阅读说明：本技术 从废正极材料分离过渡金属的方法 (Method for separating transition metal from waste positive electrode material ) 是由 郑元植 李泰荣 崔桓营 于 2020-12-15 设计创作，主要内容包括：本发明涉及一种从废正极材料分离过渡金属的方法,其中所述方法包括：步骤1：准备由式1表示的废正极材料；步骤2：在非活性气体气氛或氧气气氛中对所述废正极材料进行热处理,以将所述废正极材料相分离为锂氧化物和金属氧化物；步骤3：将步骤2所得的产物在惰性气氛中冷却至室温；以及步骤4：将步骤3中的冷却至室温的冷却产物与蒸馏水混合,然后过滤混合物以浸出过渡金属。(The present invention relates to a method for separating a transition metal from a waste positive electrode material, wherein the method comprises: step 1: preparing a waste positive electrode material represented by formula 1; step 2: heat-treating the waste positive electrode material in an inert gas atmosphere or an oxygen atmosphere to phase-separate the waste positive electrode material into lithium oxide and metal oxide; and step 3: cooling the product obtained in the step 2 to room temperature in an inert atmosphere; and step 4: the cooled product cooled to room temperature in step 3 is mixed with distilled water, and then the mixture is filtered to leach out the transition metal.)

1. A method of separating a transition metal from a spent positive electrode material, the method comprising:

step 1: preparing a waste positive electrode material represented by the following formula 1;

step 2: heat-treating the waste positive electrode material in an inert gas atmosphere or an oxygen atmosphere to phase-separate the waste positive electrode material into lithium oxide and metal oxide;

and step 3: cooling the product obtained in the step 2 to room temperature in an inert atmosphere; and

and 4, step 4: mixing the cooled product cooled to room temperature in step 3 with distilled water, and then filtering the mixture to leach out the transition metal:

[ formula 1]

Li_1+aNi_1-xM_xO₂

Wherein in the above formula 1, the first and second groups,

m is one or more selected from the following: the components of Co, Mn and Al,

0≤a≤0.3，0≤x≤0.5。

2. the method according to claim 1, wherein in step 2, the heat treatment is performed at 900 ℃ or more in an oxygen atmosphere.

3. The method of claim 2, wherein the heat treatment is performed at 900 ℃ to 1000 ℃ in the oxygen atmosphere.

4. The method according to claim 1, wherein in step 2, the heat treatment is performed at 800 ℃ or higher in an inert gas atmosphere.

5. The method of claim 4, wherein the heat treatment is performed at 800 ℃ to 950 ℃ in the inert gas atmosphere.

6. The method of claim 4, wherein the inert gas atmosphere of step 2 further comprises hydrogen in an amount of 10 vol% or less, based on 100 vol% of inert gas.

7. The method of claim 1, wherein the spent positive electrode material of step 1 comprises 80 mol% or more nickel, based on total moles of transition metals other than lithium.

8. The method of claim 1, wherein during the cooling of step 3, the ramp down rate is from 1 ℃/minute to 10 ℃/minute.

9. The method of claim 1, wherein in step 4, the cooled product is mixed with the distilled water in a ratio of 1: 0.3 to 1: 2, and mixing.

10. The method of claim 1, wherein the transition metal leached in step 4 is in the form of a lithium compound comprising a lithium hydroxide formed by reaction of the lithium oxide with the distilled water.

11. The process of claim 1, wherein the transition metal leached in step 4 is in the form of nickel metal oxide comprising nickel and M (wherein M is one or more selected from the group consisting of Co, Mn and Al).

12. The method of claim 1, wherein steps 1-4 are repeated 1-4 times.

13. The method according to claim 1, wherein the transition metal is determined to have a purity of 80% or more when a unit cell size obtained by measuring the transition metal separated in step 4 by XRD is 0.42nm to 0.4165 nm.

Technical Field

This application claims the benefit of korean patent application No. 10-2019-0168318, filed on 16.12.2019 with the korean intellectual property office, the disclosure of which is incorporated herein by reference in its entirety.

The present invention relates to a method for separating transition metals from waste positive electrode materials.

Background

A lithium secondary battery is generally composed of a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and an electrolyte, and is a secondary battery that is charged and discharged by intercalation-deintercalation of lithium ions. Lithium secondary batteries have advantages of high energy density, high electromotive force, and large capacity, and are therefore used in various fields.

The positive active material of the lithium secondary battery includes lithium and transition metals such as nickel, cobalt, manganese, and the like. Nickel and cobalt are relatively expensive metals, and in particular, the number of countries producing cobalt is limited, so that cobalt is referred to as a metal whose supply and demand are unstable worldwide. Therefore, when the transition metal including lithium and cobalt is recovered from the waste electrode, particularly the positive electrode, and recycled as a raw material, price competitiveness may be secured and additional revenue may be generated. Therefore, a method of recovering and recycling metal components from the waste electrodes has been studied.

Conventionally, in order to recover metal components from waste electrodes, a method of extracting transition metals by dissolving a positive electrode active material in a chemical solvent such as an acid solvent or an organic solvent has been used. However, when a chemical solvent is used as described above, there is a problem of environmental pollution.

Therefore, a separation method capable of suppressing the problem of environmental pollution when separating a transition metal from a waste positive electrode is required.

< Prior Art document >

(patent document 1) Korean patent laid-open publication No. 1497921

Disclosure of Invention

Technical problem

In order to solve the above problems, a first aspect of the present invention provides a method capable of easily separating a transition metal from a waste positive electrode material in a dry manner without causing environmental pollution problems.

Technical scheme

According to an aspect of the present invention, there is provided a method of separating a transition metal from a waste positive electrode material, wherein the method comprises: step 1: preparing a waste positive electrode material represented by the following formula 1; step 2: heat-treating the waste positive electrode material in an inert gas atmosphere or an oxygen atmosphere to phase-separate the waste positive electrode material into lithium oxide and metal oxide; and step 3: cooling the product obtained in the step 2 to room temperature in an inert atmosphere; and step 4: the cooled product cooled to room temperature in step 3 is mixed with distilled water, and then the mixture is filtered to leach out the transition metal.

[ formula 1]

Li_1+aNi_1-xM_xO₂

In formula 1 above, M is one or more selected from the group consisting of: a is more than or equal to 0 and less than or equal to 0.3, and x is more than or equal to 0 and less than or equal to 0.5.

Advantageous effects

According to the present invention, the transition metal is separated from the waste cathode material through the structural change caused by the heat treatment, so that the problem of environmental pollution caused by the use of a chemical solvent can be prevented in advance, and the transition metal can be easily separated from the waste cathode material.

Drawings

Fig. 1 (a) to (c) are graphs showing XRD data representing the structural change of the waste cathode material manufactured in example 1 according to temperature;

fig. 2 (a) to (c) are graphs showing XRD data measured after separating transition metals from the waste cathode materials manufactured in (a) example 1, (b) example 2, and (c) comparative example 1, respectively.

Detailed Description

Hereinafter, the present invention will be described in more detail.

It will be understood that the words or terms used in the specification and claims of this invention should not be construed as limited to having the meanings defined in commonly used dictionaries. It will be further understood that the terms or terms should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the technical idea of the present invention, on the basis of the principle that the inventor may appropriately define the meaning of the terms or terms in order to best explain the present invention.

Method for separating transition metal from waste positive electrode material

According to the present invention, in order to separate a transition metal from a waste positive electrode material, the following steps are included:

step 1: preparing a waste positive electrode material represented by the following formula 1; step 2: heat-treating the waste positive electrode material in an inert gas atmosphere or an oxygen atmosphere to phase-separate the waste positive electrode material into lithium oxide and metal oxide; and step 3: cooling the product obtained in the step 2 to room temperature in an inert atmosphere; and step 4: the cooled product cooled to room temperature in step 3 is mixed with distilled water, and then the mixture is filtered to leach out the transition metal.

Hereinafter, each step of the present invention will be described in more detail.

First, a waste positive electrode material is prepared (step 1).

In the present invention, the waste cathode material may be derived from an electrode having defects generated during the manufacturing process of the secondary battery, or may be derived from an electrode separated from a used secondary battery, which is then discarded. Specifically, the waste cathode material may be, for example, a waste cathode material having a coating defect generated during the coating of the electrode active material slurry, or an off-specification waste cathode material, or may be derived from an electrode in which a set expiration date expires during storage among manufactured electrodes.

In particular, when the waste cathode material is used as in the present invention, the benefit of recycling the active material may be greater than the benefit of recycling the waste anode material.

For example, the waste cathode material according to the present invention may be represented by the following formula 1, and preferably, nickel may be contained at 60 mol% or more based on the total moles of transition metals other than lithium.

[ formula 1]

Li_1+aNi_1-xM_xO₂

In formula 1 above, M is one or more selected from the group consisting of: a is more than or equal to 0 and less than or equal to 0.3, and x is more than or equal to 0 and less than or equal to 0.5.

Specifically, in formula 1 above, M is an element replacing Ni sites in the oxide represented by formula 1, and may include one or more selected from the group consisting of: co, Mn and Al.

1+ a represents a molar ratio of lithium in the oxide represented by the above formula 1, wherein a may satisfy 0. ltoreq. a.ltoreq.0.3, preferably 0. ltoreq. a.ltoreq.0.2.

x represents a molar ratio of the doping element M in the oxide represented by the above formula 1, wherein x may satisfy 0. ltoreq. x.ltoreq.0.5, preferably 0. ltoreq. x.ltoreq.0.4, more preferably 0. ltoreq. x.ltoreq.0.2.

1 to x represent a molar ratio of nickel in the oxide represented by the above formula 1, wherein 1 to x may satisfy 0.5. ltoreq. 1 to x. ltoreq.1.0, preferably 0.6. ltoreq. 1 to x. ltoreq.1.0, more preferably 0.8. ltoreq. 1 to x. ltoreq.1.0.

When the nickel-excess used cathode material containing excess nickel is used as in the present invention, since expensive nickel is contained in a large amount, price competitiveness can be secured when the transition metal is recovered therefrom and recycled as a raw material. Further, as the demand for high-capacity batteries increases for third-generation electric vehicles and the like, the use of nickel-excess positive electrode materials is expected to increase rapidly, so that it is important to ensure a technique for disposing of nickel-excess waste positive electrode materials.

Next, the waste cathode material is heat-treated in an inert gas atmosphere or an oxygen atmosphere to phase-separate the waste cathode material into lithium oxide and metal oxide (step 2).

As in the present invention, when the waste cathode material is heat-treated at a temperature above the temperature range (700 to 800 ℃) where the layered structure is stable, the waste cathode material is phase-separated into a phase where both the lithium oxide phase and the metal oxide phase are stable at a high temperature, that is, a phase of lithium oxide and metal oxide, because the layered structure is unstable. For example, at 600 to 800 ℃, the cathode material is in the form of a stable phase when having a layered structure, and when heat treatment is performed at 800 ℃ or more, the cathode material is in the form of a stable phase when separated into lithium oxide and metal oxide. In addition, the higher the heat treatment temperature during phase separation, the higher the purity of the separation rate.

According to the present invention, the heat treatment of the waste cathode material may be performed in an inert gas atmosphere or an oxygen atmosphere, for example, in an inert gas atmosphere in which an inert gas such as nitrogen, argon, helium, or neon is used or in an oxygen atmosphere in which the oxygen concentration is 100 mol% or less.

For example, when the heat treatment is performed in an oxygen atmosphere, the heat treatment may be performed at 900 ℃ or more, preferably 900 to 1000 ℃. Therefore, when the heat treatment is performed in the above temperature range, a stable phase tends to be formed, so that the lithium transition metal oxide may be easily phase-separated. However, when the heat treatment temperature is lower than the above range, the layered structure remains, so that the separation efficiency may be reduced, and when it is higher than the above range, the process efficiency may be reduced.

In particular, the lower the partial pressure of oxygen (wherein the oxygen concentration is 100 mol% or less, preferably 50 mol% or less, more preferably 0 mol% to 10 mol%), the easier the phase separation of the lithium transition metal oxide. However, even in an oxygen atmosphere of 100 mol%, phase separation can occur within the above-described heat treatment temperature range.

For example, when the heat treatment is performed in an inert gas atmosphere, the heat treatment may be performed at 800 ℃ or higher, preferably 800 ℃ to 950 ℃.

When the heat treatment is performed in an inert gas atmosphere, a reducing atmosphere is maintained to reduce the temperature at which the phases of the lithium oxide and the metal oxide are separated, so that the lithium transition metal oxide can be easily phase-separated even when the heat treatment temperature is relatively low.

Further, according to the present invention, when the heat treatment is performed in an inert gas atmosphere, hydrogen gas may be further contained. Preferably, hydrogen may also be included in an amount of 10 vol% or less, preferably 2 vol% to 5 vol%, based on 100 vol% of the inactive gas.

When the heat treatment is performed in an inert gas atmosphere, and when hydrogen is also contained, the temperature at which the phases of the lithium oxide and the metal oxide are separated is further reduced due to the reducing ability of hydrogen, so that the effect that the lithium transition metal oxide is easily separated from the phases can be further achieved even when the heat treatment temperature is relatively low.

Next, the product obtained in step 2 is cooled to room temperature in an inert atmosphere (step 3).

When the heat-treated waste positive electrode material is cooled as in the present invention, the cooling is performed in an inert atmosphere, thereby preventing the waste positive electrode material from being transformed back to have a layered structure during temperature reduction. By the above, cooling to room temperature can be achieved while maintaining the separated phases in step 2. For example, if cooling is performed in an oxygen atmosphere, when the temperature of the waste cathode material passes through an interval of 600 ℃ to 800 ℃ during temperature reduction, the waste cathode material may be transformed back to have a layered structure due to recrystallization of the cathode material.

For example, the temperature decrease rate when cooling the waste cathode material may be 1 to 10 ℃/min. When the temperature decrease rate is lower than the above range, the phase separation rate may decrease and the process time may also increase as the time passing through the layered structure generation interval of 600 to 800 ℃, so that the process efficiency may decrease. On the other hand, when the temperature decrease rate is higher than the above range, the equipment is strained, so that the process cost may be increased due to the reduction of the equipment life or the like.

Finally, the mixed solution obtained by mixing the cooled product obtained in step 3 with distilled water is filtered to leach out the transition metal.

For example, the cooled product obtained in step 3 may be mixed with distilled water in a ratio of 1: 0.3 to 1: 2. preferably 1: 0.5 to 1: 1.2 to leach the lithium oxide and metal oxide phases separated in step 2 in distilled water.

For example, the leaching of the transition metal in distilled water may be performed at a temperature of 10 to 50 ℃ for 5 to 20 minutes. When the leaching time is shorter than the above range, the leaching of the transition metal in the distilled water is insufficient, and when the leaching time exceeds the above range, the leaching amount may increase, but the process is extended, so that the economic feasibility may be lowered. Further, when the leaching temperature satisfies the above range, the leaching efficiency may be further improved, but the present invention is not limited thereto.

Next, the distilled water is filtered to obtain each of the lithium oxide and the metal oxide leached in the distilled water.

The filtration may be performed by a method of passing the mixed solution through a filter having micro pores to filter floating materials and impurities in the mixed solution, and may be preferably performed by a method of filtering the leachate under reduced pressure using a filter or the like connected to a vacuum pump or a method of filtering the mixed solution using filter paper having micro pores.

The transition metals leached after step 4 may include, for example: a lithium compound including lithium hydroxide formed by a reaction between the lithium oxide separated in step 2 and distilled water; and nickel metal oxide containing nickel and M, specifically Ni_1-xM_xA metal oxide in the form of O (in this case, 0. ltoreq. x. ltoreq.0.5).

On the other hand, it is most preferable that metal oxide is used as Ni_1-xM_xLeaching the metal oxide in the form of O (wherein, x is more than or equal to 0 and less than or equal to 0.5). However, the metal oxide may be Li in which a part of nickel is replaced with lithium_x2Ni_1-x1-x2M_x1O (wherein 0 ≦ x1 ≦ 0.2, 0 ≦ x2 ≦ 0.3, and x ═ x1+ x 2). When the metal oxide in a form in which a part of nickel is substituted with lithium is leached, steps 1 to 4 of the present invention may be repeated to further improve the separation purity between the lithium oxide and the metal oxide.

For example, the separation purity of the metal oxide can be determined by the size of the unit cell measured by Inductively Coupled Plasma (ICP) or XRD. Steps 1 to 4 may be repeated 1 to 4 times to obtain the target isolation purity.

For example, the separation purity of the metal oxide can be determined by the Li concentration measured by ICP. Alternatively, when the unit cell size measured by XRD is 0.42nm to 0.4165nm, it can be determined that the purity is 80% or more. On the other hand, when the unit cell size measured by XRD is smaller than the above range, it means that the nickel site is substituted with lithium, so that it can be determined that the separation purity is less than 80%, which is low, and when the size exceeds the above range, it can be determined that phases other than the metal oxide may coexist.

Modes for carrying out the invention

Hereinafter, the present invention will be described in detail with reference to embodiments. However, the embodiment according to the present invention may be modified into other various forms, and the scope of the present invention should not be construed as being limited to the embodiment described below. The embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Examples

Example 1

Preparation of a liquid containing LiNi_0.9Co_0.05Mn_0.05O₂A waste positive electrode material as a positive electrode active material (step 1). Thermally treating the waste positive electrode material at 850 ℃ in a nitrogen atmosphere to separate the phase of the waste positive electrode material into Li₂O and Ni_0.9Co_0.05Mn_0.05And O (step 2).

Thereafter, the phase-separated waste cathode material was cooled to room temperature in a nitrogen atmosphere (step 3).

Next, the resulting cooled product was mixed with distilled water at a ratio of 1: 0.8 weight ratio was mixed to wash, and vacuum filtration was performed using a filter made of polyvinylidene fluoride having a pore size of 0.5 μm. Thereafter, the filtered solid and aqueous solution were vacuum-filtered to be separated into lithium oxide (LiOH) and metal oxide (Ni)_0.9Co_0.05Mn_0.05O) ofForm (step 4).

Example 2

Lithium oxide (LiOH) and metal oxide (Ni) were added to the mixture in the same manner as in example 1, except that the waste cathode material was heat-treated at 950 ℃ in an atmospheric atmosphere_0.9Co_0.05Mn_0.05O) from the spent positive electrode material.

Example 3

Lithium oxide (LiOH) and metal oxide (Ni) were added in the same manner as in example 1, except that steps 1 to 4 were repeated 4 times_0.9Co_0.05Mn_0.05O) from the spent positive electrode material.

Comparative example 1

Lithium oxide (LiOH) and metal oxide (Ni) were added to the reaction mixture in the same manner as in example 1, except that the phase-separated waste cathode material was cooled to room temperature in an oxygen atmosphere_0.9Co_0.05Mn_0.05O) from the spent positive electrode material.

Comparative example 2

Lithium oxide (LiOH) and metal oxide (Ni) were added in the same manner as in example 1, except that the heat treatment was performed at 750 ℃_0.9Co_0.05Mn_0.05O) from the spent positive electrode material.

Comparative example 3

Lithium oxide (LiOH) and metal oxide (Ni) were added in the same manner as in example 1, except that the heat treatment was performed at 850 ℃ in an oxygen atmosphere_0.9Co_0.05Mn_0.05O) from the spent positive electrode material.

Experimental example 1

In order to determine the phase separation performance of the waste cathode material of example 1, the temperature was increased from 700 ℃ to 830 ℃ during the heat treatment of the waste cathode material of example 1, and the change of the phase of the cathode material at this time was observed.

Specifically, the waste cathode material of example 1 was warmed up in a nitrogen (> 99%) atmosphere, and the in situ thermal XRD data at this time was determined using the Empyrean XRD equipment of panagical (Panalytical).

As shown in (a) and (b) of fig. 1, it can be confirmed that the waste cathode material prepared in example 1 has lithium transition metal oxide (LiMO) at 710 ℃₂R-3m, layered structure). However, when (a) and (c) of fig. 1 are examined, it can be confirmed that the waste cathode material prepared in example 1 has a phase of metal oxide (MO, Fm3m, rock salt structure) at 790 ℃ or more, specifically, about 820 ℃. As the results show, the lithium transition metal oxide decomposes and converts to a metal oxide/lithium oxide phase above 790 ℃.

Experimental example 2

The phase change of the waste positive electrode material after heat treatment and cooling to room temperature was observed in each of examples 1 and 2 and comparative example 1.

Specifically, the waste cathode materials were prepared in examples 1 and 2 and comparative example 1, respectively, and then cooled after phase separation, and in-situ thermal XRD data at this time was determined using an Empyrean XRD equipment of panacea and shown in (a) to (c) of fig. 2.

Fig. 2 is a graph showing in-situ thermal XRD data of the waste cathode materials prepared in (a) example 1, (b) example 2, and (c) comparative example 1, respectively, and then cooled after phase separation.

Looking at (a) and (b) of fig. 2, it can be confirmed that (c) of fig. 1, i.e., a metal oxide (MO, Fm3m, rock salt structure) phase is maintained even though the waste cathode material is heated and then cooled by the respective methods in examples 1 and 2.

On the other hand, referring to (c) of fig. 2, when the waste cathode material is heated and then cooled by the method of comparative example 1, (b) of fig. 1, i.e., a lithium transition metal oxide (LiMO), is again generated₂R-3m, layered structure).

Experimental example 3

In order to determine the separation purity of the transition metal separated in each of examples 1 to 3 and comparative examples 2 to 3, the unit cell size at this time was determined using an Empyrean XRD equipment of pannaceae, and the size was shown in table 1 below.

[ Table 1]

	Unit cell size (nm)
		Example 1	0.4187
Example 2	0.4185
		Example 3	0.4195
Comparative example 2	0.4134
		Comparative example 3	0.4125

The transition metals each isolated in examples 1 to 3 had a unit cell size measured by XRD in the range of 0.42nm to 0.4165nm, so that it could be confirmed that the purity thereof was 80% or more. On the other hand, the transition metals each separated in comparative examples 2 and 3 had a unit cell size measured by XRD in a range less than the range of the present invention, so that it can be confirmed that the purity thereof was lower than that of the transition metals each separated in examples 1 to 3.