WO2020111807A1 - Cathode active material for lithium secondary battery and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a method for manufacturing a cathode active material for a lithium secondary battery from a recovered cathode active material and a cathode active material for a lithium secondary battery manufactured thereby. In the manufacturing method for a cathode active material for a lithium secondary battery from a recovered cathode active material according to the present invention, a desired composition for the cathode active material can be prepared by adding a metal raw material to the recovered cathode active material as necessary and prepared into pellet forms which are then fired to adjust the diameters thereof within a predetermined range. The lithium secondary battery comprising the recovered cathode active material of the present invention can have improved packing density properties and charge-discharge characteristics.

Description

Positive electrode active material for lithium secondary battery and method for manufacturing same

The present invention relates to a cathode active material for a lithium secondary battery and a method for manufacturing the same, and more particularly, to a cathode active material for a lithium secondary battery in a primary particle state and a method for manufacturing the same.

The battery is to generate electric power by using a material capable of electrochemical reaction on the positive electrode and the negative electrode. A representative example of such a battery is a lithium secondary battery that generates electrical energy by changing a chemical potential when lithium ions are intercalated/deintercalated at the positive electrode and the negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation/deintercalation of lithium ions as a positive electrode and a negative electrode active material, and charging an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

The positive electrode active material is a material that plays the most important role in battery performance and safety of a lithium secondary battery, and a chalcogenide compound is used, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x Composite metal oxides such as O ₂ (0<x<1) and LiMnO ₂ have been studied. Among the positive electrode active materials, Mn-based positive electrode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are also easy to synthesize, relatively inexpensive, and have less pollution to the environment, but are attractive materials, but have a small capacity. Co-based positive electrode active materials such as LiCoO ₂ have good electrical conductivity, high battery voltage, and excellent electrode characteristics, but have the disadvantage of being expensive. In addition, the development of other positive electrode materials is desired because Co has low reserves and is expensive and has toxicity to the human body. In addition, the crystal structure is unstable due to de-lithium during charging, and thus has a disadvantage in that the thermal properties are very poor.

In order to improve this, many attempts have been made to replace a portion of nickel with a transition metal element, to shift the heating start temperature to the high temperature side, or to broaden the heating peak in order to prevent sudden heating. That is, in the case of a LiNi _1-x Co _x O ₂ (x=0.1-0.3) material in which a part of nickel is substituted with cobalt, excellent charge/discharge characteristics and life characteristics are shown, but thermal safety problems have not been solved. Further, as well as in European Patent No. 0.87245 million of the other metals as well as Co and Mn to Ni spot substituted _{Li a Co b Mn c M d} Ni 1- (b + c + d) O 2 (M = B, Al, Si. Fe, Cr, Cu, Zn, W, Ti, Ga) types have been disclosed, but the thermal stability of Ni-based still has not been solved.

Recently, as the production and use of lithium secondary batteries for electric vehicles have increased, the amount of their disposal will also increase, so the need for reprocessing and recycling of waste lithium secondary batteries for its treatment has emerged. In addition, in the industry related to secondary batteries and materials, competition to reduce the production cost of products is fierce, making efforts for low-cost raw materials, low-cost processes, and yield improvement, as well as increasing demand for secondary batteries. There are increasing attempts to recycle defective products, electrodes, and the like.

The method of reprocessing the metal oxide-based positive electrode active material of the lithium secondary battery reported so far has been studied by a dry treatment method by high-temperature melting, which has the advantage of being capable of mass processing, but is used to decompose each valuable metal component in a molten state. There is a disadvantage in that the purity is lowered and a second refining process through wet processing is required. In addition, in the case of recovering valuable metals through wet smelting, the positive electrode plate is separated from the waste-lithium secondary battery, the waste-anode active material is recovered after physical treatment, and then leached with acid such as sulfuric acid, nitric acid, hydrochloric acid to ionize metal components. For selective metal ion recovery afterwards, additional treatment processes such as solvent extraction are not only involved, but also a large amount of waste water is generated, and acid vapors that evaporate and diffuse into the atmosphere by using a large amount of acid cause serious environmental pollution and equipment corrosion. The back problem is serious. In addition, there is a disadvantage that it is not economical due to the high investment cost of facilities and facilities for recovering valuable metals.

An object of the present invention is to provide a method of manufacturing a positive electrode active material for a recycled lithium secondary battery of a new method in order to solve the problems of the positive electrode active material recycling technology that needs to be melted and recycled as described above.

Another object of the present invention is to provide a new positive electrode active material produced by the production method of the present invention and capable of exhibiting a high packing density with a uniform particle size.

The present invention provides a positive electrode active material in the form of primary particles, that is, a plurality of non-bonded primary particles in order to solve the above problems.

In the case of a conventional positive electrode active material, a plurality of primary particles aggregate to form a secondary particle structure, whereas in the present invention, the term “primary particle positive electrode active material” means that each primary particle is not bound to each other. 10 shows a positive electrode active material for a lithium secondary battery according to the present invention. As shown in FIG. 10, unlike the conventional positive electrode active material showing a form of secondary particles in which a plurality of primary particles are aggregated, the positive electrode active material of the present invention is composed of only individual primary particles that are not aggregated.

The particle diameter of the “primary particle-shaped positive electrode active material” according to the present invention is characterized in that it is 3 to 20 um.

The positive electrode active material for a lithium secondary battery in a primary particle state prepared from the recycled positive electrode active material represented by the following Chemical Formula 1 according to the present invention is characterized by being represented by the following Chemical Formula 2.

[Chemical Formula _{2] Li 1 + a 'Ni} b' Co c 'M 1- (b' + c ') O 2

(In Formula 2, -0.1≤a'≤0.5, 0.05≤b'≤0.8, 0.05≤c'≤0.5, b'+c'≤1, M is Mn, Al, Mg, Ni, Co, Fe, It is one or more elements selected from the group consisting of Ti, V, Zr and Zn)

The'primary particle state positive electrode active material' according to the present invention is characterized by including a cation mixed layer. The cation may mean Li ⁺ and Ni ²⁺ in the embodiment according to the present invention. Depending on the degree of cation mixing in the positive electrode active material structure of Li ⁺ and Ni ²⁺ , reversible capacity and life characteristics can be improved.

The present invention also

Solid-phase mixing of recycled positive electrode active material and metal raw material as raw materials;

Preparing the mixture into pellets;

Heat-treating the pellets to obtain a lithium composite oxide; And

It provides a method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material comprising; crushing the pellets.

The method of manufacturing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention is a technical feature of producing a positive electrode active material for a lithium secondary battery using a recycled positive electrode active material that has been subjected to one or more charge and discharge processes as a raw material.

In the manufacturing method according to the present invention, the recycled positive electrode active material as a raw material may be used without limitation as long as it is a positive electrode active material that has been subjected to one or more charge/discharge processes, and may be specifically represented by Chemical Formula 1 as follows.

[Formula 1] Li _1+a Ni _b Co _c M _1-(b+c) O ₂

(In Formula 1, -0.1≤a≤0.5, 0≤b≤0.8, 0≤c≤0.8, b+c≤1, M is Mn, Al, Mg, Ni, Co, Fe, Ti, V, Zr And Zn is at least one element selected from the group consisting of).

That is, in the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the recycled positive electrode active material can be used without limitation as long as it contains Ni, and a plurality of recycled positive electrode active materials can be mixed and used. .

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the metal raw material mixed with the recycled positive electrode active material is not only a lithium raw material, but also various metal materials, such as manganese, aluminum, magnesium, nickel, cobalt, It is characterized by being a material comprising at least one metal selected from the group consisting of iron, titanium, vanadium, zirconium and zinc.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, in the step of preparing the mixture into pellets, the pellet is produced by applying a pressure of 10 to 500 Mpa of compressive strength.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the step of manufacturing the mixture into pellets is a pelletizer, a high pressure press, a hot press , It is characterized in that it is performed using an extruder (extruder) or kneading (kneading) equipment.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the density of the pellets in the step of manufacturing the mixture into pellets is characterized in that 1 to 5 g / cc.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the step of calcining the pellets by heat treatment is characterized in that it is carried out at 500 to 1,500 ℃.

In the method of manufacturing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the step of pulverizing the pellets may include classifying the calcined pellets.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the step of pulverizing or classifying the fired pellets includes a ball mill, an attrition mill, and a disc mill ( It is characterized in that it is carried out by a method that is a disk mill, jet mill (jet mill), jaw crusher, crusher (crusher), classifier (sieve) or a combination thereof.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the lithium raw material in the step of solid-phase mixing the recycled positive electrode active material and the lithium raw material containing Ni is LiOH, Li ₂ O , Li ₂ CO ₃ , Li ₂ SO ₄ and Li-acetate.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the step of solid-phase mixing the recycled positive electrode active material and the lithium raw material is characterized by further mixing the Ni raw material.

In the method for producing a positive electrode active material for a lithium secondary battery from the recycled positive electrode active material according to the present invention, the Ni raw material includes at least one material selected from the group consisting of Ni(OH) ₂ , NiSO ₄ , NiO and Ni-acetate It is characterized by.

The present invention also provides a positive electrode active material for a lithium secondary battery produced from recycled positive electrode active material by the production method of the present invention.

The method for manufacturing a positive electrode active material for a lithium secondary battery in a primary particle state represented by Formula 2 prepared from the recycled positive electrode active material represented by Chemical Formula 1 according to the present invention includes the number of moles of lithium of the lithium raw material added, x, Ni raw material When the number of moles of nickel is y, the molar ratio of lithium and nickel in the recycled positive electrode active material as the raw material represented by Chemical Formula 1 and the positive electrode active material in the primary particle state represented by Chemical Formula 2 produced by the production method according to the present invention The molar ratio of lithium and nickel is characterized by satisfying the following equation.

a’ = a + x

b’ = b + y

The method of manufacturing a positive electrode active material for a lithium secondary battery in a primary particle state from the recycled positive electrode active material according to the present invention uses a recycled positive electrode active material as a raw material, and if necessary, adds a metal raw material including lithium raw material, nickel raw material and other metal Lithium secondary battery comprising a positive electrode active material prepared according to the present invention can be prepared in a'primary particle state positive electrode active material', the particle size is adjusted to a certain range by firing after being produced in a pellet shape, the charging density characteristics And charging/discharging characteristics are improved.

1 is a schematic diagram showing the method of manufacturing the positive electrode active material of the present invention step by step.

2 to 4 show SEM pictures of the positive electrode active material prepared in one embodiment and a comparative example of the present invention.

5 and 6 show the XRD measurement results of the positive electrode active material prepared in Examples and Comparative Examples of the present invention.

7 to 9 show the results of measuring the electrochemical properties of the positive electrode active material prepared in Examples and Comparative Examples of the present invention.

10 shows the structure of a typical positive electrode active material.

Hereinafter, the present invention will be described in more detail by examples. However, the present invention is not limited by the following examples.

<Example 1>

LiNi _0.6 Co _0.2 Mn _0.2 containing a molar ratio of Ni:Co:Mn of 6:2:2 is mixed with LiOH as a lithium source and Ni(OH) ₂ as a nickel source in a solid phase, thereby mixing LiNi _0.7 Co _0.15 Mn _0.15 O ₂ The composition was mixed while stirring for 1 hour or more.

The pulverized particles were prepared in a pellet shape, compressed for 10 sec at 30 Mpa pressure, based on 1 g powder, and then heat treated at 980° C. for 20 hours, then heat treated at 900° C. for 5 hours, and the pellets were crushed into particles.

<Comparative Example 1>

LiNi _0.6 Co _0.2 Mn _0.2 containing a molar ratio of Ni:Co:Mn of 6:2:2 is mixed in a solid phase while stirring LiOH as a lithium source and Ni(OH) ₂ as a nickel source for 1 hour or more, and pellet shape It was heat-treated at 980°C for 20 hours in a pulverized state without being prepared, heat-treated at 900°C for 5 hours, and the pellets were crushed into particles.

<Experimental Example> SEM photograph measurement

The SEM photographs of the particles prepared in Example 1 and Comparative Example 1 were measured, and the results are shown in FIGS. 2 to 4.

As shown in Figure 2, in the case of the positive electrode active material in the primary particle state prepared according to the embodiment of the present invention, it was confirmed that the positive electrode active material in the primary particle state having an average particle size of 3 to 5 um.

In FIG. 3, in the case of Comparative Example 1 in which pellets were not prepared, it was confirmed that the primary particles were aggregated secondary particles and were not prepared as a cathode active material in a primary particle state.

In FIG. 4, it can be confirmed that even when a lithium source or a nickel source is not added, it is manufactured in a pellet shape and then heat-treated and pulverized to produce a cathode active material in a primary particle state.

<Experimental Example> XRD measurement

The SEM photographs of the particles prepared in Example 1 and Comparative Example 1 were measured, and the results are shown in FIGS. 5 and 6.

As shown in FIG. 5, it was confirmed that the positive electrode active material prepared in the embodiment of the present invention was a positive electrode active material in an undetected primary particle state with an impurity-related peak in the same XRD pattern as a normal layered positive electrode active material.

In addition, as shown in FIG. 6, it was confirmed that the peak intensity detected at 2θ=45 was higher than that of the example of the present invention in the case of the comparative example not prepared from pellets.

<Production Example> Preparation of lithium secondary battery

A battery was manufactured using the positive electrode active material prepared in Example 1 and Comparative Example 1.

A slurry was prepared by mixing the positive electrode active material prepared in Example 1 and Comparative Example 1 with super-P as a conductive material and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 8:1:1, respectively. The slurry was uniformly applied to an aluminum foil having a thickness of 15 μm, and vacuum dried at a temperature of 120° C. to prepare an anode.

The prepared positive electrode and lithium foil are used as counter electrodes, and a liquid electrolyte solution in which LiPF ₆ is dissolved at a concentration of 1.0 M in a solvent in which a porous polyethylene membrane carbonate, ethylmethyl carbonate, and dimethyl carbonate is mixed in a volume ratio of 3:4:3 is used. Thus, a half cell was prepared according to a commonly known manufacturing process.

<Experimental Example> Measurement of battery characteristics-Charging and discharging characteristics

The charge and discharge characteristics of the battery containing the active material of Example 1 recycled and manufactured according to an embodiment of the present invention were measured and the results are shown in Table 1 below.

As a comparative example, as a result of using a commercially available product LiNi _0.7 Co _0.1 Mn _0.1 O ₂ composition, it can be confirmed that the charge and discharge characteristics of the cathode active material and commercially available products produced and recycled according to the examples of the present invention are similar.

	Example 1	Comparative Example 1
CHG(mAh/g)	205	210
DIS(mAH/g)	185	190
C.E.(%)	90.2	90.5

<Example 2>

LiNi _0.84 Co _0.14 Al _0.02 LiCoO ₂ per 1 mol was solid-phase mixed at a ratio of 0.33 mol to make a composition of LiNi _0.63 Co _0.355 Al _0.015 O ₂ and mixed with stirring for 1 hour or more.

Prepared in the form of pellets, and pressed for 10 sec at 30 Mpa pressure based on 1 g powder, and then heat treated at 900° C. for 5 hours, and the pellets were crushed into particles.

<Comparative Example 2>

LiNi _0.84 Co _0.14 Al _0.02 LiCoO ₂ was mixed in a solid phase at a ratio of 0.33 mol to the positive electrode active material and mixed with LiNi _0.63 Co _0.355 Al _0.015 O ₂ composition for 1 hour or more while stirring.

It was heat treated at 900° C. for 5 hours in a pulverized state without being prepared in a pellet shape, and the pellet was pulverized into particles.

<Production Example> Preparation of lithium secondary battery

A battery was manufactured using the positive electrode active material prepared in Example 2.

A slurry was prepared by mixing the positive electrode active material prepared in Example 2 and Comparative Example 2 with super-P as a conductive material and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 8:1:1, respectively. The slurry was uniformly applied to an aluminum foil having a thickness of 15 μm, and vacuum dried at a temperature of 120° C. to prepare an anode.

The prepared positive electrode and lithium foil are used as counter electrodes, and a liquid electrolyte solution in which LiPF ₆ is dissolved at a concentration of 1.0M in a solvent in which a porous polyethylene membrane carbonate, ethylmethyl carbonate, and dimethyl carbonate is mixed in a volume ratio of 3:4:3 is used. Thus, a half cell was prepared according to a commonly known manufacturing process.

<Experimental Example> Measurement of battery characteristics-Charging and discharging characteristics

Charge and discharge characteristics of the battery containing the active material of Example 2 recycled and manufactured according to an embodiment of the present invention were measured and the results are shown in FIGS. 7 to 9.

Claims (14)

1. Comprising a plurality of primary particles that are not aggregated with each other,

   Positive electrode active material for lithium secondary batteries.
2. According to claim 1,

   The particle size of the positive electrode active material for a lithium secondary battery is 3 to 20 um,

   Positive electrode active material for lithium secondary batteries.
3. According to claim 1,

   The positive electrode active material for a lithium secondary battery would include a cation mixed layer,

   Positive electrode active material for lithium secondary batteries.
4. Mixing a first positive electrode active material and a metal raw material;

   Preparing the mixture into pellets;

   Heat-treating the pellets to obtain a lithium composite oxide; And

   Comprising the step of grinding the pellet; containing,

   Method for producing a positive electrode active material for a lithium secondary battery according to claim 1.
5. The method of claim 4,

   The metal raw material is a material containing at least one metal selected from the group consisting of lithium, manganese, aluminum, magnesium, nickel, cobalt, iron, titanium, vanadium, zirconium and zinc,

   Method for manufacturing a positive electrode active material for a lithium secondary battery.
6. The method of claim 4,

   The first positive electrode active material is represented by the following formula (1),

   Method for manufacturing a positive electrode active material for a lithium secondary battery.

   [Formula 1] Li _1+a Ni _b Co _c M _1-(b+c) O ₂

   (In the above formula 1 -0.1≤a≤0.5, 0≤b≤0.8, 0≤c≤0.8, b + c≤1, M is Mn, Al, Mg, Ni, Co, Fe, Ti, V, Zr And Zn is one or more elements selected from the group consisting of)
7. The method of claim 4,

   In the step of preparing the mixture into pellets, the pellets are prepared by compression with a compressive strength of 1 to 20 ton/cm ² .

   Method for manufacturing a positive electrode active material for a lithium secondary battery.
8. The method of claim 4,

   The step of preparing the mixture into pellets is carried out using a pelletizer, a high pressure press, a hot press, an extruder or a kneading equipment,

   Method for manufacturing a positive electrode active material for a lithium secondary battery.
9. The method of claim 4,

   In the step of preparing the mixture into pellets, the density of the pellets is 10 to 20 g/cc,

   Method for manufacturing a positive electrode active material for a lithium secondary battery.
10. The method of claim 4,

    The step of calcining the pellets by heat treatment is performed at 700 to 1,500°C.

    Method for manufacturing a positive electrode active material for a lithium secondary battery.
11. The method of claim 4,

    The step of pulverizing the calcined pellets includes a ball mill, an attrition mill, a disk mill, a jet mill, a jaw crusher, and a crusher. , Is performed by a method that is a classifier (sieve) or a combination thereof,

    Method for manufacturing a positive electrode active material for a lithium secondary battery.
12. The method of claim 4,

    The step of grinding the pellets includes classifying the pellets,

    Method for manufacturing a positive electrode active material for a lithium secondary battery.
13. The method of claim 4,

    The raw material containing lithium as the metal raw material is selected from the group consisting of LiOH, Li ₂ O, Li ₂ CO ₃ and Li ₂ SO ₄ ,

    Method for manufacturing a positive electrode active material for a lithium secondary battery.
14. The method of claim 4,

    The raw material containing nickel as the metal raw material is selected from the group consisting of Ni(OH) ₂ , NiSO ₄ , NiO and Ni-acetate,

    Method for manufacturing a positive electrode active material for a lithium secondary battery.

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