A high-rate sodium iron pyrophosphate-barium titanate positive electrode material and its preparation method

Abstract

The present invention discloses a high-rate sodium iron phosphate pyrophosphate-barium titanate cathode material and its preparation method. The material comprises nano-barium titanate in-situ composited with sodium iron phosphate pyrophosphate. The sodium iron phosphate pyrophosphate has a porous structure, and the mass proportion of barium titanate in the porous sodium iron phosphate pyrophosphate is 0.5-6wt%. The present invention introduces nano-barium titanate into the porous sodium iron phosphate pyrophosphate through an in-situ composite technique, significantly improving the rate performance, cycling capacity, and ionic conductivity of the sodium iron phosphate pyrophosphate-barium titanate cathode material. The material particularly optimizes the rate performance during high-current charge and discharge, effectively supporting high-power output in a short period of time and long-term cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium batteries, and in particular relates to a high-rate sodium iron pyrophosphate-barium titanate positive electrode material and a preparation method thereof. Background Art

[0002] As a new energy storage system, sodium-ion batteries, with their significant advantages such as low cost and abundant resources, have been widely used in various fields, including renewable energy storage, electric vehicles, and grid dispatch. In particular, in high-load applications such as power load regulation and rapid response, sodium-ion batteries need to have higher rapid charge and discharge capabilities, that is, to output high power in a short period of time while maintaining high cycle stability during long-term use. Therefore, sodium ferrous pyrophosphate (NFPP) has gradually come into people's attention.

[0003] NFPP is an ionic compound containing pyrophosphate. Its unique three-dimensional framework provides stable pathways for the insertion and extraction of sodium ions. This allows for rapid sodium ion insertion and extraction while preventing structural collapse caused by volume changes during charge and discharge, effectively extending the battery's cycle life. However, with the increasing application of batteries in everyday life, higher demands have been placed on the rate performance and cycling capacity of NFPP. To optimize these performances, researchers have begun to incorporate other highly conductive materials into NFPP, such as doping with titanium, aluminum, manganese, nitrogen, and sulfur, or compounding NFPP with materials such as carbon nanotubes and graphene. While these modifications have further enhanced NFPP's rate performance, the rapid migration of ions and electrons during short, high-load conditions can still cause structural changes in the electrode material, impacting cycle life. Furthermore, coating or encapsulating NFPP to optimize its cycling performance can inhibit the battery's rate performance, particularly during high-current charge and discharge.

[0004] Therefore, how to further improve the structural stability of NFPP and optimize its cycle performance while optimizing the rate performance of NFPP, especially the stability and rate during high current charging and discharging, has become a major difficulty in current research. Summary of the Invention

[0005] The present invention addresses the problems in the prior art and provides a high-rate sodium iron pyrophosphate-barium titanate positive electrode material, which effectively optimizes the NFPP cycle performance and rate performance while maintaining the high stability of sodium iron pyrophosphate, especially the rate performance during high current charge and discharge.

[0006] In the first aspect, the present invention provides a high-rate sodium iron phosphate pyrophosphate-barium titanate positive electrode material, including nano-barium titanate in-situ composited with sodium iron phosphate pyrophosphate, the sodium iron phosphate pyrophosphate has a porous structure, and the mass proportion of the barium titanate in the porous sodium iron phosphate pyrophosphate is 0.5-6wt%.

[0007] As a further solution, the sodium ferric phosphate pyrophosphate has the general formula Na x Fe y (PO4) z P2O7, where 2.8≤x≤4.2, 1.8≤y≤3.2, and 0.8≤z≤2.2.

[0008] As some preferred examples, in the sodium ferric pyrophosphate, 2.8≤x≤3.5, 1.8≤y≤2.5, and 0.8≤z≤1.5.

[0009] As a further solution, the sodium iron pyrophosphate-barium titanate positive electrode material has a micron-scale and nano-scale secondary pore structure, wherein the micron-scale pore size range is less than 2 μm, and the nano-scale pore structure size range is selected from 10 nm to 60 nm.

[0010] As a further preferred solution, the micron-scale pores have a pore size range of less than 1.5 μm, and the nanoscale pore structure has a pore size range selected from 25 nm to 50 nm.

[0011] As a further solution, the reversible specific capacity of the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 89.1-92 mAh / g.

[0012] As a further solution, the sodium iron pyrophosphate-barium titanate positive electrode material has a 350-week 1C cycle retention rate greater than 95%.

[0013] As a further solution, the sodium iron pyrophosphate-barium titanate positive electrode material has a rate specific capacity greater than 65 mAh / g at 60C.

[0014] Preferably, the sodium iron pyrophosphate-barium titanate positive electrode material has a first 60C / 1C rate capacity percentage greater than 70%.

[0015] Preferably, the sodium iron pyrophosphate-barium titanate positive electrode material has a first 60C / 1C rate capacity percentage greater than 73%.

[0016] In a second aspect, this solution provides a method for preparing a sodium iron pyrophosphate-barium titanate positive electrode material, comprising the following steps:

[0017] S1: Dispersing nano-barium titanate into a solvent containing a chelating agent according to the product stoichiometric ratio, and adding an iron source to obtain solution A;

[0018] S2: dissolving a sodium source and a phosphorus source in a solvent according to the product stoichiometric ratio to obtain a solution B, mixing solutions A and B, evaporating the solvent, and drying to obtain a sodium iron pyrophosphate-barium titanate cathode material precursor;

[0019] S3: calcining the sodium iron phosphate pyrophosphate-barium titanate positive electrode material precursor to obtain the sodium iron phosphate pyrophosphate-barium titanate positive electrode material.

[0020] As a further solution, the mass proportion of the barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 0.5wt% to 6wt%.

[0021] As some preferred solutions, the mass proportion of the barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 2wt% to 4wt%.

[0022] As a further solution, the particle size of the barium titanate is selected from 50 nm to 150 nm.

[0023] As some preferred solutions, the particle size of the barium titanate is selected from 80nm to 120nm.

[0024] As a further embodiment, the molar ratio of the iron source to the chelating agent is selected from (0.5-3.5):1.

[0025] As some preferred solutions, the molar ratio of the iron source to the chelating agent is selected from (1.5-2.5):1.

[0026] As a further solution, the concentration of the iron source in the solvent is selected from 0.1-0.2 mol / L.

[0027] As a further solution, the iron source is selected from any one or more of ferric salts and ferrous salts.

[0028] As a further embodiment, the chelating agent is selected from any one or more of polyhydroxy aldehydes, polyhydroxy acids, and dicarboxylic acids.

[0029] As a further solution, in steps S1 and S2, the solvent is selected from any one of deionized water and alcohol solvents.

[0030] As a further solution, the sodium source is selected from any one of an inorganic sodium salt and an organic sodium salt.

[0031] As a further embodiment, the phosphorus source is selected from phosphates, phosphoric acid and phosphorus oxides.

[0032] As a further solution, in step S2, when mixing solution A and solution B, the mixing method is not limited in principle, and technicians can choose any method such as stirring, ultrasound, etc. to mix solution A and solution B.

[0033] As a further solution, when solution A and solution B are mixed by stirring, the stirring time is selected from 40-60 min, and the stirring speed is selected from 500 r / min-800 r / min.

[0034] As a further solution, in step S2, the temperature for evaporating the solvent is selected from 70°C to 90°C.

[0035] As a further solution, in step S2, the drying temperature is selected from 80°C-120°C.

[0036] As a further solution, in step S2, the drying time is selected from 6h-10h.

[0037] As a further solution, in step S3, before calcining the sodium iron pyrophosphate-barium titanate positive electrode material precursor, the sodium iron pyrophosphate-barium titanate positive electrode material precursor is first ground into powder.

[0038] As a further solution, in step S3, the calcination of the sodium iron pyrophosphate-barium titanate positive electrode material precursor is carried out in an inert atmosphere.

[0039] As a further solution, the inert atmosphere is selected from any one of helium, neon, argon and nitrogen.

[0040] As a further solution, the inert atmosphere is preferably argon or nitrogen.

[0041] As a further solution, when calcining in step S3, the sintered steel is first pre-sintered at 300-380°C for 1-6 hours, and then naturally cooled and then calcined at 500-700°C for 5-12 hours.

[0042] As some preferred solutions, when calcining in step S3, the steel is first pre-sintered at 330-360°C for 3-6 hours, and then naturally cooled and then calcined at 500-600°C for 8-12 hours.

[0043] As a further solution, the heating rate during calcination is selected from 5 to 10°C / min.

[0044] In a third aspect, the present invention provides a battery using sodium iron pyrophosphate-barium titanate positive electrode material as the positive electrode active material.

[0045] As a further solution, the battery includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0046] As a further solution, the positive electrode sheet includes a positive electrode current collector, a positive electrode conductor, and a positive electrode adhesive.

[0047] As a further embodiment, the positive electrode current collector is selected from copper, aluminum, titanium, nickel, zirconium, zinc, tungsten, bismuth, antimony, iron, chromium, tin and alloys containing one or more of these, and one or more metals selected from alloys can be mentioned.

[0048] As a further solution, the positive electrode conductive agent is selected from any one or more of carbon materials, metal materials, and conductive polymers.

[0049] As a further solution, the positive electrode binder is selected from at least one of thermoplastic resin, acrylic resin, sodium carboxymethyl cellulose and styrene butadiene rubber.

[0050] As a further solution, the negative electrode plate can directly adopt a sodium plate or a plate including a negative electrode active material, a negative electrode current collector, a negative electrode conductive agent, and a negative electrode adhesive.

[0051] As a further embodiment, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon beads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 , one or more of Li-Al alloys

[0052] As a further solution, the negative electrode current collector is not limited in principle, and for example, any one of aluminum, nickel, tin, copper and stainless steel can be selected.

[0053] As a further solution, the negative electrode conductive agent is selected from carbon materials.

[0054] As a further solution, the negative electrode binder is selected from any one or more of polymers, rubbers, cellulose derivatives, and resins.

[0055] As a further solution, the diaphragm is not limited, and technicians can select any one of glass fiber diaphragms, polyimide (PI) diaphragms, polyetheretherketone (PEEK) diaphragms, polyethylene terephthalate (PET) diaphragms, and non-woven fabric diaphragms according to their needs.

[0056] As a further solution, the battery may further include a solid electrolyte or an electrolyte. The solid electrolyte or the electrolyte is not limited, and technicians can select the corresponding electrolyte or solid electrolyte according to needs.

[0057] Fourthly, this solution also provides an electrochemical device, comprising the high-rate sodium iron pyrophosphate-barium titanate cathode material proposed in this solution as the positive electrode active material. The electrochemical device refers to a device that utilizes electrochemical reactions to transform matter and energy, including but not limited to primary cells, electrolytic cells, electrochemical workstations, and electrochemical reactors.

[0058] Fifthly, this solution also proposes an energy storage device composed of a plurality of batteries or electrochemical devices for storing and releasing electrical energy.

[0059] In a sixth aspect, this solution also provides an electrical device comprising the high-rate sodium iron pyrophosphate-barium titanate cathode material proposed in this solution as the positive electrode active material. The electrical device refers to any device and system that requires electricity to operate, including any one or more energy storage devices, batteries, and electrochemical devices.

[0060] Compared with the prior art, the present invention has at least the following beneficial effects:

[0061] The present invention introduces nano-scale barium titanate particles into porous sodium iron phosphate pyrophosphate through in-situ composite technology, significantly improving the overall performance of the sodium iron phosphate pyrophosphate-barium titanate positive electrode material. In the sodium iron phosphate pyrophosphate-barium titanate positive electrode material, the unique spontaneous polarization characteristics of nano-barium titanate form a built-in electric field, which promotes the rapid diffusion of Na⁺ and optimizes the rate performance, allowing the material to maintain a high capacity under high current charge and discharge conditions. At the same time, the piezoelectrically induced polarization electric field of barium titanate accelerates the desolvation process, improves the ionic conductivity, and promotes the formation of a thin, uniform, stable and inorganic-rich CEI interface film during the charge and discharge process, optimizes the interface diffusion kinetics, and significantly enhances the battery's cycle stability. With these advantages, the sodium iron pyrophosphate-barium titanate positive electrode material exhibits excellent rate performance and cycle stability, providing important material support for the research and development of high-performance sodium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0063] Figure 1 a is the XRD pattern of Example 1, and b is the XRD pattern of Comparative Example 1;

[0064] Figure 2 This is a SEM image of barium titanate used as a raw material in Example 1;

[0065] Figure 3 a is the SEM image of Comparative Example 1, and b is the SEM image of Example 1;

[0066] Figure 4 a is the FIB image of Comparative Example 1, and b is the FIB image of Example 1;

[0067] Figure 5 This is the line scan result of the sodium iron pyrophosphate-barium titanate positive electrode material prepared in Example 1;

[0068] Figure 6 The first charge and discharge diagrams of Example 1 and Comparative Example 1 at 0.1C are shown;

[0069] Figure 7 1 is a rate performance diagram of Example 1 and Comparative Example 1;

[0070] Figure 8 1 is a cycle diagram of Example 1 and Comparative Example 1;

[0071] Figure 9 In the figure, Figure a is a TEM image of Example 1 after cycling, and Figure b is a TEM image of Comparative Example 1 after cycling, wherein the area selected by the white dotted line is the CEI film formed after cycling;

[0072] Figure 10 In the figure, Figure a is the XPS graph of Comparative Example 1 before and after the cycle, and Figure b is the XPS graph of Example 1 before and after the cycle;

[0073] Figure 11 This is the BET result of Example 1. DETAILED DESCRIPTION

[0074] For ease of understanding, the present invention will be described in more detail below, and examples of the present invention are given, but the scope of the present invention is not limited thereby.

[0075] The following is a description of terms or words, and unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0076] As used herein, the term "polyhydroxy aldehyde" refers to a class of organic compounds containing at least two hydroxyl groups (-OH) and one aldehyde group (-CHO).

[0077] As used herein, the term "polyhydroxy acid" refers to an organic acid containing at least two hydroxyl (-OH) groups.

[0078] As used herein, the term "dicarboxylic acid" refers to a class of organic compounds containing two carboxyl (-COOH) functional groups.

[0079] In the first aspect, the present invention provides a high-rate sodium iron phosphate pyrophosphate-barium titanate positive electrode material, including nano-barium titanate in-situ composited with sodium iron phosphate pyrophosphate, the sodium iron phosphate pyrophosphate has a porous structure, and the mass proportion of the barium titanate in the porous sodium iron phosphate pyrophosphate is 0.5-6wt%.

[0080] In order to further optimize the rate performance of NFPP, improve the cycle capacity of NFPP, and achieve rapid charge and discharge of the battery, this scheme introduces barium titanate into NFPP; barium titanate is a typical ferroelectric material with significant spontaneous polarization characteristics, that is, in the absence of an external electric field, titanium ions will spontaneously deviate from the center position of the oxygen octahedron, thereby forming a polarization phenomenon. Compared with other ferroelectric materials, barium titanate has a better dielectric constant, piezoelectric effect, and strong chemical and thermal stability. It can provide unique advantages in optimizing rate performance, improving cycle capacity, promoting the contact between electrode active materials and electrolytes, and increasing the stability of material structures. Therefore, in this scheme, we will use in-situ composite technology to introduce nanometer-sized barium titanate particles into porous sodium iron pyrophosphate. Nanometer-sized barium titanate particles can use the built-in electric field brought by the polarization effect to form a polarization field for Na + Diffusion provides the driving force, thereby accelerating the Na + migration and improve the rate performance; at the same time, the piezoelectrically induced polarization electric field constructed by barium titanate can also effectively accelerate the desolvation process, thereby further improving the ionic conductivity, and in the process of sodium storage, it can help to build a thin, uniform, stable and inorganic-rich CEI interface film, thereby improving the interface diffusion kinetics of the material and optimizing the battery cycle performance; in addition, in this scheme, the mass proportion of barium titanate in the porous sodium iron phosphate pyrophosphate is set to 0.5-6wt%. By controlling the mass proportion of barium titanate in the porous sodium iron phosphate pyrophosphate, it is helpful to fully exert the self-polarization effect of barium titanate while protecting the porous sodium iron phosphate pyrophosphate structure, and at the same time cooperate with the barium titanate particle size to optimize the pore size of the porous sodium iron phosphate pyrophosphate, thereby promoting full contact between the electrode active material and the electrolyte; under the interaction between porous sodium iron phosphate pyrophosphate and barium titanate, the porous sodium iron phosphate pyrophosphate-barium titanate material obtained in this scheme exhibits excellent rate performance and cycle ability, and significantly improves the rate capacity during high current charge and discharge.

[0081] As some examples, the general formula of the sodium ferric phosphate pyrophosphate is Na x Fe y (PO4) z P2O7, where 2.8≤x≤4.2, 1.8≤y≤3.2, 0.8≤z≤2.2.

[0082] As some preferred examples, in the sodium ferric pyrophosphate, 2.8≤x≤3.5, 1.8≤y≤2.5, and 0.8≤z≤1.5.

[0083] As some examples, Figure 3 b. Figure 4 b. The sodium iron phosphate pyrophosphate-barium titanate cathode material has a micron-scale and nano-scale secondary pore structure, wherein the micron-scale pore size range is less than 2μm, and the nano-scale pore size range is selected from 10 nm to 60 nm. This secondary pore structure, on the one hand, provides a more efficient channel for the contact between the electrode active material and the electrolyte, while promoting the contact between the electrolyte and the electrode material, thereby accelerating the diffusion process of sodium ions in the material and improving the charge and discharge rate and capacity of the battery. On the other hand, it also helps to coordinate the particle size and content of barium titanate, optimize the polarization electric field of barium titanate, and efficiently drive the solvent molecules to detach from the ion surface, thereby achieving desolvation.

[0084] As some preferred examples, the micron-scale pore size range is less than 1.5 μm, and the nanoscale pore size range is selected from 25 nm to 50 nm ( Figure 11 ).

[0085] As some examples, the reversible specific capacity of the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 89.1-92 mAh / g.

[0086] As some examples, the sodium iron pyrophosphate-barium titanate positive electrode material has a 350-week 1C cycle retention rate greater than 95%.

[0087] As some examples, the sodium iron pyrophosphate-barium titanate positive electrode material has a rate specific capacity greater than 65 mAh / g at 60C.

[0088] Preferably, the sodium iron pyrophosphate-barium titanate positive electrode material has a first 60C / 1C rate capacity percentage greater than 70%;

[0089] Preferably, the sodium iron pyrophosphate-barium titanate positive electrode material has a first 60C / 1C rate capacity percentage greater than 73%.

[0090] In a second aspect, this solution provides a method for preparing a sodium iron pyrophosphate-barium titanate positive electrode material, comprising the following steps:

[0091] S1: Dispersing nano-barium titanate into a solvent containing a chelating agent according to the product stoichiometric ratio, and adding an iron source to obtain solution A;

[0092] S2: dissolving a sodium source and a phosphorus source in a solvent according to the product stoichiometric ratio to obtain a solution B, mixing solutions A and B, evaporating the solvent, and drying to obtain a sodium iron pyrophosphate-barium titanate cathode material precursor;

[0093] S3: calcining the sodium iron phosphate pyrophosphate-barium titanate positive electrode material precursor to obtain the sodium iron phosphate pyrophosphate-barium titanate positive electrode material.

[0094] As some examples, the mass proportion of the barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 0.5wt% to 6wt%. Such a range helps to protect the porous sodium iron pyrophosphate structure while fully exerting the effect of barium titanate, thereby improving the reversible specific capacity of the sodium iron pyrophosphate-barium titanate positive electrode material and the charge and discharge performance under high voltage, while optimizing the cycle performance of the sodium iron pyrophosphate-barium titanate positive electrode material.

[0095] As some preferred examples, the mass proportion of the barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 2wt% to 4wt%. We believe that a barium titanate content of 2wt% to 4wt% helps to better optimize the barium titanate effect and the structure of the sodium iron pyrophosphate-barium titanate positive electrode material, thereby improving the overall performance of the sodium iron pyrophosphate-barium titanate positive electrode material.

[0096] As some examples, the barium titanate particle size is selected from 50nm to 150nm. On the one hand, the polarization properties of barium titanate (including spontaneous polarization and piezoelectric effect) depend on its crystal structure, especially the position of the titanium ion away from the center of the oxygen octahedron. When the barium titanate particle size is selected from 50nm to 150nm, it helps to better exert the polarization effect of barium titanate, thereby optimizing the overall performance of the sodium iron pyrophosphate-barium titanate positive electrode material. On the other hand, when the barium titanate particle size is selected from 50nm to 150nm, it also helps to match the pores on the porous sodium iron pyrophosphate, further optimizing the overall performance of the sodium iron pyrophosphate-barium titanate positive electrode material.

[0097] As some preferred examples, the particle size of barium titanate is selected from 80nm to 120nm, which not only helps barium titanate to obtain more interfaces and higher surface energy, but also strengthens the polarization effect of barium titanate and promotes Na + It can not only improve the migration of the material, but also coordinate with the barium titanate content to optimize the pore structure and promote the full contact between the electrode and the electrolyte, thereby improving the ion migration speed, electrical conductivity and rate performance of the battery.

[0098] As some examples, the molar ratio of the iron source to the chelating agent is selected from (0.5-3.5):1.

[0099] As some preferred examples, the molar ratio of the iron source to the chelating agent is selected from (1.5-2.5):1.

[0100] As some examples, the concentration of the iron source in the solvent is selected from 0.1-0.2 mol / L.

[0101] As some examples, the iron source is selected from any one or more of ferric salts and ferrous salts.

[0102] As some examples, the ferric salt includes but is not limited to any one or more of ferric sulfate, ferric chloride, and ferric nitrate.

[0103] As some examples, the ferrous salt is selected from any one or more of ferrous oxalate, ferrous acetylacetonate, ferrous citrate, and ferrous sulfate.

[0104] On the one hand, the presence of the chelating agent can complex transition metal ions with barium titanate to form a complex, thereby improving the uniformity of the material while avoiding the introduction of impurity ions. On the other hand, during the subsequent calcination process, the chelating agent pyrolyzes and produces gas at high temperature, which not only achieves the immobilization of barium titanate, but also gives the sodium iron pyrophosphate-barium titanate positive electrode material a unique secondary pore structure. This structure with both micron-scale pores and nano-scale pores helps to provide different diffusion channels for ions, thereby more efficiently completing the ion transfer during the battery charging and discharging process, promoting the contact between the electrolyte and the electrode material, and improving the interface reaction.

[0105] Therefore, as some examples, the chelating agent is selected from any one or more of polyhydroxy aldehydes, polyhydroxy acids, and dicarboxylic acids.

[0106] As some examples, the polyhydroxy aldehyde is selected from any one or more of glyceraldehyde, glucose, and mannose.

[0107] As some examples, the polyhydroxy acid is selected from any one or more of ascorbic acid, citric acid, and methanetricarboxylic acid.

[0108] As some examples, the dicarboxylic acid is selected from any one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid.

[0109] As some examples, in the process of synthesizing sodium iron pyrophosphate-barium titanate positive electrode materials, different iron sources, sodium sources, and phosphorus sources have different solubility characteristics. In steps S1 and S2, the choice of solvent depends on whether the iron source, sodium source, and phosphorus source are soluble in water or in an alcohol solvent. Therefore, in steps S1 and S2, the solvent is selected from either deionized water or an alcohol solvent.

[0110] As some preferred examples, the solvents in steps S1 and S2 are preferably different solvents. Selecting different types of solvents in steps S1 and S2 helps to match the solubility characteristics of the iron source, sodium source and phosphorus source, so that they are better dissolved in the solvent, laying the foundation for subsequent experiments. On the other hand, by selecting different solvents for distributed dissolution and mixing, the microstructure of the material can be better controlled, thereby constructing a more uniform and stable sodium iron pyrophosphate-barium titanate positive electrode material.

[0111] As some examples, the alcohol solvent includes but is not limited to any one of ethanol, methanol, propanol, and isopropanol.

[0112] As some examples, the sodium source is selected from any one of an inorganic sodium salt and an organic sodium salt.

[0113] As some examples, the inorganic sodium salt is not limited in principle, and includes but is not limited to any one or more of sodium hydroxide, sodium chloride, sodium sulfate, sodium carbonate, sodium bicarbonate, sodium nitrate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium dihydrogen phosphate dihydrate.

[0114] As some examples, the organic sodium salt includes but is not limited to any one or more of sodium acetate, sodium citrate, and sodium carboxymethyl cellulose.

[0115] As some examples, the phosphorus source is selected from phosphates, phosphoric acid, and phosphorus oxides.

[0116] As some examples, the phosphate includes but is not limited to any one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate dihydrate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and sodium pyrophosphate.

[0117] As some examples, the phosphorus oxides include but are not limited to any one or more of phosphorus pentoxide and phosphorus trioxide.

[0118] As some preferred examples, the phosphorus source and sodium source are preferably substances containing both phosphorus and sodium elements, including but not limited to any one or more of sodium dihydrogen phosphate dihydrate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

[0119] As some examples, in step S2, when mixing solution A and solution B, the mixing method is not limited in principle, and technicians can choose any method such as stirring, ultrasound, etc. to mix solution A and solution B.

[0120] As some examples, when solution A and solution B are mixed by stirring, the stirring time is selected from 40-60 min, and the stirring speed is selected from 500 r / min-800 r / min.

[0121] As some examples, in step S2, the temperature for evaporating the solvent is selected from 70°C to 90°C.

[0122] As some examples, in step S2, the drying temperature is selected from 80°C-120°C.

[0123] As some examples, in step S2, the drying time is selected from 6 hours to 10 hours.

[0124] As some examples, in step S3, before calcining the sodium iron pyrophosphate-barium titanate positive electrode material precursor, the sodium iron pyrophosphate-barium titanate positive electrode material precursor is first ground into powder.

[0125] As some examples, in step S3, calcining the sodium iron pyrophosphate-barium titanate positive electrode material precursor is performed in an inert atmosphere.

[0126] As some examples, the inert atmosphere is selected from any one of helium, neon, argon, and nitrogen.

[0127] As some examples, the inert atmosphere is preferably argon or nitrogen.

[0128] As some examples, when calcining in step S3, the pre-sintering is first performed at 300° C.-380° C. for 1-6 hours, and then the calcination is continued at 500-700° C. for 5-12 hours after natural cooling.

[0129] As some preferred examples, when calcining in step S3, the steel is first pre-sintered at 330-360°C for 3-6 hours, and then naturally cooled and then calcined at 500-600°C for 8-12 hours.

[0130] As some examples, the heating rate during calcination is selected from 5 to 10° C. / min.

[0131] In a third aspect, the present invention provides a battery using sodium iron pyrophosphate-barium titanate positive electrode material as the positive electrode active material.

[0132] As some examples, the battery includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0133] As some examples, the positive electrode sheet includes a positive electrode current collector, a positive electrode conductor, and a positive electrode adhesive.

[0134] As some examples, the positive electrode current collector is selected from copper, aluminum, titanium, nickel, zirconium, zinc, tungsten, bismuth, antimony, iron, chromium, tin, alloys containing one or more of these, and one or more metals selected from alloys can be mentioned.

[0135] As some examples, the positive electrode conductive agent is selected from any one or more of carbon materials, metal materials, and conductive polymers.

[0136] As some examples, the carbon material is selected from any one or more of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber.

[0137] As some examples, the metal material is selected from any one or more of copper, nickel, aluminum, and silver.

[0138] As some examples, the conductive polymer is selected from one or more of polyfluorene (PF), polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh), polyethylene dioxythiophene (PEDOT), polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS), and polyacetylene (PA).

[0139] As some examples, the positive electrode binder is selected from at least one of thermoplastic resin, acrylic resin, sodium carboxymethyl cellulose and styrene butadiene rubber.

[0140] As a further embodiment, the thermoplastic resin includes at least one of polyvinylidene fluoride, polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, thermoplastic polyimide, polyethylene and polypropylene.

[0141] As some examples, the negative electrode plate may be a sodium plate or a plate including a negative electrode active material, a negative electrode current collector, a negative electrode conductive agent, and a negative electrode binder.

[0142] As some examples, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon beads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 , one or more of Li-Al alloys.

[0143] As some examples, the negative electrode current collector is not limited in principle, and for example, any one of aluminum, nickel, tin, copper and stainless steel can be selected.

[0144] As some examples, the negative electrode conductive agent is selected from carbon materials.

[0145] As some examples, the carbon material used as the negative electrode conductive agent is selected from any one or more of carbon black, Super P, activated carbon, graphite, graphene, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon fibers, conductive carbon black, carbon nanospheres, ellipsoidal carbon, hard carbon, amorphous carbon, and silicon carbide.

[0146] As some examples, the negative electrode binder is selected from any one or more of polymers, rubbers, cellulose derivatives, and resins.

[0147] As some examples, the polymer is selected from any one or more of polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, polyvinylidene 1,1-difluoride, polyvinyl pyrrolidone, polyethylene, polypropylene, polyimide, polyacrylic acid, polyvinyl chloride, polytetrafluoroethylene, and polyvinylidene fluoride.

[0148] As some examples, the rubber is selected from any one or more of styrene-butadiene rubber, EPDM rubber, and fluororubber.

[0149] As some examples, the cellulose derivatives are selected from any one or more of carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose.

[0150] As some examples, the resin is selected from any one or more of epoxy resin and styrene.

[0151] As some examples, the diaphragm is not limited, and technicians can select any one of glass fiber diaphragm, polyimide (PI) diaphragm, polyetheretherketone (PEEK) diaphragm, polyethylene terephthalate (PET) diaphragm, and non-woven fabric diaphragm according to needs.

[0152] As some examples, the battery may further include a solid electrolyte or an electrolyte. The solid electrolyte or the electrolyte is not limited, and technicians may select the corresponding electrolyte or solid electrolyte according to needs.

[0153] Fourthly, this solution also provides an electrochemical device, comprising the high-rate sodium iron pyrophosphate-barium titanate cathode material proposed in this solution as the positive electrode active material. The electrochemical device refers to a device that utilizes electrochemical reactions to transform matter and energy, including but not limited to primary cells, electrolytic cells, electrochemical workstations, and electrochemical reactors.

[0154] Fifthly, this solution also proposes an energy storage device composed of a plurality of batteries or electrochemical devices for storing and releasing electrical energy.

[0155] In a sixth aspect, this solution also provides an electrical device comprising the high-rate sodium iron pyrophosphate-barium titanate cathode material proposed in this solution as the positive electrode active material. The electrical device refers to any device and system that requires electricity to operate, including any one or more energy storage devices, batteries, and electrochemical devices.

[0156] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application and do not represent all possible embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0157] The chemical raw materials involved in the following examples and comparative examples are all prior art and are commercially available. The experimental devices, test devices, etc. involved in the following examples and comparative examples are all conventional devices in the art and are not particularly limited.

[0158] Example 1

[0159] S1: According to the stoichiometric ratio, barium titanate is dispersed in 100g of an ethanol solution containing citric acid, and then 0.012mol of ferric acetylacetonate is dissolved in the above ethanol solution to obtain solution A, wherein the amount of citric acid added is 0.006mol, and the average particle size of barium titanate is selected from 100nm (such as Figure 2 shown);

[0160] S2: Using sodium dihydrogen phosphate as a sodium source and a phosphorus source, 0.018 mol of sodium dihydrogen phosphate was dissolved in 100 g of deionized water to obtain solution B; solution A and solution B were mixed at a speed of 750 r / min, stirred for 50 min, and then the solvent was evaporated at 80°C. Subsequently, the mixture was kept at 90°C in a drying oven for 8 h to obtain a sodium iron pyrophosphate-barium titanate cathode material precursor;

[0161] S3: The sodium iron pyrophosphate-barium titanate positive electrode material precursor is ground into powder, and then heated to 350°C at a rate of 5°C / min under an argon atmosphere, maintained for 5 hours, and then naturally cooled to room temperature, and then heated to 550°C at the same rate, calcined for 10 hours, and cooled to obtain the sodium iron pyrophosphate-barium titanate positive electrode material, wherein the molecular formula of sodium iron pyrophosphate is Na3Fe2(PO4)P2O7, and the mass content of barium titanate is 3%.

[0162] Example 2

[0163] The synthesis conditions and preparation steps are the same as those in Example 1, except that barium titanate with a particle size of 50 nm is used instead of barium titanate with a particle size of 100 nm.

[0164] Example 3

[0165] The synthesis conditions and preparation steps are the same as those in Example 1, except that barium titanate with a particle size of 150 nm is used instead of barium titanate with a particle size of 100 nm.

[0166] Example 4

[0167] The synthesis conditions and preparation steps are the same as those in Example 1, except that, in the sodium iron pyrophosphate-barium titanate positive electrode material theoretically generated according to the stoichiometric ratio, the mass proportion of barium titanate is 1 wt %.

[0168] Example 5

[0169] The synthesis conditions and preparation steps are the same as those in Example 1, except that, in the sodium iron pyrophosphate-barium titanate positive electrode material theoretically generated according to the stoichiometric ratio, the mass proportion of barium titanate is 5 wt %.

[0170] Example 6

[0171] The synthesis conditions and preparation steps were the same as those in Example 1, except that the amount of citric acid used was 0.012 mol.

[0172] Example 7

[0173] The synthesis conditions and preparation steps were the same as those in Example 1, except that the amount of citric acid used was 0.018 mol.

[0174] Comparative Example 1

[0175] The synthesis conditions and preparation steps are the same as those in Example 1, except that barium titanate is not added.

[0176] Comparative Example 2

[0177] The synthesis conditions and preparation steps are the same as those in Example 1, except that titanium dioxide is used instead of barium titanate.

[0178] Comparative Example 3

[0179] The synthesis conditions and preparation steps are the same as those in Example 1, except that barium carbonate is used instead of barium titanate.

[0180] Comparative Example 4

[0181] The synthesis conditions and preparation steps are the same as those in Example 1, except that barium titanate and Na3Fe2(PO4)P2O7 are dissolved in ethanol, mixed and stirred for 3 hours, and then heated to 350°C at a rate of 5°C / min under an argon atmosphere. After maintaining for 5 hours, the mixture is naturally cooled to room temperature, and then heated to 550°C at the same rate and calcined for 10 hours. After natural cooling, a directly mixed and calcined barium titanate-sodium iron phosphate pyrophosphate material is obtained.

[0182] Comparative Example 5

[0183] The synthesis conditions and preparation steps are the same as those in Example 1, except that the proportion of barium titanate in the total mass of sodium dihydrogen phosphate, ferric acetylacetonate and barium titanate is 10 wt %.

[0184] Test Method

[0185] A positive electrode slurry was prepared by mixing sodium iron pyrophosphate-barium titanate positive electrode material: Super P: polyvinylidene fluoride = 7:2:1, and coated on aluminum foil to prepare a positive electrode. The diaphragm was a glass fiber diaphragm, and the negative electrode was a sodium sheet. A CR2032 button half-cell was prepared under the condition that the water and oxygen values in the glove box were less than 0.01. The test was carried out on a Xinwei electrochemical tester. The voltage test range was 1.5-4.3V, the cycle performance test was carried out at a constant current of 1C for 350 weeks, and the rate performance test was carried out at current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 20C, 30C, 50C, and 60C for 5 cycles respectively. The first week 1C reversible specific capacity, 350-week 1C cycle retention rate, 5-week 60C rate capacity, and first week 60C / 1C rate specific capacity of the embodiment and comparative example were measured.

[0186] Among them, the 60C / 1C rate capacity percentage = (60C rate performance test first week reversible capacity / 1C rate performance test first week reversible capacity) * 100%.

[0187] The test results are shown in Table 1.

[0188] Table 1

[0189]

[0190] It can be observed from Table 1 that at 60C, Examples 1-7 exhibited better reversible specific capacity, 1C cycle retention rate, and rate capacity at 60C than Comparative Examples 1-5, indicating that the sodium iron pyrophosphate-barium titanate positive electrode material proposed in this scheme can effectively utilize the polarization effect of barium titanate to form Na + Diffusion provides the driving force, while improving ionic conductivity and optimizing the battery's cycling performance.

[0191] First, by Figure 1 It can be observed that sodium iron pyrophosphate and sodium iron pyrophosphate-barium titanate cathode materials were successfully synthesized. Figure 5 The presence of titanium and barium can be clearly observed; and both Comparative Example 1 and Example 1 exhibit porous characteristics ( Figure 3 、 Figure 4 ), the comparison results of the first efficiency, rate and cycle performance of Example 1 and Comparative Example 1 are shown in Figures 6, 7, Figure 8 Secondly, from Example 1 and Comparative Example 1 in Table 1, it can be observed that when barium titanate is not added, the reversible specific capacity and 1C cycle retention rate of Comparative Example 1 are different from those of Example 1. When high current charge and discharge (60C) is performed, its rate capacity is only 57.92mAh / g, which is much lower than 70.21mAh / g of Example 1. This may be because the introduction of barium titanate can effectively cooperate with sodium iron pyrophosphate, and the polarization effect is used to enhance the Na+ While migrating power, a more stable CEI interface film is constructed (such as Figure 9 a), while when barium titanate is lacking, comparative example 1 lacks Na + migration dynamics, and it is difficult to construct a stable CEI membrane ( Figure 9 b), and by Figure 10 It can be observed that compared with Example 1, the content of Na-F bonds in Comparative Example 1 after cycling is significantly lower, so Comparative Example 1 exhibits lower comprehensive performance than Example 1.

[0192] In order to further determine the role of barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material, we used titanium dioxide, which is also a ferroelectric material, and barium carbonate, which also contains barium elements, to replace barium titanate (Comparative Examples 2 and 3). It can be observed that Comparative Examples 2-3 exhibit lower comprehensive performance than Example 1. This may be because compared with titanium dioxide and barium titanate, the unique structure of barium titanate can give it better polarization and better compounding with porous sodium iron pyrophosphate. When titanium dioxide and barium titanate are used to replace barium titanate, even if they are both ferroelectric materials or similar elements are present, similar effects cannot be achieved. Therefore, the performance of Comparative Examples 2-3 is lower than that of Example 1.

[0193] In Comparative Example 4, we mixed barium titanate with porous sodium iron phosphate pyrophosphate and calcined it. It can be observed that when the method proposed in this scheme is not used to prepare the sodium iron phosphate pyrophosphate-barium titanate positive electrode material, Comparative Example 4 is also unable to obtain an effect similar to that of Example 1. This may be because the method proposed in this scheme can achieve in-situ compounding of porous sodium iron phosphate pyrophosphate and barium titanate, and the barium titanate only stays on the surface of the porous sodium iron phosphate pyrophosphate, which affects the performance of Comparative Example 4.

[0194] In Example 1 and Comparative Example 5, we discussed the effect of barium titanate content on the sodium iron pyrophosphate-barium titanate positive electrode material. It can be observed that when the mass content of barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is 10 wt%, the reversible specific capacity, 1C cycle retention rate and rate capacity at 60C of Comparative Example 5 are greatly affected. This may be because when the mass content of barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material exceeds 6%, excessive barium titanate may affect the structure of the sodium iron pyrophosphate-barium titanate positive electrode material, thereby affecting the comprehensive performance of the sodium iron pyrophosphate-barium titanate positive electrode material, especially the cycle performance. Therefore, Comparative Example 5 shows a result far lower than that of Example 1.

[0195] In this study, we discussed the effect of particle size on the sodium iron pyrophosphate-barium titanate cathode material. It can be observed from Examples 1-3 that Example 1 exhibits better reversible specific capacity, 1C cycle retention rate, and rate capacity at 60C than Examples 2-3. This may be because when the barium titanate particle size is selected from 80nm to 120nm, on the one hand, the polarization efficiency of barium titanate can be fully utilized, which is better than that of Na + This provides a stronger driving force for the migration of active materials. Furthermore, the pore size of the porous sodium iron pyrophosphate can be optimized by adjusting the barium titanate content. The optimized pore structure, in turn, optimizes the barium titanate polarization field, promoting full contact between the electrode active material and the electrolyte while also facilitating desolvation. Therefore, Example 1 exhibits superior overall performance.

[0196] In Examples 1 and 4-5, we further discussed the effect of adding barium titanate. It can be observed that compared with Examples 4-5, Example 1 exhibits better comprehensive performance, indicating that when the mass proportion of barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 2% to 4%, it helps to further optimize the structure of the sodium iron pyrophosphate-barium titanate positive electrode material and exert the polarization effect of barium titanate. Therefore, Example 1 exhibits the best reversible specific capacity, rate capacity at 60C and cycle performance.

[0197] The presence of the chelating agent not only complexes the transition metal ions but also avoids the introduction of impurity ions. In Examples 1, 6-7, we discussed the effect of the amount of chelating agent on this solution. It can be observed that when the molar ratio of the iron source to the chelating agent satisfies the iron source: chelating agent = (1.5-2.5): 1, Example 1 exhibits the optimal rate capacity at 60C. This may be because when the molar ratio of the iron source to the chelating agent satisfies the (1.5-2.5): 1, it helps to better exert the complexing effect of the chelating agent on the transition metal ions and form a more uniform complex, thereby allowing Example 1 to exhibit better performance.

[0198] The various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-described embodiments are exemplary and cannot be understood as limitations of the present invention. Those skilled in the art can change, modify, replace and deform the above-described embodiments within the scope of the present invention. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

Claims

1. A high-rate sodium iron pyrophosphate-barium titanate positive electrode material, characterized in that: The porous structure of sodium ferric phosphate pyrophosphate is used as the main material, and nano-barium titanate is in-situ compounded in the sodium ferric phosphate pyrophosphate. The mass proportion of the barium titanate in the porous sodium ferric phosphate pyrophosphate is 0.5-6wt%.

2. The high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 1, characterized in that: The general formula of the sodium ferric phosphate pyrophosphate is Na x Fe y (PO4) z P2O7, where 2.8≤x≤4.2, 1.8≤y≤3.2, 0.8≤z≤2.2; Alternatively, in the sodium ferric pyrophosphate, 2.8≤x≤3.5, 1.8≤y≤2.5, and 0.8≤z≤1.

5.

3. The high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 1, characterized in that: The sodium iron pyrophosphate-barium titanate cathode material has a micron-scale and nano-scale secondary pore structure, wherein the micron-scale pore size range is less than 2 μm, and the nano-scale pore size range is selected from 10 nm to 60 nm; And / or, the particle size of the barium titanate is selected from 50 nm to 150 nm; and / or, the sodium iron pyrophosphate-barium titanate positive electrode material has a rate specific capacity greater than 65 mAh / g at 60C; And / or, the sodium iron pyrophosphate-barium titanate positive electrode material has an initial 60C / 1C rate capacity percentage greater than 70%.

4. A method for preparing the high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to any one of claims 1 to 3, characterized in that: The steps include: S1: Dispersing nano-barium titanate into a solvent containing a chelating agent according to the product stoichiometric ratio, and adding an iron source to obtain solution A; S2: dissolving a sodium source and a phosphorus source in a solvent according to the product stoichiometric ratio to obtain a solution B, mixing solutions A and B, evaporating the solvent, and drying to obtain a sodium iron pyrophosphate-barium titanate cathode material precursor; S3: calcining the sodium iron phosphate pyrophosphate-barium titanate positive electrode material precursor to obtain the sodium iron phosphate pyrophosphate-barium titanate positive electrode material.

5. The method for preparing a high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 4, characterized in that: The mass proportion of the barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 0.5wt% to 6wt%; Alternatively, the mass proportion of the barium titanate in the sodium iron pyrophosphate-barium titanate positive electrode material is selected from 2wt% to 4wt%.

6. The method for preparing a high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 4, characterized in that: The molar ratio of the iron source to the chelating agent is selected from (0.5-3.5): 1; And / or, the concentration of the iron source in the solvent is selected from 0.1-0.2 mol / L.

7. The method for preparing a high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 4, characterized in that: The iron source is selected from any one or more of ferric salts and ferrous salts; and / or, the chelating agent is selected from any one or more of polyhydroxy aldehydes, polyhydroxy acids, and dicarboxylic acids; And / or, in steps S1 and S2, the solvent is selected from any one or more of deionized water or alcohol solvents; And / or, the sodium source is selected from any one or more of inorganic sodium salts and organic sodium salts; And / or, the phosphorus source is selected from any one or more of phosphates, phosphoric acid and phosphorus oxides.

8. The method for preparing a high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 4, characterized in that: In step S2, when the solution A and the solution B are mixed by stirring, the stirring time is selected from 40-60 min, and the stirring speed is selected from 500 r / min-800 r / min; And / or, in step S2, the temperature of evaporating the solvent is selected from 70°C to 90°C; And / or, in step S2, the drying temperature is selected from 80°C to 120°C; And / or, in step S2, the drying time is selected from 6h-10h; And / or, in step S3, before calcining the sodium iron pyrophosphate-barium titanate positive electrode material precursor, the sodium iron pyrophosphate-barium titanate positive electrode material precursor is first ground into powder; And / or, in step S3, calcining the sodium iron pyrophosphate-barium titanate positive electrode material precursor is performed in an inert atmosphere.

9. The method for preparing a high-rate sodium iron pyrophosphate-barium titanate positive electrode material according to claim 4, characterized in that: During the calcination in step S3, the sintered steel is first pre-sintered at 300-380°C for 1-6 hours, and then naturally cooled and then calcined at 500-700°C for 5-12 hours. Alternatively, during the calcination in step S3, the sintering is first performed at 330° C.-360° C. for 3-6 hours, and then, after natural cooling, the calcination is continued at 500-600° C. for 8-12 hours.

10. A positive electrode sheet or energy storage device, characterized in that: The invention relates to a high-rate sodium iron phosphate pyrophosphate-barium titanate positive electrode material according to any one of claims 1 to 3, or a high-rate sodium iron phosphate pyrophosphate-barium titanate positive electrode material prepared by the method according to any one of claims 4 to 9.

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