JPH06349482A - Lithium secondary battery - Google Patents

Abstract

PURPOSE:To provide a lithium secondary battery having a large discharge capacity and high battery voltage by using the graphite having a specific nature for the main constituent of the negative electrode active material of a negative electrode, and mixing a complex stuck with copper oxide on the surfaces of all or part of graphite grains and a binder to form an electrode. CONSTITUTION:Lithium ion intercalatable/deintercalatable graphite is prepared. Electroless copper plating is applied to graphite powder to obtain copper-coated graphite powder. It is oxidized in air, and the prescribed process is applied to obtain a negative electrode. A positive electrode current collector 2 is welded to the inner bottom face of a positive electrode can 1, an insulating packing 8 is put in the positive electrode can 1 to connect a positive electrode 3 by pressure. A separator 7 is put on it, and it is impregnated with an electrolyte. A negative electrode current collector 5 is welded inside a negative electrode can 4, and a negative electrode 6 is connected by pressure to obtain a coin battery. The grain size of the graphite is preferably set to 80mum or below, and the ratio between the graphite and the coated copper is preferably set to the range of 98.5:1.5-62:38wt.%.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art With the miniaturization and power saving of electronic devices,
Secondary batteries using alkali metals such as lithium are drawing attention. When an alkali metal such as lithium is used alone for the negative electrode, charge and discharge are repeated, that is, the dissolution-precipitation process of the alkali metal causes dendrites (dendrites) to grow on the dissolution-precipitation surface of the metal and grow. Therefore, there is a problem that a short circuit inside the battery is induced by penetrating the separator and coming into contact with the positive electrode. It was found that when an alkali metal alloy was used for the negative electrode for the secondary battery instead of the alkali metal, the generation of dendrites was suppressed and the charge / discharge cycle characteristics were improved, compared to when using a single substance. However, the use of alloys does not completely prevent the generation of dendrites, and may cause a short circuit inside the battery. In recent years, instead of using a dissolution-precipitation process or a dissolution-precipitation-diffusion process of a metal such as an alkali metal or an alloy thereof for a negative electrode, carbon or carbon using an absorption-desorption process of an alkali metal ion is used. Organic materials such as conductive polymers have been developed. As a result, the generation of dendrites that occur when an alkali metal or an alloy thereof is used does not occur in principle, and the problem of short circuit inside the battery is drastically reduced.

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 a battery electrode.

When carbon is used as the negative electrode active material, the amount of lithium inserted between the layers of carbon is 1 atom of lithium to 6 atoms of carbon, that is, C6Li is the upper limit, and per unit weight of carbon at that time. Capacity of 372 mAh / g.
Carbon has a wide range of structures from what is called amorphous carbon to graphite, and the size of the hexagonal mesh surface of carbon and the arrangement are different depending on the starting material, the manufacturing method, and the like. Examples of the carbon material conventionally used as the negative electrode active material include, for example, JP-A-62-90863, JP-A-62-122066, JP-A-63-213267, and JP-A-1-2.
There are those disclosed in JP-A-04361, JP-A-2-82466, JP-A-3-252053, JP-A-3-285273, JP-A-3-289068 and the like.

None of these carbons reaches the above theoretical capacity, and even if the capacity is large to a certain extent, the potential during deintercalation of lithium increases linearly, and the actual battery system In some cases, the above structure does not show a sufficient capacity in the usable potential range, and it is not possible to manufacture a negative electrode having a satisfactory negative electrode capacity when manufacturing a battery. In addition, when an electrode is produced, the true density of the carbon material is also necessary, 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. In the examples of JP-A-62-90863, JP-A-2-
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 9068, and none of these fibrous carbons reaches the theoretical capacity described above, and the negative electrode capacity that is satisfactory for manufacturing a battery is obtained. It is not possible to produce a negative electrode having In addition, JP-A-63-2455
Although the pyrolytic carbon by the vapor phase method as shown in 5 shows high charge and discharge stability, it is difficult to produce a thick film electrode and it is difficult to obtain a high capacity electrode by this production method.

In contrast, 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, it is a measurement of a small current although the discharge capacity of the theoretical capacity is obtained. It is not satisfactory in terms of practical use. Further, it is disclosed in JP-A-4-112455, JP-A-4-115457, JP-A-4-115458, JP-A-4-237971, JP-A-5-28996 and the like that a graphite material is used as a negative electrode active material. Since the above theoretical capacity is not reached, it is not possible to produce a negative electrode that has a satisfactory negative electrode capacity when producing a battery.

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

As in JP-A-4-184863, a metal (nickel, copper) coating is formed on a carbon material, or JP-A-4-184863.
By using a mixed negative electrode of carbon and metal (at least one kind of metal that does not alloy with lithium) such as 259964, cycle characteristics can be improved and high rate discharge after high-temperature standing can be improved. No fundamental improvement in negative electrode capacity can be expected.

As in JP-A-3-216960, by forming lithium on the surface of the carbon body so as not to block the pores, a large current can be taken out, and the secondary life with improved cycle life and safety can be obtained. A battery can be obtained, and as in JP-A-4-39864, by using a negative electrode in which a carbonaceous material is impregnated with an alloy capable of forming an alloy with an active material, the electrode capacity is large, the charge / discharge cycle characteristics are excellent, and the self-discharge Although a secondary battery with improved characteristics can be obtained,
There is a problem that the number of steps in manufacturing the electrode increases.

As described in JP-A-4-179049, by using a composite negative electrode of a conductive polymer and a metal and / or carbon-based material, a flexible negative electrode for a battery having a long cycle life can be provided, but the charge and discharge capacity is reduced. There's a problem.

[0011]

DISCLOSURE OF THE INVENTION As described above,
Even when various carbon materials and graphite materials are used as the negative electrode active material, the theoretical capacity (372 mAh / g) has not been reached, and a negative electrode having a satisfactory negative electrode capacity cannot be manufactured. However, although the graphite material can basically charge and discharge the theoretical capacity, there is a problem that the charging / discharging current value used at that time is not a practically usable current value. In addition, the reaction of inserting and desorbing lithium ions has an average voltage of 2 V (Li / Li
+) Is used a negative electrode mixed with a chalcogen compound and a carbonaceous material capable of inserting and releasing lithium ions, but the problem of low charge and discharge voltage and low energy density, carbon-lithium alloy In a composite negative electrode with a metal that does not form a metal, it is not possible to bring about a fundamental improvement in the capacity of the negative electrode, and in a composite negative electrode 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 charge / discharge capacity in a composite negative electrode of a conductive polymer and a metal and / or a carbon-based material. Further, as 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 that is not involved in the reaction.

In view of the above-mentioned circumstances, the present invention provides an electrode in which graphite capable of intercalating / deintercalating lithium is mixed with copper oxide and a binder to provide a high capacity electrode. It is an object of the present invention to provide a graphite mixed negative electrode which can reduce the number of manufacturing steps, and further a high capacity, high voltage lithium secondary battery.

[0013]

According to the present invention, a positive electrode,
In a battery composed of a negative electrode and a non-aqueous ionic conductor,
The negative electrode is composed of graphite capable of intercalating / deintercalating lithium ions as a main component of the negative electrode active material, and a composite material and a binder in which copper oxide is attached on the surface of all or part of the graphite particles. There is provided a lithium secondary battery in which the electrodes are mixed.

The negative electrode of the present invention is oxidized by applying oxidation treatment after coating the surface of all or a part of graphite particles capable of intercalation / deintercalation of lithium ions as a negative electrode active material. It is produced by using a composite produced by a production method for producing copper and mixing it with a binder. At this time, the negative electrode current collector may be used to fabricate a negative electrode and the negative electrode current collector integrated with each other.

The graphite used as the main component of the negative electrode active material used in the present invention has an average interplanar spacing (d ₀₀₂ ) of (002) planes of 0.335 to 0.340 nm by X-ray wide angle diffraction method,
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. A factor affecting the capacity and the charge / discharge potential is the physical properties related to the layered structure of carbon. For the physical properties related to the layered structure of carbon (00
2) The interplanar spacing (d ₀₀₂ ), that is, the interlayer distance, and the crystallite size. Since the crystallinity becomes higher, the potential during deintercalation of lithium becomes closer to the potential of lithium, so that it is expected that a higher capacity carbon body electrode can be obtained. Therefore, when the battery capacity that can be used when the lithium secondary battery is assembled is taken into consideration, the average interplanar spacing (d ₀₀₂ ) of the (002) planes by the X-ray wide angle diffraction method is 0.335 to 0.340 nm. Preferably there is. Crystallite thickness in the (002) plane direction (L
In c), when the thickness is 10 nm or less, the crystallinity is poor, and 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 plane direction is 10 nm or less, the crystallinity is poor. Therefore, when assembled as a lithium secondary battery, the usable battery capacity becomes small, which is not practical.

In graphite as a main component of the negative electrode active material used in the present invention, 1 by 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. When it is larger than 0.4, the crystallinity becomes low, and the potential at the time of deintercalation of lithium becomes higher due to the potential of lithium. Therefore, when assembled as a lithium secondary battery, the usable battery capacity is It becomes small and not practical.

As graphite which can be used, artificial graphite obtained from easily graphitizable carbon such as natural graphite, quiche graphite, petroleum coke or coal pitch coke or expanded graphite satisfying the above-mentioned physical properties. Graphite, and the shape is spherical, scaly,
It may be fibrous or crushed products thereof, but spherical, scaly or crushed products thereof are preferred.

When graphite is prepared as a negative electrode, the particle size of graphite is preferably 80 μm or less. The particle size is a value obtained as a particle size having a peak in the particle size distribution obtained by measuring the volume-based particle size distribution. 80
When graphite having a particle size larger than μm is used, the contact area with the electrolytic solution becomes small, so that the diffusion of lithium in the particles,
Problems such as reduction of reaction sites occur, and problems occur in charging and discharging with a large current.

As a method for producing a composite in which copper oxide is attached to the surface of graphite particles, a method of forming copper oxide by subjecting a part of the surface of graphite particles to copper and then subjecting it to oxidation treatment There is. Among these, as a method of coating the surface of the graphite particles with copper, electroless plating method of copper, vapor deposition method utilizing heating evaporation by keeping copper in a high reduced pressure, sputtering method using heating evaporation and ion bombardment, etc. Is mentioned. Of these, the electroless plating method is preferable in terms of cost and work. For electroless plating of copper, there is, for example, an alkaline bath using formaldehyde, hydrazine or the like as a reducing agent. It is also possible to use a commercially available electroless copper plating bath.

Oxidizing treatment is carried out after coating with copper. As the oxidizing treatment, a method of oxidizing with a gaseous oxidizing agent such as air, oxygen or ozone, a liquid oxidizing agent such as hydrogen peroxide, Examples include, but are not limited to, a method of oxidizing with water having dissolved oxygen, a salt of oxo acid (nitrous acid, permanganic acid, chromic acid, dichromic acid, chloric acid, hypochlorous acid, etc.). 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 it is approximately 60
It is 0 ° C or higher. Therefore, the temperature is preferably 600 ° C. or lower. In addition, even in the following oxidation treatment using air and oxygen at 600, the type of graphite, the oxidation time, the oxygen partial pressure,
The surface of the graphite is oxidized, and functional groups such as a carboxyl group, a lactone, a hydroxyl group, and a carbonyl group are generated, although it depends on the ratio of graphite to copper and the like. From this, 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 copper oxide-adhered graphite composite, the ratio of graphite and copper constituting the copper-coated graphite composite is determined by the kind and particle size of graphite or the coating of copper. The weight ratio of graphite to copper is preferably 98.5: 1.5 to 62:38, although it depends on the method. More preferably, it is 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 reaction sites of lithium ions are reduced during charging / discharging of graphite, and the lithium secondary battery is assembled. However, the battery capacity that can be used becomes small, which is not practical.

The negative electrode is formed by mixing the above-mentioned composite material in which copper oxide is adhered on the surface of all or part of the graphite particles and a binder. As the binder, a fluorine-based polymer such as polytetrafluoroethylene or polyvinylidene fluoride, a polyolefin-based polymer such as polyethylene or polypropylene, a synthetic rubber or the like can be used, but the binder is not limited thereto. This mixing ratio is such that the weight ratio of the composite in which copper oxide is adhered to the surface of all or part of the graphite particles and the binder is 99: 1 to 70:30.
Can be If the binder is larger than 70:30, the resistance or polarization of the electrodes becomes large and the discharge capacity becomes small, so that a practical lithium secondary battery cannot be manufactured. If the binder is less than 90: 1, the binding ability will be lost, and it will be difficult to manufacture the battery because the active material will fall off and the mechanical strength will decrease. In the production of the negative electrode, it is preferable to perform heat treatment at a temperature around the melting point of each binder in order to improve the binding property.

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

As the ionic conductor, for example, an organic electrolytic solution, a polymer solid electrolyte, an inorganic solid electrolyte, a molten salt or the like can be used, and among them, the organic electrolytic solution can be preferably used. As a solvent for the organic electrolytic solution, esters such as propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate and γ-butyrolactone, substituted tetrahydrofuran such as tetrahydrofuran and 2-methyltetrahydrofuran, dioxolane, diethyl ether , Dimethoxyethane, diethoxyethane,
Examples include ethers such as methoxyethoxyethane, dimethyl sulfoxide, sulfolane, methylsulfolane, acetonitrile, methyl formate, methyl acetate, and the like.
Used as one kind or as a mixed solvent of two or more kinds. Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium borofluoride, lithium phosphorus fluoride, lithium arsenic hexafluoride, lithium trifluoromethanesulfonate, lithium halides and lithium chloroaluminate. One of these or Two or more kinds are mixed and used. An electrolyte solution 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.

The positive electrode in the lithium secondary battery of the present invention includes LiCoO ₂ , LiNiO ₂ and L of this series.
_{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 is based on the active material 1
The conductive material may be 5 to 50 parts by weight and the binder may 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 the conductive material is not limited thereto. The binder may be, but not limited to, a fluorine-based polymer such as polytetrafluoroethylene or polyvinylidene fluoride, a polyolefin-based polymer such as polyethylene or polypropylene, or a synthetic rubber. 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 electrodes 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 (the weight part changes depending on the kind of the mixed conductive material), the amount of the active material contained in the electrode is reduced, so that the discharge capacity as the positive electrode becomes small. If the binding material is less than 1 part by weight, the binding ability will be lost, and if it is more 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 the production of the positive electrode, it is preferable to perform 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, the electrode obtained by mixing the binder with the composite in which copper oxide is adhered on the surface of all or part of graphite particles capable of intercalating / deintercalating lithium is It has a high capacity. This is because a complex oxide of lithium and copper that reversibly progresses was formed in the electrochemically reduced copper oxide. Further, 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 that forms an alloy with lithium. Furthermore, a chalcogen compound having a high capacity and a lithium ion insertion / desorption reaction with an average voltage of 2 V (Li / Li ⁺ ) or less was mixed with a carbonaceous material capable of lithium ion insertion / desorption. Since a lower potential of the negative electrode can be used as compared with a battery using the negative electrode, a lithium secondary battery with 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 The present invention will now be described in more detail by way of examples.

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

Example 1 Preparation of Copper Oxide-Adhered Graphite Composite Graphite particles of a 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 used to produce natural graphite (scaly form) from Madagascar. , Particle size 11 μm, d ₀₀₂
Is 0.337 nm, Lc is 27 nm, La is 17 nm,
An R value of 0 and a specific surface area of 8 m ² / g) were used, and this was subjected to electroless copper plating. Electroless copper plating was performed by the following method. First, the graphite powder is dipped in ethyl alcohol and dried, and then dipped in a sensitizing treatment liquid (mixture of 30 g / l SnCl ₂ .2H ₂ O and 20 ml / l concentrated hydrochloric acid) to further activate the treatment liquid (0 0.4 g / l PbCl ₂ · 2H ₂ O and 3 ml
Pretreatment was carried out by immersing in a mixed solution of concentrated hydrochloric acid (1 / l). Next, 10 g / g of pretreated graphite powder
1 CuSO ₄ .5H ₂ O, 50 g / l potassium sodium tartrate, 10 g / l sodium hydroxide, 10 ml
A solution prepared by dissolving 1 / l of 37% formalin 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. It was dried at 60 ° C. The weight ratio of graphite to copper of 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 complex to which copper oxide was attached. When powder X-ray wide-angle diffraction measurement of this copper oxide-adhered graphite complex was performed, diffraction lines derived from graphite and diffraction lines derived from cupric oxide were observed.

Preparation of Negative Electrode A nonionic dispersant was added to the copper oxide-adhered graphite composite prepared by the above-described method, and polytetrafluoroethylene (after drying, the copper oxide-adhered graphite composite and polytetrafluoroethylene were mixed). The weight ratio is 87:13.) A dispersion liquid was added to form a paste, and the paste was applied to both surfaces of the copper foil current collector. This is dried at 60 ℃, 240
After heat treatment at ℃, press and press for 20 minutes to remove water.
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 (current collector thickness of 50 μm).

Evaluation of Negative Electrode A lead wire was used to collect current from a copper current collector, which was used as an electrode for evaluation. For evaluation, a three-pole method was used, and lithium was used for the counter electrode and the reference electrode. The electrolytic solution was prepared 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
It was first charged to 0 V at a current density of 0.1 mA / cm ² , and then discharged to 1.5 V at the same current. Two
After the first time, charge and discharge were repeated in the same potential range and current density, 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 As graphite particles, modified graphite (scale-like, particle size 8 μm, d ₀₀₂
Is 0.337 nm, Lc is 17 nm, La is 12 nm,
R value is 0.1 and specific surface area is 9 m ² / g), 0.06 m
ol / l CuSO ₄ .5H ₂ O, 0.3 mol / l E
DTA, 0.4 mol / l formaldehyde, 170
mg / l 7-iodo-8-hydroxyquinoline-5-
A solution in which sulfonic acid is dissolved is added with sodium hydroxide
A copper oxide-adhered graphite complex was produced by the method described in Example 1 except that plating was performed at 75 ° C. in an electroless copper plating bath prepared to H12.8, and oxidation treatment was performed at 400 ° C. in air for 30 minutes. . The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 85:15. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 71 μm (the thickness of the collector was 5
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 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 as graphite particles (scale-like, 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 of _{Cu (NO 3) 2 · 3H} 2 O, and dissolved sodium bicarbonate 10 g / l, sodium potassium tartrate 30 g / l, sodium hydroxide 20 g / l, and a 37% formalin 100 ml / l Using an electroless copper plating bath in which the solution is adjusted to pH 11.5 with sodium hydroxide,
A copper oxide-adhered graphite complex was prepared by the method described in Example 1 except that the oxidation treatment was performed in oxygen at 200 ° C. for 24 hours. The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 91: 9. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

A negative electrode was produced by the method described in Example 1 using this copper oxide-adhered graphite composite. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 88 μm (the thickness of the current collector is 5
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 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 Artificial graphite as graphite particles (scaly, 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 potassium sodium tartrate, 45 g
Example 1 except that an electroless copper plating bath prepared by mixing a solution prepared by dissolving 1 g / l sodium hydroxide and 15 g / l sodium carbonate immediately before use was subjected to an oxidation treatment in air at 350 ° C. for 1 hour. A copper oxide-adhered graphite composite was prepared by the method described. The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 89:11. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 132 μm (current collector thickness is 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 as graphite particles (spherical, particle size 6 μm, d ₀₀₂ 0.339 nm, Lc 25 nm, La 13 nm, R
The value is 0.4 and the specific surface area is 8 m ² / g), and MAC-100 (manufactured by Okuno Chemical Industries Co., Ltd.) and M are used as a pretreatment liquid.
Using AC-200 (Okuno Pharmaceutical Co., Ltd.), MA
Described in Example 1 except that a two-liquid type electroless copper plating bath of C-500A and MAC-500B (manufactured by Okuno Chemical Industries Co., Ltd.) was used and oxidation treatment was performed at 70 ° C. for 15 hours in water containing dissolved oxygen. A copper oxide-adhered graphite composite was produced by the method described above. The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 96: 4. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite complex revealed that it was graphite, cuprous oxide, and cupric oxide.

A negative electrode was prepared by the method described in Example 1 using this copper oxide-adhered graphite composite. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 71 μm (the thickness of the collector was 5
0 μm).

This negative electrode was described in Example 1 except that 1 mol / l of lithium perchlorate was dissolved in a 2: 1: 2 mixed solvent of ethylene carbonate, propylene carbonate and diethyl carbonate as the electrolytic solution. It evaluated by the method.

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 prepared by the method described in Example 1 using only natural graphite produced in Madagascar. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 85 μm (the thickness of the current collector was 50 μm).
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 from Madagascar was used as the main negative electrode active material, and this was mixed with commercially available cupric oxide (particle size: 27 μm) in a mortar at a weight ratio of 80:20 to obtain a nonionic dispersion. Agent, and a dispersion liquid of polytetrafluoroethylene (after drying, a mixture of graphite and cupric oxide and the weight ratio of polytetrafluoroethylene is 87:13) is added and the paste is added. The shaped material was applied to both surfaces of a copper foil current collector. This is dried at 60 ℃, heat treated at 240 ℃, pressed, and 200 ℃ to remove water.
The one dried under reduced pressure in 1 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).

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 335 mAh per unit volume of the electrode (excluding the volume of the current collector).

Comparative Example 3 Mesocarbon microbeads carbonized as carbon particles at 1000 ° C. (spherical, particle size 6 μm, d ₀₀₂ is 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), MAC as pretreatment liquid
-100 (Okuno Pharmaceutical Co., Ltd.) and MAC-2
00 (Okuno Pharmaceutical Co., Ltd.), MAC-50
Example 1 except that a two-liquid type electroless copper plating bath (Okuno Pharmaceutical Co., Ltd.) of 0A and MAC-500B was used.
A copper oxide-adhered carbon composite was prepared by the method described in 1.
The weight ratio of carbon to copper of the copper-coated carbon powder produced at this time was 81:19. Further, powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered carbon composite revealed that it was carbon and cupric oxide.

Using this copper oxide-adhered carbon composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 68 μm (the thickness of the current collector is 5
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 176 mA per unit volume of the electrode (excluding the volume of the current collector).
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, it was found that a high discharge capacity was obtained when the negative electrode containing the copper oxide-adhered graphite composite was used.

[0061]

[Table 1]

Example 6 As graphite particles, artificial graphite (scale-like, particle size 77 μm, d
₀₀₂ is 0.337 nm, Lc is 26 nm, La is 14 n
m, R value is 0.1, specific surface area is 2 m ² / g), MAC-100 (manufactured by Okuno Chemical Industry Co., Ltd.) and MAC-200 (manufactured by Okuno Pharmaceutical Industry Co., Ltd.) are used as pretreatment liquids, and MAC- A copper oxide-adhered graphite complex was produced by the method described in Example 1 except that a two-liquid type electroless copper plating bath (made by Okuno Chemical Industries Co., Ltd.) of 500A and MAC-500B was used. The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 87:13. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The surface area of the produced negative electrode is 8 cm ² , and the thickness is 227 μm (the thickness of the current collector is 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 Artificial graphite as graphite particles (scaly, particle size 117 μm, d
₀₀₂ is 0.337 nm, Lc is 25 nm, La is 17 n
m, R value was 0.1, and a specific surface area of 1 m ² / g) was used, and a copper oxide-adhered graphite composite was prepared by the method described in Example 6. The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 88:12. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 305 μm (current collector thickness is 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).

The results of Examples 1 to 6 and Comparative Example 4 are shown in Table 1. From this, it was found that the particle size of graphite should be 80 μm or less.

Example 7 A copper oxide-adhered graphite composite was prepared by the method described in Example 6 except that natural graphite from Madagascar was used as the graphite particles. The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 89:11. Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

A nonionic dispersant was added to the copper oxide-adhered graphite composite prepared by the above-mentioned method, and polytetrafluoroethylene (after drying, the weight ratio of the copper oxide-adhered graphite composite and polytetrafluoroethylene was 77:23) was added to form a paste, and the paste was applied to both surfaces of the copper foil current collector. 60 ℃
The negative electrode was dried in a vacuum oven, heat-treated at 240 ° C., pressed, and dried under reduced pressure at 200 ° C. to remove water. 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).

The 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 As the copper oxide-adhered graphite composite, the material described in Example 7 was used.

After drying, a negative electrode was produced by the method described in Example 7 except that the weight ratio of the copper oxide-adhered graphite composite and polytetrafluoroethylene was changed to 63:37. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 88 μm.

The 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 as the copper oxide-adhered graphite composite.

After drying, a negative electrode was produced by the method described in Example 1 except that the weight ratio of the copper oxide-adhered graphite composite and polytetrafluoroethylene was set to 97: 3. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 76 μm (the thickness of the current collector is 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 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 As the copper oxide-adhered graphite composite, the material described in Example 7 was used.

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

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 optimum weight ratio of the copper oxide-adhered graphite composite and the binder was 99: 1 to 70:30.

[0086]

[Table 2]

Example 9 As graphite particles, artificial graphite (scale-like, particle size 7 μm, d ₀₀₂
Is 0.336 nm, Lc is 22 nm, La is 13 nm,
A copper oxide-adhered graphite complex was produced by the method described in Example 6 except that the R value was 0.1 and the specific surface area was 10 m ² / g). The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 89:11. Further, 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.

Polyvinylidene fluoride dissolved in N, N-dimethylformamide in advance in the copper oxide-adhered graphite composite prepared by the above-mentioned method (the weight ratio of N, N-dimethylformamide and polyvinylidene fluoride is
It is 1.5: 0.05. ) And made into a paste. At this time, the copper oxide-adhered graphite composite and polyvinylidene fluoride were mixed so that the weight ratio after drying was 91: 9. This paste was applied on both sides of a stainless foil current collector. After drying at 65 ° C and heat treatment at 155 ° C,
What was pressed and further dried under reduced pressure at 160 ° C. to remove water was used as a negative electrode. This negative electrode has a surface area of 8c
m ² , electrode thickness 72 μm (current collector thickness 50 μm
m).

The 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 as graphite particles (scaly, particle size 7 μm, d ₀₀₂
Is 0.336 nm, Lc is 22 nm, La is 13 nm,
A copper oxide-adhered graphite complex was produced by the method described in Example 6 except that the R value was 0.1 and the specific surface area was 10 m ² / g). The weight ratio of graphite to copper of the copper-coated graphite powder produced at this time was 98.1: 1.9 (graphite / (graphite + copper) = 0.
981). Further, the powder X-ray wide-angle diffraction measurement of the produced copper oxide-adhered graphite composite revealed that it was graphite and cupric oxide.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 70 μm (the thickness of the collector was 5
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 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 graphite powder coated with copper was 95: 5 (graphite / (graphite + copper) = 0.95). An attached graphite composite was prepared.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. 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
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 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 obtained 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.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode had a surface area of 8 cm ² and a thickness of 76 μm (the thickness of the collector was 5
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 425 mA per unit volume of the electrode (excluding the volume of the current collector).
The discharge capacity at 10th cycle was 412 mAh per unit volume of the electrode (excluding the volume of the current collector).

Example 13 Example 10 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.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 80 μm (the thickness of the current collector was 5
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 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.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode had a surface area of 8 cm ² and a thickness of 79 μm (the thickness of the collector was 5
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).
The discharge capacity at 10th cycle was 368 mAh per unit volume of the electrode (excluding the volume of the current collector).

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

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode had a surface area of 8 cm ² and a thickness of 83 μm (the thickness of the collector was 5
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 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 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.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 81 μm (the thickness of the current collector is 5
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).
The discharge capacity at 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 produced by the method described in Example 10 except that the value was 7.5 (graphite / (graphite + copper) = 0.625).

Using this copper oxide-adhered graphite complex, a negative electrode was prepared by the method described in Example 1. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 85 μm (the thickness of the collector was 5
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 (scaly, particle size 7 μm, d ₀₀₂ is 0.336 n
m, Lc is 22 nm, La is 13 nm, R value is 0.1,
Specific surface area of 10 m ² / g only (weight ratio graphite / (graphite +
A negative electrode was produced by the method described in Example 10 using copper) = 1). The prepared negative electrode has a surface area of 8 cm ² and a thickness of 77 μm (current collector thickness is 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 prepared 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.

Using this copper oxide-adhered graphite composite, a negative electrode was produced by the method described in Example 1. The prepared negative electrode has a surface area of 8 cm ² and a thickness of 72 μm (the thickness of the current collector is 5
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 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.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The prepared negative electrode had a surface area of 8 cm ² and a thickness of 87 μm (the thickness of the collector was 5
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).
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 Example 10 except that the weight ratio of graphite to copper in the copper-coated graphite powder was 53:47 (graphite / (graphite + copper) = 0.53).
A copper oxide-adhered graphite composite was prepared by the method described in 1.

Using this copper oxide-adhered graphite composite, a negative electrode was prepared by the method described in Example 1. The surface area of the prepared negative electrode was 8 cm ² , and the thickness was 86 μm (the thickness of the current collector was 5
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. For these, the relationship between the weight ratio of graphite to the mixture of graphite and plated copper and the discharge capacity per unit volume of the electrode in the second cycle (excluding the volume of the current collector) is shown in FIG. From this, the weight ratio of graphite to plated copper is preferably in the range of 98.5: 1.5 to 62:38, and preferably in the range of 98.5: 1.5 to 75:25. It turned out to be particularly preferable.

[0139]

[Table 3]

Example 18 Preparation of Negative Electrode The material described in Example 7 was used for the copper oxide-adhered graphite composite.

A nonionic dispersant was added to the copper oxide-adhered graphite composite prepared by the above-mentioned method, and polytetrafluoroethylene (after drying, the weight ratio of the copper oxide-adhered graphite composite and polytetrafluoroethylene was , 91: 9) to form a paste, which was applied to a nickel three-dimensional porous current collector, and the paste was applied into the pores. Dry this at 60 ℃, 240 ℃
After heat treatment at 200 ° C, press and then 200 for moisture removal.
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 are used in a ratio of lithium atom to cobalt atom and antimony atom of 1:
Each was weighed 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 positive electrode active material thus obtained 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) was added to form a paste, and the paste was applied onto a titanium mesh current collector. This is dried at 60 ℃, 24
After heat treatment at 0 ° C, press and further 2 to remove water.
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 3 was pressure-bonded to the positive electrode can 1 in which the positive electrode current collector 2 was previously attached to the inner bottom surface by welding and the insulating packing 8 was placed. Next, a microporous polypropylene separator 7 was placed on this, and 1 mol / l of LiPF ₆ was added to a mixed solvent of ethylene carbonate, propylene carbonate and diethyl carbonate in a ratio of 2: 1: 3.
Is impregnated with the dissolved electrolyte. 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 pressure-bonded to the negative electrode current collector. Next, the negative electrode 6 is stacked on the separator 7 and the positive electrode can 1 and the negative electrode can 4 are caulked with an insulating packing 8 interposed therebetween to manufacture a coin-type battery.

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

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

Comparative Example 11 A negative electrode was prepared by the method described in Example 18 using only natural graphite produced in Madagascar. The size and thickness of the manufactured negative electrode are the same. The positive electrode and the battery are also as in Example 18.
It was prepared by the method described in.

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

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

Example 19 Preparation of Negative Electrode The material described in Example 11 was used for the copper oxide-adhered graphite composite.

A nonionic dispersant was added to the copper oxide-adhered graphite composite prepared by the above-described method, and polytetrafluoroethylene (after drying, the weight ratio of the copper oxide-adhered graphite composite and polytetrafluoroethylene was , 91: 9) to form a paste, which was applied to a nickel three-dimensional porous current collector, and the paste was applied into the pores. Dry this at 60 ℃, 240 ℃
After heat treatment at 200 ° C, press and then 200 for moisture removal.
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 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. By firing and then crushing in a mortar, the active material LiM
A powder of n ₂ O ₄ was obtained. The positive electrode active material thus obtained was mixed with a conductive material (a mixture of acetylene black and expanded graphite in a weight ratio of 2: 1), a nonionic dispersant was added, and polytetrafluoroethylene (after drying, The weight ratio of the positive electrode active material, the conductive material, and polytetrafluoroethylene is
It is 100: 10: 5. The dispersion liquid of 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 further dried under reduced pressure at 200 ° C. to remove water, and used as the positive electrode. This positive electrode has a diameter of 1
It is a pellet having a thickness of 4.5 mm and an electrode thickness of 1.0 mm.

-Battery assembly Ethylene carbonate and γ-butyrolactone were used as electrolytes.
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 obtained by dissolving ol / l of LiPF ₆ was used.

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

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

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

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

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

The results of Examples 18 and 19 and Comparative Examples 11 and 12 are shown in Table 4. From this, it is possible to manufacture a high-capacity lithium secondary battery by using the negative electrode containing the copper oxide-adhered graphite composite.

[0159]

[Table 4]

[0160]

INDUSTRIAL APPLICABILITY The negative electrode according to the present invention, that is, the electrode obtained by mixing a binder with a copper oxide-adhered graphite composite in which copper oxide is adhered to lithium intercalation / deintercalation graphite has a large discharge capacity. Indicates. Moreover, since a lower potential of the negative electrode can be used, a lithium secondary battery having a high battery voltage can be provided. Therefore, the negative electrode according to the present invention can be used to provide an excellent lithium secondary battery.

[Brief description of drawings]

FIG. 1 is a weight ratio of graphite to a mixture of graphite and plated copper in Example 10 to 17 and Comparative Examples 2 and 7 to 10 and a unit volume of an electrode at the second cycle (excluding the volume of the current collector). FIG. 3 is a diagram showing a relationship of discharge capacity per unit.

FIG. 2 shows Examples 18 and 19 of the present invention and Comparative Examples 11 and 1.
It is explanatory drawing of the battery produced in 2.

[Explanation of symbols]

 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Naoto Nishimura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Kazuo Yamada 22-22 Nagaike-cho, Abeno-ku, Osaka Prefecture, Osaka Incorporated (72) Inventor Tetsuya Yoneda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture

Claims (5)

[Claims] 1. A battery comprising a positive electrode, a negative electrode and a non-aqueous ionic conductor, wherein the negative electrode is composed 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, which is an electrode in which a composite material in which copper oxide is adhered on all or part of the surface and a binder are mixed. 2. The particle size of graphite, which is the 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 a part of the surface of graphite particles with copper,
The lithium secondary battery according to claim 1, which is a composite manufactured by a manufacturing method in which copper oxide is generated by performing an oxidation treatment. 4. The lithium secondary battery according to claim 3, wherein the ratio of graphite to copper coated is 98.5: 1.5 to 62:38 by weight ratio of graphite to copper. 5. The binder is polytetrafluoroethylene,
The lithium secondary battery according to claim 1, which is polyvinylidene fluoride, polyethylene, polypropylene, a polyolefin-based polymer, or synthetic rubber.