JP2787153B2 - Secondary battery and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery using an alkali metal, and more particularly to extending the life of a battery.

[0002]

2. Description of the Related Art A lithium secondary battery, which represents a high-energy non-aqueous electrolyte battery, has a negative electrode made of lithium metal or a lithium alloy or carbon capable of absorbing and releasing lithium ions, a positive electrode made of a transition metal oxide, A non-aqueous electrolyte in which a lithium salt is dissolved in the electrolyte is used. When the negative electrode is made of lithium metal or alloy, lithium is dissolved when the battery is discharged. In the case of a carbon negative electrode, lithium ions intercalated between carbon layers move to the solution phase. This is a reaction in which the positive electrode takes in the lithium ions released from the negative electrode. At the time of charging, the above-described reverse reaction proceeds by electric energy applied from an external power supply connected to the battery. Since the secondary battery operates at a high voltage of 3 to 4 V, a strong oxidizing atmosphere is provided on the positive electrode, and a strong reducing atmosphere is provided on the negative electrode.

[0003] Therefore, a non-aqueous electrolyte excellent in oxidation resistance and reduction resistance is essential. In particular, the electrochemical stability of the solvent, which is the main component of the electrolytic solution, is important. When the solvent is electrolytically oxidized at the positive electrode, the resistance between the electrodes increases, so that the battery capacity decreases or the inside of the battery decreases. Rupture of the battery container occurs due to gas generation.

[0004] Typical solvents used in lithium secondary batteries include propylene carbonate and ethylene carbonate.
And dimethoxycarbonate, and ether solvents such as 1,2-dimethoxyethane and 2-methyltetrahydrofuran. The former carbonate-based solvents have excellent oxidation resistance, and the oxidation potential of these solvents is 3.7 to 4 V based on lithium metal, and the latter is 3.2 to 3.5 V for the ether-based solvents (edited by the Battery Handbook Editing Committee). : Battery Handbook, p.324, 1990, Maruzen). On the other hand, the former reduction potential is 0.7
11 V, the latter having a reduction potential of 0.2-0.3 V. Such a solvent that is hardly oxidized is inferior in reduction resistance, and a solvent that is hardly reduced tends to have low oxidation resistance, and a solvent for a non-aqueous electrolyte having both excellent oxidation resistance and reduction resistance is Very few. Since the actual electrolyte of a lithium battery requires high electrical conductivity in addition to electrochemical stability,
A mixed non-aqueous solvent of a liquid having a high dielectric constant and a liquid having a low viscosity is used. For example, a mixed solvent of propylene carbonate and 1,2-dimethoxyethane (JP-A-58-214279) or a mixed solvent of ethylene carbonate and 2-methyltetrahydrofuran (JP-A-5-3115) ) Uses a non-aqueous electrolyte in which an electrolyte is dissolved. In the examples other than the above-mentioned solvents, by using a mixed solvent of 4-methyldioxolane and acetonitrile, a non-aqueous electrolyte having excellent oxidation resistance and reduction resistance has been obtained (Japanese Patent Laid-Open No. 4-206476). .

[0005]

The solvent for the non-aqueous electrolyte is
In order to obtain an electrolyte having not only excellent chemical stability but also high electrical conductivity, it is desirable that the electrolyte has a high dielectric constant and a low viscosity. However, developing a solvent that meets all these requirements is not easy in practice.

An object of the present invention is to provide a technique for reducing the rate of electrolytic oxidation reaction of a solvent for a non-aqueous electrolyte, and to provide a secondary battery having a longer battery life and improved safety.

[0007]

According to the present invention, in order to solve the above-mentioned problems, the rate of the electrolytic oxidation reaction of the solvent for the non-aqueous electrolyte depends on the catalytic activity of the positive electrode active material with respect to the oxidative decomposition of the solvent. And found that reducing the catalytic activity of the positive electrode active material can suppress the oxidative decomposition of the solvent for the non-aqueous electrolyte.

The positive electrode active material of the lithium secondary battery according to the present invention is a metal oxide such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and V ₂ O ₅ . When the electrolyte is oxidized on the positive electrode containing these active materials, first the solvent molecules are adsorbed on the positive electrode active material particles. At that time, an adsorption site for solvent molecules is required on the surface of the positive electrode active material particles. The adsorbed solvent molecules are
It is broken down into intramolecular bonds and recombination, and is further decomposed into products with the emission of electrons from the solvent molecules to the positive electrode active material. For example, as an example of a solvent used for a lithium secondary battery,
Propylene carbonate is present, but when it is oxidatively decomposed, carbon dioxide gas is generated. In general, since the solvent for nonaqueous electrolysis is a polyatomic molecule, when it is oxidatively decomposed, a plurality of adsorption sites adjacent to the surface of the positive electrode active material are required. If a part of the adsorption site group is blocked with a different metal element, the non-aqueous solvent molecules cannot be adsorbed and are hardly oxidized. Therefore, by adding an oxide or a metal having an oxidation catalytic activity lower than that of the above-described positive electrode active material to the surface of the positive electrode active material, the adsorption site of the solvent molecule is blocked, and the oxidative decomposition reaction of the solvent can be suppressed.

Examples of oxides or metals having low catalytic activity for oxidatively decomposing a solvent include I ₂ such as K ₂ O, CaO, Sc ₂ O ₃ and TiO _2.
oxides of a~IVa group element, or _{CuO, Au, B 2 O 3} , Al
There are oxides or metals of Group Ib to Vb elements such as ₂ O ₃ , SiO ₂ , and P ₂ O ₅ . When the raw material powder of the positive electrode active material is immersed in a dilute aqueous solution containing a nitrate, a chloride salt, an acid or the like containing these oxides or metals, the salt is adsorbed on the surface of the active material.
Examples of different element compounds used include Ca (NO ₃ ) ₂ , Sc (N
_{O 3) 3, Ti (NO} 3) 4, Cu (NO 3) 2, HAuCl 6, Al (NO 3) include _3, aqueous or non-aqueous solution containing 10 to ⁵ -10 to ¹ molar equivalent of the compound Is added to the positive electrode active material powder, and the mixture is sufficiently kneaded to adhere the heterogeneous element compound to the surface of the positive electrode active material powder. When this sample is subjected to a heat treatment in the air, the metal oxide is held in a highly dispersed state on the surface of the positive electrode active material powder. Ib
When an acid of group metal (Au) (HAuCl ₆ ) is used, firing in a vacuum or in hydrogen causes the surface of the positive electrode active material powder to have a Ib group metal.
(Au) particles are fixed. The firing temperature is desirably as low as possible, and the firing temperature is desirably 400 ° C. or lower using a compound which is easily decomposed at a low temperature such as a nitrate. When firing at a high temperature, metal ions attached to the surface of the active material diffuse into the active material, and the effect of modifying the surface of the active material may not be obtained.

As described above, by blocking a part of the adsorption site of the solvent molecule existing on the surface of the positive electrode active material particles with the foreign element, the adsorption of the solvent molecule is prevented and the decomposition reaction of the electrolytic solution can be suppressed. . The coverage of the oxide or metal of a different element fixed on the surface of the positive electrode active material particles is preferably about 0.1 to 30% with respect to the total surface area of the positive electrode active material particles. There is no effect on the suppression, and when it exceeds 30%, the diffusion of alkali metal ions near the surface of the positive electrode active material is inhibited, and the charge / discharge capacity of the positive electrode is reduced. The composite oxide thus obtained is mixed with a carbon powder and a binder to produce a positive electrode, which can be used for a lithium secondary battery.

The amount of the oxide or metal of a different element fixed on the surface of the positive electrode active material powder is 0.1 to 30% with respect to the specific surface area of the positive electrode active material powder. It does not actually hinder the charge / discharge reaction. By using the positive electrode active material in which the oxide or metal of the different element according to the present invention is fixed, a conventionally known electrolytic solution effective for the negative electrode, for example, ethylene carbonate, propylene carbonate, etc.
The oxidation resistance of carbonate, 1,2-dimethoxyethane and 2-methyltetrahydrofuran can be greatly improved.
The method of the present invention is applicable not only to lithium secondary batteries but also to non-aqueous electrolyte batteries in general, and is effective in extending the life of power sources for consumer use, distributed power storage, and electric vehicles.

[0012]

According to the present invention, by fixing an oxide or metal composed of a different element to a part of the surface of the positive electrode active material particles, the oxidative decomposition of the electrolyte is suppressed, and the life of the nonaqueous electrolyte battery is extended. Safety can be improved.

[0013]

【Example】

Embodiment 1 FIG. 1 is a view showing an AA size (AA) cylindrical lithium secondary battery used for specifically implementing the technique of the present invention. The cylindrical lithium secondary battery includes an electrode group 4 spirally wound with a separator 3 interposed between sheets of a positive electrode 1 and a negative electrode 2, and a metal battery housing the electrode group 4. The container 6, the nonaqueous electrolyte injected into the battery container 6 and entering the electrode group 4, the negative electrode lead wire 7 joined to the battery container 6, the positive electrode 1 and the positive electrode terminal 11 on the container lid 10. And a hole for passing the positive electrode lead wire 9 disposed on the polymer insulating sheet 5 and the electrode group 4 laid on the inner bottom of the battery container 6. And an insulating plate 8. Then, the container lid 10 and the battery container 6 were swaged to seal the entire container, thereby producing this battery.

The positive electrode 1 was prepared by mixing a positive electrode active material with a carbon powder and a binder, and pressing the mixture onto an aluminum foil as a current collector to form a sheet. The negative electrode 2 was prepared by mixing the negative electrode active material with a binder and pressing the mixture onto a copper foil as a current collector to form a sheet. The positive electrode active material is LiCo
O _2, and a LiCoO _2, 3 kinds of LiCoO ₂ with attached CaO with attached Al ₂ O ₃ described below, the negative electrode active material using graphite powder. Al ₂ O ₃ and CaO are examples of the low activity metal oxide of the present invention. The non-aqueous electrolyte is obtained by dissolving 1 mole equivalent of LiPF ₆ in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in equal volumes.
400mA rated discharge capacity when battery operating voltage is 2.5 to 4.2V
At h, the average output voltage was 3.5 V.

The powders of the three kinds of positive electrode active materials used in this example were synthesized by the following method. LiCo for the first positive electrode active material
The O ₂ powder was produced by thermally decomposing a mixture of CoCO ₃ and Li ₂ CO ₃ . Co ₃ O ₄ , LiOH instead of CoCO ₃ and Li ₂ CO ₃
Etc. can be used. A second cathode active material, Al ₂ O ₃ powder of LiCoO ₂ of deposition, Al (NO ₃₎ that was prepared in 5 × 10 ~ ² molar equivalent to LiCoO ₂ powder 10 g ₃ aqueous solution 20ml was added standing overnight After that, it was synthesized by heat treatment at 400 ° C. in the atmosphere. LiCoO with CaO as the third positive electrode active material
₂ is added to 10 g of LiCoO ₂ powder in the same manner as the second cathode material.
The solution was synthesized by adding 20 ml of a Ca (NO ₃ ) ₂ aqueous solution adjusted to a concentration of × 10 to ² mol, leaving it to stand all day and night, and then performing a heat treatment at 400 ° C. in the atmosphere. Each of the synthesized positive electrode active material powders was prepared by observing the AlCoO ₂ oxide particles on the surface of the LiCoO ₂ oxide particles by observation with a transmission electron microscope, measurement of a fine structure by wide area X-ray absorption, or electron beam microanalysis.
And Ca oxide were confirmed. The content of Al and Ca in the positive electrode active material powder was 0.01% in terms of a molar ratio with respect to LiCoO ₂ and 10% in terms of the surface coverage.

3 m above the container lid 10 of the battery shown in FIG.
A pore of mφ was opened, a stainless tube of 3 mmφ was connected to the pore, and a pressure sensor was attached to the stainless tube.
From the pressure change measured by this pressure sensor and the void volume inside the battery shown in FIG. 1, the volume of gas generated by decomposition of the electrolyte was estimated. FIG. 2 shows LiCoO ₂ , Al ₂ O ₃
The showing a LiCoO ₂ gas generation amount of the test results that occurred during the charge and discharge test of lithium secondary battery using each obtained by adding LiCoO ₂ and CaO were added. The test condition is that the battery voltage is 3
The battery was repeatedly charged and discharged at a constant current of 55 V and 200 mA. The gas generation amount was measured immediately after discharge in each cycle.
Gas generation amount, most often in the untreated cell using LiCoO ₂ in shown in curve (a), and LiCoO ₂ of Ca oxide deposition shown by curve (b), Al oxide shown by curve (c) LiCoO ₂ with adhesion
The amount of gas generated was significantly reduced in the battery using.

[0017] In addition to the carbon negative electrode used in this embodiment, even when using a negative electrode obtained by bonding a negative electrode plate of lithium metal, or a mixture of a lithium alloy powder and a binder on a current collector, CaO Ya Al ₂ O ₃ It was possible to reduce the amount of gas generated by the addition of. Further, the electrolytic solution to which the present invention can be applied is not limited to the electrolytic solution used in this example, and the electrolyte may be LiClO ₄ , CF ₃ SO ₃
Even when propylene carbonate, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, or the like was used as a solvent such as Li, the amount of generated gas was reduced as in the present example.

Example 2 Table 1 shows the types of the metal salt and acid of the fourth periodic element in the periodic table added to the powder of the positive electrode active material LiCoO ₂ , and the discharge capacity reduction rate of the battery having the same specifications as FIG. The relationship was shown.

[0019]

[Table 1]

The low active oxides studied in this example are K, C
a, Sc, Ti, Cu, Zn, B, Al, Si, each oxide of P,
The low activity metal is Au. These low-active substances were retained on the LiCoO ₂ surface according to the following procedure. First, KNO ₃ , Ca
(NO ₃ ) ₂ , Sc (NO ₃ ) ₃ , Cu (NO ₃ ) ₂ , Zn (ClO ₄ ) ₂ , Na ₃ BO ₃ , Al
An aqueous solution of (NO ₃ ) ₃ , H ₃ PO ₄ and an alcohol solution of TiCl ₄ and SiF ₄ are prepared. The solution containing the acid added to LiCoO ₂ is HA
It was an aqueous solution of lCl ₆ and the concentration of each solution was 5 × 10 to ² mol per liter of solvent. 20 ml of the above solution was added per 10 g of LiCoO ₂ powder, and the mixture was left overnight. Thereafter, the sample to which Au was added was heat-treated at 400 ° C. in vacuum, and the sample to which elements other than Au were added was heat-treated at 400 ° C. in air. Thus, oxides of Ca, Sc, Cu, B, Al, Ti, Si, or Au
Using each LiCoO ₂ positive active material was added, to prepare a lithium battery AA size having the same specifications and FIG. The operating voltage of the battery was 2.5 to 4.2 V, and the capacity of the battery was measured by charging and discharging at a constant current. The addition amounts shown in Table 1 are based on the number of moles of the Co element in the LiCoO ₂ powder, that is, the above elements, that is, K, Ca, Sc, Ti, and C.
It is a value in which the molar ratio of u, Zn, B, Al, Si, P, and Au is expressed in percentage. The discharge capacity at the first cycle and the capacity decrease rate are the discharge capacity at the first cycle when charging and discharging at a constant current of 100 mA in the battery voltage range of 3.0 to 4.5 V, respectively. Represents the ratio of the discharge capacity.

The battery using the respective LiCoO ₂ to which the oxides of Ca, Ti, B, Al, P, and Zn are added as the positive electrode active material has a discharge capacity in the first cycle of 392 to 400 mAh and a reduction rate of the discharge capacity. 0.03 ~
0.04%. In particular, when Al oxide was added to LiCoO ₂ , the initial discharge capacity was high and the discharge capacity reduction rate was small. The remarkable suppression effect of the addition of Al oxide on the reduction in the capacity of the battery is based on the suppression of the decomposition of the solvent in the electrolyte, as judged from the results of FIG. Oxides of Cu and Si,
When using each of LiCoO ₂ to which Au was added, the discharge capacity in the first cycle was 380 to 382 mAh, and the discharge capacity reduction rate was 0.06.
0.00.07%. The effect of suppressing the capacity decrease by adding K and Sc oxides was slight, and the discharge capacity decrease rate was 0.08%.

K, Ca, Sc, Ti, Cu, Z studied in this embodiment
n, B, Al, Si, the oxides of P, and out of the Au metal, a combination of several kinds of oxides or Au, be attached to LiCoO ₂ powder, the reduction capacity of the battery by oxidative decomposition of the electrolyte solution Could be suppressed.

[Embodiment 3] Al (NO ₃ ) ₃ was used in the same manner as in Embodiment 2.
A battery having the same specifications as in FIG. 1 was produced using the positive electrode active material produced by adding the powder to LiCoO ₂ powder. FIG. 3 shows the initial discharge capacity and the capacity reduction rate with respect to the amount of Al added. Initial discharge capacity and capacity reduction rate are 100m in the range of battery voltage 3.0 ~ 4.5 respectively
It shows the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle and the discharge capacity at the first cycle when the battery is charged and discharged at a constant current of A. The capacity reduction rate is 20 to
It decreased to 25% with the increase of Al addition. But Al
When the added amount exceeded 30%, the initial discharge capacity was significantly reduced, and conversely, the capacity reduction rate was increased. According to this example, by setting the amount of Al added to 30% or less, the rated discharge capacity of the battery was maintained, and it was possible to suppress a decrease in capacity.

Embodiment 4 V ₂ O ₅ , LiV ₃ O ₈ , LiNiO ₂ , LiMn
The capacity of a lithium secondary battery that uses a positive electrode active material in which Al and P oxides are added to four types of oxides of ₂ O ₄ is used, and a positive electrode active material that does not include Al and P oxides is used. Battery. The lithium secondary battery manufactured in this example is the AA size cylindrical battery shown in FIG. Each positive electrode active material was produced according to the following procedure. LiV ₃ O _{8 as a} raw material was synthesized by heat treatment of a mixture of LiOH and V ₂ O ₅ . Similarly, LiNiO ₂ , LiMn ₂ O ₄ is Ni (OH) ₃ or Mn
Lithium salts such as Li (OH) and LiNO ₃ were mixed with O ₂ and obtained by heat treatment. V ₂ O ₅ used a commercial product. V ₂ O ₅ , LiV ₃
Each oxide of O ₈ , LiNiO ₂ , and LiMn ₂ O ₄ is converted to Al (NO ₃ ) ₃
Alternatively, it was immersed in an aqueous solution in which H ₃ PO ₄ was dissolved all day and night.
The number of moles of Al and P present in these aqueous solutions is 1 to the number of moles of V, Ni, and Mn contained in the oxide powder to be immersed.
It was set to 0 ~ ⁴ . Then, heat to dry the oxide powder, heat-treat at 400 ° C., V ₂ O ₅ , LiV ₃ O ₈ , LiNiO ₂ , L
Al and P oxides were deposited on iMn ₂ O ₄ . X-ray photoelectron spectroscopy and X-ray diffraction analysis of the low-active oxide added to the raw material oxide revealed that Al oxide was a mixture of Al ₂ O ₃ and Al (OH) ₃ and P oxide was P It was confirmed to be ₂ O ₅ . Al and P
As a result of calculating the coverage of the oxide of V ₂ O ₅ , Li
V ₃ with respect to O _8, LiNiO _2, LiMn ₂ specific surface area of the O ₄ powder, 5-10
%Met.

The obtained positive electrode active material powder was mixed with a carbon powder and a binder, and the mixture was pressed on an aluminum foil to produce eight kinds of sheet-shaped positive electrodes for each active material.
Graphite powder was used as the negative electrode active material, and a mixture of the graphite powder and the binder was pressed on a copper foil to produce sheet-like electrodes 2 respectively. Between each of the electrodes 1 produced above and the sheet of the negative electrode 2, a separator 3 is interposed and wound,
Eight types of electrode groups 4 were produced. This wound electrode group 4
Was placed in a metallic battery container 6 having a polymer insulating sheet 5 laid on the bottom, and the negative electrode lead wire 7 was welded to the battery container 6.
Then, a non-aqueous electrolyte solution in which LiPF ₆ equivalent to 1 molar concentration was dissolved in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane at an equal volume ratio was injected into the inside of the battery container 6, and the wound electrode group 4 The insulating plate 8 was placed on the upper part, and the positive electrode lead wire 9 was connected to the positive electrode terminal 11 on the upper part of the container lid 10 through the hole in the center of the insulating plate 8. Finally, the battery lid 10 and the battery container 6 were swaged to seal the entire container, thereby producing a cylindrical battery. The operating voltage of a battery using V ₂ O ₅ and LiV ₃ O ₈ as raw material oxides is 2.
The operating voltage of the battery using LiNiO ₂ and LiMn ₂ O ₄ was 2.5 to 4.2 V. The capacity of each battery was measured by charging and discharging at a constant current.

Table 2 summarizes the discharge capacity at the first cycle and the rate of decrease in capacity of the eight batteries manufactured in this example.

[0027]

[Table 2]

In the case where the raw material oxides are V ₂ O ₅ and LiV ₃ O ₈ , when the P oxide is added rather than the Al oxide, the capacity reduction rate is remarkably reduced as compared with the non-added battery. Was. That is, P
The capacity reduction rate of the battery using the oxide-added V ₂ O ₅ was reduced by 0.4% from the value without the addition, and the capacity reduction rate of the battery using the LiV ₃ O ₈ with the P oxide was greater than the value without the addition. It decreased by about 1%.

In the case of LiNiO ₂ and LiMn ₂ O ₄ , the decrease in battery capacity was significantly suppressed when Al oxide was added. The capacity decrease rate of the battery using the Al oxide-added LiNiO ₂ is reduced by 0.05% from the value without the addition, and the capacity decrease rate of the battery using the Al oxide-added LiMn ₂ O ₄ is 0.08% from the value without the addition. % Has become smaller.

[0030]

According to the present invention, in the lithium secondary battery, the surface of the particles of the positive electrode active material, which is a lithium oxide, constituting the positive electrode is partially less active than the lithium oxide with respect to the nonaqueous electrolyte. K is a different element oxides, oxides of Ca Noi
By adhering the slippage, a decrease in the capacity of the nonaqueous electrolyte battery can be suppressed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a cylindrical lithium secondary battery according to one embodiment of the present invention.

FIG. 2 is a diagram showing a measurement result of an amount of gas generated inside a cylindrical lithium secondary battery during a charge / discharge cycle of the battery according to one embodiment.

FIG. 3 shows the initial discharge capacity to the amount of Al oxide added to LiCoO ₂ and the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle during the charge and discharge cycles of the cylindrical lithium secondary battery of the present invention. It is a figure showing the measurement result of.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Separator 3 Negative electrode 4 Electrode group 5 Insulating sheet 6 Battery container 7 Negative lead wire 8 Insulating plate 9 Positive lead wire 10 Container lid 11 Positive electrode terminal

Continued on the front page (72) Inventor Masanori Yoshikawa 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Mamoru Mizumoto 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor Tatsuo Horiba 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory (56) References JP-A-5-47383 (JP, A) JP-A-3-119656 (JP, A) JP-A-7-307150 (JP, A) JP-A-4-329267 (JP, A) JP-A-4-328258 (JP, A) JP-A-1-304660 (JP, A) JP, A) JP-A-6-150928 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 10/40 H01M 4/02-4/04 H01M 4/58

Claims (4)

(57) [Claims] 1. A non-aqueous electrolyte, a negative electrode containing lithium metal or an alloy containing lithium metal or an intercalation compound of lithium metal ions, and a positive electrode active for electrochemically absorbing and releasing lithium metal ions. secondary battery, wherein K is a part of the grain surface of the material, a positive electrode or to the distributed retention of the oxides of Ca, in that it consists of. 2. The secondary battery according to claim 1, wherein one of the oxides of K and Ca occupies 0.1 to 30% of the total surface area of the positive electrode active material. 3. The secondary battery according to claim 1, wherein the positive electrode active material includes at least one of V, Mn, Co, and Ni. 4. A non-aqueous electrolyte, a negative electrode containing lithium metal or an alloy containing lithium metal or an intercalation compound of lithium metal ion, and a positive electrode active for electrochemically absorbing and releasing lithium metal ions. In a method for manufacturing a secondary battery comprising a positive electrode containing a substance,
The cathode material is brought into contact with an aqueous solution of potassium nitrate, then mosquitoes in a part of the positive electrode active material surface by heat treatment
A step of dispersing and holding the oxide of lithium (K) , or
The cathode material is brought into contact with an aqueous solution of calcium nitrate ,
Thereafter, a step of dispersing and holding an oxide of calcium (Ca) on a part of the surface of the positive electrode active material by heat treatment is included.
A method for producing a secondary battery .