JPH1021912A - Manufacture of nonaqueous electrolyte secondary battery and its positive electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery where high temperature preservation property is improved. SOLUTION: In a nonaqueous electrolyte secondary battery possessing a chargeable and dischargeable positive electrode, a nonaqueous electrolyte, and a chargeable and dischargeable negative electrode, the positive electrode contains the carbon material which includes at least one kind of element (but, in case that it contains two or more kinds, 35wt.% in total is the limit) being selected from the group consisting of 0.5-19wt.% nitrogen, 0.5-35wt.% sulfur, and 0.5-25wt.% oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly, to an improvement in a positive electrode thereof.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries using lithium or a lithium compound as a negative electrode are expected to have a high voltage and a high energy density, and are being actively studied. As a negative electrode, a carbon material such as graphite, which forms an intercalation compound with lithium, has been put to practical use because of its smaller cycle capacity but superior cycle characteristics as compared with metallic lithium or alloy negative electrodes. On the other hand, as the active material of the positive electrode, MnO ₂ and TiS ₂ have been well studied. These positive electrode active materials have a potential of about 3 V with respect to lithium. Recently, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li
MnO _2, LiFeO cathode active material showing a 4V potential close the lithium such as ₂ also actively studied have been made already Li
Batteries using CoO ₂ for the positive electrode have been put to practical use. That is, as a means for obtaining a high energy density of a battery, efforts are being made to increase the battery voltage as well as the capacity.

[0003]

When the above-mentioned positive electrode active material is used, the battery voltage and the capacity are increased, so that the energy density of the battery can be increased. However, when the charging voltage is 3
Since the voltage may exceed V or exceed 4 V in some cases, there is a problem in storage characteristics especially at high temperature after charging. One of the causes of self-discharge after charging at a high temperature of a nonaqueous electrolyte secondary battery or a subsequent decrease in capacity is an increase in internal resistance of the battery due to decomposition of an electrolyte solution or the like on a positive electrode active material. In particular, the operating temperature range of the battery is required to be as high as possible, and it is desired to improve the storage characteristics in a higher temperature state. An object of the present invention is to solve such problems and to provide a positive electrode that provides a non-aqueous electrolyte secondary battery having high energy density and excellent storage characteristics.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a non-aqueous electrolyte secondary battery having a chargeable / dischargeable positive electrode, a nonaqueous electrolyte, and a chargeable / dischargeable negative electrode.
t% nitrogen, 0.5-35 wt% sulfur and 0.5-35 wt%
It is characterized by containing a carbon material containing at least one element selected from the group consisting of 25 wt% oxygen (however, when two or more kinds are contained, the total is up to 35 wt%). With this configuration, the decomposition reaction of the electrolytic solution on the positive electrode active material at a high temperature is suppressed, and the adverse effect on the high-temperature storage characteristics can be substantially eliminated.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The positive electrode of the present invention has a thickness of 0.5 to 19 watts.
t% nitrogen, 0.5-35 wt% sulfur and 0.5-35 wt%
A carbon material containing at least one element selected from the group consisting of 25 wt% oxygen (however, if two or more elements are contained, the total is up to 35 wt%);
In one embodiment, these carbon materials are mixed in the positive electrode mixture. In another aspect, at least a part of the surface of the active material of the positive electrode includes 0.5 to 19 wt% of nitrogen,
Contains at least one element selected from the group consisting of 0.5 to 35 wt% sulfur and 0.5 to 25 wt% oxygen (however, when two or more elements are included, 35 wt%
) Carbon material layer. In an embodiment in which the carbon material is contained in at least a part of the positive electrode active material surface layer,
Even if the carbon material does not contain nitrogen, sulfur or oxygen elements, the effect of improving high-temperature storage characteristics can be obtained. The content of the carbon material in the positive electrode is equivalent to 1 to 15 wt% of the positive electrode active material, particularly preferably 3 to 15 wt%.

According to the method of manufacturing a positive electrode for a non-aqueous electrolyte secondary battery of the present invention, an organic material containing at least one element selected from the group consisting of nitrogen, sulfur and oxygen is added to a positive electrode active material, The organic material is carbonized by heating in an atmosphere, and a carbon material layer containing at least one element selected from the group consisting of nitrogen, sulfur and oxygen is formed on the surface layer of the positive electrode active material. Another method for producing a positive electrode for a non-aqueous electrolyte secondary battery of the present invention is a step of adding an organic substance or an organic substance containing at least one element selected from the group consisting of nitrogen, sulfur and oxygen to the positive electrode active material, Forming a positive electrode active material to which the organic substance is added on the surface of the positive electrode current collector; and heating the organic substance in an inert atmosphere to carbonize the organic substance. The organic material containing at least one element selected from the group consisting of nitrogen, sulfur and oxygen used in these production methods has a nitrogen, sulfur, or oxygen content after carbonization in the above range. Are preferred.

The positive electrode active material used in the present invention is Li
Mn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNiO ₂ ,
And those selected from the group consisting of LiFeO ₂ . As the organic substance used as the raw material of the carbon material, a cyclic compound such as pitch, coal tar, benzene, naphthalene, anthracene or the like, or a derivative or polymer thereof is preferable. Examples of the organic substance containing nitrogen include cyclic compounds such as aniline and polyaniline, derivatives and polymers thereof, and pyrrole.
Heterocyclic compounds containing a nitrogen atom such as polypyrrole, piperazine, pyrazine, pyrazole, triazine, triazole, quinoline, tetrahydroquinoline, melamine, derivatives and polymers thereof are preferred. Further, dimethylformamide or acetonitrile, acrylonitrile, propionitrile, butyronitrile, chain-type nitrile represented by pentanonitrile, derivatives thereof,
Further, a chain compound containing a nitrogen atom such as polyacrylonitrile or a copolymer thereof is preferable.

As organic substances containing sulfur, thiophene,
Tetrahydrothiophene, polythiophene, thiane, dithiane, trithiane, thiophthene, benzothiophene,
Heterocyclic compounds containing a sulfur atom such as thianthrene, derivatives or polymers thereof are preferred. Further, methanethiol, ethanethiol, propanethiol, butanethiol, hexanethiol, heptanethiol, ethanedithiol, propanedithiol, dimethylsulfide, diethylsulfide, dipropylsulfide, dimethyldisulfide, diethyldisulfide, dipropyldisulfide, derivatives thereof or A chain compound containing a sulfur atom such as a polymer is preferred.

Examples of the organic substance containing oxygen include furan, polyfuran, tetrahydrofuran, pyran, dioxane, trioxane, dioxolan, oxolan, benzofuran, butyrolactone, chromene, chroman, benzoquinone, naphthol, naphthoquinone, phenol, phenolic resin, and derivatives or polyphenols thereof. Cyclic compounds containing an oxygen atom such as coalescence are preferred. Polyethers such as polyethylene oxide and polypropylene oxide; polyesters such as polyethylene terephthalate, alkyd resin and maleic acid resin; polymers and copolymers such as polyvinyl alcohol; and alcohols such as ethyl alcohol, acetaldehyde and the like. Preferred are chain compounds containing an oxygen atom such as aldehydes and carboxylic acids such as acetic acid.

[0010]

Embodiments of the present invention will be described below. Example 1 In this example, the amount of the carbon material containing nitrogen was examined. LiMn ₂ O _{4 as} the positive electrode active material,
LiMnO ₂ , LiCoO ₂ , LiNiO ₂ , or Li
FeO ₂ was used, and a carbon material having a nitrogen content of 5 wt% obtained by heating polyacrylonitrile was used. 4.0 g of a polyfluoroethylene resin as a binder and a carbon material having a nitrogen content of 5 wt% were mixed with 100 g of the positive electrode active material in amounts shown in Table 1 to prepare a positive electrode mixture. Table 1
, The addition amount of the carbon material is 100 wt.
% (The same applies to the following tables). 0.1 g of this positive electrode mixture was press-molded at a pressure of 1 ton / cm ² into a disk having a diameter of 17.5 mm to obtain a positive electrode. The positive electrode 1 is placed in a stainless steel case 2, a separator 3 made of a microporous polypropylene film is placed thereon, and after injecting an electrolytic solution, a diameter of 17.
A negative electrode lithium plate 4 having a thickness of 5 mm and a thickness of 0.3 mm was adhered, and sealed with a sealing plate 6 having a polypropylene gasket 5 attached to the outer periphery to obtain a test battery. In addition, a mixed solution of ethylene carbonate and diethylene carbonate in a volume ratio of 1: 1 in which 1 mol / l of lithium perchlorate (LiClO ₄ ) was dissolved was used as the electrolytic solution. For comparison, a positive electrode using acetylene black as a carbon material containing no nitrogen was produced, and a similar battery was assembled.

A high temperature storage test was performed on these batteries. That is, at 20 ° C., at a constant current of 1 mA, L
A battery using iCoO ₂ or LiNiO ₂ as a positive electrode active material has a capacity of up to 4.2 V to LiMn ₂ O ₄ , LiMnO ₂ , or L
The battery using iFeO ₂ as a positive electrode active material was charged to 4.5 V, and then charged and discharged to 3 V repeatedly for 10 cycles. Next, after the completion of the charging in the eleventh cycle, 8
Stored at 0 ° C. for one month. After this storage, the atmosphere was returned to the temperature of 20 ° C., and discharge was performed under the same conditions as above. Here, the capacity retention rate was defined as follows. Capacity retention rate = [discharged electricity amount at 100 × 11th cycle]
/ [Discharged electricity amount at 10th cycle] Further, after the storage was completed, charging was performed, and the subsequent discharge capacity was evaluated. Here, the capacity recovery rate was defined as follows. Capacity recovery rate = [discharged electricity amount at 100 × 12th cycle]
/ [Discharged electricity amount at 10th cycle] Table 1 shows the capacity retention rate and capacity recovery rate of each battery obtained as described above after one month of storage. Table 2 shows the results of comparative examples using acetylene black as the carbon material.

[0012]

[Table 1]

[0013]

[Table 2]

A battery using acetylene black containing no nitrogen can be used with any of the positive electrode active materials.
Storing at 0 ° C. for 1 month showed a very large capacity loss. On the other hand, in a battery using a carbon material containing nitrogen, up to 15 wt% of the active material, the higher the amount of addition, the higher the capacity retention ratio and the capacity recovery ratio. Since the battery capacity decreases as the addition amount increases, the addition amount is preferably equivalent to 1 to 15 wt% of the positive electrode active material.

Example 2 In this example, the nitrogen content of a carbon material containing nitrogen was examined. LiMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNi
O ₂ or LiFeO ₂ , and the carbon material obtained by heating polyacrylonitrile has a nitrogen content of 0.1 to 25 watts.
Each of t% was used. In 100 g of the positive electrode active material,
4.0 g of a polyfluoroethylene resin as a binder and 5.0 g of carbon materials having different nitrogen contents shown in Table 3 were mixed to prepare a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Table 3 shows the capacity maintenance rate and capacity recovery rate of each battery after one month of storage.

[0016]

[Table 3]

In a battery using a carbon material containing nitrogen,
Even when stored at 80 ° C. for one month, the capacity retention rate and the capacity recovery rate are high, and particularly when the nitrogen content is in the range of 0.5 to 19 wt%, the capacity retention rate is 70% or more, and the capacity recovery rate is 78%.
That was all. By including the carbon material containing nitrogen in the positive electrode as described above, an effect of suppressing a decrease in capacity due to high-temperature storage can be obtained.

Example 3 In this example, the amount of sulfur-containing carbon material added was examined. L for the positive electrode active material
iMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNi
O ₂ or LiFeO ₂ was used, and a carbon material having a sulfur content of 7 wt% obtained by heating polythiophene was used. 4.0 g of a polyfluoroethylene resin as a binder and a carbon material having a sulfur content of 7 wt% were mixed with 100 g of the positive electrode active material in amounts shown in Table 3 to obtain a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Table 4 shows the capacity maintenance rate and capacity recovery rate of each battery after one month of storage.

[0019]

[Table 4]

A battery using acetylene black containing no sulfur can be used in any of the positive electrode active materials.
Storing at 0 ° C. for 1 month showed a very large capacity loss. On the other hand, in the battery using the carbon material containing sulfur, the capacity retention ratio and the capacity recovery ratio increased as the addition amount increased up to 15 wt% of the positive electrode active material. Since the battery capacity decreases as the addition amount increases, the addition amount is preferably equivalent to 1 to 15 wt% of the positive electrode active material.

Example 4 In this example, the sulfur content of a carbon material containing sulfur was examined. LiMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNi
O ₂ or LiFeO ₂ was used, and a carbon material having a sulfur content of 0.1 to 37 wt% obtained by heating polythiophene was used. To 100 g of the positive electrode active material, 4.0 g of a polyfluoroethylene resin as a binder and 5.0 g of carbon materials having different sulfur contents shown in Table 5 were mixed to prepare a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Table 5 shows the capacity retention rate and capacity recovery rate of each battery after one month of storage.

[0022]

[Table 5]

In a battery using a carbon material containing sulfur,
Even when stored at 80 ° C. for one month, the capacity retention rate and the capacity recovery rate are high, especially when the nitrogen content is in the range of 0.5 to 35 wt%, the capacity retention rate is 65% or more, and the capacity recovery rate is 75%.
That was all. By including a carbon material containing sulfur in the positive electrode as described above, an effect of suppressing a decrease in capacity due to high-temperature storage can be obtained.

Example 5 In this example, the amount of the carbon material containing oxygen was examined. L for the positive electrode active material
iMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNi
O ₂ or LiFeO ₂ was used, and a carbon material having an oxygen content of 4 wt% obtained by heating polyethylene oxide was used as the carbon material. 4.0 g of a polyfluoroethylene resin as a binder and a carbon material having an oxygen content of 4 wt% were mixed with 100 g of the positive electrode active material in amounts shown in Table 6 to prepare a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Table 6 shows the storage 1 for each battery.
The capacity maintenance rate after a month and the capacity recovery rate are shown.

[0025]

[Table 6]

A battery using acetylene black containing no oxygen can be used with any of the positive electrode active materials.
Storing at 0 ° C. for 1 month showed a very large capacity loss. On the other hand, in the battery using the carbon material containing oxygen, up to 15 wt% of the positive electrode active material, the capacity retention ratio and the capacity recovery ratio increased as the addition amount increased. Since the battery capacity decreases as the addition amount increases, the addition amount is preferably equivalent to 1 to 15 wt% of the positive electrode active material.

Example 6 In this example, the oxygen content of an oxygen-containing carbon material was examined. LiMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ , LiNi
O ₂ or LiFeO ₂ , and the carbon material obtained by heating polyethylene oxide has an oxygen content of 0.1 to 28.
wt% of each was used. 100 g of positive electrode active material
Was mixed with 4.0 g of a polyfluoroethylene resin as a binder and 5.0 g of a carbon material having a different oxygen content shown in Table 7,
A positive electrode mixture was used. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. Example 1
A high-temperature storage test was performed in the same manner as described above. Table 7 shows the capacity retention rate and capacity recovery rate of each battery after one month of storage.

[0028]

[Table 7]

In a battery using a carbon material containing oxygen,
Even when stored at 80 ° C. for one month, the capacity retention rate and the capacity recovery rate are high, and particularly when the oxygen content is in the range of 0.5 to 25 wt%, the capacity retention rate is 65% or more, and the capacity recovery rate is 75%.
That was all. By including the carbon material containing oxygen in the positive electrode as described above, an effect of suppressing a decrease in capacity due to high-temperature storage can be obtained.

Embodiment 7 In this embodiment, a positive electrode using an active material provided with a carbon material layer on a surface layer will be described. LiMn ₂ O ₄ , LiMnO ₂ , LiCo
O ₂ , LiNiO ₂ , or LiFeO ₂ was used. In addition, pitch or benzene polymer polyparaphenylene was used as the organic material forming the carbon material layer. The positive electrode active material provided with the carbon material layer on the surface layer was produced as follows.
First, a predetermined amount of pitch dispersed in quinoline or polyparaphenylene dispersed or dissolved in dimethylformamide was mixed with a positive electrode active material and dried. After crushing this, it is heated at 800 ° C. in a nitrogen atmosphere,
As shown in Tables 8 and 9, a positive electrode active material was obtained in which the amount of the carbon material layer was equivalent to 0.5, 1, 5, 10, or 15 wt% of the active material. 4.0 g of a polyfluoroethylene resin as a binder was mixed with 100 g of the above positive electrode active material to prepare a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Tables 8 and 9 show the capacity retention rate and capacity recovery rate of each battery after one month of storage.

[0031]

[Table 8]

[0032]

[Table 9]

The batteries using a positive electrode having a carbon material layer provided on the surface layer of the positive electrode active material all had a higher capacity retention ratio than the batteries containing only acetylene black in the positive electrode shown in the comparative example of Example 1. And the capacity recovery rate was higher. The effect was recognized in either graphitizable carbon obtained by heating the pitch or in non-graphitizable carbon obtained by heating the polyparaphenylene, and the high-temperature storage characteristics could be improved.

Embodiment 8 In this embodiment, a positive electrode in which a carbon material layer containing nitrogen is provided on a surface layer of a positive electrode active material will be described. LiMn ₂ O ₄ , LiMn
O ₂ , LiCoO ₂ , LiNiO ₂ , or LiFeO ₂ was used. A predetermined amount of polyacrylonitrile or polyaniline dispersed or dissolved in dimethylformamide was mixed with the positive electrode active material and dried. After pulverization, the mixture was heated to 600 to 1100 ° C. in a nitrogen atmosphere, and as shown in Tables 10, 11, and 12, the amount of the carbon material layers having different nitrogen contents was 1, 5, or 15 wt. % Of a positive electrode active material was obtained. 4.0 g of a polyfluoroethylene resin as a binder was added to and mixed with 100 g of the above-mentioned positive electrode active material to prepare a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Table 10, Table 11,
And Table 12 shows the capacity retention rate of each battery after one month of storage,
And the capacity recovery rate.

[0035]

[Table 10]

[0036]

[Table 11]

[0037]

[Table 12]

The battery using the positive electrode in which the nitrogen-containing carbon material layer is provided on the surface layer of the positive electrode active material is the same as the battery using the positive electrode obtained by simply mixing the carbon material containing nitrogen shown in Examples 1 and 2. In comparison, the capacity retention rate and the capacity recovery rate were further increased, which was effective in improving the high-temperature storage characteristics.

Embodiment 9 In this embodiment, a positive electrode in which a carbon material layer containing sulfur is provided on a surface layer of a positive electrode active material will be described. LiMn ₂ O ₄ , LiMn
O ₂ , LiCoO ₂ , LiNiO ₂ , or LiFeO ₂ was used. A predetermined amount of the thiophene polymer dispersed or dissolved in dimethylformamide was mixed with the positive electrode active material and dried. After pulverizing this, in a nitrogen atmosphere,
When heated to 1100 ° C., the amount of the carbon material layers having different sulfur contents as shown in Tables 13, 14, and 15 was changed to 1, 5,
Alternatively, a cathode active material equivalent to 15 wt% was obtained. 4.0 g of a polyfluoroethylene resin as a binder was mixed with 100 g of the above positive electrode active material to prepare a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Tables 13, 14 and 15 show the storage 1 of each battery.
The capacity maintenance rate after a month and the capacity recovery rate are shown.

[0040]

[Table 13]

[0041]

[Table 14]

[0042]

[Table 15]

The battery using the positive electrode provided with the carbon material layer containing sulfur on the surface layer of the active material is different from the battery using the positive electrode containing only the carbon material containing sulfur simply shown in Examples 3 and 4. As a result, the capacity retention rate and the capacity recovery rate were further increased, which was effective in improving the high-temperature storage characteristics.

Embodiment 10 In this embodiment, a positive electrode in which a carbon material layer containing oxygen is provided on a surface layer of a positive electrode active material will be described. LiMn ₂ O ₄ , LiMnO
₂ , LiCoO ₂ , LiNiO ₂ , or LiFeO ₂ was used. A predetermined amount of a furan polymer dispersed or dissolved in dimethylformamide was mixed with the positive electrode active material and dried. After pulverization, 600 to 11 in a nitrogen atmosphere.
By heating to 00 ° C., as shown in Tables 16, 17, and 18, a positive electrode active material was obtained in which the amount of carbon material layers having different oxygen contents was equivalent to 1, 5, or 15 wt% of the active material. 4.0 g of a polyfluoroethylene resin as a binder was added to 100 g of the above positive electrode active material.
Were mixed to obtain a positive electrode mixture. Using this positive electrode mixture, a positive electrode was produced in the same manner as in Example 1, and a battery was assembled. A high-temperature storage test was performed in the same manner as in Example 1. Tables 16, 17, and 18 show the capacity retention rate and capacity recovery rate of each battery after one month of storage.

[0045]

[Table 16]

[0046]

[Table 17]

[0047]

[Table 18]

The battery using the positive electrode provided with the carbon material layer containing oxygen on the surface layer of the active material is different from the battery using the positive electrode containing only the carbon material containing oxygen shown in Examples 5 and 6. As a result, the capacity retention rate and the capacity recovery rate were further increased, and the high temperature storage characteristics were effective.

Example 11 In this example, a step of forming a positive electrode active material mixed with an organic substance which is carbonized by heating on the surface of a current collector, and heating the same in an inert atmosphere to remove the organic substance A method for producing a positive electrode having a carbonization step was studied. LiMn ₂ O ₄ ,
LiMnO ₂ , LiCoO ₂ , LiNiO ₂ , or Li
FeO ₂ was used. The positive electrode was produced as follows. First, a predetermined amount of the pitch dispersed or dissolved in quinoline was mixed with the positive electrode active material, and the mixture was applied on a titanium core material, and then dried at 110 ° C. Also,
A predetermined amount of polyparaphenylene dispersed or dissolved in dimethylformamide was mixed with the positive electrode active material, and the mixture was applied on a titanium core material, and then dried at 110 ° C. The electrode plate coated with the active material mixed with the organic substance was heated to 700 ° C. in a nitrogen gas stream to obtain a positive electrode plate having a carbon material layer equivalent to 5 or 10 wt% of the active material.

The positive electrode plate 11 and the negative electrode plate 12 made of lithium foil were spirally wound via a separator 13 made of a microporous polypropylene film to form an electrode group. The electrode group is provided with insulating plates 16 and 17 made of polypropylene on its upper and lower sides, respectively, and inserted into a battery case 18.
After forming a step on the top of 8, a non-aqueous electrolyte
A mixed solution of ethylene carbonate and diethylene carbonate at a volume ratio of 1: 1 in which mol / l lithium perchlorate was dissolved was injected and sealed with a sealing plate 19 having a positive electrode terminal 20 to form a cylindrical battery. The positive electrode lead 14 connected to the positive electrode core is connected to the positive electrode terminal 20, and the negative electrode lead 15 connected to the negative electrode core is connected to the bottom of the battery case. In this battery, the electric capacity of the negative electrode is larger, and the capacity of the battery is determined by the capacity of the positive electrode.

A high-temperature storage test was performed on these batteries. That is, at 20 ° C., at a constant current of 0.5 mA / cm ² , a battery using LiCoO ₂ or LiNiO ₂ as a positive electrode active material has a LiMn ₂ O ₄ , LiMnO ₂ up to 4.2 V.
₂ or LiFeO ₂ as a positive electrode active material is 4.5.
Each charge to V and then discharge to 3 V was repeated 10 cycles. Next, after completion of the eleventh charge, the battery was stored at 80 ° C. for one month. 20 after this storage
The temperature was returned to an atmosphere of ° C., and discharge was performed under the same conditions as above. Here, the capacity retention rate was defined as follows. Capacity retention rate = [discharged electricity amount at 100 × 11th cycle]
/ [Discharged electricity amount at 10th cycle] Further, after the storage was completed, charging was performed, and the subsequent discharge capacity was evaluated. Here, the capacity recovery rate was defined as follows. Capacity recovery rate = [discharged electricity amount at 100 × 12th cycle]
/ [Discharged electricity amount at 10th cycle] The capacity retention rate and capacity recovery after one month of storage of each battery determined as described above are shown in Table 19 for the case where pitch was used as the organic substance, and as polycrystalline for the organic substance. Table 20 shows the case where paraphenylene was used.

[0052]

[Table 19]

[0053]

[Table 20]

Also in the battery of this example, the capacity retention rate and the capacity recovery rate were higher than those of the battery obtained by simply mixing acetylene black in the positive electrode shown in the comparative example of Example 1. The effect was recognized in both the graphitizable carbon obtained by heating the pitch and the non-graphitizable carbon obtained by heating the polyparaphenylene, and the high-temperature storage characteristics could be improved.

Example 12 In this example, a step of forming a positive electrode active material mixed with a nitrogen-containing organic substance on the surface of a current collector, and heating the same in an inert atmosphere to convert the organic substance to carbon A method for manufacturing a positive electrode having a process of forming a positive electrode was studied. LiMn ₂ O ₄ , LiM
nO ₂ , LiCoO ₂ , LiNiO ₂ , or LiFeO ₂
Was used. A predetermined amount of polyacrylonitrile or polyaniline dispersed or dissolved in dimethylformamide was mixed with the above positive electrode active material, and this mixture was applied on a titanium core material, and then dried at 110 ° C. This electrode plate was heated to 700 ° C. in a nitrogen gas stream to obtain a positive electrode plate containing a carbon material having a nitrogen content of 19 wt% corresponding to 5 or 10 wt% of the active material. A cylindrical battery was manufactured in the same manner as in Example 11, and a high-temperature storage test was performed. Table 21 shows the capacity maintenance rate and capacity recovery rate of each battery after one month.

[0056]

[Table 21]

Also in the battery of this embodiment, the capacity retention ratio and the capacity recovery ratio are higher than those of the battery using the positive electrode in which the carbon material containing only nitrogen is mixed as shown in Embodiment 2, and the high-temperature storage characteristics are obtained. Was effective in improving

Example 13 In this example, a method of manufacturing a positive electrode similar to that of Example 11 was studied using an organic substance containing sulfur as an organic substance to be mixed in advance with the positive electrode active material. A predetermined amount of a thiophene polymer dispersed or dissolved in dimethylformamide is mixed with a positive electrode active material, and the mixture is applied on a titanium core material.
Dried at 10 ° C. This electrode plate was heated to 700 ° C. in a nitrogen gas stream to obtain a positive electrode plate containing a carbon material having a sulfur content of 25 wt% corresponding to 5 or 10 wt% of the active material.
A cylindrical battery was manufactured in the same manner as in Example 11, and a high-temperature storage test was performed. Table 22 shows the capacity maintenance rate and capacity recovery rate of each battery after one month.

[0059]

[Table 22]

Also in the battery of this embodiment, the capacity retention rate and the capacity recovery rate are higher than those of the battery using the positive electrode in which the carbon material containing only sulfur shown in Example 4 is mixed, and the high-temperature storage characteristics are obtained. Was effective in improving

Example 14 In this example, a method of manufacturing a positive electrode similar to that of Example 11 was examined using an organic substance containing oxygen as an organic substance to be mixed in advance with the positive electrode active material. A predetermined amount of a furan polymer dispersed or dissolved in dimethylformamide is mixed with a positive electrode active material, and the mixture is applied on a titanium core material.
Dry at ℃. This electrode plate is placed in a nitrogen gas flow for 7 minutes.
By heating to 00 ° C., a positive electrode plate containing a carbon material having an oxygen content of 15 wt% corresponding to 5 or 10 wt% of the active material was obtained. A cylindrical battery was manufactured in the same manner as in Example 11, and a high-temperature storage test was performed. Table 23 shows the capacity retention rate of each battery after one month,
And the capacity recovery rate.

[0062]

[Table 23]

Also in the battery of this embodiment, the capacity retention ratio and the capacity recovery ratio are higher than those of the battery using the positive electrode in which the carbon material containing only oxygen is mixed as shown in Embodiment 6, and the high-temperature storage characteristics are obtained. Was effective in improving

In the above embodiment, 1 mol / mol of the electrolytic solution was used.
1 of lithium perchlorate dissolved in ethylene carbonate and diethylene carbonate at a volume ratio of 1: 1 was used, but this type of non-aqueous electrolyte secondary battery is known as an electrolyte, and the solute is hexafluorophosphoric acid. Lithium, lithium trifluoromethanesulfonate, lithium borofluoride, solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, etc .; esters such as gamma-butyrolactone, methyl acetate; ethers such as dimethoxyethane and tetrahydrofuran The same effect can be obtained in an electrolytic solution using a single or mixed solvent of the above.

[0065]

As described above, according to the present invention, a non-aqueous electrolyte secondary battery having high energy density and excellent high-temperature storage characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a coin-type battery used in an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a cylindrical battery used in another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Case 3 Separator 4 Negative electrode 5 Gasket 6 Sealing plate 11 Positive electrode 12 Negative electrode 13 Separator 14 Positive lead plate 15 Negative lead plate 16 Upper insulating plate 17 Lower insulating plate 18 Battery case 19 Sealing plate 20 Positive terminal

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toyoguchi ▲ Yoshi ▼ Toku 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A chargeable / dischargeable positive electrode, a non-aqueous electrolyte, and a chargeable / dischargeable negative electrode, wherein the positive electrode is 0.5 to 19
wt% nitrogen, 0.5-35 wt% sulfur and 0.5 wt%
A non-aqueous electrolyte characterized by containing a carbon material containing at least one element selected from the group consisting of oxygen in an amount of up to 25 wt% (however, when two or more kinds are contained, the total is limited to 35 wt%). Rechargeable battery. 2. A chargeable / dischargeable positive electrode, a non-aqueous electrolyte, and a chargeable / dischargeable negative electrode, wherein at least a part of the active material surface layer of the positive electrode is a carbon material layer or 0.5 to 19 wt%.
Nitrogen, 0.5-35 wt% sulfur and 0.5-25
contains at least one element selected from the group consisting of wt.% oxygen (however, when two or more are contained,
A non-aqueous electrolyte secondary battery comprising a carbon material layer. 3. The cathode active material is LiMn ₂ O ₄ or LiMnO.
_2, LiCoO _2, LiNiO _2, and at least one non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein selected from the group consisting of LiFeO _2. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the carbon material in the positive electrode is equivalent to 1 to 15 wt% of the positive electrode active material. 5. An organic material containing at least one element selected from the group consisting of nitrogen, sulfur and oxygen is added to a positive electrode active material, and then heated under an inert atmosphere to carbonize the organic material. A method for producing a positive electrode for a non-aqueous electrolyte secondary battery. 6. A step of adding an organic substance or an organic substance containing at least one element selected from the group consisting of nitrogen, sulfur and oxygen to a positive electrode active material, and collecting the positive electrode active material to which the organic substance is added into a positive electrode current collector. Forming on the body surface,
And a step of heating in an inert atmosphere to carbonize the organic substance, the method for producing a positive electrode for a non-aqueous electrolyte secondary battery.