Lithium metal recovery method and residue recovery method

Abstract

The invention provides a lithium metal recovery method and a residue recovery method, and the method comprises a crude lithium carbonate purification process: preparing crude lithium carbonate, slurrying the crude lithium carbonate, and carrying out deep carbonization to obtain a carbonized material; performing impurity removal and thermal decomposition on the carbonized material; and carrying out solid-liquid separation and other treatments on the material after thermal decomposition to obtain purified lithium carbonate. According to an existing waste battery powder recycling technology, concentrated sulfuric acid dissolution is mainly adopted, then extraction and other processes are adopted for separating and removing impurities of elements such as lithium, nickel, cobalt and manganese, and metal such as lithium carbonate, nickel, cobalt and manganese is recycled. However, the process flow is long, a large amount of acid and alkali are needed, a large amount of wastewater is generated, energy consumption is high, and the risk of environmental pollution is high. The method has the advantages of simple process, no need of adding any auxiliary reagent in the impurity removal process, no wastewater discharge, reduction of the recovery cost by 40%, economy, energy saving and environmental protection.

Description

Technical Field

[0001] The invention relates to a metal recovery method, in particular to a lithium metal recovery method and a residue recovery method generated by the method. Background Art

[0002] As the popularity of new energy vehicle manufacturing continues to rise, the number of retired power batteries will also experience explosive growth, and solving the problem of recycling and reusing used power batteries is urgent.

[0003] At present, there are three main methods for recycling waste ternary lithium batteries: physical method, chemical method and biological method.

[0004] Physical methods include crushing flotation and mechanical grinding. Crushing flotation is a method of sorting by using the difference in physical and chemical properties of the surface of the material. That is, firstly, the complete waste lithium battery is crushed and sorted, and then the obtained battery material powder is heat treated to remove the organic binder. Finally, the battery material powder is flotated and separated according to the difference in hydrophilicity of the positive electrode and graphite surface in the battery material powder, so as to recover the valuable metal compound powder. The crushing flotation method has a simple process, which can effectively separate the positive and negative electrode materials, and the recovery rate of valuable metals is high. However, since all kinds of materials are crushed and mixed, it is difficult to separate and recover the subsequent copper foil, aluminum foil and metal shell fragments; and because the crushing easily causes the electrolyte LiPF6 to react with H2O to produce volatile gases such as HF, which causes environmental pollution, it is necessary to add auxiliary treatment facilities. Mechanical grinding is a method that uses the heat energy generated by mechanical grinding to cause the electrode material to react with the abrasive, so that the composite metal compounds in the electrode material that were originally bonded to the current collector are converted into salts. Mechanical grinding is also an effective method for recovering nickel, cobalt, manganese and lithium from waste lithium-ion batteries. The process is relatively simple, but it has high requirements for instruments and is prone to cause cobalt loss and difficulty in recovering aluminum foil.

[0005] The chemical method is a method of treating waste lithium batteries by chemical reaction process, which is generally divided into two methods: pyrometallurgy and hydrometallurgy. Pyrometallurgy is to remove the organic binder in the electrode material by high-temperature incineration, and at the same time make the metals and their compounds undergo oxidation-reduction reaction, recover the low-boiling point metals and their compounds in the form of condensation, and recover the metals in the slag and the alloy formed at high temperature by screening, pyrolysis, magnetic separation or chemical methods. Pyrometallurgy does not have high requirements for the composition of raw materials and is suitable for large-scale treatment of more complex batteries, but combustion will inevitably produce waste gas to pollute the environment, and high-temperature treatment also has high requirements for equipment. At the same time, it is also necessary to add purification and recovery equipment, etc., and the processing cost is high. Hydrometallurgy is a method of first dissolving with strong acid, and then extracting and gradually separating and removing impurities from elements such as lithium, nickel, cobalt and manganese. The hydrometallurgical process is more suitable for recycling waste lithium batteries with relatively single chemical components. It can be used alone or in combination with high-temperature metallurgy. It does not require high equipment and has low processing costs. It is a very mature treatment method suitable for the recycling of small and medium-sized waste lithium batteries.

[0006] Biometallurgy is still under research, which uses the metabolic process of microorganisms to achieve selective leaching of metal elements such as cobalt and lithium. The biological method has low energy consumption, low cost, and the microorganisms can be reused, with little pollution; however, the cultivation of microorganisms requires harsh conditions, long cultivation time, low leaching efficiency, and low reaction efficiency, and it is currently difficult to achieve industrialization.

[0007] Compared with traditional batteries such as lead-acid batteries, lithium batteries are more difficult to recycle due to their complex technical processes.

[0008] The market prospect of recycling a large number of waste lithium batteries is huge. However, due to the immaturity of recycling technology and the non-standard recycling process, it has not yet formed a good economic benefit.

[0009] The mainstream process in the market is to dissolve the waste battery powder with concentrated sulfuric acid, and then gradually separate and remove the elements such as lithium, nickel, cobalt and manganese through extraction. After lithium is recovered, it is prepared into battery-grade lithium carbonate, and nickel, cobalt and manganese metals are prepared into battery-grade nickel sulfate, cobalt sulfate and manganese sulfate respectively. This process is long, requires the use of a large amount of acid and alkali, produces a large amount of wastewater, has complex procedures, high energy consumption, and a high risk of environmental pollution. Summary of the invention

[0010] The present invention provides a lithium carbonate purification method and a lithium metal recovery method and a battery recovery method using the method, so as to reduce environmental pollution generated during the recovery process.

[0011] The present invention provides a lithium metal recovery method, comprising:

[0012] Prepare crude lithium carbonate, mix the crude lithium carbonate with deionized water to form a slurry, wherein the amount of deionized water added is 20 times the weight of the crude lithium carbonate;

[0013] The slurry is placed in a carbon dioxide atmosphere, the pH value of the slurry is controlled between 7 and 8, the temperature is maintained at 25-30° C., and the reaction time is 1-4 hours, so that the impurity components in the slurry are carbonized to obtain a carbonized material containing lithium bicarbonate;

[0014] After the carbonized material is subjected to resin removal and thermal decomposition, the thermally decomposed material is subjected to solid-liquid separation, specifically, centrifugal separation is performed by a centrifuge to obtain lithium carbonate with a purity of more than 99.5%.

[0015] The invention is based on carbonizing crude lithium carbonate to form lithium bicarbonate with better solubility, and uses impurity removal to separate it from other impurities with low solubility, and then cooperates with thermal decomposition to form lithium carbonate again after the purified lithium bicarbonate, removes impurities in the solution through solid-liquid separation, and makes the impurities in the crude lithium carbonate water-soluble, and purifies it through solid-liquid to form lithium carbonate.

[0016] It should be noted that the crude lithium carbonate used in the above lithium carbonate refining process may also be from other sources (such as crude lithium carbonate with a purity lower than 95% obtained by purchase or other purification methods).

[0017] Furthermore, the resin impurity removal and thermal decomposition of the carbonized material include:

[0018] The carbonized material is subjected to impurity removal, specifically, impurities such as calcium and magnesium in the carbonized material are removed by a resin adsorption method;

[0019] The carbonized material after impurities removal is thermally decomposed, and the thermal decomposition temperature is controlled at 90-95° C. and the time is 0.5-1 h to obtain the thermally decomposed material.

[0020] The carbonized material specifically includes a lithium bicarbonate solution, and the resin impurity removal specifically refers to adding resin to the carbonized material so as to utilize the resin to adsorb insoluble impurities in the carbonized material; thermal decomposition is formed by heating to convert the lithium bicarbonate back into lithium carbonate, which precipitates from the solution to form lithium carbonate particles.

[0021] The present invention adopts resin, which adsorbs and removes impurities in the carbonized material, and separates lithium carbonate from the carbonized material through thermal decomposition.

[0022] Furthermore, the solid-liquid separation of the thermally decomposed material to obtain lithium carbonate with a purity of more than 99.5% comprises:

[0023] The thermally decomposed material is centrifuged to obtain wet lithium carbonate and a thermally decomposed solution;

[0024] Drying the wet lithium carbonate to obtain dried lithium carbonate;

[0025] crushing the dried lithium carbonate to obtain crushed lithium carbonate;

[0026] The crushed lithium carbonate is demagnetized to remove ferromagnetic impurities to obtain lithium carbonate with a purity of more than 99.5%.

[0027] Among them, since the reprecipitated lithium carbonate is relatively small, it can be effectively separated by centrifugation. The lithium carbonate in the reprecipitation process is relatively small, which can effectively avoid the coating of the solution by lithium carbonate, and reduce the problem of lithium carbonate purity decreasing due to the coating of the solution containing impurities.

[0028] The present invention can effectively absorb magnetic metals such as iron, nickel and the like in lithium carbonate by demagnetizing lithium carbonate.

[0029] Furthermore, the preparation of crude lithium carbonate comprises:

[0030] A solid obtained by drying the electrolyte is prepared, and the solid obtained by drying the electrolyte is heated to a reaction temperature in a reducing atmosphere to perform a reduction reaction to obtain a corresponding reducing material;

[0031] The raw material is ball-milled and leached to obtain a ball-milled slurry, and the ball-milling time is 0.5-2h;

[0032] Use a filter press to filter the ball mill slurry to separate the grinding residue and the grinding liquid;

[0033] The grinding leaching liquid is placed in a carbon dioxide atmosphere, at a pH of 10-10.5 and a temperature of ≤60°C, and lithium hydroxide reacts to form lithium carbonate slurry;

[0034] The lithium carbonate slurry is filtered again to obtain a lithium-containing mother liquor and crude lithium carbonate;

[0035] The reducing atmosphere is one or more of natural gas and hydrogen.

[0036] Furthermore, the solid obtained by drying the electrolyte is heated to a reaction temperature in a reducing atmosphere to carry out a reduction reaction to obtain a corresponding reducing material, and the reaction temperature is 600-700°C.

[0037] Furthermore, the solid obtained by drying the electrolyte is prepared, and the method for preparing the solid obtained by drying the electrolyte includes:

[0038] Screening the waste batteries to obtain screened materials;

[0039] The screened material is alkali washed, and the alkali washed material is subjected to a first filter press to obtain an alkali washed residue;

[0040] The alkali-washed slag is washed with water and dried to obtain a dried material, which is the solid after the electrolyte is dried.

[0041] Furthermore, the sieve material is subjected to alkali washing, and the material after alkali washing is filtered to obtain alkali washing residue, and the alkali solution used for alkali washing is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and ammonia water.

[0042] A method for recovering residues generated during the purification of crude lithium carbonate, the method comprising:

[0043] After obtaining the grinding and leaching residue in the process of preparing crude lithium carbonate, the lithium-containing mother liquor and the thermal decomposition solution produced in the process of purifying crude lithium carbonate into lithium carbonate, one or more of the grinding and leaching residue, the lithium-containing mother liquor and the thermal decomposition solution are slurried, and the slurry is controlled to have a pH of 7-8 at normal temperature and pressure in a carbon dioxide atmosphere, and reacted for 1-4 hours to obtain a carbonized material and deep carbonized slag containing lithium bicarbonate.

[0044] Furthermore, the carbonized material containing lithium bicarbonate will be recycled to the purification process after the crude lithium carbonate is deeply carbonized, and finally lithium carbonate with a purity of more than 99.5% will be obtained.

[0045] Furthermore, the treatment of the deeply carburized slag includes:

[0046] The deep carbonized slag is subjected to filter pressing to obtain the carbonized slag;

[0047] Washing the carbonized slag with water to obtain a washed material;

[0048] The washed material is filtered to obtain a nickel-cobalt-manganese mixture;

[0049] The nickel-cobalt-manganese mixture is used as a raw material in other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 Schematic diagram of the purification process of crude lithium carbonate in an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of the process of residue recovery in an embodiment of the present invention;

[0053] Figure 3The present invention is a schematic diagram of a process for recycling waste batteries and extracting lithium carbonate in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only embodiments of a part of the present invention, rather than all embodiments.

[0055] In order to explain each processing of the present invention in detail, the above processing is divided into Examples 1-7 according to different stages and explained separately.

[0056] Example 1

[0057] The embodiment of the present invention discloses a method for recovering lithium metal, comprising the following steps:

[0058] S1: preparing crude lithium carbonate, mixing the crude lithium carbonate with deionized water to form a slurry, wherein the amount of deionized water added is 20 times the weight of the crude lithium carbonate;

[0059] Put the crude lithium carbonate in a carbonization reactor, add deionized water 20 times the weight of the crude lithium carbonate, and stir.

[0060] S2: placing the slurry under a carbon dioxide atmosphere, controlling the pH value of the slurry to be between 7 and 8, maintaining the temperature at 25-30° C., and reacting for 1-4 hours to carbonize the impurities in the slurry to obtain a carbonized material containing lithium bicarbonate;

[0061] Then slowly introduce carbon dioxide into the reactor. Control the pH value of the reaction system between 7 and 8. Under this pH condition, lithium carbonate is gradually converted into lithium bicarbonate. During the carbonization reaction, the temperature is maintained at 30°C (in practical applications, the temperature can be selected within the range of 25°C-30°C as long as it does not affect the results), and the reaction time is 2h (1-4h can be used depending on the period), until the crude lithium carbonate is completely converted into carbonized material (i.e., lithium bicarbonate solution).

[0062] S3: After resin impurity removal and thermal decomposition of the carbonized material, the thermally decomposed material is subjected to solid-liquid separation, specifically, centrifugal separation is performed by a centrifuge to obtain lithium carbonate with a purity of more than 99.5%.

[0063] The pre-treated chelating resin is filled into the resin column, and the carbonized material solution is passed through the resin column so that the +2-valent impurity ions such as calcium and magnesium in the solution are adsorbed by the resin. During the resin impurity removal process, the impurity ion content of the effluent is regularly tested. When the impurity ion content is detected to be close to or reaches the specified standard, the feeding is stopped and the resin adsorption is considered to be saturated. The solution after the resin impurity removal is the impurity-removed material;

[0064] Transfer the resin material after impurities removal to a clean container for thermal decomposition. Raise the temperature to 92°C (in practical applications, the temperature can be selected within the range of 90-95°C as long as it does not affect the results) and maintain it at this temperature for 1 hour (0.5-1 hour as required). During the thermal decomposition process, lithium bicarbonate decomposes to regenerate lithium carbonate and releases carbon dioxide gas. After the thermal decomposition is completed, the thermally decomposed material is obtained.

[0065] S3: Drying, crushing and demagnetizing the materials after thermal decomposition after solid-liquid separation;

[0066] The material after thermal decomposition is transferred to a high-speed centrifuge for centrifugal separation. Through centrifugation, the solid lithium carbonate (wet lithium carbonate) is separated from the thermal decomposition solution to obtain wet lithium carbonate precipitate and thermal decomposition solution, which are collected for further processing and analysis;

[0067] The wet lithium carbonate obtained by centrifugal separation is placed in an electric heating blast drying oven for drying until the water in the wet lithium carbonate is completely evaporated to obtain dry lithium carbonate. The dry lithium carbonate is then placed in a small jaw crusher for crushing to obtain lithium carbonate;

[0068] The lithium carbonate is demagnetized by a magnetic separator (other demagnetization equipment can be selected according to actual conditions) to remove the magnetic impurities that may be contained therein. After demagnetization, purified lithium carbonate is obtained, and after testing, the lithium carbonate meets the standards of battery-grade lithium carbonate.

[0069] Through the above detailed processing steps, crude lithium carbonate is effectively purified, and the purity of lithium carbonate is significantly improved, and the recovery rate of lithium in the whole process reaches 98.5%. This method is not only applicable to the crude lithium carbonate of a specific source in the embodiment of the present invention, but also can be applied to the purification of low-purity lithium carbonate from other sources, and has wide applicability and practicality. In the actual operation process, the parameters of each step can be optimized and adjusted according to the specific circumstances to further improve the purification effect and production efficiency.

[0070] The crude lithium carbonate in the embodiments of the present invention can be recovered from waste batteries or obtained from other places. Embodiment 2-3 is the steps of recovering crude lithium carbonate from waste batteries:

[0071] Example 2

[0072] S10: Screening the waste batteries to obtain screened materials;

[0073] Place the used batteries on a vibrating screen for screening. During the vibration process, smaller particles and powdery substances fall through the screen and become undersize, while larger impurities such as battery shell fragments and plastic parts are left on the screen. Collect the undersize and place it in a sealed container for later use.

[0074] S20: alkali-washing the screened material, and performing a first filter press on the alkali-washed material to obtain an alkali-washed residue;

[0075] Prepare a sodium hydroxide solution with a concentration of 10 mol / L as the alkali solution (in the actual operation process, 3-10 mol / L of alkali solution can be selected, and the alkali solution can be selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and ammonia water, which does not affect the result). Pour the screened material into the reactor, add the alkali solution, and start the reactor. Under this condition, an alkali washing reaction is carried out (in the alkali washing process, the sodium hydroxide solution reacts chemically with certain metal oxides, acidic substances, etc. in the waste batteries, dissolving them or converting them into easily separable substances). After the alkali washing reaction is completed, the material is filtered for the first time using a filter press to obtain an alkali washing residue (the alkali washing residue mainly contains solid matter that has not reacted with the alkali solution and a small amount of residual alkali solution and impurities). S30: Wash the alkali washing residue with water and dry it to obtain a dried material, which is the solid after the electrolyte is dried;

[0076] Transfer the alkali-washed residue to a clean container, wash it with deionized water, and add deionized water. After stirring evenly, let it stand and then filter it to remove the supernatant. Repeat the water washing operation 3 times to fully remove the alkali solution and other soluble impurities remaining in the alkali-washed residue. After the water washing is completed, transfer the material to an electric heating blast drying oven for drying. After the drying is completed, a dried electrolyte solid is obtained, which can be further processed or analyzed to achieve resource recycling.

[0077] S40: heating the solid obtained by drying the electrolyte to a reaction temperature in a reducing atmosphere to perform a reduction reaction to obtain a corresponding reducing material;

[0078] The solid after the electrolyte is dried is heated to the reaction temperature in a reducing atmosphere to perform a reduction reaction to obtain the corresponding reducing material. The dried material is evenly placed in a quartz boat, and then the quartz boat is slowly pushed into the quartz tube of the tubular reduction furnace. After closing the furnace door, nitrogen is first introduced for purging to remove the air in the furnace;

[0079] After the purging is completed, switch to hydrogen atmosphere. Raise the furnace temperature to 650°C (in actual application, the temperature can be any temperature in the range of 600-700°C, as long as it does not affect the results). Maintain the reduction time at this temperature for 3 hours, so that the lithium compound in the dried material is reduced to the corresponding low-valent state or metallic state under the hydrogen atmosphere;

[0080] After the reduction is completed, the quartz boat is taken out and cooled to room temperature under nitrogen protection (inert gas is sufficient). The reduced material is then treated by water immersion. The material is transferred to a leaching container, and deionized water is added and stirred to obtain a reduced raw material solution.

[0081] S50: ball-milling the reducing material to obtain a ball-milled slurry, the ball-milling time being 0.5-2h;

[0082] The obtained reducing material solution is filtered to remove unreacted large particle impurities, and the obtained filter residue is subjected to ball milling. The filter residue is transferred to the ball milling tank of a planetary ball mill for ball milling. After ball milling for 1 hour (in actual application, the ball milling time can be selected within 0.5-2 hours), a ball milling slurry is obtained;

[0083] S60: using a filter press to filter the ball mill slurry to separate the grinding residue and the grinding liquid;

[0084] The ball mill slurry is transferred to a plate and frame filter press for filtration, and the solid and liquid in the slurry are separated to obtain grinding residue and grinding liquid. The grinding residue mainly contains impurities such as nickel, cobalt and manganese metals and oxides that have not been leached, which can be subsequently recycled or further studied. The grinding liquid contains dissolved lithium compounds and other components.

[0085] S70: placing the grinding leaching liquid in a carbon dioxide atmosphere at a pH of 10-10.5 and a temperature of ≤60° C., so that lithium hydroxide reacts to form lithium carbonate slurry;

[0086] Transfer the grinding solution to the carbonization reactor, turn on the stirring device, and then introduce carbon dioxide. As carbon dioxide is introduced, the lithium substance in the grinding solution combines with carbon dioxide to form lithium carbonate precipitate. During the reaction, the reaction progress is controlled by monitoring parameters such as the pH value and conductivity of the solution. When the pH value of the solution stabilizes at around 10-10.5, the reaction temperature is ≤60°C, and the conductivity change tends to be flat, it indicates that the carbonization lithium precipitation reaction is close to completion. At this point, lithium carbonate slurry is obtained;

[0087] S80: filtering the lithium carbonate slurry again to obtain a lithium-containing mother liquor and crude lithium carbonate;

[0088] The lithium carbonate slurry is subjected to a filter press operation again to obtain a lithium-containing mother liquor and crude lithium carbonate. The lithium-containing mother liquor can be returned to the carbonization and lithium precipitation step for recycling to improve the recovery rate of lithium. After further washing, drying and other treatments, the crude lithium carbonate can obtain a lithium carbonate product with a higher purity. The purity of the crude lithium carbonate is 92.36%.

[0089] Example 3

[0090] S10: Screening the waste batteries to obtain screened materials;

[0091] Place the used batteries on a vibrating screen for screening. During the vibration process, smaller particles and powdery substances fall through the screen and become undersize, while larger impurities such as battery shell fragments and plastic parts are left on the screen. Collect the undersize and place it in a sealed container for later use.

[0092] S20: alkali-washing the screened material, and performing a first filter press on the alkali-washed material to obtain an alkali-washed residue;

[0093] Prepare a sodium hydroxide solution with a concentration of 10 mol / L as the alkali solution (in the actual operation process, 3-10 mol / L of alkali solution can be selected, and the alkali solution can be selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and ammonia water, which does not affect the result). Pour the screened material into the reactor, add the alkali solution, and start the reactor. Under this condition, an alkali washing reaction is carried out (in the alkali washing process, the sodium hydroxide solution reacts chemically with certain metal oxides, acidic substances, etc. in the waste batteries, dissolving them or converting them into easily separable substances). After the alkali washing reaction is completed, the material is filtered for the first time using a filter press to obtain an alkali washing residue (the alkali washing residue mainly contains solid matter that has not reacted with the alkali solution and a small amount of residual alkali solution and impurities). S30: Wash the alkali washing residue with water and dry it to obtain a dried material, which is the solid after the electrolyte is dried;

[0094] Transfer the alkali-washed residue to a clean container, wash it with deionized water, and add deionized water. After stirring evenly, let it stand and then filter it to remove the supernatant. Repeat the water washing operation 3 times to fully remove the alkali solution and other soluble impurities remaining in the alkali-washed residue. After the water washing is completed, transfer the material to an electric heating blast drying oven for drying. After the drying is completed, a dried electrolyte solid is obtained, which can be further processed or analyzed to achieve resource recycling.

[0095] S40: heating the solid obtained by drying the electrolyte to a reaction temperature in a reducing atmosphere to perform a reduction reaction to obtain a corresponding reducing material;

[0096] The solid after the electrolyte is dried is heated to the reaction temperature in a reducing atmosphere to perform a reduction reaction to obtain the corresponding reducing material. The dried material is evenly placed in a quartz boat, and then the quartz boat is slowly pushed into the quartz tube of the tubular reduction furnace. After closing the furnace door, nitrogen is first introduced for purging to remove the air in the furnace;

[0097] After the purging is completed, switch to natural gas atmosphere. Raise the furnace temperature to 650°C (in actual application, the temperature can be any temperature in the range of 600-700°C, as long as it does not affect the results). Maintain the reduction time at this temperature for 3 hours, so that the lithium compounds in the dried material are reduced to the corresponding low-valent state or metallic state under the natural gas atmosphere;

[0098] After the reduction is completed, the quartz boat is taken out and cooled to room temperature under nitrogen protection (inert gas is sufficient). The reduced material is then treated by water immersion. The material is transferred to a leaching container, and deionized water is added and stirred to obtain a reduced raw material solution.

[0099] S50: ball-milling the reducing material to obtain a ball-milled slurry, the ball-milling time being 0.5-2h;

[0100] The obtained reducing material solution is filtered to remove unreacted large particle impurities, and the obtained filter residue is subjected to ball milling. The filter residue is transferred to the ball milling tank of a planetary ball mill for ball milling. After ball milling for 1 hour (in actual application, the ball milling time can be selected within 0.5-2 hours), a ball milling slurry is obtained;

[0101] S60: using a filter press to filter the ball mill slurry to separate the grinding residue and the grinding liquid;

[0102] The ball mill slurry is transferred to a plate and frame filter press for filtration, and the solid and liquid in the slurry are separated to obtain grinding residue and grinding liquid. The grinding residue mainly contains impurities such as nickel, cobalt and manganese metals and oxides that have not been leached, which can be subsequently recycled or further studied. The grinding liquid contains dissolved lithium compounds and other components.

[0103] S70: placing the grinding leaching liquid in a carbon dioxide atmosphere at a pH of 10-10.5 and a temperature of ≤60° C., so that lithium hydroxide reacts to form lithium carbonate slurry;

[0104] Transfer the grinding solution to the carbonization reactor, turn on the stirring device, and then introduce carbon dioxide. As carbon dioxide is introduced, the lithium substance in the grinding solution combines with carbon dioxide to form lithium carbonate precipitate. During the reaction, the reaction progress is controlled by monitoring parameters such as the pH value and conductivity of the solution. When the pH value of the solution stabilizes at around 10-10.5, the reaction temperature is ≤60°C, and the conductivity change tends to be flat, it indicates that the carbonization lithium precipitation reaction is close to completion. At this point, lithium carbonate slurry is obtained;

[0105] S80: filtering the lithium carbonate slurry again to obtain a lithium-containing mother liquor and crude lithium carbonate;

[0106] The lithium carbonate slurry is subjected to a filter press operation again to obtain a lithium-containing mother liquor and crude lithium carbonate. The lithium-containing mother liquor can be returned to the carbonization and lithium precipitation step for recycling to improve the recovery rate of lithium. After further washing, drying and other treatments, the crude lithium carbonate can obtain a lithium carbonate product with a higher purity. The purity of the crude lithium carbonate is 92.15%.

[0107] Example 2 and Example 3 are both specific implementation steps for extracting crude lithium carbonate from waste batteries. The difference between the two is that after the purging in step 4 of Example 2 is completed, the atmosphere is switched to hydrogen, while after the purging in step 4 of Example 3 is completed, the atmosphere is switched to hydrogen. The two use different reducing gases mainly to illustrate that both hydrogen and natural gas can be used as reducing gases, which does not affect the final purification effect.

[0108] Through the treatment in Example 2 and Example 3, lithium carbonate can be effectively extracted from the dried waste battery material, resource recycling can be achieved, and lithium carbonate products with a certain purity can be obtained, which provides a feasible method for resource processing of waste batteries. At the same time, the parameters in each step can be optimized and adjusted according to actual conditions to further improve the extraction efficiency and product quality.

[0109] The methods of Examples 1-3 are not only applicable to crude lithium carbonate from a specific source in the embodiments of the present invention, but can also be applied to the purification of low-purity lithium carbonate from other sources, and have wide applicability and practicality. In the actual operation process, the parameters of each step can be optimized and adjusted according to the specific situation to further improve the purification effect and production efficiency.

[0110] The following are specific examples of Examples 4-7: After slurrying one or more of the grinding and leaching residues, lithium-containing mother liquor and thermal decomposition solution produced in Examples 1-3, carbon dioxide is introduced at room temperature and pressure to control the pH of the slurry to 7-8, and the reaction is carried out for 1-4 hours to obtain a carbonized material containing lithium bicarbonate and a deep carbonized slag, wherein the grinding and leaching residues, lithium-containing mother liquor and thermal decomposition solution are all produced in the production process of Examples 1-3.

[0111] The specific embodiments are as follows:

[0112] Example 4

[0113] In Example 4 of the present invention, the waste grinding and leaching residues produced in Examples 1-3 are treated as follows:

[0114] S101: taking one or more of the grinding leaching residue, the lithium-containing mother liquor and the thermal decomposition solution and slurrying them, introducing carbon dioxide at normal temperature and pressure, controlling the pH of the slurry to 7-8, reacting for 1-4 hours to obtain a carbonized material and a deeply carbonized slag, the carbonized material is recovered for purification after deep carbonization of crude lithium carbonate, and the deeply carbonized material is further processed;

[0115] Take the ground leaching residue and add water to make a slurry, place the slurry in a reactor and stir it, slowly introduce carbon dioxide into the reactor at normal temperature and pressure to control the pH of the slurry between 7-8. Under this pH condition, the reaction time is 3h (in practical applications, the time within the range of 2-4h can be selected according to the situation, as long as it does not affect the results). In this process, impurities are carbonized to form carbonized materials containing lithium bicarbonate and deeply carbonized slag. The deeply carbonized slag mainly contains metals such as nickel, cobalt, and manganese.

[0116] S102: filtering the deep carbonized slag to obtain carbonized slag;

[0117] The deeply carbonized slag is taken out from the reactor and transferred to a plate and frame filter press for filtration to separate the solid and the liquid to obtain the carbonized slag.

[0118] S103: washing the carbonized slag with water to obtain a washed material;

[0119] The carbonized slag is transferred to a clean container, and a proper amount of deionized water is added to perform a water washing operation to obtain a washed material.

[0120] S104: filtering the washed material to obtain a nickel-cobalt-manganese mixture;

[0121] The washed material is filtered again to obtain a nickel-cobalt-manganese mixture, which can be used as a raw material in other fields to achieve resource recycling.

[0122] The carbonized material containing lithium bicarbonate with carbonized impurities obtained in the deep carbonization process can be used in the purification process of crude lithium carbonate after deep carbonization. The specific operation is similar to the lithium carbonate purification method described above. After resin impurity removal, thermal decomposition, centrifugal separation, drying and crushing, and demagnetization, lithium carbonate with a purity of more than 99.5% can be finally obtained.

[0123] Example 5

[0124] In Example 5 of the present invention, the lithium-containing mother solution produced in Example 1-3 is treated as follows:

[0125] S101: taking one or more of the grinding leaching residue, the lithium-containing mother liquor and the thermal decomposition solution and slurrying them, introducing carbon dioxide at normal temperature and pressure, controlling the pH of the slurry to 7-8, reacting for 1-4 hours to obtain a carbonized material and a deeply carbonized slag, the carbonized material is recovered for purification after deep carbonization of crude lithium carbonate, and the deeply carbonized material is further processed;

[0126] Take the lithium-containing mother liquor and add water to make a slurry, place the slurry in a reactor and stir, slowly introduce carbon dioxide into the reactor at normal temperature and pressure, and control the pH of the slurry between 7-8. Under this pH condition, the reaction time is 3h (in practical applications, the time in the range of 2-4h can be selected according to the situation, as long as it does not affect the results). In this process, impurities are carbonized to form carbonized materials containing lithium bicarbonate and deep carbonized slag. The deep carbonized slag mainly contains metals such as nickel, cobalt, and manganese.

[0127] S102: filtering the deep carbonized slag to obtain carbonized slag;

[0128] The deeply carbonized slag is taken out from the reactor and transferred to a plate and frame filter press for filtration to separate the solid and the liquid to obtain the carbonized slag.

[0129] S103: washing the carbonized slag with water to obtain a washed material;

[0130] The carbonized slag is transferred to a clean container, and an appropriate amount of deionized water is added to perform a water washing operation to obtain a washed material.

[0131] S104: filtering the washed material to obtain a nickel-cobalt-manganese mixture;

[0132] The washed material is filtered again to obtain a nickel-cobalt-manganese mixture, which can be used as a raw material in other fields to achieve resource recycling.

[0133] The carbonized material containing lithium bicarbonate with carbonized impurities obtained in the deep carbonization process can be used in the purification process of crude lithium carbonate after deep carbonization. The specific operation is similar to the lithium carbonate purification method described above. After resin impurity removal, thermal decomposition, centrifugal separation, drying and crushing, and demagnetization, lithium carbonate with a purity of more than 99.5% can be finally obtained.

[0134] Example 6

[0135] In Example 6 of the present invention, the waste thermal decomposition solution generated in Examples 1-3 is treated as follows:

[0136] S101: taking one or more of the grinding leaching residue, the lithium-containing mother liquor and the thermal decomposition solution and slurrying them, introducing carbon dioxide at normal temperature and pressure, controlling the pH of the slurry to 7-8, reacting for 1-4 hours to obtain a carbonized material and a deeply carbonized slag, the carbonized material is recovered for purification after deep carbonization of crude lithium carbonate, and the deeply carbonized material is further processed;

[0137] Take the thermal decomposition solution to make a slurry, place the slurry in a reactor and stir it, slowly introduce carbon dioxide into the reactor at normal temperature and pressure, and control the pH of the slurry between 7-8. Under this pH condition, the reaction time is 3h (in practical applications, the time in the range of 2-4h can be selected according to the situation, as long as it does not affect the results). In this process, impurities are carbonized to form carbonized materials containing lithium bicarbonate and deep carbonized slag. The deep carbonized slag mainly contains metals such as nickel, cobalt, and manganese.

[0138] S102: filtering the deep carbonized slag to obtain carbonized slag;

[0139] The deeply carbonized slag is taken out from the reactor and transferred to a plate and frame filter press for filtration to separate the solid and the liquid to obtain the carbonized slag.

[0140] S103: washing the carbonized slag with water to obtain a washed material;

[0141] The carbonized slag is transferred to a clean container, and a proper amount of deionized water is added to perform a water washing operation to obtain a washed material.

[0142] S104: filtering the washed material to obtain a nickel-cobalt-manganese mixture;

[0143] The washed material is filtered again to obtain a nickel-cobalt-manganese mixture, which can be used as a raw material in other fields to achieve resource recycling.

[0144] The carbonized material containing lithium bicarbonate with carbonized impurities obtained in the deep carbonization process can be used in the purification process of crude lithium carbonate after deep carbonization. The specific operation is similar to the lithium carbonate purification method described above. After resin impurity removal, thermal decomposition, centrifugal separation, drying and crushing, and demagnetization, lithium carbonate with a purity of more than 99.5% can be finally obtained.

[0145] Embodiment 7:

[0146] In Example 7 of the present invention, the waste grinding leaching residue, lithium-containing mother liquor and thermal decomposition solution generated in Examples 1-3 are treated as follows:

[0147] S101: taking one or more of the grinding leaching residue, the lithium-containing mother liquor and the thermal decomposition solution and slurrying them, introducing carbon dioxide at normal temperature and pressure, controlling the pH of the slurry to 7-8, reacting for 1-4 hours to obtain a carbonized material and a deeply carbonized slag, the carbonized material is recovered for purification after deep carbonization of crude lithium carbonate, and the deeply carbonized material is further processed;

[0148] Take the grinding leaching residue, lithium-containing mother liquor and thermal decomposition solution and mix them evenly in a certain proportion to form a slurry (in actual application, according to the production situation, one or more of the grinding leaching residue, lithium-containing mother liquor and thermal decomposition solution can be taken for treatment), take the thermal decomposition solution to make a slurry, place the slurry in a reactor and stir, slowly introduce carbon dioxide into the reactor at normal temperature and pressure, and control the pH of the slurry between 7-8. Under this pH condition, the reaction time is 3h (in actual application, the time within the range of 2-4h can be selected according to the situation, as long as it does not affect the result). In this process, impurities are carbonized to form carbonized materials and deep carbonized slag containing lithium bicarbonate. The deep carbonized slag mainly contains metals such as nickel, cobalt, and manganese.

[0149] S102: filtering the deep carbonized slag to obtain carbonized slag;

[0150] The deeply carbonized slag is taken out from the reactor and transferred to a plate and frame filter press for filtration to separate the solid and the liquid to obtain the carbonized slag.

[0151] S103: washing the carbonized slag with water to obtain a washed material;

[0152] The carbonized slag is transferred to a clean container, and an appropriate amount of deionized water is added to perform a water washing operation to obtain a washed material.

[0153] S104: filtering the washed material to obtain a nickel-cobalt-manganese mixture;

[0154] The washed material is filtered again to obtain a nickel-cobalt-manganese mixture, which can be used as a raw material in other fields to achieve resource recycling.

[0155] The carbonized material containing lithium bicarbonate with carbonized impurities obtained in the deep carbonization process can be used in the purification process of crude lithium carbonate after deep carbonization. The specific operation is similar to the lithium carbonate purification method described above. After resin impurity removal, thermal decomposition, centrifugal separation, drying and crushing, and demagnetization, lithium carbonate with a purity of more than 99.5% can be finally obtained.

[0156] Through Examples 5-7, the effective treatment of the residues in the preparation and purification process of lithium carbonate is achieved, the resource recovery rate is improved, and the discharge of waste is reduced, which has important economic and environmental significance. In the actual operation process, the parameters of each step can be optimized and adjusted according to the specific situation to achieve the best treatment effect. Taking the 523 type positive electrode material as an example, the 523 type positive electrode material is: LiNi 0.5 Co 0.2 Mn 0.3 O2, the lithium extraction material obtained after treatment is: Ni 0.5 Co 0.2 Mn 0.3 O0.3 It can be seen that the treatment methods of Examples 5-7 of the present invention effectively treat the grinding leaching residue, lithium-containing mother liquor and thermal decomposition solution, and the obtained deep carbonized slag is nickel, cobalt and manganese metals and oxides, which can be sold as raw materials, and the obtained carbonized material containing lithium bicarbonate can be used for lithium extraction again.

[0157] Among them, deep carbonization specifically refers to: at room temperature and pressure, controlling the reaction pH value to 7-8, reacting for 1-4 hours, introducing an excess of carbon dioxide into the slurry to carbonize the material, so that the lithium metal element in the slurry forms bicarbonate, which is convenient for subsequent separation and purification. It should be noted that technicians can calculate the appropriate reaction conditions such as the amount of carbon dioxide introduced, pressure, reaction temperature, etc. according to the actual amount of raw materials to ensure the deep carbonization of the grinding leaching residue, so the specific reaction conditions are not repeated here.

[0158] Comparative example: Traditional acid leaching and alkali precipitation process to recover and purify the electrolyte from waste batteries

[0159] Step 1: Acid leaching

[0160] Place the waste battery containing electrolyte into a glass beaker and add an appropriate amount of sulfuric acid solution. Determine the amount of sulfuric acid solution based on the mass of the waste battery and the content of the electrolyte, generally maintaining a solid-liquid ratio of 1:3 (mass ratio). Turn on the stirring rod for stirring. Perform an acid leaching reaction at room temperature. During this process, sulfuric acid reacts with metal compounds and impurities in the waste battery to release components in the electrolyte, such as lithium salts, organic solvents, etc.

[0161] Step 2: Filtering

[0162] After the acid leaching reaction is completed, filter the solution using filter paper and a funnel. Slowly pour the solution into the funnel and remove insoluble solid impurities such as metal oxides, plastic fragments, etc. through the filtering effect of the filter paper. Collect the filtered solution in another clean container.

[0163] Step 3: Alkali precipitation treatment

[0164] Use a pH meter to measure the pH of the filtered solution. Then, slowly add sodium hydroxide solution while stirring the solution. By controlling the dripping rate of the sodium hydroxide solution, adjust the pH of the solution to 9. At this pH, specific metal ions and impurities will form precipitation.

[0165] Step 4: Filter again

[0166] After the alkaline precipitation reaction is completed, the filtration operation is performed again. The solution is filtered through filter paper and a funnel to separate the precipitate and the solution containing the purified electrolyte components. The precipitate mainly contains metal hydroxides and other impurities, which can be further processed or disposed of. The filtered solution is collected, which is the waste battery electrolyte that has been recovered and purified by the traditional acid leaching and alkaline precipitation process.

[0167] By conducting an in-depth comparative analysis of the production process and products of Examples 1-7 of the present invention and the control example, it can be seen that the improvement of the recycling process provided by the present invention is obvious.

[0168] In Examples 1-7 of the present invention, starting from the treatment of waste batteries, a series of steps including screening, alkali washing, reduction, ball milling, filter pressing, carbonization and lithium precipitation, deep carbonization, resin impurity removal, thermal decomposition, centrifugal separation, drying and crushing, demagnetization and residue treatment are carried out to achieve efficient recovery and utilization of valuable resources in waste batteries, especially the purification of lithium carbonate to a high purity. Although the traditional acid leaching and alkali precipitation process used in the control example can achieve the recovery and purification of waste battery electrolyte to a certain extent, it has many shortcomings in terms of efficiency, purity and environmental protection. For example, harmful gases may be generated during the acid leaching process, causing pollution to the environment; multi-step operation makes the process more complicated, resulting in relatively low efficiency; and the purity of the purified electrolyte may not be as high as the method of the present invention. The specific advantages of the present invention are as follows:

[0169] In terms of wastewater generation, as a complete recycling process, embodiments 1-8 of the present invention can reduce the generation of 15-20 tons of saline wastewater for every ton of lithium carbonate recycled. Due to the differences in the types of waste batteries, the amount of wastewater generated during the recycling process of the embodiments of the present invention will vary, but overall, there is a significant improvement in wastewater reduction, reducing the cost and difficulty of wastewater treatment.

[0170] The embodiment of the present invention also includes a carbon dioxide collection process during the treatment process: hydrogen or natural gas combustion is used to indirectly heat the furnace tube, thereby heating the reduction process, and the carbon dioxide generated by the combustion is introduced into the wet lithium extraction in Example 4. Carbon recovery is achieved by using the carbon dioxide generated by the carbonaceous heat treatment as a carbonizing agent to achieve carbon capture. According to actual monitoring, the embodiment of the present invention uses the carbon dioxide collection process, and the carbon dioxide capture rate exceeds 50%, effectively reducing the carbon emissions of the production process.

[0171] Compared with the traditional hydrometallurgical lithium extraction and impurity removal process which requires the use of a large amount of acid and alkali, the embodiment of the present invention only uses alkali solution, resin, and carbon dioxide, without adding any other auxiliary reagents, to achieve effective impurity removal of impurities in the electrolyte. The technical process is simple and utilizes a deep carbonization process to effectively reduce wastewater discharge. Actual tests have shown that the recycling cost is reduced by 40%, which is both economical and energy-saving and environmentally friendly.

[0172] At the same time, in an embodiment of the present invention, the product obtained after a series of processing steps will enter a machine-selected demagnetization device. In this device, a strong electromagnetic field can be used to effectively remove magnetic substances in the product, thereby further improving the purity and quality of the product. After demagnetization treatment, the final product can be obtained. The product appears as a black powder. It should be noted that its color is not a single fixed color, and the specific color is determined by the metal composition in the product. For example, if the product contains more metals such as nickel and cobalt, it may present a specific dark tone.

[0173] In summary, the embodiment of the present invention utilizes carbon heat treatment combined with water leaching technology to achieve lithium extraction, with a lithium recovery rate of no less than 98.5%, and the purity of the prepared lithium carbonate product exceeds 99.5%, reaching the battery-grade lithium carbonate product standard, which can be used in the preparation of lithium batteries, and the comprehensive recovery rate of nickel, cobalt and manganese metals is tested to be no less than 99.2%, and can also be used as a raw material for lithium battery production. In this process, the carbon dioxide generated by carbon heat treatment is used as a carbonizing agent to achieve carbon capture, and its capture rate exceeds 50%, effectively reducing carbon emissions in the lithium battery recycling process.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, the technicians can still modify or replace the specific implementation mode of the present invention with equivalents, but these modifications or changes do not deviate from the scope of protection of the pending claims of the present application.

Claims

1. A lithium metal recovery method, characterized in that: The method comprises: Prepare crude lithium carbonate, mix the crude lithium carbonate with deionized water to form a slurry, wherein the amount of deionized water added is 20 times the weight of the crude lithium carbonate; The slurry is placed in a carbon dioxide atmosphere, the pH value of the slurry is controlled between 7 and 8, the temperature is maintained at 25-30° C., and the reaction time is 1-4 hours, so that the impurity components in the slurry are carbonized to obtain a carbonized material containing lithium bicarbonate; After the carbonized material is subjected to resin removal and thermal decomposition, the thermally decomposed material is subjected to solid-liquid separation, specifically, centrifugal separation is performed by a centrifuge to obtain lithium carbonate with a purity of more than 99.5%.

2. A lithium metal recovery method according to claim 1, characterized in that: The resin impurity removal and thermal decomposition of the carbonized material include: The carbonized material is subjected to impurity removal, specifically, impurities such as calcium and magnesium in the carbonized material are removed by a resin adsorption method; The carbonized material after impurities removal is thermally decomposed, and the thermal decomposition temperature is controlled at 90-95° C. and the time is 0.5-1 h to obtain the thermally decomposed material.

3. A lithium metal recovery method according to claim 1, characterized in that: The solid-liquid separation of the thermally decomposed material to obtain lithium carbonate with a purity of more than 99.5% comprises: The thermally decomposed material is centrifuged to obtain wet lithium carbonate and a thermally decomposed solution; Drying the wet lithium carbonate to obtain dried lithium carbonate; crushing the dried lithium carbonate to obtain crushed lithium carbonate; The crushed lithium carbonate is demagnetized to remove ferromagnetic impurities to obtain lithium carbonate with a purity of more than 99.5%.

4. A lithium metal recovery method according to any one of claims 1 to 3, characterized in that: The preparation of crude lithium carbonate comprises: A solid obtained by drying the electrolyte is prepared, and the solid obtained by drying the electrolyte is heated to a reaction temperature in a reducing atmosphere to perform a reduction reaction to obtain a corresponding reducing material; The raw material is ball-milled and leached to obtain a ball-milled slurry, and the ball-milling time is 0.5-2h; Use a filter press to filter the ball mill slurry to separate the grinding residue and the grinding liquid; The grinding leaching liquid is placed in a carbon dioxide atmosphere, at a pH of 10-10.5 and a temperature of ≤60°C, and lithium hydroxide reacts to form lithium carbonate slurry; The lithium carbonate slurry is filtered again to obtain a lithium-containing mother liquor and crude lithium carbonate; The reducing atmosphere is one or more of natural gas and hydrogen.

5. A lithium metal recovery method according to claim 4, characterized in that: The solid obtained by drying the electrolyte is prepared, and the solid obtained by drying the electrolyte is heated to a reaction temperature in a reducing atmosphere to carry out a reduction reaction to obtain a corresponding reducing material, and the reaction temperature is 600-700°C.

6. A lithium metal recovery method according to claim 4, characterized in that: The solid obtained by drying the electrolyte is prepared, and the method for preparing the solid obtained by drying the electrolyte includes: Screening the waste batteries to obtain screened materials; The screened material is alkali washed, and the alkali washed material is filter pressed to obtain alkali washed residue; The alkali-washed slag is washed with water and dried to obtain a dried material, which is the solid after the electrolyte is dried.

7. A lithium metal recovery method according to claim 6, characterized in that: The sieve material is subjected to alkali washing, and the material after alkali washing is subjected to a first filter press to obtain alkali washed residue, and the alkali solution used for alkali washing is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and ammonia water.

8. A method for recovering the residue of any one of the methods of claims 1 to 7, characterized in that: The method for recovering the residue comprises: After obtaining the grinding and leaching residue in the process of preparing crude lithium carbonate, the lithium-containing mother liquor and the thermal decomposition solution produced in the process of purifying crude lithium carbonate into lithium carbonate, one or more of the grinding and leaching residue, the lithium-containing mother liquor and the thermal decomposition solution are slurried, and the slurry is controlled to have a pH of 7-8 at normal temperature and pressure in a carbon dioxide atmosphere, and reacted for 1-4 hours to obtain a carbonized material and deep carbonized slag containing lithium bicarbonate.

9. A residue recovery method according to claim 8, characterized in that: The carbonized material containing lithium bicarbonate will be recycled to the purification process after the crude lithium carbonate is deeply carbonized, and lithium carbonate with a purity of more than 99.5% will be finally obtained.

10. A residue recovery method according to claim 9, characterized in that: The treatment of the deep carburized slag comprises: The deep carbonized slag is subjected to filter pressing to obtain the carbonized slag; Washing the carbonized slag with water to obtain a washed material; The washed material is filtered to obtain a nickel-cobalt-manganese mixture; The nickel-cobalt-manganese mixture is used as a raw material in other fields.

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