A sodium ion battery positive electrode material and preparation method

Abstract

The present application discloses a sodium ion battery positive electrode material and a preparation method thereof, comprising sodium ferric sulfate, a carbon material and a plurality of metal ions, wherein the carbon material is dispersed between the sodium ferric sulfate and the metal ions are doped in the crystal structure of the sodium ferric sulfate; the sodium ion battery positive electrode material is prepared using an iron source, a layered oxide precursor byproduct having sodium sulfate and the carbon material as raw materials; the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn 4+ At least two of the above. The dispersion of carbon materials and the doping of multiple metal ions in this application can effectively improve the rate performance and cycle performance of sodium-ion battery cathode materials. Furthermore, the sodium-ion battery cathode material is prepared using an iron source, a layered oxide precursor byproduct, and a carbon material as raw materials. Process waste is used to prepare the sodium-ion battery cathode material, thereby reducing the production cost of the sodium-ion battery cathode material and saving energy consumption and environmental costs associated with processing process waste.

Description

Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery positive electrode material and a preparation method thereof. Background Art

[0002] Sodium ferric sulfate positive electrode material has the remarkable characteristics of low cost, high voltage, long cycle, and high safety performance. It is suitable for application scenarios such as electric vehicles and energy storage. In the current mainstream sodium ferric sulfate synthesis process, the raw materials used are mostly ferrous sulfate and sodium sulfate powder. In order to ensure the quality of sodium ferric sulfate positive electrode material products, the ferrous sulfate and sodium sulfate used are both battery grade. They are produced through chemical synthesis methods to ensure the purity of ferrous sulfate and sodium sulfate, which increases the overall preparation cost of sodium ferric sulfate and limits its production capacity. Summary of the Invention

[0003] In response to the problems existing in the above-mentioned prior art, the present application provides a sodium ion battery positive electrode material and a preparation method, and the technical solution is as follows:

[0004] On the one hand, the present application provides a sodium ion battery positive electrode material, the sodium ion battery positive electrode material comprising sodium ferric sulfate, a carbon material and a plurality of metal ions, wherein the carbon material is dispersed between the sodium ferric sulfate, and the metal ions are doped in the crystal structure of the sodium ferric sulfate;

[0005] The sodium ion battery positive electrode material is prepared from an iron source, a layered oxide precursor byproduct having sodium sulfate, and a carbon material as raw materials; the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn 4+ At least two of the .

[0006] Furthermore, the iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, the titanium dioxide byproduct includes metal ions, the titanium dioxide byproduct and / or the layered oxide precursor byproduct include metal ions, and the metal ions include Ni 2+ Mg 2+ 、Co 2+ and Mn 4+ ;

[0007] The chemical formula of the sodium ion battery positive electrode material is Na x Fe y Ni a Co b Mn c Mg d (SO4) z @C, where 1≤x / y≤2, (a+b+c+d) / y≤0.1.

[0008] Furthermore, the sodium ion battery positive electrode material is obtained by performing a first purification treatment on a titanium dioxide byproduct to obtain a first purified solution, performing a second purification treatment on a layered oxide precursor byproduct to obtain a second purified solution, mixing the first purified solution, the second purified solution and a carbon material, drying them, and granulating and sintering them;

[0009] The first purification process can remove insoluble substances in the titanium dioxide by-product, and the first purification solution includes ferrous sulfate heptahydrate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ Mg 2+ and Mn 4+ At least two of the following;

[0010] The second purification treatment can remove ammonia nitrogen in the layered oxide precursor byproduct; the second purification solution includes sodium sulfate and a plurality of soluble metal ions, the soluble metal ions including Ni 2+ 、Co 2+ and Mn 4+ At least two of the .

[0011] Furthermore, the first purified solution and the second purified solution are mixed according to a preset x / y value between the sodium element and the iron element by measuring the iron content and the sodium content in the first purified solution, measuring the sodium content in the second purified solution, and wherein 1.2≤x / y≤1.8.

[0012] On the other hand, the present application also provides a method for preparing a positive electrode material for a sodium ion battery, wherein the positive electrode material for a sodium ion battery is prepared using an iron source, a layered oxide precursor byproduct having sodium sulfate, and a carbon material as raw materials; the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn 4+ At least two of the following;

[0013] The sodium ion battery positive electrode material includes sodium ferric sulfate, a carbon material and a plurality of metal ions, wherein the carbon material is dispersed among the sodium ferric sulfate, and the metal ions are doped in the crystal structure of the sodium ferric sulfate.

[0014] Furthermore, the iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, and the titanium dioxide byproduct includes metal ions, and the metal ions include Ni 2+ Mg 2+ , and Mn 4+ At least two of the above; the sodium ion battery positive electrode material prepared by using an iron source, a layered oxide precursor byproduct having sodium sulfate and a carbon material as raw materials includes:

[0015] The titanium dioxide by-product is subjected to a first purification treatment to obtain a first purified solution; the first purification treatment can remove insoluble substances in the titanium dioxide by-product, and the first purified solution includes ferrous sulfate heptahydrate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ Mg 2+ and Mn 4+ At least two of the following;

[0016] The layered oxide precursor by-product is subjected to a second purification treatment to obtain a second purified solution; the second purification treatment can remove ammonia nitrogen in the layered oxide precursor by-product, and the second purified solution includes sodium sulfate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ 、Co 2+ and Mn 4+ At least two of the following;

[0017] Mixing and drying the first purified solution, the second purified solution, and the carbon material to obtain a positive electrode material precursor;

[0018] Granulating the positive electrode material precursor to obtain a precursor pressed material;

[0019] The precursor pressed material is sintered and crushed to obtain the sodium ion battery positive electrode material.

[0020] Furthermore, the first purification process of the titanium dioxide by-product to obtain a first purified solution includes:

[0021] dissolving the titanium dioxide by-product in deionized water, and dispersing iron powder in the deionized water to obtain a first initial solution;

[0022] The sodium hydroxide solution and the first initial solution are mixed until the pH of the first initial solution reaches the first target pH, and filtered to obtain a filtrate; the first target pH is 4.5 to 5; the titanium dioxide by-product also includes Ti 2+ , in the case of the first target pH, the Ti in the first initial solution 2+ A precipitation reaction occurs to form an insoluble titanium precipitate;

[0023] Sulfuric acid, an antioxidant and the filtrate are mixed until the pH of the filtrate reaches a second target pH to obtain the first purified solution; the second target pH is 2 to 3.5.

[0024] Furthermore, the titanium dioxide by-product is subjected to a first purification treatment to obtain a first purified solution that meets at least one of the following characteristics:

[0025] The insoluble matter of the titanium dioxide by-product includes titanium dioxide, and the mass proportion of the titanium dioxide in the titanium dioxide by-product is less than the first mass proportion, which is 0.7% to 1.3%;

[0026] The mass proportion of the multiple soluble metal ions of the first purified solution in the titanium dioxide by-product is less than the second mass proportion, and the second mass proportion is 0.7% to 1.3%;

[0027] The concentration of ferrous sulfate heptahydrate in the first initial solution is 50 g / L to 150 g / L;

[0028] The mass percentage between the iron powder and the ferrous sulfate heptahydrate is 0.1% to 1%;

[0029] The pH of the sodium hydroxide solution is 10-13;

[0030] The antioxidant comprises at least one of ascorbic acid, oxalic acid and citric acid;

[0031] The mass percentage between the antioxidant and the ferrous sulfate heptahydrate is 0.1% to 3%.

[0032] Furthermore, the step of performing a second purification treatment on the layered oxide precursor by-product to obtain a second purified solution comprises:

[0033] Deamination treatment is performed on the layered oxide precursor byproduct to obtain a second initial solution;

[0034] Sulfuric acid and the second initial solution are mixed until the pH of the second initial solution reaches a third target pH, thereby obtaining the second purified solution; the third target pH is 6.7 to 7.0.

[0035] Furthermore, the second purification treatment is performed on the layered oxide precursor by-product to obtain a second purified solution that meets at least one of the following characteristics:

[0036] The pH of the layered oxide precursor byproduct is greater than 12;

[0037] The concentration of sodium sulfate in the layered oxide precursor by-product is 50 g / L to 200 g / L;

[0038] The ammonia nitrogen content in the layered oxide precursor by-product is 5 g / L to 10 g / L;

[0039] The content of the multiple soluble metal ions in the layered oxide precursor by-product of the second purified solution is 75 mg / L to 130 mg / L.

[0040] On the other hand, the present application also provides a sodium ion battery, comprising the sodium ion battery positive electrode material as described in any of the above items, or comprising the sodium ion battery positive electrode material prepared by the preparation method of the sodium ion battery positive electrode material as described in any of the above items.

[0041] The implementation of this application has the following beneficial effects:

[0042] The sodium-ion battery cathode material is prepared using an iron source, a layered oxide precursor byproduct containing sodium sulfate and multiple metal ions, and a carbon material as raw materials. Process waste is used as a sodium source to prepare the sodium-ion battery cathode material, thereby realizing a preparation process flow directly from byproducts to the sodium-ion battery cathode material, improving waste utilization rate. Compared with the preparation process requiring a high-purity sodium source in traditional processes, the production process of the sodium-ion battery cathode material is simplified, the raw material cost and the production cost of the sodium-ion battery cathode material are reduced, and the energy consumption and environmental protection costs caused by processing process wastes such as the layered oxide precursor byproduct are greatly saved, thereby reducing carbon emissions in the production environment, and improving the economy and environmental friendliness of the sodium-ion battery cathode material and its preparation process.

[0043] The layered oxide precursor byproduct of this application contains Ni 2+ ,Co 2+ The prepared sodium ion battery positive electrode material contains metal ions Ni 2+ ,Co 2+ , where Ni 2+ Because of the existence of Ni 2+ / Ni 3+ Redox couple, which can provide capacity during the charge and discharge process, Co 2+ It can effectively reduce the charge transfer impedance and thus improve the rate performance of the sodium ion battery positive electrode material. The capacity of the sodium ion battery prepared using the positive electrode material of the present application is improved and has good rate performance.

[0044] At the same time, this preparation method does not require additional doping of metal ions, which not only simplifies a process but also saves the cost of metal ion raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in the embodiments, wherein identical components are denoted by identical reference numerals. Obviously, the drawings described below are merely some embodiments of this application, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0046] Figure 1 Flow chart of the preparation method of the sodium ion battery positive electrode material provided in Example 1 of the present application;

[0047] Figure 2 This is a comparison chart of the rate performance of the sodium ion battery positive electrode materials provided in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments, and therefore should not be understood as limiting this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] It should be noted that in the description of this application, for the following defined terms, these definitions should be applied unless a different definition is given in the claims or elsewhere in this specification. All numerical values, whether or not explicitly indicated, are defined herein as being modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art would consider to be equivalent to the stated value to produce substantially the same properties, functions, results, etc. A numerical range indicated by a low value and a high value is defined to include all numerical values included in the numerical range and all subranges included in the numerical range.

[0050] It should be noted that the terms "first", "second", etc. in the specification, claims, and drawings of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the objects used in this way can be interchangeable where appropriate, so that the embodiments of the present application can be implemented in a sequence other than the following diagrams or the following descriptions. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, or product comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or that are inherent to these processes, methods, or products.

[0051] The embodiment of the present application provides a sodium ion battery positive electrode material, which includes sodium ferric sulfate, a carbon material and a plurality of metal ions, wherein the carbon material is dispersed between the sodium ferric sulfate, and the metal ions are doped in the crystal structure of the sodium ferric sulfate, that is, the metal ions are filled in the crystal structure of the sodium ferric sulfate; and the sodium ion battery positive electrode material is prepared by using an iron source, a layered oxide precursor byproduct having sodium sulfate and a carbon material as raw materials, wherein the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn4+ At least two of the .

[0052] Among them, sodium sulfate is a by-product of the lithium battery\sodium battery layered oxide positive electrode material precursor industry. Theoretically, about 1.5 tons of sodium sulfate will be produced during the synthesis of one ton of layered oxide positive electrode material precursor. These sodium sulfates are all present in the waste liquid of the precursor synthesis. This application uses industrial waste as a sodium source to prepare sodium ion battery positive electrode materials, realizing a preparation process flow directly from by-products to sodium ion battery positive electrode materials, improving waste utilization rate, and compared with the preparation process requiring a high-purity sodium source in traditional processes, simplifying the production process of the sodium ion battery positive electrode material, reducing the cost of raw materials and the production cost of the sodium ion battery positive electrode material, and greatly saving the energy consumption and environmental protection costs brought about by the treatment of process wastes such as layered oxide precursor by-products, reducing carbon emissions in the production environment, and improving the economy and environmental friendliness of the sodium ion battery positive electrode material and its preparation process.

[0053] The layered oxide precursor byproduct of this application contains Ni 2+ ,Co 2+ The prepared sodium ion battery positive electrode material contains metal ions Ni 2+ ,Co 2+ , where Ni 2+ Because of the existence of Ni 2+ / Ni 3+ Redox couple, which can provide capacity during the charge and discharge process, Co 2+ It can effectively reduce the charge transfer impedance and thus improve the rate performance of the sodium ion battery positive electrode material. The capacity of the sodium ion battery prepared using the positive electrode material of the present application is improved and has good rate performance.

[0054] At the same time, this preparation method does not require additional doping of metal ions, which not only simplifies a process but also saves the cost of metal ion raw materials.

[0055] Specifically, in some exemplary embodiments, the iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, and at least one of the titanium dioxide byproduct and the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ Mg 2+ 、Co 2+ and Mn 4+ .

[0056] Among them, ferrous sulfate heptahydrate is the largest by-product in the titanium dioxide industry. Theoretically, the production of one ton of titanium dioxide will produce 3.5 to 4 tons of titanium dioxide by-products. This application further uses industrial waste as an iron source to prepare sodium ion battery positive electrode materials, realizing a preparation process flow directly from by-products to sodium ion battery positive electrode materials, further improving waste utilization. Compared with the preparation process requiring a high-purity iron source in traditional processes, it further simplifies the production process of the sodium ion battery positive electrode material, reduces the cost of raw materials and the production cost of the sodium ion battery positive electrode material, and greatly saves the energy consumption and environmental protection costs brought about by the treatment of titanium dioxide by-products and other process wastes, reduces carbon emissions in the production environment, and improves the economy and environmental friendliness of the sodium ion battery positive electrode material and its preparation process.

[0057] At least one of the titanium dioxide byproduct and / or layered oxide precursor of the present invention includes metal ions, and the metal ions include Ni 2+ Mg 2+ 、Co 2+ and Mn 4+ The prepared sodium ion battery cathode material also includes Ni 2+ Mg 2+ 、Co 2+ and Mn 4+ .

[0058] Among them, Ni 2+ Ni exists 2+ / Ni 3+ The redox pair can also provide capacity during the charge and discharge process, which can further improve the capacity of the sodium ion battery positive electrode material to a certain extent; Mg 2+ Doping in the crystal structure of sodium iron sulfate can make the sodium ion battery cathode material obtain a smaller particle size morphology, increase the contact area between the electrode sheet with the sodium ion battery cathode material and the electrolyte in the sodium ion battery, further accelerate the charge transfer between the electrode sheet and the electrolyte interface, and Mg 2+ It can also play a supporting role in the lattice, preventing the crystal structure of the sodium ion battery positive electrode material from collapsing during the cycle, thereby improving the cycle stability of the sodium ion battery positive electrode material; Co 2+ It can effectively reduce the charge transfer impedance and improve the rate performance of the sodium ion battery cathode material; Mn 4+It does not change price and does not participate in the charge and discharge process, but it can also improve the structural stability of the positive electrode material of the sodium ion battery; by doping a variety of metal ions in the crystal structure of sodium ferric sulfate, it can effectively improve the rate performance and cycle performance of the positive electrode material of the sodium ion battery, and make up for the performance degradation that may be caused by insufficient purity of raw materials, so that the sodium ion battery positive electrode material prepared with titanium dioxide by-products and layered oxide precursor by-products as part of the raw materials has a performance comparable to that of the sodium ferric sulfate positive electrode material prepared with high-purity raw materials.

[0059] Specifically, in some exemplary embodiments, the metal ions of the titanium dioxide by-product include Ni 2+ Mg 2+ , and Mn 4+ In other exemplary embodiments, the metal ions of the layered oxide precursor by-products include Ni 2+ 、Co 2+ and Mn 4+ At least two of the .

[0060] In some exemplary embodiments, the titanium dioxide by-product includes metal ions, and the metal ions in the titanium dioxide by-product include Mg 2+ and Mn 4+ In other exemplary embodiments, the layered oxide precursor by-product includes metal ions, and the metal ions in the layered oxide precursor by-product include Ni 2+ 、Co 2+ and Mn 4+ .

[0061] In other exemplary embodiments, the titanium dioxide by-product includes metal ions, and the metal ions in the titanium dioxide by-product include Ni 2+ Mg 2+ and Mn 4+ , and the layered oxide precursor by-product includes metal ions, and the metal ions in the layered oxide precursor by-product include Ni 2+ 、Co 2+ and Mn 4+ .

[0062] Specifically, the chemical formula of the sodium ion battery cathode material is Na x Fe y Ni a Co b Mn c Mg d (SO4) z@C, where 1≤x / y≤2, (a+b+c+d) / y≤0.1; it is understood that the value of x / y can be any value between 1 and 2, and the value of (a+b+c+d) / y can be any value less than or equal to 0.1; for example, the value of x / y can be 1, 1.1, 1.2, 1.5, 1.7, 1.9, 2, etc.; the value of (a+b+c+d) / y can be 0.1, 0.08, 0.05, 0.03, 0.01, 0.008, 0.0 0.4, 0.002, etc.; in this way, the sodium ion battery positive electrode material can have a good specific capacity, and the rate performance and cycle performance of the sodium ion battery positive electrode material are improved; further, in some exemplary embodiments, 1.2≤x / y≤1.8; in some preferred embodiments, 1.3≤x / y≤1.7, (a+b+c+d) / y≤0.05, which is conducive to further improving the specific capacity of the sodium ion battery positive electrode material and improving the rate performance and cycle performance of the sodium ion battery positive electrode material.

[0063] Specifically, the sodium ion battery positive electrode material is obtained by performing a first purification treatment on the titanium dioxide by-product to obtain a first purified solution, performing a second purification treatment on the layered oxide precursor by-product to obtain a second purified solution, and mixing the first purified solution, the second purified solution and the carbon material to dry, and then granulating and sintering.

[0064] The titanium dioxide by-product is a solid waste material containing insoluble substances, including insoluble titanium dioxide and insoluble impurities (e.g., dust, particles), etc. The first purification process can remove the insoluble substances in the titanium dioxide by-product, and the various metal ions in the titanium dioxide by-product include various soluble metal ions. During the first purification process, the various metal ions can be at least partially dissolved, so that after the first purification process, the first purified solution includes ferrous sulfate heptahydrate and various soluble metal ions. The soluble metal ions in the first purified solution include Ni 2+ Mg 2+ and Mn 4+ At least two of the above can be doped into the crystal structure of sodium iron sulfate during the subsequent preparation process to improve the performance of the sodium ion battery positive electrode material.

[0065] The layered oxide precursor by-product is a liquid waste in the form of a solution. The layered oxide precursor by-product contains ammonia nitrogen and a small amount of metal ions. Ammonia nitrogen (abbreviated as NH3-N) refers to the free ammonia (NH3) and ammonium salt (NH3) in the solution of the layered oxide precursor by-product. 4+) in the form of nitrogen, the second purification process can remove ammonia nitrogen in the layered oxide precursor by-product, so that after the second purification process, the second purification solution includes sodium sulfate and a plurality of soluble metal ions, and the soluble metal ions in the second purification solution include Ni 2+ 、Co 2+ and Mn 4+ At least two of the above can be doped into the crystal structure of sodium ferric sulfate in the subsequent preparation process to improve the performance of the positive electrode material of sodium ion battery; In addition, it should be noted that the metal ions and / or soluble metal ions in this application refer to the metal ions other than Na + and Fe 2+ The impurity metal ions are relatively small in content and are used to dope the crystal structure of sodium ferric sulfate. Other metal ions such as Ca may also be present in the titanium dioxide by-product and the layered oxide precursor by-product. 2+ and Al 3+ etc., may remain in the positive electrode materials of sodium ion batteries after preparation, but their impact on the performance of the positive electrode materials of sodium ion batteries is small and can be ignored.

[0066] In this way, there is no need to purify each by-product to an extremely high purity to produce a sodium ion battery positive electrode material with relatively good performance, saving the cost of purifying and recycling industrial waste, improving waste utilization, and reducing pollution. At the same time, using industrial waste as raw materials to prepare sodium ion battery positive electrode materials can also simplify the production process and reduce the production cost of sodium ion battery positive electrode materials.

[0067] Specifically, the first purified solution and the second purified solution are mixed by measuring the iron content and the sodium content in the first purified solution, measuring the sodium content in the second purified solution, and according to a preset x / y value between the sodium element and the iron element; wherein 1.2≤x / y≤1.8; this is conducive to improving the accuracy of the proportion of each component in the sodium ion battery positive electrode material and effectively improving the performance of the sodium ion battery positive electrode material.

[0068] Specifically, the carbon material includes at least one of graphite, graphene, carbon black, single-walled carbon nanotubes and multi-walled carbon nanotubes, has good electrical conductivity, can effectively enhance the electrical conductivity between ions, reduce the risk of battery polarization in a sodium ion battery having the sodium ion battery positive electrode material, inhibit grain growth, shorten the transmission path of sodium ions in the sodium ion battery positive electrode material, improve the sodium ion transmission efficiency, and greatly improve the conductivity of the sodium ion battery positive electrode material.

[0069] Specifically, the mass proportion of the carbon material in the sodium ion battery positive electrode material is 0.5% to 10%; it can be understood that the mass proportion of the carbon material in the sodium ion battery positive electrode material can be any point value between 0.5% and 10%; illustratively, the mass proportion of the carbon material in the sodium ion battery positive electrode material can be 0.5%, 0.7%, 1.0%, 1.5%, 2.0%, 3.0%, 5.0%, 8.0%, 10%, etc.; in this way, the carbon material is well dispersed in the sodium ion battery positive electrode material, which can improve the conductivity, conductive uniformity and electrochemical performance of the sodium ion battery positive electrode material.

[0070] On the other hand, the present application also provides a method for preparing a positive electrode material for a sodium ion battery, wherein the positive electrode material for a sodium ion battery is prepared using an iron source, a layered oxide precursor byproduct having sodium sulfate, and a carbon material as raw materials; the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn 4+ At least two of the following: the positive electrode material of the sodium ion battery includes sodium ferric sulfate, a carbon material and a plurality of metal ions, the carbon material is dispersed between the sodium ferric sulfate, and the metal ions are doped in the crystal structure of the sodium ferric sulfate.

[0071] Specifically, in some exemplary embodiments, the iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, and a sodium ion battery positive electrode material is prepared using the titanium dioxide byproduct having ferrous sulfate heptahydrate, a layered oxide precursor byproduct having sodium sulfate, and a carbon material as raw materials; wherein at least one of the titanium dioxide byproduct and / or the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ Mg 2+ 、Co 2+ and Mn 4+ .

[0072] Among them, titanium dioxide by-products refer to by-products produced in the process of producing titanium dioxide, mainly including ferrous sulfate heptahydrate and acid solution; in the process of producing lithium / sodium layered oxide positive electrode materials, the lithium / sodium layered oxide positive electrode material precursor will be formed, and then the final lithium / sodium layered oxide positive electrode material is obtained based on the lithium / sodium layered oxide positive electrode material precursor; the layered oxide precursor by-product refers to the waste liquid after co-precipitation and filtration of the lithium / sodium layered oxide positive electrode material precursor in the process of producing lithium / sodium layered oxide positive electrode materials, and the waste liquid contains sodium sulfate; based on the layered oxide precursor by-product and titanium dioxide by-product as raw materials, the sodium ion battery positive electrode material can be prepared, which not only realizes the reuse of various by-products, saves energy consumption and environmental protection costs brought by the treatment of by-products, but also simplifies the preparation process of the sodium ion battery positive electrode material, reduces the preparation difficulty and preparation cost of the sodium ion battery positive electrode material, and at the same time can also make the prepared sodium ion battery positive electrode material have good performance.

[0073] Moreover, under the large output of existing chemical production, the preparation of sodium-ion battery positive electrode materials based on the titanium dioxide by-product and the layered oxide precursor by-product can provide sufficient iron and sodium sources for the preparation of sodium-ion battery positive electrode materials, solving the problem of limited production capacity of sodium-ion battery positive electrode materials.

[0074] Specifically, when the iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, the sodium ion battery positive electrode material prepared using the iron source, the layered oxide precursor byproduct having sodium sulfate and the carbon material as raw materials includes:

[0075] S1, performing a first purification treatment on the titanium dioxide by-product to obtain a first purified solution; the first purification treatment can remove insoluble substances in the titanium dioxide by-product, and the first purified solution includes ferrous sulfate heptahydrate and multiple soluble metal ions, the soluble metal ions including Ni 2+ Mg 2+ and Mn 4+ At least two of the following;

[0076] S2, performing a second purification treatment on the layered oxide precursor by-product to obtain a second purified solution; the second purification treatment can remove ammonia nitrogen in the layered oxide precursor by-product, and the second purified solution includes sodium sulfate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ 、Co 2+ and Mn 4+ At least two of the following;

[0077] S3, mixing and drying the first purified solution, the second purified solution and the carbon material to obtain a positive electrode material precursor;

[0078] S4, granulating the positive electrode material precursor to obtain a precursor pressed material;

[0079] S5, sintering the precursor pressed material and crushing it to obtain the sodium ion battery positive electrode material.

[0080] First, in step S1, the titanium dioxide by-product is a titanium dioxide by-product prepared by a sulfuric acid method. The impurities in the titanium dioxide by-product, except for ferrous sulfate heptahydrate, mainly include insoluble substances and soluble metal ions. Among them, the soluble metal ions are all in the form of sulfates and do not contain other anions that will affect the battery system. In the subsequent synthesis of sodium ferric sulfate, the soluble metal ions can exist in the crystal structure of sodium ferric sulfate in the form of doping, thereby improving the rate and cycle performance of the sodium ion battery positive electrode material. The first purification treatment in step S1 is mainly used to remove insoluble substances, including insoluble titanium dioxide and other insoluble impurities (for example, dust, etc.).

[0081] Specifically, the titanium dioxide by-product is subjected to a first purification treatment to obtain a first purified solution, that is, step S1 includes:

[0082] S11, dissolving the titanium dioxide by-product in deionized water, and dispersing iron powder in the deionized water to obtain a first initial solution;

[0083] S12, mixing the sodium hydroxide solution and the first initial solution until the pH of the first initial solution reaches a first target pH, and filtering to obtain a filtrate;

[0084] S13, mixing sulfuric acid, an antioxidant, and the filtrate until the pH of the filtrate reaches a second target pH, to obtain the first purified solution.

[0085] Compared with traditional processes that recover ferrous sulfate heptahydrate from these by-products and use it as a sewage treatment agent or soil conditioner, which has low added value, or require high-purity purification before it can be used in the battery industry, which results in additional costs, this first purification treatment has lower purification requirements for titanium dioxide by-products, and can further save the energy consumption and environmental protection costs required for the waste treatment of titanium dioxide by-products.

[0086] Among them, in step S11, the titanium dioxide by-product also contains Fe 3+ , or Fe in titanium dioxide by-products 2+ After dissolving in deionized water, it is easily oxidized to Fe 3+ , add iron powder to deionized water, the iron powder plays a reducing role and can be used to reduce the Fe 3+ Reduction to Fe 2+, to increase Fe 2+ In some exemplary embodiments, the titanium dioxide byproduct is dissolved in deionized water at room temperature, and iron powder is added to the solution to reduce the Fe 3+ , stirring for 0.5h~2h, improve the dissolution and dispersion uniformity of titanium dioxide by-products, and also help promote the iron powder to Fe 3+ The first initial solution is obtained by reduction, wherein the iron element in the first initial solution is mainly in the form of divalent iron ions Fe 2+ exists in the form of .

[0087] Specifically, in some exemplary embodiments, the mass percentage between the iron powder and the ferrous sulfate heptahydrate is 0.1% to 1%; it can be understood that the mass percentage between the iron powder and the ferrous sulfate heptahydrate can be any point value between 0.1% and 1%; for example, the mass percentage between the iron powder and the ferrous sulfate heptahydrate can be 0.1%, 0.2%, 0.5%, 0.7%, 0.8%, 1%, etc.; the mass percentage between the iron powder and the ferrous sulfate heptahydrate in the titanium dioxide by-product is within this range, which can provide sufficient iron powder to remove Fe that may exist in the solution. 3+ Effective reduction is beneficial to maintain the Fe 2+ stability, which is beneficial to improving the preparation yield of sodium ion battery positive electrode materials and improving the specific capacity and other properties of sodium ion battery positive electrode materials.

[0088] Specifically, in some exemplary embodiments, the concentration of ferrous sulfate heptahydrate in the first initial solution is 50 g / L to 150 g / L; it is understandable that the concentration of ferrous sulfate heptahydrate in the first initial solution can be any point value between 50 g / L and 150 g / L; illustratively, the concentration of ferrous sulfate heptahydrate in the first initial solution can be 50 g / L, 70 g / L, 80 g / L, 100 g / L, 120 g / L, 150 g / L, etc.; in this way, ferrous sulfate heptahydrate can be fully dissolved in the first initial solution, is not prone to precipitation, and can provide sufficient iron source in the subsequent S3-S5 steps to generate sodium ferric sulfate, thereby improving the preparation accuracy and preparation yield of the sodium ion battery positive electrode material.

[0089] Then, in step S12, the sodium hydroxide solution is used to adjust the pH of the first initial solution, and the pH of the sodium hydroxide solution is 10-13; it can be understood that the pH of the sodium hydroxide solution can be any point value between 10 and 13; illustratively, the pH of the sodium hydroxide solution can be 10, 10.5, 11, 11.7, 12, 13, etc.; in this way, the pH of the first initial solution can be effectively increased, so that some other undesirable cations in the first initial solution are precipitated and removed during the filtration process, which is beneficial to improve the accuracy of the metal ion doping species in the final sodium ion battery positive electrode material and improve the performance of the sodium ion battery positive electrode material; in addition, the sodium ions in the sodium hydroxide solution can also be used as part of the sodium source in the subsequent preparation process, and are ultimately used to form the positive electrode material, thereby improving the capacity of the sodium ion battery positive electrode material.

[0090] Specifically, titanium dioxide by-products also include soluble Ti 2+ , which will have an adverse effect on the performance of the positive electrode material of the sodium ion battery; in the process of dissolving the titanium dioxide by-product in deionized water, Ti 2+ Also dissolved in deionized water, thus existing in the first initial solution, and Ti 2+ The solubility under different pH conditions is different. In step S12, the sodium hydroxide solution can adjust the pH of the first initial solution to the first target pH. Under the first target pH, the Ti in the first initial solution is 2+ A precipitation reaction occurs to form an insoluble titanium precipitate. Sodium hydroxide solution is added to the first initial solution and stirred for 0.2h to 2h to allow Ti 2+ Sufficient precipitation allows titanium precipitation, insoluble matter and residual iron powder to be removed together during the filtration process. The impurity removal process is simple and efficient, and the impurity removal effect is good.

[0091] Specifically, the first target pH is 4.5 to 5. It can be understood that the first target pH can be any point value between 4.5 and 5. For example, the first target pH can be 4.5, 4.55, 4.6, 4.7, 4.8, 4.9, 5, etc. Within the first target pH range, Ti 2+ Effective precipitation occurs to increase Ti 2+ The removal efficiency of Ti 2+ Adverse effects on the performance of the positive electrode material of the sodium ion battery; and the first target pH is Fe 2+ The boundary pH of precipitation can effectively avoid Fe 2+ Precipitation occurs, which improves the solution stability of the first initial solution and the filtrate, and is beneficial to improving the preparation yield and preparation reliability of the final sodium ion battery positive electrode material.

[0092] Specifically, in step S12, the insoluble substances in the titanium dioxide by-product removed by filtration include titanium dioxide, and the mass proportion of titanium dioxide in the titanium dioxide by-product is less than the first mass proportion, and the first mass proportion is 0.7% to 1.3%; it can be understood that the first mass proportion can be any point value between 0.7% and 1.3%, which is not enumerated here; in this way, it is convenient to remove titanium dioxide by filtration, and it is not easy to affect the performance of the sodium ion battery positive electrode material; in some preferred embodiments, the first mass proportion is 1%, that is, the mass proportion of titanium dioxide in the titanium dioxide by-product is less than 1%; in addition, the insoluble substances in the titanium dioxide by-product also include insoluble impurities, such as dust, particles, etc., and the mass proportion of insoluble impurities in the titanium dioxide by-product is less than 1%, which can be effectively removed by filtration.

[0093] Then, in step S13, sulfuric acid is used to adjust the pH of the filtrate or the first purified solution, and sulfuric acid is added to the filtrate so that the pH of the filtrate reaches a second target pH, and the second target pH is 2 to 3.5; it can be understood that the second target pH can be any point value between 2 and 3.5; for example, the second target pH can be 2, 2.1, 2.5, 2.8, 3, 3.2, 3.5, etc.; within the second target pH range, Fe 2+ Precipitation occurs, effectively maintaining the stability of the first purified solution, improving the stability and reliability of the preparation method, and being beneficial to improving the preparation accuracy and preparation yield of the sodium ion battery positive electrode material.

[0094] Among them, the mass proportion of various soluble metal ions retained in the first purified solution in the titanium dioxide by-product is less than the second mass proportion, that is, Ni 2+ Mg 2+ and Mn 4+ The mass proportion of the total mass of the titanium dioxide by-product is less than the second mass proportion, and the second mass proportion is 0.7% to 1.3%; it can be understood that the second mass proportion can be any point value between 0.7% and 1.3%, which is not enumerated here; in this way, the desired content of metal ions can be doped into the crystal structure of sodium ferric sulfate in the subsequent preparation steps, greatly improving the specific capacity, rate performance and cycle performance of the sodium ion battery positive electrode material; in some preferred embodiments, the second mass proportion is 1%, that is, Ni 2+ Mg 2+ and Mn 4+ The total mass of titanium dioxide by-products accounts for less than 1%.

[0095] Specifically, in some exemplary embodiments, the antioxidant in step S13 includes at least one of ascorbic acid, oxalic acid and citric acid, which has excellent antioxidant properties; in the process of mixing sulfuric acid, antioxidant and filtrate, the antioxidant can effectively prevent the divalent iron ions (Fe2+ ) is oxidized, which is beneficial to maintaining the stability of the filtrate and the first purified solution, and further beneficial to improving the rate performance and cycle performance of the prepared sodium ion battery positive electrode material.

[0096] Specifically, in some exemplary embodiments, the mass percentage between the antioxidant and ferrous sulfate heptahydrate is 0.1% to 3%; it can be understood that the mass percentage between the antioxidant and ferrous sulfate heptahydrate can be any point value between 0.1% and 3%; for example, the mass percentage between the antioxidant and ferrous sulfate heptahydrate can be 0.1%, 0.2%, 0.5%, 1.0%, 1.5%, 2%, 2.5%, 3%, etc.; thus, it can effectively prevent Fe 2+ It is oxidized, improving the electrical properties of sodium ion battery positive electrode materials such as specific capacity and cycle stability.

[0097] Through the first purification process in step S1, the insoluble matter, the iron powder remaining in the process and the Ti 2+ was effectively removed, and the first purified solution obtained mainly included ferrous sulfate heptahydrate and Ni 2+ Mg 2+ and Mn 4+ The metal ion impurities can improve the performance of the final sodium ion battery positive electrode material in the form of doping; and the first purified solution also includes a small amount of Na introduced by the sodium hydroxide solution. + , which can be used as part of the sodium source to generate sodium ferric sulfate, thereby increasing the capacity of the positive electrode material of the sodium ion battery; the first purified solution also includes an antioxidant to further maintain the stability of ferrous sulfate heptahydrate, which is beneficial to improving the reliability of the preparation method and the preparation yield of the positive electrode material of the sodium ion battery.

[0098] Specifically, the second purification treatment of the layered oxide precursor by-product to obtain a second purified solution, that is, step S2, includes:

[0099] S21, deammoniating the layered oxide precursor byproduct to obtain a second initial solution;

[0100] S22, mixing sulfuric acid and the second initial solution until the pH of the second initial solution reaches a third target pH, to obtain the second purified solution.

[0101] Compared with the existing waste liquid treatment process including deammoniation recovery, precipitation, and MVR evaporation to obtain high-purity sodium sulfate powder (i.e., "sodium sulfate"), the second purification treatment has lower purification requirements for the layered oxide precursor by-product, which is conducive to reducing the purification difficulty and purification cost, further reducing the energy consumption and environmental problems caused by the recycling of by-products, and reducing the cost of waste treatment and recycling; and, compared with the process of preparing sodium iron sulfate positive electrode materials with high-purity raw materials, it can greatly reduce the production cost of the positive electrode material; that is, while improving the recycling rate of industrial waste and reducing the energy consumption and environmental protection costs of waste treatment, it can also use a relatively simple process to prepare positive electrode materials with relatively good rate performance and cycle performance using industrial waste as raw materials.

[0102] In step S2, the layered oxide precursor by-product mainly includes sodium sulfate, and in the process of preparing the layered oxide precursor by-product, the raw materials used are all sulfates, so that the anions in the layered oxide precursor by-product are all SO4 2- , there are no other anions that affect the battery system, and a small amount of Ni 2+ 、Co 2+ and Mn 4+ Metal ion impurities can also be used as doping elements to improve the performance of sodium ion battery positive electrode materials. The second purification treatment is used to remove ammonia nitrogen in the layered oxide precursor by-products and regulate the pH of the second purified solution.

[0103] Specifically, the concentration of sodium sulfate in the layered oxide precursor by-product is 50 g / L to 200 g / L; it can be understood that the concentration of sodium sulfate in the layered oxide precursor by-product can be any point value between 50 g / L and 200 g / L; illustratively, the concentration of sodium sulfate in the layered oxide precursor by-product can be 50 g / L, 70 g / L, 100 g / L, 120 g / L, 150 g / L, 180 g / L, 200 g / L, etc.; in this way, a rich sodium source can be provided to generate sodium ferric sulfate, thereby increasing the yield of sodium ion battery positive electrode materials.

[0104] Specifically, in step S21, the pH of the layered oxide precursor by-product is greater than 12; it is understood that the pH of the layered oxide precursor by-product can be any value greater than 12, which is not enumerated here; the ammonia nitrogen content in the layered oxide precursor by-product is 5g / L to 10g / L; it is understood that the ammonia nitrogen content in the layered oxide precursor by-product can be any value between 5g / L and 10g / L, which is not enumerated here; the deamination treatment is used to remove ammonia nitrogen in the layered oxide precursor by-product, which can be carried out by a distillation tower. Deamination treatment is performed to obtain a second initial solution that does not contain ammonia. In an alkaline environment, it is beneficial to remove ammonia by distillation in step S21, and the discharge of ammonia during the removal process promotes the reversible reaction between ammonium ions and ammonia in the direction of generating ammonia, further removing ammonia nitrogen in the layered oxide precursor by-products, and improving the deamination efficiency and ammonia nitrogen removal rate; in addition, the discharged ammonia can be converted into ammonia water after absorption, realizing the recovery of by-product ammonia, which can be further used for pH control in other precursor preparation processes, with a high recovery rate and greatly reduced pollution.

[0105] Specifically, the content of various soluble metal ions remaining in the second purified solution in the layered oxide precursor by-product is 75 mg / L to 130 mg / L, i.e., Ni 2+ 、Co 2+ and Mn 4+ The content of Ni in the layered oxide precursor by-product is 75mg / L to 130mg / L; it is understandable that Ni 2+ 、Co 2+ and Mn 4+ The content of the layered oxide precursor by-product can be any value between 75 mg / L and 130 mg / L, which is not enumerated here; in this way, the desired content of metal ions can be doped into the crystal structure of sodium iron sulfate in the subsequent preparation steps, greatly improving the specific capacity, rate performance and cycle performance of the sodium ion battery positive electrode material; in some specific embodiments, Ni 2+ 、Co 2+ and Mn 4+ The content in the layered oxide precursor by-product may be about 100 mg / L.

[0106] Specifically, in step S22, sulfuric acid is added to the second initial solution to adjust the pH of the second initial solution or the second purified solution to a third target pH, and the third target pH is 6.7-7.0; it can be understood that the third target pH can be any point value between 6.7 and 7.0; illustratively, the third target pH can be 6.7, 6.75, 6.8, 6.9, 7.0, etc.; within the third target pH range, the cations in the second initial solution can be effectively prevented from precipitating, the stability of the second purified solution can be effectively maintained, and the stability and reliability of the preparation method of the sodium ion battery positive electrode material can be improved, which is beneficial to improving the preparation accuracy and preparation yield of the sodium ion battery positive electrode material.

[0107] Then, after obtaining the first purified solution in step S1 and the second purified solution in step S2, a positive electrode material for a sodium ion battery is prepared based on the first purified solution, the second purified solution and the carbon material, and a positive electrode material precursor is prepared in step S3. Then, in step S4, the positive electrode material precursor is granulated to obtain a precursor pressed material. The precursor pressed material is a block structure with a certain shape and not loose, which is convenient for subsequent sintering and improves the sintering effect. Finally, in step S5, the precursor pressed material is granulated in a preset atmosphere environment. The sodium ion battery cathode material is sintered and crushed to obtain the sodium ion battery cathode material. The preparation method of the sodium ion battery cathode material has low overall cost and low preparation difficulty, and has low purity requirements for the sodium ferric sulfate heptahydrate and sodium sulfate raw materials. It can directly realize the preparation of battery-grade sodium ion battery cathode material from industrial waste, greatly saving the energy consumption and environmental protection costs caused by the waste coarse particles of titanium dioxide by-products and layered oxide precursor by-products, and also greatly simplifying the production process of the sodium ion battery cathode material, thereby reducing the production cost of the sodium ion battery cathode material.

[0108] Specifically, in some exemplary embodiments, the first purified solution, the second purified solution, and the carbon material are mixed and dried to obtain a cathode material precursor, that is, step S3 includes:

[0109] According to a preset x / y value, the first purified solution, the second purified solution, and the carbon material are mixed to obtain a precursor solution;

[0110] The precursor solution is dried to obtain the positive electrode material precursor.

[0111] Specifically, in some other exemplary embodiments, the first purified solution, the second purified solution, and the carbon material are mixed and dried to obtain a cathode material precursor, that is, step S3 includes:

[0112] According to a preset x / y value, the first purified solution and the second purified solution are mixed to obtain a precursor solution;

[0113] Drying the precursor solution to obtain a precursor solid;

[0114] The carbon material and the precursor solid are mixed and ball milled to obtain the positive electrode material precursor.

[0115] Specifically, in other exemplary embodiments, the first purified solution, the second purified solution, and the carbon material are mixed and dried to obtain a positive electrode material precursor, that is, step S3 includes:

[0116] According to a preset x / y value, the first purified solution, the second purified solution, and the carbon material are mixed to obtain a precursor solution;

[0117] Drying the precursor solution to obtain a precursor solid;

[0118] The carbon material and the precursor solid are mixed and ball milled to obtain the positive electrode material precursor.

[0119] That is, in step S3, the carbon material can be added to the precursor solution during the mixing of the first purified solution and the second purified solution; or the carbon material can be dry-mixed with the precursor solid after the first purified solution and the second purified solution are mixed and dried; or the carbon material can be added in both of the above steps. The preparation method of the sodium ion battery positive electrode material is flexible and has a wide range of applications.

[0120] In some exemplary embodiments, the obtained precursor solution is a uniform non-stratified solution. After the first purified solution and the second purified solution (or further including carbon material) are mixed and stirred, sand milling treatment may be performed to improve the uniformity of the precursor solution.

[0121] Specifically, in some exemplary embodiments, in the first purified solution and the second purified solution for preparing the positive electrode material precursor in step S3, the preset x / y value between the sodium element and the iron element is 1 to 2. During the preparation process, the first purified solution and the second purified solution can be subjected to ICP testing to obtain the iron element content and the sodium element content. Based on the measured iron element content and the sodium element content, the mass of the first purified solution and the second purified solution, as well as the mass of the carbon material to be added, are determined to prepare the positive electrode material precursor; it can be understood that the preset x / y value between the sodium element and the iron element is 1 to 2. Assume that the x / y value can be any point value between 1 and 2; illustratively, the preset x / y value between the sodium element and the iron element can be 1, 1.1, 1.2, 1.5, 1.7, 1.8, 1.9, 2, etc.; in this way, the specific capacity of the prepared sodium ion battery positive electrode material can be improved, and the rate performance and cycle performance of the sodium ion battery positive electrode material can be improved; further, in some exemplary embodiments, the preset x / y value between the sodium element and the iron element is 1.2 to 1.8; in some preferred embodiments, the preset x / y value between the sodium element and the iron element is 1.3 to 1.7.

[0122] Specifically, in some exemplary embodiments, in the process of mixing the first purified solution, the second purified solution, and the carbon material according to a preset x / y value to obtain a precursor solution, the mass of the carbon material is 0.1% to 5% of the total mass of ferrous sulfate heptahydrate and sodium sulfate; it can be understood that the mass of the carbon material can be any point value between 0.1% and 5% of the total mass of ferrous sulfate heptahydrate and sodium sulfate; illustratively, the mass of the carbon material can be 0.1%, 0.5%, 1%, 3%, 5%, etc. of the total mass of ferrous sulfate heptahydrate and sodium sulfate; in this way, the conductivity of the prepared sodium ion battery positive electrode material can be effectively improved, and the rate performance and cycle performance of the sodium ion battery positive electrode material can be improved.

[0123] Specifically, in the process of drying the precursor solution, the drying treatment includes at least one of freeze drying, evaporative drying, spray drying and steam mechanical recompression (MVR) to effectively remove moisture from the precursor solution; in some exemplary embodiments, the precursor solution is spray dried, the inlet air temperature is 180°C to 220°C, and the outlet air temperature is 90°C to 120°C; it can be understood that the inlet air temperature can be any point value between 180°C and 220°C, and the outlet air temperature can be any point value between 90°C and 120°C, which are not enumerated here, and can effectively remove moisture from the precursor solution.

[0124] Specifically, in some exemplary embodiments, in the process of mixing the carbon material and the precursor solid matter and ball milling to obtain the positive electrode material precursor, the mass of the carbon material is 0.1% to 5% of the mass of the precursor solid matter; it can be understood that the mass of the carbon material can be any point value between 0.1% and 5% of the mass of the precursor solid matter, which is not enumerated here; in this way, the conductivity of the prepared sodium ion battery positive electrode material can be effectively improved, and the rate performance and cycle performance of the sodium ion battery positive electrode material can be improved.

[0125] Specifically, the ball milling treatment can include at least one of planetary ball milling, vibrating ball milling and stirring ball milling. Correspondingly, ball milling can be performed by at least one ball milling equipment selected from the group consisting of a planetary ball mill, a vibrating ball mill and a stirring ball mill. This can effectively improve the mixing uniformity of the precursor solid matter and the carbon material, reduce the particle size of the positive electrode material precursor, and help improve the sintering effect of the subsequent sintering step, thereby improving the preparation yield of the positive electrode material for sodium ion batteries.

[0126] Specifically, in some exemplary embodiments, during the ball milling process, the ball-to-material ratio of the total mass of the precursor solid and the carbon material to the ball milling medium is 10:1 to 50:1, and the ball milling time is 0.2h to 5h; it can be understood that the ball-to-material ratio of the total mass of the precursor solid and the carbon material to the ball milling medium can be any point value between 10:1 and 50:1, and the ball milling time can be any point value between 0.2h and 5h, which are no longer enumerated here; in this way, the dispersion and uniformity of the carbon material and the precursor solid can be effectively improved, and the particle size of the positive electrode material precursor can be reduced, which is beneficial to improving the subsequent doping effectiveness and doping uniformity of multiple metal ions in the sodium iron sulfate crystal structure, and is also beneficial to improving the sintering effect in the subsequent sintering process, improving the molding accuracy of the sodium ion battery positive electrode material, and improving the preparation stability and preparation reliability, thereby helping to improve the performance of the prepared sodium ion battery positive electrode material.

[0127] Next, in the granulation process of step S4, granulation can be performed by granulation equipment such as a tablet press, a roller granulator, and a press, and the target density of the precursor pressed material is 2.0 g / cm 3 ~3.0g / cm 3 It is understood that the target density of the precursor pressed material can be 2.0g / cm 3 ~3.0g / cm 3 For example, the target density of the precursor pressed material can be 2.0 g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.5g / cm 3 , 2.7g / cm 3 , 3.0g / cm3 In this way, the contact tightness between the materials in the precursor pressed material can be effectively improved, which is beneficial to improving the sintering effect, improving the morphology accuracy and performance of the sodium ion battery positive electrode material, and when using a roller kiln for sintering, it can also increase the production capacity of the kiln, further improving the economy of the preparation method of the sodium ion battery positive electrode material.

[0128] Specifically, in step S5, during the sintering process of the precursor pressed material, the preset atmosphere environment includes nitrogen, argon, etc., to effectively play a protective role and improve the sintering effect. The sintering temperature is 350°C to 400°C, and the sintering time is 4h to 15h. It can be understood that the sintering temperature can be any point value between 350°C and 400°C, and the sintering time can be any point value between 4h and 15h. For example, the sintering temperature can be 350°C, 360°C, 370°C, 375°C, 380°C, 390°C, 400°C, etc., and the sintering time can be 4h, 6h, etc. h, 8h, 9h, 10h, 11h, 13h, 15h, etc.; the sintering process produces a pure solid-phase reaction, which can make the iron element and the sodium element in the precursor pressed material fully react to form sodium ferric sulfate, and can also promote the doping of various metal ion impurities into the crystal structure of sodium ferric sulfate. The sintering effect is good, which is beneficial to improving the specific capacity and other properties of the sodium ion battery positive electrode material. In addition, crushing after sintering can also improve the convenience of using the sodium ion battery positive electrode material in sodium ion batteries; in some preferred embodiments, the sintering temperature is 350°C to 370°C, and the sintering time is 8h to 12h.

[0129] On the other hand, an embodiment of the present application further provides a sodium ion battery, comprising the sodium ion battery positive electrode material as described above, or comprising the sodium ion battery positive electrode material prepared by the preparation method of the sodium ion battery positive electrode material as described above, so that the sodium ion battery has good rate performance and cycle performance, and the preparation process is simple and the preparation difficulty is low, realizing the preparation process flow from industrial by-products to sodium ion batteries, greatly reducing the energy consumption and environmental protection costs brought about by industrial waste treatment, and using industrial by-products as raw materials also reduces the preparation cost of sodium ion batteries.

[0130] The following describes the embodiments of the present application in combination with the above technical solutions.

[0131] Example 1

[0132] like Figure 1 As shown, the positive electrode material of the sodium ion battery of this embodiment is prepared by the following steps:

[0133] 1. Dissolve the titanium dioxide byproduct in deionized water and disperse the iron powder in deionized water, and stir for 0.5 h to obtain a first initial solution; wherein the mass of the iron powder is 0.5% of the mass of ferrous sulfate heptahydrate, and the concentration of ferrous sulfate heptahydrate in the first initial solution is 120 g / L;

[0134] 2. Mixing a sodium hydroxide solution having a pH of 12 with the first initial solution until the pH of the first initial solution reaches 4.5, stirring for 1 hour, and then filtering to obtain a filtrate;

[0135] 3. Sulfuric acid, ascorbic acid and the filtrate were mixed until the pH of the filtrate reached 3.0 to obtain a first purified solution. ICP results of the first purified solution showed that the iron content was 23.7% and the sodium content was 1.3%.

[0136] 4. Deaminate the layered oxide precursor byproduct to obtain a second initial solution, and mix sulfuric acid with the second initial solution until the pH of the second initial solution reaches 7.0 to obtain a second purified solution. ICP results of the second purified solution showed a sodium content of 3.12%;

[0137] 5. Based on the above ICP results, the first purified solution, the second purified solution, and the carbon nanotubes were mixed at a preset x / y ratio of 1.5, stirred evenly, and then sand-milled to obtain a precursor solution; wherein the mass of the carbon nanotubes was 3% of the total mass of ferrous sulfate heptahydrate and sodium sulfate in the solution;

[0138] 6. The precursor solution is spray dried with an inlet air temperature of 200°C and an outlet air temperature of 110°C to obtain a gray-black precursor solid;

[0139] 7. The precursor solid and carbon nanotubes were mixed in a mass ratio of 98:2, and ball milled in a vibrating ball mill at a ball-to-material ratio of 10:1 for 2 h to obtain a cathode material precursor;

[0140] 8. Granulate the cathode material precursor to obtain a compacted precursor material;

[0141] 9. The precursor pressed material is placed in a roller kiln and sintered in a nitrogen atmosphere at a sintering temperature of 360°C for 10 hours, and then crushed to obtain a sodium ion battery positive electrode material.

[0142] Example 2

[0143] The sodium ion battery positive electrode material of this embodiment is prepared by the following steps:

[0144] 1. Dissolve the titanium dioxide byproduct in deionized water and disperse the iron powder in deionized water, and stir for 0.5 h to obtain a first initial solution; wherein the mass of the iron powder is 0.7% of the mass of ferrous sulfate heptahydrate, and the concentration of ferrous sulfate heptahydrate in the first initial solution is 150 g / L;

[0145] 2. Mixing a sodium hydroxide solution having a pH of 12 with the first initial solution until the pH of the first initial solution reaches 4.7, stirring for 1 hour, and then filtering to obtain a filtrate;

[0146] 3. Sulfuric acid, ascorbic acid and the filtrate were mixed until the pH of the filtrate reached 3.0 to obtain a first purified solution. ICP results of the first purified solution showed that the iron content was 28.7% and the sodium content was 1.6%.

[0147] 4. Deaminate the layered oxide precursor byproduct to obtain a second initial solution, and mix sulfuric acid with the second initial solution until the pH of the second initial solution reaches 6.8 to obtain a second purified solution. ICP results of the second purified solution showed a sodium content of 3.14%;

[0148] 5. Based on the above ICP results, the first purified solution, the second purified solution, and the carbon nanotubes were mixed according to a preset x / y ratio of 1.6, stirred evenly, and then sand-milled to obtain a precursor solution; wherein the mass of the carbon nanotubes was 2% of the total mass of ferrous sulfate heptahydrate and sodium sulfate in the solution;

[0149] 6. The precursor solution is spray dried with an inlet air temperature of 200°C and an outlet air temperature of 110°C to obtain a gray-black precursor solid;

[0150] 7. The precursor solid and carbon nanotubes were mixed in a mass ratio of 98:2, and ball milled in a vibrating ball mill at a ball-to-material ratio of 10:1 for 2 h to obtain a cathode material precursor;

[0151] 8. Granulate the cathode material precursor to obtain a compacted precursor material;

[0152] 9. The precursor pressed material is placed in a roller kiln and sintered in a nitrogen atmosphere at a sintering temperature of 360°C for 10 hours, and then crushed to obtain a sodium ion battery positive electrode material.

[0153] Example 3

[0154] The sodium ion battery positive electrode material of this embodiment is prepared by the following steps:

[0155] 1. Dissolve the titanium dioxide byproduct in deionized water and disperse the iron powder in deionized water, and stir for 0.5 h to obtain a first initial solution; wherein the mass of the iron powder is 0.3% of the mass of ferrous sulfate heptahydrate, and the concentration of ferrous sulfate heptahydrate in the first initial solution is 100 g / L;

[0156] 2. Mixing a sodium hydroxide solution having a pH of 12 with the first initial solution until the pH of the first initial solution reaches 4.5, stirring for 1 hour, and then filtering to obtain a filtrate;

[0157] 3. Sulfuric acid, ascorbic acid and the filtrate were mixed until the pH of the filtrate reached 2.5 to obtain a first purified solution. ICP results of the first purified solution showed that the iron content was 18.7% and the sodium content was 0.9%.

[0158] 4. Deaminate the layered oxide precursor byproduct to obtain a second initial solution, and mix sulfuric acid with the second initial solution until the pH of the second initial solution reaches 7.0 to obtain a second purified solution. ICP results of the second purified solution showed a sodium content of 3.10%.

[0159] 5. Based on the above ICP results, the first purified solution, the second purified solution, and the carbon nanotubes were mixed according to a preset x / y ratio of 1.35, stirred evenly, and then sand-milled to obtain a precursor solution; wherein the mass of the carbon nanotubes was 2% of the total mass of ferrous sulfate heptahydrate and sodium sulfate in the solution;

[0160] 6. The precursor solution is spray dried with an inlet air temperature of 200°C and an outlet air temperature of 110°C to obtain a gray-black precursor solid;

[0161] 7. The precursor solid and carbon nanotubes were mixed in a mass ratio of 98:2, and ball milled in a vibrating ball mill at a ball-to-material ratio of 10:1 for 2 h to obtain a cathode material precursor;

[0162] 8. Granulate the cathode material precursor to obtain a compacted precursor material;

[0163] 9. The precursor pressed material is placed in a roller kiln and sintered in a nitrogen atmosphere at a sintering temperature of 360°C for 10 hours, and then crushed to obtain a sodium ion battery positive electrode material.

[0164] Example 4

[0165] The sodium ion battery positive electrode material of this embodiment is prepared by the following steps:

[0166] 1. Dissolve the titanium dioxide byproduct in deionized water and disperse the iron powder in deionized water, and stir for 0.5 h to obtain a first initial solution; wherein the mass of the iron powder is 0.5% of the mass of ferrous sulfate heptahydrate, and the concentration of ferrous sulfate heptahydrate in the first initial solution is 120 g / L;

[0167] 2. Mixing a sodium hydroxide solution having a pH of 12 with the first initial solution until the pH of the first initial solution reaches 4.5, stirring for 1 hour, and then filtering to obtain a filtrate;

[0168] 3. Sulfuric acid, ascorbic acid and the filtrate were mixed until the pH of the filtrate reached 3.0 to obtain a first purified solution; ICP results of the first purified solution showed that the iron content was 23.9% and the sodium content was 1.1%;

[0169] 4. Deaminate the layered oxide precursor byproduct to obtain a second initial solution, and mix sulfuric acid with the second initial solution until the pH of the second initial solution reaches 7.0 to obtain a second purified solution. ICP results of the second purified solution showed a sodium content of 3.16%;

[0170] 5. Based on the above ICP results, according to the preset x / y value = 1.5, the first purified solution and the second purified solution were mixed and stirred to obtain a precursor solution;

[0171] 6. The precursor solution is spray dried with an inlet air temperature of 200°C and an outlet air temperature of 110°C to obtain a gray-black precursor solid;

[0172] 7. The precursor solid and carbon nanotubes were mixed in a mass ratio of 97:3, and ball milled in a vibrating ball mill at a ball-to-material ratio of 10:1 for 2 h to obtain a cathode material precursor;

[0173] 8. Granulate the cathode material precursor to obtain a compacted precursor material;

[0174] 9. The precursor pressed material is placed in a roller kiln and sintered in a nitrogen atmosphere at a sintering temperature of 360°C for 10 hours, and then crushed to obtain a sodium ion battery positive electrode material.

[0175] Example 5

[0176] The sodium ion battery positive electrode material of this embodiment is prepared by the following steps:

[0177] 1. Dissolve the titanium dioxide byproduct in deionized water and disperse the iron powder in deionized water, and stir for 0.5 h to obtain a first initial solution; wherein the mass of the iron powder is 0.4% of the mass of ferrous sulfate heptahydrate, and the concentration of ferrous sulfate heptahydrate in the first initial solution is 120 g / L;

[0178] 2. Mixing a sodium hydroxide solution having a pH of 12 with the first initial solution until the pH of the first initial solution reaches 4.5, stirring for 1 hour, and then filtering to obtain a filtrate;

[0179] 3. Sulfuric acid, ascorbic acid and the filtrate were mixed until the pH of the filtrate reached 3.0 to obtain a first purified solution; ICP results of the first purified solution showed that the iron content was 24.0% and the sodium content was 1.0%;

[0180] 4. Deaminate the layered oxide precursor byproduct to obtain a second initial solution, and mix sulfuric acid with the second initial solution until the pH of the second initial solution reaches 7.0 to obtain a second purified solution. ICP results of the second purified solution showed a sodium content of 3.17%;

[0181] 5. Based on the above ICP results, the first purified solution, the second purified solution, and the carbon nanotubes were mixed at a preset x / y ratio of 1.5, stirred evenly, and then sand-milled to obtain a precursor solution; wherein the mass of the carbon nanotubes was 3% of the total mass of ferrous sulfate heptahydrate and sodium sulfate in the solution;

[0182] 6. The precursor solution is spray-dried with an inlet air temperature of 200°C and an outlet air temperature of 110°C to obtain a gray-black cathode material precursor;

[0183] 7. Granulate the cathode material precursor to obtain a compacted precursor material;

[0184] 8. The precursor pressed material is placed in a roller kiln and sintered in a nitrogen atmosphere at a sintering temperature of 360°C for 10 hours, and then crushed to obtain a sodium ion battery positive electrode material.

[0185] Example 6

[0186] The difference between this embodiment and embodiment 1 is that, in step 5, the preset x / y value is 1.8; the rest is the same as embodiment 1.

[0187] Example 7

[0188] The difference between this embodiment and embodiment 1 is that, in step 5, the preset x / y value is 1.2; the rest is the same as embodiment 1.

[0189] Comparative Example 1

[0190] The difference between this comparative example and Example 1 is that, before step 5, high-purity raw materials are used for preparation. The sodium ion battery positive electrode material of this comparative example is prepared by the following steps:

[0191] 1. Disperse high-purity ferrous sulfate heptahydrate (ferrous sulfate heptahydrate content > 99.8%, impurity element content less than 100 ppm) in deionized water at a concentration of 120 g / L. Add ascorbic acid (1% by mass of ferrous sulfate heptahydrate) and stir for 0.5 h to obtain a clear green first solution. The ICP results of the first solution show that the iron content is 24.2%.

[0192] 2. Disperse high-purity sodium sulfate (sodium sulfate content > 99.9%, impurity element content less than 100 ppm) in deionized water and stir for 1 hour to obtain a second solution; the sodium sulfate concentration in the second solution is 100 g / L, and the ICP result of the second solution shows that the sodium content is 3.24%;

[0193] 3. Based on the above ICP results, the first solution, the second solution, and the carbon nanotubes were mixed at a preset x / y ratio of 1.5, stirred evenly, and then sand-milled to obtain a precursor solution; wherein the mass of the carbon nanotubes was 3% of the total mass of ferrous sulfate heptahydrate and sodium sulfate in the solution;

[0194] 6. The precursor solution is spray dried with an inlet air temperature of 200°C and an outlet air temperature of 110°C to obtain a gray-black precursor solid;

[0195] 7. The precursor solid and carbon nanotubes were mixed in a mass ratio of 98:2, and ball milled in a vibrating ball mill at a ball-to-material ratio of 10:1 for 2 h to obtain a cathode material precursor;

[0196] 8. Granulate the cathode material precursor to obtain a compacted precursor material;

[0197] 9. The precursor pressed material is placed in a roller kiln and sintered in a nitrogen atmosphere at a sintering temperature of 360°C for 10 hours, and then crushed to obtain a sodium ion battery positive electrode material.

[0198] Comparative Example 2

[0199] The difference between this comparative example and Example 1 is that iron powder is not added in step 1, and sodium hydroxide solution is not added in step 2; the rest is the same as Example 1.

[0200] Comparative Example 3

[0201] The difference between this comparative example and Example 1 is that, in step 5, the preset x / y value is 2.2; the rest is the same as Example 1.

[0202] Comparative Example 4

[0203] The difference between this embodiment and embodiment 1 is that, in step 5, the preset x / y value is 0.9; the rest is the same as embodiment 1.

[0204] Table 1 Test results of discharge specific capacity of sodium ion battery positive electrode materials in Examples and Comparative Examples

[0205]

[0206] Table 2 Test results of impurity element content in sodium ion battery positive electrode materials in some examples and some comparative examples

[0207]

[0208] As shown in Table 1, compared with the sodium ion battery positive electrode material prepared using high-purity raw materials in Comparative Example 1, the sodium ion battery positive electrode materials prepared in Examples 1-7 of the present application all have good discharge specific capacity; further, the value of x / y in Examples 1-5 is within the range of 1.3 to 1.7, and the discharge specific capacity is greater than or equal to 92.8 mAh / g, especially in Examples 1-3. The discharge specific capacity reached 95.3 mAh / g, 94.8 mAh / g and 95.9 mAh / g, respectively, which is very close to the specific capacity of 95.1 mAh / g in Comparative Example 1. That is, the sodium ion battery positive electrode material prepared by the preparation method of the sodium ion battery positive electrode material provided by the present application has a discharge specific capacity comparable to that of the positive electrode material prepared based on high-purity raw materials.

[0209] In the sodium ion battery positive electrode material without the first purification treatment in Comparative Example 2, as shown in Table 2, a large amount of titanium ions remain during the preparation process, resulting in a significant decrease in the discharge specific capacity of the prepared sodium ion battery positive electrode material. In Example 1, the titanium ions remain less, and the effect on the performance of the sodium ion battery positive electrode material is almost negligible, while other metal ions (Ni 2+ Mg 2+ 、Co 2+ and Mn 4+ ) makes the sodium ion battery positive electrode material have good discharge specific capacity, rate performance and cycle performance; and the value of x / y in Comparative Examples 3-4 exceeds the range of 1 to 2, resulting in a significant decrease in the discharge specific capacity of the sodium ion battery positive electrode material in Comparative Examples 3-4, while in the embodiments of the present application, the values of x / y are all within the range of 1 to 2, so that the discharge specific capacity of the sodium ion battery positive electrode material is greater than 90 mAh / g.

[0210] In addition, if Figure 2 As shown, according to the rate performance comparison data of Example 1 and Comparative Example 1, it can be seen that after metal ion doping, although the capacity of the sodium ion battery positive electrode material in Example 1 has decreased to a certain extent, the capacity retention rate at high rate is effectively improved, making the sodium ion battery positive electrode material suitable for high rate application scenarios, and expanding the scope of application of the sodium ion battery positive electrode material.

[0211] It can be seen that compared with the traditional process based on high-purity raw material preparation, the sodium ion battery positive electrode material and preparation method of the present application can realize the preparation process of sodium ion battery positive electrode material from industrial waste such as titanium dioxide by-products and layered oxide precursor by-products to batteries. On the one hand, it saves the energy consumption and environmental protection costs brought about by-product recovery and waste treatment. On the other hand, a sodium ion battery positive electrode material with better performance can be further obtained by simple purification treatment. The purification requirements are relatively low, which greatly simplifies the production process of the sodium ion battery positive electrode material. The large amount of by-products and the easy availability of by-products also remove the production capacity constraints, further reducing the production cost of the sodium ion battery positive electrode material. At the same time, it avoids the risk of a significant decline in the performance of the sodium ion battery positive electrode material, so that the prepared sodium ion battery positive electrode material has a specific capacity, rate performance and cycle performance similar to that of the high-purity positive electrode material.

[0212] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0213] What is described above are only some embodiments of the present application and are not intended to limit the present application. Those skilled in the art should understand that the present application may be subject to various changes and improvements, and any modifications, equivalent substitutions, and improvements made in accordance with the present application shall fall within the scope of protection required by the present application.

Claims

1. A sodium ion battery cathode material, characterized in that The sodium ion battery positive electrode material includes sodium ferric sulfate, carbon material and multiple metal ions, the carbon material is dispersed between the sodium ferric sulfate, and the metal ions are doped in the crystal structure of the sodium ferric sulfate; The sodium ion battery positive electrode material is prepared from an iron source, a layered oxide precursor byproduct having sodium sulfate, and a carbon material as raw materials; the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn 4+ The iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, and the titanium dioxide byproduct includes metal ions, and the metal ions include Ni 2+ Mg 2+ and Mn 4+ ; The chemical formula of the sodium ion battery positive electrode material is Na x Fe y Ni a Co b Mn c Mg d (SO4) z @C, where 1≤x / y≤2, (a+b+c+d) / y≤0.

1.

2. The sodium ion battery positive electrode material according to claim 1, characterized in that The sodium ion battery positive electrode material is obtained by performing a first purification treatment on a titanium dioxide byproduct to obtain a first purified solution, performing a second purification treatment on a layered oxide precursor byproduct to obtain a second purified solution, mixing the first purified solution, the second purified solution and a carbon material, drying them, and granulating and sintering them; The first purification process can remove insoluble substances in the titanium dioxide by-product, and the first purification solution includes ferrous sulfate heptahydrate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ Mg 2+ and Mn 4+ ; The second purification treatment can remove ammonia nitrogen in the layered oxide precursor byproduct; the second purification solution includes sodium sulfate and a plurality of soluble metal ions, the soluble metal ions including Ni 2+ 、Co 2+ and Mn 4+ .

3. The sodium ion battery positive electrode material according to claim 2, characterized in that The first purified solution and the second purified solution are mixed by measuring the iron content and the sodium content in the first purified solution, measuring the sodium content in the second purified solution, and according to a preset x / y value between the sodium element and the iron element; wherein 1.2≤x / y≤1.

8.

4. A method for preparing a positive electrode material for a sodium ion battery, characterized in that: The sodium ion battery positive electrode material is prepared by using an iron source, a layered oxide precursor byproduct having sodium sulfate and a carbon material as raw materials; the layered oxide precursor byproduct includes metal ions, and the metal ions include Ni 2+ 、Co 2+ and Mn 4+ The iron source is a titanium dioxide byproduct having ferrous sulfate heptahydrate, and the titanium dioxide byproduct includes metal ions, and the metal ions include Ni 2+ Mg 2+ and Mn 4+ The chemical formula of the sodium ion battery positive electrode material is Na x Fe y Ni a Co b Mn c Mg d (SO4) z @C, where 1≤x / y≤2, (a+b+c+d) / y≤0.1; The sodium ion battery positive electrode material includes sodium ferric sulfate, a carbon material and a plurality of metal ions, wherein the carbon material is dispersed among the sodium ferric sulfate, and the metal ions are doped in the crystal structure of the sodium ferric sulfate.

5. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, wherein: The sodium ion battery positive electrode material prepared by using an iron source, a layered oxide precursor byproduct having sodium sulfate, and a carbon material as raw materials includes: The titanium dioxide by-product is subjected to a first purification treatment to obtain a first purified solution; the first purification treatment can remove insoluble substances in the titanium dioxide by-product, and the first purified solution includes ferrous sulfate heptahydrate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ Mg 2+ and Mn 4+ ; The layered oxide precursor by-product is subjected to a second purification treatment to obtain a second purified solution; the second purification treatment can remove ammonia nitrogen in the layered oxide precursor by-product, and the second purified solution includes sodium sulfate and a plurality of soluble metal ions, wherein the soluble metal ions include Ni 2+ 、Co 2+ and Mn 4+ ; Mixing and drying the first purified solution, the second purified solution, and the carbon material to obtain a positive electrode material precursor; Granulating the positive electrode material precursor to obtain a precursor pressed material; The precursor pressed material is sintered and crushed to obtain the sodium ion battery positive electrode material.

6. The method for preparing a positive electrode material for a sodium ion battery according to claim 5, wherein: The first purification process of the titanium dioxide by-product to obtain a first purified solution comprises: dissolving the titanium dioxide by-product in deionized water, and dispersing iron powder in the deionized water to obtain a first initial solution; The sodium hydroxide solution and the first initial solution are mixed until the pH of the first initial solution reaches the first target pH, and filtered to obtain a filtrate; the first target pH is 4.5 to 5; the titanium dioxide by-product also includes Ti 2+ , in the case of the first target pH, the Ti in the first initial solution 2+ A precipitation reaction occurs to form an insoluble titanium precipitate; Sulfuric acid, an antioxidant and the filtrate are mixed until the pH of the filtrate reaches a second target pH to obtain the first purified solution; the second target pH is 2 to 3.

5.

7. The method for preparing a positive electrode material for a sodium ion battery according to claim 6, wherein: The titanium dioxide by-product is subjected to a first purification treatment to obtain a first purified solution that meets at least one of the following characteristics: The insoluble matter of the titanium dioxide by-product includes titanium dioxide, and the mass proportion of the titanium dioxide in the titanium dioxide by-product is less than the first mass proportion, which is 0.7% to 1.3%; The mass proportion of the multiple soluble metal ions of the first purified solution in the titanium dioxide by-product is less than the second mass proportion, and the second mass proportion is 0.7% to 1.3%; The concentration of ferrous sulfate heptahydrate in the first initial solution is 50 g / L to 150 g / L; The mass percentage between the iron powder and the ferrous sulfate heptahydrate is 0.1% to 1%; The pH of the sodium hydroxide solution is 10-13; The antioxidant comprises at least one of ascorbic acid, oxalic acid and citric acid; The mass percentage between the antioxidant and the ferrous sulfate heptahydrate is 0.1% to 3%.

8. The method for preparing a positive electrode material for a sodium ion battery according to claim 5, wherein: The step of performing a second purification process on the layered oxide precursor by-product to obtain a second purified solution comprises: Deamination treatment is performed on the layered oxide precursor byproduct to obtain a second initial solution; Sulfuric acid and the second initial solution are mixed until the pH of the second initial solution reaches a third target pH, thereby obtaining the second purified solution; the third target pH is 6.7 to 7.

0.

9. The method for preparing a positive electrode material for a sodium ion battery according to claim 8, wherein: The second purification treatment is performed on the layered oxide precursor by-product to obtain a second purified solution that meets at least one of the following characteristics: The pH of the layered oxide precursor byproduct is greater than 12; The concentration of sodium sulfate in the layered oxide precursor by-product is 50 g / L to 200 g / L; The ammonia nitrogen content in the layered oxide precursor by-product is 5 g / L to 10 g / L; The content of the multiple soluble metal ions in the layered oxide precursor by-product of the second purified solution is 75 mg / L to 130 mg / L.

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