JP2001167762A - Lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent decrease in capacitance in charging and discharging cycles of a lithium ion battery. SOLUTION: The lithium ion battery is disclosed, which comprises a positive electrode 1 made of a positive electrode material at least containing lithium- based composite metal oxides capable of occluding and discharging lithium ions; a negative electrode 2 made of a carbon-based conductive material capable of occluding and discharging lithium ions; and an organic non-aqueous electrolyte solution interposed between the positive electrode and the negative electrode. At least a portion of the lithium-based composite metal oxides has a single crystal structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lithium cobalt oxide (LiCoO) capable of occluding and releasing lithium ions.
O ₂ ), a positive electrode made of a positive electrode material containing at least a lithium-based composite metal oxide exemplified by lithium manganate (LiMn ₂ O ₄ ), and carbon such as graphite or carbon black capable of occluding and releasing lithium ions. The present invention relates to an improvement of a lithium ion battery including a negative electrode made of a system conductive material, and an organic non-aqueous electrolyte solution such as propylene carbonate provided between the positive electrode and the negative electrode.

[0002]

_2. Description of the Related Art In recent years, LiCoO ₂ , LiNi
A lithium ion battery using a lithium-based composite metal oxide such as O ₂ or LiMn ₂ O ₄ and using a carbon-based material such as graphite for the negative electrode has a large dischargeable power capacity per unit weight and a single cell. The other two
Its use is rapidly expanding as a battery with a high energy density because it can operate equipment without boosting the voltage because it is higher than secondary batteries such as NiCd secondary batteries and nickel-metal hydride secondary batteries. LiC as cathode material
Batteries using oO ₂ , LiMn ₂ O _{4, and the} like are widely used because cobalt and manganese to be used are relatively abundant in resources and are available at low cost.

[0003] As a method for producing the lithium-based composite metal oxide used for these positive electrodes, an Ander L.
unblad Bill Bergman, "So
ldState Ionics "96 (1997) 17
As shown in FIGS. 3-181 and 183-193, Li ₂ CoO _{3 is used} as a lithium raw material, and Co _{2 is used} as a cobalt raw material.
Using CO ₃ , these were adjusted so that Li / Co = 1.14, molded into a bellet, reacted at 700 ° C. for 5 hours, calcined at 800 ° C. for 3 hours, and then fired. A lithium-based composite metal oxide having an average particle size of 1 μm or more is produced by a solid phase method in which pellets are crushed and washed with water to collect particles.

As another method for producing a lithium-based composite metal oxide, T.I. Ogiwara, Y .; Sai
to, et. al, "Journal of the
Society of Japan "101 (199
8) As shown in 1159-1163, LiNO _{3 is used} as a lithium source, and Co (N
Using O ₃ ) ₂ , these are adjusted to Li / Co = 1 and dissolved in distilled water, and the raw material solution is adjusted to a concentration of 0.05 to 1.0 mol / liter. The raw material liquid thus adjusted is supplied to the ultrasonic spray pyrolysis apparatus at 25 ° C. by atomizing with air, and the dry pyrolysis is performed at a drying temperature of 400 ° C. and a pyrolysis temperature of 500 to 900 ° C. By that
There is a liquid phase method described as a spray pyrolysis method for obtaining LiCoO ₂ having an average particle size of 0.56 μm.

Further, as another liquid phase method, YK.su
n, "journal of Materials
As shown in Sciencen. (1996) 3617-3621, LiNO ₃ is used as a lithium raw material and Co (NO ₃ ) ₂ .6H ₂ O is used as a cobalt raw material.
These were adjusted so that Li / Co = 1, and the pH was 1
The mixture was stirred and mixed with polyacrylic acid (PAA) while adjusting with nitric acid so that
In the evening, after the sol is dried until a sol is obtained, the resulting sol is dried at 70 to 80 ° C. while stirring to remove water to obtain a gel, and at 300 ° C. for the purpose of removing organic components in the gel. For 1 hour, then 400-65
There is a sol-gel method in which heat treatment is performed at 0 ° C. to obtain LiCoO ₂ .

[0006]

However, the crystal structure of the conventional lithium-based composite metal oxide obtained by each of the above-mentioned methods is a particle having a polycrystalline structure or a polycrystalline structure having a partially amorphous phase. Since the strain at the crystal grain boundaries increases with the discharge cycle and the crystal structure is destroyed, the amount of lithium ions that can be stored or released decreases, and for example, in the LiMn ₂ O ₄ , the elution of Mn occurs. There is a problem that the electric capacity is gradually decreased because the organic non-aqueous electrolyte solution such as ethylene carbonate is oxidized and deteriorated due to oxidation.

[0007] Further, the lithium-based composite metal oxide used for these positive electrodes is subjected to lithium ion storage and release on its surface as described above. Although the discharge rate can be obtained, the conventional lithium-based composite metal oxide particles obtained by each of the above-described methods have a polycrystalline structure or an amorphous structure as described above, and are not subjected to pulverization or the like. Has a particle diameter of about 1 μm or more, and a lithium-based composite metal oxide having a particle diameter of 1 μm or less and having a single crystal structure could not be produced.

Accordingly, the present invention has been made in view of the above-mentioned problems. First, the present invention prevents a decrease in electric capacity in a charge / discharge cycle of a lithium ion battery, and secondly, the present invention relates to It is an object of the present invention to provide a lithium ion battery having a higher charge / discharge rate.

[0009]

In order to solve the above-mentioned problems, a lithium ion battery according to the present invention comprises a positive electrode made of a positive electrode material containing at least a lithium-based composite metal oxide capable of inserting and extracting lithium ions. A negative electrode made of a carbon-based conductive material capable of inserting and extracting lithium ions,
An organic nonaqueous electrolyte solution provided so as to be interposed between the positive electrode and the negative electrode, wherein at least a part of the lithium composite metal oxide has a single crystal structure. According to this feature, since at least a part of the lithium-based composite metal oxide has a single crystal structure, crystal defects on the surface of the lithium-based composite metal oxide are suppressed, and the lithium-based composite metal oxide is not organically-organized. It is possible to suppress catalytic effects such as oxidation during charging on the aqueous electrolyte solution, and it is possible to prevent a decrease in electric capacity in a charge / discharge cycle due to oxidative deterioration of these organic non-aqueous electrolyte solutions. Further, by making at least a part of the single crystal structure, the surface energy of the particles can be reduced, and even if the particle size is reduced, the metal in the lithium-based composite metal oxide, particularly, LiMn ₂ O
₄ can suppress the dissolution of Mn.

[0010] In the lithium ion battery of the present invention, the metal component in the lithium-based composite metal oxide is preferably at least one of nickel, cobalt, manganese, and iron. In this way, by setting the metal component to at least one of nickel, cobalt, manganese, and iron, each of these metals is relatively abundant in resources and can be obtained at low cost. A lithium ion battery can be manufactured.

In the lithium ion battery of the present invention, it is preferable that the lithium-based composite metal oxide is a fine powder having a particle size of about 0.1 to 1 μm. By doing so, the surface area of the lithium-based composite metal oxide can be increased by reducing the particle diameter as compared with the conventional art, and a lithium ion battery having a high charge / discharge rate can be provided.

In the lithium ion battery of the present invention, the lithium-based composite metal oxide having at least a portion having a single crystal structure is generated by a hydrothermal reaction using water in a supercritical or subcritical state as a solvent. Is preferred. In this way, by appropriately controlling the production conditions, the lithium-based composite metal oxide having the single crystal can be efficiently produced, and the lithium-based composite metal oxide having a smaller particle size than the conventional one can be produced. It can also be obtained continuously and at low cost.

[0013]

Embodiments of the present invention will be described below with reference to FIG. FIG. 1 is an exploded perspective view of the lithium ion battery according to the present invention. As shown in FIG. 1, the structure of the lithium ion battery of the present invention has a bottomed cylindrical outer case 7 made of aluminum.
A sheet-shaped positive electrode material composed of O ₂ and Ketjen Black (trade name, manufactured by Lion Akzo) as a conductive material, and Teflon (polytetrafluoroethylene; PTFE, product surface manufactured by DuPont-Mitsui Fluorochemicals) as a binder was formed. A power generation cell 9 including a positive electrode 1, a negative electrode 2 in which an active material layer mainly composed of natural graphite is formed on a core made of copper, and a separator 3 separating the positive electrode 1 and the negative electrode 2 are housed. In the outer case 7, propylene carbonate (PC) which is an organic non-aqueous electrolyte solution is provided.
An electrolyte in which LiPF ₆ as an electrolyte is dissolved at a rate of 1 M (mol / liter) is injected into the solvent, and a sealing lid 8 made of aluminum is fixed to an opening of the outer case 7. The battery is sealed and sealed.

Further, the positive electrode 1 is connected to a positive electrode terminal 6 via a positive electrode current collecting tab 4, and the negative electrode 6 is connected to an outer case 7 via a negative electrode current collecting tab 5, respectively. Can be extracted to the outside as electric energy.

Here, the lithium ion battery having the above structure was manufactured as follows. First, the positive electrode material is
90% by weight of LiCoO ₂ as a positive electrode active material, 5% by weight of Ketjen black as a conductive agent, and 5% by weight of Teflon as a binder, and N-methyl-2-pyrrolidone as a predetermined amount of a solvent. (NMP),
After melting to prepare a slurry for the positive electrode, this slurry for the positive electrode was used as an aluminum foil (thickness: 20) as a positive electrode current collector.
μm). Then, the solvent N-
Methyl-2-pyrrolidone (NMP) was dried, compressed to a predetermined thickness by a roller, cut to a predetermined width and length, and the positive electrode current collector tab 4 was welded to the positive electrode current collector. .

At the same time, 95% by weight of natural graphite powder as the negative electrode active material, 5% by weight of polyvinylidene fluoride (PVDF) as the binder, and an NMP solution as a solvent were mixed to form a negative electrode. After preparing the slurry,
This negative electrode slurry is coated with copper foil (thickness:
16 μm). After that, the solvent is dried,
After being compressed to a predetermined thickness by a roller, it was cut into a predetermined width and length, and the negative electrode current collector tab 5 was welded to the negative electrode current collector.

Next, the positive electrode 1 and the negative electrode 2 are combined with a separator 3 (thickness: 25 μm) made of a microporous polyethylene film.
Then, the power generation cell 9 was prepared by inserting the power generation cell 9 into the outer case 7, and the negative electrode current collecting tab 5 was welded to the bottom of the outer case 7. Thereafter, the positive electrode current collecting tab 4 was welded to the sealing lid 8.

Thereafter, an electrolyte solution in which LiClO ₄ as an electrolyte is dissolved in the propylene carbonate (PC) at a ratio of 1 M (mol / liter) is injected into the outer case 7, and then sealed with the sealing lid 8. Thus, a cylindrical lithium ion battery was manufactured. As the negative electrode material, natural graphite, artificial graphite, or the like is preferably used. As the electrolyte of the electrolytic solution, in addition to the above-mentioned LiClO ₄ , LiP
F ₆ , LiBF ₄ , LiCF ₃ SO _{3 and the} like can also be used.

LiC, which is a lithium-based composite metal oxide used for the positive electrode material of the lithium ion battery of the present invention,
A method using super (sub) critical water as a method for producing oO ₂ will be described below.

FIG. 2 shows the configuration of the apparatus used in this embodiment. In the metal salt melting bath 10, a metal salt solution that is stable even at high temperatures (for example, KNO ₃ —NaN manufactured by Shin-Nichika Chemical Co., Ltd.)
O ₃ 50 wt% nitrates Metal heat treatment agent Tempering agent T
-3) is accommodated. Then, the electric heater 12 is immersed therein for heating, and the thermoelectric element 1 for temperature measurement is immersed therein.
4 are arranged. By controlling the heating by the electric heater 12 while measuring the temperature with the thermoelectric body 14, the metal salt solution in the metal salt molten bath 10 is controlled to a predetermined temperature.

Then, the reaction tube 16 is immersed in the metal salt melting bath 10, and LiCo
To generate O _2. The stop valve 18 connected to the reaction tube 16 is provided for collecting the generated gas generated in the reaction tube 16 after the reaction.

When LiCoO ₂ is produced by such an apparatus, first, a raw material aqueous solution is charged into the reaction tube 16. The raw material aqueous solution is, for example, LiOH and Co (NO ₃ ).
₂ dissolved in distilled water is used. Where LiC
The ratio Li / Co for producing oO ₂ is not a theoretical ratio of 1, but LiCoO is set in a state where Li ions are present in excess in the raw material aqueous solution in excess of Co ions.
₂ is preferable because the yield can be increased. In the present embodiment, Li / Co is set to about 15.

Also, by using Co (NO ₃ ) ₂ ,
NO ₃ ions can be added to the raw material aqueous solution. This NO ₃
Functions as an oxidizing agent. Therefore, Co ₂ ⁺ supplied as Co (NO ₃ ) ₂ due to the presence of this NO ₃ ion →
The oxidation reaction to Co ₃ ⁺ can be promoted. Further, the reaction tube 1
Since air exists in 6, oxygen in the air also functions as an oxidizing agent. As described above, it is preferable that oxygen is present in the gas phase in the reaction tube 16.

By adding LiOH, the alkali molar ratio [OH ⁻ ] / [NO ₃ ⁻ ] can be increased. By increasing the alkali molar ratio, the production of LiCoO ₂ can be promoted. Furthermore, the alkali molar ratio can be further increased by adding ammonia.
That is, it is considered that one molecule of ammonia [NH ₃ ] generates one OH ^- 1 molecule. The addition of ammonia can raise the pH of the raw material aqueous solution, thereby suppressing the production of Co ₃ O _{4 and the} like in the temperature raising process and improving the yield of LiCoO ₂ .

The aqueous solution of the raw material is adjusted to a target pressure at the temperature in the metal salt melting bath 10. Here, as for this pressure, assuming that the raw material aqueous solution is pure water, a steam table (Steam Tabl) is used.
e) is calculated. For example, reaction temperature 400 ° C., the density of water in the reaction pressure 30MPa, since it is 0.35 g / cm ^3, the volume of the reaction tube 16 is as long as 10 cm ^3,
The raw material aqueous solution is charged so that the total amount of the raw material aqueous solution in the reaction tube 16 becomes 3.5 cm ³ .

The supercritical point of water is 374 ° C., 22M
Pa, and the reaction conditions are set to be in a subcritical or supercritical state. Although it depends on other conditions such as the concentration of the raw material solution, it is preferable that the temperature is at least 250 ° C. or more, and the pressure is 20 MPa or more so that the water is in a subcritical state. It is particularly preferable to set the conditions.

After charging the raw material aqueous solution into the reaction tube 16,
The reaction tube 16 is immersed in the metal salt melting bath 10 and kept in that state for a predetermined reaction time (for example, about 5 to 20 minutes). Next, the reaction tube 16 is taken out of the metal salt melting bath 10 and put in a cold water bath to immediately stop the reaction.

Then, the contents of the reaction tube 16 are taken out,
By washing with water after filtration, the reaction product LiC
Fine particles of oO ₂ are obtained.

The LiCoO ₂ thus obtained is:
As shown in the transmission electron micrograph of FIG. 7 (a), it has a small amount of impurities, a small particle diameter, and is a single crystal or a material close to a single crystal, and thus is very suitable as a battery material. Therefore, it can be suitably used as a positive electrode material of a lithium ion battery.

These lithium-based composite metal oxides, L
Regarding the formation temperature of iCoO ₂ , Li ⁺ , Co ²⁺ ,
Ions having a charge such as NO ₃ ^— tend to be more stably present in the liquid. On the other hand, a nonpolar substance such as LiCoO ₂ , which is a metal oxide after the reaction, originally tends to exist more stably in a gas. Furthermore, the solubility of the metal oxide drops sharply as the temperature of the supercritical water increases under a constant pressure. Therefore, as the temperature of water in the supercritical state, which is the generation temperature of the lithium-based composite metal oxide, is increased, the solvent changes from a liquid state to a gaseous state, and the solute reacts from a polar ionic state to a nonpolar oxide. Is faster. Further, since the solubility of the oxide is reduced, the precipitation of the oxide (in this case, LiCoO ₂ ) as a reaction product is promoted. At this time, the nucleus generation rate of oxide generation is increased, and the particle diameter of the generated oxide is reduced.

When the solvent is liquid, the precipitated oxide is
It takes in water of crystallization and hydroxyl groups, but not when the solvent is gaseous. Therefore, it is considered that generation of an oxide having a high degree of crystallinity is promoted and single-crystal oxide fine particles are easily obtained. Further, the conditions such that the water becomes supercritical state, the CO ²⁺ due to the presence of nitrate Co ^{3 +}
Oxidation can be suitably performed.

Further, when producing these lithium-based composite metal oxides, it is better to increase the Li / Co ratio in the aqueous solution of the raw material and to make the condition of excess Li ion, so that LiCoO ₂
Has a good yield. That is, when the Li / Co ratio is reduced, the amount of Co ₃ O ₄ that is not the target substance in the reaction product increases. This is probably because the presence of a large amount of Li during the deposition of the oxide facilitates the production of LiCoO ₂ more equilibrium than Co ₃ O ₄ . Raw material aqueous solution concentration,
Depending on other conditions such as temperature and pressure, Li / Co is 1
-20, especially 15-20. Further, the overall concentration of the raw material aqueous solution, that is, the concentration of lithium ions and cobalt ions is reduced to increase the concentration range of lithium ions from 0.05 mol / liter to 2 m.
ol / liter, the yield of LiCoO ₂ increases.

Further, the production of the lithium-based composite metal oxide
At the time of formation, ammonia is added and an alkali molar ratio ([N
H₃] 10 [OH⁻]) / [NO₃ ⁻]
LiCoO₂Yield is high. This is the
By increasing the pH, CO ₃O₄Precipitates, especially overheating
It is considered that precipitation during the process became difficult to occur. Manufacturing method
In the method, the raw material aqueous solution is charged into the reaction tube 16 at normal temperature,
Immersed in a metal melting bath 10. Therefore, the supercritical
Before the state is created, Co₃O₄Generates
It remains as it is even in the supercritical state. That is,
After warming, LiCoO₂Condition that generates
Even before that, Co₃O₄Is generated
This remains in the reaction product as it is.

By increasing the alkali molar ratio and the pH in the raw material aqueous solution, Co ₃ O ₄ in the solution is increased.
, The precipitation is suppressed, the generation of Co ₃ O ₄ in the temperature raising process is suppressed, and the C in the reaction product is reduced.
It is considered that generation of o ₃ O ₄ is suppressed.

By increasing the amount of LiOH added, it is possible to increase the amount of Li and increase the concentration of OH ⁻ .
Thus, it can be seen that adding a large amount of LiOH is also preferable from this point.

It is preferable that the alkali molar ratio be 1 to 20, especially about 5 or more. Thereby, the yield of LiCoO ₂ in the reaction product can be made sufficient.

It is to be noted that the deposition of Co ₃ O ₄ can be similarly suppressed by using an acid instead of an alkali. this is,
This is because the solubility of Co ₃ O ₄ is reduced even in the acidic condition. Then, by lowering the pH of the raw material aqueous solution, the Co ₃ O ₄ generated in the temperature raising stage is dissolved in water to efficiently generate LiCoO ₂ during the reaction after the temperature raising. Can be.

In addition, when producing the lithium-based composite metal oxide, by adding NO ₃ , an oxidizing agent is added to the raw material aqueous solution. That is, NO ₃ functions as an oxidizing agent for oxidizing CO ²⁺ to Co ³⁺ by being reduced to NO ²⁻ . Therefore, cobalt is changed to Co (NO
₃ ) It is understood that the addition in the form of ₂ is preferable. Therefore, it is also preferable to further add nitric acid or aqueous hydrogen peroxide to increase the amount of the oxidizing agent. For example, by adding nitric acid in the form of ammonium nitrate (NH ₄ NO ₃ )
The nitric acid can be increased while maintaining the alkali molar ratio at a predetermined value.

Further, for oxidation of Co ²⁺ , a reaction tube 16 was used.
The oxygen gas in the gas phase also contributes. Therefore, it is also preferable to increase the amount of oxygen in the gas phase or to add ozone gas.

In the above description of the embodiment,
Although the description has been made on the assumption that LiCoO ₂ is produced, the present invention is not limited to this. Instead of cobalt, a simple substance or a mixture of manganese, nickel and iron can be used. As shown in b), manganese can be used to obtain single-crystal or nearly single-crystal LiMn ₂ O ₄ fine particles.

Example 1 Using the apparatus shown in FIG. 2, LiCoO ₂ was produced. The experiment was performed using a reaction tube 16 made of SUS316 having a volume of 10 cm ³ . The raw material aqueous solution contains 3.34 mol / liter of LiOH
And 1.56 mol / liter of Co (NO ₃ ) ₂ . The concentration of Co (NO ₃ ) ₂ is kept constant (0.097 mo)
1 / liter), and by changing the amount of LiOH,
The Co ratio was adjusted to (1, 5, 10, 15). Further, in order to investigate the influence of oxygen gas in the reaction tube 16, an experiment was conducted in which a part of the gas in the reaction tube 16 was replaced with argon (0.5 MPa).

3.5 cm ³ of the raw material aqueous solution was charged into the reaction tube 16 and reacted in the metal salt melting bath 10 adjusted to 400 ° C. for a certain period of time (7 minutes or 10 minutes). After the reaction, the reaction tube 16 was put into a water bath to stop the reaction. The reaction solution was subjected to suction filtration to collect generated particles. The crystal structure of the resulting particles is
It was measured by powder XRD (X-ray analysis). The shape and size of the formed particles were observed by TEM and SEM.
Further, the resulting particles were dissolved in hydrochloric acid (6M) and quantified by ICP to determine the stoichiometric ratio Li / Co of the product. The filtrate of the reaction solution was diluted, and the concentrations of nitrate ion and nitrite ion were determined by ion chromatography, and the concentrations of residual Li and Co were determined by flame atomic absorption spectrophotometry.

Table 1 shows the experimental conditions and results. In addition,
In Table 1, the Li / Co molar ratio is a rough value, and the exact value is twice the alkali molar ratio. Also,
The alkali molar ratio is the [OH ⁻ ] / [NO ₃ ⁻ ] ratio, and the relative intensity is the intensity ratio between the maximum peak of Co ₃ O _{2 and} the maximum peak of LiCoO _{2 in} the XRD chart. In addition, the reaction time includes a temperature raising time.

[Table 1]

When the Li / Co ratio was 5 or more and the alkali molar ratio was 2.36 or more, LiCoO ₂ was obtained. A peak derived from Co ₃ O ₄ was confirmed from the XRD chart, and the reactive product was a mixture of LiCoO ₂ (Co is trivalent) and Co ₃ O ₄ (Co is divalent and trivalent). The relative intensity of the maximum peak derived from Co ₃ O _{4 with} respect to the maximum LiCoO ₂ peak decreases as the raw material Li / Co ratio increases, as viewed from XRD. Therefore, in the range of the Li / Co ratio of 1 to 15, the larger the ratio, the more easily LiCoO ₂ is generated. Particles with a small relative intensity (reaction time 7 minutes, Li / Co = 15, air), (reaction time 10
The Li / Co ratio in Li / Co = 15 (air) was measured to be 0.853 and 0.795, respectively. Assuming that the produced particles are only LiCoO ₂ and Co ₃ O ₄ , the yield of LiCoO _{2 in} the particles is 95 mol, respectively.
% And 93 mol%.

Here, the production of LiCoO ₂ is based on the divalent C
O is oxidized to trivalent Co. The nitrite ion concentration in the recovered liquid increases with the phenomenon of relative intensity. This suggests that divalent Co in the raw material aqueous solution is oxidized to nitrate ions. Furthermore, the result of replacing the gas in the reaction tube 16 with argon (48 Pa = 5 ber) shows that the presence of air increases the yield of LiCoO ₂ . This indicates that oxygen in the air also contributes to the oxidation of Co. In addition, SEM and TE
According to the observation result of M, the diameter of the produced particles was 400 nm to 1 nm.
It was about μm, and it was a very fine particle. The synthesis conditions were as follows: reaction temperature 400 ° C., pressure 30 MPa, cobalt nitrate 0.
Li at a concentration of 0.5 M and a LiOH concentration of 0.5 M
Electron micrographs of the CoO ₂ fine particles are shown in FIGS. FIG. 3 is a photograph at a magnification of 30,000 and FIG. 4 is a photograph at a magnification of 40,000.

Accordingly, CoO ₃ O _{4 is obtained} by a method such as (i) further increasing the Li / Co ratio, (ii) increasing the alkali molar ratio, (iii) increasing the nitric acid concentration, or adding other oxidizing agents. And a single-phase LiCoO
₂ was obtained.

Example 2 In the same apparatus as in Example 1, ammonia was added to the raw material aqueous solution, and the effect was examined. Table 2 shows the conditions and results. Reaction time 10 minutes,
The reaction temperature is 400 ° C.

[Table 2]

From this, by adding ammonia, LiCoO ₂ is produced even when the Li / CO ratio = 1. In addition, even when ammonia is added, L / Co ratio in the raw material aqueous solution is increased to increase L / Co ratio.
The yield of iCoO ₂ is increasing. Therefore, it was confirmed that the yield of LiCoO ₂ can be increased by adding ammonia.

Example 3 Further, the reaction temperature was set to 200,
The temperature was changed to 300 and 400 ° C., and an experiment was performed. Table 3 shows the experimental conditions and results.

[Table 3]

From this, when the reaction temperature is lowered, LiC
It was confirmed that oO ₂ was hardly generated.

(Comparative test) In Example 1, Li / Co
An alkaline ion battery A of the present invention using LiCoO ₂ obtained at a ratio of 15 as the cathode material, and LiCoO ₂ produced by the conventional solid phase method shown in the photograph of FIG. 5 as the cathode material The used alkaline ion battery B is charged at each predetermined voltage, and the electrolytic solution L after the charging is charged.
FIG. 6 shows the result of taking out propylene carbonate (PC) in which iClO ₄ was dissolved at a rate of 1 M (mol / liter) and examined by infrared absorption spectroscopy.

From the results, in the case of the conventional polycrystalline structure, as shown in FIG. 6 (b), absorption of each functional group generated by oxidative decomposition of propylene carbonate (PC) is observed at 4.2V. On the other hand, in the case of using LiCoO ₂ having a single crystal structure according to the present invention, as shown in FIG. 6A, it was found that the oxidative decomposition of the electrolytic solution was suppressed up to approximately 4.8 V. At a practical voltage such as 3.3 V, a decrease in battery capacity due to the deterioration of the electrolytic solution can be suppressed to a low level.

[0053]

The present invention has the following effects.

(A) According to the first aspect of the present invention, since at least a part of the lithium-based composite metal oxide has a single crystal structure, crystal defects on the surface of the lithium-based composite metal oxide are suppressed. It is possible to suppress catalytic effects such as oxidation during charging of the lithium-based composite metal oxide on the organic non-aqueous electrolyte solution, and the electric capacity of the organic non-aqueous electrolyte solution during charge-discharge cycles due to oxidative deterioration of the solution is increased. Drop can be prevented. Further, by making at least a part of the single crystal structure, the surface energy of the particles can be reduced, and even if the particle size is reduced, the metal in the lithium-based composite metal oxide, in particular, Mn in LiMn ₂ O ₄
Can be kept low.

(B) According to the second aspect of the invention, since the metal component is at least one of nickel, cobalt, manganese, and iron, these metals are relatively abundant in resources and inexpensive. Because it is available, a lithium-ion battery can be manufactured at low cost.

(C) According to the third aspect of the present invention, the surface area of the lithium-based composite metal oxide can be increased by reducing the particle diameter as compared with the prior art, and therefore, a high charge / discharge rate can be obtained. A lithium ion battery can be provided.

(D) According to the invention of claim 4, the lithium-based composite metal oxide having the single crystal can be efficiently produced by appropriately controlling the production conditions.
It is also possible to obtain a lithium-based composite metal oxide having a smaller particle diameter continuously and inexpensively than in the conventional case.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing a structure of a lithium ion battery of the present invention.

FIG. 2 is a diagram showing a configuration of a manufacturing apparatus for a lithium-based composite metal oxide used as a positive electrode material of a lithium ion battery of the present invention.

FIG. 3 is an electron micrograph of LiCoO ₂ used for a positive electrode material of a lithium ion battery of the present invention.

FIG. 4 is an electron micrograph of LiCoO ₂ used as a positive electrode material of the lithium ion battery of the present invention.

FIG. 5 is an electron micrograph of LiCoO ₂ produced by a conventional solid-phase method.

FIG. 6 (a) is a diagram showing a result of infrared absorption spectroscopy measurement of an electrolytic solution in a lithium ion battery of the present invention.
(B) is a diagram showing a result of infrared absorption spectroscopy measurement of an electrolytic solution in a conventional lithium ion battery.

FIG. 7 (a) shows Li obtained by the production method of the present invention.
Shows a transmission electron micrograph of CoO _2.
(B) is the LiMn ₂ O obtained by the production method of the present invention.
FIG. ₄ is a diagram showing a transmission electron micrograph of FIG.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode 3 Separator 4 Positive current collecting tab 5 Negative current collecting tab 6 Positive terminal 7 Outer case 8 Sealing lid 9 Power generation cell 10 Metal salt melting bath 12 Heater 14 Thermocouple 16 Reaction tube

Continued on the front page F-term (reference) 4G048 AA04 AB02 AC06 AD04 AD07 AE05 AE07 5H003 AA01 AA04 AA08 BA00 BA05 BB05 BC06 BD02 5H014 AA02 BB00 BB05 EE10 HH06 5H029 AJ02 AJ05 AJ14 AK03 AL07 AM03 AM07 BJBJJB03

Claims (4)

[Claims] 1. A positive electrode comprising a positive electrode material containing at least a lithium-based composite metal oxide capable of storing and releasing lithium ions, a negative electrode comprising a carbon-based conductive material capable of storing and releasing lithium ions, and the positive electrode An organic non-aqueous electrolyte solution provided so as to be interposed between the negative electrodes, wherein at least a part of the lithium-based composite metal oxide has a single crystal structure. . 2. The lithium ion battery according to claim 1, wherein the metal component in the lithium-based composite metal oxide is at least one of nickel, cobalt, manganese, and iron. 3. The lithium ion battery according to claim 1, wherein the lithium-based composite metal oxide is a fine powder having a particle size of about 0.1 to 1 μm. 4. The method according to claim 1, wherein the lithium-based composite metal oxide at least partially having a single crystal structure is produced by a hydrothermal reaction using water in a supercritical or subcritical state as a solvent. The lithium ion battery according to any one of the above.