High-magnification ferric sodium pyrophosphate-barium titanate positive electrode material and preparation method thereof

Abstract

The invention discloses a high-magnification sodium ferric phosphate pyrophosphate-barium titanate positive electrode material and a preparation method thereof, the high-magnification sodium ferric phosphate pyrophosphate-barium titanate positive electrode material comprises nano barium titanate compounded with sodium ferric phosphate pyrophosphate in situ, the sodium ferric phosphate pyrophosphate is of a porous structure, and the mass ratio of barium titanate in the porous sodium ferric phosphate pyrophosphate is 0.5-6 wt%. The nano barium titanate is introduced into the porous ferric sodium phosphate pyrophosphate through an in-situ compounding technology, so that the rate capability, the cycle capability and the ionic conductivity of the ferric sodium phosphate pyrophosphate-barium titanate positive electrode material are remarkably improved, and the rate capability during high-current charging and discharging is particularly optimized; and effective support is provided for high-power output in a short time and stability of long-time circulation.

Description

Technical Field

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

[0002] As a new type of energy storage system, sodium-ion batteries have been widely used in many fields such as renewable energy storage, electric vehicles, and power grid dispatching due to their significant advantages such as low cost and rich resources. Especially in high-load application scenarios such as power load regulation and rapid response, sodium-ion batteries need to have higher fast charge and discharge capabilities, that is, output a large power in a short time, and at the same time maintain high cycle stability during long-term use. Therefore, sodium iron pyrophosphate (NFPP) has gradually come into people's view.

[0003] NFPP is an ionic compound containing pyrophosphate groups. Its unique three-dimensional framework structure can provide a stable channel for the insertion and extraction of sodium ions. Therefore, while realizing the rapid insertion and extraction of sodium ions, NFPP can also avoid the problem of structural collapse caused by volume change during charge and discharge, thereby effectively extending the cycle life of the battery. However, with the increasingly wide application of batteries in life, people have put forward higher requirements for the rate performance and cycle ability of NFPP. To optimize the rate and cycle performance of NFPP, people have begun to try to introduce other highly conductive materials into NFPP, such as doping elements such as titanium, aluminum, manganese, nitrogen, sulfur, etc. into NFPP or compounding NFPP with materials such as carbon nanotubes and graphene. Although such modification further improves the rate performance of NFPP to a certain extent, during short-term high-load operation, rapidly migrating ions and electrons may still cause structural changes in the electrode material, thereby affecting the cycle life; and coating or covering NFPP to optimize its cycle performance may have an inhibitory effect on the rate performance of the battery, especially more obvious during high-current charge and discharge.

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

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

[0006] In a first aspect, the present invention provides a high-rate sodium iron pyrophosphate titanate barium cathode material, including nano-sized barium titanate in-situ composite with sodium iron pyrophosphate. The sodium iron pyrophosphate has a porous structure, and the mass ratio of barium titanate in the porous sodium iron pyrophosphate is 0.5 - 6 wt%.

[0007] As a further solution, the general formula of the sodium iron 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.

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

[0009] As a further solution, the sodium iron pyrophosphate titanate barium cathode material has a secondary pore structure at the micron and nano scales. Among them, the pore diameter range of the micron-scale pores is less than 2 μm, and the pore diameter range of the nano-scale pore structure is selected from 10 nm to 60 nm.

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

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

[0012] As a further solution, the 1C cycle retention rate of the sodium iron pyrophosphate titanate barium cathode material after 350 cycles is greater than 95%.

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

[0014] Preferably, the rate capacity percentage of the sodium iron pyrophosphate titanate barium cathode material for the first time at 60C / 1C is greater than 70%.

[0015] Preferably, the rate capacity percentage of the sodium iron pyrophosphate titanate barium cathode material for the first time at 60C / 1C is greater than 73%.

[0016] In a second aspect, the present solution provides a preparation method of a sodium iron pyrophosphate titanate barium cathode material, including the following steps: S1: According to the product stoichiometric ratio, disperse nano-sized barium titanate into a solvent containing a chelating agent, and add an iron source to obtain solution A; S2: Dissolve the sodium source and phosphorus source in a solvent according to the product stoichiometric ratio to obtain solution B. After mixing solutions A and B, evaporate the solvent and dry it to obtain the sodium iron pyrophosphate - barium titanate cathode material precursor. S3: Calcinate the sodium iron pyrophosphate - barium titanate cathode material precursor to obtain the sodium iron pyrophosphate - barium titanate cathode material.

[0017] As a further solution, the mass proportion of barium titanate in the sodium iron pyrophosphate - barium titanate cathode material is selected from 0.5 wt% to 6 wt%.

[0018] As some preferred solutions, the mass proportion of barium titanate in the sodium iron pyrophosphate - barium titanate cathode material is selected from 2 wt% to 4 wt%.

[0019] As a further solution, the particle size of barium titanate is selected from 50 nm to 150 nm.

[0020] As some preferred solutions, the particle size of barium titanate is selected from 80 nm to 120 nm.

[0021] As a further solution, the molar ratio of the iron source to the chelating agent is selected from (0.5 - 3.5):1.

[0022] As some preferred solutions, the molar ratio of the iron source to the chelating agent is selected from (1.5 - 2.5):1.

[0023] As a further solution, the concentration of the iron source in the solvent is selected from 0.1 - 0.2 mol / L.

[0024] As a further solution, the iron source is selected from any one or more of ferric salts and ferrous salts.

[0025] As a further solution, the chelating agent is selected from any one or several of polyhydroxy aldehydes, polyhydroxy acids, and dicarboxylic acids.

[0026] As a further solution, in steps S1 and S2, the solvent is selected from any one of deionized water or alcohol solvents.

[0027] As a further solution, the sodium source is selected from any one of inorganic sodium salts and organic sodium salts.

[0028] As a further solution, the phosphorus source is selected from phosphates, phosphoric acid, and oxides of phosphorus.

[0029] As a further solution, in step S2, when mixing solutions A and B, the mixing method is not limited in principle, and those skilled in the art can choose any one method such as stirring or ultrasonic wave to mix solutions A and B.

[0030] As a further solution, when mixing solution A and solution B by stirring, the stirring time is selected from 40 - 60 min, and the stirring speed is selected from 500 r / min - 800 r / min.

[0031] As a further solution, in step S2, the temperature for evaporating the solvent is selected from 70°C - 90°C.

[0032] As a further solution, in step S2, the drying temperature is selected from 80°C - 120°C.

[0033] As a further solution, in step S2, the drying time is selected from 6 h - 10 h.

[0034] As a further solution, in step S3, before calcining the sodium iron pyrophosphate - barium titanate cathode material precursor, the sodium iron pyrophosphate - barium titanate cathode material precursor is first ground into powder.

[0035] As a further solution, in step S3, the calcination of the sodium iron pyrophosphate - barium titanate cathode material precursor is carried out in an inert atmosphere.

[0036] As a further solution, the inert atmosphere is selected from any one of helium, neon, argon, and nitrogen.

[0037] As a further solution, the inert atmosphere is preferably argon or nitrogen.

[0038] As a further solution, when carrying out the calcination in step S3, first pre - sinter at 300°C - 380°C for 1 - 6 h, and after natural cooling, continue to calcine at 500 - 700°C for 5 - 12 h.

[0039] As some preferred solutions, when carrying out the calcination in step S3, first pre - sinter at 330°C - 360°C for 3 - 6 h, and after natural cooling, continue to calcine at 500 - 600°C for 8 - 12 h.

[0040] As a further solution, the heating rate during calcination is selected from 5 - 10°C / min.

[0041] In a third aspect, this solution provides a battery using the sodium iron pyrophosphate - barium titanate cathode material as the cathode active material.

[0042] As a further solution, the battery includes a positive electrode plate, a negative electrode plate, and a separator.

[0043] As a further solution, the positive electrode plate includes a positive current collector, a positive conductive agent, and a positive binder.

[0044] As a further embodiment, the positive 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 may be mentioned.

[0045] As a further embodiment, the positive electrode conductive agent is selected from any one or more of carbon materials, metal materials, and conductive polymers.

[0046] As a further embodiment, the positive electrode binder is selected from at least one of thermoplastic resins, acrylic resins, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0047] As a further embodiment, the negative electrode plate can directly use a sodium sheet or a plate including a negative electrode active material, a negative electrode current collector, a negative electrode conductive agent, and a negative electrode binder.

[0048] As a further embodiment, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon microspheres (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 and one or more of Li-Al alloy As a further embodiment, the negative electrode current collector is not limited in principle. For example, any one of aluminum, nickel, tin, copper, and stainless steel can be selected.

[0049] As a further embodiment, the negative electrode conductive agent is selected from carbon materials.

[0050] As a further embodiment, the negative electrode binder is selected from any one or more of polymers, rubbers, cellulose derivatives, and resins.

[0051] As a further embodiment, the separator is not limited. Those skilled in the art can select any one of, for example, glass fiber separator, polyimide (PI) separator, polyether ether ketone (PEEK) separator, polyethylene terephthalate (PET) separator, and non-woven fabric separator according to requirements.

[0052] As a further embodiment, the battery may further include a solid electrolyte or an electrolyte solution, and the solid electrolyte or the electrolyte solution is not limited. Those skilled in the art can select the corresponding electrolyte solution or solid electrolyte according to requirements.

[0053] Fourthly, the present solution also provides an electrochemical device, which includes using the high-rate sodium iron pyrophosphate-titanium barium phosphate cathode material proposed in the present solution as the cathode active material. The electrochemical device refers to a device that uses electrochemical reactions for material conversion and energy conversion, including but not limited to primary batteries, electrolytic cells, electrochemical workstations, and electrochemical reactors.

[0054] Fifthly, the present solution also proposes an energy storage device, which is composed of a combination of multiple batteries or electrochemical devices and is used for storing and releasing electrical energy.

[0055] Sixthly, the present solution also provides an electrical device, which includes using the high-rate sodium iron pyrophosphate-titanium barium phosphate cathode material proposed in the present solution as the cathode active material. The electrical device refers to all devices and systems that require electricity to operate, which may include one or more of energy storage devices, batteries, and electrochemical devices.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects: Through the in-situ composite technology, the present invention introduces nanoscale barium titanate particles into porous sodium iron pyrophosphate, significantly improving the overall performance of the sodium iron pyrophosphate-titanium barium phosphate cathode material. In the sodium iron pyrophosphate-titanium barium phosphate cathode material, the unique spontaneous polarization property of nanoscale barium titanate forms a built-in electric field, promoting the rapid diffusion of Na⁺, optimizing the rate performance, and enabling the material to maintain a high capacity under high-current charge and discharge conditions. At the same time, the piezoelectric-induced polarization electric field of barium titanate accelerates the desolvation process, increases the ionic conductivity, and promotes the formation of a thin, uniform, stable, and inorganic-rich CEI interface film during the charge and discharge process, optimizing the interfacial diffusion kinetics and significantly enhancing the cycle stability of the battery. With these advantages, the sodium iron pyrophosphate-titanium barium phosphate cathode material exhibits excellent rate performance and cycle stability, providing important material support for the research and development of high-performance sodium-ion batteries. Description of the Drawings

[0057] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0058] Figure 1 In which, a is the XRD pattern of Example 1, and b is the XRD pattern of Comparative Example 1; Figure 2 It is the SEM image of barium titanate as a raw material in Example 1; Figure 3In this figure, a is the SEM image of Comparative Example 1, and b is the SEM image of Example 1; Figure 4 In this figure, a is the FIB image of Comparative Example 1, and b is the FIB image of Example 1; Figure 5 This is the line scan result of the sodium iron pyrophosphate titanate cathode material prepared in Example 1; Figure 6 This is the first charge-discharge graph of Example 1 and Comparative Example 1 at 0.1C; Figure 7 This is the rate performance graph of Example 1 and Comparative Example 1; Figure 8 This is the cycle graph of Example 1 and Comparative Example 1; Figure 9 In this figure, Figure a is the TEM image after cycling of Example 1, and Figure b is the TEM image after cycling of Comparative Example 1. Among them, the area outlined by the white dotted line is the CEI film formed after cycling; Figure 10 In this figure, Figure a is the XPS image of Comparative Example 1 before and after cycling, and Figure b is the XPS image of Example 1 before and after cycling; Figure 11 This is the BET result of Example 1. Detailed implementation mode

[0059] For ease of understanding, the present invention will be described more comprehensively below, and embodiments of the present invention are given, but the scope of the present invention is not limited thereby.

[0060] The following are explanations of terms or words, and unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention pertains.

[0061] In this article, the term "polyhydroxy aldehyde" refers to a class of organic compounds containing at least two hydroxyl groups (-OH) and one aldehyde group (-CHO).

[0062] In this article, the term "polyhydroxy acid" refers to an organic acid containing at least two hydroxyl groups (-OH).

[0063] In this article, the term "dicarboxylic acid" refers to a class of organic compounds containing two carboxyl groups (-COOH) functional groups.

[0064] In a first aspect, the present invention provides a high-rate sodium iron pyrophosphate titanate cathode material, including nano-barium titanate in-situ composite with sodium iron pyrophosphate. The sodium iron pyrophosphate has a porous structure, and the mass ratio of barium titanate in the porous sodium iron pyrophosphate is 0.5 - 6 wt%.

[0065] To further optimize the rate performance of NFPP, improve the cycling ability of NFPP, and enable fast charging and discharging of the battery, barium titanate is introduced into NFPP in this solution; 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, thus forming a polarization phenomenon. Compared with other ferroelectric materials, barium titanate has better dielectric constant, piezoelectric effect, and stronger chemical and thermal stability, and can provide unique advantages in optimizing rate performance, enhancing cycling ability, promoting the contact between electrode active materials and electrolytes, and increasing the structural stability of materials. Therefore, in this solution, we will use in-situ composite technology to introduce nanoscale barium titanate particles into porous sodium pyrophosphate iron phosphate. The nanoscale barium titanate particles can utilize the built-in electric field brought by the polarization effect to provide a driving force for Na + diffusion, thereby accelerating the migration of Na + and improving the rate performance; at the same time, the piezoelectric-induced polarization electric field constructed by barium titanate can effectively accelerate the process of desolvation, thereby further enhancing the ionic conductivity, and can help build a thin, uniform, stable, and inorganic-rich CEI interface film during the sodium storage process, thereby enhancing the interfacial diffusion kinetics of the material and optimizing the battery cycling performance; in addition, in this solution, the mass ratio of barium titanate in porous sodium pyrophosphate iron phosphate is set to 0.5-6 wt%. By controlling the mass ratio of barium titanate in porous sodium pyrophosphate iron phosphate, it helps to give full play to the self-polarization effect of barium titanate while protecting the structure of porous sodium pyrophosphate iron phosphate, and at the same time coordinates with the particle size of barium titanate to optimize the pore size of porous sodium pyrophosphate iron phosphate, thereby promoting the full contact between electrode active materials and electrolytes; under the interaction of porous sodium pyrophosphate iron phosphate and barium titanate, the porous sodium pyrophosphate iron phosphate-barium titanate material obtained in this solution exhibits excellent rate performance and cycling ability, and at the same time significantly improves the rate capacity during high-current charging and discharging.

[0066] As some examples, the general formula of the sodium pyrophosphate iron phosphate is Na x Fe y (PO4) z P2O7, where 2.8 ≤ x ≤ 4.2, 1.8 ≤ y ≤ 3.2, 0.8 ≤ z ≤ 2.2.

[0067] As some preferred examples, in the sodium pyrophosphate iron phosphate, 2.8 ≤ x ≤ 3.5, 1.8 ≤ y ≤ 2.5, 0.8 ≤ z ≤ 1.5.

[0068] As some examples, such as Figure 3 b, Figure 4b. The sodium iron pyrophosphate - barium titanate cathode material has a secondary pore structure at the micron and nanometer scales. The pore diameter range of the micron - scale pores is less than 2 μm, and the pore diameter range of the nanometer - scale pore structure 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, promotes the contact between the electrolyte and the electrode material, thereby accelerating the diffusion process of sodium ions in the material and improving the charge - 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, thus realizing desolvation.

[0069] As some preferred examples, the pore diameter range of the micron - scale pores is less than 1.5 μm, and the pore diameter range of the nanometer - scale pore structure is selected from 25 nm to 50 nm ( Figure 11 ).

[0070] As some examples, the reversible specific capacity of the sodium iron pyrophosphate - barium titanate cathode material is selected from 89.1 - 92 mAh / g.

[0071] As some examples, the 1C cycle retention rate of the sodium iron pyrophosphate - barium titanate cathode material after 350 cycles is greater than 95%.

[0072] As some examples, the rate specific capacity of the sodium iron pyrophosphate - barium titanate cathode material at 60C is greater than 65 mAh / g.

[0073] Preferably, the rate capacity percentage of the sodium iron pyrophosphate - barium titanate cathode material at the first 60C / 1C is greater than 70%; Preferably, the rate capacity percentage of the sodium iron pyrophosphate - barium titanate cathode material at the first 60C / 1C is greater than 73%.

[0074] In the second aspect, this solution provides a preparation method of a sodium iron pyrophosphate - barium titanate cathode material, including the following steps: S1: According to the product stoichiometric ratio, disperse nanometer - scale barium titanate into a solvent containing a chelating agent, and add an iron source to obtain solution A; S2: According to the product stoichiometric ratio, dissolve a sodium source and a phosphorus source in a solvent to obtain solution B. After mixing solutions A and B, evaporate the solvent and dry it to obtain a sodium iron pyrophosphate - barium titanate cathode material precursor; S3: Calcinate the sodium iron pyrophosphate - barium titanate cathode material precursor to obtain the sodium iron pyrophosphate - barium titanate cathode material.

[0075] As some examples, the mass percentage of barium titanate in the sodium iron pyrophosphate - barium titanate cathode material is selected from 0.5 wt% to 6 wt%. Such a range helps to protect the porous sodium iron pyrophosphate structure while giving full play to the role of barium titanate, thereby improving the reversible specific capacity of the sodium iron pyrophosphate - barium titanate cathode material and the charge - discharge performance at high voltages, and optimizing the cycle performance of the sodium iron pyrophosphate - barium titanate cathode material.

[0076] As some preferred examples, the mass percentage of barium titanate in the sodium iron pyrophosphate - barium titanate cathode material is selected from 2 wt% to 4 wt%. We believe that a barium titanate content of 2 wt% to 4 wt% helps to better optimize the role of barium titanate and the structure of the sodium iron pyrophosphate - barium titanate cathode material, thereby improving the comprehensive performance of the sodium iron pyrophosphate - barium titanate cathode material.

[0077] As some examples, the particle size of barium titanate is selected from 50 nm to 150 nm. On the one hand, the polarization characteristics of barium titanate (including spontaneous polarization and piezoelectric effect) depend on its crystal structure, especially the position of titanium ions deviating from the center of the oxygen octahedron. When the particle size of barium titanate is selected from 50 nm to 150 nm, it helps to better play the polarization role of barium titanate, thereby optimizing the comprehensive performance of the sodium iron pyrophosphate - barium titanate cathode material. On the other hand, when the particle size of barium titanate is selected from 50 nm to 150 nm, it also helps to match the pores on the porous sodium iron pyrophosphate, further optimizing the comprehensive performance of the sodium iron pyrophosphate - barium titanate cathode material.

[0078] As some preferred examples, the particle size of barium titanate is selected from 80 nm to 120 nm, which not only helps barium titanate to obtain more interfaces and higher surface energy, strengthen the polarization effect of barium titanate, and promote the migration of Na + ions, but also can synergistically optimize the pore structure with the barium titanate content, promote the full contact between the electrode and the electrolyte, thereby increasing the ion migration speed, conductivity of the material, and the rate performance of the battery.

[0079] As some examples, the molar ratio of the iron source to the chelating agent is selected from (0.5 - 3.5):1.

[0080] As some preferred examples, the molar ratio of the iron source to the chelating agent is selected from (1.5 - 2.5):1.

[0081] As some examples, the concentration of the iron source in the solvent is selected from 0.1 - 0.2 mol / L.

[0082] As some examples, the iron source is selected from any one or more of ferric salts and ferrous salts.

[0083] As some examples, the ferric salts include, but are not limited to, any one or more of ferric sulfate, ferric chloride, and ferric nitrate.

[0084] As some examples, the ferrous salts are selected from any one or more of ferrous oxalate, ferrous acetylacetonate, ferrous citrate, and ferrous sulfate.

[0085] 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 generates gas at high temperature, achieving the immobilization of barium titanate while endowing the sodium iron pyrophosphate-barium titanate cathode material with a unique secondary pore structure. This structure with both micron-sized pores and nano-sized pores helps to provide different diffusion channels for ions, thus more efficiently completing the transfer of ions during the charge and discharge process of the battery, promoting the contact between the electrolyte and the electrode material, and improving the interfacial reaction.

[0086] Therefore, as some examples, the chelating agent is selected from any one or several of polyhydroxy aldehydes, polyhydroxy acids, and dicarboxylic acids.

[0087] As some examples, the polyhydroxy aldehydes are selected from any one or several of glyceraldehyde, glucose, and mannose.

[0088] As some examples, the polyhydroxy acids are selected from any one or several of ascorbic acid, citric acid, and methane tricarboxylic acid.

[0089] As some examples, the dicarboxylic acids are selected from any one or several of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid As some examples, in the process of synthesizing the sodium iron pyrophosphate-barium titanate cathode material, different iron sources, sodium sources, and phosphorus sources have different dissolution 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 alcohol solvents. Therefore, in steps S1 and S2, the solvent is selected from any one of deionized water or alcohol solvents.

[0090] 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 dissolution characteristics of the iron source, sodium source, and phosphorus source on the one hand, making them better soluble in the solvent and 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 cathode material.

[0091] As some examples, the alcohol solvents include, but are not limited to, any one of ethanol, methanol, propanol, and isopropanol.

[0092] As some examples, the sodium source is selected from any one of inorganic sodium salts and organic sodium salts.

[0093] As some examples, the inorganic sodium salts are not limited in principle and include any one or more of, but are not limited to, sodium hydroxide, sodium chloride, sodium sulfate, sodium carbonate, sodium bicarbonate, sodium nitrate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium dihydrogen phosphate dihydrate.

[0094] As some examples, the organic sodium salts include any one or more of, but are not limited to, sodium acetate, sodium citrate, and sodium carboxymethyl cellulose.

[0095] As some examples, the phosphorus source is selected from phosphates, phosphoric acid, and oxides of phosphorus.

[0096] As some examples, the phosphates include any one or more of, but are not limited to, disodium hydrogen phosphate, sodium dihydrogen phosphate dihydrate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and sodium pyrophosphate.

[0097] As some examples, the oxides of phosphorus include any one or more of, but are not limited to, phosphorus pentoxide and phosphorus trioxide.

[0098] As some preferred examples, the phosphorus source and the sodium source are preferably substances containing both phosphorus element and sodium element, including any one or more of, but are not limited to, sodium dihydrogen phosphate dihydrate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

[0099] As some examples, in step S2, when mixing solution A and solution B, the mixing method is not limited in principle, and those skilled in the art can choose any one method such as stirring or ultrasonic wave to mix solution A and solution B.

[0100] As some examples, when mixing solution A and solution B by stirring, the stirring time is selected from 40 - 60 min, and the stirring speed is selected from 500 r / min - 800 r / min.

[0101] As some examples, in step S2, the temperature for evaporating the solvent is selected from 70°C - 90°C.

[0102] As some examples, in step S2, the drying temperature is selected from 80°C - 120°C.

[0103] As some examples, in step S2, the drying time is selected from 6 h - 10 h.

[0104] As some examples, in step S3, before calcining the sodium iron pyrophosphate - barium titanate cathode material precursor, the sodium iron pyrophosphate - barium titanate cathode material precursor is first ground into powder.

[0105] As some examples, in step S3, the calcination of the sodium iron pyrophosphate titanate-barium titanate cathode material precursor is carried out in an inert atmosphere.

[0106] As some examples, the inert atmosphere is selected from any one of helium, neon, argon, and nitrogen.

[0107] As some examples, the inert atmosphere is preferably argon or nitrogen.

[0108] As some examples, when carrying out the calcination in step S3, first pre-sinter at 300°C - 380°C for 1 - 6 h, and after natural cooling, continue to calcine at a temperature of 500 - 700°C for 5 - 12 h.

[0109] As some preferred examples, when carrying out the calcination in step S3, first pre-sinter at 330°C - 360°C for 3 - 6 h, and after natural cooling, continue to calcine at a temperature of 500 - 600°C for 8 - 12 h.

[0110] As some examples, the heating rate during calcination is selected from 5 - 10°C / min.

[0111] In a third aspect, this solution provides a battery that uses the sodium iron pyrophosphate titanate-barium titanate cathode material as the cathode active material.

[0112] As some examples, the battery includes a positive electrode plate, a negative electrode plate, and a separator.

[0113] As some examples, the positive electrode plate includes a positive electrode current collector, a positive electrode conductive agent, and a positive electrode binder.

[0114] 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.

[0115] As some examples, the positive electrode conductive agent is selected from any one or several of carbon materials, metal materials, and conductive polymers.

[0116] As some examples, the carbon materials are selected from any one or several of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber.

[0117] As some examples, the metal materials are selected from any one or several of copper, nickel, aluminum, and silver.

[0118] As some examples, the conductive polymer is selected from one or more of polyfluorene (PF), polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh), poly(ethylenedioxythiophene) (PEDOT), poly(ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), and polyacetylene (PA).

[0119] As some examples, the positive electrode binder is selected from at least one of thermoplastic resins, acrylic resins, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0120] As a further embodiment, the thermoplastic resin includes at least one of polyvinylidene fluoride, polyvinyl fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene.

[0121] As some examples, the negative electrode sheet can directly use a sodium sheet or a sheet including a negative electrode active material, a negative electrode current collector, a negative electrode conductive agent, and a negative electrode binder.

[0122] As some examples, the negative electrode active material is selected from natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon - carbon composite, Li - Sn alloy, Li - Sn - O alloy, Sn, SnO, SnO2, lithiated TiO2 - Li4Ti5O with a spinel structure 12 , and one or several of Li - Al alloy.

[0123] 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.

[0124] As some examples, the negative electrode conductive agent is selected from carbon materials.

[0125] As some examples, the carbon material as the negative electrode conductive agent is selected from any one or several 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.

[0126] As some examples, the negative electrode binder is selected from any one or several of polymers, rubbers, cellulose derivatives, and resins.

[0127] As some examples, the polymers are selected from any one or more of polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, poly(vinylidene fluoride), polyvinylpyrrolidone, polyethylene, polypropylene, polyimide, polyacrylic acid, polyvinyl chloride, polytetrafluoroethylene, poly(vinylidene difluoride).

[0128] As some examples, the rubbers are selected from any one or more of styrene-butadiene rubber, ethylene-propylene-diene monomer rubber, fluororubber.

[0129] As some examples, the cellulose derivatives are selected from any one or more of carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose.

[0130] As some examples, the resins are selected from any one or more of epoxy resin, styrene.

[0131] As some examples, the separator is not limited, and those skilled in the art can select any one of, such as, glass fiber separator, polyimide (PI) separator, polyetheretherketone (PEEK) separator, polyethylene terephthalate (PET) separator, non-woven fabric separator according to requirements.

[0132] As some examples, the battery may further include a solid electrolyte or an electrolyte solution, and the solid electrolyte or the electrolyte solution is not limited, and those skilled in the art can select the corresponding electrolyte solution or solid electrolyte according to requirements.

[0133] In a fourth aspect, the present solution further provides an electrochemical device, including using the high-rate sodium iron pyrophosphate-titanium barium composite cathode material proposed in the present solution as a cathode active material. The electrochemical device refers to a device that uses an electrochemical reaction for material conversion and energy conversion, including but not limited to a primary battery, an electrolytic cell, an electrochemical workstation, an electro-chemical reactor.

[0134] In a fifth aspect, the present solution further proposes an energy storage device, which is composed of a plurality of batteries or electrochemical devices combined together and is used for storing and releasing electric energy.

[0135] In a sixth aspect, the present solution further provides an electrical equipment, including using the high-rate sodium iron pyrophosphate-titanium barium composite cathode material proposed in the present solution as a cathode active material. The electrical equipment refers to all equipment and systems that require electricity to operate, which may include one or more of energy storage devices, batteries, electrochemical devices.

[0136] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application and do not represent all possible embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0137] The chemical raw materials involved in the following examples and comparative examples are all prior arts and are obtained through commercial purchases. The experimental devices, testing devices, etc. involved in the following examples and comparative examples are all conventional devices in the art and have no special requirements and limitations.

[0138] Example 1 S1: According to the stoichiometric ratio, barium titanate is dispersed in 100 g of an ethanol solution containing citric acid. Subsequently, 0.012 mol of iron acetylacetonate is dissolved in the above ethanol solution to obtain solution A, where the addition amount of citric acid is 0.006 mol, and the average particle size of barium titanate is selected from 100 nm (as Figure 2 shown); S2: Sodium dihydrogen phosphate is used as the sodium source and phosphorus source. 0.018 mol of sodium dihydrogen phosphate is dissolved in 100 g of deionized water to obtain solution B; solutions A and B are mixed at a rotation speed of 750 r / min, stirred for 50 min, and then the solvent is evaporated at 80 °C. Subsequently, it is kept at 90 °C in a drying oven for 8 h to obtain a sodium iron pyrophosphate - barium titanate cathode material precursor; S3: The sodium iron pyrophosphate - barium titanate cathode material precursor is ground into powder. Subsequently, in an argon atmosphere, it is heated to 350 °C at a rate of 5 °C / min, held for 5 h, and then naturally cooled to room temperature. Subsequently, it is heated to 550 °C at the same rate and calcined for 10 h. After cooling, a sodium iron pyrophosphate - barium titanate cathode material is obtained, where the molecular formula of sodium iron pyrophosphate is Na3Fe2(PO4)P2O7, and the mass content of barium titanate is 3%.

[0139] Example 2 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 to replace barium titanate with a particle size of 100 nm.

[0140] Example 3 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 to replace barium titanate with a particle size of 100 nm.

[0141] Example 4 The synthesis conditions and preparation steps are the same as those in Example 1, except that in the theoretically stoichiometrically generated sodium iron pyrophosphate - barium titanate cathode material, the mass ratio of barium titanate is 1 wt%.

[0142] Example 5 The synthesis conditions and preparation steps are the same as those in Example 1, except that in the sodium iron pyrophosphate titanate cathode material theoretically generated according to the stoichiometric ratio, the mass ratio of barium titanate is 5 wt%.

[0143] Example 6 The synthesis conditions and preparation steps are the same as those in Example 1, except that the amount of citric acid used is 0.012 mol.

[0144] Example 7 The synthesis conditions and preparation steps are the same as those in Example 1, except that the amount of citric acid used is 0.018 mol.

[0145] Comparative Example 1 The synthesis conditions and preparation steps are the same as those in Example 1, except that barium titanate is not added.

[0146] Comparative Example 2 The synthesis conditions and preparation steps are the same as those in Example 1, except that titanium dioxide is used to replace barium titanate.

[0147] Comparative Example 3 The synthesis conditions and preparation steps are the same as those in Example 1, except that barium carbonate is used to replace barium titanate.

[0148] Comparative Example 4 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, stirred for 3 h, then heated to 350 °C at a rate of 5 °C / min under an argon atmosphere, held for 5 h and then naturally cooled to room temperature, and then heated to 550 °C at the same rate, calcined for 10 h, and naturally cooled to obtain a directly mixed calcined barium titanate-sodium iron pyrophosphate material.

[0149] Comparative Example 5 The synthesis conditions and preparation steps are the same as those in Example 1, except that the mass ratio of barium titanate in the total mass of sodium dihydrogen phosphate, iron acetylacetonate and barium titanate is 10 wt%.

[0150] Testing Method The positive electrode slurry was prepared by mixing sodium iron pyrophosphate titanate - barium titanate positive electrode material: Super P: polyvinylidene fluoride in a ratio of 7:2:1, and coated on aluminum foil to prepare the positive electrode. The separator was a glass fiber separator, and the negative electrode was a sodium sheet. A CR2032 coin - type half - cell was made under the condition that the water - oxygen value in the glove box was less than 0.01, and tested on a Neware 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 cycles. 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 each. The first - week 1C reversible specific capacity, 350 - week 1C cycle retention rate, 5 - week rate capacity of charge - discharge at 60C, and first - week 60C / 1C rate specific capacity of the examples and comparative examples were measured.

[0151] Among them, the percentage of the rate capacity of 60C / 1C = (the first - week reversible capacity of the 60C rate performance test / the first - week reversible capacity of the 1C rate performance test) * 100%.

[0152] The test results are shown in Table 1.

[0153] Table 1

[0154] It can be observed from Table 1 that at 60C, Examples 1 - 7 showed better reversible specific capacity, 1C cycle retention rate, and rate capacity at 60C than Comparative Examples 1 - 5, indicating that the sodium iron pyrophosphate titanate - barium titanate positive electrode material proposed in this scheme can effectively utilize the polarization effect of barium titanate to provide a driving force for Na + diffusion, while improving the ionic conductivity and optimizing the cycle performance of the battery.

[0155] First, it can be observed from Figure 1 that both sodium iron pyrophosphate and sodium iron pyrophosphate titanate - barium titanate positive electrode materials were successfully synthesized, Figure 5 and the presence of titanium and barium elements can be clearly observed; and both Comparative Example 1 and Example 1 showed porous characteristics ( Figure 3 , Figure 4 ), and 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 respectively. Secondly, it can be observed from Example 1 and Comparative Example 1 in Table 1 that when barium titanate was not added, there were gaps in the reversible specific capacity and 1C cycle retention rate between Comparative Example 1 and Example 1. When performing large - current charge - discharge (60C), its rate capacity was only 57.92 mAh / g, far lower than 70.21 mAh / g of Example 1. This may be because the introduction of barium titanate can effectively cooperate with sodium iron pyrophosphate, and by using the polarization effect to improve Na +While constructing a more stable CEI interface film during the migration driving force (such as Figure 9 a), when barium titanate is absent, Comparative Example 1 lacks the + migration driving force and it is difficult to construct a stable CEI film ( Figure 9 b), and it can be Figure 10 observed that compared with Example 1, the content of Na-F bonds after cycling in Comparative Example 1 is significantly lower. Therefore, Comparative Example 1 exhibits lower comprehensive performance than Example 1.

[0156] To further determine the role of barium titanate in the sodium iron pyrophosphate phosphate-barium titanate cathode material, when we replace barium titanate with titanium dioxide, which is also a ferroelectric material, and barium carbonate, which also contains barium element (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 endow it with better polarization and can be better compounded with porous sodium iron pyrophosphate phosphate. When using titanium dioxide and barium titanate to replace barium titanate, even if they are ferroelectric materials or contain similar elements, they cannot achieve similar effects. Therefore, the performance of Comparative Examples 2-3 is lower than that of Example 1.

[0157] In Comparative Example 4, we mixed and calcined barium titanate with porous sodium iron pyrophosphate phosphate. It can be observed that when the sodium iron pyrophosphate phosphate-barium titanate cathode material is not prepared by the method proposed in this scheme, Comparative Example 4 also cannot obtain the similar effect as Example 1. This may be because the method proposed in this scheme can realize the in-situ composite of porous sodium iron pyrophosphate phosphate and barium titanate, and barium titanate only stays on the surface of porous sodium iron pyrophosphate phosphate, resulting in the performance of Comparative Example 4 being affected.

[0158] In Example 1 and Comparative Example 5, we discussed the influence of the content of barium titanate on the sodium iron pyrophosphate phosphate-barium titanate cathode material. It can be observed that when the mass content of barium titanate in the sodium iron pyrophosphate phosphate-barium titanate cathode material is 10 wt%, the reversible specific capacity, 1C cycle retention rate, and rate capacity at 60C in Comparative Example 5 are greatly affected. This may be because when the mass content of barium titanate in the sodium iron pyrophosphate phosphate-barium titanate cathode material exceeds 6%, the excessive barium titanate may affect the structure of the sodium iron pyrophosphate phosphate-barium titanate cathode material, thereby affecting the comprehensive performance of the sodium iron pyrophosphate phosphate-barium titanate cathode material, especially the performance in terms of cycling. Therefore, Comparative Example 5 shows results far lower than those of Example 1.

[0159] In this solution, we discussed the effect of particle size on the sodium iron pyrophosphate 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 particle size of barium titanate is selected from 80nm to 120nm, on the one hand, it can fully exert the polarization efficiency of barium titanate and provide stronger driving force for the migration of Na + . On the other hand, it can cooperate with the barium titanate content to optimize the pore size in porous sodium iron pyrophosphate, and the optimized pore structure can optimize the polarization electric field of barium titanate, promoting the full contact between the electrode active material and the electrolyte while promoting desolvation. Therefore, Example 1 exhibits better comprehensive performance.

[0160] In Examples 1, 4-5, we further discussed the effect of the addition of barium titanate. It can be observed that compared with Examples 4-5, Example 1 exhibits better comprehensive performance, indicating that when the mass ratio of barium titanate in the sodium iron pyrophosphate titanate cathode material is selected from 2% to 4%, it helps to further optimize the structure of the sodium iron pyrophosphate titanate cathode material and exert the polarization effect of barium titanate. Therefore, Example 1 exhibits the best reversible specific capacity, rate capacity at 60C, and cycling performance.

[0161] The presence of the chelating agent chelates transition metal ions while avoiding the introduction of impurity ions. In Examples 1, 6-7, we discussed the influence of the dosage of the chelating agent on this solution. It can be observed that when the molar ratio of the iron source to the chelating agent satisfies iron source:chelating agent = (1.5-2.5):1, Example 1 exhibits the best rate capacity at 60C. This may be because when the molar ratio of the iron source to the chelating agent satisfies (1.5-2.5):1, it helps to better exert the chelating effect of the chelating agent on transition metal ions and form a more uniform complex, thus enabling Example 1 to exhibit better performance.

[0162] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and deformations to the above embodiments within the scope of the present invention. In addition, without contradiction, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples.

Claims

1. A high-rate sodium iron pyrophosphate titanate barium cathode material, characterized in that, Using sodium iron pyrophosphate with a porous structure as the main material, barium titanate nanoparticles are in-situ composite in the sodium iron pyrophosphate, and the mass ratio of the barium titanate in the porous sodium iron pyrophosphate is 0.5-6wt%.

2. The high-rate sodium iron pyrophosphate-titanium barium composite cathode material according to claim 1, wherein The sodium iron pyrophosphate phosphate has the general formula 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 iron pyrophosphate, 2.8≤x≤3.5, 1.8≤y≤2.5, 0.8≤z≤1.

5.

3. The high-rate sodium iron pyrophosphate-titanium barium composite cathode material according to claim 1, wherein The sodium iron pyrophosphate-barium titanate cathode material has a secondary pore structure at the micron and nanometer levels. The pore diameter range of the micron-level pores is less than 2μm, and the pore diameter range of the nanometer-level pore structure is selected from 10 nm to 60 nm; and / or, the particle size of the barium titanate is selected from 50nm~150nm; and / or, the rate specific capacity of the sodium iron pyrophosphate-barium titanate cathode material at 60C is greater than 65mAh / g; and / or, the rate capacity percentage of the sodium iron pyrophosphate-barium titanate cathode material at the first 60C / 1C is greater than 70%.

4. A method for preparing the high-rate sodium iron pyrophosphate-titanium barium phosphate cathode material according to any one of claims 1-3, characterized in that, It includes the following steps: S1: According to the product stoichiometric ratio, disperse barium titanate nanoparticles into a solvent containing a chelating agent, and add an iron source to obtain solution A; S2: According to the product stoichiometric ratio, dissolve the sodium source and phosphorus source in a solvent to obtain solution B. After mixing solutions A and B, evaporate the solvent and dry it to obtain a precursor of the sodium iron pyrophosphate-barium titanate cathode material; S3: Calcinate the precursor of the sodium iron pyrophosphate-barium titanate cathode material to obtain the sodium iron pyrophosphate-barium titanate cathode material.

5. The method for preparing sodium iron pyrophosphate-titanium barium composite cathode material with high magnification according to claim 4, wherein, The mass ratio of the barium titanate in the sodium iron pyrophosphate-barium titanate cathode material is selected from 0.5wt%~6wt%; or, the mass ratio of the barium titanate in the sodium iron pyrophosphate-barium titanate cathode material is selected from 2wt%~4wt%.

6. The method for preparing the sodium iron pyrophosphate - barium titanate cathode material with high rate 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 0.1-0.2mol / L.

7. The method for preparing the sodium iron pyrophosphate-titanium barium phosphate cathode material with high magnification 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 several of polyhydroxy aldehydes, polyhydroxy acids, and dicarboxylic acids; and / or, in steps S1 and S2, the solvent is selected from any one or several of deionized water and alcohol solvents; and / or, the sodium source is selected from any one or several of inorganic sodium salts and organic sodium salts; and / or, the phosphorus source is selected from any one or several of phosphates, phosphoric acid, and phosphorus oxides.

8. The method for preparing the sodium iron pyrophosphate-titanium barium phosphate cathode material with high magnification according to claim 4, characterized in that In step S2, when mixing solutions A and B by stirring, the stirring time is selected from 40-60min, and the stirring speed is selected from 500r / min-800r / min; and / or, in step S2, the temperature for evaporating the solvent is selected from 70℃-90℃; and / or, in step S2, the drying temperature is selected from 80℃-120℃; and / or, in step S2, the drying time is selected from 6h-10h; and / or, in step S3, before calcining the precursor of the sodium iron pyrophosphate-barium titanate cathode material, first grind the precursor of the sodium iron pyrophosphate-barium titanate cathode material into powder; and / or, in step S3, the calcination of the precursor of the sodium iron pyrophosphate-barium titanate cathode material is carried out in an inert atmosphere.

9. The method for preparing the sodium iron pyrophosphate-titanium barium phosphate cathode material with high magnification according to claim 4, wherein When calcining in the step S3, first pre-sinter at 300°C - 380°C for 1 - 6 h, and after natural cooling, continue to calcine at a temperature of 500 - 700°C for 5 - 12 h; Alternatively, when calcining in the step S3, first pre-sinter at 330°C - 360°C for 3 - 6 h, and after natural cooling, continue to calcine at a temperature of 500 - 600°C for 8 - 12 h.

10. A positive electrode sheet or energy storage device, characterized in that, It includes the high-rate sodium iron pyrophosphate-titanium barium composite cathode material according to any one of claims 1 - 3, or the high-rate sodium iron pyrophosphate-titanium barium composite cathode material prepared by the method according to any one of claims 4 - 9.

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