JP2002033102A - Secondary power source and method for manufacturing negative electrode for secondary power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary power source having a high breakdown voltage, high capacity, high energy density, and high charging-discharging cycle reliability. SOLUTION: This secondary power source has a positive electrode containing activated carbon, a negative electrode containing carbon capable of storing and releasing lithium ions, and an organic electrolyte containing lithium ions. In this case, the carbon contained in the negative electrode contains boron in its hexagonal net surface structure, and the spacing of its surface [002] measured by an X-ray diffraction method is 0.337-0.410 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary power supply having a high withstand voltage, a large capacity, and a high reliability of a rapid charge / discharge cycle, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Polarizable electrodes mainly composed of activated carbon are used for both positive and negative electrodes of conventional electric double layer capacitors. The withstand voltage of the electric double layer capacitor is 1.2 V when an aqueous electrolyte is used, and 2.5 to 3.3 V when an organic electrolyte is used. Since the energy of the electric double layer capacitor is proportional to the square of the withstand voltage, the organic electrolyte having a higher withstand voltage has higher energy than the aqueous electrolyte. However, even an electric double layer capacitor using an organic electrolyte has an energy density of 1/10 or less of that of a secondary battery such as a lead storage battery, and further improvement in energy density is required.

On the other hand, Japanese Patent Application Laid-Open No. 64-14882 discloses that an electrode mainly composed of activated carbon is used as a positive electrode, and the [002] plane spacing by X-ray diffraction is 0.338 to 0.35.
A secondary power supply having an upper limit voltage of 3 V, in which an electrode in which lithium ions are preliminarily occluded in a carbon material having a thickness of 6 nm is used as a negative electrode, and JP-A-8-107048 discloses a carbon material capable of occluding and releasing lithium ions. A battery using a carbon material, in which lithium ions have been occluded in advance by a chemical method or an electrochemical method, as a negative electrode is disclosed in
No. 5342 proposes a secondary power supply having an upper limit voltage of 4 V and having a negative electrode in which a carbon material capable of inserting and extracting lithium ions is supported on a porous current collector which does not form an alloy with lithium. However, these secondary power supplies have a problem that a step of previously absorbing lithium ions into the carbon material of the negative electrode is required.

In addition to the electric double layer capacitor, a power source capable of charging and discharging a large current is a lithium ion secondary battery.
Lithium-ion secondary batteries have the characteristics of higher voltage and higher capacity than electric double-layer capacitors, but have the problem of high resistance and a significantly shorter life due to rapid charge / discharge cycles than electric double-layer capacitors. Was.

Further, in a secondary power supply using an activated carbon as a positive electrode, a carbon material such as a graphite-based carbon material capable of occluding and releasing lithium ions as a negative electrode, and an organic electrolyte containing lithium ions as an electrolyte, both the positive and negative electrodes are activated carbon. Although it is possible to develop a higher voltage than an electric double layer capacitor mainly composed of, a negative electrode material is charged and discharged due to electrochemical reactions such as occlusion and desorption reactions of lithium ions into carbon at the negative electrode. In some cases. In particular,
For a graphite-based carbon material having a [002] plane spacing of 0.335 to 0.337 nm obtained by X-ray diffraction,
When charge / discharge was repeated at a charge / discharge current of mA / cm ² or more, the change in capacity was large.

[0006]

Therefore, according to the present invention, the [002] plane obtained by the X-ray diffraction method has a plane spacing of 0.3.
It solves the problem that the rate of change in capacity after a charge / discharge cycle with a charge / discharge current of 5 mA / cm ² or more when using a graphite-based carbon material of 35 to 0.337 nm is large, enabling rapid charge / discharge. An object is to provide a secondary power supply having a high withstand voltage, a high capacity, and a high energy density.

[0007]

The present invention has succeeded in solving the above-mentioned problems by adopting the following constitution. (1) In a secondary power supply having a positive electrode containing activated carbon, a negative electrode containing carbon capable of absorbing and desorbing lithium ions, and an organic electrolyte containing lithium ions, the carbon contained in the negative electrode has a hexagonal network structure. Contains boron, and the [002] plane spacing measured by the X-ray diffraction method is 0.337 to 0.4.
A secondary power supply having a thickness of 10 nm.

(2) The secondary power source according to (1), wherein the boron content in the hexagonal mesh structure of the negative electrode carbon is 0.5 to 8% by mass in terms of boron. (3) The secondary power supply according to (1) or (2), wherein the positive electrode contains a lithium-containing transition metal oxide in addition to activated carbon. (4) The secondary power source according to (3), wherein the content of the lithium-containing transition metal oxide in the positive electrode is 1 to 30% by mass in the positive electrode.

(5) The method for manufacturing a secondary power supply according to any one of (1) to (4), wherein the [002] plane of the hexagonal mesh structure measured by an X-ray diffraction method. The interval is 0.355-
Amorphous carbon having a diameter of 0.420 nm is mixed with a boron compound in an inert gas atmosphere or vacuum in a range of 1300 to 3000.
A method for manufacturing a secondary power supply, wherein the negative electrode carbon is prepared by heat treatment at a temperature of ° C. to adjust the [002] plane spacing to 0.337 to 0.410 nm. (6) The method according to (5), wherein the boron compound is B ₄ C or B ₂ O ₃ .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present specification, a positive electrode body is obtained by joining a positive electrode containing activated carbon and a current collector and integrating them. The same definition applies to the negative electrode body. Further, both the secondary battery and the electric double layer capacitor are one kind of secondary power supply. In this specification, however, the specific configuration of the secondary battery includes activated carbon in the positive electrode and carbon capable of absorbing and desorbing lithium ions in the negative electrode. The secondary power supply is simply called a secondary power supply.

According to the present invention, the positive electrode is made of activated carbon, the negative electrode is made of an electrode mainly composed of carbon capable of absorbing and desorbing lithium ions, and an organic electrolyte containing a lithium salt is used. At the negative electrode, lithium ions in the electrolytic solution are occluded by carbon capable of inserting and extracting lithium ions. In the present specification, the term "adsorption" refers to the adsorption of ions to activated carbon by the formation of an electric double layer during charging, and the term "occlusion" refers to a reaction involving charge transfer. In addition, detachment of ions from activated carbon during discharge is called desorption, and that accompanied by charge transfer is called desorption.

In general, carbon can develop a graphite structure by reacting with a boron compound, and can reduce the spacing between [002] planes of a hexagonal mesh structure measured by X-ray diffraction. For example, by treating graphitizable carbon generated from pitch or coke of petroleum or coal at 2000 to 3000 ° C. in a boron compound and inert gas atmosphere,
The plane spacing of the [002] plane of graphite consisting of only carbon atoms is 0.
Graphite smaller than 3354 nm can be obtained.

The same applies to amorphous carbon used in the production of the negative electrode for a secondary power supply of the present invention.
It reacts with a boron compound at 00 to 3000 ° C. to develop a graphite structure in a fine part, and a plane spacing (hereinafter simply referred to as “plane spacing”) of a [002] plane of a hexagonal mesh structure measured by an X-ray diffraction method.
). Specifically, while the untreated amorphous carbon has an interplanar spacing of 0.355 to 0.420 nm, the above heat treatment can reduce the spacing to 0.337 to 0.410 nm. If the above-mentioned plane spacing is larger than 0.410 nm, the initial Coulomb efficiency becomes low, and if it is smaller than 0.337 nm, deterioration during charge / discharge cycles becomes large, which is not preferable. In addition, the plane spacing of the present invention was measured by an X-ray diffraction measuring device (RINT1000, manufactured by Rigaku Corporation) and calculated from the angle at which the X-ray diffraction intensity was the strongest.

The boron compound used in the above heat treatment is preferably B ₄ C, B ₂ O ₃ or the like.
0-3000 ° C is suitable. However, in a nitrogen atmosphere,
If heat treatment is performed at a temperature exceeding 000 ° C., boron nitride may be formed on the carbon surface.
When the temperature is higher than 00 ° C., the heat treatment is preferably performed in an argon atmosphere or a vacuum. That is, the heat treatment temperature in the nitrogen atmosphere is suitably in the range of 1300 to 2000 ° C. By using the boron-containing carbon thus obtained as a negative electrode of a secondary power supply, the capacity can be improved, and the film formed on the carbon surface during charging and discharging is strong and stable, so that Deterioration due to cycles can be suppressed. The more preferable range of the heat treatment temperature is 150
0-2100 ° C.

The amount of boron contained in the carbon of the negative electrode is 0.1.
A range of 5 to 8.0% by mass is appropriate. If the content is less than 0.5% by mass, the capacity of the secondary power supply cannot be improved, and
If it exceeds 0% by mass, the capacity change accompanying the charge / discharge cycle becomes large. A more preferred range is 0.8 to 5.0% by mass.

The positive electrode of the secondary power supply of the present invention preferably contains a lithium-containing transition metal oxide. This composition is considered to be effective in resolving the shortage of lithium ions in the electrolyte due to the deterioration during the charge / discharge cycle. When this positive electrode is used, the reaction that occurs at the negative electrode during charging is to occlude lithium ions in the electrolytic solution and lithium ions released from the positive electrode.

As the lithium-containing transition metal oxide compounded in the positive electrode, V, Fe, Co, Mn, Ni, W and Zn
Preferred is a composite oxide of one or more transition metals selected from the group consisting of and lithium. Particularly preferred are Co,
It is a composite oxide of lithium and one or more selected from the group consisting of Mn and Ni, and specific examples include the following. Li _x Co _y Ni _(1-y) O ₂ Li _z Mn ₂ O ₄ (provided that 0 <x <2, 0 ≦ y ≦ 1, 0 <z <2)

The amount of the lithium-containing transition metal oxide in the positive electrode is preferably 1 to 30% by mass. When the amount is less than 1% by mass, the amount of lithium ions desorbed at the time of the first charge is
This is not enough for the amount of lithium ions that can be absorbed by the negative electrode, and the voltage of the secondary power supply cannot be increased. When the content exceeds 30% by mass, the amount of activated carbon in the positive electrode becomes relatively small.
The capacity decrease in the charge / discharge cycle increases. A more preferred range is 5 to 20% by mass.

The activated carbon contained in the positive electrode preferably has a BET specific surface area of 300 to 3000 m ² / g. B
A more preferable range of the ET specific surface area is 500 to 2500 m.
² / g. Raw material of activated carbon, activation conditions are not limited, for example, as a raw material, coconut, phenolic resin,
Petroleum coke and the like can be mentioned, and examples of the activation method include a steam activation method and a molten alkali activation method. In order to reduce the resistance of the electrode, it is preferable to mix conductive carbon black, graphite or the like as a conductive agent in the electrode, and the compounding amount of the conductive agent is appropriately in the range of 0.1 to 20% by mass in the positive electrode. is there. A more preferred range of the amount of the conductive agent is 5.0.
１５15% by mass.

As a method for producing a positive electrode body, for example, polytetrafluoroethylene is added as a binder to a mixture of activated carbon powder, lithium-containing transition metal oxide powder, and carbon black as a conductive agent, and the mixture is kneaded. There is a method in which a positive electrode is formed into a sheet shape, and the sheet is fixed to a current collector using a conductive adhesive. Further, in a varnish in which polyvinylidene fluoride, polyamideimide, polyimide, etc. are dissolved as a binder, only the activated carbon powder and the lithium-containing transition metal oxide powder, or the activated carbon powder are dispersed, and this liquid is applied to the current collector by a doctor blade method or the like. Coating and drying. The amount of the binder contained in the positive electrode is preferably in the range of 1 to 20% by mass in order to balance properties such as strength and capacity of the positive electrode body.

The organic electrolyte used in the present invention has a cation of lithium ion and an anion of PF ₆ ⁻ , BF ₄ ⁻ , C
10 ₄ ⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , CF ₃ SO ₃ ⁻ ,
_{C (SO 2 CF 3) 3} -, AsF 6 - and SbF ₆ ^- consists of one or more selected from the group of the solvent of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, One or more selected from the group of sulfolane and dimethoxyethane are preferred. The concentration of the electrolyte in the organic electrolyte is preferably adjusted to 0.5 to 2 mol / l in order to increase the electric conductivity.

The type of the separator used in the present invention is not limited as long as it is insoluble in the organic electrolyte and has a certain strength. Specifically, it can be made of polyethylene, polypropylene, rayon, polybutylene terephthalate, polyphenylene sulfide, or the like. Among them, polyethylene, polypropylene and rayon are advantageous in terms of cost, but polybutylene terephthalate and polyphenylene sulfide are advantageous in terms of heat resistance. The form of the separator is preferably a porous film or a nonwoven fabric.

[0023]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The production and measurement of the cells in Examples and Comparative Examples were all performed in an argon glove box having a dew point of −60 ° C. or less. Cell diameter is 10.8m
m, and a coin cell having a height of 1.7 mm was used.

Example 1 A cathode body was prepared by using a phenol resin as a raw material and having a BET specific surface area of 20 obtained by a steam activation method.
Ethanol was added to a mixture of 70% by mass of activated carbon of 00m ² / g, 20% by mass of conductive carbon black, and 10% by mass of polytetrafluoroethylene as a binder, kneaded and rolled, and then heated at 200 ° C. for 2 hours. Vacuum drying was performed to obtain an electrode sheet. This electrode sheet was adhered to a coin cell cap using a conductive adhesive containing polyamideimide as a binder, and heat-treated under reduced pressure at 300 ° C. for 2 hours to obtain a positive electrode body of Example 1.

The anode body is made of a phenol resin as a raw material.
0.37 spacing between [002] planes obtained by heat treatment at 00 ° C
3 nm of amorphous carbon and B ₂ O ₃
Treatment at 500 ° C. produced a boron-containing carbon. Then, the boron-containing carbon and vapor-grown carbon (VGCF) heat-treated at 2800 ° C. as a conductive agent were dispersed in N-methyl-2-pyrrolidone in which polyvinylidene fluoride (PVDF) as a binder component was dissolved. The mass composition ratio of the negative electrode was as follows: boron-containing carbon: VGCF: PVDF = 7:
1: 2. The spacing between the [002] planes of the boron-containing carbon was 0.365 nm, and the amount of boron incorporated in the carbon was 2.5% by mass. Coating the dispersion on the copper current collector
It was dried at 00 ° C., punched into a diameter of 60 mm, resistance-welded to a coin cell case, and dried under reduced pressure at 130 ° C. to obtain a negative electrode body.

Using the above-mentioned positive electrode body and negative electrode body, 1.0 mol / L LiB was interposed through a polypropylene separator.
A coin cell was prepared using ethyl methyl carbonate containing F ₄ and ethylene carbonate (volume ratio 1: 1) as electrolytes, and the initial capacity was measured. The charge / discharge cycle was repeated 1,000 times between 4.2 V and 2.75 V. , The capacity was measured, and the rate of change in capacity from the initial value was calculated. The results are shown in Table 1.

[Example 2] The same positive electrode body as in Example 1 was used. The negative electrode is made of phenolic resin
Heat treatment at 00 ° C [002] plane spacing 0.380n
m of amorphous carbon and B ₂ O ₃ in an argon atmosphere at 250
Treatment at 0 ° C. produced a boron-containing carbon. This boron-containing carbon and vapor-grown carbon (VGCF) treated at 2800 ° C. as a conductive agent were dispersed in N-methyl-2-pyrrolidone in which polyvinylidene fluoride (PVDF) as a binder component was dissolved. The mass composition ratio of the negative electrode was boron-containing carbon: VGCF: PVDF = 7: 1: 2. The plane spacing of the boron-containing carbon was 0.372 nm, and the amount of boron incorporated in the carbon was 2.5% by mass. A coin cell was manufactured using the above-described positive electrode body and negative electrode body, and using the same separator and electrolytic solution as in Example 1, and the initial capacity was measured. Thereafter, a charge / discharge cycle was repeated 1,000 times between 4.2 V and 2.75 V, and the capacity was measured to calculate the rate of change in capacity from the initial state. The results are shown in Table 1.

Example 3 The same positive electrode body as in Example 1 was used. For the negative electrode, use phenol resin as raw material.
0.373n spacing between [002] planes heat treated at 00 ° C
m of amorphous carbon and B ₂ O ₃ in an argon atmosphere at 250
Treatment at 0 ° C. produced a boron-containing carbon. This boron-containing carbon and vapor-grown carbon (VGCF) treated at 2800 ° C. as a conductive agent were dispersed in N-methyl-2-pyrrolidone in which polyvinylidene fluoride (PVDF) as a binder was dissolved. The mass composition ratio of the negative electrode was boron-containing carbon: VGCF: PVDF = 7: 1: 2. The plane spacing of boron-containing carbon was 0.362 nm, and the amount of boron incorporated in carbon was 5.0% by mass. A coin cell was manufactured using the above-described positive electrode body and negative electrode body, and using the same separator and electrolytic solution as in Example 1, and the initial capacity was measured. Thereafter, a charge / discharge cycle was repeated 1,000 times between 4.2 V and 2.75 V, and the capacity was measured to calculate the rate of change in capacity from the initial state. The results are shown in Table 1.

Example 4 The same positive electrode body as in Example 1 was used. For the negative electrode, use phenol resin as raw material.
0.390n spacing between [002] planes heat treated at 00 ° C
m of amorphous carbon and B ₂ O ₃ in an argon atmosphere at 250
Treatment at 0 ° C. produced a boron-containing carbon. This boron-containing carbon and vapor grown carbon (VGCF) treated at 2800 ° C. as a conductive agent are mixed with N-methyl-2-, which dissolves polyvinylidene fluoride (PVDF) as a binder component.
Dispersed in pyrrolidone. The mass composition ratio of the negative electrode was boron-containing carbon: VGCF: PVDF = 7: 1: 2. The spacing between [002] planes of boron-containing carbon is 0.385 n
m, the amount of boron incorporated in the carbon was 2.5% by mass. A coin cell was manufactured using the above-described positive electrode body and negative electrode body, and using the same separator and electrolytic solution as in Example 1, and the initial capacity was measured. Then from 4.2V to 2.75
The charge / discharge cycle was repeated 1000 times up to V, and the capacity was measured to calculate the rate of change in capacity from the initial. The results are shown in Table 1.

Example 5 The same positive electrode body as in Example 1 was used. For the negative electrode, use phenol resin as raw material.
0.373n spacing between [002] planes heat treated at 00 ° C
m of amorphous carbon and B ₄ C in an argon atmosphere at 2500
C. to produce boron-containing carbon. This boron-containing carbon and vapor-grown carbon (VGCF) treated at 2800 ° C. as a conductive agent were dispersed in N-methyl-2-pyrrolidone in which polyvinylidene fluoride (PVDF) as a binder component was dissolved. The mass composition ratio of the negative electrode was boron-containing carbon: VGCF: PVDF = 7: 1: 2. The plane spacing of the boron-containing carbon was 0.368 nm, and the amount of boron incorporated in the carbon was 2.5% by mass. A coin cell was manufactured using the above-described positive electrode body and negative electrode body, and using the same separator and electrolytic solution as in Example 1, and the initial capacity was measured. Thereafter, a charge / discharge cycle was repeated 1,000 times between 4.2 V and 2.75 V, and the capacity was measured to calculate the rate of change in capacity from the initial state. The results are shown in Table 1.

Example 6 The same positive electrode body as in Example 1 was used for 63% by mass of activated carbon, 7% by mass of LiCoO ₂ , 20% by mass of conductive carbon black, and 10% by mass of polytetrafluoroethylene as a binder. After adding ethanol to the mixture, kneading and rolling were performed, and vacuum-dried at 200 ° C. for 2 hours to obtain an electrode sheet. This electrode sheet was bonded to a coin cell using a conductive adhesive having polyamideimide as a binder, and heat-treated at 300 ° C. for 2 hours under reduced pressure to obtain a positive electrode body. The negative electrode body, the electrolytic solution, and the separator are the same as those in Example 1.
A coin cell was prepared using the same method as described above, and the initial capacity was measured. The charge / discharge cycle was repeated 1,000 times between 4.2 V and 2.75 V, and the capacity was measured. Calculated. The results are shown in Table 1.

Comparative Example 1 The same positive electrode body as in Example 1 was used. For the negative electrode, use phenol resin as raw material.
0.373n spacing between [002] planes heat treated at 00 ° C
m of amorphous carbon and B ₂ O ₃ in an argon atmosphere for 200
Treatment at 0 ° C. produced a boron-containing carbon. This boron-containing carbon and vapor-grown carbon (VGCF) treated at 2800 ° C. as a conductive agent were dispersed in N-methyl-2-pyrrolidone in which polyvinylidene fluoride (PVDF) as a binder component was dissolved. The mass composition ratio of the negative electrode was boron-containing carbon: VGCF: PVDF = 7: 1: 2. The plane spacing of the boron-containing carbon was 0.371 nm, and the amount of boron incorporated in the carbon was 0.3% by mass. A coin cell was manufactured using the above-described positive electrode body and negative electrode body, and using the same separator and electrolytic solution as in Example 1, and the initial capacity was measured. Thereafter, a charge / discharge cycle was repeated 1,000 times between 4.2 V and 2.75 V, and the capacity was measured to calculate the rate of change in capacity from the initial state. The results are shown in Table 1.

[Comparative Example 2] The same positive electrode body as in Example 1 was used. The negative electrode is made from petroleum pitch
Carbon having a plane spacing of 0.345 nm between the [002] plane and B ₂ O ₃ heat treated at ₂ ° C. was treated at 2800 ° C. in an argon atmosphere to produce boron-containing carbon. This boron-containing carbon and vapor-grown carbon (VGCF) treated at 2800 ° C. as a conductive agent were dispersed in N-methyl-2-pyrrolidone in which polyvinylidene fluoride (PVDF) as a binder component was dissolved. The mass composition ratio of the electrode was boron-containing carbon: VGCF: PVDF = 7: 1: 2. The plane spacing of the boron-containing carbon was 0.335 nm, and the amount of boron incorporated in the carbon was 0.3% by mass. Using the same separator and electrolytic solution as in Example 1, a coin cell was prepared, and the initial capacity was measured. Thereafter, the charge / discharge cycle was repeated 1000 times between 4.2 V and 2.75 V, the capacity was measured, and the rate of change in capacity from the initial value was calculated. The results are shown in Table 1.

Comparative Example 3 The same positive electrode body as in Example 1 was used. The negative electrode used as carbon was MCMB6.28 (trade name of [002] plane 0.336 made by Osaka Gas Co., Ltd.).
nm) and in the same manner as in Example 1, the above carbon: vapor-grown carbon (VGCF): polyvinylidene fluoride (PVD)
F): A negative electrode body was manufactured so as to be 7: 1: 2. A coin cell was manufactured using the above-described positive electrode body and negative electrode body, and using the same separator and electrolytic solution as in Example 1, and the initial capacity was measured. Thereafter, the charge / discharge cycle was repeated 1000 times between 4.2 V and 2.75 V, the capacity was measured, and the rate of change in capacity from the initial value was calculated. The results are shown in Table 1.

[0035]

[Table 1]

(Evaluation) As is apparent from Table 1, the coin cells of Examples 1 to 6 have extremely low capacity change rates as compared with the coin cells of Comparative Examples 1 and 2, and the coin cells of Examples 1 to 6 were charged to 4.2V. It was found that the coin cells of Nos. 1 to 6 were able to maintain high withstand voltage with little deterioration due to charge / discharge cycles.

[0037]

According to the present invention, by employing the above structure, it is possible to provide a secondary power supply having a high withstand voltage, a large capacity, a high energy density and a high reliability of a rapid charge / discharge cycle. Was.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Car Isamu 1150 Hazawa, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. F-term (reference) 4G046 CB09 CC02 CC03 HB07 5H029 AJ03 AJ05 AK03 AL01 AL02 AL07 AM02 AM03 AM04 AM05 AM07 CJ02 CJ28 DJ17 HJ01 HJ13 HJ14 5H050 AA07 AA08 BA17 CA08 CA09 CA16 CA29 CB08 EA01 EA12 FA19 GA02 GA27 HA01 HA13 HA14

Claims (6)

[Claims] 1. A secondary power source comprising a positive electrode containing activated carbon, a negative electrode containing carbon capable of inserting and extracting lithium ions, and an organic electrolyte containing lithium ions, wherein carbon contained in the negative electrode is formed by a hexagonal mesh. Containing boron in the surface structure,
The [002] plane spacing measured by the X-ray diffraction method is 0.33.
A secondary power supply having a thickness of 7 to 0.410 nm. 2. The secondary power supply according to claim 1, wherein the boron content in the hexagonal mesh structure of the negative electrode carbon is 0.5 to 8% by mass in terms of boron. 3. The positive electrode contains a lithium-containing transition metal oxide in addition to activated carbon.
Or the secondary power supply according to 2. 4. The secondary power supply according to claim 3, wherein the content of the lithium-containing transition metal oxide in the positive electrode is 1 to 30% by mass in the positive electrode. 5. The method for manufacturing a secondary power supply according to claim 1, wherein the spacing of the [002] plane of the hexagonal mesh structure measured by X-ray diffraction is 0. 355-0.4
Amorphous carbon having a thickness of 20 nm is heat-treated together with a boron compound at a temperature of 1300 to 3000 ° C. in an inert gas atmosphere or vacuum to reduce the [002] plane spacing to 0.337.
A method for producing a secondary power supply, wherein the carbon prepared to a thickness of 0.410 nm is used as the negative electrode carbon. 6. The method according to claim 1, wherein the boron compound is B ₄ C or B ₂ O _3.
6. The method for manufacturing a secondary power supply according to claim 5, wherein: