JP2014239068A - Positive electrode for lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode for achieving a lithium battery which is high in specific capacity, excellent in discharge characteristics capable of acquiring large current and less in deterioration.SOLUTION: Since a conductive assistant is obtained by forming and coating carbon on a particle surface of a lithium metal oxide, by a chemical vapor deposition method for forming and coating carbon on a lithium metal oxide particle as a positive electrode active material, a raw material for forming carbon is used as solution of an organic compound, inert gas or low reactive gas is supplied as carrier gas together with the solution of the organic compound to a positive electrode active material particle to have a positive electrode for a lithium battery to form carbon. The solution of the organic compound contains carbon and oxygen in a compound molecule.

Description

  The present invention relates to a positive electrode for a lithium battery that can realize excellent battery characteristics.

  In recent years, the demand for batteries has increased due to the downsizing, high performance, and portability of various electronic devices. Accordingly, the improvement and development of batteries are becoming increasingly active. New application areas for batteries are also expanding.

  The nickel-metal hydride battery (hereinafter referred to as “high energy density”) with the rapid spread of mobile devices since around 1990 in the consumer secondary battery market, which was only a lead battery and a nickel cadmium battery (hereinafter referred to as “Ni / Cd battery”). , Ni / MH batteries) and lithium ion batteries (hereinafter referred to as Li ion batteries) have been developed and spread to occupy a significant share (see Non-Patent Document 1).

  However, electronic devices typified by mobile phones and notebook PCs frequently undergo model changes, and each time they are required to have higher energy density by making them more multifunctional and smaller.

  In recent years, as stipulated by the Kyoto Protocol (COP3) and the like, environmental preservation, reduction of environmental burden, and effective use of material energy have been screamed, and it has become mandatory. Regarding secondary batteries, strict management of regulated substances and restrictions on the use of batteries containing such substances have come to be demanded, and recycling of battery constituent materials has also been demanded (for example, non-patent documents). 2). In order to reduce the environmental impact and ensure reliability, it is one of the important measures to suppress the progress of battery deterioration as much as possible and to make effective use of material energy by extending the life.

  Fundamental measures to improve battery characteristics and suppress battery deterioration include exploration and development of high-performance battery materials, modification thereof, and optimization of battery construction methods.

In the Li-ion battery, in addition to the modification of LiCoO ₂ , LiNiO ₂ , spinel LiMn ₂ O ₄ , Co, Ni, Mn ternary lithium metal oxide Li (Co _{x Mn y Ni z) O 2} (x + y + z = 1), to such an olivine LiFePO ₄ has been developed, graphite materials also negative, such as Si-based or Sn-based alloys have been studied (non-Patent Document 3 and non Patent Document 4).

  As for the positive electrode, it is a matter of course that a positive electrode active material having excellent characteristics as described above is adopted, but the positive electrode is not only a positive electrode active material, but also a conductive aid for ensuring sufficient conductivity, and these Considering that it is a porous electrode composed of a binder for binding and forming particles of the conductive agent, the conductivity, particle shape, and positive electrode activity of the conductive aid for smoothly moving the electrons accompanying the electrode reaction The mixed state of the substance and the conductive additive is also a condition for improving characteristics and suppressing deterioration.

  However, in reality, it is very difficult to mix and disperse properly a positive electrode active material and a conductive auxiliary agent having a large specific gravity, and the content of the conductive auxiliary agent is inevitably increased, and the positive electrode active material which affects the battery reaction is inevitably increased. Often the content of the material was relatively reduced and the properties were not sufficiently improved. In addition, repetitive expansion and contraction due to insertion / desorption of lithium into / from the positive electrode active material accompanying charging / discharging of the battery deteriorates the contact state between the positive electrode active material and the conductive additive, thereby promoting deterioration of battery characteristics (Non-Patent Document) There was a problem of 5).

OHM Co., Ltd., “Special Feature Leaping Secondary Battery World Part II”, OHM, 2006.02, p. 32 (2006). Japan Battery Manufacturers Association homepage, http: // www. baj. or. jp / recycle / industrial. html, 2008.5.26. Okada Shigeto, “Lithium-ion Secondary Battery Second Edition”, Chapter 3, Nikkan Kogyo Shimbun, pp. 35-37 (2000). Nikkei Electronics 2005.2.28, pp. 34-35 (2005). Mitsuharu Tabuchi, Tomonari Takeuchi, Masahiro Shikano, Kuniaki Tsuji, “Fabrication of Fe-containing Li2MnO3-based cathode and examination of high output by carbon composite”, Battery Technical Committee Document 19-07, Battery Technical Committee (2007).

  An object of the present invention is to provide a positive electrode for improving the above-mentioned present situation, realizing a lithium battery having a large specific capacity, excellent discharge characteristics capable of acquiring a large current, and little deterioration.

  The positive electrode for a lithium battery according to one embodiment of the present invention is lithium, which is a positive electrode active material capable of electrochemically inserting and desorbing lithium ions in a lithium battery containing a nonaqueous organic solvent in which a lithium salt is dissolved as a solute as an electrolyte. A positive electrode for a lithium battery comprising a metal oxide, a carbon material of a conductive auxiliary agent, and a binder material for binding these particles, wherein the conductive auxiliary agent is a particle of the lithium metal oxide. Carbon is formed and coated on the surface, and carbon is formed and coated on the lithium metal oxide particles, which are the positive electrode active material, by chemical vapor deposition. Such a chemical vapor deposition method forms an organic compound solution as a raw material for forming carbon, and supplies the positive active material particles with an inert gas or a low-reactive gas as a carrier gas to form the carbon. The organic compound in the solution contains carbon and oxygen in the compound molecule.

  In one embodiment of the present invention, the solution of the organic compound may be any of methanol, ethanol, ethylene glycol, acetone, formic acid, or acetic acid.

  In one embodiment of the present invention, the weight ratio of carbon serving as the conductive auxiliary agent may be 4 wt% or more and 20 wt% or less with respect to the weight of the positive electrode active material.

  In one aspect of the present invention, with respect to the positive electrode for a lithium battery, the lithium metal oxide, the conductive additive, and the binder material constituting the positive electrode are preliminarily determined to have a weight ratio on the lithium metal oxide particles that are the positive electrode active material. The carbon battery is coated with a carbon material serving as a conductive aid so that the carbon weight ratio is in the range of 1.5 wt% or more and 15 wt% or less with respect to the weight of the positive electrode active material. The positive electrode active material formed by coating an agent, the amount of carbon necessary to reach a predetermined weight of the conductive auxiliary agent, and the binder material may be mixed.

  In one embodiment of the present invention, in the method for forming carbon on the positive electrode active material particles, the temperature at which the positive electrode active material particles are allowed to stand to form carbon is 350 ° C. or higher and 600 ° C. or lower, and the temperature is increased to such a temperature. The carrier gas is supplied at the time of starting or before that, the environment for forming carbon on the positive electrode active material particles is placed in a deoxygenated state, and the organic compound solution as a raw material is supplied to the positive electrode active material particles with respect to the carrier. It may be installed in the gas supply direction, and the installation amount may be 1 ml or more per 1 g of the positive electrode active material.

  In one embodiment of the present invention, the positive electrode active material includes one or more of chloride, sulfide, carbonate, or acetate of Fe, Ni, Co, Cu, Sn, Zn, Cr, In, and Sb. After the metal is added in advance so as to be 0.01 wt% or more and 5 wt% or less with respect to the weight of the positive electrode active material, carbon may be formed and coated on the positive electrode active material particles.

  In one embodiment of the present invention, the composite material in which carbon is formed on the surface of the lithium metal oxide that is the positive electrode active material is maintained in the air at a temperature of 300 ° C. to 500 ° C. for 30 minutes to 2 hours. Thus obtained material may be used as the positive electrode material.

It is the figure which showed the relationship between the specific capacity per positive electrode active material weight of a lithium battery, and an electric current value as an example which shows the effect of the positive electrode composite material of this invention. As an example showing the effect of the positive electrode composite material of the present invention, the relationship between the carbon ratio of the positive electrode composite material and the specific capacity per weight of the positive electrode active material of the lithium battery having the positive electrode formed of the positive electrode composite material and the binder was shown. FIG. As an example showing the effect of the positive electrode composite material of the present invention, the formed carbon ratio of the positive electrode composite material and the specific capacity per weight of the positive electrode active material of the lithium battery having the positive electrode formed of the positive electrode composite material, the carbon material, and the binder It is the figure which showed the relationship. It is the figure which showed the change of the specific capacity per positive electrode active material weight accompanying the charging / discharging cycle of the lithium battery using the positive electrode composite material produced from the different raw material filling amount as an example which shows the effect of the positive electrode composite material of this invention. Relationship between the amount of Ni catalyst supported on the positive electrode active material in the positive electrode composite material produced as an example showing the effect of the positive electrode composite material of the present invention and the specific capacity per weight of the positive electrode active material of a lithium battery using the positive electrode composite material FIG. It is the figure which showed the change of the specific capacity per positive electrode active material weight accompanying the charging / discharging cycle of the lithium battery using the positive electrode composite material produced from the different catalyst carrying amount as an example which shows the effect of the positive electrode composite material of this invention. It is the figure which showed the relationship between the heat processing temperature of a positive electrode composite material, and the specific capacity per positive electrode active material weight of the lithium battery using this positive electrode composite material as an example which shows the effect of the positive electrode composite material of this invention. It is the figure which showed the relationship between the heat processing time of a positive electrode composite material, and the specific capacity per positive electrode active material weight of the lithium battery using this positive electrode composite material as an example which shows the effect of the positive electrode composite material of this invention.

  The reason why the positive electrode having such a configuration is effective is that the contact resistance between the positive electrode active material and the conductive auxiliary agent is greatly increased by fixing all or part of the conductive auxiliary agent directly on the surface of the positive electrode active material particles. It can be interpreted that the transfer of electrons necessary for the electrode reaction occurring on the surface of the positive electrode active material proceeds very smoothly. Moreover, it can be interpreted that it is possible to effectively arrange a limited conductive auxiliary agent for securing conductivity by fixing the positive electrode active material to the surface.

  As a negative electrode of a lithium battery, in addition to using lithium metal as a direct electrode, natural graphite, graphitized spherules, amorphous carbon, PIC (Pseudo Isotropic Carbon), FMC (Fine Mosaic Carbon), polyacene, polyparaphenylene, etc. Carbon materials that can insert and release lithium, such as carbon obtained by firing a polymer compound, Sn-based alloys, Si-based alloys, and the like can be selected. However, the material is not limited to these as long as the battery reaction of the lithium battery is smoothly performed.

The positive electrode active material for a lithium battery, LiCoO _2, spinel LiMnO _2, LiNiO _2, but olivine type _{LiFePO 4, LiCo x Mn y Ni} z O 2 (x + y + z = 1) lithium metal oxides such as is contemplated, lithium The substance is not limited to these as long as the battery reaction of the battery is smoothly performed.

As the electrolytic _solution, as _{LiClO 4, LiAsF 6, LiPF 6} , LiBF 4, LiSbF 4, LiN (SO 2 CF 3) 2, LiCF 3 solute of lithium salts such as SO _3, ethylene carbonate, propylene carbonate, 1 , 2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane, etc. As long as the battery reaction of the lithium battery is smoothly performed, the material is not limited thereto.

  In one form of the present invention, it is proposed that the weight ratio of carbon serving as a conductive additive directly formed on the surface of the positive electrode active material particles is 4 wt% or more and 20 wt% or less with respect to the weight of the positive electrode active material.

  The conductive auxiliary agent plays a role of facilitating the movement of electrons involved in the battery reaction, and when the weight ratio of carbon directly formed on the surface of the positive electrode active material particles is less than 4 wt%, the smooth transfer of electrons is inhibited, The current for practical use cannot be obtained. However, if the conductive additive exceeds 20 wt%, the content ratio of the positive electrode active material decreases, the capacity itself decreases, and it cannot be used for a practical battery.

  According to one embodiment of the present invention, a method is proposed in which the conductive auxiliary agent is contained by directly forming on the positive electrode active material particles, but the mixing ratio of the positive electrode active material and the conductive auxiliary agent is strictly determined according to battery specifications, And under conditions such as it is difficult to strictly control the amount of carbon formed on the positive electrode active material particles, the amount of carbon directly formed on the positive electrode active material particles is measured in advance, A method of mixing different kinds of conductive assistants to a specified mixing ratio is also proposed. In this case, it is also proposed that the weight ratio of carbon directly formed on the surface of the positive electrode active material particles is 1.5 wt% or more and 15 wt% or less with respect to the weight of the positive electrode active material. Although this method increases the number of manufacturing steps, the carbon directly formed on the surface of the positive electrode active material particles does not lose a good contact state even with repeated expansion and contraction of the active material due to charge and discharge. It is possible to provide the same stable battery characteristics as when all are formed directly on the positive electrode active material.

  In one embodiment of the present invention, a chemical vapor deposition method is a method in which carbon is directly formed and coated on lithium metal oxide particles that are a positive electrode active material in order to produce the carbon / positive electrode active material composite material. Proposing to select a solution of an organic compound as a raw material for forming the carbon and to supply the positive electrode active material particles with an inert gas or a low-reactive gas as a carrier gas to form the carbon To do.

  The solution of the organic compound as the raw material is methanol, ethanol, ethylene glycol, acetone, formic acid, acetic acid, etc., which are the cheapest and can be used easily, but contain carbon C and oxygen O, which are not explosive, in the compound molecule. Any organic solution that volatilizes moderately at temperature can be used as long as carbon that fulfills the function as a conductive additive that facilitates battery reaction can be formed on the surface of the positive electrode active material particles, and is not limited thereto.

  The reason why such an organic compound is used as a raw material is based on the presence of oxygen O contained in the molecule, which has a certain volatility, can generate carbon with high reactivity and efficiently by containing carbon C in the molecule. This is because reductive decomposition of the lithium metal oxide can be suppressed.

  In one embodiment of the present invention, the raw material that is volatilized at a set temperature is filled quantitatively in a non-reactive container such as a ceramic boat so that the organic compound solution of the raw material is 1 ml per 1 g of the positive electrode active material. In order to stably supply the surface of the positive electrode active material particles as the base material, a boat of the raw material solution is arranged in the direction in which the carrier gas is supplied to the base material.

  The position of the container for the raw material solution is not particularly limited as long as the volatilized raw material is effectively supplied to the vicinity of the surface of the positive electrode active material particles as the base material. Place it in a place where all or part of it is exposed.

  As the carrier gas, an inert gas such as argon or nitrogen, or a low-reactive gas can be used. However, the positive electrode active material particles that are quantitatively and stably serve as the base material without inhibiting the progress of the carbon-forming reaction. If the raw material can be supplied on the surface, it is not limited to these gases.

  In one embodiment of the present invention, when carbon is formed on the surface of the positive electrode active material particles by supplying such raw materials, the temperature (reaction temperature) for leaving the positive electrode active material particles to form carbon directly is 350 ° C. or more and 600 ° C. We propose that:

Details of the reaction that forms carbon on the surface of the positive electrode active material particles are unknown, but for example, when methanol is used as a raw material,
2CH ₃ OH → C + CH ₄ + 2H ₂ O (1)
When ethanol is used as a raw material,
C ₂ H ₅ OH → C + CH ₄ + H ₂ O (2)
Can be considered. If acetic acid is used as a raw material, CH ₃ COOH → 2C + 2H ₂ O (3)
Is assumed.

However, when the reaction temperature is less than 350 ° C., for example, when the raw material is methanol,
CH ₃ OH → CO + 2H ₂ (4)
Such a reaction makes it difficult for the carbon formation reaction to proceed. On the other hand, when the reaction temperature exceeds 600 ° C., for example, when the positive electrode active material is LiCoO ₂ , 2CH ₃ OH → 2C + 2H ₂ + 2H ₂ O (5)
2H ₂ + 2LiCoO ₂ → Li ₂ O + CoO + 2H ₂ O (6)
Although the carbon formation rate is increased by such a reaction, the cathode active material may be decomposed at the same time, which is not preferable.

  According to one aspect of the present invention, oxygen is removed from the reaction system at a time when the temperature rise is started from room temperature to such a temperature, or before the carrier gas is supplied into the quartz tube which is a reaction field and reaches a predetermined temperature. The carbon forming reaction is efficiently performed at the temperature. The supply amount of the carrier gas until the temperature of the tubular furnace reaches the set temperature is not particularly limited as long as the oxygen in the quartz tube is purged until the set temperature is reached. To preferably 30 ml / min. If it is less than 30 ml per minute, oxygen removal in the reaction system may not be sufficiently performed until the predetermined temperature is reached, which is not preferable.

  In one form of this invention, the installation amount of the raw material for causing the carbon forming reaction is set to 1 ml or more per 1 g of the positive electrode active material particles as a base. If it is less than 1 ml / g, carbon formation is not sufficient, which is not preferable.

  One form of the present invention also proposes the use of a catalyst in order to effectively promote carbon formation on the surface of the positive electrode active material particles. Namely, Fe, Ni, Co, Cu, Sn, Zn, Cr, In, and Sb are used as catalysts for carbon formation, and one or more of chlorides, sulfides, carbonates or acetates of these metals are used. In addition, after the metal catalyst is fixed on the surface of the positive electrode active material particles, carbon growth is performed on the surface of the positive electrode active material particles. In one embodiment of the present invention, the amount of the metal catalyst fixed on the surface of the positive electrode active material particles is proposed to be 0.01 wt% or more and 5 wt% or less per weight of the positive electrode active material.

For example, when nickel is used as a catalyst and methanol is used as a raw material, the chloride, sulfide, carbonate or acetate of the metal expected as a catalyst is given.
2CH ₃ OH → C + CH ₄ + 2H ₂ O (1)
In nickel chloride,
2NiCl ₂ + CH ₄ → 2Ni + 4HCl + C (7)
In nickel sulfate,
2NiSO ₄ + CH ₄ → 2Ni + 2H ₂ O + 2SO ₂ + CO ₂ (8)
In nickel carbonate,
2Ni (CO ₃ ) ₂ + CH ₄ → 2Ni + 2H ₂ O + 5CO ₂ (9)
In nickel acetate,
2Ni (OCOCH ₃ ) ₂ + CH ₄ → 2Ni + 2H ₂ O + 8C (10)
The reaction changes to Ni metal as a catalyst.

  When the amount of the catalyst metal is less than 0.01 wt%, the amount of the catalyst metal supported on the surface of the positive electrode active material particles is insufficient and carbon formation does not proceed effectively. As the amount of catalyst supported on the material surface increases, the amount of carbon formation does not increase, which is not preferable.

  Hereinafter, the positive electrode for a lithium battery according to an embodiment of the present invention and a method for producing the same will be described with reference to examples, but the present invention is not limited thereto.

[Example 1]
As a positive electrode active material for a lithium battery, 5 g of LiCoO ₂ powder was weighed in a ceramic boat, and the sample boat was placed so as to be located in the quartz tube and at the center of the tubular furnace. Further, another ceramic boat was filled with 5 ml of methanol and installed in a quartz tube at a position where the tip of the boat was placed at the end of the tubular furnace in front of the sample boat. One end of this quartz tube was connected to a gas supply tube, and the other end was connected to a gas exhaust hose.

Argon (hereinafter referred to as Ar) gas as a carrier gas was supplied to the quartz tube at 50 ml / min for 5 minutes to purge oxygen in the quartz tube. The tube furnace was heated while continuing the supply of Ar gas. When the furnace temperature reached 450 ° C., the Ar gas was increased to 100 ml / min and supplied for 30 minutes. When the predetermined time is reached, the supply of Ar gas is returned to 50 ml / min and the heater in the tubular furnace is stopped to lower the furnace temperature. After 2 hours, the supply of Ar gas was stopped, the sample boat was taken out from the quartz tube, and the powder in the boat was weighed. As a result, the carbon formed LiCoO ₂ on powder was 4.68Wt% to LiCoO ₂ powder.

After the obtained powder was lightly stirred in an agate mortar, 4.7511 g was weighed, transferred to an agate mortar and mixed for 8 minutes with a rake machine, and 0.1477 g of Teflon (registered trademark) powder was added thereto. After mixing for 2 minutes to form a rough sheet, the sheet was formed into a sheet with a roll molding machine, and then punched out with a punch to produce a positive electrode. The produced positive electrode was 92.6 wt% LiCoO _2, 4.3 wt% carbon, 3 wt% Teflon, a thickness of about 0.57 mm, and a weight of 0.19 g to 0.20 g.

For comparison, a Ni net was placed on a ceramic boat, installed in a quartz tube, and the quartz tube was installed in a cylindrical furnace. First, Ar gas is supplied at 50 ml / min using Ar gas as the carrier gas and the raw material is acetylene gas. After 5 minutes, the temperature of the cylindrical furnace is started to rise to 600 ° C. When the set temperature is reached, 150 ml of Ar gas is supplied. / Min and supply of 30 ml / min of acetylene gas (hereinafter C ₂ H ₂ gas) was started. After 10 minutes, the supply of C ₂ H ₂ gas was stopped and the Ar gas supply was returned to 50 ml / min. After about 2 hours, when the furnace temperature became 100 ° C. or less, the Ar gas supply was stopped, and the sample boat was taken out to obtain 0.1586 g of carbon having substantially the same shape as the carbon on the positive electrode active material produced in this patent. . LiCoO ₂ 94.6 wt%, the carbon 12 wt%, Teflon powder 6 wt%, each weighed out to a total of 3.004 g, first mixing LiCoO ₂ and AB (acetylene black) for 8 minutes with a trickling machine, Teflon powder was added thereto and mixed for 2 minutes, and punched with a punch in the same manner to produce a positive electrode.

Produced 2032 type coin cells A and B consisting of the produced positive electrode, lithium metal as the negative electrode, 1M LiPF ₆ -ethylene carbonate / dimethyl carbonate (volume ratio 1/1) as the electrolyte, and Dura-Gard 2502 as the separator, and the battery characteristics were improved. evaluated. The characteristics of the test batteries A and B are as follows: a test battery is installed in a constant temperature bath at 21 ° C., and the charge / discharge voltage range is 3.0 V to 4.3 V, the charge current value is 1 mA, and the charge and discharge are performed by an automatic charge / discharge test device. The test was performed under the condition of providing a 10-minute pause in between.

  FIG. 1 shows the capacity of each of the test batteries A and B at each discharge current value.

  That is, FIG. 1 is a graph showing the discharge current value on the horizontal axis and the specific capacity of the test battery (discharge capacity per weight of the positive electrode active material) on the vertical axis, and curve 1 in FIG. 1 indicates the test battery A of the present invention. Curve 2 shows the characteristics of test battery B as a comparative example.

  As can be seen from FIG. 1, the test battery A of the present invention exhibited excellent battery characteristics with a large specific capacity at a low current and a large specific capacity even at a large current.

  On the other hand, in the test battery B shown as a comparative example, it was found that the specific capacity in the whole discharge current tested was smaller than that of the test battery A of the present invention, which was not preferable.

[Example 2]
As a positive electrode active material for a lithium battery, 5 g of LiCoO ₂ powder was weighed in a ceramic boat, and the sample boat was placed so as to be located in the quartz tube and at the center of the tubular furnace. Furthermore, one or two other ceramic boats were filled with 10 ml of methanol or acetic acid as a raw material, and placed in a quartz tube at a position where the tip of the boat was placed at the end of the tubular furnace in front of the sample boat.

LiCoO ₂ was prepared in the same manner as in Example 1 except that argon (hereinafter referred to as Ar) gas was used as the carrier gas, the furnace temperature was set to 450 ° C., and the set time (reaction time) was set as shown in Table 1. Carbon was formed on the particle surface.

  The obtained composite material powder was lightly stirred in an agate mortar, and 4.85 g was weighed out, transferred to an agate mortar and mixed for 6 minutes with a milling machine, and 0.15 g of Teflon powder was added thereto for another 2 minutes. After mixing and forming into a rough sheet and forming into a sheet with a roll forming machine, a positive electrode was produced by punching with a punch.

A 2032 type coin cell composed of the produced positive electrode, lithium metal as the negative electrode, 1M LiPF ₆ -ethylene carbonate / dimethyl carbonate (volume ratio 1/1) as the electrolyte, and Duraguard 2502 as the separator was produced, and battery characteristics were evaluated. The test battery was evaluated by installing the test battery in a constant temperature bath at 21 ° C., charging it to 4.3 V with a current value of 1 mA (0.75 mA / cm ² per positive electrode) using an automatic charge / discharge test device, and resting for 10 minutes. Thereafter, the battery was discharged to 3.0 V at a current value of 2.5 mA (1.88 mA / cm ² ) and rested for 10 minutes. This charge / discharge operation was repeated twice to evaluate the second discharge capacity.

  FIG. 2 shows the discharge capacity of the test battery.

That is, FIG. 2 shows the weight ratio of formed carbon to LiCoO ₂ of the composite material on the horizontal axis, and the specific capacity (discharge capacity per weight of the positive electrode active material) of the test battery using the composite material corresponding to the vertical axis as the positive electrode. FIG. 2 shows a curve 3 showing a change in specific capacity with respect to the amount of carbon formed.

As apparent from FIG. 2, when the proportion of carbon directly formed on the surface of the positive electrode active material particles proposed by the present invention is in the range of 4 wt% to 20 wt% with respect to ₂ wt% of LiCoO, the specific capacity is 100 mAh / g or more. It has become clear that it exhibits excellent properties.

  On the other hand, it has been found that a weight ratio of less than 4 wt% or more than 20 wt% is not preferable because it does not show a sufficient specific capacity.

[Example 3]
As a positive electrode active material for a lithium battery, 5 g of LiCoO ₂ powder was weighed in a ceramic boat, and the sample boat was placed so as to be located in the quartz tube and at the center of the tubular furnace. Further, another ceramic boat was filled with 5 ml of methanol and installed in a quartz tube at a position where the tip of the boat was placed at the end of the tubular furnace in front of the sample boat. One end of the quartz tube is connected to a gas supply tube, and the other end is connected to a gas exhaust hose.

LiCoO ₂ was prepared in the same manner as in Example 1 except that argon (hereinafter referred to as Ar) gas was used as the carrier gas, the furnace temperature was set to 450 ° C., and the set time (reaction time) was set as shown in Table 1. Carbon was formed on the particle surface.

Separately, a Ni net was placed on a ceramic boat, this was installed in a quartz tube, and the quartz tube was installed in a cylindrical furnace. First, Ar gas is supplied at 50 ml / min using Ar gas as the carrier gas and the raw material is acetylene gas. After 5 minutes, the temperature of the cylindrical furnace is started to rise to 600 ° C. When the set temperature is reached, 150 ml of Ar gas is supplied. / Min and supply of 30 ml / min of acetylene gas (hereinafter C ₂ H ₂ gas) was started. After 10 minutes, the supply of C ₂ H ₂ gas was stopped and the Ar gas supply was returned to 50 ml / min. After about 2 hours, when the furnace temperature became 100 ° C. or lower, the Ar gas supply was stopped, and the sample boat was taken out to obtain carbon having substantially the same shape as the carbon of the composite material of this patent. This was repeated several times to obtain the required amount of carbon.

The prepared carbon / LiCoO ₂ composite material, carbon, and Teflon powder are weighed to a ratio of LiCoO ₂ 80 wt%, carbon 15 wt%, and Teflon powder 5 wt%, and the powder obtained by removing the Teflon powder in an agate mortar is used. After mixing for 6 minutes, Teflon powder was added thereto and mixed for 2 minutes to form a rough sheet. After forming into a sheet with a roll forming machine, a positive electrode was produced by punching with a punch.

  Using the positive electrode thus prepared, a 2032 type coin battery was manufactured using the same negative electrode and electrolyte material as in Example 1.

Each test battery is installed in a thermostat set at 21 ° C., and charged to 4.3 V at a constant current of 1 mA (0.75 mA / cm ² , per positive electrode area, the same applies hereinafter) by an automatic charging / discharging device. After 10 minutes of rest, the battery was discharged to 3.0 V at a constant current of 3.84 mA (2.89 mA / cm ² ), and rested for 10 minutes. This charge / discharge was repeated to measure the discharge capacity of the battery.

The results are shown in FIG. That is, FIG. 3 shows the weight ratio of formed carbon to LiCoO ₂ of the composite material on the horizontal axis, and the specific capacity (discharge capacity per weight of the positive electrode active material) of the test battery using the composite material corresponding to the vertical axis as the positive electrode. The curve 4 in FIG. 3 shows the change in specific capacity with respect to the amount of carbon formed.

  As is clear from FIG. 3, the carbon weight ratio directly formed on the surface of the positive electrode active material in the composite material of the present invention is 1.5 wt% or more and 15 wt% or less with respect to the weight of the positive electrode active material, and the specific capacity is 70 mAh / g or more. It was found to show excellent properties. On the other hand, it was found that when the amount of carbon formed was less than 1.5 wt% or more than 15 wt% with respect to the weight of the positive electrode active material, the specific capacity was as low as less than 70 mAh / g, which was not preferable.

[Example 4]
A ceramic boat containing 5 g of LiCoO ₂ powder is placed in a quartz tube, and another ceramic boat is filled with 5 ml of acetic acid, and the tip of the boat is placed at the end of the tube furnace in front of the sample boat in the quartz tube. did.

  Table 3 shows a tubular furnace in which argon (hereinafter referred to as Ar) gas as a carrier gas is supplied to a quartz tube at a rate of 50 ml / min for 5 minutes to purge oxygen in the quartz tube, and the quartz tube is installed. A predetermined temperature was set. When the predetermined temperature was reached, the Ar gas was increased to 100 ml / min. After maintaining the same conditions for 20 minutes, the supply of Ar gas was reduced to 50 ml / min. After 2 hours, the Ar gas supply was stopped, and the sample boat was taken out of the quartz tube to produce five types of composite materials 13 to 17 shown in Table 3.

The obtained samples 13 to 17, it obtains a weight ratio LiCoO ₂ generated carbon, to confirm the presence or absence of decomposition of LiCoO ₂ foundation to implement an X-ray diffraction measurement. Table 3 shows the proportion of carbon formed (%) relative to the weight of LiCoO ₂ and the presence or absence of a diffraction peak of Li ₂ CO ₃ as a decomposition product as an index indicating the decomposition of LiCoO ₂ .

As is clear from Table 3, in Samples 14 to 16, 4% or more of carbon was formed, and no significant decomposition of LiCoO ₂ was observed. It was confirmed that it was within a reasonable range. On the other hand, it was found that Sample 13 having a reaction temperature of 300 ° C. was not preferable because the decomposition of LiCoO ₂ was not observed but almost no carbon was formed. Further, in Sample 17 having a reaction temperature of 650 ° C., although a certain amount of carbon formation was obtained, decomposition of LiCoO ₂ was observed, and it was found that this was also not preferable.

[Example 5]
A ceramic boat containing 10 g of LiCoO ₂ powder was placed in the quartz tube, and another ceramic boat was filled with acetic acid in the amount shown in Table 4, and the tip of the boat was placed in the quartz tube at the end of the tubular furnace in front of the sample boat. Installed at a position where

The temperature of the tubular furnace was set to 350 ° C., carbon was formed on the surface of the LiCoO ₂ particles of the sample boat in the same procedure as in Example 4, and composite materials 18 to 20 were produced. With respect to the obtained samples 18 to 20, the weight ratio of generated carbon to LiCoO ₂ was determined and shown in Table 4.

  4.75 g of the sample was weighed, and the sample was mixed for 6 minutes with a coarse machine, and then 0.25 g of Teflon powder was added thereto, and further mixed for 2 minutes to prepare a coarse sheet. The rough sheet was formed into a sheet with a roll forming machine, and then punched with a punch to produce a positive electrode.

  Using the produced positive electrode, a 2032 type coin battery was produced using the same negative electrode and electrolyte material as in Example 1.

The coin cell is installed in a constant temperature bath at 21 ° C., charged to 4.3 V at a current value of 1 mA (0.75 mA / cm ² per positive electrode) by an automatic charge / discharge test apparatus, and after a pause of 10 minutes, a current value of 16 mA ( At 12 mA / cm ² ), the battery was discharged to 3.0 V and rested for 10 minutes. This charge / discharge operation was repeated, and the cycle characteristics of each battery were evaluated.

  The results are shown in FIG.

  That is, FIG. 4 shows the change in specific capacity of each test battery in accordance with the charge / discharge cycle, and the curves 5 to 7 show the ratio of the positive test batteries prepared using the samples 18 to 20 shown in Table 4. Indicates the change in capacity.

As is clear from FIG. 4, curves 6 and 7 of the sample prepared by installing 1 ml or more of the raw material (acetic acid) of the present invention with respect to 1 g of LiCoO ₂ showed excellent specific capacity. On the other hand, it was found that the curve 5 of the sample prepared with less than 1 ml of acetic acid per gram of LiCoO _{2 changed} with a small specific capacity, which was not preferable.

[Example 6]
100 ml of a NiCl ₂ aqueous solution having a concentration shown in Table 5 was prepared from nickel chloride hexahydrate NiCl ₂ .6H ₂ O and distilled water, and 5 g of LiCoO ₂ was mixed therewith and stirred for 10 minutes. The powder obtained by filtering this was dried to obtain LiCoO ₂ powder having NiCl ₂ fixed on the surface. The weight ratio of Ni fixed on the LiCoO ₂ particles was calculated from the difference between the weight of LiCoO ₂ immersed in the aqueous solution and the weight of the obtained powder.

  5 g of the obtained powder was weighed, transferred to a ceramic sample boat, the boat was installed in a quartz tube, and another ceramic boat was filled with 5 ml of methanol, and the quartz tube was placed in the tube furnace in front of the sample boat. The boat was installed at a position where the tip of the boat was at the end.

The temperature of the tubular furnace was set to 350 ° C., carbon was formed on the surface of the LiCoO ₂ particles of the sample boat in the same procedure as in Example 4, and composite materials 21 to 25 were produced. The obtained samples 21-25 showed weight ratio LiCoO ₂ product carbon determined Table 5.

  4.75 g of the sample was weighed, and the sample was mixed for 6 minutes with a coarse machine, and then 0.25 g of Teflon powder was added thereto, and further mixed for 2 minutes to prepare a coarse sheet. The rough sheet was formed into a sheet with a roll forming machine, and then punched with a punch to produce a positive electrode.

  Using the produced positive electrode, a 2032 type coin battery was produced using the same negative electrode and electrolyte material as in Example 1.

The coin cell is installed in a constant temperature bath at 21 ° C., charged to 4.3 V at a current value of 1 mA (0.75 mA / cm ² per positive electrode) by an automatic charge / discharge test apparatus, and after a pause of 10 minutes, a current value of 16 mA ( At 12 mA / cm ² ), the battery was discharged to 3.0 V and rested for 10 minutes. This charge / discharge operation was repeated twice, and the second discharge capacity was measured.

  The results are shown in FIG.

That is, the curve 8 in FIG. 5 shows the relationship between the Ni carrying amount (wt%) per LiCoO ₂ weight used in the positive electrode of each test battery and the specific capacity per LiCoO ₂ weight. As is apparent from FIG. 5, when the Ni loading proposed by the present invention is 0.01 wt% or more and 5 wt% or less, the specific capacity is 60 mAh / g or more, and good characteristics are exhibited. On the other hand, it was found that the specific capacity was less than 60 mAh / g when the Ni loading was less than 0.01 wt% or more than 5 wt%.

[Example 7]
As a positive electrode active material, 20 g of LiCoO ₂ and basic nickel carbonate NiCO ₃ · 2Ni (OH) ₂ · 4H ₂ O (molecular weight: 376.18) are mixed with the amounts shown in Table 6, and the mixed powder and 300 ml of distilled water are mixed. Were put in a 1 liter plastic bottle, filled with 100 g of zirconia balls having a diameter of 10 mm as a mixing medium, sealed, placed on a rotating pot mill base, and mixed by rotating for 5 hours. When the mill was completed, the material in the bottle was sieved to remove the zirconia balls, and then filtered and dried to obtain a mixed powder. The amount of Ni supported was calculated from the weight of basic nickel carbonate and shown in Table 6.

  5 g of the obtained powder was weighed, transferred to a ceramic sample boat, the boat was installed in a quartz tube, and another ceramic boat was filled with 5 ml of formic acid, and the quartz tube was placed in the tubular furnace in front of the sample boat. The boat was installed at a position where the tip of the boat was at the end.

The temperature of the tubular furnace was set to 450 ° C., carbon was formed on the surface of the LiCoO ₂ particles of the sample boat in the same procedure as in Example 4, and composite materials 26 to 30 were produced. For the obtained samples 26 to 30, the weight ratio of produced carbon to LiCoO ₂ was determined and shown in Table 6.

The sample, acetylene black (hereinafter referred to as AB), and Teflon powder are weighed to a total of 5 g in order to obtain a composition ratio of 90 wt% LiCoO _{2, 7} wt% carbon (conducting aid), and 3 wt% binder. A powder other than Teflon powder was mixed for 6 minutes with a machine, and then Teflon powder (3 wt%, 0.15 g) was added thereto and further mixed for 2 minutes to prepare a coarse sheet. The rough sheet was formed into a sheet with a roll forming machine, and then punched with a punch to produce a positive electrode.

  Using the produced positive electrode, a 2032 type coin battery was produced using the same negative electrode and electrolyte material as in Example 1.

The coin cell is placed in a constant temperature bath at 21 ° C., charged to 4.3 V at a current value of 1 mA (0.75 mA / cm ² per positive electrode) by an automatic charge / discharge test apparatus, and after a pause of 10 minutes, a current value of 5. The battery was discharged at 49 mA (4.12 mA / cm ² ) to 3.0 V and rested for 10 minutes. This charge / discharge operation was repeated, and the change in discharge capacity was measured.

  The results are shown in FIG.

  That is, FIG. 6 shows a change in specific capacity per positive electrode active material of each test battery with charge / discharge cycles, and curves 9 to 13 are positive electrodes prepared using samples 26 to 30 shown in Table 6. The change of the specific capacity of the test battery is shown.

As is clear from FIG. 6, the curves 10 to 12 of the test battery produced using the sample in which the Ni catalyst of the present invention is supported at 0.01 wt% or more and 5 wt% or less with respect to LiCoO ₂ have an excellent specific capacity. Indicated. On the other hand, the curve 9 of the sample supporting Ni catalyst with less than 0.01 wt% relative to LiCoO ₂ and the curve 13 of the sample supporting more than 0.5 wt% transitioned with a small specific capacity, It turned out to be undesirable.

[Example 8]
As a positive electrode active material for a lithium battery, 20 g of LiCoO ₂ powder was weighed in a ceramic boat, and the sample boat was placed so as to be located in the quartz tube and at the center of the tubular furnace. Furthermore, another ceramic boat was filled with 20 ml of ethanol and installed in a quartz tube at a position where the tip of the boat was placed at the end of the tubular furnace in front of the sample boat.

A composite material in which carbon was formed on LiCoO ₂ was produced in the same manner as in Example 1 except that argon (hereinafter referred to as Ar) gas was used as the carrier gas and the set temperature of the tubular furnace was maintained at 450 ° C. for 15 minutes. Carbon formed on LiCoO ₂ on powder was 7.01Wt% to LiCoO ₂ powder.

The measured X-ray diffraction of the composite powder, with the diffraction peak of LiCoO _2, a diffraction peak of Li 2 _CO 3, Co also exists, a part of LiCoO ₂ foundation was found to be reduced and decomposed .

The obtained composite material was divided into four parts, and each was put in an alumina crucible and heat-treated in the atmosphere at the temperature shown in Table 7 for 1 hour to obtain Samples 31 to 34. The formed carbon on LiCoO ₂ was determined as the value shown in Table 7 from the weight difference before and after the treatment of the sample. The X-ray diffraction measurement of the obtained powder was also performed, and the results of the Co peak are shown in Table 7 as indicating the state of LiCoO ₂ decomposition.

The obtained powder and the carbon produced in the Ni net of Example 3 were weighed to a total of 4.85 g, transferred to an agate mortar and mixed for 6 minutes with a milling machine, and 0.15 g of Teflon was added thereto. Powder was added and mixed for another 2 minutes to form a rough sheet, which was then formed into a sheet with a roll molding machine, and then punched with a punch to prepare LiCoO ₂ 90 wt%, carbon 7 wt%, and binder 3 wt%.

The coin cell is installed in a constant temperature bath of 21 ° C., charged to 4.3 V at a current value of 1 mA (0.75 mA / cm ² per positive electrode) by an automatic charge / discharge test apparatus, and after a pause of 10 minutes, a current value of 1. The battery was discharged at 33 mA (1.0 mA / cm ² ) to 3.0 V and rested for 10 minutes. This charge / discharge operation was repeated twice, and the second discharge capacity was measured.

  The results are shown in FIG.

  FIG. 7 is a graph showing the heat treatment temperature on the horizontal axis and the specific capacity per weight of the positive electrode active material of the battery on the vertical axis, and the curve 14 shows the relationship of the test battery of this example.

As is apparent from FIG. 7, when the heat treatment temperatures of the present invention were 300 ° C. and 500 ° C., both were 90 mAh / g or more, indicating an excellent specific capacity. In addition, almost no decomposition products of LiCoO ₂ existed at these heat treatment temperatures. On the other hand, when the heat treatment temperatures were 250 ° C. and 600 ° C., the specific capacity was less than 90 mAh / g, which was not preferable.

[Example 9]
A composite material in which carbon was formed on 20 g of LiCoO ₂ was produced in the same manner as in Example 8. Carbon formed on LiCoO ₂ on powder was 8.04Wt% to LiCoO ₂ powder.

The measured X-ray diffraction of the composite powder, with the diffraction peak of LiCoO _2, a diffraction peak of Li 2 _CO 3, Co also exists, a part of LiCoO ₂ foundation was found to be reduced and decomposed .

The obtained composite material was divided into four parts, and each was put in an alumina crucible and heat-treated in the atmosphere at 450 ° C. for the time shown in Table 8 to obtain Samples 35 to 38. The formed carbon on LiCoO ₂ was determined as the value shown in Table 7 from the weight difference before and after the treatment of the sample. The X-ray diffraction measurement of the obtained powder was also performed, and the results of the Co peak are shown in Table 8 as indicating the state of LiCoO ₂ decomposition.

The obtained powder and the carbon produced by the Ni net of Example 3 above are weighed to a total of 4.85 g (however, in the case of sample 35, only sample 35 is weighed) and transferred to an agate mortar for 6 minutes. Mix with a cracking machine, add 0.15 g of Teflon powder to this and mix for 2 minutes to make a rough sheet. After forming into a sheet with a roll molding machine, punch out with LiCoO ₂ 90 wt%, carbon 7 wt%, binder A positive electrode having a composition of 3 wt% was produced.

The coin cell is installed in a constant temperature bath of 21 ° C., charged to 4.3 V at a current value of 1 mA (0.75 mA / cm ² per positive electrode) by an automatic charge / discharge test apparatus, and after a pause of 10 minutes, a current value of 1. The battery was discharged at 88 mA (1.4 mA / cm ² ) to 3.0 V and rested for 10 minutes. This charge / discharge operation was repeated twice, and the second discharge capacity was measured.

  The results are shown in FIG.

  FIG. 8 is a graph showing the heat treatment time (minutes) on the horizontal axis and the specific capacity per weight of the positive electrode active material of the battery on the vertical axis, and the curve 15 shows the relationship of the test battery of this example.

As is apparent from FIG. 8, the heat treatment time of the present invention was 30 minutes or 120 minutes (2 hours), both of which were 80 mAh / g or more, indicating an excellent specific capacity. Moreover, the decomposition products of LiCoO ₂ disappeared during these heat treatment times. In contrast, when the heat treatment temperature was 20 minutes or 150 minutes (2.5 hours), the specific capacity was less than 80 mAh / g, which was not preferable.

  The present invention can take the following aspects. In one embodiment of the present invention, for a lithium battery including a nonaqueous organic solvent dissolved as a solute as a lithium salt as an electrolyte, a lithium metal oxide that is a positive electrode active material, a carbon material that is a conductive additive, and these particles The present invention proposes a positive electrode which is composed of a binder material for binding, and in which all of the conductive assistant is formed by directly forming carbon on the surface of the lithium metal oxide particles.

  In addition, a chemical vapor deposition method is proposed as a simple and effective method for directly forming and coating carbon as a conductive additive on lithium metal oxide particles. In this method, the present invention proposes a solution of an organic compound as a raw material for forming carbon. At the same time, an inert gas or a low-reactive gas is used as a carrier gas to supply the lithium metal oxide particles to form the carbon. In one embodiment of the present invention, it is proposed that the weight ratio of carbon formed as a conductive additive is 4 wt% or more and 20 wt% or less with respect to the weight of the positive electrode active material.

  Furthermore, in one embodiment of the present invention, the weight ratio of the lithium metal oxide, the conductive additive, and the binder material constituting the positive electrode is determined in advance, and the range of the weight ratio on the lithium metal oxide particles that are the positive electrode active material. A carbon material as a conductive auxiliary agent is directly fixed and coated on the surface so as to be inside, and the generation ratio is calculated, and if necessary, the same or different conductive auxiliary agent is satisfied so as to satisfy the mixing ratio. It is proposed that a positive electrode is produced by adding a necessary amount of and mixing. In this case, it is proposed to produce the material so that the carbon weight ratio directly formed on the surface of the positive electrode active material is 1.5 wt% or more and 15 wt% or less with respect to the weight of the positive electrode active material.

  In one embodiment of the present invention, in order to directly form carbon on the lithium metal oxide particles, the temperature at which the lithium metal oxide is installed is set to 350 ° C. or more and 600 ° C. or less, and the temperature is increased to such a temperature, or Before that, the carrier gas is supplied, the environment for forming carbon on the positive electrode active material particles is placed in a deoxygenated state, and the organic compound solution as a raw material is installed in the carrier gas supply direction with respect to the positive electrode active material particles. A method is proposed in which the installation amount is 1 ml or more per 1 g of the positive electrode active material.

  In one embodiment of the present invention, when carbon is directly formed on the lithium metal oxide particles, the carbon / lithium metal oxide composite material used for the positive electrode for a lithium battery is directly formed for the carbon formation. A method for supporting a metal catalyst on lithium metal oxide particles is proposed.

  Namely, Fe, Ni, Co, Cu, Sn, Zn, Cr, In, and Sb are used as catalysts for carbon formation, and one or more of chlorides, sulfides, carbonates or acetates of these metals are used. In addition, after the metal catalyst is fixed on the surface of the positive electrode active material particles, carbon growth is performed on the surface of the positive electrode active material particles. In one aspect of the present invention, the amount of the metal catalyst to be fixed on the surface of the positive electrode active material particles is proposed to be 0.01 wt% or more and 5 wt% or less per weight of the positive electrode active material.

  Several methods are conceivable as a method for realizing this proposal as one aspect of the present invention. As one specific example, metal chloride of Fe, Ni, Co, Cu, Sn, Zn, Cr, In, and Sb is used. The positive electrode active material particles are dipped in an aqueous solution in which one or a plurality of oxides, sulfides, carbonates or acetates are dissolved as solutes, and dried to give a catalyst for carbon growth on the surfaces of the positive electrode active material particles. The concentration of the aqueous solution and the amount of the positive electrode active material immersed in the aqueous solution are not particularly limited as long as the amount of the fixing metal described above is realized. As an example, the concentration of the aqueous solution is 0.05 wt% or more and 10 wt% or less. The immersion amount of the positive electrode active material can be 10 g / liter or more and 500 g / liter or less. Although the immersion time of the positive electrode active material particles in the aqueous solution is not particularly limited, as an example, it can be 1 minute or more and 1 hour or less.

  Another method is to mix one or more of metal chlorides or sulfides, carbonates or acetates of Fe, Ni, Co, Cu, Sn, Zn, Cr, In, and Sb into the positive electrode active material. These powders and zirconia balls are filled in an alumina pot and mixed in a pot mill. In this case, it is preferable that the solution in which the metal compound is insoluble is filled together because mixing becomes easy. The mixing ratio of the metal compound and the positive electrode active material is not particularly limited as long as the supported amount described above is realized, but as an example, the mixing ratio may be 0.06 wt% or more and 30 wt% or less with respect to the positive electrode active material. it can.

  An amount of the positive electrode active material and an organic compound solution as a raw material are set in a quartz tube, and a carrier gas such as dry Ar gas, dry nitrogen gas, or dry helium gas is supplied into the tube at a constant temperature for a predetermined time. Carbon, which is a conductive additive, is fixedly formed on the surface of the material particles.

In addition, regarding a composite material in which carbon is formed on the surface of a positive electrode active material using an organic compound solution as a raw material, the base positive electrode active material may be reduced and decomposed depending on the raw material. If the positive electrode active material is reduced and decomposed even with a small amount, intercalation of Li ⁺ ions to the particle surface is difficult to proceed, and there is a concern that the battery characteristics may be greatly deteriorated.

  One aspect of the present invention also proposes a post-treatment of the composite material made to alleviate this concern. That is, in the present invention, the composite material in which carbon is once formed on the surface of the lithium metal oxide, which is a positive electrode active material, is treated in the air at a temperature of 300 ° C. to 500 ° C. for 30 minutes to 2 hours. The composite material thus treated is utilized for a lithium battery as a positive electrode active material.

  As described above, by applying a positive electrode that directly forms and coats carbon as a conductive auxiliary agent on the positive electrode active material particles, the specific capacity is large, the discharge characteristics capable of acquiring a large current are excellent, and the deterioration is small. A lithium battery can be realized.

  As described above, according to the present invention, the battery has a large discharge capacity, and can realize lithium battery characteristics exhibiting excellent capacity maintenance even after the charge / discharge cycle has elapsed, thereby greatly contributing to environmental conservation and effective use of energy. It will be.

Claims (7)

Lithium metal oxide, which is a positive electrode active material capable of electrochemically inserting and desorbing lithium ions, in a lithium battery containing a non-aqueous organic solvent in which a lithium salt is dissolved as a solute as an electrolyte, A lithium battery positive electrode composed of a binder material for binding these particles,
The conductive auxiliary agent is formed by coating carbon on the surface of the lithium metal oxide particles, and chemical vapor deposition for forming and coating the carbon on the lithium metal oxide particles as the positive electrode active material. The method uses a raw material for forming carbon as a solution of an organic compound, together with an inert gas or a low-reactive gas as a carrier gas, and supplies the positive electrode active material particles to form the carbon.
The positive electrode for a lithium battery, wherein the organic compound solution contains carbon and oxygen in compound molecules. The positive electrode for a lithium battery according to claim 1, wherein the solution of the organic compound is any one of methanol, ethanol, ethylene glycol, acetone, formic acid, or acetic acid. The positive electrode for a lithium battery according to claim 1 or 2, wherein a weight ratio of carbon serving as the conductive auxiliary agent is 4 wt% or more and 20 wt% or less with respect to the weight of the positive electrode active material. Regarding the positive electrode for a lithium battery, the weight ratio of the lithium metal oxide, the conductive additive, and the binder material constituting the positive electrode is determined in advance, and the weight ratio of carbon on the positive electrode active material lithium metal oxide particles is positive electrode active material. A carbon material serving as a conductive auxiliary agent is coated and formed so as to be within a range of 1.5 wt% or more and 15 wt% or less with respect to the substance weight,
The positive electrode for a lithium battery is produced by mixing the positive electrode active material formed by coating the conductive auxiliary agent, a required amount of carbon, and the binder material. 2. The positive electrode for a lithium battery according to 2. In the method of forming carbon on the positive electrode active material particles, the temperature at which the positive electrode active material particles are allowed to stand to form carbon is 350 ° C. or higher and 600 ° C. or lower. Supply the carrier gas from before, place the environment for forming carbon in the positive electrode active material particles in a deoxygenated state, the organic compound solution as a raw material is installed in the carrier gas supply direction with respect to the positive electrode active material particles, The installation amount is 1 ml or more per 1 g of the positive electrode active material. The positive electrode for a lithium battery according to any one of claims 1 to 4. In the positive electrode active material, one or more of Fe, Ni, Co, Cu, Sn, Zn, Cr, In, and Sb chloride or sulfide, carbonate or acetate is used as the weight of the positive electrode active material. 6. The lithium according to claim 1, wherein carbon is formed and coated on the positive electrode active material particles after being added in advance so as to be 0.01 wt% or more and 5 wt% or less. Battery positive electrode. A material obtained by treating a composite material in which carbon is formed on the surface of the lithium metal oxide, which is the positive electrode active material, in the atmosphere at a temperature of 300 ° C. to 500 ° C. for 30 minutes to 2 hours is processed. It uses as a material. The positive electrode for lithium batteries of any one of the Claims 1 thru | or 6 characterized by the above-mentioned.

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