KR101449807B1 - Cathode active material, method for preparing the same, and lithium secondary batteries comprising the same - Google Patents

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same.
Formula _{Li [Li xz (Ni a Co} b Mn c) 1-x] O 2? ( Here, a + b + c = 1 , 0.05 ≤ x ≤ 0.33, 0 <z ≤ 0.05) or the formula Li [Li _xz ( Ni _a Co _b Mn _c ) _1-x ] O _{2 -y} F _y where a + b + c = 1, 0.05 ≦ x ≦ 0.33, 0 ≦ y ≦ 0.08, 0 <z ≦ 0.05 A production step of producing a manganese excess amount of a layered composite oxide; A mixing step of adding a metal salt, ammonium fluoride and the above-mentioned complex oxide to an organic solvent having a moisture content of 10% or less to form a mixture; And a heat treatment step of heat-treating the mixture under an inert atmosphere to coat the surface of the composite oxide with metal fluoride fluoride; And a method for producing the positive electrode active material.

Description

[0001] The present invention relates to a cathode active material, a method for producing the same, and a lithium secondary battery comprising the cathode active material, a method for preparing the same,

The present invention relates to a cathode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same. More particularly, the present invention relates to a method for producing a lithium manganese oxide superlattice composite oxide by using an organic solvent having a moisture content of 10% The present invention relates to a technique for improving initial efficiency, rate characteristics, and life characteristics by coating a metalloid fluoride and preventing capacity reduction due to the dissolution of Li ions generated during coating in an aqueous solution.

Lithium secondary batteries have been increasingly used in small electronic devices, electric vehicles, electric power storage devices, and the like, and there is a growing demand for cathode materials for secondary batteries having high safety, long life, high energy density and high output characteristics.

In this connection, the lithium over-layered lithium metal composite oxide is a cathode active material having a high capacity of 240 mAh / g or more per unit weight and is attracting attention as a next-generation electric vehicle and a cathode material for electric power storage which require high capacity characteristics.

However, it is difficult to realize a high capacity discharge capacity due to the large irreversible capacity due to the phase change in the first charge / discharge cycle of the lithium overburdened lithium metal complex oxide, and the lifetime due to elution of manganese ions and adverse reaction with electrolyte at high temperature And has a drawback that it is rapidly deteriorated. In addition, the lithium overburdened layered lithium metal composite oxide has a risk of causing a fire or an explosion by reacting with an electrolyte at a high temperature when used in a lithium secondary battery due to a structural instability occurring in a high charged state.

Accordingly, various materials are coated on the surface of the positive electrode active material in order to reduce the initial irreversible capacity of the lithium overpotable layered composite oxide and to realize a positive electrode material composed of a lithium oversubstituted layered composite oxide having excellent high rate characteristics and being usable for a long time, Attempts have been made to suppress the adverse reaction with and to improve the structural stability.

Among them, coatings of metal / metal oxide / metal fluoride and the like have been known to improve the electrochemical properties of the cathode active material. In particular, the coating of metal fluorides such as AlF ₃ greatly improves the electrochemical properties of layered compounds (See Non-Patent Document 1, etc.).

In particular, Patent Document 1 discloses a technique of wet coating a fine powder of a fluorine compound on the surface of a cathode active material for a lithium secondary battery to prevent the phenomenon that the performance of the battery deteriorates at life characteristics, particularly at high pressure and high rate.

As generally described in Patent Document 1, a general wet coating method of forming a metal fluoride on the surface of a cathode active material includes a fluorine (F) compound and an element precursor which reacts with the fluorine compound to form a fluorine compound coated on the cathode active material The cathode active material is added to the dissolved aqueous solution, reacted at a high temperature, and then heat-treated in an inert atmosphere or the like.

When AlF ₃ was coated on the lithium oversubstituted lithium metal composite oxide capable of achieving a high capacity, the electrochemical characteristics such as improvement in the rate characteristics and lifetime characteristics were improved. However, when the complex oxide It was difficult to expect an improvement in the long-term lifetime characteristics as expected due to the decrease in the capacity and the increase in the moisture content of the Li ion as a solvent.

Also, Patent Document 2 cites the above Patent Document 1, and it can be said that metal fluoride or metalloid fluoride can be used for coating by using a solution-based precipitation approach using an aqueous solvent Lt; / RTI &gt;

On the other hand, in the case of Patent Document 3, the inventor of Patent Document 1 has found that when the coating is performed by the wet coating method as in Patent Document 1, "the powder of the coated cathode active material forms a lump to change the particle size distribution, The coating effect is not exhibited at 100% because of the composition and structure of the cathode active material surface due to excessive contact with lithium ions. &Quot; or &quot; excessive lithium is easily dissolved in water or an organic solvent, The present inventors have pointed out the problem of the wet coating method of the metal fluoride disclosed in Patent Document 1 and the like as disclosed in Patent Document 1, The structural transition occurring on the surface of the active material is prevented.

In addition, the inventors of Patent Document 1 disclose that when metal fluoride and metal oxyfluoride are coated on the surface of a cathode active material, they protect the cathode active material from hydrofluoric acid present in the electrolyte solution and maintain the crystal structure of the cathode active material well But also increases the migration speed of lithium ions from the electrolyte to the cathode active material, thereby reducing the increase in internal resistance.

KR 10-0822013 B KR 10-2012-68826 A KR 10-2010-60363 A

"AlF3-coating to improve High Voltage Cycling Performance of Li [Ni1 / 3Co1 / 3Mn1 / 3] O2 cathode materials for Lithium Secondary Batteries," J. of Electrochem. Soc., 154 (3), A168-A172 (2007)

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems in the technical field as described above, and it is an object of the present invention to provide a method of coating a surface of a lithium manganese excess layered composite oxide with a metalloid fluoride-based material using an organic solvent having a moisture content of 10% , Rate characteristics, and life characteristics, and to prevent a decrease in capacity due to the dissolution of Li ions generated during coating in an aqueous solution.

Further, Li of the Li ₂ MnO ₃ region in the surface coating layer and the complex oxide reacts to form a lithium-metal-fluoride (Li-MF) complex having high ion conductivity, and thereby, a part of Li ₂ MnO ₃ is LiMn ₂ O ₄ cubic spinel phase, the mobility of Li is increased, and the oxidation and reduction reaction of Mn, which is kinematically slow during charging and discharging, is activated to reduce the irreversible capacity at the first charge / discharge curve, To maintain the characteristics, improve the high rate characteristics, the life characteristics, and improve the thermal stability.

The present invention also provides a method of manufacturing such a cathode active material and a secondary battery including the same.

In order to solve the above problems, the present invention provides the following embodiments.

In one embodiment, the present invention provides a lithium _{secondary battery comprising} : Li _x Li (Ni _a Co _b Mn _c ) _1-x ] O ₂ wherein a + b + c = 1, 0.05 x x 0.33, ) or formula _{Li [Li xz (Ni a Co} b Mn c) 1-x] O 2-y F y ( here, a + b + c = 1 , 0.05 ≤ x ≤ 0.33, 0 ≤ y ≤ 0.08, 0 < z < / = 0.05); A mixing step of adding a metal salt, ammonium fluoride and the above-mentioned complex oxide to an organic solvent having a moisture content of 10% or less to form a mixture; And a heat treatment step of heat-treating the mixture under an inert atmosphere to coat the surface of the composite oxide with metal fluoride fluoride; And a method for producing the positive electrode active material.

In the above formula, since the sum of Li and other metals becomes 1 + xz + 1-x = 2-z, the composition becomes smaller by z value than Li _{2 of the} layered structure LiMO ₂ (M = metal) And has a composition in which the cubic spinel structure is easily formed in the cathode active material.

In the above embodiment, lithium in the monoclinic Li ₂ MnO ₃ region in the composite oxide reacts with the metaloid fluoride forming a coating layer to form a lithium-metal-fluoride (Li-MF) complex ; And a step wherein the monoclinic Li ₂ MnO ₃ for a part of Li ₂ MnO ₃ area is to be changed to LiMn ₂ O ₄ of the cubic spinel structure; . &Lt; / RTI &gt;

Further, in the above embodiment, the lithium manganese oxide having the cubic spinel structure can undergo a reduction reaction at 2.8 to 3.0 V. In other words, the cathode active material coated with the metal halide fluoride forms a LiMn ₂ O ₄ cubic spinel phase on its surface, and a reduction peak is expressed on dQ / dV at 2.8 to 3.0 V during discharging (the capacity of the discharge curve is differentiated by voltage In the case of H-OLO, the reduction peak at 3.7V and 3.0 ~ 3.2V at the discharging time is shown as Ni (dQ / dV) and Ni (dQ / dV) , Indicating that Li enters the vicinity of Mn and a reduction reaction of the corresponding metal ions occurs).

Further, in the above embodiment, the complex oxide may include rhombohedral LiMO ₂ (where M is Ni, Co and Mn) and monoclinic Li ₂ MnO ₃ .

In this case, the structure of the composite oxide is determined by the surface coating of the metaloid fluoride with a surface-active LiMO ₂ (R ₃ m) + mono-phase Li ₂ MnO ₃ (L 2 / m) + cubic spinel LiMn ₂ O ₄ (Fd ₃ m) Can be like.

Further, in the above embodiment, the metaloid fluoride as the surface coating material may be one selected from the group consisting of AlF ₃ , MgF ₂ , CoF ₃ , NaF, and mixtures thereof, preferably AlF ₃ .

The surface of the cathode active material having the composition as shown in the above formula, in which the cubic spinel structure is easily formed, is coated with metal fluoride fluoride, and Li is eluted between the cathode active material and the coating layer to form a cubic spinel structure.

In addition, due to the formation of Li-MF complexes with high ionic conductivity, the diffusion and mobility of Li are increased, so that the reduction reaction of Mn, which is kinematically slow, is activated, The rate characteristic is increased and the capacity retention rate after 41 cycles is largely maintained in the course of repeating charge and discharge at 1C.

In addition, a large amount of heat is generated at a low temperature due to the structural deformation accompanied by the oxygen generated in the charging and discharging process of the lithium manganese excess layered composite oxide. On the other hand, when metalyl fluoride is coated, To maintain the high oxygen pressure and to prevent the generation of additional oxygen, thereby lowering the heat generation amount and increasing the heat generation temperature.

Further, in the above embodiment, the thickness of the coated metalloid fluoride may be 3 to 20 nm. When the thickness of the coating is less than 3 nm, the coating does not act as a protective layer of the cathode active material. If the thickness of the coating is thicker than 20 nm, the migration of Li ions may be disturbed and the capacity may decrease.

Also, in the above embodiment, the amount of the coated metalloid fluoride may be 0.3 to 2.0 wt%, and preferably 1.0 wt% with respect to the cathode active material.

Here, as the coating amount of the metal fluoride fluoride increases, the amount of the cathode active material capable of releasing Li ions decreases, thereby reducing the charging capacity. However, when the metal fluoride fluoride is surface-coated in an appropriate amount relative to the cathode active material, The cubic spinel structure is formed on the surface of the active material, and the discharge capacity is increased according to the improvement of the efficiency due to the reduction of the irreversible capacity. When the content of the coating layer is 2.0 wt% or more, the capacity decreases as the content of the cathode active material decreases, which is not preferable. When the content of the coating layer is 0.3 wt% or less, the coating effect is insignificant.

In the above embodiment, the organic solvent may be an alcohol organic solvent having a water content of 10% or less, and preferably an alcohol organic solvent having a water content of 5% or less. When only an organic solvent not containing water is used, the electrochemical characteristics can be expected to be improved without deteriorating the capacity characteristics, but a large amount of organic solvent is required due to low solubility of the fluorine raw material, , The yield is inferior. When the water content increases, the capacity decrease due to the elution of Li ions occurs. Therefore, an alcohol organic solvent having a water content of 10% or less is preferable, and an alcohol organic solvent having a water content of 5% More preferable.

Also, in the above embodiment, the heat treatment step may be performed at a temperature of 300 to 600 ° C for 3 to 10 hours, and may be performed under an inert atmosphere. The Li-M-F layer is not formed when heat treatment is performed at 300 ° C or less, and when the heat treatment is performed at a temperature of 600 ° C or more, the particle size and shape of the cathode active material may be changed to cause a change in characteristics.

In the above embodiment, the metal salt may be one selected from the group consisting of a metal alkoxide, a metal nitrate, a metal sulfate, and a mixture thereof.

In another embodiment, the present invention provides a cathode active material produced in the above embodiment.

In the above embodiment, a lithium manganese oxide having a cubic spinel structure formed by changing a part of the lithium manganese oxide in the layered structure in the complex oxide may be formed between the complex oxide and the metaloid fluoride coating layer.

In the above embodiment, the specific surface area of the cathode active material may be 2 to 6 m ² / g. If the specific surface area is less than 2 m ² / g, the reaction area of the cathode active material and the electrolyte may be decreased to cause a decrease in capacity. If the specific surface area is more than 6 m ² / g, the reaction area of the cathode active material and the electrolyte increases, .

In the above embodiment, the average particle diameter of the composite oxide may be 3 to 5 占 퐉. In the case of a lithium-excess metal oxide composite having a large amount of Mn composition, the conductivity is low and the rate characteristic is deteriorated when the average particle diameter is large. When the particle diameter is less than 3 占 퐉, the amount of the cathode active material which can be filled in the same volume due to lowering of the compound density is reduced, and the energy density per volume is lowered.

In another embodiment, the present invention provides a positive electrode comprising the positive electrode active material; A negative electrode comprising a negative electrode active material; And an electrolyte existing between the positive electrode and the negative electrode.

According to the present invention, the lithium secondary battery using the lithium oversized layered composite oxide electrode and the lithium secondary battery using the electrode can reduce the irreversible capacity to 15% or less during the first charge / discharge and realize a high capacity at discharge, And the thermal stability of the secondary battery can be increased.

In addition, the lithium overcharge layered composite oxide electrode and the lithium secondary battery manufactured according to the present invention can be charged and discharged at a high voltage of 4.5 V or more, and the capacity of the battery due to continuous charge and discharge, Can be significantly lowered.

1 is a schematic view schematically showing a structural change of a cathode active material before and after coating.
2 is a cross-sectional TEM image of the cathode active material after coating.
3 is a graph showing the lifetime characteristics of the cathode active material before coating and after coating.
4 is a graph showing changes in discharge capacity according to a coating solvent.

&Lt; Method for producing positive electrode active material &

The positive electrode active material according to the invention, the formula _{Li [Li xz (Ni a Co} b Mn c) 1-x] O 2 ( where, a + b + c = 1 , 0.05 ≤ x ≤ 0.33, 0 <z ≤ 0.05) Or Li _x (Ni _a Co _b Mn _c ) _1-x ] O _{2 -y} F _y where a + b + c = 1, 0.05? X? 0.33, 0? Y? 0.08, 0 <z &Lt; / = 0.05); &lt; / RTI &gt; A mixing step of adding a metal salt, ammonium fluoride and the above-mentioned complex oxide to an organic solvent having a moisture content of 10% or less to form a mixture; And a heat treatment step of heat-treating the mixture under an inert atmosphere to coat the surface of the composite oxide with metal fluoride fluoride; And a cathode active material.

The preparation step can be produced through various preparation methods such as a known coprecipitation method, a sol-gel process, and the like, and is not limited to any particular method.

FIG. 1 is a schematic view schematically showing the structure of a positive electrode active material composed of a composite oxide before and after coating. As shown in the left side of FIG. 1, the composite oxide before coating is rhombohedral LiMO ₂ where M is Ni, Co, Mn), and monoclinic Li ₂ MnO ₃ .

In the above formulas, since the sum of Li and other metals becomes 1 + xz + 1-x = 2-z, the composition becomes smaller by z value than Li _{2 of the} layered structure LiMO ₂ (M = metal) , And a composition in which a cubic spinel structure is likely to be formed in the positive electrode active material.

Accordingly, the metalloid fluoride reacts with the lithium to form the lithium coating layer of the monoclinic Li ₂ MnO ₃ region in the composite oxide-metal-, forming a fluoride (Li-MF) complex, wherein the monoclinic Li ₂ A portion of Li ₂ MnO ₃ in the MnO ₃ region may be changed to LiMn ₂ O ₄ in the cubic spinel structure to form a cubic spinel LiMn ₂ O ₄ layer at the interface between the complex oxide and the coating layer, As can be seen from the image of FIG. 2 as well, the structure of the composite oxide is determined by the surface coating of the metal fluoride (AlF ₃ ), LiMo ₂ (R ₃ m) + mono-Li ₂ may be such as MnO ₃ (L2 / m) + the cubic spinel LiMn ₂ O ₄ (Fd3m).

The mixing step may be performed by adding a metal alkoxide, a metal nitrate, a metal sulfate, a metal sulfate, or a mixture thereof to an alcoholic organic solvent (a mixed solvent obtained by mixing an organic solvent and distilled water (DI) at a predetermined ratio) having a water content of 10% And a mixture thereof, ammonium fluoride as a fluorine source, and the composite oxide prepared above are added and reacted at 60 ° C for at least 5 hours. Thereafter, the substrate is washed and dried in an oven at 120 DEG C for at least 12 hours to form a mixture.

The amount of the coated metalloid fluoride may be 0.3 to 2.0 wt%, preferably 1.0 wt%, based on the positive electrode active material.

The heat treatment step may be performed under an inert atmosphere such as nitrogen or argon at a temperature range of 300 to 600 DEG C for 3 to 10 hours.

The average particle diameter of the composite oxide may be 3 to 5 占 퐉.

<Cathode Active Material>

The cathode active material of the present invention is produced by the above-described production method.

As described above, a lithium manganese oxide having a cubic spinel structure formed by changing a part of the lithium manganese oxide in the layered structure in the complex oxide can be formed between the complex oxide and the metaloid fluoride coating layer, (See Figs. 1 and 2).

The specific surface area of the positive electrode active material ranges from 2 to 6 m²/ g, and the thickness of the coated metalloid fluoride may be from 3 to 20 nm.

&Lt; Lithium Secondary Battery Containing Cathode Active Material >

The positive electrode active material according to the present invention can be utilized as a positive electrode material of a lithium secondary battery and has the same structure as a known secondary battery except for the cathode active material composition and crystal structure and is manufactured by the same known manufacturing method The detailed description thereof will be omitted.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, with reference to the accompanying drawings, a lithium secondary battery including a method for producing a cathode active material according to the present invention and a cathode active material manufactured thereby will be described in detail with reference to preferred embodiments and comparative examples. However, these embodiments are only a preferred embodiment of the present invention, and the present invention should not be interpreted as being limited by these embodiments.

(Example 1)

① precursor synthesis

Sulfuric nickel (NiSO ₄ ), cobalt sulfate (CoSO ₄ ) and manganese sulfate (MnSO ₄ ) are dissolved in water at a ratio of 2: 2: 6 and then added to a 1 M sodium chloride solution. Slowly add ammonia water (NH ₄ OH) to the above solution at the same ratio as the metal concentration ratio. After reacting for 12 hours or more using a continuous type reactor, the formed precipitate was filtered, washed several times with an aqueous solution, and dried in a drying oven at 120 ° C to synthesize a Ni0.2Co0.2Mn0.6 (OH) ₂ precursor.

② Synthesis of complex oxide of lithium manganese excess

① The one precursor, the nickel cobalt manganese hydroxide (Ni0.2Co0.2Mn0.6 (OH) ₂₎ and, first the lithium carbonate (Li ₂ CO ₃₎ with a chemical equivalent ratio in the synthesis: After mixing ratio of 1.4, 700 to 900 ℃ in a 24-hour formula _{Li [Li xz (Ni a Co} b Mn c) 1-x] by firing O ₂ (here, a + b + c = 1 , 0.05 ≤ x ≤ 0.33, 0 <z ≤ 0.05) in the Lithium manganese excess complex oxide powder was synthesized.

In the above formula, the sum of Li and metal Ni, Co, and Mn is 1 + xz + 1-x = 2-z, which is smaller than the sum of Li and metal of layered structure LiMO ₂ (M = metal) A composite oxide of lithium manganese with a high composition in which cubic spinel structure is easily formed in the cathode active material is synthesized by the coating of the metal halide fluoride.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 1 in accordance with the content to be coated (0.3 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 0.3 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

Denka Black, a conductive material, and polyvinylidene fluoride (PVDF), a binder, were mixed in a ratio of 92: 4: 4 to prepare a slurry. The slurry was uniformly coated on an aluminum (Al) foil to prepare a positive electrode electrode plate.

A 2032 coin cell was fabricated using lithium metal as the cathode and 1.3M LiPF6 EC / DMC / EC = 3: 4: 3 solution as the electrolyte.

Charging and discharging of one cycle proceeded to 0.1 C from 3.0 to 4.7 V. After that, the discharge characteristics were measured at 0.2 C, 0.33 C discharge capacity and 3 C discharge capacity ratio, and after charging and discharging 41 times at 1 C The lifetime characteristics were evaluated by the capacity retention rate, and the results are shown in the following Tables 1 and 2.

(Example 2)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 1.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 1 in accordance with the content to be coated (1.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 1.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2 below.

(Example 3)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 1.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 1 in accordance with the content to be coated (2.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 2.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2 below.

(Example 4)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

① The one precursor, the nickel cobalt manganese hydroxide (Ni0.2Co0.2Mn0.6 (OH) ₂₎ and lithium carbonate (Li ₂ CO ₃₎ with a chemical equivalent ratio of the one prepared in: 1.4, and mixed in a ratio, LiF (or NH4F ) were mixed with 0.05 mol more than oxygen, 700 ~ 900 ℃ 24 sigan firing formula _{Li [Li xz (Ni a Co} b Mn c) 1-x] O 2-y and F _y in (here, a + b + c = 1, 0.05? x? 0.33, 0? y? 0.08, 0 <z? 0.05) were synthesized.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 2 in accordance with the content to be coated (1.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 1.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2 below.

(Example 5)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 4.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 1 in accordance with the content to be coated (1.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 1.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

(Comparative Example 1)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 4.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in water in accordance with the content to be coated (1.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 1.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2 below.

(Comparative Example 2)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 4.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 5 in accordance with the content to be coated (1.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 1.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2 below.

(Comparative Example 3)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 1.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 1 in accordance with the content to be coated (0.1 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and well dispersed. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Thereafter, a heat treatment for 5 hours or more under 400 ℃, a nitrogen atmosphere, 0.1 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2 below.

(Comparative Example 4)

① precursor synthesis

Was synthesized in the same manner as in Example 1.

② Synthesis of complex oxide of lithium manganese excess

Was synthesized in the same manner as in Example 1.

③ Metaloid Fluoride Coating Cathode Active Material Powder Synthesis

Aluminum nitride (Al (NO ₃ )) was dissolved in a solvent of ethanol: DI = 20: 1 in accordance with the content to be coated (3.0 wt% AlF ₃ coating), and the composite oxide powder synthesized in ② was added and dispersed well. The NH ₄ F solution dissolved in the same solution was slowly added to the well-dispersed Al (NO ₃ ) solution at 60 ° C. for 5 hours. Thereafter, the substrate was washed and dried in an oven at 120 캜 for 12 hours or more. Then, 400 ℃, to a heat treatment in a nitrogen atmosphere for 5 hours or more 3.0 wt% metalloid fluoride (AlF ₃₎ is to obtain a coated positive electrode active material.

④ Evaluation of battery characteristics

A battery was prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

division AlF3
Coating content (wt%) DI
Content (%) 1st
Charging capacity
(mAh / g) 1st
Discharge capacity
(mAh / g) Initial efficiency
(%,
Discharge / charge
Volume) Rate characteristic
(%,
3C / 0.3C capacity) After 41 cycles
Capacity retention rate (%) Li _{1 + x} M _1-x O ₂ 0 - 303 269 89 79 52 Example 1 0.3 5 298 275 92 80 95 Example 2 1.0 5 294 275 94 83 94 Example 3 2.0 5 288 270 94 83 93 Example 4 1.0 10 289 272 94 82 94 Comparative Example 1 1.0 100 285 263 92 82 92 Comparative Example 2 1.0 25 286 263 92 82 94 Comparative Example 3 0.1 5 296 269 91 80 90 Comparative Example 4 3.0 5 273 253 93 83 94 Li _{1 + x} M _1-x O _{2 -y} F _y 0 - 300 267 89 80 90 Example 5 1.0 5 289 272 94 83 94

division AlF3
Coating content (wt%) DI
Content (%) △ 1st
Charging capacity
(mAh / g) △ 1st
Discharge capacity
(mAh / g) △ Initial efficiency
(%,
Discharge / charge
Volume) △ rate characteristic
(%,
3C / 0.3C capacity) After 41 cycles
Capacity retention rate (%) Example 1 0.3 5 -5 6 3 One 43 Example 2 1.0 5 -9 6 5 4 42 Example 3 2.0 5 -15 One 5 4 41 Example 4 1.0 10 -14 3 5 3 42 Comparative Example 1 1.0 100 -18 -6 3 3 40 Comparative Example 2 1.0 25 -17 -6 3 3 42 Comparative Example 3 0.1 5 -7 0 2 One 38 Comparative Example 4 3.0 5 -30 -16 4 4 42 Example 5 1.0 5 -11 5 5 3 4

In Examples 1 to 5 in which AlF ₃ was coated with an organic solvent having a water content (DI content) of 10% or less, the initial efficiency (discharge capacity ratio versus charge capacity ratio), rate characteristics, life characteristics (post- ) And the discharge capacity increase effect.

As can be seen in Comparative Examples 1 and 2, when AlF ₃ was synthetically coated in a solvent having a water content of 10% or more, the initial efficiency, rate characteristics and lifetime characteristics were improved, The capacity decrease due to the elution of Li ions occurred.

On the other hand, as the content of the AlF ₃ coating increases, the coating effect increases. However, as in Comparative Example 4, when the content of the cathode active material is more than 2.0 wt% of AlF ₃ ,

Also, as in Comparative Example 3, when the content of AlF ₃ coating was 0.3 wt% or less, the coating effect was insignificant.

Claims (15)

Formula _{Li [Li xz (Ni a Co} b Mn c) 1-x] O 2 ( where, a + b + c = 1 , 0.05 ≤ x ≤ 0.33, 0 <z ≤ 0.05) or the formula Li [Li _xz (Ni _a Co _b Mn _c ) _1-x ] O _2-y F _y where a + b + c = 1, 0.05 ≦ x ≦ 0.33, 0 <y ≦ 0.08, 0 <z ≦ 0.05) A production step of producing an excess amount of the layered composite oxide;
A mixing step of adding a metal salt, ammonium fluoride and the above-mentioned complex oxide to an organic solvent having a moisture content of 10% or less to form a mixture; And
A heat treatment step of heat-treating the mixture under an inert atmosphere to coat a surface of the composite oxide with a metalloid fluoride;
And the cathode active material. The method according to claim 1,
Reacting the monoclinic Li ₂ MnO ₃ region lithium in the complex oxide with the metaloid fluoride forming a coating layer to form a lithium-metal-fluoride (Li-MF) complex; And
Changing a part of the Li ₂ MnO ₃ of the monoclinic Li ₂ MnO ₃ region to LiMn ₂ O ₄ having a cubic spinel structure;
Wherein the positive electrode active material further comprises a negative electrode active material. The method according to claim 1,
Wherein the composite oxide contains rhombohedral LiMO ₂ (where M is Ni, Co and Mn) and mono-crystalline Li ₂ MnO ₃ . The method according to claim 1,
Wherein the metal fluoride fluoride is one selected from the group consisting of AlF ₃ , MgF ₂ , CoF ₃ , NaF, and mixtures thereof. The method according to claim 1,
Wherein the composite oxide has an average particle size of 3 to 5 占 퐉. The method according to claim 1,
Wherein the amount of the metalloid fluoride coated is 0.3 to 2.0 wt% with respect to the cathode active material. The method according to claim 1,
Wherein the organic solvent is an alcohol-based organic solvent. The method according to claim 1,
Wherein the organic solvent is an alcohol-based organic solvent having a water content of 5% or less. The method according to claim 1,
Wherein the heat treatment is performed at a temperature ranging from 300 to 600 ° C. for 3 to 10 hours. The method according to claim 1,
Wherein the metal salt is one selected from the group consisting of a metal alkoxide, a metal nitrate, a metal sulfate, and a mixture thereof. 11. The cathode active material according to any one of claims 1 to 10. 12. The method of claim 11,
And a lithium manganese oxide having a cubic spinel structure in which a part of the lithium manganese oxide in the layered structure in the complex oxide is changed between the composite oxide and the metaloid fluoride coating layer. 12. The method of claim 11,
Wherein the positive electrode active material has a specific surface area of 2 to 6 m ² / g. 12. The method of claim 11,
Wherein the coated metaloid fluoride has a thickness of 3 to 20 nm. A cathode comprising the cathode active material of claim 11;
A negative electrode comprising a negative electrode active material; And
An electrolyte existing between the anode and the cathode;
&Lt; / RTI &gt;

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