Preparation method of a sodium ion battery positive electrode material titanium-based phosphate

Abstract

The application discloses a preparation method of a sodium ion battery positive electrode material titanium-based phosphate. The method comprises the following steps: firstly, preparing NaTi2(PO4)3 carbon composite material by using a solid phase method; and secondly, preparing Na3Ti2(PO4)3 material by electrochemically embedding sodium into the NaTi2(PO4)3 carbon composite material in an aqueous solution, wherein the sodium source is sodium ions in a deoxygenated aqueous solution, and the Na3Ti2(PO4)3 is a poly-anion material with a sodium super ionic conductor structure. The preparation method of the sodium ion battery positive electrode material titanium-based phosphate is characterized in that Na3Ti2(PO4)3 material is prepared by simply electrochemically embedding sodium into NaTi2(PO4)3 in an aqueous solution. The method has the advantages of simple process, strong operability, mild preparation condition, low risk coefficient, easy realization of mass production, and realization of batch preparation of Na3Ti2(PO4)3 material with high stability and high specific capacity.

Description

Technical Field

[0001] The invention relates to a method for preparing titanium-based phosphate, a positive electrode material for sodium ion batteries. Background Art

[0002] Sodium-ion batteries have strong application potential in the field of energy storage due to their advantages such as low cost, excellent low-temperature performance and cycle stability. Among them, as a component that limits the energy density of batteries, the research on positive electrode materials has attracted much attention. In the existing sodium-ion battery energy storage system, the positive electrode materials mainly include layered oxides, Prussian blue analogues and polyanions. Polyanion compounds are three-dimensional framework structures composed of strong covalent bonds, so they have high structural stability. Among them, Na3Ti2(PO4)3 is a typical sodium superion conductor (NASICON) structure material with a theoretical specific capacity of up to 135mAh / g. The stable crystal space structure is conducive to the battery cycle of the material, and the polyanion compound gives it excellent thermal stability, so it has great potential in the application of sodium-ion batteries. Due to Ti 3+ Strong reducing property, traditional use of Ti 4+ The solid-phase method for preparing Na3Ti2(PO4)3 requires harsh conditions and a high risk factor in a reducing atmosphere (http: / / dx.doi.org / 10.1016 / j.elecom.2014.04.003; dx.doi.org / 10.1021 / ja311044t|J.Am.Chem.Soc.2013,135,3897-3903). However, Na3Ti2(PO4)3 can exist stably in non-oxygen aqueous conditions (http: / / dx.doi.org / 10.1016 / j.elecom.2014.04.003). Therefore, it is feasible to prepare Na3Ti2(PO4)3 by simple electrochemical sodium insertion in aqueous solutions using NaTi2(PO4)3 with similar structure and good environmental compatibility. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing titanium-based phosphate, a positive electrode material for sodium ion batteries, by using NaTi2(PO4)3 to prepare Na3Ti2(PO4)3 material through simple electrochemical sodium insertion in an aqueous solution. The method has simple process, strong operability, mild preparation conditions, low risk factor, and is easy to mass produce, and can realize batch preparation of Na3Ti2(PO4)3 materials with high stability and high specific capacity.

[0004] The technical solution for achieving the above object is: a method for preparing titanium-based phosphate as a positive electrode material for sodium ion batteries, wherein the molecular formula of the titanium-based phosphate as a positive electrode material for sodium ion batteries is Na3Ti2(PO4)3, and the preparation method comprises the following steps:

[0005] S1, preparing NaTi2(PO4)3 carbon composite material by solid phase method;

[0006] S2, preparing Na3Ti2(PO4)3 material by electrochemically embedding sodium in NaTi2(PO4)3 carbon composite material in aqueous solution, the sodium source is sodium ion in deoxygenated aqueous solution, specifically: uniformly mixing NaTi2(PO4)3 carbon composite material and binder in solvent, coating on current collector, drying, and then using as working electrode in sodium-containing deoxygenated aqueous solution, using inert conductive material electrode as counter electrode, and realizing Na + embedding, washing the sample with deoxygenated water in inert atmosphere environment after reaction, and finally drying in anaerobic environment to obtain Na3Ti2(PO4)3, which is a sodium superionic conductor structure polyanion material.

[0007] The preparation method of the above-mentioned sodium ion battery positive electrode material titanium-based phosphate, in step S1, the specific process of preparing NaTi2(PO4)3 carbon composite material by solid phase method is: uniformly mixing Na source material, Ti source material, P source material and carbon source material, drying to obtain precursor powder; sintering the precursor powder in a sintering kiln under inert atmosphere protection, crushing after cooling to obtain NaTi2(PO4)3 carbon composite material;

[0008] The molar ratio of Na:Ti:P in the Na source material, Ti source material and P source material is 1:2:3, and the mass ratio of the carbon material in the NaTi2(PO4)3 carbon composite material is 1%-30%; The preparation method of the above-mentioned sodium ion battery positive electrode material titanium-based phosphate, wherein the Na source material uses one or more of Na2CO3, NaOH, Na2SO4 and NaH2PO4;

[0009] The Ti source material uses one or more of TiO2, tetrabutyl titanate and titanium tetrachloride;

[0010] The P source material uses one or more of H3PO4, NH4H2PO4, (NH4)2HPO4 and P2O5;

[0011] The carbon source material uses one or more of acetylene black, activated carbon, graphite, carbon fiber, graphene and carbon nanotube.

[0012] The preparation method of the above-mentioned sodium ion battery positive electrode material titanium-based phosphate, wherein the Na source material, Ti source material, P source material and carbon source material are uniformly mixed by one or more of dry ball milling, wet ball milling and high-speed dispersion mixing;

[0013] The drying method of the mixed Na source material, Ti source material, P source material and carbon source material is one or several of fluidized bed drying, spray drying and disc drying;

[0014] The inert atmosphere of the sintering kiln is nitrogen and / or argon;

[0015] The sintering temperature of the sintering kiln is 650-1050℃, the heating rate is 1-5℃ / min, and the holding time is 4-24h;

[0016] The cooling method after sintering is active cooling and / or natural cooling;

[0017] The crushing method after cooling is one or more of mechanical crushing, air jet milling and millstone crushing.

[0018] The mass ratio of the NaTi2(PO4)3 carbon composite material to the binder in step S2 of the above preparation method of the sodium ion battery positive electrode material titanium-based phosphate is (95-99.9):(0.1-5);

[0019] The surface density of the NaTi2(PO4)3 carbon composite material and the binder mixed uniformly in the solvent and coated on the current collector ranges from 0.1 to 5 g / cm 2 .

[0020] The above preparation method of the sodium ion battery positive electrode material titanium-based phosphate, wherein the binder uses one or several of polyvinylidene fluoride, polytetrafluoroethylene and butadiene rubber;

[0021] The solvent uses N-methyl pyrrolidone or ion-free water;

[0022] The current collector uses a stainless steel corrosion-resistant current collector.

[0023] The above preparation method of the sodium ion battery positive electrode material titanium-based phosphate, wherein in step S2, the sodium salt in the deoxygenated sodium-containing aqueous solution is one or several of soluble sodium-containing compounds such as sodium sulfate, sodium carbonate, sodium nitrate, sodium acetate and sodium citrate; and the inert conductive material electrode uses one of carbon rods, graphite plates and graphite felt;

[0024] The current density in the electrochemical method of realizing Na + The current density in the electrochemical method of realizing Na

[0025] The flushing frequency of the sample with deoxygenated water is 1-3 times.

[0026] The above preparation method of the sodium ion battery positive electrode material titanium-based phosphate, wherein the drying method in an oxygen-free environment is vacuum drying or inert atmosphere drying.

[0027] The preparation method of the sodium ion battery positive electrode material titanium-based phosphate of the present application utilizes NaTi2(PO4)3 to prepare Na3Ti2(PO4)3 material by simple electrochemical sodium intercalation in aqueous solution, which has simple process, strong operability, mild preparation conditions, low risk coefficient, easy realization of mass production, and can realize batch preparation of Na3Ti2(PO4)3 material with high stability and high specific capacity. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 XRD pattern of the sodium ion battery positive electrode material titanium-based phosphate obtained by the preparation method of the present application;

[0029] Figure 2 0.1C first charge-discharge curve diagram of the sodium ion battery positive electrode material titanium-based phosphate obtained by the preparation method of the present application;

[0030] Figure 3 Cycle performance diagram of the sodium ion battery positive electrode material titanium-based phosphate obtained by the preparation method of the present application. DETAILED DESCRIPTION

[0031] In order for those skilled in the art to better understand the technical solutions of the present application, the specific embodiments thereof will be described in detail below with reference to the accompanying drawings:

[0032] Please refer to Figure 1 In the embodiments of the present application, the sodium ion battery positive electrode material titanium-based phosphate Na3Ti2(PO4)3 is made by the following preparation method:

[0033] S1, Na2CO3 is used as Na source material, TiO2 is used as Ti source material, NH4H2PO4 is used as P source material, and acetylene black is used as carbon source material; the molar ratio of Na source material, Ti source material and P source material is 1:2:3, and the mass ratio of Na3Ti2(PO4)3 and carbon source material is 0.95:0.05; the Na source material, Ti source material, P source material and carbon source material are uniformly mixed by ball milling, and then a precursor powder is obtained by spray drying; the precursor powder is sintered in a sintering kiln under nitrogen protection, the heating rate is 1-5℃ / min, the temperature is raised to 700℃, the holding time is 12 hours, and the sintered powder is subjected to airflow crushing to obtain NaTi2(PO4)3 carbon composite material;

[0034] S2, the prepared NaTi2(PO4)3 carbon composite material is mixed with polyvinylidene fluoride (binder) in N-methylpyrrolidone (solvent) to obtain a slurry, the mass ratio of the NaTi2(PO4)3 carbon composite material to the polyvinylidene fluoride is 98:2, the mixed slurry is coated on a stainless steel current collector, and then dried to obtain a working electrode; sodium sulfate is dissolved in deionized water to obtain a 1 mol / L sodium sulfate solution, and then oxygen contained in the solution is removed by vacuum pumping to obtain a sodium-containing deoxygenated aqueous solution; a graphite electrode is used as a counter electrode; an electrochemical method is used to perform a charging reaction at a current of 200 mA / g; after the charging reaction, the sample is washed with the deoxygenated water in an inert atmosphere; and after drying in an oxygen-free environment, the Na3Ti2(PO4)3 material is obtained. The XRD diffraction pattern of the obtained Na3Ti2(PO4)3 material is shown in Figure 1 , and the Na3Ti2(PO4)3 material is a sodium superionic conductor structure polyanion material.

[0035] Please refer to Figure 2 and Figure 3 , the Na3Ti2(PO4)3 material is used as a positive electrode, a Na sheet is used as a counter electrode, PC is used as a solvent, and sodium perchlorate is used as an electrolyte salt; and a 0.1C first charge-discharge curve is shown in Figure 2 , the battery is first charged and then discharged in a charge-discharge voltage range of 1.5-2.7 V. The specific capacity of the Na3Ti2(PO4)3 is greater than 110 mAh / g, and the Na3Ti2(PO4)3 has a high specific capacity. The cycle performance is shown in Figure 3 , and the capacity retention rate is greater than 99.5% after 150 cycles at 1C, and the Na3Ti2(PO4)3 has a high stability. The Na3Ti2(PO4)3 prepared by the preparation method has excellent electrochemical performance when applied to a sodium ion battery.

[0036] In the preparation method of the sodium ion battery cathode material titanium-based phosphate of the application, in step S1, the Na source material can be one or more of Na2CO3, NaOH, Na2SO4 and NaH2PO4 and the like Na-containing compounds; the Ti source material can be one or more of TiO2, tetrabutyl titanate and titanium tetrachloride and the like Ti-containing compounds; the P source material can be one or more of H3PO4, NH4H2PO4, (NH4)2HPO4 and P2O5 and the like P-containing phosphorus compounds; and the carbon source material can be one or more of acetylene black, activated carbon, graphite, carbon fiber, graphene and carbon nanotube. The mixing of the Na source material, the Ti source material, the P source material and the carbon source material can be one or more of dry ball milling, wet ball milling and high-speed dispersion mixing; the drying of the mixed Na source material, the Ti source material, the P source material and the carbon source material can be one or more of fluidized bed drying, spray drying and disc drying; the inert atmosphere of the sintering kiln can be nitrogen and / or argon; the sintering temperature of the sintering kiln is 650-1050℃, the heating rate is 1-5℃ / min; the holding time is 4-24h; the cooling after sintering is active cooling and / or natural cooling; and the crushing after cooling is one or more of mechanical crushing, jet mill crushing and millstone crushing.

[0037] In step S2, the mass ratio of the NaTi2(PO4)3 carbon composite material to the binder is (95-99.9):(0.1-5); the surface density of the NaTi2(PO4)3 carbon composite material coated on the current collector after being mixed with the binder in the solvent ranges from 0.1 to 5 g / cm2. 2 The binder can be one or more of polyvinylidene fluoride, polytetrafluoroethylene and styrene-butadiene rubber; the solvent can be N-methyl pyrrolidone or ion-free water; the current collector can be a stainless steel corrosion-resistant current collector. The sodium salt in the deoxygenated sodium-containing aqueous solution can be one or more of sodium sulfate, sodium carbonate, sodium nitrate, sodium acetate and sodium citrate; the inert conductive material electrode can be one of a carbon rod, a graphite plate and a graphite felt; and the current density in the electrochemical method for realizing Na + The current density in the electrochemical method for realizing Na

[0038] In summary, the preparation method of the sodium ion battery cathode material titanium-based phosphate of the application uses NaTi2(PO4)3 to prepare Na3Ti2(PO4)3 material by simple electrochemical sodium intercalation in an aqueous solution, and the low-cost electrochemical method has the advantages of simple process, strong operability, mild preparation conditions, low risk coefficient, easy realization of mass production, and batch preparation of Na3Ti2(PO4)3 material with high stability and high specific capacity.

[0039] Those skilled in the art will recognize that the above-described embodiments are merely illustrative of the application and should not be construed as limiting the scope of the application. Variations and modifications to the described embodiments can be made based on what is described above without departing from the scope of the application as recited in the following claims.

Claims

1. A method for preparing a titanium-based phosphate as a positive electrode material for a sodium ion battery, wherein the molecular formula of the titanium-based phosphate as a positive electrode material for a sodium ion battery is Na3Ti2(PO4)3, characterized in that: The preparation method comprises the following steps: S1, preparing NaTi2(PO4)3 carbon composite material by solid phase method; the specific process of preparing NaTi2(PO4)3 carbon composite material by solid phase method is as follows: uniformly mixing Na source material, Ti source material, P source material and carbon source material, and obtaining precursor powder after drying; sintering the precursor powder in a sintering kiln protected by inert atmosphere, and crushing the precursor powder after cooling to obtain NaTi2(PO4)3 carbon composite material; The molar ratio of Na:Ti:P in the Na source material, the Ti source material and the P source material is 1:2:3, and the mass proportion of the carbon source material in the NaTi2(PO4)3 carbon composite material is 1%-30%; S2, in an aqueous solution, NaTi2(PO4)3 carbon composite material is electrochemically embedded with sodium to prepare Na3Ti2(PO4)3 material, specifically: NaTi2(PO4)3 carbon composite material and binder are mixed evenly in a solvent, and coated on a current collector, and after drying, it is used as a working electrode in a sodium-containing deoxygenated aqueous solution, and an inert conductive material electrode is used as the counter electrode, and Na is realized by an electrochemical method. + After embedding, the sample was rinsed with deoxygenated water in an inert atmosphere and finally dried in an oxygen-free environment to obtain Na3Ti2(PO4)3, which is a polyanion material with a sodium superion conductor structure. The sodium salt in the deoxygenated sodium-containing aqueous solution is one or more of sodium sulfate, sodium carbonate, sodium nitrate, sodium acetate and sodium citrate; the inert conductive material electrode is one of carbon rod, graphite plate and graphite felt; Electrochemical method to achieve Na + The current density during embedding is 0-400mA / g, and the voltage range is -1.3 to -1.6V. The number of times the sample was rinsed with deoxygenated water was 1-3 times; The mass ratio of the NaTi2(PO4)3 carbon composite material to the binder is (95-99.9):(0.1-5); The NaTi2(PO4)3 carbon composite material and the binder are mixed uniformly in a solvent and coated on the current collector to have a surface density in the range of 0.1-5 g / cm 2 .

2. The method for preparing a titanium-based phosphate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: The Na source material is one or more of Na2CO3, NaOH, Na2SO4 and NaH2PO4; The Ti source material is one or more of TiO2, tetrabutyl titanate and titanium tetrachloride; The P source material is one or more of H3PO4, NH4H2PO4, (NH4)2HPO4 and P2O5; The carbon source material is one or more of acetylene black, activated carbon, graphite, carbon fiber, graphene and carbon nanotubes.

3. The method for preparing a titanium-based phosphate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: The Na source material, the Ti source material, the P source material and the carbon source material are uniformly mixed by one or more of dry ball milling, wet ball milling and high-speed dispersion mixing; After the Na source material, Ti source material, P source material and carbon source material are uniformly mixed, a drying method is adopted, which is one or more of fluidized bed drying, spray drying and tray drying; The inert atmosphere of the sintering furnace is nitrogen and / or argon; The sintering temperature of the sintering kiln is 650-1050°C, the heating rate is 1-5°C / min, and the holding time is 4-24h; Cooling after sintering adopts active cooling and / or natural cooling; The pulverization method after cooling is one or more of mechanical pulverization, air flow mill pulverization and grinding disc pulverization.

4. The method for preparing a titanium-based phosphate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: The binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene and styrene-butadiene rubber; The solvent is N-methylpyrrolidone or deionized water; The current collector is made of stainless steel anti-corrosion current collector.

5. The method for preparing a titanium-based phosphate as a positive electrode material for sodium ion batteries according to claim 1, characterized in that: In step S2, the drying method in an oxygen-free environment is vacuum drying or inert atmosphere drying.

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