A fluorophosphate composite electrode material, its preparation method and application

Abstract

The present application discloses a fluorophosphate composite electrode material, a preparation method thereof and an application thereof, belonging to the technical field of electrode materials. The preparation method of the present application includes: providing a fluorophosphate precursor solution; dispersing a functionalized carbon material in water to obtain a dispersion, and mixing the dispersion with the fluorophosphate precursor solution to obtain a mixed solution; after the mixed solution is evaporated to form a gel-like material, drying and grinding the gel-like material to form a fluorophosphate composite electrode material precursor; in an anaerobic atmosphere, performing pre-heat treatment and post-heat treatment on the fluorophosphate composite electrode material precursor to obtain a fluorophosphate composite electrode material. The present application effectively solves the problems existing in the synthesis of fluorophosphate-carbon material composites by the sol-gel method in the prior art, such as poor crystallization performance, many surface defects, long sintering time, insufficient electronic conductivity, and easy fragmentation and cracking of the electrode material and the electrode structure morphology due to volume change during the cycling process.

Description

Technical Field

[0001] This application belongs to the technical field of electrode materials, and particularly relates to a fluorophosphate composite electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] As a commonly used cathode material for metal ion batteries, fluorophosphate has the advantages of high potential and high energy density. However, due to the problems of low intrinsic electronic conductivity and poor crystallization performance of fluorophosphate electrode materials, metal ion batteries have defects such as low capacity, poor rate performance, and obvious cycle attenuation, which greatly limit the application of fluorophosphate electrode materials.

[0003] To improve the performance defects of fluorophosphate electrode materials, existing technologies have studied and developed modification methods such as carbon coating and metal doping. Among them, the patent application with publication number CN 112186154A discloses a preparation method of sodium vanadium fluorophosphate@CNTs composite material, which in-situ composites Na3V2(PO4)2F3 with CNTs by sol-gel method, not only can significantly enhance the crystallization performance of Na3V2(PO4)2F3, but also can improve the stability performance of Na3V2(PO4)2F3.

[0004] However, when synthesizing sodium vanadium fluorophosphate@CNTs composite material by sol-gel method, due to the excessive dispersion of ions of Na3V2(PO4)2F3 precursor and being separated by chelating agents, on the one hand, the sintering time is long, the energy consumption is high, and the cost is high, which is not conducive to industrial application, and long-time sintering may cause the loss of light element F in Na3V2(PO4)2F3 material and crystal surface defects, resulting in poor structural stability performance and many impurities of sodium vanadium fluorophosphate@CNTs composite material; on the other hand, it leads to problems such as small grain size and many defects of Na3V2(PO4)2F3 primary particles, resulting in easy electrode cracking and secondary particle fragmentation during charge and discharge, and rapid capacity attenuation and poor rate performance of ion batteries. Summary of the Invention

[0005] The purpose of this application is to provide a fluorophosphate composite electrode material, a preparation method thereof, and an application thereof, aiming to solve the technical problems of long sintering time, high cost required for synthesizing sodium vanadium fluorophosphate@CNTs composite material by existing sol-gel method, and poor structural stability performance of the synthesized sodium vanadium fluorophosphate@CNTs composite material and the electrode formed thereby.

[0006] To achieve the above purpose, the technical solution of the embodiment of this application is:

[0007] In the first aspect, the embodiment of this application provides a preparation method of a fluorophosphate composite electrode material, which includes the following steps:

[0008] Step A: Provide a fluorophosphate precursor solution;

[0009] Step B: Disperse the functionalized carbon material in water to obtain a dispersion; the functionalized carbon material is selected from any one of hydroxylated carbon materials, carboxylated carbon materials, aminated carbon materials, sulfonated carbon materials, and nitrated carbon materials;

[0010] Step C: Mix the dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0011] Step D: Evaporate the mixed solution to form a gel-like material, and then dry and grind the gel-like material to form a fluorophosphate composite electrode material precursor;

[0012] Step E: In an anaerobic atmosphere, pre-treat and post-treat the fluorophosphate composite electrode material precursor to obtain the fluorophosphate composite electrode material;

[0013] Step A and Step B are not in a sequential order.

[0014] In a preferred implementation of the first aspect, the carbon material of the functionalized carbon material includes at least one of graphene, carbon nanotubes, and nanofibers.

[0015] In a preferred implementation of the first aspect, the method for preparing the dispersion includes:

[0016] Place the functionalized carbon material into an ultrasonic cell disruptor for dispersion in an ice-water bath to obtain the dispersion.

[0017] In a preferred implementation of the first aspect, the method for preparing the fluorophosphate precursor solution includes:

[0018] Dissolve a phosphorus source, a fluorine source, a transition metal source, an alkali metal source, and a chelating agent in water to obtain the fluorophosphate precursor solution;

[0019] The alkali metal source is one or more of oxides, carbonates, phosphates, or alkalis of lithium, sodium, and potassium elements;

[0020] The transition metal source is one or more of oxides, phosphates, carbonates, or ammonium salts of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper elements;

[0021] The phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, and ammonium phosphate;

[0022] The carbon source is one or more of formic acid, gallic acid, oxalic acid, tartaric acid, malic acid, citric acid, vitamin C, glucose, sucrose, fructose, and EDTA.

[0023] In a preferred implementation of the first aspect, when the dispersion liquid is mixed with the fluorophosphate precursor solution, the addition amount of the functionalized carbon material is 0.01-10% of the target yield of fluorophosphate.

[0024] In a preferred implementation of the first aspect, the temperature for evaporating the mixed solution is 70-100 °C, and the time is 2-24 h;

[0025] Also, the temperature for drying the gel-like material is 60-100 °C.

[0026] In a preferred implementation of the first aspect, the temperature of the pre-heat treatment is 350 °C, and the time is 0.1-10 h.

[0027] In a preferred implementation of the first aspect, the temperature of the post-heat treatment is 350-800 °C, and the time is 0.1-3.5 h.

[0028] In the second aspect, the embodiments of the present application further provide a fluorophosphate composite electrode material formed by the method described in the first aspect.

[0029] In the third aspect, the embodiments of the present application further provide an application of the fluorophosphate composite electrode material described in the second aspect in the manufacture of electrodes for metal ion batteries.

[0030] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application at least include:

[0031] The preparation method according to the first aspect of the embodiments of the present application involves mixing a fluorophosphate precursor solution with a functionalized carbon material dispersion and then performing sol-gel synthesis. Among them, the hydroxyl, carboxyl, amino, sulfonic acid, and nitro groups modified on the surface of the functionalized carbon material can induce the adsorption of metal ions in fluorophosphate and enrich them around the carbon material. Firstly, this can promote the adsorption nucleation and rapid growth of fluorophosphate on the surface of the carbon material, enabling the rapid growth of primary fluorophosphate particles. Secondly, during high-temperature sintering, it can enable the rapid transport of metal and non-metal ions along the surface of the carbon material, thereby enabling the further rapid growth of fluorophosphate grains on the surface of the carbon material. While effectively improving the crystallization performance and primary particle size of fluorophosphate, it significantly shortens the sintering time, greatly reduces labor and energy costs, and improves the equipment usage efficiency. Thirdly, it can enable the anchored growth of fluorophosphate particles on the surface of the carbon material, significantly enhancing the interaction force between fluorophosphate and the carbon material. Therefore, based on the characteristic of the tight anchoring between the carbon material and fluorophosphate particles during the cycling process, it can effectively inhibit the problems of electrode surface cracking and particle fragmentation caused by the volume change of the electrode material, improving the stability of the electrode morphology and structure. Fourthly, during the charge and discharge process of the battery, since electrons are transported along the carbon material to the anchored fluorophosphate, the electronic conductivity of the fluorophosphate composite material is effectively improved. Fifthly, the light F element in fluorophosphate is prone to loss during the sintering process. Therefore, based on the significantly shortened sintering time in this application, it can effectively reduce the side reactions caused by F element loss, significantly improving the uniformity and consistency of multi-batch synthesis. In view of this, the embodiments of the present application utilize functionalized carbon materials to modify fluorophosphate electrode materials and synthesize them through sol-gel method, effectively solving the problems existing in the synthesis of fluorophosphate-carbon material composites by sol-gel method in the prior art, such as poor crystallization performance, many surface defects, long sintering time, insufficient electronic conductivity, and easy fragmentation and cracking of the electrode material and electrode structure morphology due to volume change during the cycling process. Description of the Drawings

[0032] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 Microscopic TEM image of the NVPF-6004 material synthesized in Comparative Example 1;

[0034] Figure 2 Microscopic TEM image of the NVPF@CNT001-600-35 composite material synthesized in Example 1;

[0035] Figure 3 Microscopic TEM image of the NVPF@CNT05-600-35 composite material synthesized in Example 2;

[0036] Figure 4 Microscopic TEM image of the NVPF@CNT1-600-35 composite material synthesized in Example 3;

[0037] Figure 5 XRD patterns of the NVPF-6004 material synthesized in Comparative Example 1, the NVPF@CNT001-600-35 composite material synthesized in Example 1, the NVPF@CNT05-600-35 composite material synthesized in Example 2, the NVPF@CNT1-600-35 material synthesized in Example 3, and the NVPF@CNT01-700-01 composite material synthesized in Example 4;

[0038] Figure 6 Charge-discharge curves of the electrode of the NVPF-6004 material synthesized in Comparative Example 1, the electrode of the NVPF@CNT001-600-35 composite material synthesized in Example 1, the electrode of the NVPF@CNT05-600-35 composite material synthesized in Example 2, and the electrode of the NVPF@CNT1-600-35 material synthesized in Example 3;

[0039] Figure 7 Cycling performance graphs of the electrode of the NVPF-6004 material synthesized in Comparative Example 1, the electrode of the NVPF@CNT001-600-35 composite material synthesized in Example 1, the electrode of the NVPF@CNT05-600-35 composite material synthesized in Example 2, and the electrode of the NVPF@CNT1-600-35 material synthesized in Example 3;

[0040] Figure 8 Cycling performance graphs at a 1C rate of the electrode of the NVPF-6004 material synthesized in Comparative Example 1, the electrode of the NVPF@CNT-600-8 composite material synthesized in Comparative Example 2, and the electrode of the NVPF@CNT001-600-35 composite material synthesized in Example 1;

[0041] Figure 9 SEM image of the electrode of the NVPF@CNT001-600-35 composite material synthesized in Example 1 after 1000 cycles;

[0042] Figure 10 TEM image of the electrode of the NVPF@CNT001-600-35 composite material synthesized in Example 1 after 1000 cycles;

[0043] Figure 11XRD patterns of the NVPF-6004 material synthesized in Comparative Example 1, the NVPF@CNF1-600-2 composite material synthesized in Example 5, and the NVPF@CNF10-600-2 composite material synthesized in Example 6;

[0044] Figure 12 SEM images of the KVPF-6501 material synthesized in Comparative Example 3;

[0045] Figure 13 SEM images of the KVPF@CNT01-650-1 composite material synthesized in Example 7;

[0046] Figure 14 SEM images of the KVPF@CNT005-650-1 composite material synthesized in Example 8;

[0047] Figure 15 XRD patterns of the KVPF-6501 material synthesized in Comparative Example 3, the KVPF@CNT01-650-1 composite material synthesized in Example 7, and the KVPF@CNT005-650-1 composite material synthesized in Example 8;

[0048] Figure 16 Charge-discharge curves of the electrodes of the KVPF-6501 material synthesized in Comparative Example 3, the KVPF@CNT01-650-1 composite material electrode synthesized in Example 7, and the KVPF@CNT005-650-1 composite material electrode synthesized in Example 8;

[0049] Figure 17 Cycling performance graphs of the electrodes of the KVPF-6501 material synthesized in Comparative Example 3, the KVPF@CNT01-650-1 composite material electrode synthesized in Example 7, and the KVPF@CNT005-650-1 composite material electrode synthesized in Example 8. Detailed implementation manners

[0050] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0051] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: the situation of A existing alone, B existing alone, and A and B existing simultaneously. Among them, A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0052] In the following description of this embodiment, the term "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural item(s). For example, "at least one of a, b or c", or "at least one of a, b and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0053] Those skilled in the art should understand that in the following description of the embodiments of this application, the sequence numbers do not imply the order of execution. Some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, without constituting any limitation to the implementation process of the embodiments of this application.

[0054] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms "a" and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0055] Before explaining the technical solutions of the embodiments of this application in detail, the technical principles involved in the embodiments of this application will be described first.

[0056] In the synthesis process of the fluorophosphate sol - gel method in the embodiments of this application, functionalized carbon materials are added. The hydroxyl, carboxyl, amino, sulfonic acid group, and nitro group modified on the surface of the functionalized carbon materials can induce and adsorb metal ions in the fluorophosphate and enrich them around the carbon materials, so that the metal ions in the fluorophosphate are no longer overly dispersed. On the one hand, it can promote the nucleation and growth of fluorophosphate on the surface of the carbon materials. On the other hand, during the high - temperature sintering process, the carbon materials can be used as a rapid ion - transport path to promote ion transport, which can further promote the rapid growth of fluorophosphate grains on the surface of the carbon materials. Thirdly, it can enable the fluorophosphate and the carbon material surface to be combined with each other in a high - strength binding manner of the anchoring effect. Therefore, the modification method of mixing the fluorophosphate precursor solution and the functionalized carbon material dispersion and then carrying out sol - gel synthesis in the embodiments of this application can not only significantly shorten the sintering time, but also further improve the crystallinity - structural stability, electronic conductivity, and morphological structural stability of the fluorophosphate composite material, making the specific capacity, rate performance, and cycle life of the battery significantly improved.

[0057] Next, the preparation method of the fluorophosphate composite electrode material provided in the first aspect of the embodiments of this application will be introduced.

[0058] In a first aspect, the preparation method includes the following steps:

[0059] Step A: Provide a fluorophosphate precursor solution;

[0060] Step B: Disperse the functionalized carbon material in water to obtain a dispersion; the functionalized carbon material is selected from any one of hydroxylated carbon materials, carboxylated carbon materials, aminated carbon materials, sulfonated carbon materials, and nitrated carbon materials;

[0061] Step C: Mix the dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0062] Step D: Evaporate the mixed solution to form a gel-like material, and then dry and grind the gel-like material to form a fluorophosphate composite electrode material precursor;

[0063] Step E: In an anaerobic atmosphere, perform pre-heat treatment and post-heat treatment on the fluorophosphate composite electrode material precursor to obtain the fluorophosphate composite electrode material;

[0064] Steps A and B can be carried out in any order.

[0065] Among them, the hydroxyl, carboxyl, amino, sulfonic acid, and nitro groups modified on the surface of the functionalized carbon material can induce the adsorption of metal ions in fluorophosphate, enriching them around the carbon material. On the one hand, it can promote the nucleation and growth of fluorophosphate on the surface of the carbon material, enabling the rapid growth of primary particles of fluorophosphate; on the other hand, it can enable the rapid transmission of metal ions along the surface of the carbon material during high-temperature sintering, thereby enabling the further rapid growth of fluorophosphate grains on the surface of the carbon material. While significantly improving the crystallization performance and primary particle size of fluorophosphate, it significantly shortens the sintering time, which is beneficial for significantly reducing labor and energy costs and improving equipment usage efficiency; on the third hand, it can enable the anchored growth of fluorophosphate particles on the surface of the carbon material, significantly enhancing the interaction between fluorophosphate and the carbon material. Thus, based on the characteristics of the tight anchoring between the carbon material and fluorophosphate particles during the cycling process, it can effectively suppress the problems of electrode surface cracking and particle fragmentation caused by the volume change of the electrode material, improving the stability of the electrode morphology structure; on the fourth hand, during the charge and discharge process of the battery, since electrons are transmitted along the carbon material to the anchored fluorophosphate, it effectively improves the electronic conductivity of the fluorophosphate composite material; on the fifth hand, the light F element in fluorophosphate is prone to loss during the sintering process. Therefore, based on the ability of this application to shorten the sintering time, it can effectively reduce the side reactions caused by F element loss, significantly improving the uniformity and consistency of multi-batch synthesis. In view of this, the embodiments of this application use a functionalized carbon material to modify the fluorophosphate electrode material and synthesize it by the sol-gel method, effectively solving the problems of poor crystallization performance, many surface defects, long sintering time, insufficient electronic conductivity, and easy fragmentation and cracking of the electrode material and electrode structure morphology caused by volume change during the cycling process in the prior art when using the sol-gel method to synthesize fluorophosphate-carbon material composites.

[0066] Meanwhile, this application synthesizes the fluorophosphate composite electrode material by the sol-gel method, which can achieve a higher synthesis yield of the fluorophosphate composite material compared to the hydrothermal method; compared to the solid-phase synthesis method, it can make the particle uniformity of the composite electrode material better and the carbon coating more uniform. In view of this, the fluorophosphate composite electrode material synthesized by the sol-gel method in this application is used to manufacture electrodes and applied in metal ion batteries, enabling the metal ion batteries to have higher specific capacity rate performance and better cycle stability.

[0067] In the embodiments of this application, the carbon material of the functionalized carbon material is preferably at least one of graphene, carbon nanotubes, and nanofibers. These three carbon materials can form one-dimensional or two-dimensional planar transport channels for ion transport at high temperatures, promoting the rapid growth of fluorophosphate material grains. Among them, the functionalized carbon material is obtained by modifying the carbon material according to known conventional methods, and the embodiments of this application do not make special limitations on this.

[0068] In the embodiments of the present application, the method for preparing the dispersion preferably includes:

[0069] Placing the functionalized carbon material into an ultrasonic cell disruptor for dispersion in an ice-water bath to obtain the dispersion. Among them, the cell disruptor is longitudinal ultrasound, which can improve the dispersion efficiency and dispersion effect of the functionalized carbon material in water.

[0070] In the embodiments of the present application, the method for preparing the fluorophosphate precursor solution preferably includes:

[0071] Dissolving a phosphorus source, a fluorine source, a transition metal source, an alkali metal source, and a chelating agent in water to obtain the fluorophosphate precursor solution;

[0072] The alkali metal source is one or more of oxides, carbonates, phosphates, or alkalis of lithium, sodium, and potassium elements;

[0073] The transition metal source is one or more of oxides, phosphates, carbonates, or ammonium salts of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper elements;

[0074] The phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, and ammonium phosphate;

[0075] The carbon source is one or more of formic acid, gallic acid, oxalic acid, tartaric acid, malic acid, citric acid, vitamin C, glucose, sucrose, fructose, and EDTA.

[0076] In the embodiments of the present application, when the dispersion is mixed with the fluorophosphate precursor solution, the addition amount of the functionalized carbon material is 0.01-10% of the target output of fluorophosphate.

[0077] In the embodiments of the present application, the temperature for evaporating the mixed solution is 70-100 °C, and the time is 2-24 h; and the temperature for drying the gel-like material is 60-100 °C.

[0078] In the embodiments of the present application, the temperature of the pre-heat treatment is 350 °C, and the time is 0.1-10 h.

[0079] In the embodiments of the present application, the temperature of the post-heat treatment is 350-800 °C, and the time is 0.1-3.5 h. Among them, the functionalized carbon material added during the synthesis of the fluorophosphate sol-gel method in the embodiments of the present application can enable the fluorophosphate electrode material to be sintered and formed within 0.1-3.5 h. Therefore, the preferred sintering time in the embodiments of the present application is 0.1-3.5 h, which can not only significantly reduce the labor and energy costs and improve the equipment use efficiency, but also effectively reduce the side reactions caused by the loss of F element, making the uniformity and consistency of multi-batch synthesis significantly improved.

[0080] In a second aspect, the embodiments of the present application also provide a fluorophosphate composite electrode material prepared and formed by the method described in the first aspect. Based on the preparation method of the first aspect, the sintering time can be shortened, the crystallization performance, the morphological structure stability, the electronic conductivity of the fluorophosphate composite electrode material can be improved, and the electrode cracking and the secondary particle breakage during the charge and discharge process can be effectively improved. Therefore, the fluorophosphate composite electrode material synthesized in the embodiments of the present application has the advantages of good surface structure stability, excellent electronic conductivity, and the morphology is not easily broken or cracked during the cycling process.

[0081] In a third aspect, the embodiments of the present application also provide an application of the fluorophosphate composite electrode material described in the second aspect in the manufacture of electrodes for metal ion batteries. Based on the advantages of the fluorophosphate composite electrode material described in the second aspect, such as good crystallization performance, morphological structure stability, excellent electronic conductivity, and the morphology is not easily broken or cracked during the cycling process. Therefore, when the electrode made of the fluorophosphate composite electrode material synthesized in the embodiments of the present application is applied in a metal ion battery, the metal ion battery can have better specific capacity, rate performance, and cycle life.

[0082] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0083] Example 1

[0084] This Example 1 provides a preparation method of NVPF@CNT001-600-35 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0085] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0086] Step B: Add CNT-COOH with a mass of 0.01% of Na3V2(PO4)2F3 into a beaker filled with pure water, and perform ice-water bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-COOH dispersion.

[0087] Step C: Mix the CNT-COOH dispersion liquid with the fluorophosphate precursor solution to obtain a mixed solution;

[0088] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Blast-dry the sol-gel precursor at 80 °C for 10 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite material precursor;

[0089] Step E: Put the fluorophosphate composite material precursor into a tubular furnace, and perform a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, perform secondary grinding. After secondary grinding, perform a post-heat treatment at a temperature of 600 °C for 3.5 h to obtain the NVPF@CNT001-600-35 composite material.

[0090] Example 2

[0091] This Example 2 provides a preparation method of the NVPF@CNT05-600-35 composite material, specifically including Step A to Step E. Among them, Step A and Step B have no sequential order.

[0092] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and perform magnetic stirring to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and perform magnetic stirring to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and perform magnetic stirring to obtain a fluorophosphate precursor solution.

[0093] Step B: Add CNT-COOH with a mass of 0.5% of Na3V2(PO4)2F3 to a beaker filled with pure water, and perform ice-water bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-COOH dispersion liquid.

[0094] Step C: Mix the CNT-COOH dispersion liquid with the fluorophosphate precursor solution to obtain a mixed solution;

[0095] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Blast-dry the sol-gel precursor at 80 °C for 10 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite material precursor;

[0096] Step E: Put the fluorophosphate composite material precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice, and then perform a post-heat treatment at a temperature of 600 °C for 3.5 h to obtain the NVPF@CNT05-600-35 composite material.

[0097] Example 3

[0098] This Example 3 provides a preparation method of the NVPF@CNT1-600-35 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0099] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0100] Step B: Add CNT-COOH with a mass of 1.0% of Na3V2(PO4)2F3 to a beaker containing pure water, and perform ice-water bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-COOH dispersion.

[0101] Step C: Mix the CNT-COOH dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0102] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Blast-dry the sol-gel precursor at 80 °C for 10 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite precursor;

[0103] Step E: Put the fluorophosphate composite precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, perform secondary grinding. After secondary grinding, perform a post-heat treatment at a temperature of 600 °C for 3.5 h to obtain the NVPF@CNT1-600-35 composite material.

[0104] Example 4

[0105] This Example 4 provides a preparation method of the NVPF@CNT01-700-01 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0106] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0107] Step B: Add CNT-OH with a mass of 0.1% of Na3V2(PO4)2F3 to a beaker containing pure water, and perform ice-water bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-OH dispersion.

[0108] Step C: Mix the CNT-OH dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0109] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 100 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 4 h to obtain a blue sol-gel precursor (gel-like material). Dry the sol-gel precursor at 100 °C under forced air for 10 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite precursor;

[0110] Step E: Put the fluorophosphate composite precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice, and then perform a post-heat treatment at a temperature of 700 °C for 0.1 h to obtain the NVPF@CNT01-700-01 composite material.

[0111] Example 5

[0112] This Example 5 provides a preparation method of the NVPF@CNF1-600-2 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0113] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0114] Step B: Add CNF-SO3H (sulfonated carbon fiber) with a mass of 1% of Na3V2(PO4)2F3 to a beaker containing pure water, and perform ultrasonic dispersion in an ice-water bath in an ultrasonic cell disruptor to obtain a CNT-OH dispersion.

[0115] Step C: Mix the CNF-SO3H dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0116] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Blast-dry the sol-gel precursor at 80 °C for 10 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite precursor;

[0117] Step E: Put the fluorophosphate composite precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice, and then perform a post-heat treatment at a temperature of 600 °C for 2 h to obtain the NVPF@CNF1-600-2 composite material.

[0118] Example 6

[0119] This Example 6 provides a preparation method of the NVPF@CNF10-600-2 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0120] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0121] Step B: Add CNF-SO3H (sulfonated carbon fiber) with a mass of 10% of Na3V2(PO4)2F3 to a beaker containing pure water, and perform ice bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-OH dispersion.

[0122] Step C: Mix the CNF-SO3H dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0123] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Blast-dry the sol-gel precursor at 80 °C for 10 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite precursor;

[0124] Step E: Put the fluorophosphate composite precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, perform secondary grinding. After secondary grinding, perform a post-heat treatment at a temperature of 600 °C for 2 h to obtain the NVPF@CNF10-600-2 composite material.

[0125] Example 7

[0126] This Example 7 provides a preparation method of the KVPF@CNT01-650-1 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0127] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of KF, NH4VO3, and NH4H2PO4 according to the ratio of K:V:P:F = 1:1:1:1, dissolve the weighed KF in 30 mL of ultrapure water, and add a certain amount of oxalic acid as a chelating agent, and stir magnetically to obtain an aqueous solution of KF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of KF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0128] Step B: Add CNT-NO2 (nitrated carbon nanotubes) with a mass of 0.1% of KVPO4F to a beaker containing pure water, and perform ice-water bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-NO2 dispersion.

[0129] Step C: Mix the CNT-NO2 dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0130] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Blast-dry the sol-gel precursor at 80 °C for 12 h, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite precursor;

[0131] Step E: Put the fluorophosphate composite precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 350 °C for 6 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice, and then perform a post-heat treatment at a temperature of 650 °C for 1 h to obtain the KVPF@CNT01-650-1 composite material.

[0132] Example 8

[0133] This Example 8 provides a preparation method of the KVPF@CNT005-650-1 composite material, which specifically includes steps A to E. Among them, steps A and B have no sequential order.

[0134] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of KF, NH4VO3, and NH4H2PO4 according to the ratio of K:V:P:F = 1:1:1:1, dissolve the weighed KF in 30 mL of ultrapure water, and add a certain amount of oxalic acid as a chelating agent, and stir magnetically to obtain an aqueous solution of KF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of KF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0135] Step B: Add CNT-NO2 (nitrated carbon nanotubes) with a mass of 0.05% of KVPO4F to a beaker containing pure water, and perform ice-water bath ultrasonic dispersion in an ultrasonic cell disruptor to obtain a CNT-NO2 dispersion.

[0136] Step C: Mix the CNT-NO2 dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0137] Step D: Place the mixed solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 100 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 4 h to obtain a blue sol-gel precursor (gel-like material). Bake the sol-gel precursor at 90 °C for 12 h under forced air drying, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite material precursor;

[0138] Step E: Put the fluorophosphate composite material precursor into a tube furnace, and perform a pre-heat treatment at a temperature of 450 °C for 3.5 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, perform secondary grinding. After secondary grinding, perform a post-heat treatment at a temperature of 650 °C for 1 h to obtain the KVPF@CNT005-650-1 composite material.

[0139] In order to verify the technical effects of the preparation method of the embodiments of the present application, Comparative Examples 1 to 3 were also designed in the embodiments of the present application, and the structural and performance characterizations of the electrode materials prepared in Examples 1-8 of the present application and Comparative Document Examples 1-3 were carried out.

[0140] Comparative Example 1

[0141] This Comparative Example 1 provides a preparation method of NVPF-6004 material, including Step A to Step C.

[0142] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0143] Step B: Place the fluorophosphate precursor solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 80 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Bake the sol-gel precursor at 80 °C for 10 h under forced air drying, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate material precursor;

[0144] Step C: Put the fluorophosphate material precursor into a tube furnace, and conduct a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice. After the second grinding, conduct a post-heat treatment at a temperature of 600 °C for 4 h to obtain the NVPF-6004 material.

[0145] Comparative Example 2

[0146] This Comparative Example 2 provides a preparation method of the NVPF@CNT-600-8 composite material, which specifically includes Steps A to E. Among them, Steps A and B have no sequential order.

[0147] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of NaF, NH4VO3, and NH4H2PO4 according to the ratio of Na:V:P:F = 3:2:2:3, dissolve the weighed NaF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of NaF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of NaF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain a fluorophosphate precursor solution.

[0148] Step B: Add CNT (carbon nanotube) with a mass of 5% of Na3V2(PO4)2F3 to a beaker filled with pure water, and perform ultrasonic dispersion in an ice-water bath in an ultrasonic cell disruptor to obtain a CNT dispersion.

[0149] Step C: Mix the CNT dispersion with the fluorophosphate precursor solution to obtain a mixed solution;

[0150] Step D: Place the mixed solution on a magnetic heating stirrer and conduct oil bath heating, where the temperature of the oil bath heating is 80 °C and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 8 h to obtain a blue sol-gel precursor (gel-like material). Dry the sol-gel precursor at 80 °C for 10 h in a blast dryer, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate composite electrode material precursor;

[0151] Step E: Put the fluorophosphate composite electrode material precursor into a tube furnace, and conduct a pre-heat treatment at a temperature of 350 °C for 8 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice. After the second grinding, conduct a post-heat treatment at a temperature of 600 °C for 8 h to obtain the NVPF@CNT-600-8 composite material.

[0152] Comparative Example 3

[0153] This Comparative Example 3 provides a preparation method of the KVPF-6501 material, including Step A to Step C.

[0154] Step A: Provide a fluorophosphate precursor solution. Specifically, after weighing a certain mass of KF, NH4VO3, and NH4H2PO4 according to the ratio of K:V:P:F = 1:1:1:1, dissolve the weighed KF in 30 mL of ultrapure water, and add a certain amount of citric acid monohydrate as a chelating agent, and stir magnetically to obtain an aqueous solution of KF; at the same time, dissolve NH4VO3 and NH4H2PO4 in 30 mL of ultrapure water respectively, and stir magnetically to obtain an aqueous solution of NH4VO3 and an aqueous solution of NH4H2PO4; finally, add the aqueous solution of KF, the aqueous solution of NH4VO3, and the aqueous solution of NH4H2PO4 into a large beaker in sequence, rinse three times, and stir magnetically to obtain the fluorophosphate precursor solution.

[0155] Step B: Place the fluorophosphate precursor solution on a magnetic heating stirrer for oil bath heating. Among them, the temperature of the oil bath heating is 90 °C, and the rotation speed of the magnetic stirring is 400 r / min. Under this condition, continuously heat and evaporate the solvent, and stir for about 6 h to obtain a blue sol-gel precursor (gel-like material). Dry the sol-gel precursor at a temperature of 100 °C for 10 h under forced air, and grind it for 30 min after drying to obtain a uniformly ground powdery material, forming a fluorophosphate electrode material precursor;

[0156] Step C: Put the fluorophosphate electrode material precursor into a tube furnace, and conduct a pre-heat treatment at a temperature of 400 °C for 4 h under the protection of an Ar atmosphere. After the pre-heat treatment is completed, grind it twice. After the second grinding, conduct a post-heat treatment at a temperature of 650 °C for 1 h to obtain the NVPF-6004 material.

[0157] The specific results of the structure and performance characterization are as follows:

[0158] Figure 1 Shows the microscopic TEM image of the NVPF-6004 material synthesized in Comparative Example 1; Figure 2 Shows the microscopic TEM image of the NVPF@CNT001-600-35 composite material synthesized in Example 2; Figure 3Shows the microscopic TEM image of the NVPF@CNT05-600-35 composite material synthesized in Example 3; Figure 4 Shows the microscopic TEM image of the NVPF@CNT1-600-35 composite material synthesized in Example 4.

[0159] Figures 2 to 4 Displays the particle sizes of the carbon-coated fluorophosphate composite materials synthesized at the same sintering temperature. Among them, the average particle size of the NVPF-6004 material is ∼23 nm; the average particle size of the NVPF@CNT001-600-35 composite material is ∼48 nm; the average particle size of the NVPF@CNT05-600-4 composite material is ∼48 nm; the average particle size of the NVPF@CNT1-600-35 composite material is ∼48 nm, indicating that adding CNT-COOH (carboxylated carbon nanotubes) during the sol-gel synthesis of fluorophosphate is beneficial to promoting the grain growth of the fluorophosphate composite material, and with the increase in the content of CNT-COOH (carboxylated carbon nanotubes), the primary particle size of the fluorophosphate composite material sintered and formed at the same temperature and time increases significantly.

[0160] Figure 5 Shows the XRD patterns of the NVPF-6004 material synthesized in Comparative Example 1, the NVPF@CNT001-600-35 composite material synthesized in Example 1, the NVPF@CNT05-600-35 composite material synthesized in Example 2, the NVPF@CNT1-600-35 material synthesized in Example 3, and the NVPF@CNT01-700-01 composite material synthesized in Example 4.

[0161] According to Figure 5 It can be clearly seen that with the addition of CNT-COOH (carboxylated carbon nanotubes), the crystallization performance (XRD peak intensity) of the fluorophosphate composite material has been significantly improved, further proving that adding CNT-COOH (carboxylated carbon nanotubes) during the sol-gel synthesis of fluorophosphate is beneficial to promoting the crystallization and grain growth of the fluorophosphate composite material. Among them, Example 4 can obtain the same crystallization performance as Examples 1-3 within a sintering time of 0.1 h, indicating that adding CNT-COOH (carboxylated carbon nanotubes) during the sol-gel synthesis of fluorophosphate can effectively shorten the sintering time, save labor and energy, improve the production efficiency of equipment, and reduce the material cost.

[0162] Figure 6The charge-discharge curves of the NVPF-6004 material electrode synthesized in Comparative Example 1, the NVPF@CNT001-600-35 composite material electrode synthesized in Example 1, the NVPF@CNT05-600-35 composite material electrode synthesized in Example 2, and the NVPF@CNT1-600-35 composite material electrode synthesized in Example 3 are shown.

[0163] Figure 7 The cycling performance graphs of the NVPF-6004 material electrode synthesized in Comparative Example 1, the NVPF@CNT001-600-35 composite material electrode synthesized in Example 1, the NVPF@CNT05-600-35 composite material electrode synthesized in Example 2, and the NVPF@CNT1-600-35 composite material electrode synthesized in Example 3 are shown.

[0164] According to Figure 6 and Figure 7 It can be seen that during the sol-gel synthesis process of fluorophosphate, the polarization of the battery assembled with the fluorophosphate composite material prepared by adding CNT-COOH (carboxylated carbon nanotubes) is reduced, and the specific capacity is significantly improved; at the same time, the capacity decay rate of the fluorophosphate composite material electrode shows a significant decrease with the addition of CNT-COOH (carboxylated carbon nanotubes), and the cycle life is significantly improved.

[0165] Figure 8 The cycling performance graphs at a 1C rate of the NVPF-6004 material synthesized in Comparative Example 1, the NVPF@CNT-600-8 composite material electrode synthesized in Comparative Example 2, and the NVPF@CNT001-600-35 composite material electrode synthesized in Example 1 are shown.

[0166] According to Figure 8 It can be seen that the capacity retention rates of the NVPF-6004 material, the NVPF@CNT-600-8 composite material electrode, and the NVPF@CNT001-600-35 composite material electrode at a 1C rate are 73.3%, 76.3%, and 93.3% respectively, indicating that adding carbon nanotubes during the sol-gel synthesis process of fluorophosphate has no obvious effect on improving the specific capacity and cycle stability, but adding CNT-COOH (carboxylated carbon nanotubes) can greatly improve the electrode specific capacity and cycle stability. Therefore, adding functionalized carbon materials during the sol-gel synthesis process of fluorophosphate in the examples of this application significantly improves the specific capacity and cycle stability, indicating that functionalized carbon nanotubes play a very important role in the synthesis of fluorophosphate composites.

[0167] Figure 9 The SEM image of the NVPF@CNT001-600-35 composite material electrode synthesized in Example 1 after 1000 cycles is shown.

[0168] According to Figure 9 It can be seen that after 1000 cycles of the NVPF@CNT001-600-35 composite electrode, the two sides of the electrode cracks are bridged by CNT (carbon nanotubes), indicating that the CNT-COOH (carboxylated carbon nanotubes) added during the sol-gel synthesis of fluorophosphate can anchor the fluorophosphate, thereby effectively inhibiting the cracking on the electrode surface.

[0169] Figure 10 The TEM image of the NVPF@CNT001-600-35 composite electrode synthesized in Example 1 after 1000 cycles is shown.

[0170] According to Figure 10 It can be seen that after 1000 cycles of the NVPF@CNT001-600-35 composite electrode, it can still maintain a complete structure and good crystallization performance, and is anchored around the carbon nanotubes, indicating that the addition of CNT-COOH (carboxylated carbon nanotubes) can anchor the fluorophosphate particles and inhibit the fragmentation of secondary particles.

[0171] Figure 11 The XRD patterns of the NVPF-6004 material synthesized in Comparative Example 1, the NVPF@CNF1-600-2 composite material synthesized in Example 5, and the NVPF@CNF10-600-2 composite material synthesized in Example 6 are shown.

[0172] According to Figure 11 It can be seen that after adding CNF-SO3H (sulfonated carbon fiber) to the sol-gel synthesis of fluorophosphate, the crystallization performance of the fluorophosphate composite material has been significantly improved, proving that sulfonated carbon fiber can promote the crystallization and grain growth of the fluorophosphate composite material.

[0173] Figure 12 The SEM image of the KVPF-6501 material synthesized in Comparative Example 3 is shown; Figure 13 The SEM image of the KVPF@CNT01-650-1 composite material synthesized in Example 7 is shown; Figure 14 The SEM image of the KVPF@CNT005-650-1 composite material synthesized in Example 8 is shown.

[0174] Figures 12 to 14 It shows that the addition of CNT-OH (hydroxylated carbon nanotubes) to the sol-gel synthesis of fluorophosphate and sintering at the same temperature and time significantly increases the primary particle size of the fluorophosphate composite material, indicating that the addition of nitrated carbon nanotubes is beneficial to the grain growth of the fluorophosphate composite material.

[0175] Figure 15XRD patterns of the KVPF-6501 material synthesized in Comparative Example 3, the KVPF@CNT01-650-1 composite material synthesized in Example 7, and the KVPF@CNT005-650-1 composite material synthesized in Example 8 are shown.

[0176] According to Figure 15 It can be seen that adding CNT-NO2 (nitrated carbon nanotubes) in the sol-gel synthesis of fluorophosphate significantly improves the crystallization performance of the fluorophosphate composite material, thus proving that adding functionalized carbon nanotubes in the sol-gel synthesis of fluorophosphate is beneficial to promoting the crystallization and grain growth of the fluorophosphate composite material.

[0177] According to Figure 16 and Figure 17 It can be seen that the polarization of the battery assembled with the fluorophosphate composite material prepared by adding CNT-NO2 (nitrated carbon nanotubes) during the sol-gel synthesis process of fluorophosphate decreases, and the specific capacity increases significantly; at the same time, the capacity decay rate of the fluorophosphate composite material electrode decreases significantly with the addition of CNT-NO2 (nitrated carbon nanotubes), and the cycle life increases significantly.

[0178] Based on the above structural and performance characterizations, it can be known that the embodiments of the present application use functionalized carbon materials to modify the fluorophosphate electrode material and synthesize it by the sol-gel method, effectively solving the problems of poor crystallization performance, many surface defects, long sintering time, insufficient electronic conductivity in the synthesis of fluorophosphate-carbon material composites by the sol-gel method in the prior art, and the easy fragmentation and cracking of the composite electrode material and electrode structure morphology caused by volume change during the cycle.

[0179] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0180] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting the present application; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A preparation method of a fluorophosphate composite electrode material, characterized in that, It includes the following steps: Step A: Provide a fluorophosphate precursor solution; Step B: Disperse the functionalized carbon material in water to obtain a dispersion; the functionalized carbon material is selected from any one of hydroxylated carbon materials, carboxylated carbon materials, aminated carbon materials, sulfonated carbon materials, and nitrated carbon materials; Step C: Mix the dispersion with the fluorophosphate precursor solution to obtain a mixed solution; Step D: Evaporate the mixed solution to form a gel-like material, and then dry and grind the gel-like material to form a fluorophosphate composite electrode material precursor; Step E: In an anaerobic atmosphere, perform pre-heat treatment and post-heat treatment on the fluorophosphate composite electrode material precursor to obtain the fluorophosphate composite electrode material; wherein, the temperature of the pre-heat treatment is 350 °C and the time is 0.1 - 10 h; the temperature of the post-heat treatment is 600 - 700 °C and the time is 0.1 - 3.5 h; Step A and Step B are not in a sequential order; The fluorophosphate is Na3V2(PO4)2F3 or KVPO4F.

2. The preparation method of the fluorophosphate composite electrode material according to claim 1, characterized in that, The carbon material of the functionalized carbon material includes at least one of graphene, carbon nanotubes, and nanofibers.

3. The preparation method of the fluorophosphate composite electrode material according to claim 2, characterized in that, The method for preparing the dispersion includes: Place the functionalized carbon material in an ultrasonic cell disruptor for ice-water bath dispersion to obtain the dispersion.

4. The preparation method of the fluorophosphate composite electrode material according to claim 1, wherein The method for preparing the fluorophosphate precursor solution includes: Dissolve a phosphorus source, a fluorine source, a transition metal source, an alkali metal source, and a chelating agent in water to obtain the fluorophosphate precursor solution; The alkali metal source is one or more of oxides, carbonates, phosphates, or alkalis of sodium or potassium elements; The transition metal source is one or more of oxides, phosphates, carbonates, or ammonium salts of vanadium; The phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, and ammonium phosphate; The chelating agent is one or more of oxalic acid or citric acid.

5. The preparation method of the fluorophosphate composite electrode material according to claim 1, wherein When the dispersion is mixed with the fluorophosphate precursor solution, the addition amount of the functionalized carbon material is 0.01 - 10% of the target yield of the fluorophosphate.

6. The preparation method of the fluorophosphate composite electrode material according to claim 1, wherein, The evaporation temperature of the mixed solution is 70 - 100 °C and the time is 2 - 24 h; and the drying temperature of the gel-like material is 60 - 100 °C.

7. A fluorophosphate composite electrode material formed by the preparation method according to any one of claims 1 - 6.

8. Use of the fluorophosphate composite electrode material according to claim 7 in the manufacture of electrodes for metal ion batteries.

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