KR100775294B1 - Electrode active material and cell comprising the same - Google Patents

Abstract

The present invention is an electrode active material of the secondary particle state in which the active material of the primary particle state is bonded, the secondary particles are an electrode active material, characterized in that it comprises two or more different active materials in the primary particle state It relates to a battery. Since the secondary particles of the electrode active material according to the present invention includes two or more different active materials in the primary particle state, it is possible to maximize the advantages of each active material, and to provide a customized electrode active material that meets the purpose of the desired battery. This is possible.

Electrode active material, heat treatment

Description

Electrode active material and battery comprising same {Electrode active material and cell comprising the same}

1 illustrates an electrode active material prepared according to the prior art.

Figure 2 illustrates an electrode active material prepared according to an embodiment of the present invention.

The present invention relates to an electrode active material and a battery comprising the electrode active material.

LiCoO ₂ is widely used as a cathode active material in lithium ion secondary batteries. However, many studies have been conducted on new cathode active materials to solve the problem of price increase and safety due to limited resource conditions of Co and to achieve higher capacity.

Newly proposed cathode active materials include Ni-rich active materials containing excessive Ni, half-half active materials containing Ni-Mn, and active materials in which Co is added to Ni-Mn half-half active materials. The active material mixed with 1: 1: 1 of Mn-Co has reached the commercialization stage. Active materials having a structure other than the layered structure include a spinel manganese active material and an olivine active material.

However, in the case of Ni-rich active materials, the size of Li ⁺ ions and Ni ²⁺ ions are similar to cause Ni ions to enter the Li site, which is controlled in an oxidizing atmosphere, and LiNi _0.8 Al is used to solve the safety problem. _It solves the problems of Li-byproducts and safety that were originally recognized as problems by making them into the form of _0.05 Co _0.15 O ₂ , LiNi _0.8 Co _0.2 O ₂ , LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , or coating. Doing. However, because the rate (rate) is fundamentally poor, it should be solved in the form of secondary particles, and the safety is also much lower than that of Co-based.

In Ni-Mn-Co system, Ni ²⁺ and Mn ⁴⁺ form a stable transition metal state based on the half-half of Ni-Mn. LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.5 Mn _0.5 O ₂ . However, this composition is also difficult to synthesize by solid phase reaction because it must be mixed with various kinds of metals, it is possible to synthesize by using a wet method such as coprecipitation method or hydrothermal synthesis (in this process the primary particle size There is a problem that is difficult to form large. In addition, since the rate (rate) is fundamentally low, it goes through the method of forming secondary particles.

In particular, in such a rate characteristic, the size has a large influence, and the electrode active material has a good characteristic when composed of only small primary particles, but when it is aggregated into secondary particles, property degradation occurs. On the other hand, when composed of only primary particles there is a problem that the tap density is very low.

Olivine also has low conductivity, forming small particles, doping or carbon coating, but showing low rate characteristics. In the case of Mn-Spinel, there is a problem in that the safety is good but the capacity is much lowered.

Therefore, in order to make up for the problems of the respective active materials, the active materials are mixed in many cases, but they are not mixed between the respective primary particles, but are simply mixed between the secondary particles. Since the secondary particles are still in the state that the primary particles of the same composition are combined, it cannot be said that they have a perfect composition, and the performance and advantages of the respective active materials are not maximized. In addition, when composing the electrodes by mixing the active materials, it is important to mix the active materials uniformly, but there is a limit to the uniform mixing through mixing (mixing).

In the present invention, after generating the active material of the primary particle state having a different composition formula, respectively, to form the secondary particles by combining the primary particles of the active material, the secondary particles are at least two kinds of the active material of the primary particle state To include, to maximize the advantages of each of the active materials, to provide a custom active material that meets the purpose of the desired battery.

The present invention is an electrode active material of the secondary particle state in which the active material of the primary particle state is bonded, the secondary particles are an electrode active material, characterized in that it comprises two or more different active materials in the primary particle state Provide a battery. It also provides a method for producing the electrode active material.

Hereinafter, the present invention will be described in detail.

1 illustrates an electrode active material prepared according to the prior art, and illustrates an electrode active material formed by mixing an active material A and an active material B in a secondary particle state in which primary particles of the same type are combined. That is, the electrode active material to be prepared is made of a simple mixture of each active material that is already in the secondary particle state and has a low homogeneous state.

2 illustrates an electrode active material prepared according to an embodiment of the present invention, and shows an electrode active material in which an active material A in a primary particle state and an active material B in another primary particle state are combined to form secondary particles. . That is, the prepared electrode active material is a secondary particle electrode active material formed by combining different kinds of active materials having a small primary particle state, and has a high homogeneous state, and the composition of the electrode active material of FIG. Is completely different.

The active material in the primary particle state of the present invention is not limited as long as it forms secondary particles, but is preferably a synthetic heat treatment.

The electrode active material of the present invention may be heat treated after formation of the secondary particles. After formation of the secondary particles, it is preferable to heat-treat the electrode active material in order to maintain the secondary particle state.

When the heat treatment temperature is higher than the synthesis temperature of each of the active materials in the primary particle state, new synthesis may occur between each other to cause structural breakdown between the primary particles constituting the secondary particles.

Therefore, the heat treatment after the formation of the secondary particles, the heat treatment below the second lower temperature of the synthesis temperature of the different active materials in the primary particle state to be bonded, preferably the synthesis of different active materials in the primary particle state to be bonded Heat treatment can be performed below the lowest temperature among the temperatures.

In the present invention, the active material in the primary particle state may be selected from the group consisting of the following Chemical Formulas 1 to 3.

[Formula 1]

Li _1-a Ni _x Co _y Mn _z M _{1- (x + y + z)} O ₂

(-0.1 <a <0.1, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤x + y + z≤1, transition metal except M = Ni, Mn, Co)

[Formula 2]

Li _1-a Mn ₂ O ₄ (-0.1 <a <0.1)

[Formula 3]

Li _1-a Fe _1-x M _x (P _1-y A _y O ₄ )

(-0.1 <a <0.1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, M = Mn, at least one transition metal selected from the group consisting of Co, A = Ti, V, Si and Al Metal selected from

In Formula 1, M is a transition metal except Ni, Mn, and Co, and preferred examples thereof are Fe, V, Cr, Ti, Cu, Sc, Y, Zr, Nb, Mo, Pd, Ag, Au, Pt, Ir, Os, W, or Ta.

At least one of the active materials of Chemical Formulas 1 to 3 includes at least one element selected from the group consisting of Al, Mg, Ca, Sr, Ba, Ga, In, Tl, and B in an amount of more than 0 wt% and not more than 5 wt%. It may be doped with (doping). Doping the metal site with the element may bring about structural stabilization of the active material. However, as the amount of doping increases, the capacity of the active material decreases, and particularly, when the doping exceeds 5wt%, a sudden decrease in capacity may occur.

In addition, any one or more of the active materials of Chemical Formulas 1 to 3 may be doped in the oxygen site with one or more halogen elements selected from the group consisting of F, Cl, Br, and I more than 0wt% to 5wt% or less. have. Doping oxygen sites with the halogen element may lead to structural stabilization of the active material. However, as the amount of doping increases, the capacity of the active material decreases, and in particular, when the doping exceeds 5wt%, a sudden capacity decrease may occur.

Electrode active material according to the present invention comprises the steps of forming a slurry by mixing two or more active materials and a solvent in the primary particle state; And granulating the slurry to form granules of secondary particles.

In addition, after the forming of the granules, the electrode active material may be further prepared by further comprising the step of heat-treating the granules.

As the solvent, various organic solvents and water may be used, and non-limiting examples include ethanol, methanol, water, acetone, and the like.

The granulation (granulation) can be used for all commonly used granulation method, for example spray spray (spray dry) method.

The battery of the present invention may be made by including the electrode active material provided according to the present invention as a positive electrode active material or a negative electrode active material.

As an example of a method for producing an electrode including the electrode active material of the present invention, a paste (slurry) is prepared by mixing and stirring a binder and a solvent, a conducting agent, and a dispersant in the electrode active material of the present invention, if necessary, and then a metal material. The positive electrode or the negative electrode may be prepared by coating on a current collector, compressing, and drying.

The binder may be suitably used in an amount of 1 to 10 wt% and a conductive agent in an amount of 1 to 30 wt% with respect to the electrode active material of the present invention.

Representative examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF) or a copolymer thereof, cellulose, cellulose, SBR (styrene butadiene rubber), and as a solvent, NMP ( Organic solvents such as N-methyl pyrrolidone), DMF (dimethyl formamide) or water can be used.

Generally, carbon black may be used as the conductive agent, and acetylene black series (such as a Chevron Chemical Company or Gulf Oil Company) may be used as a commercially available product. Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MMM) There is this.

The current collector of the metal material is a metal having high conductivity, and any metal can be used as long as the paste of the material is easily adhered and is not reactive in the voltage range of the battery. Representative examples include meshes, foils, and the like, which are manufactured by aluminum, copper, gold, nickel or an aluminum alloy or a combination thereof.

The method of apply | coating the paste of an electrode material to a metal material can be selected from a well-known method in consideration of the characteristic of a material, or can be performed by a new suitable method. Such an example is to distribute the paste onto the current collector and then to uniformly disperse the same using a doctor blade or the like. In some cases, a method of distributing and dispersing in one process may be used. In addition, die casting, comma coating, and screen printing can be selected. Alternatively, after molding on a separate substrate, it can be bonded to the current collector by pressing or lamination.

Non-limiting examples of the method of drying the applied paste may be dried in a vacuum oven at 50 to 200 ℃ for 0.5 to 3 days.

On the other hand, the battery of the present invention can be produced by a method known in the art using a positive electrode or a negative electrode prepared using the electrode active material prepared according to the present invention, it is not particularly limited. For example, the separator may be placed between the positive electrode and the negative electrode to add a nonaqueous electrolyte. In addition, the positive electrode, the separator and the nonaqueous electrolyte and, if necessary, other additives, may be those known in the art.

In addition, a porous separator may be used as a separator in manufacturing a battery of the present invention, and for example, a polypropylene-based, polyethylene-based, or polyolefin-based porous separator may be used, but is not limited thereto.

The nonaqueous electrolyte may include a nonaqueous solvent and an electrolyte salt.

The nonaqueous solvent included in the nonaqueous electrolyte is not particularly limited as long as it is usually used as a nonaqueous solvent for the nonaqueous electrolyte, and may include a cyclic carbonate and / or a linear carbonate. Examples of the cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (GBL), and the like. Examples of such linear carbonates include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methyl propyl carbonate (MPC), and the like. These nonaqueous solvents can be used individually or in mixture of 2 or more types.

The electrolyte salt used for the electrolyte solution is not particularly limited as long as it is usually used as an electrolyte salt for nonaqueous electrolyte solution. Electrolytic salt, non-limiting example, A ⁺ B ^- A salt of the structure, such as, A ⁺ comprises a Li ^+, Na ^+, an alkali metal cation or an ion composed of a combination thereof, such as K ⁺ B ^- is PF ₆ ^{- _{, BF 4 -, Cl -,}} Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2 ) ₃ ^- and a salt containing the same anion ion or a combination thereof. In particular, the use of lithium salts is preferred. These electrolyte salts can be used individually or in mixture of 2 or more types.

In addition, the external shape of the battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type or coin type using a can.

Hereinafter, the present invention will be described in detail with reference to the following Examples. However, the following examples are merely to illustrate the present invention and the present invention is not limited by the following examples.

(Example 1)

LiNi _1/3 Mn _1/3 Co _1/3 O ₂ primary particles having a size of 0.5 to 1.0 μm and LiCoO ₂ primary particles having a size of 1 to 2 μm were weighed in a weight ratio of 1: 1, and then ethanol The slurry was put into a container containing a ball mill to mix the two materials well. The resulting slurry was granulated to 10 탆 using a spray drying granulator. The obtained granules were placed in a 500 ° C. furnace and heat-treated for 5 hours to obtain a final electrode active material.

2.5 parts by weight of a conductive agent (Super P carbon black) and 2.5 parts by weight of a binder (PVDF) were mixed with 95 parts by weight of the obtained electrode active material, and put into NMP to form a slurry, followed by coating on 18 μm Al-foil to obtain an electrode. The obtained electrode was punched into a coin type to manufacture a coin type battery. Li-metal was used as a counter electrode of the manufactured battery, and an electrolyte solution containing 1 M of LiPF ₆ in an EC: EMC 1: 2 solution was used as an electrolyte.

(Comparative Example 1)

The size of each 10㎛ _{LiNi 1/3 Mn 1/3 Co 1/3 O 2} 2 primary particles and primary particles LiCoO ₂ 2 weight ratio of 1: 1 except that in Example 1 with an electrode active material and the battery in the same manner Was produced.

Experiment 1 Packing Density Measurement

2.5g of the electrode active material prepared in Example 1 was placed in a mold having a diameter of 1.5cm and pressed for 3 minutes at a pressure of 4000pa. Then, the thickness of the mold was measured and the thickness of the active material was measured by measuring the thickness of the mold without the active material. It was.

Experiment 2 Packing Density Measurement

The thickness of the active material was calculated by measuring in the same manner as in Experiment 1 with the mixed active material before granulation in Example 1.

Since the secondary particles of the electrode active material according to the present invention includes two or more different active materials in the primary particle state, it is possible to maximize the advantages of each active material, and to provide a customized electrode active material that meets the purpose of the desired battery. This is possible.

Claims (11)

An electrode active material in a secondary particle state in which an active material in a primary particle state is bonded, wherein the secondary particles include two or more different active materials in the primary particle state. The electrode active material according to claim 1, wherein the active material in the primary particle state is subjected to synthetic heat treatment before bonding to the secondary particles. The electrode active material according to claim 1, wherein the electrode active material is heat-treated after formation of secondary particles. The electrode active material according to claim 1, wherein the electrode active material is heat-treated at a temperature lower than a second lower temperature among the synthesis temperatures of different active materials in the state of primary particles to be bonded after formation of secondary particles. The electrode active material according to claim 1, wherein the electrode active material is heat-treated at the lowest temperature among the synthesis temperatures of different active materials in the state of the primary particles to be bonded after the formation of the secondary particles. The electrode active material according to claim 1, wherein the active material in the primary particle state is selected from the group consisting of the following Chemical Formulas 1 to 3. [Formula 1] Li _1-a Ni _x Co _y Mn _z M _{1- (x + y + z)} O ₂ (-0.1 <a <0.1, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤x + y + z≤1, transition metal except M = Ni, Mn, Co) [Formula 2] Li _1-a Mn ₂ O ₄ (-0.1 <a <0.1) [Formula 3] Li _1-a Fe _1-x M _x (P _1-y A _y O ₄ ) (-0.1 <a <0.1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, M = Mn, at least one transition metal selected from the group consisting of Co, A = Ti, V, Si and Al Metal selected from) According to claim 6, At least one of the active material of Formula 1 to Formula 3 is 0wt 1 or more elements selected from the group consisting of Al, Mg, Ca, Sr, Ba, Ga, In, Tl and B in the metal site An electrode active material, characterized in that the doping (doping) more than 5% by weight or less. The method according to claim 6, wherein any one or more of the active materials of Formula 1 to Formula 3 doped at least one halogen element selected from the group consisting of F, Cl, Br, and I in the oxygen site more than 0wt% to 5wt% ( electrode active material, characterized in that the doping). A battery comprising the electrode active material of any one of claims 1 to 8. Mixing at least two active materials and a solvent in a primary particle state to form a slurry; And granulating the slurry to form granules of secondary particles, wherein the electrode active material according to any one of claims 1 to 8 is prepared. The method of claim 10, further comprising, after forming the granules of the secondary particles, heat treating the granules.

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