JP4240422B2 - Organic electrolyte secondary battery - Google Patents

Description

【００６２】
表１に示す放電容量の測定結果から明らかなように、リン酸トリメチルを単独で有機電解液の構成溶媒として用いた比較例２は、まったく放電しなかった。しかし、リン酸トリメチルにエチレンカーボネートやプロピレンカーボネートなどの環状炭酸エステルまたは１，２−ビスエトキシカルボニルオキシエチレンなどの炭酸エステルの多量体を併用した実施例１〜４では、高容量が得られた。
【００６３】
また、引火性試験の結果から明らかなように、リン酸トリメチルを含有しない通常の有機電解液を用いた比較例１では、約４０℃に加熱した時点で引火し、燃えだしたが、有機電解液中にリン酸トリメチルを含有させた実施例１〜４では、１００℃まで加熱しても引火せず、火災に対して高い安全性を有していた。
【００６４】
また、発火性試験の結果から明らかなように、通常の有機電解液を用いた比較例１は、発火がみられたが、有機電解液中にリン酸トリメチルの含有させた実施例１〜４では、発火することなく、釘刺しにより内部短絡が生じても安全性の高い電池が得られた。
【００６５】
【発明の効果】
以上説明したように、本発明では、高容量で、かつ安全性の高い有機電解液二次電池を提供することができた。
【図面の簡単な説明】
【図１】本発明の有機電解液二次電池の一実施例を模式的に示す縦断面図である。
【符号の説明】
１ 正極
２ 負極
３ セパレータ
４ 有機電解液[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electrolyte secondary battery, and more particularly to an organic electrolyte secondary battery having a high capacity and high safety.
[0002]
[Prior art]
An organic electrolyte secondary battery represented by a lithium ion secondary battery has high capacity, high voltage, and high energy, and therefore has high expectations for its development.
[0003]
In this organic electrolyte secondary battery, lithium or a lithium alloy has been used as the negative electrode active material. However, when these negative electrode active materials are used, high capacity can be expected, but internal short circuit occurs due to lithium dendrite growth during charging. As a result, there are problems that the battery performance is lowered and the safety is poor.
[0004]
Therefore, it has been proposed to use a carbon material such as activated carbon or graphite that can be doped / undoped with lithium ions as a negative electrode active material instead of lithium or a lithium alloy (Japanese Patent Publication No. 4-24831, Japanese Patent Publication No. 5-17669).
[0005]
The graphite can capture one lithium ion for every six carbon atoms, which corresponds to 830 mAh / ml in terms of capacity per unit volume. However, due to the entry and exit of lithium ions due to charge and discharge, the graphite has an interlayer distance of about 10% larger than that of complete discharge (a state that does not include lithium) during a full charge (a state that includes lithium corresponding to 372 mAh / g). When charging and discharging are repeated, the negative electrode active material graphite is peeled off from the current collector due to the expansion and contraction, or finely pulverized, resulting in a decrease in battery performance. Therefore, in order to obtain a life of 500 cycles or more with graphite, there is a restriction that it must be used in a range of usually 250 mAh / g (600 mAh / ml) or less.
[0006]
As a material having a higher capacity than graphite, there is low crystalline carbon. This low crystalline carbon can insert lithium ions into the voids in the amorphous part as well as between the layers, and since there is almost no expansion or contraction of the lattice spacing during charging / discharging, it is expected to increase the cycle life. Yes. However, this low crystalline carbon has a theoretical maximum of 1200 mAh / g (ie, C ₂ Although a high capacity can be expected up to the Li state), since the true density is low, the capacity per volume is not much different from graphite.
[0007]
Therefore, the capacity is increased by using an oxide mainly composed of a group 14 or group 15 metal or semimetal in the periodic table as a negative electrode active material (JP-A-6-275268, JP-A-7-122274). And the use of silicon oxide as a negative electrode active material has been proposed (JP-A-6-325765, JP-A-7-29602, JP-A-9-7638). ).
[0008]
[Problems to be solved by the invention]
By the way, in the organic electrolyte secondary battery as described above, since an organic solvent is used as a constituent solvent of the electrolyte, it is required that there is no risk of ignition and ignition. Measures are taken to prevent overcharging and prevent internal short circuiting, and in general internal short circuiting, the battery only generates heat, causing problems with safety. Not to be.
[0009]
However, if the negative electrode active material that can be expected to increase in capacity as described above is used to increase the capacity or depending on the specifications required by the user, the battery configuration must be deliberately devised. It was found that the safety tends to decrease when a crushing test and a nail penetration test, which are safety confirmation tests under severe conditions assuming abnormal use.
[0010]
Such crushing tests and nail penetration tests are based on the assumption that the battery is destroyed intentionally or due to some accident, and cannot occur under normal use conditions. In crushing tests and nail penetration tests, it is desirable to make them safe so that there is no risk of ignition or ignition. In particular, the oxide-based negative electrode active material as described above is suitable for high capacity because it can contain a large amount of lithium. However, when short-circuited, an enormous current flows instantaneously, and the Joule heat rapidly generates heat, resulting in a high temperature. Therefore, there is a problem that the possibility of ignition or ignition increases during abnormal use.
[0011]
The present invention solves the safety problems that may occur due to abnormal use in the case of increasing the capacity as described above, and even when a negative electrode active material that can be expected to increase in capacity is used, ignition and ignition are possible. An object of the present invention is to provide a high-capacity and high-safety organic electrolyte secondary battery.
[0012]
[Means for Solving the Problems]
The present invention relates to a lithium host that can include at least one lithium ion selected from the group consisting of oxides, sulfides and nitrides of metals or metalloids of group 13 to group 15 in the periodic table as a negative electrode active material. And at least one of a cyclic carbonate or a carbonate ester multimer and a phosphate triester in an organic electrolyte, and a phosphate triester, a cyclic carbonate and a carbonate ester multimer, The volume ratio of the mixture is 99: 1 to 50:50, and the content of the organic solvent other than the phosphate triester, cyclic carbonate and carbonate ester multimer in the entire constituent solvent of the organic electrolyte is 20 volumes. The above-mentioned problem has been solved by setting the ratio to not more than%.
[0013]
In the present invention, as described above, as the negative electrode active material, lithium ions comprising at least one selected from the group consisting of oxides, sulfides and nitrides of metals or metalloids of Group 13 to Group 15 or 15 in the periodic table. By using a lithium host compound that can include the above, a high-potential, high-capacity organic electrolyte secondary battery can be obtained.
[0014]
And by containing phosphoric acid triester in the organic electrolyte solution, the danger of ignition and ignition is eliminated, and by using at least one of cyclic carbonate or carbonic acid ester multimer in combination with the above phosphate triester Further, it is possible to prevent a decrease in discharge capacity based on the use of the phosphoric acid triester, and in combination with the use of the specific negative electrode active material, an organic electrolyte secondary battery having a high capacity and high safety can be obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the group 13 to group 15 metal or semimetal in the periodic table is preferably an element from the third period onward in the periodic table, for example, B, Al, Si, P, Ga, Ge, In, Sn and the like are preferable.
[0016]
In the present invention, a lithium host compound that can include lithium ions used as a negative electrode active material, and examples of oxides of metals or metalloids of Groups 13 to 15 in the periodic table include, for example, SiO, SnO, SnO ₂ , PbO, PbO ₂ The group 13 to group 15 metal or metalloid sulfides include, for example, SnS and SnS. ₂ , PbS, PbS ₂ And the like are preferable, and these are used alone or in combination of two or more. And these lithium host compounds come to act as a negative electrode active material by including lithium ion at the time of charge. In addition, the lithium host compound that can include lithium ions in the present invention may contain lithium during synthesis (that is, after battery assembly and before charging), and contains lithium during such synthesis. Examples of the compound include Li _x M _y O _z , Li _x M _y S _z , Li _x M _y N _z (Here, M is a metal or semimetal of Groups 13 to 15 in the periodic table, and x, y, and z are 0 ≦ x ≦ 6, 1 ≦ y ≦ 4, and 1 ≦ z ≦ 18, respectively) Among these, oxide-based Li that can be expected to have a high potential and a high capacity _p SiO _q, Li _p SnO _q Here, p and q are 0 ≦ p ≦ 6 and 1 ≦ q ≦ 14, respectively.
[0017]
In the present invention, a lithium host compound used as a negative electrode active material, and an example of a method for synthesizing oxides, sulfides, and nitrides containing lithium at the time of synthesis is shown. As a lithium source, lithium hydroxide, lithium carbonate, nitric acid Lithium, lithium acetate, lithium nitride, lithium sulfide, lithium sulfate, lithium sulfite, lithium phosphate, lithium tetraborate, lithium chlorate, lithium perchlorate, lithium thiocyanate, lithium oxalate, lithium citrate, lithium lactate, lithium tartrate , Using lithium trifluoromethanoate, etc., mixing these lithium sources and oxides, sulfides, nitrides, etc. of metals or metalloids of group 13 to group 15 in the above periodic table, and firing the resulting mixture By doing so, it is possible to obtain a lithium host compound containing lithium during synthesis. That. At this time, the mixing molar ratio between the lithium source and the group 13 to group 15 metal or metalloid oxide, sulfide, nitride, etc. in the periodic table should be in the range of 1:10 to 12: 1. Preferably, the obtained mixture is calcined in a vacuum or an inert gas atmosphere at 250 to 2000 ° C., particularly near the melting point or decomposition point of the lithium source.
[0018]
Further, the lithium host compound used as the negative electrode active material in the present invention uses an oxide, sulfide, nitride, or the like of a metal or a metal of group 13 to group 15 in the periodic table, and is contained in an electrolytic cell before the battery is incorporated. It can also be obtained by electrochemically inserting lithium ions.
[0019]
Furthermore, the lithium host compound used as the negative electrode active material in the present invention may not be a single metal or metalloid oxide, sulfide, or nitride, but may be a plurality of metal or metalloid oxides, sulfides, Nitride may be used. Of these, oxides having particularly good stability are preferred. As a specific example of such a lithium host compound, for example, SnSiO _Three , SnPbO _Three , SnBPO ₆ Etc. These oxides, sulfides and nitrides may be used alone or in combination of two or more.
[0020]
In the present invention, the lithium host compound used as the negative electrode active material may be crystalline or amorphous, but the amorphous one has higher lithium ion conductivity, higher capacity, and cycle characteristics. Is preferable because it is excellent.
[0021]
In the present invention, a lithium host compound that can include lithium ions composed of oxides, sulfides, and nitrides of metals or metalloids of groups 13 to 15 in the periodic table as described above is used as the negative electrode active material. As a result, high-potential and high-capacity organic electrolyte secondary batteries can be obtained. However, since these negative electrode active materials contain a large amount of energy, sudden heat generation is required in the countermeasures using conventional safety elements such as safety valves and PTC elements. If there is an abnormality that cannot be suppressed, ignition or ignition may occur. However, in order to achieve high capacity, it is necessary to use a negative electrode active material that can be expected to have such high capacity.
[0022]
Therefore, in the present invention, the problem of ignition / ignition is solved by including a phosphoric triester in the organic electrolyte. The phosphate triester has the general formula: (RO) _Three P = O (wherein R is an organic group, and the three organic groups may be the same or different), and is an organic solvent with low flammability, Even in an organic electrolyte secondary battery using a negative electrode active material that can be expected to have a large capacity, safety can be sufficiently improved. Particularly in safety confirmation tests under severe conditions, such as a nail penetration test, an internal short circuit is forcibly generated, and the organic electrolyte leaks out of the battery. By including the ester in the organic electrolyte, the risk of ignition and ignition can be reduced. Examples of such phosphoric acid triesters include the above general formula (RO). _Three In P = O, trialkyl phosphates in which R is an alkyl group having 1 to 6 carbon atoms, for example, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate and the like are preferably used.
[0023]
However, when the phosphoric acid triester is contained in the organic electrolyte, the discharge capacity of the negative electrode active material composed of the above-described lithium host compound or the like is remarkably lowered, and in some cases, the discharge may not be performed at all. Although this cause is not necessarily clear, it is thought that a film formed by the decomposition of the phosphoric acid triester is formed on the negative electrode surface, which prevents the movement of lithium ions.
[0024]
Therefore, in the present invention, by using at least one of cyclic carbonates or multimers of carbonates together with the phosphoric acid triester, a reduction in discharge capacity based on the use of the phosphoric acid triester is suppressed, and a high capacity is achieved. And succeeded in obtaining a highly safe organic electrolyte secondary battery. That is, by using at least one of cyclic carbonate or carbonic acid ester multimer in combination, it is suitable for the charge / discharge reaction before the coating based on the phosphate triester is formed on the surface of the negative electrode. When a coating based on at least one of the cyclic carbonate or carbonate ester multimer is formed, and on the surface of the negative electrode, a coating based on at least one of the cyclic carbonate or carbonate multimer is formed, A coating based on at least one of the cyclic carbonate or carbonate multimer prevents the phosphoric triester that inactivates the surface of the negative electrode from coming into direct contact with the surface of the negative electrode. Since the coating based on at least one of the carbonate ester multimers also contributes to ionic conduction, lithium ion It can be doped and dedoped now be performed smoothly, to prevent a decrease in discharge capacity based on the use of phosphoric acid triesters.
[0025]
Examples of the cyclic carbonate as described above include ethylene carbonate, propylene carbonate, butylene carbonate, pentene carbonate and the like, and ethylene carbonate, propylene carbonate and the like are particularly preferable.
[0026]
In addition, the carbonate ester multimer as described above may be represented by the general formula: R ₁ OC (O) OR ₂ OC (O) OR _Three (However, R ₁ , R _Three Is an alkyl group having 1 to 4 carbon atoms, R ₂ Are alkyl groups having 2 to 4 carbon atoms, which may be the same or different, and are represented by, for example, 1,2-bismethoxycarbonyloxyethylene, 1,2-bis Examples include methoxycarbonyloxypropylene, 1,2-bisethoxycarbonyloxyethylene, 1,2-bisethoxycarbonyloxypropylene, and the like.
[0027]
Either one of the cyclic carbonate and the carbonate multimer may be used, but both may be used in combination.
[0028]
The mixing ratio of phosphoric acid triester and at least one of cyclic carbonate or carbonic acid ester multimer is preferably 99: 1 to 50:50, and 98: 2 to 80:20 in volume ratio. It is more preferable. The amount of phosphoric acid triester is 50 or more (that is, 50% by volume) with respect to the total amount with at least one of cyclic carbonates or multimers of carbonates (volume ratio with the total volume being 100). In this manner, the flammability of the organic electrolyte can be sufficiently reduced, and at least one amount of the cyclic carbonate or multimer of the carbonate is added to the total amount of the phosphate triester. By setting the volume ratio to 1 or more (that is, 1 volume% or more), a high induction rate can be ensured, and a high capacity can be achieved.
[0029]
In addition, a conventionally used organic solvent may be added to the organic electrolyte, and examples of such an organic solvent include a chain ester, a chain ether, a cyclic ether, a chain carbonate, and the like. In this case, the amount of the organic solvent added is, in order to ensure the effect based on at least one of a phosphate triester and a cyclic carbonate or a carbonate multimer, It is 20 volume% or less with respect to the whole constituent solvent, and 5 volume% or less is preferable.
[0030]
Examples of the electrolyte of the organic electrolyte include LiClO. _Four , LiPF ₆ , LiBF _Four , LiAsF ₆ , LiSbF ₆ , LiCF _Three SO _Three , LiC _Four F ₉ SO _Three , LiCF _Three CO ₂ , Li ₂ C ₂ F _Four (SO _Three ) ₂ , LiN (CF _Three SO ₂ ) ₂ , LiC (CF _Three SO ₂ ) _Three , LiC _n F _{2n + 1} SO _Three (N ≧ 2) and the like are used alone or in combination of two or more. Among them, LiPF ₆ And LiC _Four F ₉ SO _Three Is particularly suitable because of its good charge / discharge characteristics. The concentration of these electrolytes in the organic electrolytic solution is not particularly limited, but usually 0.1 to 2 mol / liter, particularly about 0.4 to 1 mol / liter is preferable.
[0031]
Furthermore, in the present invention, when carbon dioxide is dissolved in the organic electrolyte as described above, a high capacity is easily achieved. This is because in an organic electrolyte secondary battery, the reaction between the negative electrode active material and the constituent solvent of the organic electrolyte tends to occur, and the reaction product tends to inhibit the charge / discharge reaction or decrease the capacity. However, if carbon dioxide is contained in the organic electrolyte, it can be prevented by carbon dioxide. More specifically, when carbon dioxide is contained in the organic electrolyte, a thin film mainly composed of organic / inorganic carbonate is formed on the surface of the negative electrode active material. Since the reaction with the constituent solvent of the electrolytic solution is suppressed, and the coating does not adversely affect the charge / discharge reaction and does not cause a decrease in capacity, the ability of the positive electrode material and the negative electrode material can be maximized. Battery capacity can be improved.
[0032]
In addition, the carbon dioxide content in the organic electrolyte is LiNiO as the positive electrode active material. ₂ LiCoO ₂ LiMnO _Four This is particularly effective when a lithium composite oxide having a closed circuit voltage at the time of charging such as 4 V or more based on Li is used. These positive electrode active materials have a high potential, and under normal conditions, the constituent solvent of the organic electrolyte is oxidized and the discharge performance is lowered. However, carbon dioxide having excellent oxidation resistance is contained in the organic electrolyte. Carbon dioxide suppresses decomposition of the constituent solvent of the organic electrolyte due to oxidation on the surface of the positive electrode. Especially LiNiO ₂ Is difficult to use because it is more reactive with the constituent solvent of the organic electrolyte than other metal oxides, but by adding carbon dioxide in the organic electrolyte, such LiNiO ₂ Even in the case of using, the reactivity of the organic electrolyte with the constituent solvent is suppressed, and the capacity of the battery is increased.
[0033]
In the present invention, when preparing the negative electrode, a conductive additive, a binder, or the like can be added to the negative electrode active material as necessary. Examples of the conductive aid include non-carbon materials such as nickel powder, and carbon-based materials such as graphite, acetylene black, carbon black, and coke. Among these conductive aids, the (002) plane interlayer is also included. Distance (d ₀₀₂ ) Is preferably a low crystalline carbon material of 0.338 nm or more. Although the addition amount of this conductive support agent is not specifically limited, 1-30 weight% is preferable with respect to a negative electrode active material, and 2-15 weight% is especially preferable. Examples of the binder include polyacrylic acid, carboxymethyl cellulose, polyvinylidene fluoride, polytetrafluoroethylene, and ethylene propylene diene rubber, and polyacrylic acid and carboxymethyl cellulose are particularly preferable. The addition amount of the binder is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 2 to 20% by weight with respect to the negative electrode active material.
[0034]
In producing the negative electrode, for example, water or a solvent is added to and mixed with the negative electrode mixture composed of the negative electrode active material, a conductive additive, a binder, and the like to prepare a slurry paint. Is applied to a current collector and dried to form a negative electrode through a step of forming a coating film. However, the method for manufacturing the negative electrode is not limited to the above method, and other methods may be adopted.
[0035]
In the present invention, the positive electrode active material is not particularly limited, and various materials can be used. For example, LiNiO ₂ LiCoO ₂ , LiMn ₂ O _Four Lithium composite oxides such as are preferably used because a high voltage can be obtained. In preparation of the positive electrode, for example, a conductive auxiliary agent, a binder, etc. are added to the positive electrode active material as necessary, and a solvent is further added and mixed to prepare a slurry-like paint, followed by drying. And the method of producing a positive electrode through the process of forming a coating film is employ | adopted. However, the method for manufacturing the positive electrode is not limited to the above-described examples, and other methods may be adopted. Moreover, as a conductive support agent and a binder, the thing similar to the case of the said negative electrode can be used, The usage-amount with respect to those positive electrode active materials may be comparable as the usage-amount with respect to the said negative electrode active material.
[0036]
In the present invention, as a coating method when applying a paint containing the negative electrode active material or the positive electrode active material to the current collector, various coating methods including, for example, extrusion coater, reverse roller, doctor flade, etc. Can be adopted.
[0037]
In the present invention, as a current collector for electrodes such as a positive electrode and a negative electrode, for example, a metal net such as aluminum, stainless steel, titanium, and copper, a punched metal, an expanded metal, a foam metal, and a foil are used. .
[0038]
As the separator, for example, a microporous polyethylene film or a microporous polypropylene film having a thickness of 10 to 15 μm and a porosity of 30 to 70% is preferably used.
[0039]
For example, a battery includes a spirally structured electrode body such as a spiral electrode body fabricated by stacking a separator between a positive electrode and a negative electrode fabricated as described above and winding the separator in a spiral shape. It is manufactured through a process of inserting and sealing in a nickel-plated iron or stainless steel battery case. The battery usually incorporates an explosion-proof mechanism that discharges gas generated inside the battery to a certain pressure to the outside of the battery to prevent the battery from bursting under high pressure.
[0040]
【Example】
Next, the present invention will be described more specifically with reference to examples. However, this invention is not limited only to those Examples.
[0041]
Example 1
LiPF ₆ Is dissolved in trimethyl phosphate, and ethylene carbonate is added and mixed, so that LiPF is mixed in a mixed solvent of trimethyl phosphate and ethylene carbonate in a volume ratio of 98: 2. ₆ Was dissolved in an amount of 1.0 mol / liter.
[0042]
Also, lithium cobalt oxide (LiCoO ₂ ) To 91 parts by weight, 6 parts by weight of graphite and 3 parts by weight of polyvinylidene fluoride were added and mixed to prepare a positive electrode mixture, which was dispersed with N-methylpyrrolidone to prepare a slurry paint. The slurry-like paint containing the positive electrode mixture is uniformly applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm and dried to form a coating film made of the positive electrode mixture, and then a roller press machine The lead body was welded to form a sheet-like positive electrode having a thickness of 160 μm.
[0043]
Separately from the above, 45 parts by weight of silicon monoxide (SiO) is mixed with 40 parts by weight of graphite and 15 parts by weight of polyacrylic acid to prepare a negative electrode mixture, which is dispersed with water to form a slurry-like paint. Prepared. A slurry press containing this negative electrode mixture is uniformly applied to both surfaces of a negative electrode current collector made of a copper foil having a thickness of 18 μm, dried to form a coating film made of the negative electrode mixture, and then a roller press machine. Then, the lead body was welded to prepare a sheet-like negative electrode having a thickness of 40 μm.
[0044]
Next, the sheet-like positive electrode and the sheet-like negative electrode are overlapped with a separator made of a microporous polyethylene film having a thickness of 25 μm interposed therebetween, and wound in a spiral shape to produce a spiral electrode body. Then, the spiral electrode body is filled in a cylindrical battery case having a bottomed cylindrical shape with an outer diameter of 18 mm, and then the opening of the battery case is sealed to produce the cylindrical organic electrolyte secondary battery shown in FIG. did.
[0045]
Referring to the battery shown in FIG. 1, 1 is the sheet-like positive electrode and 2 is the sheet-like negative electrode. However, in FIG. 1, in order to avoid complication, a metal foil or the like is not illustrated as a current collector used in manufacturing the positive electrode 1 or the negative electrode 2. The positive electrode 1 and the negative electrode 2 are spirally wound through a separator 3 and are housed in a battery case 5 together with the organic electrolyte 4 as a spiral electrode body.
[0046]
The battery case 5 is made of stainless steel and also serves as a negative electrode terminal. An insulator 6 made of polytetrafluoroethylene is disposed at the bottom of the battery case 5 prior to the insertion of the spiral electrode body. The sealing plate 7 is made of aluminum, has a disk shape, has a thin portion 7a at the center, and serves as a pressure introduction port 7b for allowing the battery internal pressure to act on the explosion-proof valve 9 around the thin portion 7a. A hole is provided. And the protrusion part 9a of the explosion-proof valve 9 is welded to the upper surface of this thin part 7a, and the welding part 11 is comprised. In addition, the thin-walled portion 7a and the explosion-proof valve 9a provided on the sealing plate 7 are shown only on the cut surface for easy understanding on the drawing, and the outline behind the cut surface is omitted. is doing. In addition, the welded portion 11 between the thin portion 7a of the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 is also shown in an exaggerated state so as to facilitate understanding on the drawing.
[0047]
The terminal board 8 is made of rolled copper, has a nickel-plated surface, and has a hat shape with a peripheral edge portion, and the terminal board 8 is provided with a gas discharge hole 8a. The explosion-proof valve 9 is made of aluminum and has a disk shape, and a projection 9a having a tip on the power generation element side (lower side in FIG. 1) is provided at the center of the explosion-proof valve 9. As described above, the lower surface is welded to the upper surface of the thin portion 7 a of the sealing plate 7 to constitute the welded portion 11. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is arranged at the upper part of the peripheral edge of the sealing plate 7. The explosion-proof valve 9 is arranged at the upper part, and the sealing plate 7 and the explosion-proof valve 9 are insulated. The gap between the two is sealed so that the organic electrolyte does not leak between the two. The annular gasket 12 is made of polypropylene, the lead body 13 is made of aluminum, connects the sealing plate 7 and the positive electrode 1, the insulator 14 is disposed above the spiral electrode body, and the negative electrode 2 and the battery case 5 The bottom is connected by a lead body 15 made of nickel.
[0048]
As described above, the insulator 6 is disposed at the bottom of the battery case 5, and the spiral electrode body composed of the positive electrode 1, the negative electrode 2, and the separator 3, the organic electrolyte 4, and the insulator 14 above the spiral electrode body. Are accommodated in the battery case 5, and after the accommodation, an annular groove having a bottom protruding inward is formed in the vicinity of the opening end of the battery case 5. Then, an annular gasket 12 in which a sealing plate 7, an insulating packing 10, and an explosion-proof valve 9 are inserted is inserted into the opening of the battery case 5, and a terminal plate 8 is further inserted over the annular gasket 12. By tightening the portion inward, the opening of the battery case 5 is sealed. However, in assembling the battery as described above, it is preferable that the negative electrode 2 and the battery case 5 are connected in advance by the lead body 15 and the positive electrode 1 and the sealing plate 7 are connected by the lead body 13 in advance.
[0049]
In the battery assembled as described above, the welded portion 11 is in contact with the thin portion 7a of the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9, and the peripheral portion of the explosion-proof valve 9 and the peripheral portion of the terminal plate 8 are Are in contact with each other, and the positive electrode 1 and the sealing plate 7 are connected by the lead body 13 on the positive electrode side. Therefore, the positive electrode 1 and the terminal plate 8 are connected to the lead body 13, the sealing plate 7, the explosion-proof valve 9, and their welded portions 11. Provides an electrical connection and functions normally as an electrical circuit.
[0050]
Then, when an abnormality occurs in the battery and gas is generated inside the battery and the internal pressure of the battery rises, the central portion of the explosion-proof valve 9 is moved in the internal pressure direction (upward direction in FIG. 1) due to the increase of the internal pressure. Along with this, a shearing force is applied to the thin portion 7a integrated at the welded portion 11, and the thin portion 7a is broken, or the protruding portion 9a of the explosion-proof valve 9 and the thin portion 7a of the sealing plate 7 are broken. As a result, the welded portion 11 is peeled off, whereby the electrical connection between the positive electrode 1 and the terminal plate 8 is lost, and the current is interrupted. As a result, the battery reaction does not proceed, so that even when overcharged or short-circuited, the battery temperature rise or internal pressure rise no longer proceeds due to the charging current or short-circuit current, so that the battery can be prevented from firing or bursting. Designed.
[0051]
The explosion-proof valve 9 is provided with a thin-walled portion 9b. For example, when a large amount of gas is generated due to decomposition of a power generation element such as an organic electrolyte or an active material due to extreme progress of charging, the explosion-proof valve 9 After the valve 9 is deformed and the welded portion 11 between the protruding portion 9a of the explosion-proof valve 9 and the thin-walled portion 7a of the sealing plate 7 is peeled off, the thin-walled portion 9b provided on the explosion-proof valve 9 is cleaved to release the gas to the terminal plate It is designed so that the battery can be prevented from rupturing by being discharged out of the battery through the gas discharge holes 8a.
[0052]
Example 2
SnO and SiO as negative electrode active materials ₂ SnSiO obtained by mixing at a molar ratio of 1: 1, firing at 1000 ° C. in an argon atmosphere, and quenching. _Three An organic electrolyte secondary battery was produced in the same manner as in Example 1 except that was used.
[0053]
Example 3
An organic electrolyte secondary battery was produced in the same manner as in Example 1 except that propylene carbonate was used instead of ethylene carbonate as a constituent solvent of the organic electrolyte.
[0054]
Example 4
An organic electrolyte secondary battery was produced in the same manner as in Example 1 except that 1,2-bisethoxycarbonyloxyethylene was used in place of ethylene carbonate as a constituent solvent of the organic electrolyte.
[0055]
Comparative Example 1
An organic electrolyte secondary battery was produced in the same manner as in Example 1 except that methyl ethyl carbonate was used as a constituent solvent of the organic electrolyte instead of trimethyl phosphate.
[0056]
Comparative Example 2
An organic electrolyte secondary battery was produced in the same manner as in Example 1 except that only trimethyl phosphate was used as a constituent solvent of the organic electrolyte.
[0057]
The discharge capacities of the batteries of Examples 1 to 4 and Comparative Examples 1 and 2 obtained as described above were measured, and flammability tests and ignitability tests were performed. The measurement methods and test methods are as follows.
[0058]
Discharge capacity:
The batteries of Examples 1 to 4 and Comparative Examples 1 to 2 were charged and discharged at 20 ° C. and 0.2 C in the voltage range of 2.75 to 4.1 V, and the initial discharge capacity was measured. The obtained discharge capacity is shown in Table 1 as a value converted to the capacity per unit volume of the negative electrode active material.
[0059]
Flammability test:
Regarding the batteries in Examples 1 to 4 and Comparative Examples 1 and 2, the battery was heated to a high temperature and the safety valve was activated (i.e., in the battery shown in FIG. 1, by evaporation of the constituent solvent from the organic electrolyte, etc. When the gas is generated inside the battery and the internal pressure of the battery rises and reaches a predetermined pressure, the thin-walled portion 7a provided on the inner side from both end surfaces in the thickness direction of the sealing plate 7 extends in the internal pressure direction of the explosion-proof valve 9. The thin wall portion 7a of the sealing plate 7 is destroyed in advance by assuming that the gas inside the battery is destroyed by the shearing force generated in accordance with the change of the gas and the gas inside the battery is discharged from the gas discharge hole 8a). In this state, the battery was heated to 100 ° C., and a fire was brought close to the gas discharge hole 8a of the battery to examine whether or not it would ignite. The results are shown in Table 1.
[0060]
Ignition test:
For the batteries of Examples 1 to 4 and Comparative Examples 1 and 2, a nail penetration test was performed. In the nail penetration test, the battery was charged to 4.18 V and left in a 45 ° C. constant temperature bath for 4 hours. The number of batteries that pierced to half and ignited in each of the five batteries was examined. The results are shown in Table 1. In Table 1, the denominator of the numerical value indicating the result of the ignitability test is the number of batteries subjected to the test, and the numerator is the number of batteries ignited.
[0061]
[Table 1]

[0062]
As is apparent from the measurement results of the discharge capacity shown in Table 1, Comparative Example 2 using trimethyl phosphate alone as a constituent solvent of the organic electrolyte did not discharge at all. However, in Examples 1 to 4, in which trimethyl phosphate was used in combination with a cyclic carbonate such as ethylene carbonate or propylene carbonate or a multimer of carbonate such as 1,2-bisethoxycarbonyloxyethylene, a high capacity was obtained.
[0063]
In addition, as is apparent from the results of the flammability test, in Comparative Example 1 using a normal organic electrolytic solution not containing trimethyl phosphate, it was ignited and started to burn when heated to about 40 ° C. In Examples 1 to 4 in which trimethyl phosphate was contained in the liquid, it did not ignite even when heated to 100 ° C., and had high safety against fire.
[0064]
As is clear from the results of the ignitability test, in Comparative Example 1 using a normal organic electrolyte, ignition was observed, but Examples 1-4 in which trimethyl phosphate was contained in the organic electrolyte. Then, a battery with high safety was obtained even if an internal short circuit occurred due to nail penetration without firing.
[0065]
【The invention's effect】
As described above, according to the present invention, an organic electrolyte secondary battery having a high capacity and high safety can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing one embodiment of an organic electrolyte secondary battery of the present invention.
[Explanation of symbols]
1 Positive electrode
2 Negative electrode
3 Separator
4 Organic electrolyte

Claims (1)

In an organic electrolyte secondary battery having a negative electrode and a positive electrode capable of inserting and extracting lithium ions by charge and discharge, and a lithium ion conductive organic electrolyte, the negative electrode active material is a metal of group 13 to group 15 in the periodic table or A lithium host compound capable of including at least one lithium ion selected from the group consisting of metalloid oxides, sulfides and nitrides, and a cyclic carbonate or carbonate multimer in the organic electrolyte. At least one of them and a phosphate triester , the mixing ratio of the phosphate triester to the cyclic carbonate and carbonate ester multimer is 99: 1 to 50:50 in volume ratio, The content of the organic solvent other than the phosphate triester, cyclic carbonate, and carbonate ester multimer in the entire constituent solvent of the organic electrolyte is 2 The organic electrolyte secondary battery according to volume percent or less, wherein the der Rukoto.

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