Lithium iron phosphate preparation method based on sodium iron phosphate, lithium iron phosphate and lithium ion battery
Through the preparation method of lithium iron phosphate based on sodium iron phosphate, the two steps of desodium electrolysis and lithium embedded electrolysis were used to solve the problems of low lithium ion transmission rate of lithium iron phosphate materials and difficulty in recycling waste sodium phosphate, and the preparation of lithium iron phosphate materials with high electrochemical performance and environmental protection and sustainable development was achieved.
Patent Information
- Application Number
- CN202411975603.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-05-13
AI Technical Summary
The lithium ion transmission rate of existing lithium iron phosphate materials is low, which affects the improvement of electrochemical performance. At the same time, it is difficult to recover waste sodium iron phosphate, resulting in environmental pollution and waste of resources.
The preparation method of lithium iron phosphate based on sodium iron phosphate is adopted, and the effective de-extraction of sodium ions in sodium iron phosphate and uniform intercalation of lithium ions are achieved through the two steps of de-sodium electrolysis and lithium intercalation. Lithium iron phosphate with high electrochemical performance is prepared.
The specific capacity, cycle stability and fast charging and discharge capacity of lithium iron phosphate materials have been significantly improved, environmental pollution and resource waste have been reduced, and the recycling and reuse of waste sodium iron phosphate has been realized.
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Figure CN119980257A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of batteries, and in particular to a method for preparing lithium iron phosphate based on sodium iron phosphate, lithium iron phosphate and lithium-ion batteries. Background Art
[0002] Lithium iron phosphate occupies an important position in the field of lithium-ion batteries due to its excellent safety and long cycle life. However, conventional lithium iron phosphate materials have the problem of low lithium ion transmission rate, which affects the further improvement of their electrochemical performance.
[0003] As the positive electrode material of sodium ion batteries, sodium iron phosphate has the advantages of stable structure, high voltage platform, thermal stability, easy availability of raw materials, low price, and non-toxicity and pollution. However, waste sodium iron phosphate is easy to cause environmental pollution, and the treatment and recycling of waste sodium iron phosphate has always been an urgent problem to be solved in the industry. Summary of the invention
[0004] In view of this, the embodiments of the present application are committed to providing a method for preparing lithium iron phosphate based on sodium iron phosphate, lithium iron phosphate and lithium-ion batteries, so as to solve the problems in the prior art that conventional lithium iron phosphate materials have low lithium ion transmission rate and difficult recycling of waste sodium iron phosphate.
[0005] The first aspect of the present application provides a method for preparing lithium iron phosphate based on sodium iron phosphate, comprising:
[0006] Electrolyzing a sodium removal electrolytic cell using sodium iron phosphate as an anode to remove sodium ions from the sodium iron phosphate serving as an anode to form an iron phosphate intermediate;
[0007] Electrolysis is performed on a lithium insertion electrolytic cell which uses the iron phosphate intermediate as a cathode, a lithium-containing substance as an anode, and contains a lithium ion electrolyte, so that lithium ions are inserted into the iron phosphate intermediate to obtain lithium iron phosphate.
[0008] In one embodiment of the present application, the cathode in the de-sodium electrolytic cell is a lithium sheet or a carbon-based electrode, the electrolyte in the de-sodium electrolytic cell is a sodium salt aqueous solution or an organic solvent electrolyte, and the de-sodium electrolytic cell is provided with a sodium ion diaphragm for the passage of sodium ions.
[0009] In one embodiment of the present application, the anode in the lithium insertion electrolytic cell is a lithium sheet or a lithium-containing compound, and the lithium insertion electrolytic cell is provided with a lithium ion diaphragm for lithium ions to pass through.
[0010] In one embodiment of the present application, the process of electrolyzing a sodium-removing electrolytic cell with sodium iron phosphate as an anode and / or electrolyzing a lithium-insertion electrolytic cell with the iron phosphate intermediate as a cathode, a lithium-containing material as an anode, and a lithium-ion electrolyte is configured to be performed at a constant voltage or current density.
[0011] In one embodiment of the present application, before the step of electrolyzing the sodium-removing electrolytic cell with sodium iron phosphate as the anode to remove the sodium ions in the sodium iron phosphate as the anode to form the iron phosphate intermediate, the step further includes:
[0012] The sodium iron phosphate battery is disassembled to separate the positive electrode material of the sodium iron phosphate battery to obtain sodium iron phosphate powder, and the sodium iron phosphate powder is washed and dried to obtain sodium iron phosphate to be electrolyzed.
[0013] In one embodiment of the present application, after the step of electrolyzing the sodium-removing electrolytic cell with sodium iron phosphate as the anode to remove the sodium ions in the sodium iron phosphate as the anode to form the iron phosphate intermediate, the step further includes:
[0014] The prepared ferric phosphate intermediate is washed and dried to remove residual electrolyte and impurities in the ferric phosphate intermediate.
[0015] In one embodiment of the present application, after electrolyzing a lithium-ion electrolyte cell with the iron phosphate intermediate as a cathode, a lithium-containing substance as an anode, and a lithium-ion electrolyte to embed lithium ions into the iron phosphate intermediate to obtain lithium iron phosphate, the steps further include:
[0016] The lithium iron phosphate obtained by electrolysis is heat-treated in an inert atmosphere or a reducing atmosphere to obtain heat-treated lithium iron phosphate, wherein the temperature range of the heat treatment is set between 600-800° C. and the duration is not less than 6 hours.
[0017] In one embodiment of the present application, the step of heat treating the lithium iron phosphate obtained by electrolysis in an inert atmosphere or a reducing atmosphere to obtain the heat-treated lithium iron phosphate further includes:
[0018] The heat-treated lithium iron phosphate material is crushed and surface-modified.
[0019] A second aspect of the present application provides a lithium iron phosphate, which is prepared by using the sodium iron phosphate-based lithium iron phosphate preparation method.
[0020] A third aspect of the present application provides a lithium-ion battery using the lithium iron phosphate as an electrode material.
[0021] The sodium iron phosphate-based lithium iron phosphate preparation method of the present application can effectively utilize the sodium iron phosphate extracted from waste sodium iron phosphate batteries to prepare lithium iron phosphate, thereby effectively realizing the recycling and reuse of waste sodium iron phosphate battery materials, which can not only reduce environmental pollution, but also avoid waste of resources, effectively save costs, and comply with the concept of green and sustainable development.
[0022] Existing wet recovery or pyrometallurgical recovery methods cannot achieve the effective removal of sodium ions and uniform embedding of lithium ions in sodium iron phosphate. The method for preparing lithium iron phosphate based on sodium iron phosphate of the present application can achieve the effective removal of sodium ions and uniform embedding of lithium ions in sodium iron phosphate by adopting electrolytic sodium removal and electrolytic lithium embedding, and can also more accurately control the reaction process, reduce the use of chemical reagents and the generation of secondary pollution.
[0023] In the process of sodium removal and lithium insertion in the present application, the iron phosphate intermediate and the finally obtained lithium iron phosphate both maintain the original crystal form of sodium iron phosphate. Since the radius of sodium ions is larger than that of lithium ions, the lattice structure of the iron phosphate after sodium removal is relatively loose, providing a larger space for the subsequent insertion of lithium ions. Compared with the lithium iron phosphate obtained by other methods, the finally obtained lithium iron phosphate has a larger lithium ion channel, which significantly improves the electrochemical properties of the lithium iron phosphate material, and the specific capacity, cycle stability and rapid charge and discharge capabilities are all significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Shown is a schematic diagram of the steps of the method for preparing lithium iron phosphate based on sodium iron phosphate of the present application;
[0025] Figure 2 Shown is another schematic diagram of the step of the method for preparing lithium iron phosphate based on sodium iron phosphate of the present application. DETAILED DESCRIPTION
[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0027] Please refer to the following Figure 1 to Figure 2 , to illustrate the method for preparing lithium iron phosphate based on sodium iron phosphate of the present application.
[0028] like Figure 1 As shown, the present application provides a method for preparing lithium iron phosphate based on sodium iron phosphate, and the method for preparing lithium iron phosphate based on sodium iron phosphate comprises:
[0029] Step S101: electrolyzing a sodium-removing electrolytic cell with sodium iron phosphate as an anode to remove sodium ions from the sodium iron phosphate as an anode to form an iron phosphate intermediate.
[0030] It is understandable that the above-mentioned sodium iron phosphate may include not only sodium iron phosphate prepared by other methods, but also waste sodium iron phosphate extracted from waste lithium iron phosphate batteries.
[0031] Since the anode in the sodium removal electrolytic cell is sodium iron phosphate, when the sodium removal electrolytic cell with sodium iron phosphate as the anode is electrolyzed, the sodium ions in the sodium iron phosphate are released into the electrolyte, and the sodium iron phosphate is converted into an iron phosphate intermediate. During the electrolysis process of the sodium removal electrolytic cell, after the sodium ions in the sodium iron phosphate are removed, the iron phosphate intermediate still maintains the original crystal form of the sodium iron phosphate.
[0032] Further, in one embodiment of the present application, the cathode in the sodium-removing electrolytic cell is a lithium sheet or a carbon-based electrode, the electrolyte in the sodium-removing electrolytic cell is a sodium salt aqueous solution or an organic solvent electrolyte, and a sodium ion diaphragm for sodium ions to pass through is provided in the sodium-removing electrolytic cell. In the process of electrolysis of the sodium-removing electrolytic cell, the sodium ions in the sodium iron phosphate escape into the electrolyte, pass through the sodium ion diaphragm for sodium ions to pass through, and are embedded in the cathode. Since the cathode in the sodium-removing electrolytic cell is a lithium sheet or a carbon-based electrode, the electrolyte in the sodium-removing electrolytic cell is a sodium salt aqueous solution or an organic solvent electrolyte, and a sodium ion diaphragm for sodium ions to pass through is provided in the sodium-removing electrolytic cell, it can effectively ensure that the sodium ions in the sodium iron phosphate escape into the electrolyte to form an iron phosphate intermediate.
[0033] Step S102: electrolyzing a lithium-ion electrolyte cell with an iron phosphate intermediate as a cathode, a lithium-containing substance as an anode, and a lithium-ion electrolyte, so that lithium ions are embedded in the iron phosphate intermediate to obtain lithium iron phosphate.
[0034] Since the cathode of the lithium-ion electrolytic cell is an iron phosphate intermediate, the anode is a lithium-containing substance, and the electrolyte also contains lithium ion electrolyte; during the electrolysis of the lithium-ion electrolytic cell, the iron phosphate intermediate gains electrons, and the lithium ions move to the iron phosphate intermediate and then embed into the lattice of the iron phosphate intermediate to form lithium iron phosphate. It can be understood that the lithium ions are embedded in the iron phosphate intermediate to form
[0035] Furthermore, in one embodiment of the present application, the anode in the lithium-intercalation electrolytic cell is a lithium sheet or a lithium-containing compound, and a lithium-ion diaphragm for lithium ions to pass through is provided in the lithium-intercalation electrolytic cell. During the electrolysis of the lithium-intercalation electrolytic cell, the lithium ions at the anode escape into the electrolyte, pass through the lithium-ion diaphragm for lithium ions to pass through, and are embedded in the iron phosphate intermediate at the cathode. Since the anode in the lithium-intercalation electrolytic cell is a lithium sheet or a lithium-containing compound, the electrolyte contains lithium ions, and a lithium-ion diaphragm for lithium ions to pass through is provided therein, it can effectively ensure that the lithium ions are embedded in the iron phosphate intermediate to form lithium iron phosphate.
[0036] It can be seen that the method for preparing lithium iron phosphate based on sodium iron phosphate of the present application can effectively utilize sodium iron phosphate extracted from waste sodium iron phosphate batteries to prepare lithium iron phosphate, thereby effectively realizing the recycling and reuse of waste sodium iron phosphate battery materials, which can not only reduce environmental pollution, but also avoid waste of resources, effectively save costs, and comply with the concept of green and sustainable development.
[0037] Existing wet recovery or pyrometallurgical recovery methods cannot achieve the effective removal of sodium ions and uniform embedding of lithium ions in sodium iron phosphate. The method for preparing lithium iron phosphate based on sodium iron phosphate of the present application can achieve the effective removal of sodium ions and uniform embedding of lithium ions in sodium iron phosphate by adopting electrolytic sodium removal and electrolytic lithium embedding, and can also more accurately control the reaction process, reduce the use of chemical reagents and the generation of secondary pollution.
[0038] In the process of sodium removal and lithium insertion in the present application, the iron phosphate intermediate and the finally obtained lithium iron phosphate both maintain the original crystal form of sodium iron phosphate. Since the radius of sodium ions is larger than that of lithium ions, the lattice structure of the iron phosphate after sodium removal is relatively loose, providing a larger space for the subsequent insertion of lithium ions. Compared with the lithium iron phosphate obtained by other methods, the finally obtained lithium iron phosphate has a larger lithium ion channel, which significantly improves the electrochemical properties of the lithium iron phosphate material, and the specific capacity, cycle stability and rapid charge and discharge capabilities are all significantly improved.
[0039] In one embodiment of the present application, the process of electrolyzing a sodium-removing electrolytic cell with sodium iron phosphate as an anode and / or electrolyzing a lithium-insertion electrolytic cell with an iron phosphate intermediate as a cathode, a lithium-containing material as an anode, and a lithium-ion electrolyte is configured to be performed at a constant voltage or current density.
[0040] like Figure 2 As shown, in one embodiment of the present application, in step S101: electrolyzing a sodium-removing electrolytic cell with sodium iron phosphate as an anode to remove sodium ions from the sodium iron phosphate as an anode to form an iron phosphate intermediate, the step also includes:
[0041] Step S201: disassemble the sodium iron phosphate battery, separate the positive electrode material of the sodium iron phosphate battery to obtain sodium iron phosphate powder, and wash and dry the sodium iron phosphate powder to obtain sodium iron phosphate to be electrolyzed.
[0042] Specifically, the waste sodium iron phosphate batteries can be safely disassembled, and the positive electrode materials containing sodium iron phosphate can be separated from other battery components by mechanical crushing and physical screening technology to obtain waste sodium iron phosphate powder; the waste sodium iron phosphate powder is then washed multiple times with deionized water or an organic solvent to remove the electrolyte and other impurities remaining on the surface of the waste sodium iron phosphate powder, followed by drying to ensure the purity and dryness of the sodium iron phosphate to be electrolyzed, thereby ensuring that the lithium iron phosphate can be de-sodiumized normally and improving the purity of the iron phosphate intermediate obtained by subsequent electrolysis.
[0043] Therefore, the sodium iron phosphate-based lithium iron phosphate preparation method of the present application can effectively utilize the sodium iron phosphate extracted from waste sodium iron phosphate batteries, recycle and reuse the waste sodium iron phosphate battery materials, do not reduce environmental pollution, avoid waste of resources, and effectively save the preparation cost of lithium iron phosphate.
[0044] like Figure 2 As shown, in one embodiment of the present application, after step S101: electrolyzing a sodium-removing electrolytic cell with sodium iron phosphate as an anode to remove sodium ions from the sodium iron phosphate as an anode to form an iron phosphate intermediate, the following steps are further included:
[0045] Step S202: washing and drying the prepared ferric phosphate intermediate to remove residual electrolyte and impurities in the ferric phosphate intermediate.
[0046] Specifically, the iron phosphate intermediate obtained by electrolysis can be washed multiple times with deionized water or an organic solvent to remove residual electrolyte and other impurities on the surface of the iron phosphate intermediate, and then dried to ensure the purity and dryness of the iron phosphate intermediate, thereby ensuring that the iron phosphate intermediate can be normally embedded with lithium and improving the purity of the lithium iron phosphate obtained by subsequent electrolysis.
[0047] like Figure 2 As shown, in one embodiment of the present application, in step S102: electrolyzing a lithium-ion electrolyte cell with an iron phosphate intermediate as a cathode, a lithium-containing substance as an anode, and a lithium-ion electrolyte to embed lithium ions into the iron phosphate intermediate to obtain lithium iron phosphate, the following steps further include:
[0048] Step S203: heat-treating the lithium iron phosphate obtained by electrolysis in an inert atmosphere or a reducing atmosphere to obtain heat-treated lithium iron phosphate, wherein the heat treatment temperature range is set between 600-800° C. and the duration is not less than 6 hours.
[0049] By heat treating the lithium iron phosphate obtained by electrolysis, and setting the temperature range of the heat treatment between 600-800°C for not less than 6 hours, the crystallinity and stability of the lithium iron phosphate obtained by electrolytic lithium insertion can be effectively improved. It is understood that the inert atmosphere can be nitrogen, argon, etc., and the reducing atmosphere can be hydrogen, carbon monoxide, etc., and the lithium iron phosphate is heat treated in an inert atmosphere or a reducing atmosphere to prevent the lithium iron phosphate from being oxidized during the heat treatment process.
[0050] like Figure 2 As shown, in one embodiment of the present application, step S203: heat-treating the lithium iron phosphate obtained by electrolysis in an inert atmosphere or a reducing atmosphere to obtain the heat-treated lithium iron phosphate, and the subsequent steps also include:
[0051] Step S204: crushing and surface modifying the heat-treated lithium iron phosphate material.
[0052] By crushing and screening the heat-treated lithium iron phosphate material, lithium iron phosphate powder particles that meet the requirements can be obtained; and surface modification of the lithium iron phosphate powder by coating, doping and other methods can effectively improve the electrochemical properties of lithium iron phosphate, such as electrical conductivity, cycle stability and thermal stability.
[0053] Specifically, by coating the surface of lithium iron phosphate powder with a layer of conductive carbon material such as carbon black and graphene, the conductivity of the resulting lithium iron phosphate can be effectively improved; by doping lithium iron phosphate with other metal elements such as magnesium and aluminum, the crystal structure and electrochemical properties of the resulting lithium iron phosphate can be effectively improved.
[0054] The present application also provides a lithium iron phosphate, which is prepared by using the aforementioned method for preparing lithium iron phosphate based on sodium iron phosphate.
[0055] The lithium iron phosphate prepared by the sodium iron phosphate-based lithium iron phosphate preparation method of the present application can effectively ensure that lithium ions are evenly embedded in the crystal lattice, and the obtained lithium iron phosphate maintains the original crystal form of sodium iron phosphate. Since the radius of sodium ions is larger than that of lithium ions, the lattice structure of iron phosphate after sodium removal is relatively loose, providing a larger space for the subsequent embedding of lithium ions; the finally obtained lithium iron phosphate has a larger lithium ion channel than the lithium iron phosphate obtained by other methods, which significantly improves the electrochemical properties of the lithium iron phosphate material, and the specific capacity, cycle stability and rapid charge and discharge capabilities are significantly improved.
[0056] The present application also provides a lithium-ion battery, using the lithium iron phosphate prepared by the lithium iron phosphate preparation method based on sodium iron phosphate as an electrode material. Compared with existing lithium-ion batteries, the lithium-ion battery provided by the present application has significantly improved performance such as specific capacity, cycle stability, and rapid charge and discharge capability.
[0057] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims
1. A method for preparing lithium iron phosphate based on sodium iron phosphate, characterized in that: include: Electrolyzing a sodium removal electrolytic cell using sodium iron phosphate as an anode to remove sodium ions from the sodium iron phosphate serving as an anode to form an iron phosphate intermediate; Electrolysis is performed on a lithium insertion electrolytic cell which uses the iron phosphate intermediate as a cathode, a lithium-containing substance as an anode, and contains a lithium ion electrolyte, so that lithium ions are inserted into the iron phosphate intermediate to obtain lithium iron phosphate.
2. The method for preparing lithium iron phosphate based on sodium iron phosphate according to claim 1, characterized in that: The cathode in the sodium removal electrolytic cell is a lithium sheet or a carbon-based electrode, the electrolyte in the sodium removal electrolytic cell is a sodium salt aqueous solution or an organic solvent electrolyte, and the sodium removal electrolytic cell is provided with a sodium ion diaphragm for sodium ions to pass through.
3. The method for preparing lithium iron phosphate based on sodium iron phosphate according to claim 1, characterized in that: The anode in the lithium-intercalation electrolytic cell is a lithium sheet or a lithium-containing compound, and the lithium-intercalation electrolytic cell is provided with a lithium-ion diaphragm for lithium ions to pass through.
4. The method for preparing lithium iron phosphate based on sodium iron phosphate according to any one of claims 1 to 3, characterized in that: The process of electrolyzing a sodium removal electrolytic cell with sodium iron phosphate as an anode and / or electrolyzing a lithium insertion electrolytic cell with the iron phosphate intermediate as a cathode, a lithium-containing material as an anode, and a lithium ion electrolyte is configured to be performed at a constant voltage or current density.
5. The method for preparing lithium iron phosphate based on sodium iron phosphate according to any one of claims 1 to 3, characterized in that: Before the step of electrolyzing the sodium-removing electrolytic cell with sodium iron phosphate as the anode to remove the sodium ions in the sodium iron phosphate as the anode to form the iron phosphate intermediate, the step further includes: The sodium iron phosphate battery is disassembled to separate the positive electrode material of the sodium iron phosphate battery to obtain sodium iron phosphate powder, and the sodium iron phosphate powder is washed and dried to obtain sodium iron phosphate to be electrolyzed.
6. The method for preparing lithium iron phosphate based on sodium iron phosphate according to any one of claims 1 to 3, characterized in that: After the step of electrolyzing the sodium-removing electrolytic cell with sodium iron phosphate as the anode to remove sodium ions from the sodium iron phosphate as the anode to form an iron phosphate intermediate, the following steps are further included: The prepared ferric phosphate intermediate is washed and dried to remove residual electrolyte and impurities in the ferric phosphate intermediate.
7. The method for preparing lithium iron phosphate based on sodium iron phosphate according to any one of claims 1 to 3, characterized in that: After electrolyzing a lithium-ion electrolyte cell using the iron phosphate intermediate as a cathode, a lithium-containing substance as an anode, and a lithium-ion electrolyte to embed lithium ions into the iron phosphate intermediate to obtain lithium iron phosphate, the following steps are further included: The lithium iron phosphate obtained by electrolysis is heat-treated in an inert atmosphere or a reducing atmosphere to obtain heat-treated lithium iron phosphate, wherein the temperature range of the heat treatment is set between 600-800° C. and the duration is not less than 6 hours.
8. The method for preparing lithium iron phosphate based on sodium iron phosphate according to any one of claims 1 to 3, characterized in that: The step of heat treating the lithium iron phosphate obtained by electrolysis in an inert atmosphere or a reducing atmosphere to obtain the heat-treated lithium iron phosphate further includes: The heat-treated lithium iron phosphate material is crushed and surface-modified.
9. A lithium iron phosphate, characterized in that: The lithium iron phosphate is prepared by the method for preparing lithium iron phosphate based on sodium iron phosphate according to any one of claims 1 to 8.
10. A lithium ion battery, characterized in that: The lithium iron phosphate described in claim 9 is used as the electrode material.