CA1323397C - Lead accumulators - Google Patents
Lead accumulatorsInfo
- Publication number
- CA1323397C CA1323397C CA000575874A CA575874A CA1323397C CA 1323397 C CA1323397 C CA 1323397C CA 000575874 A CA000575874 A CA 000575874A CA 575874 A CA575874 A CA 575874A CA 1323397 C CA1323397 C CA 1323397C
- Authority
- CA
- Canada
- Prior art keywords
- electrolyte
- lead
- metal ions
- alloy
- tin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000003792 electrolyte Substances 0.000 claims abstract description 70
- 239000011575 calcium Substances 0.000 claims abstract description 30
- 229910001420 alkaline earth metal ion Inorganic materials 0.000 claims abstract description 25
- 229910052718 tin Inorganic materials 0.000 claims abstract description 21
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052787 antimony Inorganic materials 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 18
- 239000011734 sodium Substances 0.000 claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims abstract description 16
- 239000002184 metal Substances 0.000 claims abstract description 16
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910000978 Pb alloy Inorganic materials 0.000 claims abstract description 10
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 10
- 150000002739 metals Chemical class 0.000 claims abstract description 9
- 229910001413 alkali metal ion Inorganic materials 0.000 claims abstract description 8
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910001128 Sn alloy Inorganic materials 0.000 claims abstract description 6
- 239000000203 mixture Substances 0.000 claims abstract description 6
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 4
- 229910052700 potassium Inorganic materials 0.000 claims abstract description 4
- 229910052708 sodium Inorganic materials 0.000 claims abstract description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 3
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 3
- 239000011248 coating agent Substances 0.000 claims abstract description 3
- 238000000576 coating method Methods 0.000 claims abstract description 3
- 239000011591 potassium Substances 0.000 claims abstract description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 18
- 239000013543 active substance Substances 0.000 claims description 18
- 239000002585 base Substances 0.000 claims description 17
- 150000002500 ions Chemical class 0.000 claims description 12
- 229910000882 Ca alloy Inorganic materials 0.000 claims description 11
- 229910001868 water Inorganic materials 0.000 claims description 11
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 8
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 2
- LQBJWKCYZGMFEV-UHFFFAOYSA-N lead tin Chemical compound [Sn].[Pb] LQBJWKCYZGMFEV-UHFFFAOYSA-N 0.000 claims 2
- 238000002425 crystallisation Methods 0.000 claims 1
- 230000008025 crystallization Effects 0.000 claims 1
- 239000002142 lead-calcium alloy Substances 0.000 claims 1
- 229910045601 alloy Inorganic materials 0.000 abstract description 37
- 239000000956 alloy Substances 0.000 abstract description 37
- 230000002939 deleterious effect Effects 0.000 abstract 1
- 229910021645 metal ion Inorganic materials 0.000 description 21
- 229910014474 Ca-Sn Inorganic materials 0.000 description 16
- 239000002253 acid Substances 0.000 description 14
- 238000007599 discharging Methods 0.000 description 14
- 230000000694 effects Effects 0.000 description 14
- 230000001976 improved effect Effects 0.000 description 14
- 238000011084 recovery Methods 0.000 description 14
- 239000000654 additive Substances 0.000 description 12
- 238000007654 immersion Methods 0.000 description 11
- 229910020220 Pb—Sn Inorganic materials 0.000 description 10
- 238000007747 plating Methods 0.000 description 10
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 8
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 8
- 230000003247 decreasing effect Effects 0.000 description 8
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 8
- 229910006531 α-PbO2 Inorganic materials 0.000 description 8
- 239000001999 grid alloy Substances 0.000 description 7
- YADSGOSSYOOKMP-UHFFFAOYSA-N lead dioxide Inorganic materials O=[Pb]=O YADSGOSSYOOKMP-UHFFFAOYSA-N 0.000 description 7
- 235000011007 phosphoric acid Nutrition 0.000 description 7
- 229910017835 Sb—Sn Inorganic materials 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 239000011777 magnesium Substances 0.000 description 5
- 239000007832 Na2SO4 Substances 0.000 description 4
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 4
- 230000005484 gravity Effects 0.000 description 4
- 235000019341 magnesium sulphate Nutrition 0.000 description 4
- -1 phosphoric acid ions Chemical class 0.000 description 4
- 230000036647 reaction Effects 0.000 description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 description 4
- 235000011152 sodium sulphate Nutrition 0.000 description 4
- 229910020669 PbOx Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- PIJPYDMVFNTHIP-UHFFFAOYSA-L lead sulfate Chemical compound [PbH4+2].[O-]S([O-])(=O)=O PIJPYDMVFNTHIP-UHFFFAOYSA-L 0.000 description 3
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 3
- 238000011282 treatment Methods 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 229910001245 Sb alloy Inorganic materials 0.000 description 2
- 229910020935 Sn-Sb Inorganic materials 0.000 description 2
- 229910008757 Sn—Sb Inorganic materials 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 238000004080 punching Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 2
- KEQXNNJHMWSZHK-UHFFFAOYSA-L 1,3,2,4$l^{2}-dioxathiaplumbetane 2,2-dioxide Chemical compound [Pb+2].[O-]S([O-])(=O)=O KEQXNNJHMWSZHK-UHFFFAOYSA-L 0.000 description 1
- 229910001316 Ag alloy Inorganic materials 0.000 description 1
- 229910004776 CaSn3 Inorganic materials 0.000 description 1
- 206010024769 Local reaction Diseases 0.000 description 1
- 101100309487 Mus musculus Samhd1 gene Proteins 0.000 description 1
- 101100369237 Mus musculus Tgtp1 gene Proteins 0.000 description 1
- 101100369238 Mus musculus Tgtp2 gene Proteins 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 229910052924 anglesite Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 235000019795 sodium metasilicate Nutrition 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229910002058 ternary alloy Inorganic materials 0.000 description 1
- 229910006529 α-PbO Inorganic materials 0.000 description 1
- 229910006654 β-PbO2 Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/68—Selection of materials for use in lead-acid accumulators
- H01M4/685—Lead alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/06—Lead-acid accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/06—Lead-acid accumulators
- H01M10/08—Selection of materials as electrolytes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Cell Electrode Carriers And Collectors (AREA)
- Secondary Cells (AREA)
Abstract
Abstract A lead accumulator having an electrolyte and a grid substrate. The grid substrate is formed of an alloy of lead with a metal, or a mixture of metals, selected from, first antimony, which alloy further contains any one of the metals sodium, lithium, potassium or tin. Secondly calcium, and further containing tin, tin and antimony or tin and aluminum. Thirdly calcium with no antimony and a coating of tin or an alloy of lead and tin. The electrolyte in the first and second cases contains alkaline earth metal ions. In the third case, the electrolyte contains alkaline earth and alkali metal ions. The accumulator improves the performance and properties of conventional lead accumulators and is resistant to the deleterious effects of being allowed to stand in a discharged condition.
Description
13233~
LEAD ACCUMULATORS
The present invention is concerned ~ith improvements in or relating to a lead accumulator.
Upon being allo~ed to stand for an extended period or in an over-discharged sate, lead accumulators are so frequently unchargeable due to self-discharging that they are prematurely unserviceable. To solve this problem, various attempts have been made in terms of grid alloys for lead accumulators, In one effort, the Sb content of grids has been decreased to reduce self-discharging or, for the same purpose, Pb-Ca base alloys have been used as antimony-free alloys In another effort, the grids have been coated on their surfaces with a conductor ~ith a vie~ to prevent the formation of PbO~ or lead sulfate on the interface of positive grids and associated active substances, which is responsible for a lo~ering of the performance of lead accumulators upon being allowed to stand in an over-charged state.
In a further effort, an electrically conductive resin having a pellobskite base compound or hu, Ag or Pt po~ders dispersed therein has been added to the active substances in order to pernit conduction to be maintained, even though such a highly resistive vaterial is formed. In a still further effort, phosphoric acid or alkalline metal ions have been incorporated into an electrolyte for the sa~e purpose.
The grid alloys now put to practical use include Pb-Sb and Pb-Ca base alloys. However, the Sb base alloys are disadYantageous in that a hydrogen-generati~g potential of Sb is too noble to reduce self-discharging, and a water electrolysis voltage is so low that the amount of a water reduction is increased. The E~b-Ca alloys, on the other hand, have a limited or reduced service life at the time when used in deep charge/discharge cycles, and need a special load circuit for the purpose of preventing over-discharging. At a reduced content of Sb, say, 3.5% by weight or less, such alloys have a demerit similar to that of Sb-free alloys.
Thus, the problems as mentioned above cannot substantially be solved by binary grid alloy compositions such as Pb-Ca and Pb-Sb. With this in mind, ternary alloys of Pb-Sn-As and Pb-Ca-Sn have been proposed in recent years. These alloys show limited self-discharging, are comparable to the Pb-Ca alloys in terms of water electrolysis and exhibit good properties even upon being allowed to stand in an over-discharged state. In the case of the Pb-Ca-Sn alloys, however, considerable elongation of grid collectors per se is caused by intergranular corrosion at a Ca concentration of 0.09% by wei~ht or higher thereby making it impossible to hold their associated active substances. When such an alloy is used for a Positive grid, it comes into contact with a strap, on the negative electrode side, giving rise to a short-circuit or, in extreme cases, a failure of an accumulator cell. As a result, the accumulator becomes prematurely unserviceable Further, these alloys are inferior to Pb-Ag alloys in terms of corrosion resistance, so that difficulty is involved in holding active substances. Still further, an increase in the content of Sn leads to a rise in the cost Referring on the other hand to the concentration of sulfuric acid forming an electrolyte, it is considerably decreased in an overdischarged state with the result that the conductivity of the electrolyte is considerably decreased so that the accumulator becomes uncha~geable.
Thus, problems arise in connection with not oniy the grid alloys but also the conductivity of electrolytes to be maintained. In this respect, it has been proposed to add ~3PD4 into _~_ ~3233Q7 electrolytes in the prior art. However, although H3PO4 improves the chargeability of lead accumulators during over-discharging, it rather gives rise to a lowering of discharge capacity at the initial stage of service life and increased self-discharging.
With a view to solving the above problems, the present invention provides a lead accumulator having an electrolyte and a grid substrate formed of an alloy of lead with a metal or mixture of metals selected from the group, (a) antimony and further containing any one of the metals sodium, lithium, potassium or tin; (b) calcium and further containing tin, tin and antimony or tin and aluminum; and (c) calcium with no antimony and a coating of tin or an alloy of lead and tin; the electrolyte in (a) and (b) containing alkaline earth metal ions and, in (c), alkaline e~rth and alkali metal ions.
The invention is illustrated, by way of example only, in the drawings in which:
Figure 1 is a view illustrating the relationship between the concentration of Ca and the rate of grid elongation in a trickle life test of a lead accumulator of 1.2 Ah-6 V using a Pb-Ca alloy, Figure 2 is a graphical view showing the results of a cycle life test carried out with lead accumulators using grids obtained from a Pb-Na-Sb-Sn alloy according to the first aspect of the present invention and a conventional Pb-Ca-Sn alloy, Figure 3 is a comparative view illustrating the 3~ recovery performance of capacities of lead accumulators after permitted to stand in an over-discharged state, said accumulators using grids .~ ~
1~233~7 obtained from a Pb-Na-Sb-Sn alloy according to the first aspect of the present invention and a conventional Pb-Ca-Sn alloy, Figure 4 is a comparative view illustrating the recovery of capacities of lead accumulators according to the second aspect of the present invention, Figure 5 is a graphical view illustrating the chargeability of lead accumulators after permitted to stand in an over-discharged state for the purpose of comparison, Fig~re 6 is a graphical view illustrating the relationship between the days elapsed and the remaining capacities, Figure 7 illustrates the chargeability of lead accumulators after permitted to stand in an over-discharged state,which are affected by plating a~d acid immersion treatments and the addition of Nat and Mg2t, hatched regions showing lead accumulators which are not treated ~ith an acid, and Figure 8 is a view illustrating the relationship between the days elapsed and the remaining capacities.
According to the first aspect of the present invention, there is provided a lead accu~ulator ~hich uses a grid substrate for~ed of a Pb-Sb alloy containing any one of Na, Li and K and Sn, and in ~hich an electrolyte contains alkaline earth metal ions.
According to the second aspect of the present invention, there is provided a lead accumulator which uses a grid substrate conprising a lead alloy containin~ Ca and SD or Ca, Sn and Sb or Ca, Sn, Sb and AQ, and in which ao electrolyte contains alkaline earth metal ions.
According to a third aspect of the present invention, there is provided a lead accumulator in which a grid substrate is formed of a plate piece obtained by making a Pb-Ca base alloy plate integral with a Pb-Sn base alloy plate, and an electrolyte contains alkaline metal 13233~7 ions, alklaine earth metal ions or phosphoric acid ions.
According to the fourth aspect of the present inve~tion, thereis provided a lead accumulator which uses an electrode obtained by plating the surface of a Pb-Ca alloy electrode containing no Sb ~ith Sn or an Pb-Sn alloy, and in which an electrolyte contains at least one of alkaline metal ions and alkaline earth metal ions.
According to the fifth aspect of the present invention, there is provided a lead accumulator in which an electrolyte contains alkaline earth metal ions, and which includes a positive grid obtained by forming an unformed, active substance-filled grid using a grid member obtained from a Ca and Sn-containing lead alloy free from antimony and i~ersing said grid in dilute sulfuric acid.
According to the sixth aspect of the present invention, there is provided a lead accumulator in which an electrolyte contains 500 ppm or higher of alkaline Metal ions and, at the same time, ions of an alkaline earth ~etal having no ~ater and/or crystallized water.
According to the seventh aspect of the present invention, there is a provided a lead accumulator in which an electrolyte contains alkaline metal ions and/or alkaline earth metal ionst and ~hich includes a positive grid obtained by plating the surface of a collector uith a Pb-Sn alloy and forming a grid using said collector, follo~ed by its immersion in dilute sulfuric acid.
Upon being allo~ed to stand for an exteDded period ~ithout charging, lead accumulators become unchargeable, or upon being left alone after deep charging, they again become unchargeable. This is caused by a considerable increase in the internal resistance of positive grids probably due to the following factors. Upon over-discharged, the specific gravity of electrolytes decreases, and its decrease is nore considerable in the vicinity of the grids in the grid ~233~7 sbustrates than on the surfaces thereof. In this case, the solubilityof Pb in the grids increases to yield Pb2t. When Pb2t is formed, PbO2 that is an active substance in the vicinity of the positive grids becomes unstable at an increased pH level, so that a local cell reaction, as represented by the scheme:
PbO2 + Pb + 2H2SO~ -~ 2PbS04 + 2H20, occurs, thus yielding PbSO4. At the same time, PbSO~ undergoes repeated dissolution and precipitation at an increased pH level for crystal growth, so that the grid interface is coated with non-reducing PbSO~. Further, as H2SO~ is consumed by the aforesaid local cell reaction, the positive grid potential decreases to a base level of -400 to -200 mV (vs. Hg/Hg2SO~). At this potential, another local cell reactions, as expressed in terms of the scheme:
PbO2 (active substance) + H20 + 2e~ -~ PbO(PbOx) + 20H- and Pb (grid) + SO~2- - PbSO~ + 2e~, occur synergistically (Eo = - 370 mV vs. Hg/Hg2SO~PbSO~, so that a highly resistive film is formed by the growth of PbSOY and the formation of PbOx, thus making charging impossible. For that reason, there may be available a compound which makes it difficult to form such a resistive film or make conduction between Pb (grid) and PbO2 (active substance), even though it is formed. As already pointed out, Sn is effective for the properties of lead accumulators upon being allowed to stand in an over-discharged state.
According to the first aspect of the present invention, Sn is incorporated as a grid alloy element into a Pb-Na-Sb alloy. Although the effect of Sn is still unclarified, improved chargeability is probably achieved for the following reasons. In the Pb matrix, there may be formed an intermetallic compound such as CaSn3 or Pbycaysn~
which, w~en the grid is anodically oxidi~ed, is dispersed throughout the resulting oxide film to maintain conductivity. Alternatively, Sn 132339~
may be oxidized to form a compound such as SnO or SnO2 having semiconductive properties (n-type semiconductor). Sb that acts as another grid alloy element dissolves into the oxide film in the form of Sb3t or Sb203, which then destroy the highly resistive film and prevent the lead acc~mulator from becoming unchargeable. Further, Sb also serves to reduce an increase in the internal resistance, when the accumulator is allowed to stand in an over-charged state. However, since increased and decreased amounts of Sn bring about a considerable decrease in the consumption of the electrolyte and a lowering of the strength of the grid, respectively, Na is used for keeping the grid strength in an amount which allows Sb to be effective for over-discharging and the amount of the electrolyte to be not decreased.
Referring to the additives in the electrolyte, on the other hand, an oxidation reaction occurs on the positive electrode side during charging, so that electrons flow toward the negative electrode and electron charges are carried from the negative elelctrode by H~
and SO~2- in the electrolyte. After over-discharging, however, the pH
is in the vicinity of 7, so that H20 increases, while SO~2- and Ht decrease. Thus, cations of SO~2- salts should be selected as the charge carrier, since most anions such as halogen ions or NO32- react with Pb. In particular, such cations should be selected fro~ those forming sulfates, in view of the influences upon other properties of the accumulator (inclusive of service life, capacity, etc.3. Table 1 shows the ion conductivities at 25C of various sulfates and a phosphate, of which the sulfates of alkaline earth metals are preferred and advantageously used. The alkaline earth metals are more inexpensive than the alkaline metals.
13233~7 Table !
(25C ) ~ Compounds ¦ Conductivities (Q/cm) I Alkaline ¦ Na2SO~ ¦ 0.005 Na2SiO3 ~ 0.006 I Metals K25O~ I 0.006 il Alkaline CaSO~ ¦ 0.Q02 (Concentration: 0.02 M)~
Earth Metals MgSO~ I 0.004 __ _ _ _ __ CuSO~ 0.003 Other La2(SO4)3 0.001 Elements ZnSO, 0.003 I H3PO~ I O.006 According to the second aspect of the present invention, Sn is incorporated as a grid substrate alloy element into a Pb-Ca base alloy. More specifically, the grid substrate to be used comprises any one of Pb-Ca-Sn, Pb-Ca-Sn-Sb and Pb-Ca-Sn-Sb-AQ alloys which limits the consumption of an electrolyte, shows limited self-discharging and has improved properties upon being allowed to stand in an over-discharged state, and the electrolyte to be used contains alkaline earth metal ions for the purpose of maintaining its conductivity.
In this aspect, Sn and Sb act in a sinilar manner as explained in connection with the first aspect of the present invention.
If the amounts (in ~ by weight) of Ca and Sb are increased in the Pb-Ca-Sb base alloys, then Ca ~d Sb forms a dross compound in the form of Ca2Sb3 incapable of forming a solid solution. In this case, however, the presence of AQ causes Ca to be fixed into the alloy without forming any dross compound. This is why AQ is added to that alloy.
The additives for electrolytes mentioned in connection with the first aspect of the present invention are again used in the second aspect of the present invention.
According to the third aspect of the present invention, there is provided a lead acc~ lator in which an electrode substrate is formed of a plate piece obtained by making a Pb-Ca base alloy plate integral with a Pb-Sn base alloy plate, and an electrolyte contains alkaline metal ions, alklaine earth metal ions or pnophoric acid ions.
In this aspect, Sn acts in a similar manner as explained in connection with the first aspect of the present invention, and the additives used for electrolytes are identical with those used in the first aspect of the present invention.
According to the fourth aspect of the present invention, an electrode comprises a Pb-Ca alloy which contains no Sb and is plated on its surface with Sn or a Pb-Sn alloy, and an electrolyte contains at least one of alkaline metal ions and alkaline earth metal ions.
A lowering of the chargeability of a lead accumulator occurring upon being allowed to stand in an over-discharged state seems to be due to an insulating PbSO~ film bei.~ formed on the interface of a positive grid and an active substance. However, since chargeability is improved by an increase in the amount of Sn contained in the grid alloy, it is likely that Sn serves to maintain conductivity between the grid and the active substance. If the concentration of Sn on the grid interface is increased by plating with Sn or a Pb-Sn alloy, then the properties of the accuwulator upon allowed to stand in an over-discharged state can be improved. Uhen the lead accumulator is per~itted to stand in an over-discharged state, on the other hand9 the concentration of sulfuric acid in the electrolyte is so decreased that the conductivity of the electrolyte is decreased; this being one factor for a lowering of chargeability. However, the addition of alkaline metal ions or alkaline earth metal ions to the electrolyte causes an increase in the conductivity of the electrolyte, which assures improved flowing of charging currents.
13233~7 Any appreciable effect is not obtained by sole app}ication of~
Sn plating or a Pb-Sn alloy plating or alkaline (earth) metal ions, since they act separately upon individual causes for a lowering of the chargeability of lead accumulators upon allowed to stand in an over-discharged state. However, if the Sn (or a Pb-Sn alloy) plating is used in cooperation with alkaline (earth) metal ions, then extremely improved effects are obtained through synergism.
According to the fi~th aspect of the present invention, there is provided a lead accumulator in which an electrolyte contains alkaline earth metal ions, and which includes a positive grid obtained by preparing a grid substrate from a Ca and Sn-containing lead alloy free from antimony, filling an active substance in the grid substrate and forming the grid substrate, followed by its immersion in dilute sulfuric acid.
In this aspect, Sn acts in a similar manner as explained in connection with the first aspect of the present invention.
After a lead accumulator is permitted to stand in an over-discharged stage, H2S0~ in its electrolyte is converted to H70 and PbS0~. As a result, charging current-carrying ions are extremely reduced, giving rise to a considerable lowering of the conductivity of the electrolyte. Required in this case are ions giving no damage to the service life, capacity and performance of the accumulator.
Alkaline metal ions are said to be effective for this purpose.
However, alkaline earth metal ions more inexpensive than alkaline metal ions are comparable thereto in terms of electrical conductivity and effect, as set forth in Table 1. In place of the alkaline earth metal ions, the corresponding hydrates may also be used, as is the case with magnesi~ sulfate. In this connection, it is noted that the alkaline metal ion and alkaline earth metal ion, if used simultaneously, cooperate synergistically with each other to improve 13233~7 conductivity, excep~ for in a high concentration region in which the ions do not interact.
In order to prevent PbSO~ from being formed on the interface of a grid and an active substance during over-discharging, the positive grid after forning may be immersed in dilute sulfuric acid regulated to the given concentration and temperature, whereby the positive grid is maintained at a certain potential and an alpha-PbO2 film is formed on the interface of the grid and the active substance to keep conductivity therebetween. This is due to the presence of alpha-PbO2 which is more inert with respect to a discharging reaction and more intimate than beta-PbO2. In other words, alpha-PbO2 is unlikely to be converted to PbO~ through a local reaction, and suppresses inward diffusion of SO~2-. Thus, the formation of PbSO~ in the interface film is prevented. Alpha-PbO2 is stable and electrically conductive during charging, and thus functions as a conductor.
Any noticeable effect is not obtained by sole application of such three means. However, if they are applied in combination, then much more improved effects are obtained, since they act upon improvements in the properties of lead accumulators upon permitted to stant in an over-discharged state through difference mechanisms.
According to the sixth aspect of the present invention, there is provided a lead accumulator in ~hich an electrolyte contains alkaline metal ions in a concentratlon of 500 ppm or more and, at the same time, ions of an anyhydrous alkaline earth metal and/or ions of an alkaline earth metal having crystallized ~ater.
As already mentioned, lead accu~ulators frequently become unchargeable upon allo~ed ~o stand after deep discharging. This is because a non-reactive PbSO~ film is formed on the interface of a grid and an active substance, giving rise to an increase in the internal resistance of the accumulators. In particular, the internal resistance of the positive grid is increased. This is due to the fact 1323~7 that PbSO~ is formed on the interface of the grid and the active substance as a result of local cell reactions between Pb, PbO2 and H2SO~ occurring on that interface. When a lead accumulator is allowed to stand in an over-discharged state, the specific gravity of the electrolyte is so decreased that the resistance of the electrolyte is increased. This is responsible for a lowering of the properties of the accumulator after allowed to stand in an over-discharged state.
After allowed to stand in an over-discharged state, the specific gravity of the electrolyte drops and approaches nearly to that of water. ~or that reason, the resistance of the electrolyte is so increased that difficulty is involved in flowing of a charging current. In order to increase the conductivity of the electrolyte and a charging current flowing therethrough, al~aline metal ions may be added to the electrolyte.
When magnesium sulfate is added to the electrolyte, on the other hand, there is an increase in the solubility of lead sulfate.
For that reason, the passivated lead sulfate formed on the grid interface is dissolved to recover conduction between the grid and the active substance, thus facilitating flowing of a charging current.
Any noticeable effect on the recovery of chargeability is not obtained by sole application of such two means. However, if the two means are used in combination, then the chargeability of the lead accumulator after being allowed to stand in an over-discharged state can be largely improved. Alkaline metal ions are substantially ineffective in a concentration of below 500 ppm, and should thus be used in a concentration of at least 500 ppm to achieve the desired effect.
The seventh asepct of the present invention is a combination of the fourth aspect with the fifth asepct of the present invention.
The present invention will now be explained with reference to the following non-restrictive examples.
13233~7 EXAMPLES
Examples of the First Aspect Lead accumulators of 10 Ah-2 V were prepared from Pb-Na-Sb-Sn and Pb-Ca-Sn alloys, and were then subjected at 30C to a cycle test of 2A discharge (with a depth of 100 %) at a constant voltage of 2.55 V (2A restriction). The results are shown in Figure 2, from which it is found that the invented accumulator A based on Pb-Na-Sb-Sn is superior to the conventional accu~ulator B based on Pb-~a-Sn in terms of cycle properties. Prepared from the aforesaid two alloys and an electrolyte containing a predetermined amount of MgS0~ were accumulator cells of 1.2 Ah-6V, which were then discharged at 8 ohms for 24 hours, allowed to stand at 25C for one month, and subjected to constant-voltage charge at 2.45 V/cell for 24 hours. At that time, the 5H- R- capacities were compared uith each other before and after over-discharging. The ratios of capacities recovered with respect to the initial capacities are illustrated in Figure 3, from which it is noted that the Pb-Na-Sb-Sn base cell is improved over the Pb-Ca-Sn base cell in terms of recovery properties. It is also found that by the addition of MgS0~, the recovery properties of the Pb-Ca-Sn base t cell shows a 15 % increase, while the recovery properties of the Pb-Na-Sb-Sn base cell exhibits a 20 ~ increase. This means that MgS0 and the alloy con~osition interact synergistically with each other.
It is to be understood that the collector to be used may be not only in the grid form but also in the plate, expanded, blanked or rolled-plate form.
Examples of the Second Aspect Grids were prepared from a Pb-Ca alloy containing Sn and Sb or AQ, and were used with an electrolyte containing a predetermined concentration (0.1 mole/Q) of MgS0~ as an alkaline earth metal to make accumulator cells of 1.2 Ah-6V, which were then discharged at a - l3-132~97 constant resistance of 8 ohms, open-circuited after the lapse of 24 hours, allowed to stand at 25C for one month and recovered by constant-voltage charge at 2.45 V to measure the ratios of the capacities recovered with respect to the initial five-hour capacities.
For the purpose of comparison, a Pb-Ca alloy and an electrolyte containing no MgS04 were used to make comparative cells. The test results are illustrated in Figure 4, from which it is found that the Pb-Ca, Pb-Ca-Sn, Pb-Ca-Sn-Sb and Pb-Ca-Sn-Sb-A~ base cells are all poor in the recovery of their capacities, when the electrolytes used therewith contain no MgS0~. This is considered to be due to the synergism of the effects of Sn, Sb and MgS04, which restrains a high resistor from being formed at the time when the cells are allowed to stand in an over-discharged state.
Examples of the Third Aspect A 0.5 mm-thick alloy sheet of Pb containing 2.5 weight Z of Sn was laminated on and rolled with an alloy sheet of Pb containing 0.06 weight X of Ca and 0.3 weight Z of Sn. Prepared from the thus obtained laminate was an electrode substrate of 3 ~m in thickness by punching, which was then filled with a paste, aged and dried to obtain a positive grid. A lead accumulator was assembled ~y forming to make an accumulator cell of 4 V-4 Ah. The thus obtained cells were then filled with electrolytes containing a regulated concentration (0.1 mole/~) of Na~S0~, MgS0~ and H3P0~. The thus prepared lead accumulator cells ~ere discharged at 1.7 ohms for 24 hours, allowed to stand at 25C for 6 months, and were thereafter charged at a constant v~ltage of 2.45 V/cell (1.2A cut) for 24 hours to measure the rocovery of their capacities with resepct to their initial capacities. The results are set forth in Table 2.
1~23397 Table 2 Cell ¦ Compositions and T---- ---------------- Recovery of Capacities Nos.l Configurations of ¦ Additives Grides I (%) 0~6~ A~ V ~ ble _l ___ ~ I MgSO~ I 86.2 4 1 " I H1PO4 ! 85.7 1 Prior t - - ¦ Na2SO4 1 91.8 ¦ MgSO~ 1 1 Art ._ _~ I 89 6 __ _ H3PO4 _ L
7 ~ MgSO4 1 88.5 I ~ , __ 8 1 Pb-0.06Ca-0.3Sn I !
Pb-3Sn~Punched INo Additivel 17.6 I Rolled Sheet) I l 9 t ~~ I Na2SO~ I 93.8 , o t ~ I MgSO4 ¦ 93.3 l l 11 1 " ¦ H3PO4 1 91.7 12 1 " ~, Na7SO~ r 1 0O Invention I
l __ I __ _ I l I
13 ~ Na25O~ 1 98.8 MgS ~ 1 99.3 I____ ~,___ i From a comparison of Cell No. 1 to No. 7 ~ith Cell No. 8 to No.
14, it is found that the grids obtained from the rolled laminates are improved over those from castings in terms of recovery propoerties.
This seems to be due to the fact that the content of Sn on the surfaces of the electrode substrates made by rolling is 1.5 % or more than that made by castings. Of Cell Nos. 8 to 14, Cell Nos. 9, 10 and 11 are more i~proved in terms of charge recovery because of the presence of alkaline metal ions7 alkaline earth metal ions and phosphoric acid ions. From this, it is found that Sn in the electrode - l5-13233~7 substrates becomes more effective in the presence of the aforesaid additives. Much more increased effects are obtained with Cell No~.
12, 13 and 14 containing all the possible combinations of these additives than with Cell Nos. 9, 10 and 11. From the foregoing, it is preferred in view of improvements in the properties of the accumulator cells at the time when they are permitted to stand in an over-discharged state that the rolled laminates of Pb-Ca-Sn and Pb-Sn having an increased Sn content on their surfaces be used as electrode substrates in combination with electrolytes containing alkaline metal ions, alkaline earth metal ions and phosphoric acid ions, which interact synergistically with Sn.
Examples of the Fourth Aspect Grids of an Sb-free Pb-Ca alloy plated on its surface with Sn was used as positive grids to prepare accumulators of 1.2 Ah-2 V, which were then filled with an electrolyte containing Na1 and Mg21 and an electrolyte to which no Na~ and Mg2t were added. The thus obtained accumulator cells were discharged at a constant resistance for 24 hours, open-circuited, and were thereafter permitted to stand for one month. For the purpose of comparison, accumulator cells were prepared with grids which were not plated with Sn, and ~ere tested under similar conditions as mentioned above. These accumulator cells were then charged at a constant voltage of 2.45 V to measure the charging currents after 10 seconds, 30 seconds and 60 seconds elapsed. The results are illustrated in Figure 5. The charging curren$s measured are expressed by the ratio with respect to a charging current flowing in the reference accumulator cell comprising a grid which was not plated on its surface with Sn and containing an electrolyte to which Nat was added.
In Figure 5, reference nu~erals 1, ~ ~nd 3 stand for accumulator cells co~prising grids which were not plated on their - l6-surfaces with Sn. The cell No. 1 contained an electrolyte to which nothing was added, No. 2 an electrolyte to which Na''' was added, and No. 3 an electrolyte to which Mg2t was added. Reference numerals 4, 5 and 6 stand for accumulator cells having grids plated with Sn on their surfaces. The cell No. 4 contained an electrolyte to which nothing was added, No. 5 an electrolyte to which Na~ was added, and No. 6 an electrolyte to which Mg2t was added.
When comparing with the accumulator cells containing an electrolyte to which Nat or Mg2~ alone was added or having a grid plated with Sn, the accumulator cells having grids plated with Sn and containing an electrolyte to which both Na~ and Mg2t were added are found to carry an about two-fold charging current. This indicates that Sn plating interacts synergistically with Natand Mg2t added to an electrolyte. t In the instant examples, cast grids were used. However, similar effects will be obtained with grids obtained from rolled sheets by punching or expanded grids.
Examp es of_the Fifth Aspect Prepared from an Pb-Ca alloy containing Sn were grids, which were filled with an active substance and formed to make positive grids having or having not an alpha-PbO2 film thereon. Prepared with these grids were accumulator cells of 1.2 Ah-6 V, which were then filled with electrolytes containing Na2SO~, MgS04, MgSO~-7H20, Na2SO~ +
MgSO~ and Na2SO~ + MgSO~-7H20. In order to prepare a reference accumulator cell common to 211 the cells as mentioned above, a Pb-Ca alloy having no alpha-PbO~ thereon was used with a sulfuric acid electrolyte to which nothing was added. These cells were discharged at a constant resistance of 8 ohms for 24 hours, and were thereafter open-circuited and permitted to stand at 25C for 1 month. The cells were then charged at a constant voltage of 7.35 ~ (0.3 C restriction) 1323~97 for 24 hours with a stabilized power source.
Table 3 shows the results in terms of the ratios of the 5 H.R.
capacities recovered with respect to the initial 5 H.R. capacities.
13233~7 Table 3 ~Cell I Grid Additives 1 a-PbO2 I Recovery ¦ Nos. __ IFilm (%) 1 Pb-Ca No ,Not¦ Unchargeable 1 Additive IForm ¦ I
__ _____ ~
LEAD ACCUMULATORS
The present invention is concerned ~ith improvements in or relating to a lead accumulator.
Upon being allo~ed to stand for an extended period or in an over-discharged sate, lead accumulators are so frequently unchargeable due to self-discharging that they are prematurely unserviceable. To solve this problem, various attempts have been made in terms of grid alloys for lead accumulators, In one effort, the Sb content of grids has been decreased to reduce self-discharging or, for the same purpose, Pb-Ca base alloys have been used as antimony-free alloys In another effort, the grids have been coated on their surfaces with a conductor ~ith a vie~ to prevent the formation of PbO~ or lead sulfate on the interface of positive grids and associated active substances, which is responsible for a lo~ering of the performance of lead accumulators upon being allowed to stand in an over-charged state.
In a further effort, an electrically conductive resin having a pellobskite base compound or hu, Ag or Pt po~ders dispersed therein has been added to the active substances in order to pernit conduction to be maintained, even though such a highly resistive vaterial is formed. In a still further effort, phosphoric acid or alkalline metal ions have been incorporated into an electrolyte for the sa~e purpose.
The grid alloys now put to practical use include Pb-Sb and Pb-Ca base alloys. However, the Sb base alloys are disadYantageous in that a hydrogen-generati~g potential of Sb is too noble to reduce self-discharging, and a water electrolysis voltage is so low that the amount of a water reduction is increased. The E~b-Ca alloys, on the other hand, have a limited or reduced service life at the time when used in deep charge/discharge cycles, and need a special load circuit for the purpose of preventing over-discharging. At a reduced content of Sb, say, 3.5% by weight or less, such alloys have a demerit similar to that of Sb-free alloys.
Thus, the problems as mentioned above cannot substantially be solved by binary grid alloy compositions such as Pb-Ca and Pb-Sb. With this in mind, ternary alloys of Pb-Sn-As and Pb-Ca-Sn have been proposed in recent years. These alloys show limited self-discharging, are comparable to the Pb-Ca alloys in terms of water electrolysis and exhibit good properties even upon being allowed to stand in an over-discharged state. In the case of the Pb-Ca-Sn alloys, however, considerable elongation of grid collectors per se is caused by intergranular corrosion at a Ca concentration of 0.09% by wei~ht or higher thereby making it impossible to hold their associated active substances. When such an alloy is used for a Positive grid, it comes into contact with a strap, on the negative electrode side, giving rise to a short-circuit or, in extreme cases, a failure of an accumulator cell. As a result, the accumulator becomes prematurely unserviceable Further, these alloys are inferior to Pb-Ag alloys in terms of corrosion resistance, so that difficulty is involved in holding active substances. Still further, an increase in the content of Sn leads to a rise in the cost Referring on the other hand to the concentration of sulfuric acid forming an electrolyte, it is considerably decreased in an overdischarged state with the result that the conductivity of the electrolyte is considerably decreased so that the accumulator becomes uncha~geable.
Thus, problems arise in connection with not oniy the grid alloys but also the conductivity of electrolytes to be maintained. In this respect, it has been proposed to add ~3PD4 into _~_ ~3233Q7 electrolytes in the prior art. However, although H3PO4 improves the chargeability of lead accumulators during over-discharging, it rather gives rise to a lowering of discharge capacity at the initial stage of service life and increased self-discharging.
With a view to solving the above problems, the present invention provides a lead accumulator having an electrolyte and a grid substrate formed of an alloy of lead with a metal or mixture of metals selected from the group, (a) antimony and further containing any one of the metals sodium, lithium, potassium or tin; (b) calcium and further containing tin, tin and antimony or tin and aluminum; and (c) calcium with no antimony and a coating of tin or an alloy of lead and tin; the electrolyte in (a) and (b) containing alkaline earth metal ions and, in (c), alkaline e~rth and alkali metal ions.
The invention is illustrated, by way of example only, in the drawings in which:
Figure 1 is a view illustrating the relationship between the concentration of Ca and the rate of grid elongation in a trickle life test of a lead accumulator of 1.2 Ah-6 V using a Pb-Ca alloy, Figure 2 is a graphical view showing the results of a cycle life test carried out with lead accumulators using grids obtained from a Pb-Na-Sb-Sn alloy according to the first aspect of the present invention and a conventional Pb-Ca-Sn alloy, Figure 3 is a comparative view illustrating the 3~ recovery performance of capacities of lead accumulators after permitted to stand in an over-discharged state, said accumulators using grids .~ ~
1~233~7 obtained from a Pb-Na-Sb-Sn alloy according to the first aspect of the present invention and a conventional Pb-Ca-Sn alloy, Figure 4 is a comparative view illustrating the recovery of capacities of lead accumulators according to the second aspect of the present invention, Figure 5 is a graphical view illustrating the chargeability of lead accumulators after permitted to stand in an over-discharged state for the purpose of comparison, Fig~re 6 is a graphical view illustrating the relationship between the days elapsed and the remaining capacities, Figure 7 illustrates the chargeability of lead accumulators after permitted to stand in an over-discharged state,which are affected by plating a~d acid immersion treatments and the addition of Nat and Mg2t, hatched regions showing lead accumulators which are not treated ~ith an acid, and Figure 8 is a view illustrating the relationship between the days elapsed and the remaining capacities.
According to the first aspect of the present invention, there is provided a lead accu~ulator ~hich uses a grid substrate for~ed of a Pb-Sb alloy containing any one of Na, Li and K and Sn, and in ~hich an electrolyte contains alkaline earth metal ions.
According to the second aspect of the present invention, there is provided a lead accumulator which uses a grid substrate conprising a lead alloy containin~ Ca and SD or Ca, Sn and Sb or Ca, Sn, Sb and AQ, and in which ao electrolyte contains alkaline earth metal ions.
According to a third aspect of the present invention, there is provided a lead accumulator in which a grid substrate is formed of a plate piece obtained by making a Pb-Ca base alloy plate integral with a Pb-Sn base alloy plate, and an electrolyte contains alkaline metal 13233~7 ions, alklaine earth metal ions or phosphoric acid ions.
According to the fourth aspect of the present inve~tion, thereis provided a lead accumulator which uses an electrode obtained by plating the surface of a Pb-Ca alloy electrode containing no Sb ~ith Sn or an Pb-Sn alloy, and in which an electrolyte contains at least one of alkaline metal ions and alkaline earth metal ions.
According to the fifth aspect of the present invention, there is provided a lead accumulator in which an electrolyte contains alkaline earth metal ions, and which includes a positive grid obtained by forming an unformed, active substance-filled grid using a grid member obtained from a Ca and Sn-containing lead alloy free from antimony and i~ersing said grid in dilute sulfuric acid.
According to the sixth aspect of the present invention, there is provided a lead accumulator in which an electrolyte contains 500 ppm or higher of alkaline Metal ions and, at the same time, ions of an alkaline earth ~etal having no ~ater and/or crystallized water.
According to the seventh aspect of the present invention, there is a provided a lead accumulator in which an electrolyte contains alkaline metal ions and/or alkaline earth metal ionst and ~hich includes a positive grid obtained by plating the surface of a collector uith a Pb-Sn alloy and forming a grid using said collector, follo~ed by its immersion in dilute sulfuric acid.
Upon being allo~ed to stand for an exteDded period ~ithout charging, lead accumulators become unchargeable, or upon being left alone after deep charging, they again become unchargeable. This is caused by a considerable increase in the internal resistance of positive grids probably due to the following factors. Upon over-discharged, the specific gravity of electrolytes decreases, and its decrease is nore considerable in the vicinity of the grids in the grid ~233~7 sbustrates than on the surfaces thereof. In this case, the solubilityof Pb in the grids increases to yield Pb2t. When Pb2t is formed, PbO2 that is an active substance in the vicinity of the positive grids becomes unstable at an increased pH level, so that a local cell reaction, as represented by the scheme:
PbO2 + Pb + 2H2SO~ -~ 2PbS04 + 2H20, occurs, thus yielding PbSO4. At the same time, PbSO~ undergoes repeated dissolution and precipitation at an increased pH level for crystal growth, so that the grid interface is coated with non-reducing PbSO~. Further, as H2SO~ is consumed by the aforesaid local cell reaction, the positive grid potential decreases to a base level of -400 to -200 mV (vs. Hg/Hg2SO~). At this potential, another local cell reactions, as expressed in terms of the scheme:
PbO2 (active substance) + H20 + 2e~ -~ PbO(PbOx) + 20H- and Pb (grid) + SO~2- - PbSO~ + 2e~, occur synergistically (Eo = - 370 mV vs. Hg/Hg2SO~PbSO~, so that a highly resistive film is formed by the growth of PbSOY and the formation of PbOx, thus making charging impossible. For that reason, there may be available a compound which makes it difficult to form such a resistive film or make conduction between Pb (grid) and PbO2 (active substance), even though it is formed. As already pointed out, Sn is effective for the properties of lead accumulators upon being allowed to stand in an over-discharged state.
According to the first aspect of the present invention, Sn is incorporated as a grid alloy element into a Pb-Na-Sb alloy. Although the effect of Sn is still unclarified, improved chargeability is probably achieved for the following reasons. In the Pb matrix, there may be formed an intermetallic compound such as CaSn3 or Pbycaysn~
which, w~en the grid is anodically oxidi~ed, is dispersed throughout the resulting oxide film to maintain conductivity. Alternatively, Sn 132339~
may be oxidized to form a compound such as SnO or SnO2 having semiconductive properties (n-type semiconductor). Sb that acts as another grid alloy element dissolves into the oxide film in the form of Sb3t or Sb203, which then destroy the highly resistive film and prevent the lead acc~mulator from becoming unchargeable. Further, Sb also serves to reduce an increase in the internal resistance, when the accumulator is allowed to stand in an over-charged state. However, since increased and decreased amounts of Sn bring about a considerable decrease in the consumption of the electrolyte and a lowering of the strength of the grid, respectively, Na is used for keeping the grid strength in an amount which allows Sb to be effective for over-discharging and the amount of the electrolyte to be not decreased.
Referring to the additives in the electrolyte, on the other hand, an oxidation reaction occurs on the positive electrode side during charging, so that electrons flow toward the negative electrode and electron charges are carried from the negative elelctrode by H~
and SO~2- in the electrolyte. After over-discharging, however, the pH
is in the vicinity of 7, so that H20 increases, while SO~2- and Ht decrease. Thus, cations of SO~2- salts should be selected as the charge carrier, since most anions such as halogen ions or NO32- react with Pb. In particular, such cations should be selected fro~ those forming sulfates, in view of the influences upon other properties of the accumulator (inclusive of service life, capacity, etc.3. Table 1 shows the ion conductivities at 25C of various sulfates and a phosphate, of which the sulfates of alkaline earth metals are preferred and advantageously used. The alkaline earth metals are more inexpensive than the alkaline metals.
13233~7 Table !
(25C ) ~ Compounds ¦ Conductivities (Q/cm) I Alkaline ¦ Na2SO~ ¦ 0.005 Na2SiO3 ~ 0.006 I Metals K25O~ I 0.006 il Alkaline CaSO~ ¦ 0.Q02 (Concentration: 0.02 M)~
Earth Metals MgSO~ I 0.004 __ _ _ _ __ CuSO~ 0.003 Other La2(SO4)3 0.001 Elements ZnSO, 0.003 I H3PO~ I O.006 According to the second aspect of the present invention, Sn is incorporated as a grid substrate alloy element into a Pb-Ca base alloy. More specifically, the grid substrate to be used comprises any one of Pb-Ca-Sn, Pb-Ca-Sn-Sb and Pb-Ca-Sn-Sb-AQ alloys which limits the consumption of an electrolyte, shows limited self-discharging and has improved properties upon being allowed to stand in an over-discharged state, and the electrolyte to be used contains alkaline earth metal ions for the purpose of maintaining its conductivity.
In this aspect, Sn and Sb act in a sinilar manner as explained in connection with the first aspect of the present invention.
If the amounts (in ~ by weight) of Ca and Sb are increased in the Pb-Ca-Sb base alloys, then Ca ~d Sb forms a dross compound in the form of Ca2Sb3 incapable of forming a solid solution. In this case, however, the presence of AQ causes Ca to be fixed into the alloy without forming any dross compound. This is why AQ is added to that alloy.
The additives for electrolytes mentioned in connection with the first aspect of the present invention are again used in the second aspect of the present invention.
According to the third aspect of the present invention, there is provided a lead acc~ lator in which an electrode substrate is formed of a plate piece obtained by making a Pb-Ca base alloy plate integral with a Pb-Sn base alloy plate, and an electrolyte contains alkaline metal ions, alklaine earth metal ions or pnophoric acid ions.
In this aspect, Sn acts in a similar manner as explained in connection with the first aspect of the present invention, and the additives used for electrolytes are identical with those used in the first aspect of the present invention.
According to the fourth aspect of the present invention, an electrode comprises a Pb-Ca alloy which contains no Sb and is plated on its surface with Sn or a Pb-Sn alloy, and an electrolyte contains at least one of alkaline metal ions and alkaline earth metal ions.
A lowering of the chargeability of a lead accumulator occurring upon being allowed to stand in an over-discharged state seems to be due to an insulating PbSO~ film bei.~ formed on the interface of a positive grid and an active substance. However, since chargeability is improved by an increase in the amount of Sn contained in the grid alloy, it is likely that Sn serves to maintain conductivity between the grid and the active substance. If the concentration of Sn on the grid interface is increased by plating with Sn or a Pb-Sn alloy, then the properties of the accuwulator upon allowed to stand in an over-discharged state can be improved. Uhen the lead accumulator is per~itted to stand in an over-discharged state, on the other hand9 the concentration of sulfuric acid in the electrolyte is so decreased that the conductivity of the electrolyte is decreased; this being one factor for a lowering of chargeability. However, the addition of alkaline metal ions or alkaline earth metal ions to the electrolyte causes an increase in the conductivity of the electrolyte, which assures improved flowing of charging currents.
13233~7 Any appreciable effect is not obtained by sole app}ication of~
Sn plating or a Pb-Sn alloy plating or alkaline (earth) metal ions, since they act separately upon individual causes for a lowering of the chargeability of lead accumulators upon allowed to stand in an over-discharged state. However, if the Sn (or a Pb-Sn alloy) plating is used in cooperation with alkaline (earth) metal ions, then extremely improved effects are obtained through synergism.
According to the fi~th aspect of the present invention, there is provided a lead accumulator in which an electrolyte contains alkaline earth metal ions, and which includes a positive grid obtained by preparing a grid substrate from a Ca and Sn-containing lead alloy free from antimony, filling an active substance in the grid substrate and forming the grid substrate, followed by its immersion in dilute sulfuric acid.
In this aspect, Sn acts in a similar manner as explained in connection with the first aspect of the present invention.
After a lead accumulator is permitted to stand in an over-discharged stage, H2S0~ in its electrolyte is converted to H70 and PbS0~. As a result, charging current-carrying ions are extremely reduced, giving rise to a considerable lowering of the conductivity of the electrolyte. Required in this case are ions giving no damage to the service life, capacity and performance of the accumulator.
Alkaline metal ions are said to be effective for this purpose.
However, alkaline earth metal ions more inexpensive than alkaline metal ions are comparable thereto in terms of electrical conductivity and effect, as set forth in Table 1. In place of the alkaline earth metal ions, the corresponding hydrates may also be used, as is the case with magnesi~ sulfate. In this connection, it is noted that the alkaline metal ion and alkaline earth metal ion, if used simultaneously, cooperate synergistically with each other to improve 13233~7 conductivity, excep~ for in a high concentration region in which the ions do not interact.
In order to prevent PbSO~ from being formed on the interface of a grid and an active substance during over-discharging, the positive grid after forning may be immersed in dilute sulfuric acid regulated to the given concentration and temperature, whereby the positive grid is maintained at a certain potential and an alpha-PbO2 film is formed on the interface of the grid and the active substance to keep conductivity therebetween. This is due to the presence of alpha-PbO2 which is more inert with respect to a discharging reaction and more intimate than beta-PbO2. In other words, alpha-PbO2 is unlikely to be converted to PbO~ through a local reaction, and suppresses inward diffusion of SO~2-. Thus, the formation of PbSO~ in the interface film is prevented. Alpha-PbO2 is stable and electrically conductive during charging, and thus functions as a conductor.
Any noticeable effect is not obtained by sole application of such three means. However, if they are applied in combination, then much more improved effects are obtained, since they act upon improvements in the properties of lead accumulators upon permitted to stant in an over-discharged state through difference mechanisms.
According to the sixth aspect of the present invention, there is provided a lead accumulator in ~hich an electrolyte contains alkaline metal ions in a concentratlon of 500 ppm or more and, at the same time, ions of an anyhydrous alkaline earth metal and/or ions of an alkaline earth metal having crystallized ~ater.
As already mentioned, lead accu~ulators frequently become unchargeable upon allo~ed ~o stand after deep discharging. This is because a non-reactive PbSO~ film is formed on the interface of a grid and an active substance, giving rise to an increase in the internal resistance of the accumulators. In particular, the internal resistance of the positive grid is increased. This is due to the fact 1323~7 that PbSO~ is formed on the interface of the grid and the active substance as a result of local cell reactions between Pb, PbO2 and H2SO~ occurring on that interface. When a lead accumulator is allowed to stand in an over-discharged state, the specific gravity of the electrolyte is so decreased that the resistance of the electrolyte is increased. This is responsible for a lowering of the properties of the accumulator after allowed to stand in an over-discharged state.
After allowed to stand in an over-discharged state, the specific gravity of the electrolyte drops and approaches nearly to that of water. ~or that reason, the resistance of the electrolyte is so increased that difficulty is involved in flowing of a charging current. In order to increase the conductivity of the electrolyte and a charging current flowing therethrough, al~aline metal ions may be added to the electrolyte.
When magnesium sulfate is added to the electrolyte, on the other hand, there is an increase in the solubility of lead sulfate.
For that reason, the passivated lead sulfate formed on the grid interface is dissolved to recover conduction between the grid and the active substance, thus facilitating flowing of a charging current.
Any noticeable effect on the recovery of chargeability is not obtained by sole application of such two means. However, if the two means are used in combination, then the chargeability of the lead accumulator after being allowed to stand in an over-discharged state can be largely improved. Alkaline metal ions are substantially ineffective in a concentration of below 500 ppm, and should thus be used in a concentration of at least 500 ppm to achieve the desired effect.
The seventh asepct of the present invention is a combination of the fourth aspect with the fifth asepct of the present invention.
The present invention will now be explained with reference to the following non-restrictive examples.
13233~7 EXAMPLES
Examples of the First Aspect Lead accumulators of 10 Ah-2 V were prepared from Pb-Na-Sb-Sn and Pb-Ca-Sn alloys, and were then subjected at 30C to a cycle test of 2A discharge (with a depth of 100 %) at a constant voltage of 2.55 V (2A restriction). The results are shown in Figure 2, from which it is found that the invented accumulator A based on Pb-Na-Sb-Sn is superior to the conventional accu~ulator B based on Pb-~a-Sn in terms of cycle properties. Prepared from the aforesaid two alloys and an electrolyte containing a predetermined amount of MgS0~ were accumulator cells of 1.2 Ah-6V, which were then discharged at 8 ohms for 24 hours, allowed to stand at 25C for one month, and subjected to constant-voltage charge at 2.45 V/cell for 24 hours. At that time, the 5H- R- capacities were compared uith each other before and after over-discharging. The ratios of capacities recovered with respect to the initial capacities are illustrated in Figure 3, from which it is noted that the Pb-Na-Sb-Sn base cell is improved over the Pb-Ca-Sn base cell in terms of recovery properties. It is also found that by the addition of MgS0~, the recovery properties of the Pb-Ca-Sn base t cell shows a 15 % increase, while the recovery properties of the Pb-Na-Sb-Sn base cell exhibits a 20 ~ increase. This means that MgS0 and the alloy con~osition interact synergistically with each other.
It is to be understood that the collector to be used may be not only in the grid form but also in the plate, expanded, blanked or rolled-plate form.
Examples of the Second Aspect Grids were prepared from a Pb-Ca alloy containing Sn and Sb or AQ, and were used with an electrolyte containing a predetermined concentration (0.1 mole/Q) of MgS0~ as an alkaline earth metal to make accumulator cells of 1.2 Ah-6V, which were then discharged at a - l3-132~97 constant resistance of 8 ohms, open-circuited after the lapse of 24 hours, allowed to stand at 25C for one month and recovered by constant-voltage charge at 2.45 V to measure the ratios of the capacities recovered with respect to the initial five-hour capacities.
For the purpose of comparison, a Pb-Ca alloy and an electrolyte containing no MgS04 were used to make comparative cells. The test results are illustrated in Figure 4, from which it is found that the Pb-Ca, Pb-Ca-Sn, Pb-Ca-Sn-Sb and Pb-Ca-Sn-Sb-A~ base cells are all poor in the recovery of their capacities, when the electrolytes used therewith contain no MgS0~. This is considered to be due to the synergism of the effects of Sn, Sb and MgS04, which restrains a high resistor from being formed at the time when the cells are allowed to stand in an over-discharged state.
Examples of the Third Aspect A 0.5 mm-thick alloy sheet of Pb containing 2.5 weight Z of Sn was laminated on and rolled with an alloy sheet of Pb containing 0.06 weight X of Ca and 0.3 weight Z of Sn. Prepared from the thus obtained laminate was an electrode substrate of 3 ~m in thickness by punching, which was then filled with a paste, aged and dried to obtain a positive grid. A lead accumulator was assembled ~y forming to make an accumulator cell of 4 V-4 Ah. The thus obtained cells were then filled with electrolytes containing a regulated concentration (0.1 mole/~) of Na~S0~, MgS0~ and H3P0~. The thus prepared lead accumulator cells ~ere discharged at 1.7 ohms for 24 hours, allowed to stand at 25C for 6 months, and were thereafter charged at a constant v~ltage of 2.45 V/cell (1.2A cut) for 24 hours to measure the rocovery of their capacities with resepct to their initial capacities. The results are set forth in Table 2.
1~23397 Table 2 Cell ¦ Compositions and T---- ---------------- Recovery of Capacities Nos.l Configurations of ¦ Additives Grides I (%) 0~6~ A~ V ~ ble _l ___ ~ I MgSO~ I 86.2 4 1 " I H1PO4 ! 85.7 1 Prior t - - ¦ Na2SO4 1 91.8 ¦ MgSO~ 1 1 Art ._ _~ I 89 6 __ _ H3PO4 _ L
7 ~ MgSO4 1 88.5 I ~ , __ 8 1 Pb-0.06Ca-0.3Sn I !
Pb-3Sn~Punched INo Additivel 17.6 I Rolled Sheet) I l 9 t ~~ I Na2SO~ I 93.8 , o t ~ I MgSO4 ¦ 93.3 l l 11 1 " ¦ H3PO4 1 91.7 12 1 " ~, Na7SO~ r 1 0O Invention I
l __ I __ _ I l I
13 ~ Na25O~ 1 98.8 MgS ~ 1 99.3 I____ ~,___ i From a comparison of Cell No. 1 to No. 7 ~ith Cell No. 8 to No.
14, it is found that the grids obtained from the rolled laminates are improved over those from castings in terms of recovery propoerties.
This seems to be due to the fact that the content of Sn on the surfaces of the electrode substrates made by rolling is 1.5 % or more than that made by castings. Of Cell Nos. 8 to 14, Cell Nos. 9, 10 and 11 are more i~proved in terms of charge recovery because of the presence of alkaline metal ions7 alkaline earth metal ions and phosphoric acid ions. From this, it is found that Sn in the electrode - l5-13233~7 substrates becomes more effective in the presence of the aforesaid additives. Much more increased effects are obtained with Cell No~.
12, 13 and 14 containing all the possible combinations of these additives than with Cell Nos. 9, 10 and 11. From the foregoing, it is preferred in view of improvements in the properties of the accumulator cells at the time when they are permitted to stand in an over-discharged state that the rolled laminates of Pb-Ca-Sn and Pb-Sn having an increased Sn content on their surfaces be used as electrode substrates in combination with electrolytes containing alkaline metal ions, alkaline earth metal ions and phosphoric acid ions, which interact synergistically with Sn.
Examples of the Fourth Aspect Grids of an Sb-free Pb-Ca alloy plated on its surface with Sn was used as positive grids to prepare accumulators of 1.2 Ah-2 V, which were then filled with an electrolyte containing Na1 and Mg21 and an electrolyte to which no Na~ and Mg2t were added. The thus obtained accumulator cells were discharged at a constant resistance for 24 hours, open-circuited, and were thereafter permitted to stand for one month. For the purpose of comparison, accumulator cells were prepared with grids which were not plated with Sn, and ~ere tested under similar conditions as mentioned above. These accumulator cells were then charged at a constant voltage of 2.45 V to measure the charging currents after 10 seconds, 30 seconds and 60 seconds elapsed. The results are illustrated in Figure 5. The charging curren$s measured are expressed by the ratio with respect to a charging current flowing in the reference accumulator cell comprising a grid which was not plated on its surface with Sn and containing an electrolyte to which Nat was added.
In Figure 5, reference nu~erals 1, ~ ~nd 3 stand for accumulator cells co~prising grids which were not plated on their - l6-surfaces with Sn. The cell No. 1 contained an electrolyte to which nothing was added, No. 2 an electrolyte to which Na''' was added, and No. 3 an electrolyte to which Mg2t was added. Reference numerals 4, 5 and 6 stand for accumulator cells having grids plated with Sn on their surfaces. The cell No. 4 contained an electrolyte to which nothing was added, No. 5 an electrolyte to which Na~ was added, and No. 6 an electrolyte to which Mg2t was added.
When comparing with the accumulator cells containing an electrolyte to which Nat or Mg2~ alone was added or having a grid plated with Sn, the accumulator cells having grids plated with Sn and containing an electrolyte to which both Na~ and Mg2t were added are found to carry an about two-fold charging current. This indicates that Sn plating interacts synergistically with Natand Mg2t added to an electrolyte. t In the instant examples, cast grids were used. However, similar effects will be obtained with grids obtained from rolled sheets by punching or expanded grids.
Examp es of_the Fifth Aspect Prepared from an Pb-Ca alloy containing Sn were grids, which were filled with an active substance and formed to make positive grids having or having not an alpha-PbO2 film thereon. Prepared with these grids were accumulator cells of 1.2 Ah-6 V, which were then filled with electrolytes containing Na2SO~, MgS04, MgSO~-7H20, Na2SO~ +
MgSO~ and Na2SO~ + MgSO~-7H20. In order to prepare a reference accumulator cell common to 211 the cells as mentioned above, a Pb-Ca alloy having no alpha-PbO~ thereon was used with a sulfuric acid electrolyte to which nothing was added. These cells were discharged at a constant resistance of 8 ohms for 24 hours, and were thereafter open-circuited and permitted to stand at 25C for 1 month. The cells were then charged at a constant voltage of 7.35 ~ (0.3 C restriction) 1323~97 for 24 hours with a stabilized power source.
Table 3 shows the results in terms of the ratios of the 5 H.R.
capacities recovered with respect to the initial 5 H.R. capacities.
13233~7 Table 3 ~Cell I Grid Additives 1 a-PbO2 I Recovery ¦ Nos. __ IFilm (%) 1 Pb-Ca No ,Not¦ Unchargeable 1 Additive IForm ¦ I
__ _____ ~
2 ¦ Pb-Ca ¦ Na~SO~ INot 1 15.7 Form 3 I Pb-Ca ¦ MgS04 ~Not 1 16.4 Form _ 4 I Pb-Ca Ij MgSO4 7H20 I Not 16.9 IForm 5 ¦ Pb-Ca I Na2SO~ ¦Not 21.3 MgS0" 7H20 ¦ Form 6 ¦ Pb-Ca Na2SO~ ¦ Form 49.4 i I MgS0~-7H20 ¦ l l I
7 ~ Pb-Ca I No Form 25.8 ¦ I Additive ¦ Prior 8 Pb-Ca ! Na2SO, Form 1 42.1 L 9 i Pb-Cat MgSo~ 7H20Form 1 41.9 Art 1 10 I Pb-Ca ¦ Na2SO4. Form 48.6 MgS0~
Pb-Ca MgS0~ jForm 1 43.5 ¦ Pb-Ca-Sn ¦ No t Not ¦ 51.3 Additive ¦Form --13 1 Pb-Ca-Sn ij Na2SO4 Not 67.2 _~ I Form 14 I Pb-Ca-Snt MgSO~ 7H20 Not 68.4 Form ___ ~
15 Pb-Ca-Sn ! Na2SO,. i Not ¦ 73.4 ¦ MgSO,. 7H20 ,! Form 1~b~a-Sn ~I Na2SO4 ¦Form ¦ 93.0 I ! ~ , . I
17 I Pb-Ca-Sn I No Form 1 76.5 ! Additive Inven-18 I Ph-Ca-Sn MgS0~ 7H20 ¦ For~ ! 93-4 ¦ tion19 ¦ Pb~a-Sn ¦ Na2SO~ IForm t 99.5 I__ I __ I I i 20 I Pb-Ca-Sn I MgSO~ 7H~0 I Form L 93.1 ~ 1 1 _ _ __ _I
1~233~7 From the table, it is found that the addition of Sn gives rise to a reovery of about 50 Z (No. 12), the incorporation of alkaline earth metal ions a recovery of about 16 % (Nos. 3, 4), the formation of an alpha-PbO2 film a recovery of 25 Z (No. 7) and the addition of both alkaline metal and earth metal ions a recovery of 5 X (No. 5).
Some synergism is obtained through a combination of two of these means. However, more improved effects are obtained by a combination of three means, i.e., Sn, alkaline earth metal ions and an alpha-PbO2 film. Cell Nos. 18 and 20 according to the present invention proved to be more effective than Cell Nos. 13 and 16 according to the prior art. MNch more improved effects are obtained in the presence of both alkaline metal and earth metal ions (No. 19), which are found to be very effective for the properties of the cell at the time when it is permitted to stand. T~is seems to be due to the fact that, as expected, Sn serves to suppress the formation of PbOx, alpha-PbO2 the formation of PbSO~, and Na~ , Mg2r and Mg(H2O)621 a lowering of conductivity.
An accumulator cell immersed in an acid to form an alpha-PbO2 film and an untreated cell, each of 1.9 Ah-12 V, were completely charged, and were then discharged at 65C for 15 days to examine the relationship between the remaining capacities at 1.25 A discharge and the days elapsed. The results are illustrated in Figure 6. Just after being permitted to stand, both cells shows a capacity of 70 minutes. After the lapse of 15 days, ho~ever, the untreated cell exhibits a capacity short of 25 minutes, while the acid-immersed cell maintains a capacity of as long as ~0 minutes, which means that such acid immersion is also considerably effective for self-discharge.
Thus, the acid immersion gives rise to a passivated oxide film at the initial stage, which is to be for~ed when the untreated cell is allowed to stand for an extended period.
1323~7 Examples of the Sixth Aspect Accumulator cells of 1.2 Ah-2 V were prepared and filled with a predetermined amount of electrolytes (H2SO~ having a specific gravity of 1.320) containing a total of 0.2 moles of Nat and Mg2t in various proportions. After intially charged and subjected to an initial capacity test, these cells were discharged at a constant resistance for 24 hours. Afterwards, they were open-circuited and permitted to stand at 25C for one month. The cells were then charged at a constant voltage of 2.45 V to measure the charging currents after the lapse of 10 seconds, 30 seconds and 60 seconds. The results are set out in Table 4, wherein the current values are given on the basis of 100 which stands for the value for a current flowing in No. 3 after the lapse of 10 seconds, and the amounts of Nat and Mg2~ are given in terms of mol %, provided that the total amount of the additives is fixed at 0.2 moles.
Table _ No. Amount r Amount i Current I Current Current ¦
After Na+ After Mg2+ ¦ After ¦ After After ¦
(%) (Z~ 10 sec. i 30 sec. 60 sec.
1 1 100 1 0 ~ 43.5 1 102 174 _ __ l _ l 1 2 80 20 1 65.2 1 152 261 --I 60 I_ 95.7 - 195 - _ _26 520 1 80 1 78.3 143 257 _ 90 1 2~.3 1 65.2 137 -7~ 0 100 1 8.7 1 19.6 34. ~
The foregoing results were obtained with anyhydrous magnesium.
Ho~ever, similar results were also obtained with magnesium having crystallized water.
The cells (Nos. 2 to 6) containing a mixture of Na~ with Mg carry more charging currents than do the cells (Nos. 1 and 7) containing Nat or Mg2talone. This indicates that Na correlates with 13233~7 Mg2'. In particular, it is found that the effect of Nat is notappreciably observed in a region of 0.04 moles (about 400 ppm) or less. Especially when Na r is not used, the effect of the present invention is not attained at all. As mentioned above, Nat and Mg cooperate synergistically with each other to have an improved effect on the properties of lead accumulators at the time when they are permitted to stand in an over-discharged state.
Examples of the Seventh Aspect Prepared from grids plated on their surfaces with a Pb-Sn alloy were accumnlator cells, which were then examined on their chargeability and synergistic effects upon being permitted to stand in an over-discharged state with or without acid immersion treatments and in the presence or absence of alkaline metal ions and alkaline earth metal ions. The cells, each of 1.2 Ah-6 V, ~ere discharged at a constant resistance of 8 ohms for 24 hours, and were then permitted to stand for 7 days to measure their chargeability at 7.35 V by constant-voltage charge ~25C). As illustrated in Figure 7, the results are that the addition of Na~ and Mg2+ and plating have a limited or reduced effect upon the cells which are not immersed in an acid, but have a striking effect upon the cells treated by acid immersion, leading to a considerably increased charging current flowing therein.
More improved effects are obtained with the addition of both Na~ and Mg2t than with the addition of Nat or Mg2t alone. From the instant examples, it is evident that the three means, i.e., acid immersion, plating and the addition of Nat and Mg2t cooperate synergisticaily with one another. Similar effects are also obtained with ions of an alkaline earth metal having crystallized water.
An accumulator cell treated by acid immersion and an untreated cell, each of 1.9 Ah-12 V, were completely charged, and were then discharged at 65C for 15 days to examine a relationship between their 1323~7 remaining capacities at 1.25 A discharge and the days elapsed. The results are illustrated in Figure ~. Just after permitted to stand, both cells shows a capacity of 70 minutes. After the lapse of 15 days, however, the untreated cell exhibits a capacity short of 25 minutes, while the acid-treated cell maintains a capacity of as long as 40 minutes, which means that such acid immersion is also considerably effective for self-discharge. Thus, the acid immersion treatment gives rise to a passivated oxide film at the initial stage, which is to be formed when the untreated cell is allowed to stand for an extended period.
Pb-Ca MgS0~ jForm 1 43.5 ¦ Pb-Ca-Sn ¦ No t Not ¦ 51.3 Additive ¦Form --13 1 Pb-Ca-Sn ij Na2SO4 Not 67.2 _~ I Form 14 I Pb-Ca-Snt MgSO~ 7H20 Not 68.4 Form ___ ~
15 Pb-Ca-Sn ! Na2SO,. i Not ¦ 73.4 ¦ MgSO,. 7H20 ,! Form 1~b~a-Sn ~I Na2SO4 ¦Form ¦ 93.0 I ! ~ , . I
17 I Pb-Ca-Sn I No Form 1 76.5 ! Additive Inven-18 I Ph-Ca-Sn MgS0~ 7H20 ¦ For~ ! 93-4 ¦ tion19 ¦ Pb~a-Sn ¦ Na2SO~ IForm t 99.5 I__ I __ I I i 20 I Pb-Ca-Sn I MgSO~ 7H~0 I Form L 93.1 ~ 1 1 _ _ __ _I
1~233~7 From the table, it is found that the addition of Sn gives rise to a reovery of about 50 Z (No. 12), the incorporation of alkaline earth metal ions a recovery of about 16 % (Nos. 3, 4), the formation of an alpha-PbO2 film a recovery of 25 Z (No. 7) and the addition of both alkaline metal and earth metal ions a recovery of 5 X (No. 5).
Some synergism is obtained through a combination of two of these means. However, more improved effects are obtained by a combination of three means, i.e., Sn, alkaline earth metal ions and an alpha-PbO2 film. Cell Nos. 18 and 20 according to the present invention proved to be more effective than Cell Nos. 13 and 16 according to the prior art. MNch more improved effects are obtained in the presence of both alkaline metal and earth metal ions (No. 19), which are found to be very effective for the properties of the cell at the time when it is permitted to stand. T~is seems to be due to the fact that, as expected, Sn serves to suppress the formation of PbOx, alpha-PbO2 the formation of PbSO~, and Na~ , Mg2r and Mg(H2O)621 a lowering of conductivity.
An accumulator cell immersed in an acid to form an alpha-PbO2 film and an untreated cell, each of 1.9 Ah-12 V, were completely charged, and were then discharged at 65C for 15 days to examine the relationship between the remaining capacities at 1.25 A discharge and the days elapsed. The results are illustrated in Figure 6. Just after being permitted to stand, both cells shows a capacity of 70 minutes. After the lapse of 15 days, ho~ever, the untreated cell exhibits a capacity short of 25 minutes, while the acid-immersed cell maintains a capacity of as long as ~0 minutes, which means that such acid immersion is also considerably effective for self-discharge.
Thus, the acid immersion gives rise to a passivated oxide film at the initial stage, which is to be for~ed when the untreated cell is allowed to stand for an extended period.
1323~7 Examples of the Sixth Aspect Accumulator cells of 1.2 Ah-2 V were prepared and filled with a predetermined amount of electrolytes (H2SO~ having a specific gravity of 1.320) containing a total of 0.2 moles of Nat and Mg2t in various proportions. After intially charged and subjected to an initial capacity test, these cells were discharged at a constant resistance for 24 hours. Afterwards, they were open-circuited and permitted to stand at 25C for one month. The cells were then charged at a constant voltage of 2.45 V to measure the charging currents after the lapse of 10 seconds, 30 seconds and 60 seconds. The results are set out in Table 4, wherein the current values are given on the basis of 100 which stands for the value for a current flowing in No. 3 after the lapse of 10 seconds, and the amounts of Nat and Mg2~ are given in terms of mol %, provided that the total amount of the additives is fixed at 0.2 moles.
Table _ No. Amount r Amount i Current I Current Current ¦
After Na+ After Mg2+ ¦ After ¦ After After ¦
(%) (Z~ 10 sec. i 30 sec. 60 sec.
1 1 100 1 0 ~ 43.5 1 102 174 _ __ l _ l 1 2 80 20 1 65.2 1 152 261 --I 60 I_ 95.7 - 195 - _ _26 520 1 80 1 78.3 143 257 _ 90 1 2~.3 1 65.2 137 -7~ 0 100 1 8.7 1 19.6 34. ~
The foregoing results were obtained with anyhydrous magnesium.
Ho~ever, similar results were also obtained with magnesium having crystallized water.
The cells (Nos. 2 to 6) containing a mixture of Na~ with Mg carry more charging currents than do the cells (Nos. 1 and 7) containing Nat or Mg2talone. This indicates that Na correlates with 13233~7 Mg2'. In particular, it is found that the effect of Nat is notappreciably observed in a region of 0.04 moles (about 400 ppm) or less. Especially when Na r is not used, the effect of the present invention is not attained at all. As mentioned above, Nat and Mg cooperate synergistically with each other to have an improved effect on the properties of lead accumulators at the time when they are permitted to stand in an over-discharged state.
Examples of the Seventh Aspect Prepared from grids plated on their surfaces with a Pb-Sn alloy were accumnlator cells, which were then examined on their chargeability and synergistic effects upon being permitted to stand in an over-discharged state with or without acid immersion treatments and in the presence or absence of alkaline metal ions and alkaline earth metal ions. The cells, each of 1.2 Ah-6 V, ~ere discharged at a constant resistance of 8 ohms for 24 hours, and were then permitted to stand for 7 days to measure their chargeability at 7.35 V by constant-voltage charge ~25C). As illustrated in Figure 7, the results are that the addition of Na~ and Mg2+ and plating have a limited or reduced effect upon the cells which are not immersed in an acid, but have a striking effect upon the cells treated by acid immersion, leading to a considerably increased charging current flowing therein.
More improved effects are obtained with the addition of both Na~ and Mg2t than with the addition of Nat or Mg2t alone. From the instant examples, it is evident that the three means, i.e., acid immersion, plating and the addition of Nat and Mg2t cooperate synergisticaily with one another. Similar effects are also obtained with ions of an alkaline earth metal having crystallized water.
An accumulator cell treated by acid immersion and an untreated cell, each of 1.9 Ah-12 V, were completely charged, and were then discharged at 65C for 15 days to examine a relationship between their 1323~7 remaining capacities at 1.25 A discharge and the days elapsed. The results are illustrated in Figure ~. Just after permitted to stand, both cells shows a capacity of 70 minutes. After the lapse of 15 days, however, the untreated cell exhibits a capacity short of 25 minutes, while the acid-treated cell maintains a capacity of as long as 40 minutes, which means that such acid immersion is also considerably effective for self-discharge. Thus, the acid immersion treatment gives rise to a passivated oxide film at the initial stage, which is to be formed when the untreated cell is allowed to stand for an extended period.
Claims (7)
1. A lead accumulator having an electrolyte and a grid substrate formed of an alloy of lead with a metal or mixture of metals selected from the group:
(a) antimony and further containing any one of the metals sodium, lithium, potassium or tin;
(b) calcium and further containing tin, tin and antimony or tin and aluminum; and (c) calcium with no antimony and a coating of tin or an alloy of lead and tin;
the electrolyte in (a) and (b) containing alkaline earth metal ions and, in (c), alkaline earth and alkali metal ions.
(a) antimony and further containing any one of the metals sodium, lithium, potassium or tin;
(b) calcium and further containing tin, tin and antimony or tin and aluminum; and (c) calcium with no antimony and a coating of tin or an alloy of lead and tin;
the electrolyte in (a) and (b) containing alkaline earth metal ions and, in (c), alkaline earth and alkali metal ions.
2. An accumulator as claimed in claim 1 in which the grid substrate comprises a plate piece of a lead -calcium alloy integral with a base plate of lead - tin alloy and in which the electrolyte contains ions selected from alkali metal ions, alkaline earth metal ions and phosphate ions.
3. An accumulator as claimed in claim 1 including a positive plate that comprises a grid having an active substance thereon, the grid being an alloy of lead, calcium and tin, free from antimony, the positive plate having been immersed in dilute sulfuric acid.
4. An accumulator as claimed in claim 1 in which the electrolyte contains 500 ppm or higher of alkali metal ions as well as ions of an alkaline earth metal.
5. An accumulator as claimed in claim 1 or claim 4 in which the alkaline earth metal ions contain water of crystallization.
6. An accumulator as claimed in claim 1 including a positive grid that comprises a collector plate with a lead - tin alloy, having been immersed in dilute sulfuric acid, the electrolyte containing alkaline earth metal ions, alkali metal ions or both alkaline earth and alkali metal ions.
7. An accumulator as claimed in claim 1 or 2 or 3 in which the electrolyte in (a) and (b) also contains alkali metal ions.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP217164 | 1987-08-31 | ||
| JP62217164A JPS6460969A (en) | 1987-08-31 | 1987-08-31 | Lead storage battery |
| JP62217163A JPH01281683A (en) | 1987-08-31 | 1987-08-31 | Lead storage battery |
| JP217163 | 1987-08-31 | ||
| JP62217161A JPH0724224B2 (en) | 1987-08-31 | 1987-08-31 | Lead acid battery |
| JP217161 | 1987-08-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1323397C true CA1323397C (en) | 1993-10-19 |
Family
ID=27329991
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000575874A Expired - Fee Related CA1323397C (en) | 1987-08-31 | 1988-08-26 | Lead accumulators |
Country Status (5)
| Country | Link |
|---|---|
| KR (1) | KR950004457B1 (en) |
| CA (1) | CA1323397C (en) |
| DE (1) | DE3829258A1 (en) |
| FR (1) | FR2619961B1 (en) |
| GB (1) | GB2209241B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995015587A1 (en) * | 1993-11-30 | 1995-06-08 | Shi Xue Dou | Improved grid alloy for lead-acid battery |
| US6803151B2 (en) * | 2002-02-21 | 2004-10-12 | Delphi Technologies, Inc. | Electrode |
Family Cites Families (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB854358A (en) * | 1958-05-14 | 1960-11-16 | Ford Motor Co | Coated optical elements |
| BE684284A (en) * | 1965-07-20 | 1967-01-03 | ||
| DE1533246B1 (en) * | 1966-12-19 | 1972-03-09 | Cerjak Horst Dipl Ing Dr | CREEP RESISTANT LEAD ALLOYS |
| US3647545A (en) * | 1969-06-02 | 1972-03-07 | Gould National Batteries Inc | Battery electrode grids made from tin-lithium-lead alloy |
| GB1402099A (en) * | 1971-12-15 | 1975-08-06 | Lucas Batteries Ltd | Battery plate grids for lead-acid batteries |
| JPS5031931A (en) * | 1973-07-27 | 1975-03-28 | ||
| IN146036B (en) * | 1974-10-11 | 1979-02-10 | Gould Inc | |
| DE2504284C3 (en) * | 1975-02-01 | 1979-03-08 | Rheinisch-Westfaelisches Elektrizitaetswerk Ag, 4300 Essen | Chargeable, galvanic element |
| FR2300817A1 (en) * | 1975-02-11 | 1976-09-10 | Gould Inc | Lead-calcium-tin alloy for accumulators - esp. car batteries needing no refilling with water during use |
| US4125690A (en) * | 1976-03-05 | 1978-11-14 | Chloride Group Limited | Battery electrode structure |
| JPS5357437A (en) * | 1976-11-04 | 1978-05-24 | Ito Ichirou | Method of producing sulfuric acid battery electrolyte |
| IN153954B (en) * | 1981-03-03 | 1984-09-01 | Chloride India Limited | |
| DE3215489A1 (en) * | 1982-04-26 | 1983-11-03 | Varta Batterie Ag, 3000 Hannover | LEAD ACCUMULATOR WITH EXPANDER DEPOT |
| JPS5929375A (en) * | 1982-08-12 | 1984-02-16 | Shin Kobe Electric Mach Co Ltd | sealed lead acid battery |
| JPS5929383A (en) * | 1982-08-12 | 1984-02-16 | Shin Kobe Electric Mach Co Ltd | sealed lead acid battery |
| IT1164276B (en) * | 1983-06-27 | 1987-04-08 | Magneti Marelli Spa | LEAD-ACID ELECTRIC STORAGE BATTERY OF THE TYPE WITHOUT MAINTENANCE, PRESERVED HUMID CHARGE, FULLY WATERPROOF DURING STORAGE |
| JPS609065A (en) * | 1983-06-28 | 1985-01-18 | Shin Kobe Electric Mach Co Ltd | Sealed lead storage battery |
| US4805277A (en) * | 1986-06-05 | 1989-02-21 | Matsushita Electric Industrial Co., Ltd. | Process for producing a grid for use in lead acid batteries |
| JPH0679493B2 (en) * | 1986-07-11 | 1994-10-05 | 東海産業株式会社 | Lead-acid battery function recovery agent and lead-acid battery function recovery method |
| DE3721419A1 (en) * | 1987-06-29 | 1989-01-12 | Schleenbaecker Klaus J | Composition for producing a soft, completely reversible sulphation |
| JPH05207428A (en) * | 1992-01-24 | 1993-08-13 | Matsushita Electric Ind Co Ltd | Scan converter |
-
1988
- 1988-08-26 CA CA000575874A patent/CA1323397C/en not_active Expired - Fee Related
- 1988-08-26 GB GB8820351A patent/GB2209241B/en not_active Expired - Lifetime
- 1988-08-29 DE DE3829258A patent/DE3829258A1/en not_active Withdrawn
- 1988-08-29 KR KR1019880011016A patent/KR950004457B1/en not_active IP Right Cessation
- 1988-08-31 FR FR8811610A patent/FR2619961B1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB2209241B (en) | 1992-04-15 |
| FR2619961B1 (en) | 1994-09-23 |
| FR2619961A1 (en) | 1989-03-03 |
| KR950004457B1 (en) | 1995-05-01 |
| GB8820351D0 (en) | 1988-09-28 |
| GB2209241A (en) | 1989-05-04 |
| DE3829258A1 (en) | 1989-03-09 |
| KR890004464A (en) | 1989-04-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6833216B2 (en) | Method of manufacturing a sulfated paste for use in a lead acid cell | |
| EP0127301B1 (en) | Improved positive battery plate | |
| CN103109412B (en) | Lead battery and be equipped with the idling stop vehicle of this lead battery | |
| US5024908A (en) | Lead storage battery | |
| JPS63213264A (en) | lead acid battery | |
| CA1323397C (en) | Lead accumulators | |
| US4086392A (en) | Method for reducing the float current of maintenance-free battery | |
| GB2238159A (en) | Lead accumulator | |
| GB2247344A (en) | Lead accumulators having improved charging properties after standing in over discharged state | |
| JPH0770321B2 (en) | Sealed lead acid battery | |
| JPS63244568A (en) | lead acid battery | |
| JP2000200598A (en) | Sealed lead-acid battery | |
| JP3102000B2 (en) | Lead storage battery | |
| JPS63213263A (en) | lead acid battery | |
| JP2523585B2 (en) | Sealed lead acid battery | |
| JPH0548586B2 (en) | ||
| JP2808685B2 (en) | Lead storage battery | |
| JPS588558B2 (en) | Positive electrode grid for lead-acid batteries | |
| JPH0412586B2 (en) | ||
| JPS63207057A (en) | lead acid battery | |
| JPH0434845A (en) | lead acid battery | |
| JPH01117279A (en) | lead acid battery | |
| JPH1092462A (en) | Sealed lead-acid battery | |
| JPS5924500B2 (en) | lead acid battery | |
| JPS6352745B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |