279 results about "Vanadium phosphate" patented technology

The invention provides a lithium iron phosphate composite material and a preparation method thereof, a positive pole piece and a secondary battery, the lithium iron phosphate composite material comprises a core layer, the core layer comprises an inner core, a coating layer coating the inner core, and a mutual doping layer located between the coating layer and the inner core; wherein the material of the inner core comprises lithium iron phosphate, the material of the coating layer comprises sodium vanadium fluorophosphate, and the material of the mutual doping layer comprises vanadium-doped lithium iron phosphate. A core layer of the lithium iron phosphate composite material adopts lithium iron phosphate as an inner core, the inner core is coated with sodium vanadium fluorophosphate, and a mutual doping layer structure is arranged between the inner core and a coating layer, so that mixed migration of Li / Na ions is realized, and meanwhile, the lithium iron phosphate composite material has excellent ion diffusion efficiency, relatively high theoretical specific capacity and a relatively high voltage platform; the material has low powder resistivity, a stable charge-discharge platform and excellent cycle performance, and the electrochemical performance such as energy density and cycle performance is effectively improved.

The invention discloses a carbon-coated high-entropy NASICON positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of sodium ion battery electrode materials. The method comprises the following steps: adding a vanadium source, a carbon source, a chromium source, an iron source, a manganese source, a zinc source, an aluminum source, a sodium source and a phosphorus source into deionized water, heating and dissolving to obtain a clear solution; and heating the solution to form gel, and then carrying out the steps of vacuum drying, crushing, pre-sintering, calcining and the like to obtain the Na3V2-y (CrFeMnZnAl) y (PO4) 3 / C (0 < y < 1) positive electrode material. The positive electrode material has a stable NASICON structure, and the morphology is of a scaly structure. According to the invention, a high-entropy doping mode is adopted to replace part of vanadium sites in sodium vanadium phosphate, and the conductivity of the positive electrode material is improved through carbon coating, so that the prepared positive electrode material has relatively good cycling stability and rate capability.

The invention discloses a preparation method of a sodium ferromanganese vanadium phosphate material of a sodium battery positive electrode. The preparation method comprises the following steps: S1, preparing a hydrophosphate solution and a manganous salt solution; and S2, adding the hydrophosphate solution into the manganous salt solution, and reacting to obtain the manganous hydrogen phosphate crystal nucleus slurry. And S3, filtering and washing the manganese hydrogen phosphate crystal nucleus slurry, adding water into the manganese hydrogen phosphate material to prepare slurry, heating to 85-95 DEG C, respectively adding a ferrous source and a phosphorus salt solution, and reacting to obtain the manganese iron hydrogen phosphate slurry. And S4, filtering, washing and drying the iron manganese hydrogen phosphate slurry, adding water into the dried slurry to prepare slurry, adding phosphoric acid, heating to 90-100 DEG C, reacting to obtain an iron manganese phosphate compound precipitate, and filtering, washing and drying the precipitate to obtain an iron manganese phosphate material. The sodium manganese iron vanadium phosphate product is prepared by adopting a coprecipitation method and high-temperature sintering, and the method has the advantages of short process flow, simple process, only one-time sintering, low energy consumption and the like.

The invention belongs to the technical field of sodium ion batteries, and particularly relates to a reference electrode and a preparation method and application thereof, the reference electrode comprises a metal substrate and a coating layer coating the metal substrate; the coating layer comprises sodium vanadium phosphate, a conductive agent, a binder and a solvent. The reference electrode disclosed by the invention has the beneficial effects that the reference electrode adopts sodium vanadium phosphate with stable potential as a raw material for preparing the reference electrode, so that the problem of poor chemical stability of metal sodium is fundamentally solved, and pre-activation is not needed; the assembled flexibly-packaged sodium ion battery reference electrode system can be directly adopted for in-situ activation, so that the method is easy to test, popularize and apply, and has a wide application field; when the three-electrode battery cell is manufactured, the reference electrode is directly implanted into the battery cell, the manufacturing process is simple and safe, the test stability is improved, and the problems of sodium dendrites, complex sodium modification process and high sodium modification cost are avoided.

The invention provides a sodium vanadium fluorophosphate in-situ coated sodium ferric sulfate / carbon composite material and a preparation method thereof.The preparation method comprises the steps that raw materials including a reducing agent, an iron source, a sodium source and a carbon source are added into absolute ethyl alcohol to be stirred, sanded and mixed, and after obtained slurry is subjected to spray drying, the slurry is sintered and cooled in the argon atmosphere to obtain the sodium ferric sulfate / carbon composite material; mixing the sodium ferric sulfate / carbon composite material dispersion liquid with the sodium vanadium fluorophosphate precursor solution, performing hydrothermal reaction, centrifuging, washing and drying to obtain the sodium vanadium fluorophosphate in-situ coated sodium ferric sulfate / carbon composite material. According to the preparation method, a sodium vanadium fluorophosphate coating layer is generated on the surface of sodium ferric sulfate in situ by combining a low-temperature solid-phase method with a hydrothermal method, so that the sodium vanadium fluorophosphate in-situ coated sodium ferric sulfate / carbon composite material is obtained, the electronic conductivity of the composite material is greatly improved, and the sodium ion diffusion rate is promoted by coating of sodium vanadium fluorophosphate; fe2 + is prevented from being oxidized into Fe3 + due to direct contact between the sodium ferric sulfate and air, so that the air stability of the sodium ferric sulfate is improved.

The invention discloses a composite positive electrode material for realizing sodium ion internal compensation based on electrochemical potential difference as well as a preparation method and application thereof, relates to a sodium ion battery composite positive electrode material as well as a preparation method and application thereof, and aims at solving the problems of polarization increase, capacity reduction and poor rate capability of the existing sodium ion battery positive electrode material at the discharge end and in a low-temperature environment. The composite positive electrode material is formed by compounding a main phase material A and an auxiliary phase material B with the electrochemical potential higher than that of the main phase material A in a physical mode; at the final stage of discharge or at low temperature and high rate, the auxiliary phase spontaneously releases sodium ions to the main phase based on the electrochemical potential difference of the two phases without the action of an external electric field, and the available capacity of the main phase is improved through internal compensation. The specific discharge capacity of the sodium vanadium fluorophosphate and sodium vanadium phosphate composite material is 119.2 mAh g <-1 >, the specific discharge capacities of the sodium vanadium fluorophosphate and sodium vanadium phosphate composite material are 76.4 mAh g <-1 > and 107.4 mAh g <-1 > at the multiplying power of 30 C and the multiplying power of-20 DEG C and the multiplying power of 0.1 C, and the sodium vanadium fluorophosphate and sodium vanadium phosphate composite material can be applied to the field of sodium ion batteries.

The invention discloses a high-performance carbon-coated sodium vanadium fluorophosphate positive electrode material, a sodium ion battery and a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. The preparation method provided by the invention comprises the following steps: (1) heating a mixture containing a sodium source, a vanadium source, a phosphorus source, a fluorine source, a carbon source and water I, stirring until gel is formed, and drying to obtain a precursor; and (2) carrying out ball milling on the precursor, and then placing the precursor in an inert gas atmosphere for heating II to obtain the high-performance carbon-coated sodium vanadium fluorophosphate positive electrode material. By adjusting the proportion of the sodium source, the vanadium source, the phosphorus source and the fluorine source, the prepared sodium vanadium fluorophosphate positive electrode material improves a voltage platform, so that the energy density of a sodium ion battery is improved, and the assembled sodium ion battery has extremely high capacity and excellent long cycle performance.

The invention belongs to the technical field of sodium ion battery positive electrode materials, and discloses a preparation method and application of an iron ion doped sodium vanadium phosphate positive electrode material. Modification is carried out by doping iron ions in vanadium sites and taking citric acid as a carbon source for coating, iron nitrate nonahydrate serves as an iron source to participate in the modification process, meanwhile, citric acid is used for carrying out carbon coating on the material, and the citric acid and the doped iron ions synergistically increase the ionic conductivity, so that the problem that the sodium vanadium phosphate material is poor in conductivity is solved. Besides, in the sintering treatment process, the Na3V1.8 Fe0.2 (PO4) 3 / C positive electrode material obtained by doping 0.2 molar weight of iron ions and coating citric acid is always kept in the atmosphere of argon-hydrogen mixed gas, after circulation at the current density of 0.1 C to 20 C, the capacity recovery rate can reach up to 96.1%, and the capacity can still be kept to be 74.1% of the initial capacity at the high rate of 20 C; after 500 cycles under 1C current density, the capacity retention rate is 89.8%, while the capacity retention rate is only 72% after 500 cycles of pure NVP, the rate capability and cycling stability of the material are both improved, and the electrochemical performance of the material is effectively ensured.

The invention provides a preparation method of a carbon-coated manganese-titanium-doped sodium vanadium phosphate positive electrode material, which comprises the following steps: sequentially adding raw materials of a carbon source, a vanadium source, a phosphorus source, a sodium source, a manganese source and a titanium source into deionized water according to a molar ratio, stirring until the solution becomes clear, and carrying out high-temperature calcination through a sol-gel method and a tubular furnace to prepare a Na (4-x) MnV1-XTix (PO4) 3 / C positive electrode material. The target material is of a sea rock similar structure, the surface of the target material is provided with multiple holes, and due to the morphology, the specific surface area of the material is larger, multiple active sites are provided, and the reaction rate is increased. And the surface is coated with carbon, so that the conductivity of the material is greatly improved. Through a double-doping strategy of partially replacing transition metal vanadium sites with titanium and manganese doping, the prepared electrode material has relatively good cycle stability.

A method for preparing sodium vanadium fluorophosphate as a positive electrode material for sodium-ion batteries on the basis of spray drying, which method aims to solve the problems of poor electronic conductivity and fluorine loss in sodium vanadium fluorophosphate as a positive electrode material for sodium-ion batteries. The method comprises dissolving a carbon source, a phosphorus source, a sodium source and a vanadium source in water, and then drying same in a spray dryer to obtain a precursor powder; and then uniformly mixing the precursor powder with a fluorine source, and calcining the resulting mixture for 3-6 h to obtain sodium vanadium fluorophosphate, namely, a positive electrode material for sodium ion batteries. The material is made of micron spherical particles having a core-shell structure, the particle size is about 8 μm, the shell thickness is about 200 nm, the initial specific discharge capacity is 110.60 mAh / g at a rate of 1 C, and the specific discharge capacities are 97.90 mAh / g and 74.70 mAh / g at rates of 10 C and 30 C, respectively. The present invention can be used in the field of sodium-ion batteries.

The invention belongs to the technical field of sodium ion batteries, and particularly relates to a double-carbon-coated bismuth ion doped sodium vanadium phosphate composite material, a preparation method and application thereof. The composite material is Na3BixV2-x (PO4) 3 / C (at) rGO, and x is more than or equal to 0.05 and less than or equal to 0.15. The preparation method of the composite material comprises the following steps: firstly, directly preparing Na3BixV2-x (PO4) 3 / C (at) rGO precursor powder by a one-step method; and calcining the Na < 3 > Bi < x > V < 2-x > (PO4) 3 / C (at) rGO precursor powder to obtain the Na < 3 > Bi < x > V < 2-x > (PO4) 3 / C (at) rGO composite material. The obtained composite material is used as a positive electrode material in a sodium-ion battery and has high reversible specific capacity, the electrochemical performance of the sodium-ion battery is greatly improved, and the battery is high in conductivity, stable in cycle performance and excellent in charge-discharge performance.

The invention provides a chlorine tungsten anion and cation co-doped sodium vanadium phosphate positive electrode material and a preparation method thereof, and belongs to the technical field of energy materials. The positive electrode material is formed by doping V site with W < 4 + > ions and doping (PO4) 3 site with Cl <-> ions, the chemical formula of the positive electrode material is Na < 3-x > V < 2-x > W < x > (PO4) < 3-y > Cl3y / C, x is equal to 0.05, 0.1 and 0.15, and y is equal to 0.09, 0.12 and 0.15; according to the preparation method, ammonium metavanadate, sodium acetate and ammonium dihydrogen phosphate are taken as raw materials, tungsten disulfide and sodium chloride are taken as doping sources, citric acid monohydrate is taken as a chelating agent, and the chlorine tungsten anion and cation co-doped sodium vanadium phosphate electrode material is prepared by a solution gel method, so that the electronic conductivity is improved, and the rate capability and the cycling stability are improved; the preparation method has a good application prospect in sodium ion battery positive electrode materials.

The invention discloses a preparation method of atomic layer deposition synergistic doping modified sodium vanadate, which uses water as solvent, anhydrous sodium iodide and monohydrated vanadium oxyphosphate as sodium source, vanadium source and phosphorus source, and introduces cobalt acetate tetrahydrate and nickel acetate tetrahydrate, and realizes one-step hydrothermal synthesis of HNaV6O assembled by nanosheets and co-embedded with cobalt ions, nickel ions and phosphate ions by synergistically controlling their concentration and ratio, reaction temperature, reaction time and other parameters. 16 ·4H2O nanoflower structure. This method has a simple reaction process, low temperature, easy control, and does not require large equipment and harsh reaction conditions. On this basis, the atomic layer deposition technology was used to successfully realize the cobalt ion, nickel ion and phosphate ion co-embedded HNaV6O with ultra-thin nanoscale metal oxides. 16 Uniform coating of 4H2O positive electrode material. The present invention provides the application of the material in the positive electrode material of sodium ion battery.

The invention relates to the technical field of sodium ion batteries, in particular to a coated modified high-entropy sodium vanadium phosphate positive electrode material as well as a preparation method and application thereof. The coated modified high-entropy sodium vanadium phosphate positive electrode material comprises a core material and a poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) coating layer coated on the surface of the core material, the core material comprises a sodium vanadium phosphate / carbon matrix material and metal elements doped in the sodium vanadium phosphate / carbon matrix material, and the metal elements comprise at least five of Al, Cu, Ru, Ag, Ni, Co, Zn, Ti, Zr, Mg, Mn and Mo elements. The coated modified high-entropy sodium vanadium phosphate positive electrode material provided by the invention can effectively enhance ionic conductivity, electronic conductivity and interface stability of the positive electrode material, can inhibit side reaction between a sodium vanadium phosphate positive electrode and an electrolyte and dissolution of vanadium metal in a circulation process, and has excellent cycle performance and rate capability.

The invention provides a sodium vanadium fluorophosphate positive electrode material and a preparation method and application thereof, and belongs to the technical field of sodium ion battery positive electrode materials. The preparation method comprises the following steps: mixing sodium salt, a vanadium source, a phosphorus source, villiaumite and a carbon source in water, obtaining xerogel by adopting a sol-gel method, calcining to obtain a carbon-coated sodium vanadium fluorophosphate positive electrode material, dispersing the carbon-coated sodium vanadium fluorophosphate positive electrode material in water to form a suspension, adding polyvinyl alcohol and manganese salt, uniformly stirring, heating to evaporate a solvent, and annealing in inert gas to obtain the carbon-coated sodium vanadium fluorophosphate positive electrode material. The carbon and manganese dioxide synergistically co-coated sodium vanadium fluorophosphate positive electrode material is obtained. A sol-gel method and a suspension coating technology are combined to construct the carbon and manganese dioxide dual-coated NVPF composite material, so that the problems of slow sodium ion diffusion kinetics, low electronic conductivity, interface side reaction and the like when the NVPF is used as a sodium ion battery positive electrode material are solved.

According to the transition metal doped vanadium manganese sodium phosphate composite material and the preparation method and application thereof, the specific surface area of the material is remarkably increased by adopting a spray drying-calcining method and the form of the microspheres prepared by liquid phase synthesis, and the contact between an electrolyte and an active substance is promoted, so that the capacity of a battery is improved, and the service life of the battery is prolonged. And the spherical secondary particles are beneficial to improving the stacking density of the material. In addition, the amorphous carbon coating layer effectively inhibits the dissolution of active substances, and meanwhile, the conductivity of the material is greatly improved; the problems of poor conductivity, rapid capacity attenuation and the like of the sodium ion battery positive electrode material are solved by regulating and controlling the doping amount of the vanadium doping element.

The invention relates to the technical field of sodium ion battery positive electrode materials, and discloses a preparation method of a high-entropy sodium vanadium phosphate electrode, which comprises the following steps: step 1, adding 2.7 g of ammonium vanadate and 16.8 g of oxalic acid into 200 mL of deionized water, and stirring to react for 20-80 minutes at the temperature of 60-120 DEG C; 2, after slight cooling, 0.75 g of ferric nitrate, 0.81 g of manganese nitrate, 0.80 g of chromic nitrate, 0.58 g of cobalt nitrate and 0.49 g of nickel nitrate which are dissolved with 100 mL of deionized water are added; and step 3, after stirring, adding 8.3 g of sodium dihydrogen phosphate which is dissolved by 100mL of deionized water. The precursor is prepared by adopting a chemical synthesis method, and the high-entropy metal doped sodium vanadium phosphate positive electrode material is prepared by adopting a Joule thermal process. Compared with a traditional calcination process, the process has the advantages of high heating speed, low energy consumption, mild reaction conditions, high product purity, good particle size uniformity, easiness in control of the proportion of each component and the like, and continuous preparation can be realized.

The invention provides a sodium vanadium fluorophosphate positive electrode material, a positive electrode plate and a sodium ion battery, and belongs to the technical field of sodium ion batteries, the sodium vanadium fluorophosphate positive electrode material comprises sodium vanadium fluorophosphate particles and nitrogen-doped carbon coating layers on the surfaces of the sodium vanadium fluorophosphate particles, the ratio of Ig to Id of the nitrogen-doped carbon coating layers in a Raman spectrum is 1-1.9, and the ratio of Ig to Id is 1-1.9. The porosity of the sodium vanadium fluorophosphate positive electrode material is 12%-33%, and the powder resistivity of the sodium vanadium fluorophosphate positive electrode material is 27000 omega.cm to 73000 omega.cm. According to the invention, the electrochemical performance, especially the cycle performance and the rate capability, of the sodium vanadium fluorophosphate positive electrode material can be improved.

The invention belongs to the technical field of synthesis of a positive electrode material of a sodium ion battery technology, and provides sodium vanadium phosphate prepared based on Joule heating as well as a preparation method and application of the sodium vanadium phosphate. The preparation method comprises the following steps: S1, uniformly mixing a vanadium source, a phosphorus source, a sodium source and a carbon source in a ball milling manner to obtain a precursor; and S2, loading the precursor in a graphite boat, and carrying out Joule heating treatment under inert gas or vacuum protection to obtain the uniform and compact carbon-coated sodium vanadium phosphate. The sodium vanadium phosphate is prepared through quick heating of Joule heat, the forming time difference of a carbon layer and a main body material can be effectively shortened, a uniform and compact carbon coating layer is obtained, and then the rate capability and the cycling stability of the sodium vanadium phosphate are improved.

The invention relates to the field of sodium ion batteries, and discloses a sodium vanadium phosphate composite positive electrode active material, a preparation method thereof and a sodium ion battery. The sodium vanadium phosphate composite positive electrode active material comprises a sodium vanadium phosphate inner core and a carbon coating layer coating at least part of the surface of the sodium vanadium phosphate inner core; and the compaction density of the sodium vanadium phosphate composite positive active material is greater than 1.8 g / cm < 3 >. When the positive electrode active material with relatively high compaction density is applied to the sodium ion battery, the diffusion path of sodium ions can be reduced, the energy density of the battery is improved, the discharge capacity of the battery is increased, the internal resistance of the battery is reduced, the polarization loss is reduced, the voltage platform of the battery is improved, and the rate capability and the cycle performance of the battery are ensured.

The invention relates to a vanadium-manganese-sodium phosphate / carbon positive electrode material and a preparation method and application thereof.The preparation method of the vanadium-manganese-sodium phosphate / carbon positive electrode material comprises the steps that a vanadium source, a phosphorus source and a manganese source are dissolved in deionized water respectively, and a vanadium source solution, a phosphorus source solution and a manganese source solution are obtained respectively; the method comprises the following steps: under the condition that the pH value is 4.00-6.00, dropwise adding a vanadium source solution and a manganese source solution into a phosphorus source solution respectively at the same time to carry out coprecipitation reaction, aging after dropwise adding, separating a solid product, and drying to obtain a vanadium manganese phosphate precursor; and mixing the vanadium manganese phosphate precursor, a carbon source, a sodium source and a reducing agent in an inert atmosphere, and carrying out solid-phase sintering reaction to obtain the vanadium manganese sodium phosphate / carbon positive electrode material. The prepared vanadium manganese sodium phosphate / carbon positive electrode material is high in purity, and has a proper vanadium and manganese ratio, excellent processing performance and good electrochemical performance.

The invention discloses a high-entropy sodium vanadium phosphate positive electrode material and a preparation method and application thereof.The material comprises a carbon layer coated on the outer layer of sodium vanadium phosphate, the chemical formula of the sodium vanadium phosphate is Na3V2-10xMn3xCo3xNi3xCr2xTi3x / 2 (PO4) 3, x is larger than or equal to 0 and smaller than or equal to 0.1, a carbon source, a vanadium source, a phosphorus source, a manganese source, a cobalt source, a nickel source, a chromium source, a titanium source and a sodium source are sequentially added into a solvent according to needs to be evenly mixed, the mixture is heated and stirred in an oil bath till the gel state is achieved, drying is conducted, and the high-entropy sodium vanadium phosphate positive electrode material is obtained. And grinding, calcining, naturally cooling to room temperature, and grinding into powder. The five elements Mn, Co, Ni, Cr and Ti are used for partially replacing V, the diffusion kinetics and conductivity of sodium ions are improved by doping and optimizing the structure of the material, the crystallinity and specific capacity of the material are improved, rapid migration of the sodium ions and conduction of electrons are promoted, the electrochemical performance is excellent, and the material is used for the sodium ion battery.

The invention belongs to the technical field of battery materials, and relates to a double-layer coated sodium vanadium phosphate positive electrode material as well as a preparation method and application thereof. The invention provides the double-layer coated sodium vanadium phosphate positive electrode material, the innovative design of the double-layer coated sodium vanadium phosphate positive electrode material remarkably improves the performance of the existing aqueous battery, and particularly provides an effective solution for the problems of short cycle life and low capacity of the traditional aqueous battery. The novel positive electrode material is composed of a sodium vanadium phosphate inner core, an aluminum oxide coating layer and a carbon coating layer, the electrochemical performance of the sodium vanadium phosphate inner core is further optimized by doping metal, so that the material not only has higher structural stability, but also can effectively improve the charge-discharge efficiency and capacity.

The invention provides a phosphate positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery, and belongs to the field of battery materials, the phosphate positive electrode material comprises an inner core and a carbon layer coating the inner core; the inner core comprises a sodium vanadium fluorophosphate material; the compaction density of the phosphate positive electrode material is not less than 1.78 g / cm < 3 >, and the BET specific surface area is not less than 9m < 2 > / g; the Raman spectrum of the phosphate positive electrode material has a peak D and a peak G, and the intensity ratio of the peak D to the peak G is (1.03-1.05): 1. According to the phosphate positive electrode material provided by the invention, the sodium vanadium fluorophosphate material with high working voltage is taken as the core, and the core is coated with the carbon layer with high crystallinity, so that the phosphate positive electrode material is endowed with better electron conductivity and structural stability, and the compaction density and BET specific surface area of the phosphate positive electrode material are also improved; therefore, the preparation of a secondary battery with high energy density is facilitated.

The application provides a preparation method of sodium vanadium fluorophosphate, which comprises the following steps: mixing a sodium source, a vanadium source, a phosphorus source and a fluorine source to form a first raw material, wherein the molar ratio of sodium element, vanadium element, phosphorus element and fluorine element in the first raw material is a:b:c:d, wherein a, b, c and d are real numbers greater than 0, and a / c≤1.5, a / b<1.5, a / d<1, or a / c≥1.5, c / b<1 and c / d<2 / 3; the first raw material is treated to obtain a first precursor; and the first precursor is dried and calcined to obtain sodium vanadium fluorophosphate. The preparation method can be used to prepare sodium vanadium fluorophosphate with few impurities, high purity and excellent performance, and is helpful to the use of sodium vanadium fluorophosphate. The application further provides a preparation method and application of carbon-coated sodium vanadium fluorophosphate.

The invention discloses a high-stability gel polymer electrolyte as well as a preparation method and application thereof, and relates to the technical field of metal batteries. The preparation method comprises the following steps: mixing a metal salt and a solvent to obtain a basic electrolyte; adding butyl acrylate, triallyl isocyanurate, a plasticizer and an initiator into the basic electrolyte to obtain a precursor solution; and carrying out polymerization reaction on the precursor solution to obtain the high-stability gel polymer electrolyte. The prepared gel polymer electrolyte has the characteristics of high ionic conductivity and high strength, and can be applied to a lithium metal battery and a sodium metal battery. The NVP gel polymer electrolyte Na metal battery assembled by adopting a polyanion positive electrode sodium vanadium phosphate (NVP), a sodium metal negative electrode and the gel polymer electrolyte disclosed by the invention can realize long cycle stability under high magnification.

The present application uses sodium source, vanadium source, reducing acid and phosphoric acid as raw materials, synthesizes Na(VO)2(PO4)2.4H2O through wet ball milling, and then obtains layered vanadium phosphate-based positive electrode material Na(VO)2(PO4)2 after low-temperature sintering of the synthesized material. The present application realizes synthesis of pure-phase layered vanadium phosphate-based positive electrode material Na(VO)2(PO4)2 at room temperature. Compared with other phosphate positive electrode materials, the material has obviously improved electrical conductivity, shows excellent discharge capacity without carbon coating, and the synthesis method has low synthesis temperature, simple operation, low cost, strong controllability, good repeatability and suitability for industrial production.

The invention discloses a preparation method of a soft-hard carbon coated sodium vanadium phosphate composite material and application of the soft-hard carbon coated sodium vanadium phosphate composite material in a sodium ion battery. The preparation method of the composite material comprises the following steps: mixing a sodium source, a vanadium source, a phosphorus source, a soft carbon source and a hard carbon source together, carrying out ball milling, and then carrying out high-temperature calcination to obtain the soft-hard carbon coated sodium vanadium phosphate composite material. The soft carbon can be used as a high-quality conducting medium for charge transfer, the hard carbon can provide defects to accelerate the sodium ion migration rate, and the electrochemical performance of the material can be improved under the synergistic effect of the soft-hard carbon. The composite material as a sodium ion battery positive electrode material has excellent electrochemical performance, and the preparation method is simple, short in process and low in cost, and has a great commercialization prospect.