A method for recycling waste phosphate lithium battery positive electrode material

Abstract

The present invention provides a method for recycling waste phosphate-based lithium battery positive electrode materials, and belongs to the technical field of recycling positive electrode materials for lithium ion batteries. The present invention adopts a molten salt method to dissolve waste phosphate-based lithium battery positive electrode materials in molten salt, that is, the divalent metals and lithium in the positive electrode materials are dissolved in the molten salt in the form of ions, and the phosphate reacts with the molten salt to form apatite, and the phosphorus in the positive electrode materials is completely recovered; then, the divalent metals in the positive electrode materials are precipitated by electrodeposition, and all of them are recovered; then, the lithium-containing solution is reacted with oxalic acid to recover calcium oxalate in the solution, and then reacted with phosphate to recover lithium; the present invention adopts a process of molten salt dissolution combined with electrodeposition to achieve the complete recovery of iron / nickel / cobalt / manganese, lithium and phosphate ions in waste phosphate-based lithium positive electrode materials, and finally obtains the products of metal iron / nickel / cobalt / manganese, apatite and lithium salt, and the products have high added value and good process benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling positive electrode materials of lithium ion batteries, and in particular relates to a method for recycling positive electrode materials of waste phosphate-based lithium batteries. Background Art

[0002] Phosphate-based lithium-ion batteries are widely used, and are well known for their use in electric vehicles, electric cars, laptops, mobile phones, etc. In the future, new energy vehicles will be the top priority for the development of the automotive industry, and as one of the main driving forces for new energy vehicles, phosphate-based lithium-ion batteries will have a considerable application in the future. Since batteries have a certain cycle and a service life of about 3 to 5 years, according to the statistical growth of China's lithium iron phosphate battery production, the application of lithium iron phosphate batteries continues to increase, and the number of retired waste phosphate-based lithium-ion batteries has increased significantly. The large output and variety of waste phosphate-based lithium batteries lead to complex compositions and increased environmental pressure.

[0003] At present, there are three main methods for recycling waste lithium phosphate positive electrode materials: one is the wet process of recycling valuable metals from waste lithium phosphate; the second is the repair and regeneration of waste lithium phosphate; and the third is the decomposition and resynthesis of waste lithium phosphate. Lithium phosphate battery positive electrode materials contain not only a large amount of valuable metals (Fe, Co, Mn, Ni, Li), but also high value-added phosphorus. Therefore, how to recycle phosphorus and valuable metals in positive electrode materials has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0004] The object of the present invention is to provide a method for recycling waste phosphate lithium battery positive electrode materials. The recycling method provided by the present invention can recycle valuable metals and phosphorus in waste phosphate lithium battery positive electrode materials with high quality.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for recycling waste phosphate lithium battery positive electrode materials, comprising the following steps:

[0007] (1) Mixing the waste lithium phosphate battery positive electrode material with molten salt, performing a dissolution reaction, and then mixing with a solvent to obtain a mixed salt solution containing lithium ions and divalent metal ions and apatite precipitation; the molten salt includes a calcium salt;

[0008] (2) using the mixed salt solution containing lithium ions and divalent metal ions obtained in step (1) as an electrolyte to perform electrodeposition to obtain divalent metals and a lithium-containing solution in the positive electrode material of waste phosphate-based lithium batteries;

[0009] (3) mixing the lithium-containing solution obtained in step (2) with oxalic acid to perform a first precipitation reaction to obtain a calcium oxalate precipitate and a filtrate;

[0010] (4) The filtrate obtained in step (3) is mixed with phosphate to carry out a second precipitation reaction to obtain lithium phosphate.

[0011] Preferably, the cathode material of the waste phosphate-based lithium battery in step (1) is at least one of lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium nickel phosphate and lithium manganese iron phosphate.

[0012] Preferably, the molten salt in step (1) is calcium chloride, a mixture of calcium chloride and alkali metal chloride, or a mixture of calcium chloride and alkaline earth metal chloride.

[0013] Preferably, in step (1), the mass ratio of the waste phosphate-based lithium battery positive electrode material to the molten salt is 1:(2.4-20).

[0014] Preferably, the temperature of the dissolution reaction in step (1) is 750-850° C., and the time of the dissolution reaction is 3-6 hours.

[0015] Preferably, the electrodeposition in step (2) is constant current deposition, the electrodeposition current is 0.03-0.5 A, and the electrodeposition time is 3-5 h.

[0016] Preferably, in step (2), the cathode of the electrodeposition is a metal sheet, and the anode of the electrodeposition is an inert material.

[0017] Preferably, in step (3), the molar ratio of calcium ions to oxalic acid in the lithium-containing solution is 1:(1-1.4).

[0018] Preferably, the temperature of the first precipitation reaction in step (3) is 50-80° C., and the time of the first precipitation reaction is 0.5-2.5 h.

[0019] Preferably, the temperature of the second precipitation reaction in step (4) is 50-100° C., and the time of the second precipitation reaction is 1.5-3 h.

[0020] The invention provides a method for recovering positive electrode materials of waste lithium phosphate battery, comprising the following steps: mixing the positive electrode materials of waste lithium phosphate battery with molten salt, carrying out a dissolution reaction, and then mixing with a solvent to obtain a mixed salt solution containing lithium ions and divalent metal ions and apatite precipitate; the molten salt comprises a calcium salt; using the mixed salt solution containing lithium ions and divalent metal ions as an electrolyte, carrying out electrodeposition to obtain divalent metals in the positive electrode materials of waste lithium phosphate battery and a lithium-containing solution; mixing the lithium-containing solution with oxalic acid, carrying out a first precipitation reaction, obtaining calcium oxalate precipitate and a filtrate; mixing the filtrate with phosphate, carrying out a second precipitation reaction, and obtaining lithium phosphate. The present invention adopts a molten salt method to dissolve waste phosphate lithium battery positive electrode materials in molten salt, that is, the divalent metals and lithium in the positive electrode materials are dissolved in the molten salt in the form of ions, and the phosphate reacts with the molten salt to form apatite, and the phosphorus in the positive electrode materials is completely recovered; then the divalent metals in the positive electrode materials are precipitated by electrodeposition, and all are recovered; then the lithium-containing solution is reacted with oxalic acid to recover the calcium oxalate in the solution, and then reacted with phosphate to recover lithium; calcium salt is used as a molten salt to be removed by oxalic acid to avoid affecting the subsequent recovery of lithium; the present invention adopts a molten salt dissolution combined with an electrodeposition process to achieve the complete recovery of iron / nickel / cobalt / manganese, lithium and phosphate ions in waste phosphate lithium positive electrode materials, and finally obtains the product metal iron / nickel / cobalt / manganese, apatite and lithium salt, and the product has high added value and good process efficiency. Experimental results show that the recovery method of waste phosphate lithium battery positive electrode materials provided by the present invention can obtain nickel element, iron element, cobalt element, chloroapatite and lithium phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic flow chart of a method for recycling positive electrode materials of waste phosphate-based lithium batteries;

[0022] Figure 2 This is a SEM image of the iron element prepared in Example 1;

[0023] Figure 3 This is the XRD spectrum of the iron element prepared in Example 1;

[0024] Figure 4 This is the SEM image of the chlorapatite prepared in Example 1;

[0025] Figure 5 This is the XRD spectrum of the chlorapatite prepared in Example 1;

[0026] Figure 6 This is a SEM image of the lithium phosphate prepared in Example 1;

[0027] Figure 7 This is the XRD spectrum of the lithium phosphate prepared in Example 1;

[0028] Figure 8 This is a SEM image of the nickel element prepared in Example 2;

[0029] Fig. 9 The XRD spectrum of the nickel element prepared in Example 2;

[0030] Fig.10 This is a SEM image of the cobalt single substance prepared in Example 3;

[0031] Fig.11 This is the XRD spectrum of the cobalt element prepared in Example 3. DETAILED DESCRIPTION

[0032] The present invention provides a method for recycling waste phosphate lithium battery positive electrode materials, comprising the following steps:

[0033] (1) Mixing the waste lithium phosphate battery positive electrode material with molten salt, performing a dissolution reaction, and then mixing with a solvent to obtain a mixed salt solution containing lithium ions and divalent metal ions and apatite precipitation; the molten salt includes a calcium salt;

[0034] (2) using the mixed salt solution containing lithium ions and divalent metal ions obtained in step (1) as an electrolyte to perform electrodeposition to obtain divalent metals and a lithium-containing solution in the positive electrode material of waste phosphate-based lithium batteries;

[0035] (3) mixing the lithium-containing solution obtained in step (2) with oxalic acid to perform a first precipitation reaction to obtain a calcium oxalate precipitate and a filtrate;

[0036] (4) The filtrate obtained in step (3) is mixed with phosphate to carry out a second precipitation reaction to obtain lithium phosphate.

[0037] The present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0038] In the present invention, the first and the second have no special meanings and are only used to distinguish the steps.

[0039] The present invention mixes the waste phosphate lithium battery positive electrode material with molten salt, performs a dissolution reaction, and then mixes with a solvent to obtain a mixed salt solution containing lithium ions and divalent metal ions and apatite precipitation. The present invention adopts a molten salt method to cause a dissolution reaction of the waste phosphate lithium battery positive electrode material in the molten salt, that is, the divalent metal and lithium in the positive electrode material are dissolved in the molten salt in the form of ions, and the phosphate reacts with the molten salt to generate apatite, and the phosphorus in the positive electrode material is separated from the valuable metal, thereby achieving full recovery.

[0040] In the present invention, the method for preparing the positive electrode material of the waste lithium phosphate battery is preferably to roast the positive electrode sheet of the waste lithium phosphate battery, then cool it, and then remove the foil to obtain the positive electrode material of the waste lithium phosphate battery.

[0041] In the present invention, the calcination temperature is preferably 400-500° C., more preferably 450° C.; the calcination time is preferably 1-3 h, more preferably 2 h; and the calcination is preferably performed in an argon atmosphere.

[0042] The present invention has no particular limitation on the cooling operation, and cooling to room temperature is sufficient.

[0043] The present invention has no special limitation on the operation of removing the foil, and operations well known to those skilled in the art may be adopted.

[0044] In the present invention, the waste phosphate lithium battery positive electrode material is preferably dried before use; the drying temperature is preferably 250-550°C, more preferably 300-450°C; the drying time is preferably 12-24h, more preferably 15-20h. The present invention can remove moisture by drying the waste phosphate lithium battery positive electrode material.

[0045] In the present invention, the molten salt is preferably dried before use; the drying temperature is preferably 250-550° C., more preferably 300-450° C.; the drying time is preferably 12-24 hours, more preferably 15-20 hours. The present invention can remove moisture by drying the molten salt.

[0046] In the present invention, the cathode material of the waste phosphate-based lithium battery is preferably at least one of lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium nickel phosphate and lithium manganese iron phosphate.

[0047] In the present invention, the molten salt is preferably calcium chloride, a mixture of calcium chloride and alkali metal chloride, or a mixture of calcium chloride and alkaline earth metal chloride, more preferably calcium chloride or a mixture of calcium chloride and sodium chloride. In the present invention, the molten salt is used to dissolve the valuable metals in the positive electrode material of the waste phosphoric acid lithium battery at high temperature, and separate the valuable metals from phosphorus; the chloride ions contained in the molten salt can form chloroapatite with the phosphorus in the positive electrode material of the waste phosphoric acid lithium battery, and the added calcium ions can also be removed by forming a precipitate with oxalic acid.

[0048] In the present invention, the molar ratio of calcium chloride to sodium chloride in the mixture of calcium chloride and sodium chloride is preferably 1:(0.1-1), more preferably 1:(0.5-1).

[0049] In the present invention, the mass ratio of the waste phosphate-based lithium battery positive electrode material to the molten salt is preferably 1: (2.4-20), more preferably 1: (5-20), and more preferably 1: (15-20). The present invention can ensure effective separation of valuable metals and phosphorus by limiting the mass ratio of the waste phosphate-based lithium battery positive electrode material to the molten salt within the above range.

[0050] The present invention has no special limitation on the operation of mixing the waste phosphate-based lithium battery positive electrode material with the molten salt. The two can be mixed evenly using a technical solution for preparing a mixed material well known to those skilled in the art.

[0051] In the present invention, the temperature of the dissolution reaction is preferably 750-850°C, more preferably 750-800°C; the time of the dissolution reaction is preferably 3-6 hours, more preferably 4-5 hours. The present invention limits the temperature and time of the dissolution reaction within the above range to further improve the degree of the dissolution reaction.

[0052] In the present invention, the rate of heating to the dissolution reaction temperature is preferably 3-15°C / min, more preferably 5-10°C / min.

[0053] In the present invention, the dissolution reaction is preferably carried out in an inert atmosphere; the inert atmosphere is preferably argon. Carrying out the dissolution reaction in an inert atmosphere can prevent oxidation of the positive electrode material during the temperature rise process.

[0054] After the dissolution reaction is completed, the product obtained by the dissolution reaction is preferably cooled. The cooling operation is not particularly limited in the present invention, and the operation well known to those skilled in the art can be adopted.

[0055] In the present invention, the solvent is preferably distilled water. The present invention has no particular limitation on the amount of the solvent, as long as the molten salt containing lithium ions and divalent metal ions obtained by the dissolution reaction is completely dissolved.

[0056] After the mixture is mixed with the solvent, the present invention preferably filters the mixed product to obtain a mixed salt solution containing lithium ions and divalent metal ions and an apatite precipitate.

[0057] The present invention has no particular limitation on the filtering operation, and any operation well known to those skilled in the art may be used.

[0058] After obtaining a mixed salt solution containing lithium ions and divalent metal ions, the present invention uses the mixed salt solution containing lithium ions and divalent metal ions as an electrolyte to perform electrodeposition to obtain divalent metals and a lithium-containing solution in the positive electrode material of waste phosphate-based lithium batteries. The present invention utilizes electrodeposition to precipitate the divalent metals in the positive electrode material from the cathode and fully recover them.

[0059] In the present invention, the electrodeposition is preferably constant current deposition; the current of the electrodeposition is preferably 0.03-0.5A, more preferably 0.07-0.1A; the time of the electrodeposition is preferably 3-5h, more preferably 4-5h. The present invention can improve the separation degree of divalent metal and lithium in the positive electrode material by limiting the current and time of the electrodeposition within the above range, thereby improving the purity.

[0060] In the present invention, the cathode of the electrodeposition is preferably a metal sheet; the metal sheet is preferably a nickel sheet, a molybdenum sheet or a tungsten sheet; the anode of the electrodeposition is preferably an inert material; the inert electrode is preferably a glassy carbon electrode, a graphite electrode or a platinum electrode. The present invention has no special restrictions on the sizes of the cathode and anode of the electrodeposition, and operations familiar to those skilled in the art can be used.

[0061] After the electrodeposition is completed, the present invention preferably sequentially cleans and dries the cathode in the electrodeposition to obtain the divalent metal in the positive electrode material of the waste phosphate-based lithium battery.

[0062] The present invention has no special limitation on the cleaning operation, as long as the salt on the cathode surface is completely removed.

[0063] The present invention has no particular limitation on the drying operation, and the drying operation may be performed until the weight is constant.

[0064] After obtaining the lithium-containing solution, the present invention mixes the lithium-containing solution with oxalic acid to perform a first precipitation reaction to obtain calcium oxalate precipitate and filtrate. The present invention uses oxalic acid to remove calcium ions in the lithium-containing solution to avoid affecting the subsequent recovery of lithium.

[0065] In the present invention, the molar ratio of calcium ions to oxalic acid in the lithium-containing solution is preferably 1: (1-1.4), more preferably (1.1-1.2): 1. In the present invention, limiting the molar ratio of calcium ions to oxalic acid in the lithium-containing solution to the above range can further remove calcium ions in the lithium-containing solution, thereby improving the purity of the subsequent lithium salt.

[0066] In the present invention, the mixing of the lithium-containing solution and oxalic acid is preferably carried out under stirring conditions; the stirring speed is preferably 100-200 r / min. The present invention has no particular limitation on the stirring time, as long as the raw materials are mixed uniformly.

[0067] In the present invention, the temperature of the first precipitation reaction is preferably 50-80°C, more preferably 70-75°C; the time of the first precipitation reaction is preferably 0.5-2.5h, more preferably 1.5-2h. In the present invention, limiting the temperature and time of the first precipitation reaction within the above range can further remove calcium ions in the lithium-containing solution, thereby improving the purity of the subsequent lithium salt.

[0068] After the first precipitation reaction is completed, the present invention preferably filters the product obtained from the first precipitation reaction to obtain calcium oxalate precipitate and filtrate.

[0069] The present invention has no particular limitation on the filtering operation, and the separation can be performed by using operations well known to those skilled in the art.

[0070] After obtaining the filtrate, the present invention mixes the filtrate with phosphate to perform a second precipitation reaction to obtain lithium phosphate.

[0071] In the present invention, the phosphate is preferably sodium phosphate; the molar ratio of the phosphate to the lithium salt in the filtrate is preferably 3:(1-5), more preferably 3:(2-4), and more preferably 3:3.

[0072] In the present invention, the mixing of the filtrate and the phosphate is preferably carried out under stirring conditions; the stirring speed is preferably 100-300 r / min. The present invention has no particular limitation on the stirring time, as long as the raw materials are mixed uniformly.

[0073] In the present invention, the temperature of the second precipitation reaction is preferably 50-100°C, more preferably 60-80°C, and more preferably 70-75°C; the time of the second precipitation reaction is preferably 1.5-3h, and more preferably 2-2.5h. The present invention limits the temperature and time of the second precipitation reaction within the above ranges to further improve the recovery rate of lithium.

[0074] After the second precipitation reaction is completed, the present invention preferably filters and dries the product obtained by the second precipitation reaction in sequence to obtain a lithium salt.

[0075] The present invention has no particular limitation on the filtering operation, and any operation well known to those skilled in the art may be used.

[0076] The present invention has no particular limitation on the drying operation, and the product may be dried to a constant weight.

[0077] The present invention adopts a molten salt method to cause a dissolution reaction of waste phosphate-based lithium battery positive electrode materials in molten salt, that is, divalent metals and lithium in the positive electrode materials are dissolved in the molten salt in the form of ions, and phosphate reacts with the molten salt to generate apatite, so that all phosphorus in the positive electrode materials is recovered; then, the divalent metals in the positive electrode materials are precipitated by electrodeposition, and all are recovered; then, the lithium-containing solution is reacted with oxalic acid to recover calcium oxalate in the solution, and then reacted with phosphate to recover lithium; the present invention adopts a process of molten salt dissolution combined with constant current electrodeposition to achieve full recovery of iron / nickel / cobalt / manganese, lithium and phosphate ions in waste phosphate-based lithium positive electrode materials, and finally obtains products of metallic iron / nickel / cobalt / manganese, apatite and lithium salt, and the products have high added value and good process efficiency.

[0078] The recovery method provided by the present invention can realize the efficient and high-quality recovery of all valuable components in the phosphate-based lithium positive electrode material, so as to facilitate large-scale production.

[0079] The process equipment and device adopted by the present invention are simple, the process flow is short, the recovery process is easy to control, and the electrolyte solution used in the constant current electrodeposition is non-toxic and harmless, which greatly reduces the harm to operators and equipment and the impact of pollutant emissions on the environment.

[0080] The schematic flow diagram of the method for recycling the positive electrode material of waste phosphate-based lithium batteries of the present invention is as follows: Figure 1 shown.

[0081] from Figure 1 It can be seen that the waste lithium phosphate battery positive electrode sheet is separated and processed to obtain the lithium phosphate battery positive electrode material, and then dissolved in molten salt to obtain Fe 2+ / Ni 2+ / Co 2+ , Li + of molten salt and chlorapatite; then dissolution and filtration treatment is carried out to obtain chlorapatite, followed by electrodeposition to obtain metallic iron / nickel / cobalt, and then two-step precipitation is carried out to obtain lithium salt.

[0082] The invention has simple operation steps, and valuable metals can be separated and recovered with a high recovery rate, and is suitable for large-scale industrial recovery production.

[0083] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0084] The test reagents used in the examples are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0085] Example 1

[0086] The recycling method of waste phosphate lithium battery positive electrode material is as follows:

[0087] (1) Cut the lithium iron phosphate battery positive electrode foil into 5 cm × 4 cm, put it into a corundum crucible, put it into a tubular resistance furnace and heat it at 450 ° C for 2 hours, and pass argon protection. After the tubular resistance furnace is cooled to room temperature, take out the crucible and use a medicine spoon to scrape the positive electrode material from the aluminum foil to obtain the lithium iron phosphate positive electrode material;

[0088] (2) 10 g of the lithium iron phosphate positive electrode material obtained in step (1) and 200 g of the molten salt are dried at 300° C. for 20 h under argon protection, mixed evenly, and then loaded into a corundum crucible, placed in a tubular resistance furnace, and heated to 800° C. at a rate of 5° C. / min under argon protection for 5 h. After cooling, the mixture is dissolved in distilled water and filtered to obtain a filter residue and a filtrate, wherein the filter residue is chlorapatite and the filtrate is Fe-containing 2+ and Li + The molten salt is a mixture of sodium chloride and calcium chloride, and the molar ratio of the two is 1:1;

[0089] (3) Using the nickel sheet as the cathode and the glassy carbon electrode as the anode, insert the Fe-containing 2+ and Li + The solution was electro-deposited at a constant current of 0.5A for 5 hours, and then the cathode was taken out for cleaning and drying to obtain a deposition product and a lithium-containing solution; wherein the deposition product was a single substance of metallic iron with a purity of 99.73% and a recovery rate of 99.32%;

[0090] (4) adding oxalic acid to the lithium-containing solution obtained in step (3), carrying out precipitation reaction at a stirring speed of 200 r / min and a temperature of 70° C. for 1.5 h, filtering to obtain a filtrate and a CaC2O4 precipitate, and the calcium removal rate reaches 99.72%; wherein the molar ratio of oxalic acid to calcium ions in the lithium-containing solution is 1.2:1;

[0091] (5) Na3PO4 was added to the filtrate obtained in step (4), and a precipitation reaction was carried out at a stirring rate of 200 r / min and a temperature of 70°C for 2 h. After filtering and drying, Li3PO4 precipitate was obtained, and the lithium recovery rate was 98.29%; wherein the molar ratio of Na3PO4 to the lithium salt in the filtrate was 1:1.

[0092] The iron, chloroapatite and lithium phosphate prepared in Example 1 were tested, and the results were as follows: Figures 2 to 7 As shown. Among them, Figure 2 This is a SEM image of the iron element prepared in Example 1; Figure 3 This is the XRD spectrum of the iron element prepared in Example 1; Figure 4 This is the SEM image of the chlorapatite prepared in Example 1; Figure 5 This is the XRD spectrum of the chlorapatite prepared in Example 1; Figure 6 This is a SEM image of the lithium phosphate prepared in Example 1; Figure 7 This is the XRD spectrum of the lithium phosphate prepared in Example 1.

[0093] from Figures 2 to 7It can be seen that effective separation and extraction of waste lithium iron phosphate battery positive electrode materials can obtain iron, chloroapatite and lithium phosphate.

[0094] Example 2

[0095] The recycling method of waste phosphate lithium battery positive electrode material is as follows:

[0096] (1) A nickel phosphate lithium battery positive electrode foil cut into 5 cm × 4 cm was placed in a corundum crucible, placed in a tubular resistance furnace and heated at 450 ° C for 2 h, and argon gas was introduced for protection. After the tubular resistance furnace was cooled to room temperature, the crucible was taken out and the positive electrode material was scraped off the aluminum foil with a medicine spoon to obtain a nickel phosphate lithium positive electrode material;

[0097] (2) 10 g of the lithium nickel phosphate positive electrode material obtained in step (1) and 200 g of the molten salt are dried at 350° C. under argon protection for 16 h, mixed evenly, and then loaded into a corundum crucible, placed in a tubular resistance furnace, and heated to 750° C. at a rate of 5° C. / min under argon protection for 6 h, then cooled, dissolved in distilled water, and filtered to obtain a filter residue and a filtrate, wherein the filter residue is chlorapatite and the filtrate is Ni-containing 2+ and Li + The molten salt is a mixture of sodium chloride and calcium chloride, and the molar ratio of the two is 1:1;

[0098] (3) Using the molybdenum sheet as the cathode and the glassy carbon electrode as the anode, insert the Ni-containing 2+ and Li + The electrodeposition was carried out for 4 hours at a constant current of 0.03A in a solution, and then the cathode was taken out for cleaning and drying to obtain a deposition product and a lithium-containing solution; wherein the deposition product was a single substance of metallic nickel with a purity of 99.58% and a recovery rate of 99.65%;

[0099] (4) adding oxalic acid to the lithium-containing solution obtained in step (3), carrying out precipitation reaction at a stirring speed of 200 r / min and a temperature of 70° C. for 2 h, filtering to obtain a filtrate and a CaC2O4 precipitate, and the calcium removal rate reaches 99.68%; wherein the molar ratio of oxalic acid to calcium ions in the lithium-containing solution is 1.1:1;

[0100] (5) Na3PO4 was added to the filtrate obtained in step (4), and a precipitation reaction was carried out at a stirring rate of 200 r / min and a temperature of 75°C for 2 h. After filtering and drying, Li3PO4 precipitate was obtained, and the lithium recovery rate was 98.37%; wherein the molar ratio of Na3PO4 to the lithium salt in the filtrate was 1:1.

[0101] The nickel element prepared in Example 2 was tested, and the results were as follows: Figure 8 and9 As shown. Among them, Figure 8 This is a SEM image of the nickel element prepared in Example 2; Fig. 9 This is the XRD spectrum of the nickel element prepared in Example 2.

[0102] from Figures 8 and 9 It can be seen that nickel can be obtained by effectively separating and extracting the positive electrode materials of waste nickel phosphate lithium batteries.

[0103] Example 3

[0104] The recycling method of waste phosphate lithium battery positive electrode material is as follows:

[0105] (1) A lithium cobalt phosphate battery positive electrode foil cut into 5 cm × 4 cm was placed in a corundum crucible, placed in a tubular resistance furnace and heated at 450 ° C for 2 h, and argon gas was introduced for protection. After the tubular resistance furnace was cooled to room temperature, the crucible was taken out and the positive electrode material was scraped off the aluminum foil with a medicine spoon to obtain a lithium cobalt phosphate positive electrode material;

[0106] (2) 10 g of the lithium cobalt phosphate positive electrode material obtained in step (1) and 200 g of the molten salt were dried at 350° C. under argon protection for 16 h, mixed evenly, and then loaded into a corundum crucible, placed in a tubular resistance furnace, and heated to 750° C. at a rate of 10° C. / min under argon protection for 5 h, then cooled, dissolved in distilled water, and filtered to obtain a filter residue and a filtrate, wherein the filter residue is chloroapatite and the filtrate is Co-containing 2+ and Li + The molten salt is a mixture of sodium chloride and calcium chloride, and the molar ratio of the two is 1:1;

[0107] (3) Using the molybdenum sheet as the cathode and the glassy carbon electrode as the anode, insert the Co-containing 2+ and Li + The electrodeposition was carried out for 5 hours at a constant current of 0.07A in a solution, and then the cathode was taken out for cleaning and drying to obtain a deposition product and a lithium-containing solution; wherein the deposition product was a single substance of metallic cobalt with a purity of 99.49% and a recovery rate of 98.57%;

[0108] (4) adding oxalic acid to the lithium-containing solution obtained in step (3), carrying out precipitation reaction at a stirring speed of 200 r / min and a temperature of 75° C. for 2 h, filtering to obtain a filtrate and a CaC2O4 precipitate, and the calcium removal rate reaches 99.84%; wherein the molar ratio of oxalic acid to calcium ions in the lithium-containing solution is 1.2:1;

[0109] (5) Na3PO4 was added to the filtrate obtained in step (4), and a precipitation reaction was carried out at a stirring rate of 200 r / min and a temperature of 80°C for 2 h. After filtering and drying, Li3PO4 precipitate was obtained, and the lithium recovery rate was 98.42%; wherein the molar ratio of Na3PO4 to the lithium salt in the filtrate was 1:1.

[0110] The cobalt element prepared in Example 3 was tested, and the results were as follows: Fig.10 and 11 As shown. Among them, Fig.10 This is a SEM image of the cobalt single substance prepared in Example 3; Fig.11 This is the XRD spectrum of the cobalt element prepared in Example 3.

[0111] from Figures 10-11 It can be seen that cobalt element can be obtained by effectively separating and extracting the positive electrode materials of waste cobalt phosphate lithium batteries.

[0112] It can be seen from the above examples that the recycling method provided by the present invention can separate and recover valuable components such as phosphorus, lithium and iron / cobalt / nickel / manganese in the positive electrode materials of waste lithium phosphate batteries.

[0113] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recycling waste phosphate lithium battery positive electrode materials, characterized in that: For the following steps: (1) Mixing the waste lithium phosphate battery positive electrode material with molten salt to carry out a dissolution reaction, cooling the product obtained by the dissolution reaction, and then mixing it with a solvent, filtering the mixed product to obtain a mixed salt solution containing lithium ions and divalent metal ions and apatite precipitate; the waste lithium phosphate battery positive electrode material is dried before use; the molten salt is dried before use; (2) using the mixed salt solution containing lithium ions and divalent metal ions obtained in step (1) as an electrolyte to carry out electrodeposition, and sequentially cleaning and drying the cathode in the electrodeposition to obtain the divalent metal and lithium-containing solution in the positive electrode material of the waste lithium phosphate battery; (3) mixing the lithium-containing solution obtained in step (2) with oxalic acid to perform a first precipitation reaction, and filtering the product obtained by the first precipitation reaction to obtain a calcium oxalate precipitate and a filtrate; (4) mixing the filtrate obtained in step (3) with phosphate to carry out a second precipitation reaction, and filtering and drying the product obtained by the second precipitation reaction in sequence to obtain lithium phosphate; The cathode material of the waste lithium phosphate battery in step (1) is at least one of lithium iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium nickel phosphate and lithium manganese iron phosphate; The molten salt in step (1) is calcium chloride, a mixture of calcium chloride and alkali metal chloride, or a mixture of calcium chloride and alkaline earth metal chloride.

2. The recycling method according to claim 1, characterized in that: In the step (1), the mass ratio of the waste phosphate-based lithium battery positive electrode material to the molten salt is 1:(2.4-20).

3. The recycling method according to claim 1, characterized in that: The temperature of the dissolution reaction in step (1) is 750-850° C., and the time of the dissolution reaction is 3-6 hours.

4. The recycling method according to claim 1, characterized in that: The electrodeposition in step (2) is constant current deposition, the electrodeposition current is 0.03-0.5A, and the electrodeposition time is 3-5h.

5. The recycling method according to claim 1, characterized in that: In the step (2), the cathode of the electrodeposition is a metal sheet, and the anode of the electrodeposition is an inert material.

6. The recycling method according to claim 1, characterized in that: In the step (3), the molar ratio of calcium ions to oxalic acid in the lithium-containing solution is 1:(1-1.4).

7. The recycling method according to claim 1, characterized in that: The temperature of the first precipitation reaction in step (3) is 50-80° C., and the time of the first precipitation reaction is 0.5-2.5 h.

8. The recycling method according to claim 1, characterized in that: The temperature of the second precipitation reaction in step (4) is 50-100° C., and the time of the second precipitation reaction is 1.5-3 h.

Images