Lithium ferrite composite, method for producing the same, and use thereof

Abstract

The application discloses a lithium ferrite composite material, a preparation method and application thereof, and the preparation method of the lithium ferrite composite material comprises the following steps: heating a mixed system containing lithium ferrite, fluorosilicate and a solvent, coating the fluorosilicate on the surface of the lithium ferrite, and post-treating the mixed system after heating to obtain the lithium ferrite composite material. The lithium ferrite composite material can weaken the gelation phenomenon in the stirring step of preparing a positive electrode sheet of a lithium ion battery, and has a high specific capacity and good rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium ferrite composite material, its preparation method and its application. Background Technology

[0002] Global warming and the depletion of fossil fuels pose significant challenges to energy conversion and storage, making the development of new materials crucial for addressing these issues. Lithium-ion batteries, with their high energy density, high power density, long cycle life, good safety, and pollution-free characteristics, have become ideal power sources for portable electronic devices, future large-scale energy storage, and automotive power batteries. The key to improving lithium-ion battery performance lies in developing novel high-capacity, high-rate, and long-life lithium storage materials. However, due to the formation of an SEI film during the first formation cycle, irreversible lithium-ion loss occurs. Lithium ferrite is an important pre-lithiation material, widely used in lithium-ion battery cathode slurry due to its high specific capacity. However, during stirring, lithium ferrite often experiences gelation, leading to a decrease in its stability and performance.

[0003] In the prior art, Chinese patent CN114447307A discloses a composite lithium ferrite material, which includes lithium ferrite and a polymer layer coated on the surface of lithium ferrite; the polymer layer is an olefin-acrylate copolymer; although the gelation problem of the above-mentioned composite lithium ferrite material is improved in the preparation of slurry, the presence of the coating layer (olefin-acrylate copolymer) leads to a smaller surface area of ​​lithium ferrite particles, resulting in a decrease in their electrochemical activity and a decline in the pre-lithiation effect.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium ferrite composite material, its preparation method and its application. The lithium ferrite composite material can reduce the gelation phenomenon during the stirring of the positive electrode of a lithium-ion battery, and the prepared lithium ferrite composite material has high specific capacity and good rate performance.

[0006] To achieve the above objectives, a specific embodiment of the present invention provides a method for preparing lithium ferrite composite materials, comprising the following steps:

[0007] Heating a mixture containing lithium ferrite, fluorosilicate, and a solvent causes the fluorosilicate to coat the surface of the lithium ferrite.

[0008] The heated mixture was post-treated to obtain a lithium ferrite composite material.

[0009] In one or more embodiments of the present invention, the molar ratio of lithium ferrite to fluorosilicate in the mixed system is 1:(0.05 to 0.2).

[0010] In one or more embodiments of the present invention, the fluorosilicate includes at least one of zinc fluorosilicate, sodium fluorosilicate, and ferrous fluorosilicate; and / or,

[0011] The solvent includes at least one of acetone and ethanol.

[0012] In one or more embodiments of the present invention, the heating temperature of the mixing system is 70-80°C; the heating time is 8-12 hours.

[0013] In one or more embodiments of the present invention, post-processing of the heated mixture includes:

[0014] After cooling the mixture, it is filtered or centrifuged, and the resulting solid is dried to obtain a lithium ferrite composite material.

[0015] A specific embodiment of the present invention also provides a lithium ferrite composite material, the lithium ferrite composite material comprising lithium ferrite and a coating layer covering the surface of the lithium ferrite, the coating layer being a fluorosilicate.

[0016] In one or more embodiments of the present invention, the lithium ferrite composite material is in the form of irregular granules, and the particle size of the lithium ferrite composite material is 3 to 10 μm.

[0017] A specific embodiment of the present invention also provides an application of the lithium ferrite composite material as described above or the lithium ferrite composite material prepared by the preparation method of the lithium ferrite composite material as described above in the field of lithium-ion batteries.

[0018] A specific embodiment of the present invention also provides a positive electrode sheet, the raw materials of which include the lithium ferrite composite material as described above or the lithium ferrite composite material prepared by the method described above for preparing lithium ferrite composite material.

[0019] In one or more embodiments of the present invention, the raw material of the positive electrode sheet further includes a positive electrode material, and the mass of the lithium ferrite composite material is less than or equal to 5% of the mass of the positive electrode material.

[0020] In one or more embodiments of the present invention, the cathode material is at least one of lithium cobalt oxide, lithium manganese oxide, and ternary materials.

[0021] A specific embodiment of the present invention also provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, an electrolyte and a negative electrode, wherein the positive electrode is the aforementioned positive electrode.

[0022] Compared with the prior art, the beneficial effects of the lithium ferrite composite material, its preparation method, and its application of the present invention are as follows:

[0023] (1) The coating of fluorosilicates can form a conductive network structure on the surface of lithium ferrite particles, promoting the transport of lithium ions in the electrode (positive electrode) and improving the charge and discharge rate performance of the electrode. The coating of fluorosilicates can increase the interfacial heating area between lithium ferrite particles and the electrolyte in the battery, promoting ion transport and improving the charge and discharge performance of the battery. That is, it improves the rate performance of lithium ferrite composite materials, positive electrode sheets, and lithium-ion batteries;

[0024] (2) The coating of fluorosilicate can enhance the compatibility of lithium ferrite particles with other materials and reduce the phenomenon of slurry gelation.

[0025] (3) Fluorosilicones can suppress phase transitions and structural instability of lithium ferrite composites and cathode materials at high temperatures, improve the thermal stability of lithium ferrite composites and cathode materials, and thus improve the safety performance of batteries.

[0026] (4) The preparation method of the lithium ferrite composite material of the present invention has the advantages of simple process and convenient operation. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of a method for preparing lithium ferrite composite material in one example of the present invention;

[0029] Figure 2 This is a SEM image of the lithium ferrite composite material in Example 1 of the present invention;

[0030] Figures 3a-3c This is the EDS image of the lithium ferrite composite material in Example 1 of the present invention;

[0031] Figure 4 The above are charge-discharge curves of the lithium ferrite composite material electrode prepared in Example 1 of this invention at different rates.

[0032] Figure 5 This is a charge-discharge curve of the lithium ferrite material electrode prepared in Comparative Example 1 of the present invention at different rates;

[0033] Figure 6Electrochemical impedance spectroscopy (EIS) spectra of batteries prepared from lithium ferrite composite material in Example 1, batteries prepared from lithium ferrite material in Comparative Example 1, and batteries prepared from the blank group.

[0034] Figure 7 The cycling curves of batteries prepared from lithium ferrite composite material in Example 1 and lithium ferrite material in Comparative Example 1 are shown.

[0035] Figure 8 The images show the cycle curves of the lithium ferrite composite material battery prepared in Example 1 of this invention and the blank group battery. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0037] like Figure 1 As shown, a method for preparing a lithium ferrite composite material in one example of the present invention includes the following steps:

[0038] S1. Heating a mixture containing lithium ferrite (Li5FeO4), fluorosilicate and solvent, so that fluorosilicate coats the surface of lithium ferrite;

[0039] S2. Post-process the heated mixture to obtain lithium ferrite composite material.

[0040] It can be understood that the prepared lithium ferrite composite material can be considered as a layer of fluorosilicate coated on the surface of lithium ferrite particles. That is, through the composite of lithium ferrite and fluorosilicate, the gelation problem caused by the easy hydrolysis of lithium ferrite during the preparation of the positive electrode sheet is solved. At the same time, the lithium ferrite composite material also possesses excellent electrochemical activity and good pre-lithiation effect. The lithium ferrite composite material of this invention can be considered as a pre-lithiation reagent, lithium supplementer, etc.

[0041] Preferably, the molar ratio of lithium ferrite to fluorosilicate in the mixed system is 1:(0.05–0.2). High-purity lithium ferrite, fluorosilicate, and organic solvents can be prepared to ensure the purity and quality of the chemicals, thereby guaranteeing the performance of the prepared lithium ferrite composite material.

[0042] If the molar ratio of lithium ferrite to fluorosilicate is less than 1:0.05, the amount of fluorosilicate will be too low, resulting in poor coating properties of fluorosilicate, thus causing the problems that occurred in the background art when only lithium ferrite was used.

[0043] If the molar ratio of lithium ferrite to fluorosilicate is higher than 1:0.02, the coating layer (fluorosilicate) will be too heavy, resulting in a decrease in the lithium replenishment effect of lithium ferrite, a decrease in the specific capacity of the lithium ferrite composite material, an excessively large coating layer weight ratio, and an excessively high viscosity of the slurry. This will reduce the stability of the lithium ferrite composite material and cause partial detachment. An excessively thick coating layer is prone to severe polarization, resulting in voltage hysteresis. Consequently, the lithium replenishment potential will shift to a higher potential, requiring a high-voltage settling process, which will cause the electrolyte to decompose.

[0044] The fluorosilicate may include at least one of zinc fluorosilicate, sodium fluorosilicate, and ferrous fluorosilicate; the solvent is an organic solvent, such as at least one of acetone and ethanol.

[0045] Understandably, in a mixed system, lithium ferrite is not dissolved in the solvent, but rather dispersed within it. The amount of solvent added can be determined based on the total molar number of lithium ferrite and fluorosilicate to ensure sufficient dissolution of the fluorosilicate and adequate dispersion of the lithium ferrite. For example, the amount of solvent added can be 20 to 50 times the total molar number of lithium ferrite and fluorosilicate.

[0046] In this invention, the heating temperature of the mixed system is 70–80°C; the heating time is 8–12 hours. This temperature and time are to ensure that the fluorosilicate can completely coat the lithium ferrite particles.

[0047] Post-treatment of the heated mixture includes:

[0048] After cooling the mixture, it is filtered or centrifuged, and the resulting solid is dried to obtain a lithium ferrite composite material.

[0049] Specifically, cooling can be considered as cooling to room temperature (around 25°C); depending on actual needs, the above drying process can specifically include solvent drying, crushing or screening operations, so that the obtained lithium ferrite composite material is granular and meets the required particle morphology and size requirements.

[0050] A specific example of the present invention also provides a lithium ferrite composite material, which includes lithium ferrite and a coating layer on the surface of the lithium ferrite, the coating layer being a fluorosilicate. The lithium ferrite composite material of the present invention can be prepared using the above-described method for preparing lithium ferrite composite materials, or it can be prepared using other methods.

[0051] Specifically, the lithium ferrite composite material of the present invention is in the form of irregular granules with a particle size of 3–10 μm. This shape and particle size give the lithium ferrite composite material a large specific surface area, thereby exhibiting excellent electrical properties.

[0052] A specific example of the present invention also provides the application of the lithium ferrite composite material as described above, or the lithium ferrite composite material prepared by the method described above, in the field of lithium-ion batteries. That is, the lithium ferrite composite material described above can be used as one of the positive electrode raw materials for lithium-ion batteries.

[0053] A specific example of the present invention also provides a positive electrode sheet, the raw materials of which include the lithium ferrite composite material as described above or the lithium ferrite composite material prepared by the method described above for preparing the lithium ferrite composite material.

[0054] Specifically, the raw materials for the positive electrode sheet also include the positive electrode material itself, with the mass of the lithium ferrite composite material being less than or equal to 5% of the mass of the positive electrode material. The raw materials for the positive electrode sheet may also include conductive agents and binders. Conductive agents and binders are common raw materials used in positive electrode sheets on the market. For example, conductive agents can be carbon black, carbon nanotubes, etc.; binders can be polyvinylidene fluoride (PVDF) binders, etc. The statement that the mass of the lithium ferrite composite material is less than or equal to 5% of the mass of the positive electrode material means that, in the raw materials for the positive electrode sheet, the mass of the lithium ferrite composite material is less than or equal to 5% of the mass of the positive electrode material.

[0055] The cathode material is at least one of lithium cobalt oxide, lithium manganese oxide, and ternary materials. Among them, ternary materials (NCM) refer to materials composed of three metal elements, nickel, cobalt, and manganese (aluminum), used to prepare the cathode of lithium-ion batteries, such as NCM523, NCM811, etc.

[0056] A specific example of the present invention also provides a lithium-ion battery, which includes a positive electrode, an electrolyte, and a negative electrode as described above. It is understood that the lithium-ion battery may also include structures such as a separator. The electrolyte can also be considered as a liquid electrolyte solution.

[0057] The lithium ferrite composite material of the present invention, its preparation method and its application will be described in detail below with reference to specific embodiments and comparative examples.

[0058] Example 1

[0059] Lithium ferrite and zinc fluorosilicate with a purity of 99.5% were selected, along with acetone as the organic solvent. Lithium ferrite and zinc fluorosilicate were mixed thoroughly in acetone at a molar ratio of 1:0.05 (5 ml acetone for every 1 g of solid (lithium ferrite and zinc fluorosilicate)) to ensure the homogeneity of the mixture. The mixture was placed in a reaction vessel and maintained at 70°C for 8 hours. After heating, the mixture was cooled to room temperature, filtered, and the collected precipitate was dried to obtain the lithium ferrite composite material.

[0060] Figure 3a EDS image of the lithium ferrite composite material prepared in this embodiment; Figure 3bThis is the EDS diagram of fluorine in the lithium ferrite composite material prepared in this embodiment; Figure 3c This is the EDS diagram of iron in the lithium ferrite composite material prepared in this embodiment.

[0061] Depend on Figure 2 , Figure 3a , Figure 3b and Figure 3c As can be seen, the lithium ferrite composite material prepared in this embodiment is in the form of irregular granules with a particle size between 3 and 5 μm and a smooth surface.

[0062] Example 2

[0063] Lithium ferrite and sodium fluorosilicate with a purity of 99.8% were selected, along with ethanol as the organic solvent. Lithium ferrite and sodium fluorosilicate were mixed thoroughly in ethanol (5 ml of acetone for every 1 g of solid (lithium ferrite and sodium fluorosilicate)) at a molar ratio of 1:0.1 to ensure the homogeneity of the mixture. The mixture was placed in a reaction vessel and maintained at 80°C for 10 hours. After heating, the mixture was cooled to room temperature, filtered, and the collected precipitate was dried to obtain the lithium ferrite composite material. The lithium ferrite composite material was in the form of irregularly shaped particles with an average particle size of approximately 5 μm.

[0064] Example 3

[0065] Lithium ferrite and ferrous fluorosilicate with a purity of 99.7% were selected, along with acetone and ethanol as organic solvents (the volume ratio of acetone to ethanol was 3:1). Lithium ferrite and ferrous fluorosilicate were mixed uniformly in the organic solvent at a molar ratio of 1:0.15 (5 ml of organic solvent for every 1 g of solid (lithium ferrite and ferrous fluorosilicate)) to ensure the homogeneity of the mixture. The mixture was placed in a reaction vessel and maintained at 75°C for 12 hours. After heating, the mixture was cooled to room temperature, filtered, and the collected precipitate was dried to obtain the lithium ferrite composite material. The lithium ferrite composite material was in the form of irregularly shaped particles with an average particle size of approximately 6 μm.

[0066] Example 4

[0067] Lithium ferrite, zinc fluorosilicate, and sodium fluorosilicate with a purity of 99.8% were selected, along with ethanol as the organic solvent. Lithium ferrite and fluorosilicates (zinc fluorosilicate and sodium fluorosilicate) were mixed uniformly in acetone (5 ml acetone for every 1 g of solid (lithium ferrite, zinc fluorosilicate, and sodium fluorosilicate)) at a molar ratio of 1:0.2, ensuring the homogeneity of the mixture. The mixture was placed in a reaction vessel and maintained at 78°C for 9 hours. After heating, the mixture was cooled to room temperature, filtered, and the collected precipitate was dried to obtain the lithium ferrite composite material. The lithium ferrite composite material was in the form of irregularly shaped particles with an average particle size of approximately 4 μm.

[0068] Comparative Example 1

[0069] Lithium ferrite (commonly available on the market) was chosen as the lithium ferrite material.

[0070] Comparative Example 2

[0071] Lithium carbonate and iron oxide were mixed in a mass ratio of 7:1 and calcined at 800°C for 10 hours in an argon atmosphere to obtain lithium ferrite powder. Ethylene-methyl methacrylate copolymer with a weight average molecular weight of 50,000 was dispersed in dimethyl sulfoxide solvent to form an ethylene-methyl methacrylate copolymer solution with a mass concentration of 5%. The lithium ferrite powder and the ethylene-methyl methacrylate copolymer solution were then stirred for 60 minutes. After removing the solvent at a pressure of -250 kPa (relative to atmospheric pressure) and 140°C, the mixture was cooled to obtain the final lithium ferrite material.

[0072] The lithium ferrite composite materials prepared in Examples 1-4, as well as the lithium ferrite materials in Comparative Examples 1 and 2, were subjected to the following performance tests:

[0073] A composite electrode was prepared by uniformly mixing lithium ferrite composite material (or lithium ferrite material) with conductive agent carbon black and binder polyvinylidene fluoride in a ratio of 8:1:1. A lithium metal sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (ED:DMC:EMC = 1:1:1 (volume ratio)) was used as the electrolyte to assemble a lithium-ion battery. Charge-discharge tests were then conducted between 2.5 and 4.5 V, and the test results are shown in Table 1. Figure 4 and Figure 5 The charge / discharge curves.

[0074] The lithium ferrite composite materials prepared in Examples 1-4 and the lithium ferrite material of Comparative Example 1 were subjected to the following performance tests:

[0075] The degradation time of the lithium iron phosphate composite materials prepared in Examples 1-4 and the slurry prepared from the lithium iron phosphate material of Comparative Example 1 (in which lithium iron phosphate, lithium iron phosphate composite material (or lithium iron phosphate material), conductive carbon black and binder are uniformly mixed in a ratio of 75:5:10:10) under different air humidity conditions was tested, and the test results are shown in Table 2.

[0076] The lithium ferrite composite material prepared in Example 1, as well as the lithium ferrite materials of Comparative Examples 1 and 2, were subjected to the following performance tests:

[0077] A composite electrode was prepared by uniformly mixing lithium iron phosphate and lithium ferrite composite materials (or lithium ferrite material) with conductive agent carbon black and binder polyvinylidene fluoride at a ratio of 75:X:10:10. Graphite was used as the counter electrode, with N / P = 1.1. A 1 mol / L LiPF6 solution (ED:DMC:EMC = 1:1:1 (volume ratio)) was used as the electrolyte to assemble a lithium-ion battery. The first cycle charge-discharge test was conducted between 2.7 and 4.5 V, and the subsequent cycle test was conducted between 2.8 and 3.65 V. The test results are shown in Table 3. Figure 7 and Figure 8 The cyclic curve graph.

[0078] The lithium ferrite composite material prepared in Example 1 and the lithium ferrite material in Comparative Example 1 were subjected to the following performance tests:

[0079] A composite electrode, obtained by uniformly mixing lithium iron phosphate, lithium ferrite composite material (or lithium ferrite material) with conductive agent carbon black and binder polyvinylidene fluoride in a ratio of 75:5:10:10, was used as the working electrode. Graphite was used as the counter electrode, with N / P = 1.1. A lithium-ion battery was assembled using a 1 mol / L LiPF6 solution (ED:DMC:EMC = 1:1:1 (volume ratio)) as the electrolyte. Electrochemical impedance spectroscopy (EIS) tests were performed (a blank group was added, i.e., the working electrode of the lithium-ion battery in the blank group did not contain the lithium ferrite composite material). The results were as follows: Figure 6 The electrochemical impedance spectroscopy shown ( Figure 6 (The data with triangles on the curve represents data from Example 1). (Through...) Figure 6 It can be seen that the electrochemical impedance of the battery prepared by the lithium ferrite composite material in Example 1 is close to that of the battery in the blank group, while the electrochemical impedance of the battery prepared by the lithium ferrite material in Comparative Example 1 is significantly greater than that of the battery in the blank group.

[0080] Table 1

[0081]

[0082] Through Table 1 and Figure 4 and Figure 5 As can be seen from the data of Example 1 and Comparative Example 1, the lithium ferrite composite material of the present invention has a higher irreversible capacity and a better lithium replenishment effect, regardless of whether it is at a low rate or a high rate.

[0083] Table 2

[0084] Air humidity 20% Air humidity 40% Air humidity 60% Air humidity 80% Comparative Example 1 1h 0.6h 0.5h 0.2h Example 1 ＞8h ＞8h ＞6h ＞4h Example 2 ＞8h ＞8h ＞6h ＞4h Example 3 ＞8h ＞8h ＞6h ＞4h Example 4 ＞8h ＞8h ＞6h ＞4h

[0085] As can be seen from the data in Table 2, regardless of whether the humidity is low or high, the deterioration time of the slurry prepared in the embodiment of the present invention is significantly longer than that of the slurry prepared in Comparative Example 1. This is because the lithium ferrite composite material of the present invention can effectively reduce the gelation phenomenon of lithium ferrite in the slurry preparation process, which is beneficial to the storage and transportation of the slurry and is more suitable for actual industrial production.

[0086] Table 3

[0087]

[0088] Through Table 3 and Figure 7 and Figure 8 The data shows that adding lithium ferrite composite material (also known as lithium replenisher or pre-lithiation agent) can effectively improve the battery capacity retention rate. Furthermore, with the same number of lithium ferrite composite materials, the battery with the lithium ferrite composite material of this invention exhibits a significantly better capacity retention rate than the battery with the lithium ferrite material of Comparative Example 1.

[0089] As can be seen from the data in Tables 1 and 3 and common knowledge, the thick coating of lithium ferrite material in Comparative Example 2 leads to a decrease in its electrochemical activity and pre-lithiation effect. The resistivity of lithium ferrite material itself is relatively high, and its addition causes an increase in the resistance of the battery system. It can only reduce the alkalinity, resulting in a decrease in the lithium replenishment effect and high resistance.

[0090] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0091] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a lithium ferrite composite material, characterized in that, Includes the following steps: Heating a mixture containing lithium ferrite, fluorosilicate, and a solvent causes the fluorosilicate to coat the surface of the lithium ferrite. The heated mixture was post-treated to obtain a lithium ferrite composite material. The fluorosilicate includes at least one of zinc fluorosilicate, sodium fluorosilicate, and ferrous fluorosilicate; Post-processing of the heated mixture includes: cooling the mixture and then filtering or centrifuging it, drying the resulting solid, and obtaining a lithium ferrite composite material.

2. The method for preparing the lithium ferrite composite material according to claim 1, characterized in that, The molar ratio of lithium ferrite to fluorosilicate in the mixed system is 1:(0.05~0.2).

3. The method for preparing the lithium ferrite composite material according to claim 1, characterized in that, The solvent includes at least one of acetone and ethanol.

4. The method for preparing the lithium ferrite composite material according to claim 1, characterized in that, The heating temperature of the mixture is 70~80℃; the heating time is 8~12h.

5. A lithium ferrite composite material, characterized in that, The lithium ferrite composite material includes lithium ferrite and a coating layer covering the surface of the lithium ferrite. The coating layer is a fluorosilicate, wherein the fluorosilicate includes at least one of zinc fluorosilicate, sodium fluorosilicate, and ferrous fluorosilicate.

6. The lithium ferrite composite material according to claim 5, characterized in that, The lithium ferrite composite material is in the form of irregular particles, and the particle size of the lithium ferrite composite material is 3~10μm.

7. The application of a lithium ferrite composite material as described in claim 5 or a lithium ferrite composite material prepared by the preparation method of any one of claims 1 to 4 in the field of lithium-ion batteries.

8. A positive electrode sheet, characterized in that, Its raw materials include lithium ferrite composite materials as described in claim 5 or 6, or lithium ferrite composite materials prepared by the preparation method of lithium ferrite composite materials as described in any one of claims 1 to 4.

9. The positive electrode sheet according to claim 8, characterized in that, The raw materials for the positive electrode sheet also include positive electrode material, and the mass of the lithium ferrite composite material is less than or equal to 5% of the mass of the positive electrode material.

10. The positive electrode sheet according to claim 9, characterized in that, The cathode material is at least one of lithium cobalt oxide, lithium manganese oxide, and ternary materials.

11. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode is the positive electrode as described in any one of claims 8 to 10.

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