KR100404894B1 - Cathode materials of battery and method for preparing thereof - Google Patents

Abstract

The present invention relates to a positive electrode material of a battery and a method of manufacturing the same, and in particular, a surface treatment that can be used as a positive electrode material of a battery, including a lithium metal composite oxide core and a fluorine-based organometallic salt coating layer having a high capacity, long life characteristics, and safety. A lithium metal composite oxide and a method for producing the same. The lithium or lithium ion secondary battery including the surface-treated lithium metal composite oxide of the present invention as a positive electrode material has excellent life characteristics at room temperature as well as storage characteristics and life characteristics at high temperatures.

Description

Cathode material of battery and its manufacturing method {CATHODE MATERIALS OF BATTERY AND METHOD FOR PREPARING THEREOF}

The present invention relates to a positive electrode material of a battery and a method for manufacturing the same, and more particularly, to a battery material including a lithium metal composite oxide core and a fluorine-based organometallic salt coating layer having excellent storage characteristics and lifetime characteristics at a high temperature, and to a production thereof It is about a method.

In lithium or lithium ion secondary batteries, the life characteristics, safety and storage properties at high temperatures of batteries are essential elements for battery applications.

The most influential factor on the battery life characteristics is the electrochemical characteristics of the active material of the positive electrode and the negative electrode, and there have been many developments in the field of the negative electrode active material in recent years. However, there are still many areas to be improved in the positive electrode active material field. In particular, the safety and high temperature storage characteristics of the battery are mostly LiCoO ₂ , LiNiO ₂ and LiMn ₂ O ₄ as positive electrode active materials. ₂ has the highest capacity, but there are many difficulties in practical use due to thermal safety issues, LiMn ₂ O ₄ is not used alone due to its low cost, and LiCoO ₂ also needs to be improved due to poor high temperature storage characteristics.

Many studies have been conducted to solve these problems, US Patent No. 5,733, 685 discloses a method of improving the high temperature storage characteristics by coating a metal carbonate with LiMnO ₄ , Japanese Patent Application Laid-Open 11-317230 discloses a method of coating a metal oxide with LiCoO ₂ to improve the battery life characteristics and safety. In addition, a number of papers have been published on how to improve thermal safety by using various dopants in LiNiO ₂ series. In addition, methods for improving battery safety and lifespan by adding additives to electrolytes Are known. However, the above methods only affect the lifespan characteristics and safety of the battery, but do not affect the high temperature storage characteristics at all, and are not effective for the life characteristics at high temperatures.

Therefore, there is a need for further research on materials that can improve battery life characteristics and safety while at the same time improving storage characteristics and life characteristics at high temperatures.

In order to solve the above problems, it is an object of the present invention to provide a positive electrode material of a battery that can improve the life characteristics and safety of the battery and at the same time improve the storage characteristics and life characteristics at high temperatures.

Another object of the present invention is to provide a method for producing a positive electrode material of a battery capable of improving high temperature storage characteristics and high temperature life characteristics.

1 is a curve showing the results of DTA analysis of a powder coated with a fluorine-based organometallic salt on the surface of a core lithium metal composite oxide according to the present invention.

Figure 2 shows the life characteristics at room temperature (25 ℃) of a lithium metal composite oxide coated with a fluorine-based organometallic salt and an uncoated lithium metal composite oxide according to the present invention.

Figure 3 shows the life characteristics at high temperatures (55 ℃) of the lithium metal composite oxide coated with a fluorine-based organometallic salt and an uncoated lithium metal composite oxide according to the present invention.

Figure 4a shows the discharge curve according to the life at room temperature (25 ℃) of the surface of the lithium metal composite oxide not coated.

Figure 4b shows the discharge curve according to the life at room temperature (25 ℃) of the lithium metal composite oxide coated with a fluorine-based organometallic salt on the surface according to the present invention.

Figure 5 shows the DSC analysis showing the thermal properties of the lithium metal composite oxide coated with a fluorine-based organometallic salt on the surface according to the present invention.

In order to achieve the above object, the present invention

a) lithium metal composite oxide core; And

b) fluorine-based organometallic salt coating layer

It provides a surface-treated lithium metal composite oxide comprising a.

In addition, the present invention

a) providing a lithium metal composite oxide core;

b) providing a fluorine-based organometallic salt;

c) the lithium metal composite oxide core of step a) and the fluorine-based organic step of b)

Coating a metal salt; And

d) calcining the coated lithium metal composite oxide of step c)

It provides a method for producing a surface-treated lithium metal composite oxide comprising a.

The present invention also provides a lithium or lithium ion secondary battery comprising such a surface-treated lithium metal composite oxide as a positive electrode active material.

Hereinafter, the present invention will be described in detail.

The positive electrode material of the present invention includes a coating layer which serves to suppress the reactivity of cores and electrolytes capable of occluding and releasing lithium ions.

The lithium metal composite oxide core used in the present invention is a compound having a layered structure represented by Formula 1, a spinel compound represented by Formula 2, an olivine structure represented by Formula 3, and represented by Formula 4 It can be selected from the layered oxide.

[Formula 1]

In the formula of Formula 1,

L is Ni, or Co,

X is Al, B, Sn, Ti, Zr, Si, Co, or Ni,

x is 0 ≦ x ≦ 0.5.

[Formula 2]

[Formula 3]

In the formula (3),

Y is Co, Fe, or Mn.

[Formula 4]

In the formula (4),

Z is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Y, Sn, Al, Si, or In,

a is 0.2 ≦ a ≦ 0.8,

b is 0.2 ≦ b ≦ 0.8,

c is 0 ≦ c ≦ 0.3.

In addition, the fluorine-based organometallic salt used in the present invention is a compound in which a metal cation represented by the following formula (5) or (6) and a fluorine-based organic compound are present as anions and bound to each other:

[Formula 5]

[Formula 6]

In the formula 5 or 6,

F is a fluorine-based organic material containing carbon trifluoride (CF ₃ ),

A is N, or C,

M is a compound containing metal elements such as Li, Na, K, Mg, Ca, Sr, Ba, B, Al, Si, Y, Ti, Sn, or metal elements thereof,

x and y are each an integer of 1-5.

Further preferred fluorine-based organometallic salts are the compounds shown in Table 1 below.

compound (C ₂ F ₅ ) ₂ P (= O) OLi CF ₃ CO ₂ Li (CF ₃ CO) ₂ NLi CF ₃ SO ₃ Li CH ₃ SO ₃ Li C ₄ F ₉ SO ₃ Li C ₆ F ₅ SO ₃ Li C ₆ H ₅ SO ₃ Li C ₉ F ₁₇ SO ₃ Li (CF ₃ SO ₂ ) ₂ NLi (CF ₃ CH ₂ OSO ₂ ) ₂ NLi ((CF ₃ ) ₂ CHOSO ₂ ) ₂ NLi (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) NLi (CF ₃ SO ₂ ) ₃ CLi (CF ₃ CH ₂ OSO ₂ ) ₃ CLi

The positive electrode material of the battery of the present invention is a method of forming a thermally stable solid electrolyte film on the surface of a lithium metal composite oxide by coating the lithium metal composite oxide core with a fluorine-based organic metal salt and heat treatment. In the surface-treated lithium metal composite oxide particles, metal and fluorinated organic materials are decomposed and re-fused in the surface layer to coat the surface. That is, the fluorine-based organometallic salt covering the surface of the lithium metal composite oxide before heat treatment is decomposed during the heat treatment process so that the metal reacts with the surface of the oxide or the decomposition product of the fluorine organic material to form a physical solid electrolyte film on the surface of the oxide. do. When the lithium or lithium ion secondary battery is constructed using the oxide obtained by the above method, the surface coating layer formed by heat treatment is thermally stable compared to the electrochemically formed solid electrolyte membrane, so that not only the battery life characteristics but also high temperature Improve storage characteristics and thermal safety.

First, the fluorine-based organometallic salt to be coated is dissolved using an aqueous solution or an organic solution such as water or alcohol as a solvent, and then a uniform solution is formed. The solution formed is dissociated or dissolved in molecular units with lithium and anions, and the amount of the coating layer varies depending on the type, specific surface area, and surface properties of the core lithium metal composite oxide to be coated, but preferably 0.001 to 20 with respect to the core. Molar%.

After preparing a lithium metal composite oxide to be coated on a solution in which an organic metal salt is dissolved, a slurry is prepared. The slurry is stirred and heated to remove the solvent to coat the organic metal salt on the surface of the lithium metal composite oxide. In addition, a mixed solution is prepared by using a fluorine-based organometallic salt using an aqueous solution or an organic solution such as water or alcohol, and then sprayed onto a lithium metal composite oxide fluidized in hot air of 50 ° C. or higher to remove only the solution by evaporation. Thereafter, the coated lithium metal composite oxide is heat-treated for 10 minutes to 10 hours while flowing gas at a temperature of 200 to 900 ° C. to form a lithium metal fluoride composite oxide containing a new phase metal on the surface of the core. At this time, the atmosphere control gas which can be used is air or mixed gas of nitrogen and oxygen, and flow volume shall be 0.05-3.0 L / gh. Some elements of the coating layer during the heat treatment may vary depending on the temperature, but may be doped into the core particle.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

EXAMPLE

Example 1

Lithium trifluoroacetate (CF ₃ CO ₂ Li, lithium trifluoroacetate) was dissolved in ethanol as a coating material, and then stirred for 10 minutes or more to prepare a uniform mixed solution. Lithium cobalt oxide (C-10, Nippon Chemical Inc., Japan) was added to the obtained mixed solution to prepare a slurry while stirring. The salt was then coated by depositing the surface of the lithium cobalt oxide while blowing air to remove the solution ethanol. At this time, the content of the coating material was adjusted to 0.1 mol% based on the lithium cobalt oxide under the assumption that all of the coating material was coated on the surface of the lithium cobalt oxide.

The lithium cobalt oxide coated as described above was heat treated at 500 ° C. for 1 hour in an air atmosphere using an electric furnace to remove residual solvent and to heat the coating material. At this time, the heat treatment atmosphere was an air atmosphere, and the flow rate was 2 L / h.

An electrode was prepared using lithium cobalt oxide coated by heat treatment as a positive electrode active material. The obtained lithium cobalt composite oxide powder was mixed with 10% graphite and 5% polyvinylidine fluoride (PVdF) binder as a binder and n-methyl pyrrolidinone (NMP). Dispersion in solvent gave a slurry. The slurry was coated on aluminum foil and then heated to evaporate the n-methyl pyrrolidone solvent to dryness. The dried electrode was pressed by applying a pressure of about 500 kg / ㎠ and cut to prepare a cell. Lithium metal was used as a negative electrode, and electrolyte was used as a solution in which 1 mol of LiPF _{6 was} dissolved in a mixed solvent in which ethylene carbonate (EC) and ethylmethyl carbonate were mixed at a volume ratio of 1: 2.

Example 2

Except for using lithium trifluoromethanesulfonate (CF ₃ SO ₃ Li, lithium trifluoromethanesulfonate) as a coating material in Example 1 was carried out in the same manner as in Example 1.

Example 3

Except for using lithium benzoate (C ₆ H ₅ CO ₂ Li, lithium benzoate) as a coating material in Example 1 was carried out in the same manner as in Example 1.

Example 4

Except for using N-rithiotrifluoromethanesulfonimide ((CF ₃ SO ₂ ) ₂ NLi, N-lithiotrifluoromethanesulfonimide) as a coating material in Example 1 was carried out in the same manner as in Example 1.

Example 5

The same process as in Example 1 was carried out except that (CF ₃ SO ₂ ) ₃ CLi was used as a coating material in Example 1.

Example 6

Except that in Example 1 (CF ₃ CF ₂ CH ₂ OSO ₂ ) ₂ NLi as a coating material was carried out in the same manner as in Example 1.

Example 7

Except for using CF ₃ CO ₂ Li as a coating material in Example 1, and adjusting the molar ratio to lithium cobalt oxide to 0.03 mol% was carried out in the same manner as in Example 1.

Example 8

Example 1 and except that (CF ₂ SO ₂ ) ₃ CLi as a coating material in Example 1, the molar ratio to lithium cobalt oxide is adjusted to 1.0 mol%, and the heat treatment temperature is 500 ℃ It carried out in the same way.

Example 9

In order to produce a core of lithium-metal composite oxide using the Al (OH) ₃ to a raw material for Co (OH) _3, and Al in the lithium raw material Li ₂ CO ₃ with cobalt doping (doping) Li: Co: The molar equivalence ratio of Al was 1.02: 0.95: 0.05, and ethanol was used as a solvent. These were mixed and ground and mixed uniformly for 12 hours using a ball mill. The mixture was dried in a drier for 12 hours, calcined at 400 ° C. for 10 hours, then pulverized and mixed again, and heat-treated at 900 ° C. for 10 hours in air to obtain a core LiCo _0.95 Al _0.05 O ₂ .

This was carried out in the same manner as in Example 1 except that it was used as a core and (CF ₃ SO ₂ ) ₂ NLi as a coating material.

Example 10

LiCH ₃ COO and Mn (CH ₃ COO) ₂ were mixed to synthesize a lithium manganese composite oxide powder having a coreine spinel structure such that the molar ratio [Li] / [Mn] of lithium manganese was 0.538. After homogeneously mixing, the mixture was heat-treated in an air atmosphere at 480 ° C. for 10 hours, cooled to promote reaction, and sufficient to be remixed, and then reacted in an air atmosphere at 700 ° C. for 20 hours to synthesize spinel powder. In the heat treatment process, the flow rate of air was 0.1 L / gh, and the obtained lithium manganese spinel compound had a composition of Li _1.05 Mn _1.95 O ₄ .

This was carried out in the same manner as in Example 1, except that this was used as a core and CF ₃ SO ₃ Li as a coating material.

[Comparative Example]

Comparative Example 1

Except for using the core lithium cobalt oxide (C-10, Nippon Chemical, Inc., Japan) in Example 1 was carried out in the same manner as in Example 1.

Comparative Example 2

The same procedure as in Example 10 was carried out except that the core Li _1.05 Mn _1.95 O ₄ was used without coating.

In order to measure the high temperature storage characteristics of the cells prepared in Examples 1 to 10 and Comparative Examples 1 and 2, a half battery including an electrode as a positive electrode and a lithium metal as a negative electrode was constructed. The charging and discharging range was 3 to 4.2 V. After two cycles of charging and discharging, each cell was charged to 4.2 V again, held at 80 ° C. for 3 days, and then discharged to measure the battery capacity. In addition, the structural safety of the electrode active material was charged to 4.2 V, the cell was disassembled and the positive electrode was washed, and then observed by DSC. The measurement was performed in a glove box to avoid contact with air, and the measurement results are shown in Table 2 below and FIGS. 1 to 5.

division Discharge capacity after 1 cycle (mAh / g) Rear capacity aged at 80 ℃ for 3 days (mAh / g) Capacity reduction rate after aging at 80 ℃ for 3 days (%) Example 1 142.7 136.9 4.1 Example 2 142.3 136.9 3.8 Example 3 140.4 132.54 5.6 Example 4 141.6 135.6 4.2 Example 5 142.7 138.1 3.2 Example 6 141.5 135.1 4.5 Example 7 143 135.1 6.8 Example 8 137 133.3 3.2 Example 9 142.5 136.5 4.2 Example 10 120.2 111.4 7.3 Comparative Example 1 143.2 131.6 8.1 Comparative Example 2 121.5 102.7 15.5

Through Table 2, the self-discharge was much smaller when the coated Examples 1 to 10 were aged for 3 days at a high temperature of 80 ° C., compared to the uncoated Comparative Examples 1 to 2.

1 is a curve showing a DTA analysis result of the powder coated on the surface, it can be seen that decomposition by-products occur in the vicinity of about 300 ℃. In addition, since there was a slight weight loss in the vicinity of about 800 ℃, it can be seen that the newly produced material decomposed at around 300 ℃ is decomposed again at around 800 ℃.

Figure 2 shows the life characteristics at room temperature (25 ℃), it can be seen that Example 1, Example 2, and Example 7 coated with the core lithium metal composite oxide is superior to Comparative Example 1 without coating. .

Figure 3 shows the life characteristics at high temperature (55 ℃), it can be seen that Examples 1 to 3, and Example 5 coated as in the normal temperature (25 ℃) was excellent.

4A and 4B show discharge curves according to lifespan at room temperature (25 ° C.), and in the case of Comparative Example 1 (FIG. 4A) without coating, the discharge curves were lowered as the cycle progressed. , The width was very large. However, in the coated Example 1 (FIG. 4B), it was confirmed that there was almost no tendency for the discharge curve to lower.

Figure 5 shows the DSC analysis showing the thermal properties of the coated positive electrode material, as compared with Comparative Example 1 without coating Example 1 and Example 8 coated, not only increases the temperature at which the heat generation occurs but also reduces the amount of heat generated. Could confirm.

As described above, the lithium or lithium ion secondary battery including the lithium metal composite oxide core and the fluorine-based organic metal salt coating layer of the present invention as a positive electrode material has a large capacity, excellent life characteristics at room temperature, and excellent safety. It has excellent high temperature storage characteristics and high temperature life characteristics.

Claims (10)

a) lithium metal composite oxide core; And b) fluorine-based organometallic salt coating layer Surface-treated lithium metal composite oxide comprising a. The method of claim 1, The lithium metal composite oxide of a) is a compound having a layered structure represented by the following formula (1), a spinel compound represented by the formula (2), an olivine structure compound represented by the formula (3), and a layered structure represented by the formula (4) Surface-treated lithium metal composite oxides selected from oxides of the structure: [Formula 1] In the formula of Formula 1, L is Ni, or Co, X is Al, B, Sn, Ti, Zr, Si, Co, or Ni, x is 0 ≦ x ≦ 0.5. [Formula 2] [Formula 3] In the formula (3), Y is Co, Fe, or Mn. [Formula 4] In the formula (4), Z is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Y, Sn, Al, Si, or In, a is 0.2 ≦ a ≦ 0.8, b is 0.2 ≦ b ≦ 0.8, c is 0 ≦ c ≦ 0.3. The method of claim 1, The surface-treated lithium metal composite oxide of the b) is a compound represented by the following formula (5) or (6): [Formula 5] [Formula 6] In the formula 5 or 6, F is a fluorine-based organic material containing carbon trifluoride (CF ₃ ), A is N, or C, M is a metal element such as Li, Na, K, Mg, Ca, Sr, Ba, B, Al, Si, Y, Ti, Sn, or a compound containing these metal elements, x and y are each an integer of 1-5. The method of claim 1, A surface-treated lithium metal composite oxide having a coating amount of the fluorine-based organometallic salt of b) in an amount of 0.001 to 20 mol relative to 100 mol of the lithium metal composite oxide of a). a) providing a lithium metal composite oxide core; b) providing a fluorine-based organometallic salt; c) the lithium metal composite oxide core of step a) and the fluorine-based organic step of b) Coating a metal salt; And d) calcining the coated lithium metal composite oxide of step c) Method of producing a surface-treated lithium metal composite oxide comprising a. The method of claim 5, The coating of step c) dissolves the fluorine-based organometallic salt in an aqueous solution or an organic solution to prepare a mixed solution, and then sprays onto the lithium metal composite oxide fluidized in hot air of 50 ° C. or higher to evaporate and remove only the solution. Method for producing a surface-treated lithium metal composite oxide to be carried out. The method of claim 5, Method for producing a surface-treated lithium metal composite oxide of the step c) is 0.001 to 20 moles with respect to the lithium metal composite oxide 100 water. The method of claim 5, The method of manufacturing a surface-treated lithium metal composite oxide of the step d) is performed for 10 minutes to 10 hours at a temperature of 200 ~ 900 ℃. Surface-treated lithium metal composite oxide prepared by the method of claim 5. A lithium or lithium ion secondary battery comprising the surface-treated lithium metal composite oxide of claim 1 as a positive electrode active material.