JP2960834B2 - Lithium secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode obtained by mixing a composite in which copper oxide is adhered on the surface of all or a part of graphite capable of intercalating and deintercalating lithium and a binder. The present invention relates to a used lithium secondary battery.

[0002]

2. Description of the Related Art With the miniaturization and power saving of electronic devices,
A secondary battery using an alkali metal such as lithium has attracted attention. When an alkali metal such as lithium is used alone for the negative electrode, repetition of charge and discharge, that is, dendrite and (dendritic crystals) are generated and grown on the surface where the metal is dissolved and deposited by the process of dissolving and depositing the alkali metal. Therefore, there is a problem that a short circuit inside the battery is induced by penetrating through the separator and coming into contact with the positive electrode. It was found that when an alkali metal alloy was used in place of the alkali metal for the negative electrode of the secondary battery, the generation of dendrites was suppressed and the charge / discharge cycle characteristics were improved as compared with the case of a single battery. However, the use of the alloy does not completely prevent the generation of dendrite, and may cause a short circuit inside the battery. In recent years, instead of using a dissolution-precipitation process or a dissolution-precipitation-solid diffusion process of a metal such as an alkali metal or an alloy thereof, carbon using an absorption-release process of an alkali metal ion has been used. Organic materials such as conductive polymers have been developed. As a result, the generation of dendrite generated when an alkali metal or an alloy thereof is used does not occur in principle, and the problem of a short circuit inside the battery has been drastically reduced.

[0003] Since carbon is chemically stable and can be doped with both an electron donating substance and an electron accepting substance, it is a promising material as an electrode, particularly as an electrode for a battery.

When carbon is used as a negative electrode active material, the amount of lithium inserted between carbon layers is 1 atom of lithium to 6 atoms of carbon, that is, C6Li, and the amount of lithium per unit weight of carbon at that time is limited. Is 372 mAh / g.
Carbon has a wide range of structures from what is called amorphous carbon to graphite, and the size and arrangement of carbon hexagonal planes vary depending on starting materials, production methods and the like. Examples of carbon materials conventionally used as negative electrode active materials include, for example, JP-A Nos. 62-90863, 62-122066, 63-213267, and 1-2.
JP-A-04361, JP-A-2-82466, JP-A-3-252053, JP-A-3-285273, JP-A-3-289068 and the like.

[0005] None of these carbons reach the above-mentioned theoretical capacity, and even if they have a certain large capacity, the potential at the time of deintercalation of lithium increases linearly, and the battery system actually increases. In some cases, the battery does not show a sufficient capacity in the potential range that can be used, and a negative electrode having a satisfactory negative electrode capacity for manufacturing a battery cannot be manufactured. Further, when producing an electrode, the true density of the carbon material is also required, but when considering the density per unit volume, the bulk density is an important factor. The bulk density is governed by the shape and size of the carbon particles, and in the examples of JP-A-62-90863,
82466, JP-A-3-285273, JP-A-3-28
It is difficult to increase the capacity density per unit volume with fibrous carbon as shown in No. 9068, and none of these fibrous carbons reach the above-mentioned theoretical capacity. It is not possible to produce a negative electrode having Also, JP-A-63-2455
Although pyrolytic carbon produced by a gas phase method as shown in FIG. 5 exhibits high charge / discharge stability, it is difficult to produce a thick-film electrode by this method, and it is difficult to obtain a high-capacity electrode.

On the other hand, R. Fong, U. Sacken, and J.
As described in R. Dahn, J. Electrochem. Soc., 137, 2009 (1990), when graphite is used as the negative electrode active material, although the theoretical discharge capacity is obtained, it is a small current measurement. It is not satisfactory for practical use. Further, as disclosed in JP-A-4-112455, JP-A-4-115457, JP-A-4-115458, JP-A-4-237971, JP-A-5-28996, etc. as those using a graphite material as a negative electrode active material, Since the above-mentioned theoretical capacity has not been reached, a negative electrode which is satisfactory as a negative electrode capacity in manufacturing a battery cannot be manufactured.

As disclosed in Japanese Patent Application Laid-Open No. 5-21065, a chalcogen compound having a reaction of inserting and removing lithium ions at an average voltage of 2 V (Li / Li ⁺ ) or less and a carbonaceous material capable of inserting and removing lithium ions. However, there is a problem that the charge / discharge voltage is low and the energy density is reduced.

As disclosed in Japanese Patent Application Laid-Open No. Hei 4-184863, a metal (nickel, copper) film is formed on a carbon material.
By using a mixed anode of carbon and a metal (a metal not alloyed with at least one kind of lithium) as in 259768, the cycle characteristics can be improved, and the high-rate discharge after leaving at high temperature can be improved. No fundamental improvement in anode capacity can be expected.

As described in Japanese Patent Application Laid-Open No. 3-216960, by forming lithium on the surface of the carbon body so as not to block the hole, a large current can be taken out, and the secondary battery has improved cycle life and safety. A battery can be obtained, and the use of a negative electrode in which a carbonaceous material is impregnated with an alloy capable of forming an alloy with an active material as described in JP-A-4-39864 has a large electrode capacity, excellent charge / discharge cycle characteristics, and self-discharge. A secondary battery with improved characteristics can be obtained,
There is a problem that the number of steps in manufacturing the electrode increases.

As disclosed in Japanese Patent Application Laid-Open No. 4-179049, the use of a composite negative electrode of a conductive polymer and a metal and / or a carbon-based material can provide a flexible negative electrode for a battery having a long cycle life. There's a problem.

[0011]

SUMMARY OF THE INVENTION As described above,
Even if various carbon materials and graphite materials are used for the negative electrode active material, the theoretical capacity (372 mAh / g) is not reached, and a negative electrode having a satisfactory negative electrode capacity for manufacturing a battery cannot be manufactured. However, although the graphite material can basically charge and discharge the theoretical capacity, there is a problem that the charge and discharge current value used at that time is not a practically usable current value. In addition, the reaction of inserting and removing lithium ions has an average voltage of 2 V (Li / Li
+) A negative electrode mixed with a chalcogen compound and a carbonaceous material capable of inserting and removing lithium ions is used, but the charge / discharge voltage is low and the energy density is low. In the case of a composite anode with a metal that does not form an anode, it is not possible to bring about a fundamental improvement in the anode capacity, and in a composite anode in which carbon is coated with lithium or a metal that forms an alloy with lithium, the number of steps in electrode production increases. There is a problem in the charge / discharge capacity of a composite negative electrode of a conductive polymer and a metal and / or a carbon-based material. Furthermore, as described in Japanese Patent Application No. 5-112835, when an electrode in which graphite and copper oxide are mixed is used, there is a problem that the mixed copper oxide has a portion not involved in the reaction.

In view of the above-mentioned circumstances, the present invention provides a high-capacity, high-capacity electrode by providing an electrode obtained by mixing copper oxide and a binder with graphite capable of intercalating / deintercalating lithium. It is an object of the present invention to provide a graphite-mixed negative electrode capable of reducing the number of steps in production, and a lithium secondary battery having a high capacity and a high voltage.

[0013]

According to the present invention, a positive electrode,
In a battery comprising a negative electrode and a non-aqueous ion conductor,
The composite in which the negative electrode is made of graphite capable of intercalating / deintercalating lithium ions as a main component of the negative electrode active material, and a composite in which copper oxide is adhered on the surface of all or part of the graphite particles and a binder And a lithium secondary battery that is an electrode in which is mixed.

The negative electrode of the present invention can be oxidized by coating copper on the surface of all or a part of graphite particles capable of intercalating / deintercalating lithium ions as a negative electrode active material and then subjecting the particles to an oxidation treatment. It is produced by using a composite produced by a production method for producing copper and mixing this with a binder. At this time, the negative electrode and the negative electrode current collector can be integrally formed using the negative electrode current collector.

Graphite as a main component of the negative electrode active material used in the present invention has an average spacing (d ₀₀₂ ) of (002) planes by a wide angle X-ray diffraction method of 0.335 to 0.340 nm,
The crystallite thickness (Lc) in the (002) plane direction is 10 nm or more, and the crystallite thickness (La) in the (110) plane direction is 10 nm.
The above materials are used, and a high-capacity electrode can be obtained by using these materials. Factors affecting the capacity and charge / discharge potential include physical properties related to the layered structure of carbon. Physical properties related to the layered structure of carbon include (00
2) The plane spacing (d ₀₀₂ ) of the planes, that is, the interlayer distance, and the crystallite size are present. Since the potential at the time of deintercalation of lithium becomes closer to the potential of lithium by increasing the degree of crystallinity, it is possible to expect to obtain a higher capacity carbon body electrode. Therefore, when assuming the usable battery capacity when assembling as a lithium secondary battery, the average spacing (d ₀₀₂ ) of the (002) plane by the X-ray wide-angle diffraction method is 0.335 to 0.340 nm. Preferably, there is. (002) Crystallite thickness in the plane direction (L
In c), when the thickness is 10 nm or less, the crystallinity is poor, so that when assembled as a lithium secondary battery, the usable battery capacity becomes small, which is not practical. (110)
When the crystallite thickness (La) in the in-plane direction is less than 10 nm, the crystallinity is poor. Therefore, when assembled as a lithium secondary battery, the usable battery capacity becomes small, which is not practical.

The graphite used as the main component of the negative electrode active material used in the present invention was prepared by using argon laser Raman.
580 cm ^-1 near the peak intensity ratio of around 1360 cm ^-1 to the peak of, i.e. R value is preferably 0.4 or less. If it is larger than 0.4, the crystallinity will be low and the potential at the time of deintercalation of lithium will be higher than the potential of lithium, so the battery capacity that can be used when assembled as a lithium secondary battery is Small and impractical.

Examples of the graphite which can be used include artificial graphite obtained from easily graphitizable carbon such as natural graphite, quiche graphite, petroleum coke or coal pitch coke, or expanded graphite, which satisfies the above physical property conditions. Graphites, and as shapes, spherical, flaky,
Any of fibrous or crushed products thereof may be used, but spherical, flaky or crushed products thereof are preferred.

When graphite is used as the negative electrode, the graphite preferably has a particle size of 80 μm or less. The particle size is a value obtained as a particle size having a peak in a particle size distribution obtained by a particle size distribution measurement on a volume basis. 80
When graphite having a particle size larger than μm is used, the contact area with the electrolytic solution becomes smaller, so that diffusion of lithium in the particles,
Problems such as a decrease in the number of reaction sites occur, and problems arise in charging and discharging with a large current.

As a method for producing a composite in which copper oxide is adhered on the surface of graphite particles, a method of producing copper oxide by coating copper on a part of the surface of graphite particles and then performing an oxidation treatment. There is. Among these methods, methods for coating copper on the surface of graphite particles include electroless plating of copper, evaporation using heat evaporation while keeping copper under high vacuum, sputtering using heat evaporation and ion bombardment, etc. Is mentioned. Of these, the electroless plating method is preferred in terms of cost and work. The electroless plating of copper includes, for example, an alkali bath using formaldehyde, hydrazine, or the like as a reducing agent. It is also possible to use a commercially available electroless copper plating bath.

After coating with copper, an oxidation treatment is performed. The oxidation treatment may be carried out by a method of oxidizing using a gaseous oxidizing agent, for example, air, oxygen, ozone, etc., or a liquid oxidizing agent, for example, hydrogen peroxide, Examples include, but are not limited to, methods of oxidizing with water having dissolved oxygen and salts of oxoacids (such as nitrous acid, permanganic acid, chromic acid, dichromic acid, chloric acid, and hypochlorous acid). Not done.

In the oxidation treatment using air and oxygen, the treatment should be performed at a temperature lower than the combustion temperature of graphite. The combustion temperature of graphite varies depending on the type of graphite, but is approximately 60%.
0 ° C. or higher. Therefore, it is preferable to carry out at a temperature of 600 ° C. or lower. Also, in the following oxidation treatment using air and oxygen at 600, the type of graphite, oxidation time, oxygen partial pressure,
The graphite surface is oxidized to produce functional groups such as carboxyl groups, lactones, hydroxyl groups, carbonyl groups, etc., depending on the ratio of graphite to copper and the like. For this reason, it is more preferable to perform the oxidation treatment at 400 ° C. or lower.

In the copper-coated graphite composite formed during the manufacturing process of the graphite composite with copper oxide, the ratio of graphite to copper constituting the copper-coated graphite composite depends on the type and particle size of the graphite or the copper coating. Although it depends on the method and the like, the weight ratio of graphite to copper is preferably 98.5: 1.5 to 62:38. The ratio is more preferably 98.5: 1.5 to 75:25. If it is smaller than 98.5: 1.5, the effect of the attached copper oxide does not appear remarkably, and if it is larger than 62:38, the number of reaction sites of lithium ions decreases at the time of charging and discharging graphite, and the battery is assembled as a lithium secondary battery. When this occurs, the usable battery capacity is reduced, which is not practical.

The negative electrode is formed by mixing a composite having a copper oxide adhered on the surface of all or a part of the graphite particles and a binder. As the binder, a fluorine-based polymer such as polytetrafluoroethylene and polyvinylidene fluoride, a polyolefin-based polymer such as polyethylene and polypropylene, and synthetic rubbers can be used, but are not limited thereto. The mixing ratio is such that the weight ratio of the composite in which copper oxide is adhered on the surface of all or part of the graphite particles to the binder is 99: 1 to 70:30.
It can be. If the binder is larger than 70:30, a practical lithium secondary battery cannot be produced because the resistance or polarization of the electrode becomes large and the discharge capacity becomes small. On the other hand, if the binder is smaller than 90: 1, the binding ability is lost, and it is difficult to manufacture the battery due to the falling off of the active material and the decrease in mechanical strength. In the preparation of the negative electrode, it is preferable to perform a heat treatment at a temperature around the melting point of each binder in order to enhance the binding property.

A current collector is required to collect current from the negative electrode. Examples of the current collector include a metal foil, a metal mesh, and a three-dimensional porous body. As the metal used for the current collector, a metal which is unlikely to alloy with lithium is preferable in terms of mechanical strength when cycles are repeated. In particular, iron, nickel, cobalt, copper, titanium, vanadium, chromium, and manganese alone or alloys thereof are preferable.

As the ion conductor, for example, an organic electrolyte, a polymer solid electrolyte, an inorganic solid electrolyte, a molten salt, or the like can be used, and among them, an organic electrolyte can be preferably used. As the solvent for the organic electrolyte, propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, esters such as γ-butyrolactone, tetrahydrofuran, substituted tetrahydrofuran such as 2-methyltetrahydrofuran, dioxolane, diethyl ether , Dimethoxyethane, diethoxyethane,
Ethers such as methoxyethoxyethane, dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate, methyl acetate and the like;
Used as one or more mixed solvents. Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium borofluoride, lithium phosphofluoride, lithium arsenide hexafluoride, lithium trifluoromethanesulfonate, lithium halide, lithium aluminate, and the like. A mixture of two or more types is used. An electrolyte is prepared by dissolving the electrolyte in the solvent selected above. The solvent and the electrolyte used when preparing the electrolytic solution are not limited to those listed above.

As the positive electrode in the lithium secondary battery of the present invention, LiCoO ₂ , LiNiO ₂ and L
_{i x M y N z O 2} ( and a where M is Fe, Co, either Ni, N represents a transition metal, 4B group or 5B group metal,), LiMn ₂ O ₄ and LiMn _2-x An oxide containing lithium such as N _y O ₄ (where N represents a transition metal, a 4B group, or a 5B group metal) is used as a positive electrode active material, and a conductive material, a binder, and, in some cases, It is formed by mixing a solid electrolyte and the like. This mixing ratio depends on the active material 1
The conductive material can be 5 to 50 parts by weight and the binder can be 1 to 30 parts by weight with respect to 00 parts by weight. As the conductive material, carbons such as carbon black (acetylene black, thermal black, channel black, etc.), graphite powder, metal powder, and the like can be used, but are not limited thereto. As the binder, a fluorine-based polymer such as polytetrafluoroethylene or polyvinylidene fluoride, a polyolefin-based polymer such as polyethylene or polypropylene, or a synthetic rubber can be used, but is not limited thereto. If the conductive material is less than 5 parts by weight or the binder is more than 30 parts by weight, the resistance or polarization of the electrode increases and the discharge capacity decreases, so that a practical lithium secondary battery cannot be manufactured. When the amount of the conductive material is more than 50 parts by weight (parts by weight vary depending on the type of the conductive material to be mixed), the amount of the active material contained in the electrode decreases, and the discharge capacity as the positive electrode decreases. When the binder is smaller than 1 part by weight, the binding ability is lost. When the binder is larger than 30 parts by weight, as in the case of the conductive material,
This is not practical because the amount of active material contained in the electrode decreases, and, as described above, the resistance or polarization of the electrode increases and the discharge capacity decreases. In producing the positive electrode, it is preferable to perform a heat treatment at a temperature around the melting point of each binder in order to improve the binding property.

[0027]

The negative electrode according to the present invention, that is, an electrode obtained by mixing a binder and a composite in which copper oxide is adhered on the surface of all or part of graphite particles capable of intercalating / deintercalating lithium, High capacity. This is because a composite oxide of lithium and copper that progresses reversibly is formed in the electrochemically reduced copper oxide. Also, the number of steps in electrode production can be reduced as compared with a composite negative electrode in which carbon is coated with lithium or a metal forming an alloy with lithium. Furthermore, a mixture of a chalcogen compound having a high capacity and having an average voltage of 2 V (Li / Li ⁺ ) or less in the reaction of inserting and removing lithium ions and a carbonaceous material capable of inserting and removing lithium ions was mixed. Since a lower potential of the negative electrode can be used as compared to a battery using the negative electrode, a lithium secondary battery with a high battery voltage can be provided. Therefore, the lithium secondary battery using the negative electrode according to the present invention can provide an excellent lithium secondary battery that solves the above problems.

[0028]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Incidentally, a method for measuring the crystallite size (Lc, La) by the X-ray wide-angle diffraction method is a known method, for example, "Carbon Materials Experimental Techniques 1 p55-63, edited by The Society of Carbon Materials (Science and Technology Corporation). And the method described in JP-A-61-111907. Further, 0.9 was used as the shape factor K for obtaining the size of the crystallite. Also,
The particle size is measured using a laser diffraction type particle size distribution meter,
It was determined as a particle size having a peak in the particle size distribution.

Example 1 Preparation of Graphite Composite Attached to Copper Oxide The graphite particles of the composite having copper oxide adhered on the surface of all or a part of the graphite particles used as the negative electrode active material were added to natural graphite (flake-like) from Madagascar. , Particle size 11 μm, d ₀₀₂
Is 0.337 nm, Lc is 27 nm, La is 17 nm,
The R value was 0 and the specific surface area was 8 m ² / g), and this was subjected to electroless copper plating. Electroless copper plating was performed by the following method. First, the graphite powder was immersed in ethyl alcohol and dried, and then immersed in a sensitizing solution (a mixture of 30 g / l of SnCl ₂ .2H ₂ O and 20 ml / l of concentrated hydrochloric acid). 0.4 g / l PbCl ₂ .2H ₂ O and 3 ml
/ L of a mixed solution of concentrated hydrochloric acid). Next, 10 g /
1 CuSO ₄ .5H ₂ O, 50 g / l sodium potassium tartrate, 10 g / l sodium hydroxide, 10 ml
/ L of a solution in which 37% formalin was dissolved was added to an electroless copper plating bath adjusted to pH 12.0 with sodium hydroxide, and the graphite powder was copper-plated at room temperature while stirring the solution with a stirrer. This was dried at 60 ° C. The weight ratio of graphite to copper in the resulting copper-coated graphite powder was 83:17. This copper-coated graphite powder was oxidized in air at 250 ° C. for 5 hours to obtain a graphite composite to which copper oxide had adhered. When the powder X-ray wide-angle diffraction measurement of the graphite composite attached with copper oxide was performed, diffraction lines derived from graphite and diffraction lines derived from cupric oxide were observed.

Preparation of Negative Electrode A nonionic dispersant is added to the copper oxide-deposited graphite composite prepared by the above-described method, and polytetrafluoroethylene (after drying, the copper oxide-deposited graphite composite and polytetrafluoroethylene are mixed together). A dispersion liquid (weight ratio: 87:13) was added to form a paste, which was applied to both surfaces of a copper foil current collector. This is dried at 60 ° C., 240
After heat treatment at ℃, press and further 20 to remove moisture
What was dried under reduced pressure at 0 ° C. was used as a negative electrode. This negative electrode has a surface area of 8 cm ² and an electrode thickness of 75 μm (a current collector thickness of 50 μm).

Evaluation of Negative Electrode Current was collected from the copper current collector with a lead wire, and used as an electrode for evaluation. For evaluation, a three-electrode method was used, and lithium was used as a counter electrode and a reference electrode. The electrolytic solution is obtained by dissolving 1 mol / l of lithium perchlorate in a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate. The charge / discharge test is
The battery was initially charged to 0 V at a current density of 0.1 mA / cm ² , and subsequently discharged to 1.5 V at the same current. 2
The charge and discharge were repeated in the same potential range and current density after the first time, and the negative electrode was evaluated by the discharge capacity.

As a result, the discharge capacity in the second cycle was 458 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 421 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 2 Modified graphite (flaky, particle size 8 μm, d ₀₀₂₎ was used as graphite particles.
Is 0.337 nm, Lc is 17 nm, La is 12 nm,
R value is 0.1, specific surface area is 9 m ² / g) and 0.06 m
_{ol / l CuSO 4 · 5H 2} O of, 0.3mol / l of E
DTA, 0.4 mol / l formaldehyde, 170
mg / l of 7-iodo-8-hydroxyquinoline-5
The solution in which sulfonic acid was dissolved was p-p with sodium hydroxide.
A copper oxide-adhered graphite composite was produced by the method described in Example 1 except that plating was performed at 75 ° C. in an electroless copper plating bath adjusted to H12.8 and oxidation treatment was performed at 400 ° C. in air for 30 minutes. . The weight ratio of graphite to copper in the copper-coated graphite powder obtained at this time was 85:15. Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A negative electrode was prepared by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 71 μm (the current collector had a thickness of 5 μm).
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 462 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 435 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 3 Modified graphite (flaky, particle size 17 μm, d
₀₀₂ is 0.337 nm, Lc is 22 nm, La is 15 n
m, R value: 0.1, specific surface area: 9 m ² / g), 15 g
/ L Cu (NO ₃ ) ₂ .3H ₂ O, 10 g / l sodium bicarbonate, 30 g / l sodium potassium tartrate, 20 g / l sodium hydroxide, 100 ml / l 37% formalin Using an electroless copper plating bath whose solution was adjusted to pH 11.5 with sodium hydroxide,
A graphite composite attached with copper oxide was produced by the method described in Example 1 except that oxidation treatment was performed at 200 ° C. for 24 hours in oxygen. The weight ratio of graphite to copper in the copper-coated graphite powder obtained at this time was 91: 9. Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A negative electrode was prepared by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 88 μm (the thickness of the current collector was 5 μm).
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 439 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 415 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 4 As graphite particles, artificial graphite (flaky, particle size 35 μm, d
₀₀₂ is 0.336 nm, Lc is 22 nm, La is 13 n
m, R value is 0, specific surface area is 4 m ² / g), and 60 g / l
Of CuSO ₄ · 5H ₂ O, NiSO of 15g / l ₄ · 7H ₂
O, a solution in which 45 g / l hydrazine sulfate was dissolved, and 180 g / l sodium potassium tartrate, 45 g
/ L sodium hydroxide and 15 g / l sodium carbonate were dissolved in Example 1 except that they were oxidized at 350 ° C for 1 hour in air using an electroless copper plating bath mixed immediately before use. A graphite composite attached with copper oxide was prepared by the method described. The weight ratio of graphite to copper in the resulting copper-coated graphite powder was 89:11. Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 132 μm (the thickness of the current collector was 50 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 402 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 388 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 5 Artificial graphite (spherical, particle diameter 6 μm, d ₀₀₂ 0.339 nm, Lc 25 nm, La 13 nm, R
The value was 0.4, the specific surface area was 8 m ² / g), and MAC-100 (manufactured by Okuno Pharmaceutical Co., Ltd.) and M
Using AC-200 (manufactured by Okuno Pharmaceutical Co., Ltd.), MA
Described in Example 1 except that a 2-liquid type electroless copper plating bath (manufactured by Okuno Pharmaceutical Co., Ltd.) of C-500A and MAC-500B was used and oxidized at 70 ° C. for 15 hours in water containing dissolved oxygen. A graphite composite with a copper oxide was prepared by the method described above. The weight ratio of graphite to copper in the copper-coated graphite powder obtained at this time was 96: 4. In addition, when a powder X-ray wide-angle diffraction measurement of the produced graphite composite with copper oxide was performed, it was found to be graphite, cuprous oxide, and cupric oxide.

A negative electrode was prepared by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 71 μm (the current collector had a thickness of 5 μm).
0 μm).

This negative electrode was described in Example 1 except that the electrolyte was prepared by dissolving 1 mol / l lithium perchlorate in a 2: 1: 2 mixed solvent of ethylene carbonate, propylene carbonate, and diethyl carbonate. Was evaluated in the manner described.

As a result, the discharge capacity in the second cycle was 425 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 398 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 1 A negative electrode was produced in the same manner as in Example 1 except that only natural graphite produced in Madagascar was used. The surface area of the produced negative electrode was 8 cm ² and the thickness was 85 μm (the thickness of the current collector was 50 μm)
It is.

The negative electrode was evaluated by the method described in Example 1 except that the current density was 30 mA / g.

As a result, the discharge capacity in the second cycle was 358 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 344 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 2 Natural graphite produced from Madagascar was used as a main negative electrode active material, and this was mixed with a commercially available cupric oxide (particle size: 27 μm) in a mortar at a weight ratio of 80:20 to disperse a nonionic dispersion. And a dispersion liquid of polytetrafluoroethylene (the weight ratio of the combination of graphite and cupric oxide to polytetrafluoroethylene after drying is 87:13) is added, and the paste is added. It was applied on both sides on a copper foil current collector. This is dried at 60 ° C., heat-treated at 240 ° C., and then pressed.
The dried under reduced pressure was used as a negative electrode. This negative electrode
The surface area is 8 cm ² , and the thickness of the electrode is 138 μm (the thickness of the current collector is 50 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 371 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 335 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 3 Mesocarbon microbeads carbonized at 1000 ° C. as carbon particles (spherical, particle diameter 6 μm, d ₀₀₂ 0.349 n)
m and Lc are 1.3 nm, La cannot be calculated, and R value is 1.
3, specific surface area 1 m ² / g) and MAC as pretreatment liquid
-100 (manufactured by Okuno Pharmaceutical Co., Ltd.) and MAC-2
00 (manufactured by Okuno Pharmaceutical Co., Ltd.) and MAC-50
Example 1 except that a two-component type electroless copper plating bath of 0A and MAC-500B (manufactured by Okuno Pharmaceutical Co., Ltd.) was used.
, A copper oxide-adhered carbon composite was prepared.
The weight ratio of carbon to copper of the copper-coated carbon powder thus obtained was 81:19. Further, when the powdered X-ray wide-angle diffraction measurement of the produced copper oxide-adhered carbon composite was performed, it was found to be carbon and cupric oxide.

A negative electrode was manufactured by the method described in Example 1 using this copper oxide-adhered carbon composite. The produced negative electrode had a surface area of 8 cm ² and a thickness of 68 μm (the thickness of the current collector was 5
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 176 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 159 mAh per unit volume of the electrode (excluding the volume of the current collector).

Table 1 shows the results of Examples 1 to 5 and Comparative Examples 1 to 3.
Shown in From these results, it was found that when a negative electrode containing a graphite composite with copper oxide was used, a high capacity discharge capacity was obtained.

[0061]

[Table 1]

Example 6 As graphite particles, artificial graphite (flaky, particle size 77 μm, d
₀₀₂ is 0.337 nm, Lc is 26 nm, La is 14 n
m, R values are 0.1, specific surface area is 2 m ² / g), and MAC-100 (manufactured by Okuno Pharmaceutical Co., Ltd.) and MAC-200 (manufactured by Okuno Pharmaceutical Co., Ltd.) are used as pretreatment liquids. A copper oxide-adhered graphite composite was prepared by the method described in Example 1 except that a two-component electroless copper plating bath (manufactured by Okuno Pharmaceutical Co., Ltd.) of 500A and MAC-500B was used. The weight ratio of graphite to copper in the resulting copper-coated graphite powder was 87:13. Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 227 μm (the thickness of the current collector was 50 μm).

The negative electrode was evaluated by the method described in Example 1 except that the current density was 0.05 mA / cm ² .

As a result, the discharge capacity in the second cycle was 374 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 351 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 4 As graphite particles, artificial graphite (flaky, particle size 117 μm, d
₀₀₂ is 0.337 nm, Lc is 25 nm, La is 17 n
Except for using m and R values of 0.1 and a specific surface area of 1 m ² / g), a graphite composite adhering to copper oxide was prepared by the method described in Example 6. The weight ratio of graphite to copper in the resulting copper-coated graphite powder was 88:12. Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The surface area of the produced negative electrode was 8 cm ² , and the thickness was 305 μm (the thickness of the current collector was 50 μm).

The negative electrode was evaluated by the method described in Example 1 except that the current density was 0.05 mA / cm ² .

As a result, the discharge capacity in the second cycle was 361 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 337 mAh per unit volume of the electrode (excluding the volume of the current collector).

Table 1 shows the results of Examples 1 to 6 and Comparative Example 4. This proved that graphite having a particle size of 80 μm or less was good.

Example 7 A graphite composite adhering to copper oxide was prepared by the method described in Example 6, except that natural graphite produced in Madagascar was used as graphite particles. The weight ratio of graphite to copper in the resulting copper-coated graphite powder was 89:11. Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A nonionic dispersant was added to the copper oxide-deposited graphite composite produced by the above-mentioned method, and the mixture was dried with polytetrafluoroethylene (after drying, the weight ratio of the copper oxide-deposited graphite composite to polytetrafluoroethylene was: (77:23) was applied to both sides of the copper foil current collector in the form of a paste by adding the dispersion liquid. 60 ℃
, Heat-treated at 240 ° C, pressed, and dried at 200 ° C under reduced pressure to remove moisture, and used as the negative electrode. This negative electrode has a surface area of 8 cm ² and an electrode thickness of 83
μm (the thickness of the current collector is 50 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 387 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 359 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 5 The material described in Example 7 was used for the graphite composite with copper oxide.

After drying, a negative electrode was prepared in the same manner as in Example 7, except that the weight ratio of the graphite composite with copper oxide and polytetrafluoroethylene was changed to 63:37. The surface area of the produced negative electrode was 8 cm ² , and the thickness was 88 μm.

This negative electrode was evaluated by the method described in Example 7.

As a result, the discharge capacity in the second cycle was 362 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 344 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 8 The material described in Example 7 was used for the graphite composite attached with copper oxide.

After drying, a negative electrode was prepared in the same manner as in Example 1 except that the weight ratio of the graphite composite with copper oxide and polytetrafluoroethylene was changed to 97: 3. The produced negative electrode had a surface area of 8 cm ² and a thickness of 76 μm (the thickness of the current collector was 50 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 415 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 351 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 6 The material described in Example 7 was used as the graphite composite attached with copper oxide.

After drying, a negative electrode was prepared by the method described in Example 1 except that the weight ratio of the graphite composite with copper oxide and polytetrafluoroethylene was 99.5: 0.5. It was peeled off from the conductor.

Table 2 shows the results of Examples 7 and 8 and Comparative Examples 5 and 6.
Shown in From this and Examples 1 to 6, it was found that the optimal weight ratio of the graphite composite adhering to copper oxide and the binder was 99: 1 to 70:30.

[0086]

[Table 2]

Example 9 As graphite particles, artificial graphite (flaky, particle size 7 μm, d ₀₀₂₎
Is 0.336 nm, Lc is 22 nm, La is 13 nm,
An R-value of 0.1 and a specific surface area of 10 m ² / g) were used to prepare a copper oxide-adhered graphite composite by the method described in Example 6. The weight ratio of graphite to copper in the resulting copper-coated graphite powder was 89:11. Further, when the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite was performed,
It was found to be graphite and cupric oxide.

The copper oxide-adhered graphite composite prepared by the above-described method is prepared by dissolving polyvinylidene fluoride in N, N-dimethylformamide in advance (the weight ratio of N, N-dimethylformamide to polyvinylidene fluoride is:
1.5: 0.05. ) And in the form of a paste. At this time, the weight ratio after drying of the graphite composite with copper oxide and polyvinylidene fluoride was mixed so as to be 91: 9. This paste was applied on both surfaces of a stainless steel foil current collector. After drying at 65 ° C and heat-treating at 155 ° C,
What was pressed and further dried under reduced pressure at 160 ° C. for removing water was used as a negative electrode. This negative electrode has a surface area of 8c.
m ² , the electrode thickness is 72 μm (the current collector thickness is 50 μm)
m).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 441 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 416 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 10 Modified graphite (flaky, particle size 7 μm, d ₀₀₂₎ was used as graphite particles.
Is 0.336 nm, Lc is 22 nm, La is 13 nm,
An R-value of 0.1 and a specific surface area of 10 m ² / g) were used to prepare a copper oxide-adhered graphite composite by the method described in Example 6. The weight ratio of graphite to copper in the copper-coated graphite powder obtained at this time was 98.1: 1.9 (graphite / (graphite + copper) = 0.10).
981). Further, when the powdered X-ray wide-angle diffraction measurement of the produced graphite composite attached with copper oxide was performed, it was found to be graphite and cupric oxide.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 70 μm (the current collector had a thickness of 5 μm).
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 397 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 374 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 11 Copper oxide was prepared by the method described in Example 10 except that the weight ratio of graphite to copper in the copper-coated graphite powder was 95: 5 (graphite / (graphite + copper) = 0.95). An attached graphite composite was prepared.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 78 μm (the thickness of the current collector was 5 μm).
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 536 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 501 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 12 Copper oxide was prepared by the method described in Example 10 except that the weight ratio of graphite to copper in the copper-coated graphite powder was 91: 9 (graphite / (graphite + copper) = 0.91). An attached graphite composite was prepared.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 76 μm (the thickness of the current collector was 5 μm).
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 425 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 412 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 13 Example 10 was repeated except that the weight ratio of graphite to copper in the copper-coated graphite powder was 83:17 (graphite / (graphite + copper) = 0.83).
A copper oxide-adhered graphite composite was prepared by the method described in (1).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 80 μm (the thickness of the current collector was 5 μm).
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 420 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 405 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 14 Example 10 was repeated except that the weight ratio of graphite to copper in the copper-coated graphite powder was 77:23 (graphite / (graphite + copper) = 0.77).
A copper oxide-adhered graphite composite was prepared by the method described in (1).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The surface area of the produced negative electrode was 8 cm ² , and the thickness was 79 μm (the thickness of the current collector was 5 μm).
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 381 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 368 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 15 Example 10 was repeated except that the weight ratio of graphite to copper in the copper-coated graphite powder was 71:39 (graphite / (graphite + copper) = 0.71).
A copper oxide-adhered graphite composite was prepared by the method described in (1).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 83 μm (the current collector had a thickness of 5 μm).
0 μm).

This negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 373 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 358 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 16 Example 10 was repeated except that the weight ratio of graphite to copper in the copper-coated graphite powder was 67:33 (graphite / (graphite + copper) = 0.67).
A copper oxide-adhered graphite composite was prepared by the method described in (1).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 81 μm (the thickness of the current collector was 5 μm).
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 375 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 349 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 17 The weight ratio of graphite to copper in the copper-coated graphite powder was 62.5: 3.
A copper oxide-adhered graphite composite was prepared by the method described in Example 10 except that the ratio was 7.5 (graphite / (graphite + copper) = 0.625).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 85 μm (the thickness of the current collector was 5 cm ²⁾ .
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 371 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 346 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 7 Modified graphite (flaky, particle size 7 μm, d ₀₀₂ 0.336 n
m, Lc is 22 nm, La is 13 nm, R value is 0.1,
Specific surface area 10m ² / g only (weight ratio graphite / (graphite +
A negative electrode was produced by the method described in Example 10 using (copper) = 1). The surface area of the produced negative electrode was 8 cm ² , and the thickness was 77 μm (the thickness of the current collector was 50 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 361 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 340 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 8 Copper oxide was obtained by the method described in Example 10 except that the weight ratio of graphite to copper in the copper-coated graphite powder was 99: 1 (graphite / (graphite + copper) = 0.99). An attached graphite composite was prepared.

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 72 μm (the current collector had a thickness of 5 μm).
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 364 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 332 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 9 Example 10 was repeated except that the weight ratio of graphite to copper in the copper-coated graphite powder was 59:41 (graphite / (graphite + copper) = 0.59).
A copper oxide-adhered graphite composite was prepared by the method described in (1).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 87 μm (the current collector had a thickness of 5 μm).
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 352 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 316 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 10 The copper-coated graphite powder had a weight ratio of graphite to copper of 53:47 (graphite / (graphite + copper) = 0.53).
A copper oxide-adhered graphite composite was prepared by the method described in (1).

A negative electrode was manufactured by the method described in Example 1 using the graphite composite with copper oxide. The produced negative electrode had a surface area of 8 cm ² and a thickness of 86 μm (the current collector had a thickness of 5 μm).
0 μm).

The negative electrode was evaluated by the method described in Example 1.

As a result, the discharge capacity in the second cycle was 320 mA per unit volume of the electrode (excluding the volume of the current collector).
h, the discharge capacity at the 10th cycle was 304 mAh per unit volume of the electrode (excluding the volume of the current collector).

Table 3 shows the results of Examples 10 to 17 and Comparative Examples 2 and 7 to 10. FIG. 1 shows the relationship between the weight ratio of graphite to the mixture of graphite and plated copper and the discharge capacity per unit volume (excluding the volume of the current collector) of the electrode in the second cycle. Thus, the weight ratio of graphite to plated copper is preferably in the range of 98.5: 1.5 to 62:38, and more preferably in the range of 98.5: 1.5 to 75:25. It turned out to be particularly preferred.

[0139]

[Table 3]

Example 18 Production of Negative Electrode The material described in Example 7 was used for the graphite composite with copper oxide.

A nonionic dispersant was added to the copper oxide-deposited graphite composite produced by the above-mentioned method, and the mixture was mixed with polytetrafluoroethylene (after drying, the weight ratio of the copper oxide-deposited graphite composite to polytetrafluoroethylene was changed to , 91: 9) was applied to a nickel three-dimensional porous current collector, and the paste was applied to the holes. This is dried at 60 ° C, 240 ° C
After heat treatment with, press and further 200 to remove moisture
What was dried under reduced pressure at ℃ was used as a negative electrode. This negative electrode is a pellet having a diameter of 14.5 mm and an electrode thickness of 0.41 mm.

Preparation of Positive Electrode Lithium carbonate and cobalt carbonate, and antimony trioxide were mixed in a ratio of lithium atom to cobalt atom and antimony atom of 1:
Each was weighed so as to be 0.95: 0.05, mixed in a mortar, baked in air at 900 ° C. for 20 hours, and then ground in a mortar to obtain an active material powder. This active material had a composition of Li _0.98 Co _0.95 Sb _0.05 O ₂ . The thus obtained positive electrode active material is mixed with acetylene black, a nonionic dispersant is added, and polytetrafluoroethylene (after drying, the weight ratio of the positive electrode active material to acetylene black and polytetrafluoroethylene is , 100: 10: 5), and the resulting mixture was made into a paste by applying to a titanium mesh current collector. This is dried at 60 ° C., 24
After heat treatment at 0 ° C, press, and 2 to remove moisture
What was dried under reduced pressure at 00 ° C. was used as a positive electrode. This positive electrode is a pellet having a diameter of 14.5 mm and an electrode thickness of 0.93 mm.

Assembling of Battery As shown in FIG. 2, the positive electrode current collector 2 was previously attached to the inner bottom surface by welding, and the positive electrode 3 was crimped to the positive electrode can 1 on which the insulating packing 8 was placed. Next, a microporous polypropylene separator 7 was placed on top of this, and 1 mol / l LiPF ₆ was added to a 2: 1: 3 mixed solvent of ethylene carbonate, propylene carbonate, and diethyl carbonate.
Is dissolved in the electrolytic solution. On the other hand, the negative electrode current collector 5 is welded to the inner surface of the negative electrode can 4, and the negative electrode 6 is pressed to the negative electrode current collector. Next, the negative electrode 6 is placed on the separator 7 and the positive electrode can 1 and the negative electrode can 4 are caulked with the insulating packing 8 interposed therebetween, thereby producing a coin-type battery.

Evaluation of Battery The produced coin-type battery was charged at a charging / discharging current of 2 mA, and reached a charging upper limit voltage of 4.2 V. After reaching 4.2 V, the battery was charged at a constant voltage of 4.2 V, and the charging time was 12 hours. did. The capacity was measured with the lower limit voltage of the discharge being 2.5 V. The evaluation was performed on the discharge capacity of the battery.

As a result, the average voltage in the discharge was 3.7
V, and the discharge capacity at the second cycle was 19 mAh, 1
The discharge capacity at the 0th cycle was 17 mAh.

Comparative Example 11 A negative electrode was produced by the method described in Example 18 using only natural graphite produced in Madagascar. The size and thickness of the produced negative electrode are the same. The positive electrode and the battery were also prepared in Example 18.
Was prepared by the method described in (1).

This battery was evaluated by the method described in Example 18.

As a result, the average voltage in the discharge was 3.7
V, and the discharge capacity in the second cycle was 14 mAh, 1
The discharge capacity at the 0th cycle was 13 mAh.

Example 19 Production of Negative Electrode The material described in Example 11 was used for the graphite composite with copper oxide.

A nonionic dispersant was added to the copper oxide-deposited graphite composite produced by the above method, and the mixture was dried with polytetrafluoroethylene (after drying, the weight ratio of the copper oxide-deposited graphite composite to polytetrafluoroethylene was changed to , 91: 9) was applied to a nickel three-dimensional porous current collector, and the paste was applied to the pores. This is dried at 60 ° C, 240 ° C
After heat treatment with, press and further 200 to remove moisture
What was dried under reduced pressure at ℃ was used as a negative electrode. This negative electrode is a pellet having a diameter of 14.5 mm and an electrode thickness of 0.37 mm.

Preparation of Positive Electrode Lithium carbonate and manganese dioxide were each weighed so that the ratio of lithium atoms to manganese atoms was 1.1: 2, mixed in a mortar, and then in air at 900 ° C. for 3 days. The active material LiM is fired and then crushed in a mortar.
A powder of n ₂ O ₄ was obtained. The positive electrode active material thus obtained is mixed with a conductive material (a mixture of acetylene black and expanded graphite at a weight ratio of 2: 1), a nonionic dispersant is added, and polytetrafluoroethylene (after drying, The weight ratio between the positive electrode active material and the conductive material, polytetrafluoroethylene,
100: 10: 5. The dispersion liquid prepared in (1) was added to form a paste, which was applied onto a titanium mesh current collector. This was dried at 60 ° C., heat-treated at 240 ° C., pressed, and dried under reduced pressure at 200 ° C. to remove moisture, and used as a positive electrode. This positive electrode has a diameter of 1
The pellets are 4.5 mm and the thickness of the electrodes is 1.0 mm.

Battery assembly Ethylene carbonate and γ-butyrolactone were used in the electrolyte.
1m in a 3: 1: 3 mixed solvent with diethyl carbonate
A coin-type battery was produced by the method described in Example 18 except that a solution in which ol / l of LiPF ₆ was dissolved was used.

Evaluation of Battery The produced coin-type battery was charged at a charging / discharging current of 1 mA, reached a charging upper limit voltage of 4.2 V, reached 4.2 V, was charged at a constant voltage of 4.2 V, and was charged for 24 hours. did. The capacity was measured with the lower limit voltage of the discharge being 2.5 V. The evaluation was performed on the discharge capacity of the battery.

As a result, the average voltage in the discharge was 3.7
V, and the discharge capacity in the second cycle was 20 mAh, 1
The discharge capacity at the 0th cycle was 15 mAh.

Comparative Example 12 Modified graphite (flaky, particle size 7 μm, d ₀₀₂ 0.336 n
m, Lc is 22 nm, La is 13 nm, R value is 0.1,
A negative electrode was produced by the method described in Example 19 using only the specific surface area (10 m ² / g). The size of the prepared negative electrode,
The thickness is the same. A positive electrode and a battery were also prepared by the method described in Example 19.

This battery was evaluated by the method described in Example 19.

As a result, the average voltage in the discharge was 3.7
V, and the discharge capacity in the second cycle was 13 mAh, 1
The discharge capacity at the 0th cycle was 12 mAh.

Table 4 shows the results of Examples 18 and 19 and Comparative Examples 11 and 12. Thus, a high-capacity lithium secondary battery can be manufactured using the negative electrode including the graphite composite with copper oxide.

[0159]

[Table 4]

[0160]

The negative electrode according to the present invention, that is, the electrode obtained by mixing a copper oxide-adhered graphite composite obtained by adhering copper oxide to graphite capable of intercalating and deintercalating lithium and a binder, has a large discharge capacity. Is shown. Further, since a lower potential of the negative electrode can be used, a lithium secondary battery with a high battery voltage can be provided. Therefore, an excellent lithium secondary battery can be provided using the negative electrode according to the present invention.

[Brief description of the drawings]

FIG. 1 shows the weight ratio of graphite to a mixture of graphite and plated copper and the unit volume of an electrode in the second cycle (excluding the volume of the current collector) in Examples 10 to 17 and Comparative Examples 2 and 7 to 10. FIG. 4 is a diagram showing a relationship between discharge capacities per square brackets).

FIG. 2 shows Examples 18 and 19 of the present invention and Comparative Examples 11 and 1
FIG. 3 is an explanatory view of a battery manufactured in Step 2.

[Explanation of symbols]

 Reference Signs List 1 positive electrode can 2 positive electrode current collector 3 positive electrode 4 negative electrode can 5 negative electrode current collector 6 negative electrode 7 separator 8 insulating packing

Continued on the front page (72) Inventor Naoto Nishimura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Kazuo Yamada 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72 ) Inventor Tetsuya Yoneda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-5-258773 (JP, A) JP-A-6-325575 (JP, A) 4-179069 (JP, A) JP-A-1-279578 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/02-4/04 H01M 4/36-4 / 62 H01M 10/40

Claims (5)

(57) [Claims] 1. A battery comprising a positive electrode, a negative electrode and a non-aqueous ion conductor, wherein the negative electrode is made of graphite capable of intercalating / deintercalating lithium ions as a main component of a negative electrode active material, and the graphite particles A lithium secondary battery that is an electrode in which a binder and a composite having copper oxide attached on all or a part of its surface are mixed. 2. The particle size of graphite as a negative electrode active material is 80 μm.
The lithium secondary battery according to claim 1, wherein: 3. A composite in which copper oxide is adhered on the surface of graphite particles, after coating copper on a part of the surface of the graphite particles,
The lithium secondary battery according to claim 1, which is a composite produced by a production method of producing copper oxide by performing an oxidation treatment. 4. The lithium secondary battery according to claim 3, wherein the weight ratio of graphite to copper is from 98.5: 1.5 to 62:38 by weight of graphite and copper. 5. The binder is polytetrafluoroethylene,
The lithium secondary battery according to claim 1, wherein the lithium secondary battery is polyvinylidene fluoride, polyethylene, polypropylene, a polyolefin-based polymer, or a synthetic rubber.