System for electrochemically recovering phosphate positive electrode material

Abstract

The utility model provides a system for electrochemically recovering phosphate anode materials, which comprises a leaching kettle, a first filter press, a lithium precipitation kettle, a second filter press, a cleaning kettle, a filtering and drying device, an evaporation and concentration device, an electrochemical reactor, a first pushed slab kiln and a second pushed slab kiln, the second filter press is communicated with the lithium precipitation kettle and the cleaning kettle, the filtering and drying device is communicated with the cleaning kettle, the evaporation and concentration device is communicated with the second filter press, the electrochemical reactor is communicated with the evaporation and concentration device, the electrochemical reactor performs an electrochemical reaction, and a solution obtained after the electrochemical reaction is circularly fed into the leaching kettle; the first pushed slab kiln is communicated with a first filter press; and the second pushed slab kiln is communicated with the first pushed slab kiln and the filtering and drying device. According to the utility model, closed-loop recovery of the lithium element is realized, and the generated chlorine-containing wastewater can be returned to the front end for cyclic utilization through an electro-catalysis process, so that electrochemical cyclic utilization of a leaching agent is realized, and the production cost is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium - ion batteries, and more specifically, to a system for electrochemically recycling phosphate - based cathode materials. Background Art

[0002] With the increasing prominence of new energy and environmental problems, the new energy vehicle and energy storage markets have shown an explosive growth trend. Lithium iron phosphate (LFP) batteries account for 70% of the new energy vehicle market due to their high energy density, long cycle life, and high safety and stability. Generally, the service life of lithium iron phosphate batteries is 3 - 10 years, and the next few years will be the peak period for the retirement of lithium iron phosphate batteries. If a large number of waste lithium iron phosphate batteries are not recycled, it will not only cause serious environmental pollution but also result in waste of resources.

[0003] The existing recycling of lithium iron phosphate cathode materials only uses hypochlorite for weak - base oxidation selective leaching in the process, but there are still the following problems:

[0004] 1. In the wet - process recycling process, by - products (such as chlorides) generated cannot be effectively recycled and cannot be utilized with high value.

[0005] 2. In wet - process leaching, the pH of the leaching solution is generally between 0 and 2, and a large amount of waste water and waste salts will be generated during the lithium precipitation process, increasing production costs.

[0006] 3. In the wet - process recycling process, a very small amount of lithium will inevitably be entrained in the waste water, and this part of lithium loss is inevitable. Summary of the Utility Model

[0007] In view of the above - mentioned problems existing in the prior art, the purpose of the present utility model is to provide a system for electrochemically recycling phosphate - based cathode materials. By reacting hypochlorite with phosphate - based cathode materials, a lithium - containing solution and metal phosphate residues are obtained. The lithium - containing solution undergoes a carbonation reaction to obtain lithium carbonate and chlorine - containing waste water. The metal phosphate residues undergo a high - temperature solid - state reaction to obtain battery - grade phosphate precursors. Lithium carbonate and metal phosphate residues undergo a solid - state reaction to regenerate battery - grade lithium iron phosphate, realizing the closed - loop recycling of lithium elements. The generated chlorine - containing waste water undergoes a bipolar membrane electrocatalytic process to generate new hypochlorite, which can be recycled to the front end, realizing the high - value recycling of waste water, realizing the electrochemical recycling of leaching agents, and saving production costs.

[0008] The technical solution adopted by the present utility model is to provide a system for electrochemically recycling phosphate - based cathode materials, including:

[0009] A leaching kettle for receiving phosphate - based cathode waste and hypochlorite solution and accommodating the reaction of the phosphate - based cathode waste and hypochlorite solution;

[0010] The first filter press is connected to the leaching kettle, receives and separates the lithium-containing solution and metal phosphate residue from the leaching kettle;

[0011] The lithium precipitation kettle is connected to the first filter press, receives the lithium-containing solution separated from the first filter press, receives the lithium precipitant, and accommodates the reaction of the lithium-containing solution and the lithium precipitant;

[0012] The second filter press is connected to the lithium precipitation kettle, receives and separates lithium carbonate and chlorine-containing wastewater from the lithium precipitation kettle;

[0013] The cleaning kettle is connected to the second filter press, receives and cleans the lithium carbonate from the second filter press;

[0014] The filtration and drying device is connected to the cleaning kettle, receives and filters and dries the lithium carbonate from the cleaning kettle;

[0015] The evaporation and concentration device is connected to the second filter press, receives and evaporates and concentrates the chlorine-containing wastewater from the second filter press;

[0016] The electro-chemical reactor is connected to the evaporation and concentration device, receives the chlorine-containing wastewater from the evaporation and concentration device, accommodates the electro-chemical reaction of the chlorine-containing wastewater, and circulates the hypochlorite solution obtained after the electro-chemical reaction into the leaching kettle;

[0017] The first pusher kiln is connected to the first filter press, receives the metal phosphate residue from the first filter press, and calcines the metal phosphate at high temperature;

[0018] The second pusher kiln is connected to the first pusher kiln and the filtration and drying device, receives the battery-grade phosphate precursor from the first pusher kiln and the battery-grade lithium carbonate from the filtration and drying device, and accommodates the reaction of the battery-grade phosphate precursor and the battery-grade lithium carbonate.

[0019] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: By using inexpensive hypochlorite as an oxidant to oxidize waste phosphate cathode materials, battery-grade iron phosphate and battery-grade carbonate are extracted. Finally, phosphate products can be regenerated through solid-phase reaction, realizing the closed-loop regeneration of battery-grade phosphate products; lithium cations exist in the chlorine-containing wastewater, and the anion is chlorine. The chlorine-containing wastewater can generate new hypochlorite through electrocatalytic reaction, which can be returned to the leaching kettle for recycling, realizing the high-value recovery of wastewater, the electrochemical recycling of the leaching agent. And during the process that the chlorine-containing wastewater generates hypochlorite through multiple electrocatalytic reactions in the bipolar membrane electrochemical reactor, a very small amount of lithium is enriched in the hypochlorite each time and is recycled to the leaching kettle with the hypochlorite. When the recycled hypochlorite reacts with a new batch of waste phosphate cathode materials, the very small amount of lithium enriched in the hypochlorite also participates in the reaction again because it is mixed with the waste phosphate cathode materials, increasing the lithium concentration, thereby increasing the total recovery rate of lithium elements and realizing the closed-loop recovery of lithium elements.

[0020] In an alternative embodiment, the filtration and drying device includes a third filter press and a tray dryer. The third filter press is connected to the cleaning kettle to receive and separate lithium carbonate and cleaning waste liquid after cleaning from the cleaning kettle. The tray dryer is connected to the third filter press to receive and dry the lithium carbonate obtained from the third filter press.

[0021] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The setting of the third filter press enables the recycling of the cleaning waste liquid after solid-liquid separation by the third filter press. The tray dryer is used to dry the lithium carbonate after passing through the third filter press to obtain battery-grade lithium carbonate.

[0022] In an alternative embodiment, the system further includes a reverse osmosis membrane, which is connected to the third filter press to receive and process the cleaning waste liquid from the third filter press, and sends the deionized water obtained through the pipeline to the cleaning kettle.

[0023] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The setting of the reverse osmosis membrane enables the cleaning waste liquid after solid-liquid separation by the third filter press to provide deionized water for the cleaning kettle after passing through the reverse osmosis membrane.

[0024] In an alternative embodiment, the system further includes a batch mixer, which is connected to the first pusher kiln and the tray dryer to receive and mix the phosphate precursor obtained from the first pusher kiln and the lithium carbonate obtained from the tray dryer, and sends the mixed material to the second pusher kiln through a pipeline.

[0025] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The batch mixer can stir and mix the battery-grade lithium carbonate and the battery-grade iron phosphate precursor, and then enter the second pusher kiln for high-temperature calcination, so that the lithium carbonate and the iron phosphate precursor entering the second pusher kiln can fully react to regenerate the battery-grade lithium iron phosphate cathode material.

[0026] In an alternative embodiment, the electrochemical reactor is a bipolar membrane electrochemical reactor. The bipolar membrane electrochemical reactor is a continuous flow pipeline. A plurality of electrodes are embedded on the inner wall of the continuous flow pipeline. A bipolar membrane is arranged in the middle of the continuous flow pipeline. The bipolar membrane isolates the bipolar membrane electrochemical reactor into a separate anode chamber and a cathode chamber.

[0027] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The electrochemical reactor is set as a bipolar membrane, which can greatly reduce the internal resistance. And the bipolar membrane electrochemical reactor is set as a continuous flow pipeline, which can realize continuous electrochemical reactions at high current density, has excellent hydrolysis dissociation performance and long-term use stability. The anode chamber of the bipolar membrane electrochemical reactor undergoes an electrocatalytic reaction to generate new hypochlorite in the chlorine-containing wastewater and returns it to the front end for recycling, realizing the high-value recovery of wastewater, realizing the electrochemical recycling of the leaching agent, and saving the production cost.

[0028] In an alternative embodiment, the cathode chamber is connected to the first pusher kiln through a pipeline. The hydrogen gas obtained by the reaction in the cathode chamber enters the first pusher kiln through the pipeline as a reducing atmosphere. Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The cathode chamber of the bipolar membrane electrochemical reactor generates hydrogen gas through an electrocatalytic reaction, which is used as the reducing atmosphere of the first pusher kiln for the generation of battery-grade iron phosphate from phosphorus iron residues, realizing the recycling of hydrogen gas generated by the electrocatalytic reaction and saving the production cost.

[0029] The beneficial effects of the embodiments of the present invention are as follows: A lithium-containing solution and metal phosphate residues are obtained by reacting hypochlorite with phosphate-based cathode waste. The lithium-containing solution undergoes a carbonation reaction to obtain lithium carbonate and chlorine-containing wastewater. The metal phosphate residues are processed into battery-grade phosphate precursors through a high-temperature solid-phase reaction. Lithium carbonate and metal phosphate residues are regenerated into battery-grade phosphate products through a solid-phase reaction, realizing the closed-loop recovery of lithium elements. The generated chlorine-containing wastewater undergoes a bipolar membrane electrocatalytic process to generate new hypochlorite, which can be returned to the front end for recycling, realizing the high-value recovery of wastewater, realizing the electrochemical recycling of the leaching agent, and saving the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Shows a schematic diagram of a system for electrochemically recovering phosphate-based cathode materials provided by an embodiment of the present invention;

[0031] Figure 2 shows a schematic diagram of the bipolar membrane electrochemical reactor according to an embodiment of the present utility model;

[0032] Figure 3 shows a schematic flow diagram of a system for electrochemically recovering phosphate-based cathode materials provided by an embodiment of the present utility model;

[0033] Figure 4 shows a schematic diagram of a system for electrochemically recovering phosphate-based cathode materials provided by an embodiment of the present utility model.

[0034] Description of reference numerals:

[0035] 1 - leaching kettle; 2 - lithium precipitation kettle; 3 - bipolar membrane electrochemical reactor; 31 - anodic chamber; 32 - cathodic chamber; 4 - cleaning kettle; 5 - first filter press; 6 - second filter press; 7 - third filter press; 8 - first pusher kiln; 9 - second pusher kiln; 10 - reverse osmosis membrane; 11 - tray dryer; 12 - batch mixer; 13 - evaporation and concentration device. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Usually, the components of the embodiments of the present utility model described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the claimed present utility model, but merely represents the selected embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present utility model.

[0038] It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0039] Refer to the attached Figure 1 As shown, the present utility model provides a system for electrochemically recycling phosphate-based cathode materials, including:

[0040] Leaching autoclave 1, used to receive phosphate-based cathode waste and hypochlorite solution, and accommodate the reaction of the phosphate-based cathode waste and hypochlorite solution;

[0041] The first filter press 5 is connected to the leaching autoclave 1 to receive and separate the lithium-containing solution and metal phosphate residue from the leaching autoclave 1;

[0042] Lithium precipitation autoclave 2 is connected to the first filter press 5 to receive the lithium-containing solution separated from the first filter press 5, receive a lithium precipitant, and accommodate the reaction of the lithium-containing solution and the lithium precipitant;

[0043] The second filter press 6 is connected to the lithium precipitation autoclave 2 to receive and separate lithium carbonate and chlorine-containing wastewater from the lithium precipitation autoclave 2;

[0044] Washing autoclave 4 is connected to the second filter press 6 to receive and wash the lithium carbonate from the second filter press 6;

[0045] Filtering and drying device, connected to the washing autoclave 4, to receive, filter, and dry the lithium carbonate from the washing autoclave 4;

[0046] Evaporation and concentration device 13, connected to the second filter press 6, to receive and evaporate and concentrate the chlorine-containing wastewater from the second filter press 6;

[0047] Electrochemical reactor 3, connected to the evaporation and concentration device 13, to receive the chlorine-containing wastewater from the evaporation and concentration device 13, accommodate the electrochemical reaction of the chlorine-containing wastewater, and recycle the hypochlorite solution obtained after the electrochemical reaction into the leaching autoclave 1;

[0048] The first pusher kiln 8 is connected to the first filter press 5 to receive the metal phosphate residue from the first filter press 5 and calcine the metal phosphate at high temperature;

[0049] The second pusher kiln 9 is connected to the first pusher kiln 8 and the filtering and drying device, to receive the battery-grade phosphate precursor from the first pusher kiln 8 and the battery-grade lithium carbonate from the filtering and drying device, and accommodate the reaction of the battery-grade phosphate precursor and the battery-grade lithium carbonate.

[0050] Optionally, the phosphate-based cathode waste can be lithium iron phosphate cathode waste, and the hypochlorite solution is sodium hypochlorite solution.

[0051] Specifically, the lithium iron phosphate cathode waste and the sodium hypochlorite solution are mixed and reacted in the leaching kettle 1. After the reaction, they enter the first filter press 5 for solid-liquid separation. The separated lithium-containing solution and residue (including phosphorus slag, carbon, etc.) are obtained. The residue enters the first pusher kiln 8 for high-temperature calcination to obtain a battery-grade iron phosphate precursor. The lithium-containing solution enters the lithium precipitation kettle 2 for lithium precipitation reaction. After filtration by the second filter press 6, lithium carbonate and sodium chloride wastewater are obtained. The sodium chloride wastewater undergoes an electrocatalytic reaction in the electrochemical reactor 3 to obtain a sodium hypochlorite solution, and the sodium hypochlorite solution returns to the leaching kettle 1 for recycling. The lithium carbonate is purified by stirring and washing in the washing kettle 4 to obtain battery-grade lithium carbonate. The battery-grade lithium carbonate and the battery-grade iron phosphate precursor enter the second pusher kiln 9 for high-temperature calcination to obtain battery-grade lithium iron phosphate.

[0052] Specifically, there are metal cations such as lithium and sodium in the chlorine-containing wastewater, and the anion is chlorine. The wastewater can generate new hypochlorites through electrocatalytic reaction and can be returned to the leaching kettle 11 for recycling, realizing the high-value recycling of wastewater, the electrochemical recycling of the leaching agent, and during the process of generating hypochlorites through multiple electrocatalytic reactions of the entire chlorine-containing wastewater in the electrochemical reactor 3, a very small amount of lithium is enriched each time, improving the total recovery rate of lithium elements and realizing the closed-loop recycling of lithium elements.

[0053] See the appendix Figure 1 As shown, in an alternative embodiment, the filtration and drying device includes a third filter press 7 and a tray dryer 11. The third filter press 7 is connected to the washing kettle 4 to receive and separate the lithium carbonate and washing waste liquid after washing from the washing kettle 4. The tray dryer 11 is connected to the third filter press 7 to receive and dry the lithium carbonate obtained from the third filter press 7.

[0054] Specifically, the setting of the third filter press 7 enables the recycling of the washing waste liquid after solid-liquid separation by the third filter press 7. The tray dryer 11 is used to dry the lithium carbonate after passing through the third filter press 7 to obtain battery-grade lithium carbonate.

[0055] See the appendix Figure 1 As shown, in an alternative embodiment, the system further includes a reverse osmosis membrane 10, which is connected to the third filter press 7 to receive and process the washing waste liquid from the third filter press 7, and sends the deionized water obtained through the pipeline to the washing kettle 4.

[0056] Specifically, the setting of the reverse osmosis membrane 10 enables the washing waste liquid after solid-liquid separation by the third filter press 7 to provide deionized water for the washing kettle 4 after passing through the reverse osmosis membrane 10.

[0057] See the appendix Figure 1As shown, in an alternative embodiment, the system further includes a batch mixer 12, which is connected to the first pusher kiln 8 and the tray dryer 11, receives and mixes the phosphate precursor obtained from the first pusher kiln 8 and the lithium carbonate obtained from the tray dryer 11, and feeds the mixed material into the second pusher kiln 9 through a pipeline.

[0058] Specifically, the batch mixer 12 can stir and mix the battery-grade lithium carbonate and the battery-grade iron phosphate precursor, and then enter the second pusher kiln 9 for high-temperature calcination, so that the lithium carbonate and the iron phosphate precursor entering the second pusher kiln 9 can fully react to regenerate the battery-grade lithium iron phosphate cathode material.

[0059] Refer to the appendix Figure 2 As shown, in an alternative embodiment, the electrochemical reactor 3 is a bipolar membrane electrochemical reactor. The bipolar membrane electrochemical reactor is a continuous flow pipeline, and a plurality of electrodes are embedded on the inner wall of the continuous flow pipeline. A bipolar membrane is arranged in the middle of the continuous flow pipeline, and the bipolar membrane isolates the bipolar membrane electrochemical reactor into a separate anode chamber 31 and a cathode chamber 32.

[0060] Specifically, the electrochemical reactor 3 is set as a bipolar membrane, which can greatly reduce the internal resistance. And the bipolar membrane electrochemical reactor is set as a continuous flow pipeline, which means that the liquid flows continuously in the pipeline, and the reactants are always in a flowing state. The continuous flow pipeline can realize continuous electrochemical reactions at high current densities, and has excellent hydrolysis dissociation performance and long-term use stability.

[0061] Specifically, an anode is arranged in the anode chamber 31 of the bipolar membrane electrochemical reactor. The anode is a working electrode, and the working electrode is set as a graphite rod. A cathode is arranged in the cathode chamber 32, and the cathode is a reference electrode, and the reference electrode is set as a mercury oxide electrode. The chlorine-containing wastewater enters the anode chamber 31, and sodium hypochlorite solution is generated after the reaction. Deionized water enters the cathode chamber 32, and hydrogen is generated after the reaction.

[0062] Refer to the appendix Figure 2 As shown, in an alternative embodiment, the cathode chamber 32 is connected to the first pusher kiln 8 through a pipeline, and the hydrogen obtained from the reaction in the cathode chamber 32 enters the first pusher kiln 8 through the pipeline as a reducing atmosphere.

[0063] Specifically, hydrogen is generated in the cathode chamber 32 of the bipolar membrane electrochemical reactor 3 through an electrocatalytic reaction. The hydrogen can be used as the reducing atmosphere of the first pusher kiln 8 to generate the battery-grade iron phosphate precursor from the residue, realizing the recycling of the hydrogen generated by the electrocatalytic reaction.

[0064] Refer to the appendix Figure 3 and the appendix Figure 4 As shown, the present invention also provides a method for electrochemically recycling phosphate-based cathode materials.

[0065] The present utility model also provides a method for electrochemically recycling a phosphate-based cathode material. The method includes the device described in any of the above embodiments and comprises the following steps:

[0066] S1: Mix the phosphate-based cathode waste with a hypochlorite solution in a leaching kettle to carry out a weak alkalization reaction, and perform solid-liquid separation through a first filter press to obtain a lithium-containing solution and a metal phosphate residue;

[0067] S2: Carry out a carbonation reaction on the lithium-containing solution in a lithium precipitation kettle, and perform solid-liquid separation through a second filter press to obtain lithium carbonate and chlorine-containing wastewater;

[0068] S3: Evaporate and concentrate the chlorine-containing wastewater in an evaporation and concentration device, and enter an electrochemical reactor for an electrocatalytic reaction to obtain a hypochlorite solution. The hypochlorite solution is recycled into the leaching kettle for reaction;

[0069] S4: After the lithium carbonate is stirred and purified in a cleaning kettle, perform solid-liquid separation and drying through a filtration and drying device to obtain battery-grade lithium carbonate;

[0070] S5: Calcinate the metal phosphate residue at a high temperature in a first pusher kiln to obtain a battery-grade phosphate precursor;

[0071] S6: After the battery-grade lithium carbonate and the battery-grade phosphate precursor are calcined at a high temperature in a second pusher kiln, regenerate the battery-grade phosphate-based cathode material.

[0072] Specifically, after the lithium carbonate in step S4 is stirred and purified in a cleaning kettle, solid-liquid separation is performed through a third filter press. The lithium carbonate obtained after solid-liquid separation enters a tray dryer for drying treatment to obtain a battery-grade lithium carbonate product.

[0073] Specifically, in step S6, the battery-grade lithium carbonate and the battery-grade phosphate precursor enter a batch mixer for stirring and mixing, and then enter a second pusher kiln for high-temperature calcination to regenerate the battery-grade phosphate product.

[0074] Specifically, by performing weak base oxidation leaching on the phosphate-based cathode waste, the purpose of preferentially extracting lithium is achieved. The metal phosphate residue is refined into a battery-grade phosphate precursor through high-temperature roasting, the lithium salt obtains battery-grade lithium carbonate through a carbonation reaction, and the lithium carbonate and the phosphate precursor obtain a battery-grade phosphate cathode material through a solid-phase reaction. Among them, the chlorine-containing wastewater generated after the lithium precipitation process undergoes an electrocatalytic reaction to generate new hypochlorite, which can be returned to the front end for weak base oxidation reaction to achieve the purpose of high-value recycling of by-products.

[0075] In an optional embodiment, in S1, the phosphate-based cathode waste and the hypochlorite solution are mixed at a molar ratio of 1 to 5:1, and the solid-liquid ratio is 1 to 1000 g / L.

[0076] Specifically, the phosphate cathode waste and the hypochlorite solution can be mixed at a molar ratio of 2:1, and the solid-liquid ratio is 1000 g / L.

[0077] In an alternative embodiment, in S3, the chlorine-containing wastewater is evaporated and concentrated to 15 - 20 g / L in an evaporation and concentration device.

[0078] In an alternative embodiment, in the said S3, the working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, the electrolyte is a sodium chloride solution, and a stepped cyclic voltammetry electro-chemical reaction is carried out. The voltage range of the stepped cyclic voltammetry is 1.1 - 2.4 V, the transition potential is 0.05 V, and the current density is 10 - 20 mA / cm2.

[0079] Specifically, the electrolyte sodium chloride solution is the chlorine-containing wastewater obtained by solid-liquid separation through a second filter press.

[0080] Example 1

[0081] This example provides a method for electrochemically recycling phosphate cathode materials, and the method includes the following steps:

[0082] S1: Mix the lithium iron phosphate cathode waste and the sodium hypochlorite solution in the leaching kettle at a molar ratio of 2:1, with a solid-liquid ratio of 1000 g / L, carry out a weak alkalization reaction for 3 hours, and perform solid-liquid separation through the first filter press to obtain a lithium-containing solution and iron phosphate residue;

[0083] S2: Carry out a carbonation reaction on the lithium-containing solution in the lithium precipitation kettle, and perform solid-liquid separation through the second filter press to obtain lithium carbonate and sodium chloride wastewater;

[0084] S3: Evaporate and concentrate the sodium chloride wastewater to 20 g / ml, enter a bipolar membrane electro-chemical reactor for electrocatalytic reaction to obtain a sodium hypochlorite solution. The sodium hypochlorite solution can be recycled into the leaching kettle for reaction. Among them, the working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, the electrolyte is a sodium chloride solution, and a stepped cyclic voltammetry electro-chemical performance test is carried out. The voltage range of the stepped cyclic voltammetry is 1.1 - 2.4 V, the transition potential is 0.05 V, and the current density is 10 mA / cm 2 , and the test time is 200 s;

[0085] S4: After the lithium carbonate is stirred and purified in the cleaning kettle, battery-grade lithium carbonate is obtained after filtration and drying;

[0086] S5: The iron phosphate residue is calcined at high temperature in a first pusher kiln to obtain a battery-grade iron phosphate precursor;

[0087] S6: After high-temperature calcination of battery-grade lithium carbonate and battery-grade iron phosphate precursor in a second pusher kiln, battery-grade lithium iron phosphate is regenerated.

[0088] Example 2

[0089] This example provides a method for electrochemically recycling phosphate-based cathode materials, and the method includes the following steps:

[0090] S1: Mix lithium iron phosphate cathode waste and sodium hypochlorite solution in the leaching kettle at a molar ratio of 2:1, with a solid-liquid ratio of 1000 g / L, conduct a weak alkalization reaction for 3 hours, and perform solid-liquid separation through the first filter press to obtain a lithium-containing solution and iron phosphate residue;

[0091] S2: Conduct a carbonation reaction on the lithium-containing solution in the lithium precipitation kettle, and perform solid-liquid separation through the second filter press to obtain lithium carbonate and sodium chloride wastewater;

[0092] S3: Evaporate and concentrate the sodium chloride wastewater to 15 g / ml, and enter a bipolar membrane electro-chemical reactor for electrocatalytic reaction to obtain a sodium hypochlorite solution. The sodium hypochlorite solution can be recycled into the leaching kettle for reaction. Among them, the working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, the electrolyte is a sodium chloride solution, and a stepped cyclic voltammetry electro-chemical performance test is performed. The voltage range of the stepped cyclic voltammetry is 1.1~2.4 V, the transition potential is 0.05 V, and the current density is 12 mA / cm 2 , and the test time is 200 s;

[0093] S4: After washing and purifying lithium carbonate in a washing kettle, battery-grade lithium carbonate is obtained after filtration and drying;

[0094] S5: High-temperature calcination of iron phosphate residue in a first pusher kiln to obtain battery-grade iron phosphate precursor;

[0095] S6: After high-temperature calcination of battery-grade lithium carbonate and battery-grade iron phosphate precursor in a second pusher kiln, battery-grade lithium iron phosphate is regenerated.

[0096] Example 3

[0097] This example provides a method for electrochemically recycling phosphate-based cathode materials, and the method includes the following steps:

[0098] S1: Mix lithium iron phosphate cathode waste and sodium hypochlorite solution in the leaching kettle at a molar ratio of 2:1, with a solid-liquid ratio of 1000 g / L, conduct a weak alkalization reaction for 3 hours, and perform solid-liquid separation through the first filter press to obtain a lithium-containing solution and iron phosphate residue;

[0099] S2: Subject the lithium-containing solution to a carbonation reaction in the lithium precipitation kettle, and perform solid-liquid separation through the second filter press to obtain lithium carbonate and sodium chloride wastewater;

[0100] S3: Evaporate and concentrate the sodium chloride wastewater to 20 g / ml, and feed it into a bipolar membrane electrochemical reactor for an electrocatalytic reaction to obtain a sodium hypochlorite solution. The sodium hypochlorite solution can be recycled into the leaching kettle for reaction. The working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, and the electrolyte is a sodium chloride solution. Perform a stepped cyclic voltammetry electrochemical performance test. The voltage range of the stepped cyclic voltammetry is 1.1 - 2.4 V, the transition potential is 0.05 V, and the current density is 12 mA / cm 2 , and the test time is 200 s;

[0101] S4: After washing and stirring and purifying the lithium carbonate through a cleaning kettle, obtain battery-grade lithium carbonate after filtration and drying;

[0102] S5: Calcinate the iron phosphate residue at high temperature in the first pusher kiln to obtain a battery-grade iron phosphate precursor;

[0103] S6: After high-temperature calcination of the battery-grade lithium carbonate and the battery-grade iron phosphate precursor in the second pusher kiln, regenerate battery-grade lithium iron phosphate.

[0104] Example 4

[0105] This example provides a method for electrochemically recycling a phosphate-based cathode material. The method includes the following steps:

[0106] S1: Mix the lithium iron phosphate cathode waste and the sodium hypochlorite solution in the leaching kettle at a molar ratio of 2:1, with a solid-liquid ratio of 1000 g / L, perform a weak alkalization reaction for 3 hours, and perform solid-liquid separation through the first filter press to obtain a lithium-containing solution and an iron phosphate residue;

[0107] S2: Subject the lithium-containing solution to a carbonation reaction in the lithium precipitation kettle, and perform solid-liquid separation through the second filter press to obtain lithium carbonate and sodium chloride wastewater;

[0108] S3: Evaporate and concentrate the sodium chloride wastewater to 20 g / ml, and feed it into a bipolar membrane electrochemical reactor for an electrocatalytic reaction to obtain a sodium hypochlorite solution. The sodium hypochlorite solution can be recycled into the leaching kettle for reaction. The working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, and the electrolyte is a sodium chloride solution. Perform a stepped cyclic voltammetry electrochemical performance test. The voltage range of the stepped cyclic voltammetry is 1.1 - 2.4 V, the transition potential is 0.05 V, and the current density is 20 mA / cm 2 , and the test time is 200 s;

[0109] S4: After washing and stirring lithium carbonate in a washing kettle for purification, battery-grade lithium carbonate is obtained after filtration and drying;

[0110] S5: The iron phosphate residue is calcined at high temperature in a first pusher kiln to obtain a battery-grade iron phosphate precursor;

[0111] S6: After high-temperature calcination of battery-grade lithium carbonate and the battery-grade iron phosphate precursor in a second pusher kiln, battery-grade lithium iron phosphate is regenerated.

[0112] Example 5

[0113] This example provides a method for electrochemically recycling phosphate-based cathode materials, and the method includes the following steps:

[0114] S1: The lithium iron phosphate cathode waste and sodium hypochlorite solution are mixed in the leaching kettle at a molar ratio of 2:1, the solid-liquid ratio is 1 g / L, a weak alkalization reaction is carried out for 3 hours, and solid-liquid separation is carried out through the first filter press to obtain a lithium-containing solution and an iron phosphate residue;

[0115] S2: The lithium-containing solution undergoes a carbonation reaction in the lithium precipitation kettle, and solid-liquid separation is carried out through the second filter press to obtain lithium carbonate and sodium chloride wastewater;

[0116] S3: The sodium chloride wastewater is evaporated and concentrated to 20 g / ml, enters a bipolar membrane electro-chemical reactor for electrocatalytic reaction to obtain a sodium hypochlorite solution, and the sodium hypochlorite solution can be recycled into the leaching kettle for reaction. Among them, the working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, the electrolyte is a sodium chloride solution, a stepped cyclic voltammetry electro-chemical performance test is carried out, the voltage range of the stepped cyclic voltammetry is 1.1~2.4 V, the transition potential is 0.05 V, and the current density is 10 mA / cm 2 , and the test time is 200 s;

[0117] S4: After washing and stirring lithium carbonate in a washing kettle for purification, battery-grade lithium carbonate is obtained after filtration and drying;

[0118] S5: The iron phosphate residue is calcined at high temperature in a first pusher kiln to obtain a battery-grade iron phosphate precursor;

[0119] S6: After high-temperature calcination of battery-grade lithium carbonate and the battery-grade iron phosphate precursor in a second pusher kiln, battery-grade lithium iron phosphate is regenerated.

[0120] Example 6

[0121] This example provides a method for electrochemically recycling phosphate-based cathode materials, and the method includes the following steps:

[0122] S1: Mix the lithium iron phosphate cathode waste with sodium hypochlorite solution in the leaching kettle at a molar ratio of 4:1, with a solid-liquid ratio of 1000 g / L, and conduct a weak alkalization reaction for 3 hours. Then, perform solid-liquid separation through the first filter press to obtain a lithium-containing solution and iron phosphate residue;

[0123] S2: Carry out a carbonation reaction on the lithium-containing solution in the lithium precipitation kettle, and perform solid-liquid separation through the second filter press to obtain lithium carbonate and sodium chloride wastewater;

[0124] S3: Evaporate and concentrate the sodium chloride wastewater to 20 g / ml, and then enter a bipolar membrane electro-chemical reactor for electrocatalytic reaction to obtain sodium hypochlorite solution. The sodium hypochlorite solution can be recycled into the leaching kettle for reaction. The working electrode of the electrocatalytic reaction is a graphite rod, the reference electrode is a mercury oxide electrode, and the electrolyte is a sodium chloride solution. Perform a stepped cyclic voltammetry electro-chemical performance test. The voltage range of the stepped cyclic voltammetry is 1.1 - 2.4 V, the transition potential is 0.05 V, and the current density is 10 mA / cm 2 , and the test time is 200 s;

[0125] S4: After washing and purifying the lithium carbonate in the washing kettle, filter and dry it to obtain battery-grade lithium carbonate;

[0126] S5: Calcinate the iron phosphate residue at high temperature in the first pusher kiln to obtain a battery-grade iron phosphate precursor;

[0127] S6: After calcining the battery-grade lithium carbonate and the battery-grade iron phosphate precursor at high temperature in the second pusher kiln, regenerate battery-grade lithium iron phosphate.

[0128] Test the sodium hypochlorite recovery rate and single-stage lithium recovery rate of the above examples.

[0129] Specifically, the sodium hypochlorite recovery rate = (the amount of sodium hypochlorite produced / the amount of original sodium hypochlorite) × 100%; the single-stage lithium recovery rate = (the amount of lithium recovered in a single stage / the amount of lithium contained in the waste in a single stage) × 100%.

[0130] The test results are as described in Table 1.

[0131] Table 1

[0132]

[0133] It can be analyzed from Table 1 that when changing the concentration of sodium chloride wastewater to 15 - 20 g / ml and the current density of the stepped cyclic voltammetry to 10 - 20 mA / cm 2 and when the lithium iron phosphate cathode waste and sodium hypochlorite solution are mixed in the leaching kettle at a molar ratio of 2:1, with a solid-liquid ratio of 1000 g / L, the concentration of sodium chloride wastewater at 20 g / ml, and the current density of the stepped cyclic voltammetry at 10 mA / cm2 At this time, the recovery rate of sodium hypochlorite and the single lithium recovery rate are the highest.

[0134] Comparative Example 1

[0135] The difference between this comparative example and Example 1 is that the recycled raw material is a ternary 811 cathode material, and the S3 electrocatalytic cycle process is not adopted.

[0136] The remaining preparation methods and parameters are the same as those in Example 1.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that the S3 electrocatalytic cycle process is not adopted.

[0139] The remaining preparation methods and parameters are the same as those in Example 1.

[0140] Test the single lithium recovery rate of the above comparative examples.

[0141] The test results are as described in Table 2.

[0142] Table 2

[0143]

[0144] It can be analyzed from Table 2 that the single lithium extraction efficiency of Comparative Example 1 is only 32.45%. The utility model inventor analyzes that this may be because ternary cathode materials are generally recycled using reducing reagents, while hypochlorite has oxidizing properties and is not suitable for the recycling of ternary cathode materials.

[0145] According to the comparative analysis of Table 1 and Table 2, the recycled raw material of Comparative Example 2 is a phosphate-based cathode material, and the single lithium recovery rate is relatively high. The recovery effect of Example 1 is the best. The generated chlorine-containing wastewater undergoes a bipolar membrane electrocatalytic process to generate new sodium hypochlorite, which can be returned to the front end for recycling, realizing the high-value recycling of wastewater, the electrochemical recycling of the leaching agent, and the regenerative closed-loop recycling of lithium elements.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present utility model.

Claims

1. An electrochemical system for recycling phosphate cathode materials, characterized in that, Including: Leaching kettle (1), used to receive phosphate cathode waste and hypochlorite solution, and accommodate the reaction of the phosphate cathode waste and hypochlorite solution; First filter press (5), connected to the leaching kettle (1), receiving and separating the lithium-containing solution and metal phosphate residue from the leaching kettle (1); Lithium precipitation kettle (2), connected to the first filter press (5), receiving the lithium-containing solution separated from the first filter press (5), receiving a lithium precipitant, and accommodating the reaction of the lithium-containing solution and the lithium precipitant; Second filter press (6), connected to the lithium precipitation kettle (2), receiving and separating lithium carbonate and chlorine-containing wastewater from the lithium precipitation kettle (2); Washing kettle (4), connected to the second filter press (6), receiving and washing lithium carbonate from the second filter press (6); Filtering and drying device, connected to the washing kettle (4), receiving, filtering and drying lithium carbonate from the washing kettle (4); Evaporation and concentration device (13), connected to the second filter press (6), receiving and evaporating and concentrating the chlorine-containing wastewater from the second filter press (6); Electrochemical reactor (3), connected to the evaporation and concentration device (13), receiving the chlorine-containing wastewater from the evaporation and concentration device (13), accommodating the electrochemical reaction of the chlorine-containing wastewater, and circulating the hypochlorite solution obtained after the electrochemical reaction into the leaching kettle (1); First pusher kiln (8), connected to the first filter press (5), receiving the metal phosphate residue from the first filter press (5), and calcining the metal phosphate at high temperature; Second pusher kiln (9), connected to the first pusher kiln (8) and the filtering and drying device, receiving the battery-grade phosphate precursor from the first pusher kiln (8) and the battery-grade lithium carbonate from the filtering and drying device, and accommodating the reaction of the battery-grade phosphate precursor and the battery-grade lithium carbonate; 2. The system for electrochemically recycling a phosphate-based cathode material according to claim 1, characterized in that, The filtering and drying device includes a third filter press (7) and a tray dryer (11). The third filter press (7) is connected to the washing kettle (4), receiving and separating the washed lithium carbonate and washing waste liquid from the washing kettle (4). The tray dryer (11) is connected to the third filter press (7), receiving and drying the lithium carbonate obtained from the third filter press (7).

3. The system for electrochemically recycling a phosphate-based cathode material according to claim 2, wherein It further includes a reverse osmosis membrane (10), connected to the third filter press (7), receiving and treating the washing waste liquid from the third filter press (7), and sending the deionized water obtained by treatment into the washing kettle (4) through a pipeline.

4. The system for electrochemically recycling a phosphate-based cathode material according to claim 2, wherein It further includes a batch mixer (12), connected to the first pusher kiln (8) and the tray dryer (11), receiving and mixing and stirring the phosphate precursor obtained from the first pusher kiln (8) and the lithium carbonate obtained from the tray dryer (11), and sending the mixed material into the second pusher kiln (9) through a pipeline.

5. The system for electrochemically recycling a phosphate-based cathode material according to claim 1, wherein, The electrochemical reactor (3) is a bipolar membrane electrochemical reactor. The bipolar membrane electrochemical reactor is a continuous flow pipeline. Multiple electrodes are inlaid on the inner wall of the continuous flow pipeline. A bipolar membrane is arranged in the middle of the continuous flow pipeline. The bipolar membrane isolates the bipolar membrane electrochemical reactor into a separate anodic chamber (31) and cathodic chamber (32).

6. The system for electrochemically recycling a phosphate-based cathode material according to claim 5, wherein The cathode chamber (32) is connected to the first pusher kiln (8) through a pipeline, and the hydrogen gas obtained by the reaction in the cathode chamber (32) enters the first pusher kiln (8) through the pipeline and serves as a reducing atmosphere.

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