CN109065996B

CN109065996B - Method for regenerating waste nickel cobalt lithium manganate ternary cathode material

Info

Publication number: CN109065996B
Application number: CN201810872569.5A
Authority: CN
Inventors: 周涛; 庄璐琪; 孙琮皓
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2018-08-02
Filing date: 2018-08-02
Publication date: 2020-02-04
Anticipated expiration: 2038-08-02
Also published as: CN109065996A

Abstract

The invention discloses a method for regenerating a waste nickel cobalt lithium manganate ternary cathode material. The method comprises the steps of leaching waste nickel cobalt lithium manganate ternary positive electrode materials by using a phosphoric acid-citric acid mixed acid solution to obtain a leaching solution; adjusting the proportion of metal ions in the leachate by nickel salt, cobalt salt and manganese salt, adding the leachate into an oxalic acid solution for coprecipitation reaction, pre-calcining the obtained precipitate to obtain nickel-cobalt-manganese oxide, grinding and mixing the nickel-cobalt-manganese oxide with a lithium source, and calcining to obtain a regenerated nickel-cobalt-lithium manganate ternary positive electrode material; the method adopts a mixed acid leaching process, has the advantages of low acid consumption, short leaching time, low cost, small influence on the environment, no need of adding a reducing agent and simple process; and the mixed acid leachate is directly used for synthesizing the ternary cathode material, so that the complex process of separating and purifying various metals in the leachate in the prior art is avoided, and the closed-loop recycling of the metals is realized.

Description

Method for regenerating waste nickel cobalt lithium manganate ternary cathode material

Technical Field

The invention relates to a method for recycling a nickel cobalt lithium manganate ternary positive electrode material of a waste lithium ion battery, in particular to a method for recycling nickel cobalt lithium manganate ternary positive electrode waste of the waste lithium ion battery through mixed acid leaching, cocrystallization precipitation and high-temperature solid-phase reaction, and belongs to the technical field of secondary resource recycling and circular economy.

Background

With the development and popularization of portable electronic devices and electric vehicles, the use of lithium ion batteries has increased dramatically, while a large amount of lithium ion battery solid waste is generated. Research shows that by 2020, China discarded lithium ion batteries reach 250 hundred million, and the quality of the lithium ion batteries reaches 50 million tons. Due to the high content of heavy metal and toxic electrolyte in the lithium ion battery, the improper treatment of the waste lithium ion battery can bring serious environmental pollution and threaten the human health. Meanwhile, the spent lithium ion battery contains a large amount of valuable metals including Li, Ni, Co, Al, and Cu. Therefore, the recovery of valuable metals from waste lithium ion batteries, especially valuable metals with limited sources, is a very interesting problem from the viewpoint of economy and environmental protection.

At present, the recovery method of lithium ion batteryMainly comprises a pyrometallurgical method, a hydrometallurgical method and a biological metallurgical method. The hydrometallurgical process is widely used due to its advantages of high metal recovery, high purity, low energy consumption, etc. Generally, the recovery process mainly includes pretreatment, leaching of the positive active material, and extraction of metals from the leachate. Therefore, how to recover metals with high efficiency and environmental protection becomes the key of recovery. For the metal leaching process, the single-acid leaching system is widely applied, and the mixed-acid leaching system lacks systematic and theoretical research. The traditional single-acid leaching method takes inorganic acid or organic acid as a leaching agent, and the process has the defects of high acid consumption and long leaching time. In addition, because nickel, cobalt and manganese in the nickel cobalt lithium manganate ternary positive electrode material are in high valence state and are not easy to leach out in an acid solution, the leaching process needs to add a corresponding reducing agent to reduce high valence state metal into low valence state metal to promote leaching of nickel, cobalt and manganese, and the commonly used reducing agent is H₂O₂. In the metal separation and recovery process, metals in the leachate are usually separated and recovered by a precipitation method, a solvent extraction method and a crystallization method after the anode waste is leached, the closed-loop circulation of metal components in the anode waste is not realized, and the defects of serious secondary pollution, impure products, complex recovery process, high recovery cost and the like exist.

Disclosure of Invention

In the prior art, the traditional leaching and the traditional metal separation recovery process are combined in the process of recovering the lithium ion battery anode material, the traditional leaching process adopts single acid leaching, the secondary pollution is serious when single inorganic acid leaching is adopted, the price is high when single organic acid leaching is adopted, and the two leaching modes have the defects of high acid consumption, long leaching time, additional addition of a reducing agent and the like; the traditional metal separation process has the defects of complex recovery process, low efficiency, impure products and secondary pollution, and is difficult to comprehensively recover valuable metals. The invention aims to provide a method for leaching waste nickel cobalt lithium manganate ternary positive electrode materials by mixed acid and synthesizing the nickel cobalt lithium manganate ternary positive electrode materials by directly utilizing leaching liquid. Because the citric acid in the mixed acid leaching agent has reducibility, high-valence nickel, cobalt and manganese in the nickel cobalt lithium manganate can be reduced into low-valence nickel, cobalt and manganese, and the leaching efficiency of various metals in an acid solution is promoted, so that a reducing agent is not required to be additionally added in the whole leaching process; meanwhile, the mixed acid leaching solution is directly used for synthesizing the ternary cathode material without metal separation, so that closed cycle of nickel, cobalt, manganese and the like in the ternary cathode material is realized, the operation is simple, the treatment cost is low, and the method is favorable for industrial production.

The invention provides a method for regenerating a waste nickel cobalt lithium manganate ternary cathode material, which comprises the following steps:

1) leaching the waste nickel cobalt lithium manganate ternary positive electrode material by using a phosphoric acid-citric acid mixed acid solution to obtain a leaching solution;

2) adjusting the molar ratio of nickel ions, cobalt ions and manganese ions in the leachate to meet the requirement of the molar ratio of elements of nickel, cobalt and manganese in the nickel cobalt lithium manganate ternary cathode material through nickel salt, cobalt salt and manganese salt, and then adding the leachate into an oxalic acid solution for coprecipitation reaction to obtain nickel cobalt manganese oxalate;

3) pre-calcining the nickel, cobalt and manganese oxalate to obtain a nickel, cobalt and manganese oxide; and grinding and mixing the nickel-cobalt-manganese oxide and a lithium source, and calcining to obtain the regenerated nickel-cobalt-manganese lithium ternary cathode material.

The invention adopts the phosphoric acid-citric acid mixed acid solution to lead Li in the waste nickel cobalt lithium manganate⁺、Ni²⁺、Co²⁺、Mn²⁺When metals are leached efficiently, the phosphoric acid and the citric acid have obvious synergistic leaching effect, the leaching effect is obviously superior to the effect result of single acid, the acid consumption can be obviously reduced, the leaching time is greatly shortened, the cost is saved, and the influence of the whole system on the environment is small. In addition, the citric acid in the mixed acid leaching agent has reducibility, so that high-valence nickel, cobalt and manganese in the nickel-cobalt lithium manganate can be reduced to low-valence state, and the leaching efficiency of the nickel-cobalt lithium manganate in an acid solution is promoted, so that no additional reducing agent is required to be added in the whole leaching process. On the basis of which oxalic acid is used asA metal ion precipitant capable of precipitating Ni under appropriate conditions²⁺、Co²⁺、Mn²⁺And (3) selectively precipitating to generate a high-purity oxalic acid eutectic of manganese, cobalt and nickel, and preparing the nickel cobalt lithium manganate ternary cathode material by directly carrying out high-temperature solid-phase reaction on the eutectic. The method does not need to carry out metal separation on the leaching solution, is directly used for synthesizing the ternary cathode material, realizes the closed cycle of metals such as nickel, cobalt, manganese and the like in the ternary cathode material, can be used for recovering lithium from the leaching waste liquid, is simple to operate, has low treatment cost, and is beneficial to industrial production.

In a preferred embodiment, the leaching conditions are as follows: the total acid concentration of the phosphoric acid-citric acid mixed acid solution is 0.3-0.7M, the phosphoric acid concentration is less than or equal to 0.6M, the leaching solid-liquid ratio is 15-40 g/L, the leaching temperature is 50-95 ℃, and the leaching time is 5-60 min. The total concentration of acid in the phosphoric acid-citric acid mixed acid solution is preferably 0.6-0.7M. The concentration of phosphoric acid is preferably 0.2-0.3M. The leaching solid-liquid ratio is preferably 15-20 g/L. The leaching temperature is preferably 85-90 ℃. The leaching time is preferably 30-60 min. The most preferred leaching conditions are: the total acid concentration in the phosphoric acid-citric acid mixed acid solution is 0.6M, the phosphoric acid concentration is 0.2M, the leaching solid-liquid ratio is 20g/L, the leaching temperature is 90 ℃, and the leaching time is 30 min. Under the most preferred leaching conditions, Li⁺、Ni²⁺、Co²⁺、Mn²⁺The leaching rate of the metals reaches more than 90 percent.

The phosphoric acid-citric acid mixed acid solution of the invention has obvious synergistic effect between phosphoric acid and citric acid: on one hand, citric acid as a reducing agent can reduce part of metals existing in a high valence state into a low valence state, and the low valence state metals are beneficial to leaching phosphoric acid; on the other hand, the citric acid can chelate leached metal ions to further promote the leaching reaction; in the third aspect, citric acid is used as organic weak acid, which can slowly release hydrogen ions through ionization, play a role in buffering, compensate hydrogen ions consumed by inorganic phosphoric acid decomposition reaction, and enable phosphoric acid to keep higher leaching capacity in the leaching process, so that the phosphoric acid-citric acid synergistic effect is obvious, and the leaching efficiency of metal can be improved compared with single inorganic acid or organic acid.

In a preferable scheme, the molar ratio of nickel ions, cobalt ions and manganese ions in the leachate is adjusted to 5:2:3 by nickel salt, cobalt salt and manganese salt, and the total concentration of the nickel ions, the cobalt ions and the manganese ions in the leachate is within the range of 0.3-0.7M. The nickel salt is water-soluble nickel salt, preferably acetate. The cobalt salt is water-soluble cobalt salt, preferably cobalt acetate. The manganese salt is water-soluble manganese salt, preferably manganese acetate.

In a preferred embodiment, the conditions of the coprecipitation reaction are as follows: dropwise adding the leachate into an oxalic acid solution with the concentration of 0.3-0.7M at the stirring speed of 500-850 rpm, adjusting the pH of the system to 1-4, and reacting at the temperature of 25-60 ℃ for 4-6 h; the ratio of the molar quantity of oxalic acid in the oxalic acid solution to the total molar quantity of nickel ions, cobalt ions and manganese ions in the leaching solution is 1.0-1.5: 1. The concentration of the preferred oxalic acid solution is 0.3-0.5M. The preferable pH value of the system is 1.5-2.5. The preferable reaction temperature is 50-60 ℃. The preferable reaction time is 4-6 h. The ratio of the molar quantity of oxalic acid in the oxalic acid solution to the total molar quantity of nickel ions, cobalt ions and manganese ions in the leaching solution is preferably 1.2-1.5: 1. Most preferably, the conditions of the coprecipitation reaction are: dropwise adding the leachate into an oxalic acid solution with the concentration of 0.4M at the stirring speed of 600rpm, adjusting the pH of the system to be 2, and reacting for 5 hours at the temperature of 50 ℃; the ratio of the molar quantity of oxalic acid in the oxalic acid solution to the total molar quantity of nickel ions, cobalt ions and manganese ions in the leaching solution is 1.2: 1. Under the most preferable conditions, the high-efficiency selective precipitation of nickel ions, cobalt ions and manganese ions can be realized.

In a preferred embodiment, the pre-calcination conditions are: pre-calcining for 4-6 h at the temperature of 450-550 ℃. The pre-calcination process mainly decomposes oxalate prepolymer to obtain high-purity eutectic of manganese, cobalt and nickel oxides. Most preferred precalcination conditions are: the pre-calcining temperature is 500 ℃, and the pre-calcining time is 5 hours.

Preferably, the nickel-cobalt-manganese oxide is mixed with a lithium source in a molar ratio of Li/M of 1 to 1.1, wherein M is Ni + Co + Mn. The most preferred molar ratio is Li/M ═ 1.05.

In a preferred embodiment, the calcination conditions are as follows: calcining for 6-18 h at the temperature of 750-950 ℃. Most preferred calcination conditions are: the calcination temperature is 800 ℃, and the pre-calcination time is 12 h.

The method for regenerating the waste nickel cobalt lithium manganate ternary cathode material comprises the following specific steps:

1) waste lithium ion battery ternary positive electrode material LiNi_0.5Co_0.2Mn_0.3O₂Mixed with mixed acid solution of phosphoric acid and citric acid to react to obtain the product containing Li⁺、Ni²⁺、Co²⁺、Mn²⁺The leaching solution of (a); the total concentration of the mixed acid is 0.3-0.7M, the concentration of phosphoric acid in the mixed acid is less than or equal to 0.6M, the leaching solid-liquid ratio is 15-40 g/L, the leaching temperature is 50-95 ℃, and the leaching time is 5-60 min;

2) adding nickel acetate, cobalt acetate and manganese acetate to adjust the mass ratio of nickel ions, cobalt ions and manganese ions in the leachate to be 5:2:3, adjusting the concentration of total metal ions to be 0.4M, taking oxalic acid as a precipitator and ammonia water as a pH regulator, reacting for 5 hours at a proper temperature, aging for one night, filtering precipitates, washing and drying to obtain a nickel-cobalt-manganese oxalate precursor; the concentration of oxalic acid used as a precipitator is 0.4M, and under the stirring speed of 600rpm, the nickel-cobalt-manganese mixed solution is dropwise added into the oxalic acid solution in a forward feeding mode, wherein the feeding speed is 9 mL/min; in the reaction process, adding concentrated ammonia water, adjusting the pH value of the system to be 1-4, and controlling the reaction temperature to be 25-60 ℃; the ratio r of oxalic acid to the total metal ion content of the leachate is 1.0-1.5: 1.

3) The precursor is pre-calcined for 5 hours at 500 ℃, ground into powder, the powder is mixed with lithium carbonate powder according to the molar ratio of Li/M (1-1.1) (M (Ni + Co + Mn)), the mixture is manually ground for 1 hour in an ethanol medium, the mixture is dried and then pressed into a wafer under the pressure of 6MPa, the wafer is calcined for 6-18 hours at 750-950 ℃, and the wafer is ground, so that the ternary cathode material of the lithium ion battery is obtained.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1) in the synthesis process of the waste nickel cobalt lithium manganate ternary positive electrode material, phosphoric acid and citric acid are used as the synergistic leaching agents of metals in the nickel cobalt lithium manganate ternary positive electrode material, compared with the traditional single-acid leaching, the acid consumption can be obviously reduced, the leaching time is greatly shortened, the cost is saved, and no additional reducing agent is required to be added in the whole process; and the phosphoric acid and the citric acid have wide source range, low price and small influence on the environment.

2) The leachate in the synthesis process of the waste nickel cobalt lithium manganate ternary cathode material is not required to be separated and is directly used for synthesizing the ternary cathode material, so that the complex process of separating and purifying various metals in the leachate in the prior art is avoided, and the closed-loop recycling of the metals is realized.

Drawings

FIG. 1 shows the leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained from different total concentrations of mixed acid in comparative example 1.

FIG. 2 shows the leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained from the mixed acid of comparative example 2 at different concentrations of phosphoric acid.

FIG. 3 shows the leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained at different reaction temperatures in comparative example 3.

FIG. 4 shows the leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained in comparative example 4 at different solid-to-liquid ratios.

FIG. 5 shows the leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained in comparative example 5 at different reaction times.

FIG. 6 shows LiNi, an obtained product, prepared under the optimum calcination conditions of 800 ℃ for 12 hours and a lithium metal ratio of 1.05 in example 1_0.5Co_0.2Mn_0.3O₂XRD pattern of (a).

FIG. 7 shows LiNi, an obtained product, prepared under the optimum calcination conditions of 800 ℃ for 12 hours and a lithium metal ratio of 1.05 in example 1_0.5Co_0.2Mn_0.3O₂SEM image of (d).

Detailed Description

The following examples are intended to further illustrate the present disclosure and are not intended to limit the scope of the claims herein.

Characterization and analysis means:

and detecting and analyzing the content of the metal ions in the filtrate by using an inductively coupled plasma emission spectrometer (ICP-OES).

The precipitated product was characterized and analyzed by XRD ray powder diffractometer and Scanning Electron Microscope (SEM).

Comparative example 1

The total concentration of the mixed acid is respectively 0.3, 0.4, 0.5, 0.6 and 0.7M, wherein the mixed acid solution of phosphoric acid and citric acid with equal concentration is respectively subjected to mixed acid leaching reaction according to the following operations. 100ml of mixed acid solution is added into a 250ml flask and is adjusted to the rotation speed of 500 r/min. After the solution was heated to 90 ℃ 2g LiNi was added_0.5Co_0.2Mn_0.3O₂Stirring and reacting the ternary anode waste for 40min, and performing suction filtration to obtain the Li-containing cathode material⁺、Ni²⁺、Co²⁺、Mn²⁺The solution of (1).

The leaching rates of lithium, nickel, cobalt and manganese ions in the leachate obtained under the conditions of the comparative example and with different total mixed acid concentrations are shown in table 1 and figure 1.

TABLE 1 leaching rates of lithium, nickel, cobalt, manganese ions in the leachate obtained with different total concentrations of mixed acid

As can be seen from table 1 and fig. 1, under the conditions of the present comparative example, when the total concentration of the mixed acid was increased from 0.3M to 0.6M, the leaching efficiencies of Li, Co, Ni and Mn were increased from 66.73% to 100%, 60.91% to 92.32%, 59.82% to 94.77%, and 57.03% to 94.26%, respectively. Further increasing the total acid concentration of the mixed acid to 0.7mol/L, the leaching efficiency of each element is basically not changed, so 0.6M is selected as the optimal reaction acid concentration.

Comparative example 2

Mixed acid solution with total concentration of mixed acid of 0.6M and phosphoric acid concentration of 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6M in the mixed acid is prepared, and mixed acid leaching reaction is respectively carried out according to the following operations. 100ml of mixed acid solution is added into a 250ml flask and is adjusted to the rotation speed of 500 r/min. After the solution was heated to 90 ℃ 2g LiNi was added_0.5Co_0.2Mn_0.3O₂Stirring and reacting the ternary anode waste for 40minSuction filtering to obtain Li-containing⁺、Ni²⁺、Co²⁺、Mn²⁺The solution of (1).

The leaching rates of lithium, nickel, cobalt and manganese ions in the leachate obtained from the mixed acid with different phosphoric acid concentrations under the conditions of the comparative example are shown in table 2 and fig. 2.

TABLE 2 leaching rates of lithium, nickel, cobalt, manganese ions in the leachate obtained with different phosphoric acid concentrations in mixed acids

As can be seen from table 2 and fig. 2, under the conditions of the present comparative example, the leaching efficiencies of Co, Ni, Mn, and Li were 50.71%, 49.64%, 45.56%, and 54.87%, respectively, when the phosphoric acid concentration was 0M and the citric acid was 0.6M. When the concentration of phosphoric acid is 0.6M and the concentration of citric acid is 0M, the leaching efficiencies of Co, Ni, Mn and Li are respectively 38.66%, 40.09%, 1.36% and 73.91%. Therefore, the leaching efficiency is lower in a single acid system. The leaching efficiency was highest when the phosphoric acid concentration was 0.2M and 0.3M, and the leaching efficiencies of Co, Ni, Mn and Li were 91.42% and 92.32%, 94.03% and 94.77%, 92.28% and 94.26%, 100% and 100%, respectively. Considering that the phosphoric acid concentration is too high, phosphate pollution is easily caused. Therefore, the optimal reaction conditions are selected to be 0.2M phosphoric acid concentration and 0.4M citric acid concentration.

Comparative example 3

Preparing mixed acid solution with total concentration of 0.6M, wherein the concentration of phosphoric acid is 0.2M, and the concentration of citric acid is 0.4M. The reaction temperatures were controlled at 50, 60, 70, 80, 90 and 95 ℃ to carry out the following leaching reactions, respectively. 100ml of mixed acid solution is added into a 250ml flask and is adjusted to the rotation speed of 500 r/min. After the solution was heated to a set temperature, 2g of LiNi was added_0.5Co_0.2Mn_0.3O₂Stirring and reacting the ternary anode waste for 40min, and performing suction filtration to obtain the Li-containing cathode material⁺、Ni²⁺、Co²⁺、Mn²⁺The solution of (1).

The leaching rates of lithium, nickel, cobalt and manganese ions in the leachate obtained under the conditions of the comparative example and at different reaction temperatures are shown in table 3 and fig. 3.

TABLE 3 leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained at different reaction temperatures

As can be seen from table 3 and fig. 3, under the conditions of this comparative example, the leaching efficiency of the active material increased as the reaction temperature increased before the reaction temperature reached 90 ℃. Further increases the reaction temperature and slightly reduces the leaching efficiency. The reason for the analysis may be that the acid was partially decomposed at high temperature. Therefore, the reaction temperature of the reduction leaching is suitably controlled to 90 ℃.

Comparative example 4

Preparing mixed acid solution with total concentration of 0.6M, wherein the concentration of phosphoric acid is 0.2M, and the concentration of citric acid is 0.4M. The following leaching reactions were carried out while controlling the reaction solid-to-liquid ratios at 15, 20, 25, 30 and 40g/L, respectively. 100ml of mixed acid solution is added into a 250ml flask and is adjusted to the rotation speed of 500 r/min. After the solution is heated to 90 ℃, adding a corresponding amount of LiNi_0.5Co_0.2Mn_0.3O₂Stirring and reacting the ternary anode waste for 40min, and performing suction filtration to obtain the Li-containing cathode material⁺、Ni²⁺、Co²⁺、Mn²⁺The solution (a) of (b) is,

the leaching rates of lithium, nickel, cobalt and manganese ions in the leachate obtained under different conditions of the comparative example and solid-liquid ratios are shown in table 4 and fig. 4.

TABLE 4 leaching rates of Li, Ni, Co and Mn ions in the leachate obtained at different solid-to-liquid ratios

As can be seen from table 4 and fig. 4, in the conditions of this comparative example, lithium, cobalt, nickel and manganese can achieve very high reduction leaching efficiency when the solid-liquid ratio is small. When the solid-to-liquid ratio exceeds 20g/L, the leaching rate sharply decreases as the solid-to-liquid ratio increases. On the premise of ensuring the leaching efficiency, the consumption of chemicals is reduced, and the solid-liquid ratio of 20g/L is selected as the optimal reaction condition.

Comparative example 5

Preparing mixed acid solution with total concentration of 0.6M, wherein the concentration of phosphoric acid is 0.2M, and the concentration of citric acid is 0.4M. The reaction times were controlled at 5, 10, 20, 30, 40 and 60min, and the following leaching reactions were performed, respectively. 100ml of mixed acid solution is added into a 250ml flask and is adjusted to the rotation speed of 500 r/min. After the solution was heated to 90 ℃ 2g LiNi was added_0.5Co_0.2Mn_0.3O₂Stirring the ternary anode waste for reaction time, and performing suction filtration to obtain the material containing Li⁺、Ni²⁺、Co²⁺、Mn²⁺The solution of (1).

The leaching rates of lithium, nickel, cobalt and manganese ions in the leachate obtained under different reaction times under the conditions of the comparative example are shown in table 5 and fig. 5.

TABLE 5 leaching rates of lithium, nickel, cobalt, and manganese ions in the leachate obtained at different reaction times

As can be seen from table 5 and fig. 5, under the conditions of this comparative example, the reaction time had a very significant effect on the leaching rates of cobalt, nickel, manganese and lithium, and when the leaching time was 5min, the leaching rates of cobalt, nickel, manganese and lithium were 45.70%, 45.63%, 42.72% and 57.79%, respectively. The leaching rate was gradually increased as the reaction time increased, and when the reaction time was 30min, more than 91.63% of Co, 93.38% of Ni, 92.00% of Mn, and 100% of Li were leached. However, the leaching rates of lithium, cobalt, nickel and manganese basically do not change after the time is increased. Therefore, 30min was selected as the optimal reduction leaching time.

According to the experimental results of the comparative examples 1-5, the optimal leaching process conditions are that the total concentration of the mixed acid is 0.6M, the concentration of phosphoric acid in the mixed acid is 0.2M, the leaching temperature is 90 ℃, the reaction time is 30min and the solid-liquid ratio is 20 g/L. By ICP-OES detection, Li under the optimal leaching condition is obtained⁺、Ni²⁺、Co²⁺、Mn²⁺The leaching rates of (A) were 100%, 93.38%, 91.63% and 92.00%, respectively. And storing the filtrate for the subsequent regeneration of the ternary cathode material.

Example 1

(1) Preparing mixed acid solution with total concentration of 0.6M, wherein the concentration of phosphoric acid is 0.2M, and the concentration of citric acid is 0.4M. 100ml of the solution is taken and added into a 250ml flask, and the rotation speed is adjusted to 500 r/min. When the solution was heated to 90 ℃, 2g of LiNi was added_0.5Co_0.2Mn_0.3O₂Stirring and reacting the ternary anode waste for 30min, and performing suction filtration to obtain the Li-containing cathode waste⁺、Ni²⁺、Co²⁺、Mn²⁺The solution of (1).

(2) Taking 50ml of the solution obtained in the step (1), adding (CH)₃COO)₂Ni·4H₂O,(CH₃COO)₂Co·4H₂O and (CH)₃COO)₂Mn·4H₂O, adjusting Ni²⁺，Co²⁺And Mn²⁺The molar ratio of ions is 5:2:3, and the total metal ion concentration of the solution is 0.4M. Dropwise adding a proper amount of H into the nickel-cobalt-manganese mixed solution by adopting a forward feeding mode at a stirring speed of 600rpm₂C₂O₄To the solution, the dropping rate was 9 mL/min. During the reaction, by adding NH₃·H₂O, adjusting the pH value of the system, reacting for 5 hours at a proper temperature, aging for one night, filtering precipitates, washing and drying to obtain Ni_0.5Co_0.2Mn_0.3C₂O₄·2H₂And O. Corresponding single-factor experiments are designed to explore the optimal precipitation conditions, and the pH (1, 2, 3 and 4), the reaction temperature (25, 40, 50 and 60 ℃) and the ratio r (1.0, 1.2 and 1.5) of the oxalic acid to the total metal ion substance content of the leachate are controlled. Neither too high nor too low pH leads to complete precipitation of metal ions. Excessive pH value and excessive added ammonia water can ensure that part of metal ions preferentially form a complex with the ammonia water and are difficult to precipitate by oxalic acid, especially Ni²⁺. When the temperature is lower than 50 ℃, metal ions cannot be completely precipitated, and the obtained precipitate has poor crystallization property and uneven particles. When r is 1.0, the amount of oxalic acid added is not sufficient to completely precipitate metal ions. When r is 1.2 or 1.5, i.e. when oxalic acid is excessiveAnd the metal ions can be completely precipitated. The optimum precipitation conditions, pH 2, reaction temperature 50 deg.C, and ratio of oxalic acid to total metal ion content of the leachate, r 1.2 (60 ml 0.4M H) were determined by ICP-OES detection₂C₂O₄A solution). Under optimum precipitation conditions, 3.61g of Ni were obtained_0.5Co_0.2Mn_0.3C₂O₄·2H₂O。

(3) The Ni obtained in (2)_0.5Co_0.2Mn_0.3C₂O₄·2H₂O was pre-calcined at 500 ℃ for 5h to give 1.50g (Ni)_0.5Co_0.2Mn_0.3)₃O₄. And then mixing with a certain amount of Li₂CO₃Mixing the powders, adding an ethanol medium into an agate mortar, manually grinding for 1h, drying, pressing into a wafer by using a corresponding die and a corresponding tablet machine under the pressure of 6MPa, calcining for a period of time in a tubular furnace at a proper temperature, and grinding to obtain regenerated LiNi_0.5Co_0.2Mn_0.3O₂. Corresponding single-factor experiments were designed to explore the optimal calcination conditions, calcination temperature (750, 800, 850, 900 and 950 ℃), calcination time (6h, 12h and 18h), lithium metal ratio (1.00, 1.05 and 1.10). The calcination temperature is too low or the calcination time is too short, the particles do not completely grow up, the shapes are irregular, the crystallinity is low, and the cation mixed arrangement is serious. If the calcination temperature is too high or the calcination time is too long, the particles become abnormally large, so that the migration path of lithium ions in the charge-discharge process becomes long, and the diffusion speed in crystals becomes slow. And lithium volatilization is serious, cation mixing is aggravated, and the electrochemical performance of the material is reduced. The ratio of lithium metal is too low, and because lithium is volatilized at high temperature, the content of lithium in the calcined material is low, so that cation mixing is serious. Too high of a lithium metal ratio, too much lithium enters the material structure, causing the material to deviate from the layered structure.

The regenerated LiNi obtained under the above conditions_0.5Co_0.2Mn_0.3O₂The components of the compounds are identified and contrasted by XRD, and the obtained XRD pattern shows that the electrode material is classified into R^-3mα -NaFeO of type space group₂Layer-shaped Structure according to the two pairs of (006)/(102) and (108)/(110)The splitting of the diffraction peak shows that the material has a well-ordered layered structure. I is₀₀₃/I₁₀₄The (R) diffraction peak intensity ratio can be used to characterize the degree of cation mixing. In general, when R is>At 1.2, the degree of cation mixing was low. For a hexagonal cell, the ratio of lattice parameters a and c can characterize the integrity of the hexagonal structure. In general, when c/a>4.899, the hexagonal structure is considered to be very regular. According to the judgment basis, the optimal calcination condition that the lithium metal ratio is 1.05 at 800 ℃ for 12h is preliminarily judged, the two pairs of diffraction peaks of (006)/(102) and (108)/(110) are obviously split, and R is obviously₁＝1.23，c/a＝4.9460。

In the synthesis process of the regenerated ternary cathode material, oxalate prepolymer Ni is generated under the optimal operation condition_0.5Co_0.2Mn_0.3C₂O₄·2H₂O, oxide intermediate (Ni)_0.5Co_0.2Mn_0.3)₃O₄And the product LiNi_0.5Co_0.2Mn_0.3O₂The theoretical and actual values of the metal composition (measured by ICP-OES) are shown in Table 6.

TABLE 6 theoretical and actual values for the oxalate prepolymers, oxide intermediates and product Metal compositions

The above-mentioned embodiments are only preferred embodiments of the present invention, and all equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A method for regenerating a waste nickel cobalt lithium manganate ternary cathode material is characterized by comprising the following steps: the method comprises the following steps:

1) leaching the waste nickel cobalt lithium manganate ternary positive electrode material by using a phosphoric acid-citric acid mixed acid solution to obtain a leaching solution; the leaching conditions are as follows: the total acid concentration in the phosphoric acid-citric acid mixed acid solution is 0.3-0.7M, the phosphoric acid concentration is less than or equal to 0.6M, the leaching solid-liquid ratio is 15-40 g/L, the leaching temperature is 50-95 ℃, and the leaching time is 5-60 min;

2) adjusting the molar ratio of nickel ions, cobalt ions and manganese ions in the leachate to meet the requirement of the molar ratio of elements of nickel, cobalt and manganese in the nickel cobalt lithium manganate ternary cathode material through nickel salt, cobalt salt and manganese salt, and then adding the leachate into an oxalic acid solution for coprecipitation reaction to obtain nickel cobalt manganese oxalate; the coprecipitation reaction conditions are as follows: dropwise adding the leachate into an oxalic acid solution with the concentration of 0.3-0.7M at the stirring speed of 500-850 rpm, adjusting the pH of the system to 1-4, and reacting at the temperature of 25-60 ℃ for 4-6 h; the ratio of the molar quantity of oxalic acid in the oxalic acid solution to the total molar quantity of nickel ions, cobalt ions and manganese ions in the leaching solution is 1.0-1.5: 1;

3) pre-calcining the nickel, cobalt and manganese oxalate to obtain a nickel, cobalt and manganese oxide; grinding and mixing the nickel-cobalt-manganese oxide and a lithium source, and calcining to obtain a regenerated nickel-cobalt-manganese acid lithium ternary positive electrode material; the pre-calcining conditions are as follows: pre-calcining for 4-6 h at the temperature of 450-550 ℃; the calcining conditions are as follows: calcining for 6-18 h at the temperature of 750-950 ℃.

2. The method for regenerating the waste nickel cobalt lithium manganate ternary positive electrode material according to claim 1, characterized in that: the leaching conditions are as follows: the total acid concentration of the phosphoric acid-citric acid mixed acid solution is 0.6-0.7M, the phosphoric acid concentration is 0.2-0.3M, the leaching solid-liquid ratio is 15-20 g/L, the leaching temperature is 85-90 ℃, and the leaching time is 30-60 min.

3. The method for regenerating the waste nickel cobalt lithium manganate ternary positive electrode material according to any one of claims 1 to 2, characterized in that: the molar ratio of nickel ions, cobalt ions and manganese ions in the leachate is adjusted to meet 5:2:3 through nickel salt, cobalt salt and manganese salt, and the total concentration of the nickel ions, the cobalt ions and the manganese ions in the leachate is within the range of 0.3-0.7M.

4. The method for regenerating the waste nickel cobalt lithium manganate ternary positive electrode material according to claim 3, characterized in that: the nickel salt is acetate; the cobalt salt is cobalt acetate; the manganese salt is manganese acetate.

5. The method for regenerating the waste nickel cobalt lithium manganate ternary positive electrode material according to claim 4, characterized in that: the coprecipitation conditions are as follows: dropwise adding the leachate into an oxalic acid solution with the concentration of 0.3-0.5M at the stirring speed of 500-850 rpm, adjusting the pH of the system to be 1.5-2.5, and reacting for 4-6 h at the temperature of 50-60 ℃; the ratio of the molar quantity of oxalic acid in the oxalic acid solution to the total molar quantity of nickel ions, cobalt ions and manganese ions in the leaching solution is 1.2-1.5: 1.

6. The method for regenerating the waste nickel cobalt lithium manganate ternary positive electrode material according to claim 1, characterized in that: the nickel-cobalt-manganese oxide is mixed with a lithium source according to a molar ratio Li/M of 1-1.1, wherein M is Ni + Co + Mn.