Battery monomer and preparation method thereof, battery device, power utilization device and energy storage device

Abstract

The invention provides a battery monomer and a preparation method thereof, a battery device, a power utilization device and an energy storage device. The single battery comprises a positive plate, a composite electrolyte plate and a Li-In alloy negative electrode, the positive plate comprises a positive electrode material, the positive electrode material comprises a modified lithium iron phosphate material, the modified lithium iron phosphate material comprises lithium iron phosphate, a first alloy and a second alloy, the first alloy is doped in lattices of the lithium iron phosphate, the surface of the lithium iron phosphate is coated with the second alloy, and the lithium iron phosphate is doped with the first alloy. The first alloy comprises indium tin bismuth alloy, and the second alloy comprises indium tin bismuth alloy. According to the invention, the indium-tin-bismuth alloy acts on the lithium iron phosphate material in double modes of lattice doping and surface coating at the same time, so that the inherent key technical bottlenecks of poor electronic conductivity, low lithium ion diffusion rate, unstable interface in the circulation process and the like of the lithium iron phosphate material are synergistically solved.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and more specifically, to a battery cell and its manufacturing method, a battery device, an electrical device, and an energy storage device. Background Technology

[0002] Currently, lithium iron phosphate (LFP) cathode materials are widely used in lithium-ion batteries due to their advantages such as high safety, long cycle life, and low cost. However, their low intrinsic electronic conductivity, slow lithium-ion diffusion rate, and poor electrode / electrolyte interface stability severely restrict their application in high-power, low-temperature, and solid-state battery scenarios. To improve their performance, existing technologies mostly employ strategies such as carbon coating, single metal element (e.g., Ti, Mg, Zr) doping, or binary alloy (e.g., Sn-Bi, Sn-Cu) surface modification. While carbon coating can improve electronic conductivity, it reduces electrode tap density, sacrificing volumetric energy density; single metal doping easily causes lattice distortion, leading to capacity decay; binary alloy modification, while improving conductivity to some extent, struggles to simultaneously optimize electronic conduction, ion transport, and interfacial stress buffering. Especially in solid-state battery systems, poor interfacial contact and volume expansion during cycling can easily cause interfacial delamination and a sharp increase in impedance, further deteriorating battery performance.

[0003] Among the aforementioned technologies, existing modification methods have failed to effectively construct multifunctional composite interface structures that combine high electronic conductivity, high ion mobility, and good mechanical flexibility. In particular, there is a lack of novel alloy systems that can synergize with the lithium iron phosphate lattice to form stable ion transport channels. Furthermore, existing processes are mostly limited to single modification modes (such as doping or coating only), making it difficult to achieve synergistic effects between "bulk strengthening" and "surface protection." As a result, the materials still generally suffer from key bottlenecks such as high polarization, poor cycle stability, and insufficient rate performance under high-rate charge-discharge, low-temperature environments, and solid-state battery assembly conditions, making it difficult to meet the material requirements of next-generation high-energy-density and high-safety solid-state lithium-ion batteries. Summary of the Invention

[0004] The main objective of this invention is to provide a battery cell and its preparation method, battery device, power device, and energy storage device to solve the problems of low electronic conductivity, slow ion diffusion rate, and poor interface stability of lithium iron phosphate cathode materials in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a battery cell is provided, comprising a positive electrode, a composite electrolyte sheet, and a Li-In alloy negative electrode. The positive electrode comprises a positive electrode material, which includes a modified lithium iron phosphate material. The modified lithium iron phosphate material comprises lithium iron phosphate, a first alloy, and a second alloy. The first alloy is doped within the lattice of the lithium iron phosphate, and the second alloy is coated on the surface of the lithium iron phosphate. The first alloy comprises an indium tin bismuth alloy, and the second alloy comprises an indium tin bismuth alloy.

[0006] Furthermore, the mass ratio of the first alloy to the second alloy is 30%~50%:50%~70%.

[0007] Furthermore, the total mass of the first alloy and the second alloy accounts for 2.5 to 3.5% of the mass of the modified lithium iron phosphate material.

[0008] Furthermore, the mass ratio of In, Sn and Bi in the first alloy is 0.37~0.39:0.32~0.34:0.28~0.30; the first alloy includes InBi phase and InSn4 phase, and the mass ratio of InBi phase to InSn4 phase is 29:33~50:50.

[0009] Furthermore, the mass ratio of In, Sn and Bi in the second alloy is 0.37~0.39:0.32~0.34:0.28~0.30; the second alloy includes InBi phase and InSn4 phase, and the mass ratio of InBi phase to InSn4 phase is 29:33~50:50.

[0010] To achieve the above objectives, according to another aspect of the present invention, a method for preparing the aforementioned battery cell is provided, comprising preparing a positive electrode material and preparing a positive electrode sheet including the positive electrode material, wherein the positive electrode sheet, a composite electrolyte sheet and a Li-In alloy negative electrode are sequentially stacked and assembled to obtain a battery cell, wherein the positive electrode material includes a modified lithium iron phosphate material, and the method for preparing the modified lithium iron phosphate material includes: step S1, mixing and drying raw materials including a lithium source, an iron source, a phosphorus source, a solvent and an indium tin bismuth alloy to obtain a precursor; step S2, sintering the precursor in a first inert atmosphere to obtain the modified lithium iron phosphate material.

[0011] Further, step S1 includes: mixing raw materials including lithium source, iron source, phosphorus source and solvent to obtain slurry; mixing the slurry with indium tin bismuth alloy and drying it to obtain precursor; wherein the mass of indium tin bismuth alloy is 2.5~3.5% of the mass of slurry; and / or the average particle size of indium tin bismuth alloy is 50~100nm.

[0012] Furthermore, the preparation process of the indium-tin-bismuth alloy includes: in a second inert atmosphere, melting raw materials including In powder, Sn powder and Bi powder according to atomic ratio and then ball milling to obtain the indium-tin-bismuth alloy, wherein the melting temperature is 150~200℃ and the melting time is 30~60min; and / or, the second inert atmosphere is selected from any one or more of Ar, N2 and He.

[0013] Further, in step S1, the first inert atmosphere is selected from any one or more of Ar, N2 and He; and / or, the lithium source is selected from one or more of Li2CO3, LiOH, LiNO3, LiCH3COO, and LiH2PO4; and / or, the iron source is selected from one or more of FeC2O4·2H2O, Fe2O3, Fe3O4, Fe(NO3)3, and FeSO4; and / or, the phosphorus source is selected from one or more of (NH4)2HPO4, NH4H2PO4, H3PO4, LiH2PO4, and P2O5; and / or, the solvent is selected from any one or more of water, ethanol, ethylene glycol, and NMP.

[0014] Further, in step S1, the mixing process is subjected to ultrasonication at a frequency of 20~80kHz for 1.5~2.5h; and / or, the drying temperature is 70~90℃ for 10~14h.

[0015] Further, in step S2, sintering includes a first sintering and a second sintering performed sequentially, wherein the temperature of the second sintering is higher than that of the first sintering; and / or, the temperature of the first sintering is 300~400℃ and the time of the first sintering is 2~3h; and / or, the temperature of the second sintering is 650~750℃ and the time of the second sintering is 5~7h.

[0016] Furthermore, the preparation method also includes the preparation process of the composite electrolyte sheet, which includes: mixing raw materials including LiPSCl, LiPO3 and organic solvent, and then grinding and calcining them sequentially to obtain the composite electrolyte; wherein the mass ratio of LiPSCl to LiPO3 is 7:3~8:2; and / or, the organic solvent is selected from any one or more of ethanol, ethylene glycol and NMP.

[0017] Furthermore, the calcination is carried out in a third inert atmosphere, which is selected from any one or more of Ar, N2 and He; and / or, the calcination temperature is 500~600℃ and the calcination time is 3~4h.

[0018] To achieve the above objectives, according to another aspect of the present invention, a battery device is provided, the battery device including the aforementioned battery cell, and the battery device including one or more of a battery module, a battery pack, and an energy storage battery.

[0019] To achieve the above objectives, according to another aspect of the present invention, an electrical device is provided, which includes the aforementioned battery device for providing electrical energy.

[0020] To achieve the above objectives, according to another aspect of the present invention, an energy storage device is provided, the energy storage device including the aforementioned battery device, the battery device being used to store electrical energy.

[0021] By applying the technical solution of this application, indium tin bismuth alloy is simultaneously applied to lithium iron phosphate materials through both lattice doping and surface coating. The first alloy, doped within the lattice, effectively broadens lithium-ion migration channels, improves electronic conductivity, and stabilizes the crystal structure. The second alloy, coated on the particle surface, constructs a highly conductive and chemically stable interface layer, significantly suppressing side reactions between the cathode and electrolyte and reducing interfacial impedance. The indium tin bismuth alloy possesses a low melting point, high conductivity, and good lithium compatibility. It forms an electron-ion synergistic conduction network within the lattice and an alloy-like buffer layer on the surface, synergistically solving the inherent key technical bottlenecks of lithium iron phosphate materials, such as poor electronic conductivity, slow lithium-ion diffusion rate, and interfacial instability during cycling. Furthermore, this structural design eliminates the need for additional carbon coating or metal oxide modification, simplifying the process. Simultaneously, it forms a matched interface system with the Li-In alloy anode, achieving efficient charge transport and long-term cycle stability in the entire battery system, significantly improving the battery's energy density, power performance, and cycle life. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 A process flow diagram for preparing a modified lithium iron phosphate material according to Embodiment 1 of the present invention is shown. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] As analyzed in the background section of this application, existing lithium iron phosphate cathode materials suffer from low electronic conductivity, slow ion diffusion rate, and poor interface stability. To address these issues, this application provides a battery cell, its preparation method, a battery device, an electrical device, and an energy storage device.

[0026] In a typical embodiment of this application, a battery cell is provided, including a positive electrode sheet, a composite electrolyte sheet, and a Li-In alloy negative electrode. The positive electrode sheet includes a positive electrode material, which includes a modified lithium iron phosphate material. The modified lithium iron phosphate material includes lithium iron phosphate, a first alloy, and a second alloy. The first alloy is doped within the lattice of lithium iron phosphate, and the second alloy is coated on the surface of lithium iron phosphate. The first alloy includes an indium tin bismuth alloy, and the second alloy includes an indium tin bismuth alloy.

[0027] This application applies an indium tin bismuth alloy to lithium iron phosphate (LFP) materials through both lattice doping and surface coating. The first alloy, doped within the lattice, effectively broadens lithium-ion migration channels, improves electronic conductivity, and stabilizes the crystal structure. The second alloy, coated on the particle surface, constructs a highly conductive and chemically stable interface layer, significantly suppressing side reactions between the cathode and electrolyte and reducing interfacial impedance. The indium tin bismuth alloy combines a low melting point, high conductivity, and good lithium compatibility. It forms an electron-ion synergistic conduction network within the lattice and an alloy-like buffer layer on the surface, synergistically addressing the inherent key technical bottlenecks of LFP materials, such as poor electronic conductivity, slow lithium-ion diffusion rate, and interfacial instability during cycling. Furthermore, this structural design eliminates the need for additional carbon coating or metal oxide modification, simplifying the process. Simultaneously, it forms a matched interface system with the Li-In alloy anode, achieving efficient charge transport and long-term cycle stability in the entire battery system, significantly improving the battery's energy density, power performance, and cycle life.

[0028] In some embodiments of this application, the mass ratio of the first alloy to the second alloy is 30%~50%:50%~70%.

[0029] In this embodiment, by doping the lithium iron phosphate lattice with an indium tin bismuth alloy at a ratio of 30% to 50%, the lithium-ion transport channels are effectively broadened and the lattice distortion energy barrier is reduced, thereby significantly improving the ion diffusion rate. At the same time, coating the lithium iron phosphate particles with an indium tin bismuth alloy at a ratio of 50% to 70% constructs a continuous, highly conductive metal alloy network, which greatly enhances the electron conduction efficiency and inhibits the erosion of the positive electrode interface by the electrolyte, thus improving the interface stability. This specific mass ratio range achieves the synergistic effect of optimizing carrier transport within the crystal and constructing a conductive protective layer on the surface, reducing the risk of lattice structure instability due to excessively high doping ratios or excessively thick coatings that hinder lithium-ion insertion and extraction.

[0030] In some embodiments of this application, the total mass of the first alloy and the second alloy accounts for 2.5 to 3.5% of the mass of the modified lithium iron phosphate material.

[0031] In this embodiment, by limiting the total mass of the first alloy and the second alloy to a range exceeding the mass of the modified lithium iron phosphate material, the synergistic effect of the indium tin bismuth alloy in both lattice doping and surface coating is further balanced: the first alloy doped within the lattice effectively broadens the electronic conductivity channels of lithium iron phosphate and reduces the lithium-ion diffusion barrier, while the second alloy coated on the surface forms a stable and flexible ion-electron hybrid conductive interface layer, alleviating volume strain during charging and discharging and suppressing side reactions; this mass ratio range is the minimum effective threshold for achieving a synergistic improvement in conductive network continuity, interface stability, and ion transport efficiency. Below this lower limit, sufficient modified channels cannot be formed, while above this upper limit, the proportion of active material is too low, structural collapse occurs, or interface impedance increases. Thus, a balance between high rate performance, long cycle life, and excellent interface compatibility is achieved in the solid-state battery system, significantly improving battery consistency and reproducibility.

[0032] In some embodiments of this application, the mass ratio of In, Sn and Bi elements in the first alloy is 0.37~0.39:0.32~0.34:0.28~0.30; the first alloy includes InBi phase and InSn4 phase, and the mass ratio of InBi phase to InSn4 phase is 29:33~50:50.

[0033] In this embodiment, the mass ratio of In, Sn, and Bi elements in the first alloy is strictly limited to the above range. This range has been experimentally verified to precisely control the phase precipitation behavior of the alloy during the lithium iron phosphate lattice doping process, promoting the formation of a two-phase structure dominated by the InBi and InSn4 phases. The InBi phase provides a Li3Bi transport channel with high ionic conductivity, while the InSn4 phase effectively enhances the electronic conductivity network and buffers the volume stress during the charging and discharging process. The first alloy is a low-melting-point soft metal alloy InSnBi, composed of the InBi and InSn4 two-phase structure, which has a unique mixed ion-electron conductivity network. Its lithiation product Li3Bi has high ionic conductivity and can construct an efficient ion transport channel, while the soft phase characteristics can alleviate cyclic stress. When the mass ratio of the two phases is within the above range, they work together to construct a stable and continuous mixed ion-electron conductive framework, significantly improving the lithium-ion diffusion rate and interfacial charge transfer capability, while suppressing lattice distortion and particle pulverization during cycling. With the help of the two-phase structure and conductivity of the InSnBi alloy, the electronic conduction efficiency, ion diffusion rate and interfacial stability of LFP are synergistically improved, achieving comprehensive performance optimization of high power, long cycle life and wide temperature range.

[0034] In some embodiments of this application, the mass ratio of In, Sn and Bi elements in the second alloy is 0.37~0.39:0.32~0.34:0.28~0.30; the second alloy includes InBi phase and InSn4 phase, and the mass ratio of InBi phase to InSn4 phase is 29:33~50:50.

[0035] In this embodiment, the mass ratio of indium, tin, and bismuth in the second alloy is strictly limited to the aforementioned ratio. This optimized ratio promotes the preferential formation of the Li3Bi phase with high ionic conductivity during lithiation, thereby constructing a continuous and stable lithium-ion transport channel on the lithium iron phosphate surface. Simultaneously, the coexistence structure of the InBi and InSn4 phases in the second alloy forms a soft-hard synergistic dual-phase interface. The InBi phase provides excellent plastic deformation capability to buffer volume stress during cycling, while the InSn4 phase enhances structural stability and inhibits the agglomeration and pulverization of alloy particles. The reasonable control of their mass ratio further optimizes stress distribution and interfacial adhesion, significantly improving the long-term cycling stability and kinetic performance of the electrode / electrolyte interface, ultimately achieving a synergistic improvement in the electronic conductivity, ion diffusion rate, and interfacial stability of the lithium iron phosphate cathode material.

[0036] In another typical embodiment of this application, a method for preparing the aforementioned battery cell is provided, including preparing a positive electrode material and preparing a positive electrode sheet including the positive electrode material, and sequentially stacking and assembling the positive electrode sheet, a composite electrolyte sheet, and a Li-In alloy negative electrode to obtain a battery cell. The positive electrode material includes a modified lithium iron phosphate material, such as... Figure 1 As shown, the preparation method of modified lithium iron phosphate material includes: step S1, mixing raw materials including lithium source, iron source, phosphorus source, solvent and indium tin bismuth alloy and drying them to obtain a precursor; step S2, sintering the precursor in a first inert atmosphere to obtain modified lithium iron phosphate material.

[0037] This application achieves controllable doping and uniform surface coating of the indium tin bismuth alloy within the lithium iron phosphate (LFP) lattice by preparing a precursor through a mixture of lithium, iron, and phosphorus sources with an indium tin bismuth alloy, followed by drying and sintering under an inert atmosphere. This method utilizes the partial incorporation of low-temperature melt-prepared InSnBi alloy powder (containing both InBi and InSn4 phases) into the LFP lattice during sintering, improving lithium-ion diffusion kinetics. Simultaneously, the remaining portion forms a continuous conductive network on the particle surface, enhancing electron transport efficiency and stabilizing the solid-solid interface. When the resulting modified material is assembled with a LiPSCl:LiPO3 composite electrolyte and a Li-In anode, it effectively reduces interfacial impedance, increases ion transport number, and alleviates volumetric stress during cycling, thereby improving the rate performance and cycle stability of the battery over a wide temperature range. This method is suitable for the large-scale fabrication of high-safety, high-energy-density solid-state lithium-ion batteries.

[0038] In some embodiments of this application, step S1 includes: mixing raw materials including lithium source, iron source, phosphorus source and solvent to obtain slurry; mixing the slurry with indium tin bismuth alloy and drying it to obtain precursor; wherein the mass of indium tin bismuth alloy is 2.5~3.5% of the mass of slurry; and / or the average particle size of indium tin bismuth alloy is 50~100nm.

[0039] This application employs indium tin bismuth alloy powder with an average particle size of 50-100 nm, which is uniformly compounded with a mixture of lithium, iron, and phosphorus sources at a ratio of 2.5-3.5% by mass of the slurry. After drying, a precursor is formed. This particle size range facilitates uniform dispersion of the alloy powder in the slurry, reducing the risk of localized uneven concentration caused by agglomeration. This, in turn, promotes appropriate doping of alloying elements within the lithium iron phosphate lattice and the formation of a continuous and dense coating layer on the surface during subsequent sintering. This preparation method, by precisely controlling the amount and particle size of the alloy added, effectively improves the electronic conductivity and lithium-ion diffusion rate of the cathode material, enhances interface stability, and provides a foundation for modified lithium iron phosphate cathode materials with uniform structure and stable electrochemical performance for subsequent solid-state battery assembly.

[0040] In some embodiments of this application, the preparation process of indium-tin-bismuth alloy includes: melting and ball milling raw materials including In powder, Sn powder and Bi powder in an atomic ratio under a second inert atmosphere to obtain indium-tin-bismuth alloy, wherein the melting temperature is 150~200℃ and the melting time is 30~60min; and / or, the second inert atmosphere is selected from any one or more of Ar, N2 and He.

[0041] This application obtains uniformly sized biphase alloy powder by controlling the above conditions. These process conditions effectively reduce the risks of high-temperature oxidation and component volatilization, and promote the stable formation of InBi and InSn4 phases. The resulting alloy has both a low melting point and good thermal stability. Its micro-nano-scale biphase structure can be uniformly dispersed in the material lattice and surface when used for subsequent modification of lithium iron phosphate, synergistically improving the construction efficiency of electronic conductivity network and ion transport channel. At the same time, the low-temperature melting and rapid cooling process simplifies the preparation process, reduces energy consumption and equipment requirements, and is conducive to large-scale production and process consistency control.

[0042] In some embodiments of this application, in step S1, the first inert atmosphere is selected from any one or more of Ar, N2 and He; and / or, the lithium source is selected from one or more of Li2CO3, LiOH, LiNO3, LiCH3COO, and LiH2PO4; and / or, the iron source is selected from one or more of FeC2O4·2H2O, Fe2O3, Fe3O4, Fe(NO3)3, and FeSO4; and / or, the phosphorus source is selected from one or more of (NH4)2HPO4, NH4H2PO4, H3PO4, LiH2PO4, and P2O5; and / or, the solvent is selected from any one or more of water, ethanol, ethylene glycol, and NMP.

[0043] The first inert atmosphere uses inert gases such as Ar and N2, or combinations thereof, which effectively reduces the risk of oxidation of the precursor and alloy powder during high-temperature processing, improving the integrity and activity of the InSnBi alloy structure. The lithium, iron, and phosphorus sources can be flexibly matched according to process conditions, allowing for precise control of the stoichiometry of lithium, iron, and phosphorus elements, promoting the high-purity formation of the LFP crystal phase. The solvent used is deionized water or other polar solvents, which helps to uniformly disperse the precursor slurry, improving the uniformity of InSnBi alloy coating on the LFP particle surface and the stability of lattice doping. The rational selection of the above materials and process parameters synergistically ensures the structural integrity, continuity of the ion conduction path, and interfacial compatibility of the modified LFP material, providing a reliable foundation for the high-rate performance, long cycle life, and low-temperature adaptability of subsequent solid-state batteries.

[0044] In some embodiments of this application, in step S1, ultrasonication is performed during the mixing process, with an ultrasonic frequency of 20~80kHz and an ultrasonic time of 1.5~2.5h; and / or, the drying temperature is 70~90℃ and the drying time is 10~14h.

[0045] The above ultrasonic conditions can effectively promote the uniform dispersion of InSnBi alloy powder in the slurry, reduce the risk of agglomeration, and improve the synergy of subsequent lattice doping and surface coating. At the same time, controlling the drying temperature and time within the above range can fully remove solvents and volatile impurities, maintain the stability of the precursor chemical composition, and reduce the probability of lattice distortion or side reactions during sintering caused by residual moisture. This improves the structural integrity and electrochemical performance consistency of the modified lithium iron phosphate material, and enhances the rate performance and cycle stability of the cathode material.

[0046] In some embodiments of this application, step S2 includes a first sintering and a second sintering performed sequentially, wherein the temperature of the second sintering is higher than that of the first sintering; and / or, the temperature of the first sintering is 300~400℃ and the time of the first sintering is 2~3h; and / or, the temperature of the second sintering is 650~750℃ and the time of the second sintering is 5~7h.

[0047] The sintering process of this application is carried out in two stages. The first sintering can effectively remove moisture, organic residues and volatile impurities from the precursor, reducing the risk of structural cracking or particle agglomeration caused by sudden gas release during the subsequent high-temperature sintering process. The second sintering can promote the full crystallization and densification of the lithium iron phosphate crystal phase, while promoting the uniform doping of InSnBi alloy in the lattice and achieving the stable formation of the surface coating layer. The two-step temperature control synergistically optimizes the crystal integrity and interfacial bonding strength of the material, which helps to improve the electronic conductivity and lithium-ion transport efficiency of the cathode material, thereby enhancing the cycle stability and rate performance of the solid-state battery under high rate and wide temperature range conditions.

[0048] In some embodiments of this application, the preparation method further includes a process for preparing a composite electrolyte sheet, which includes: mixing raw materials including LiPSCl, LiPO3 and an organic solvent, and then grinding and calcining them sequentially to obtain a composite electrolyte; wherein the mass ratio of LiPSCl to LiPO3 is 7:3 to 8:2; and / or, the organic solvent is selected from any one or more of ethanol, ethylene glycol and NMP.

[0049] The control of the above organic solvents, grinding, and calcination is beneficial to achieving uniform composite and dense sintering of the two sulfur-phosphorus-based electrolytes, significantly improving ionic conductivity and interfacial stability. Among them, the introduction of LiPO3 effectively suppresses the tendency of sulfur precipitation in LiPSCl during long-term cycling, enhancing the chemical stability of the electrolyte. The above low-boiling-point organic solvents can promote slurry dispersion and reduce residual organic matter, which is beneficial to obtaining a dense and crack-free electrolyte membrane. When this electrolyte is matched with InSnBi modified LFP cathode and Li-In anode, it can reduce interfacial impedance and improve the cycle performance and rate characteristics of solid-state batteries in a wide temperature range.

[0050] In some embodiments of this application, calcination is carried out in a third inert atmosphere, which is selected from any one or more of Ar, N2 and He; and / or, the calcination temperature is 500~600°C and the calcination time is 3~4h.

[0051] The calcination step is carried out in an inert atmosphere such as argon, which can effectively reduce the risk of oxidation or lithium loss of the cathode material during high-temperature heat treatment, thereby improving the integrity and chemical stability of the lithium iron phosphate crystal phase. At the same time, controlling the calcination temperature and time within the above range can suppress the excessive diffusion and agglomeration of InSnBi alloy components while fully removing residual organic matter and moisture in the precursor, maintaining the uniformity of its distribution in lattice doping and surface coating, which helps to form a stable core-shell structure.

[0052] Furthermore, the preferred modified lithium iron phosphate material has the chemical formula LiFe. 1-a (InSnBi)a PO4@In x Sn y Bi z , where 0<a≤0.02, x is 0.37~0.39, y is 0.32~0.34, and z is 0.28~0.30.

[0053] In another typical embodiment of this application, a battery device is provided, which includes the aforementioned battery cell, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0054] Battery devices, including the aforementioned individual battery cells, have superior overall performance in terms of high power output, wide temperature range operation, and long cycle life, making them suitable for energy storage systems and power battery applications with high requirements for energy density, safety, and reliability.

[0055] In yet another typical embodiment of this application, an electrical device is provided, which includes the aforementioned battery device for providing electrical energy.

[0056] The aforementioned battery devices enable them to have higher energy efficiency, longer service life and more stable power output characteristics, making them suitable for energy storage systems and electric vehicle applications with stringent requirements for safety and cycle performance.

[0057] In yet another typical embodiment of this application, an energy storage device is provided, which includes the aforementioned battery device for storing electrical energy.

[0058] Energy storage devices including the aforementioned battery devices can effectively reduce interface impedance, suppress dendrite growth, and improve the cycle life and rate performance of batteries in a wide temperature range environment. They are suitable for energy storage systems with comprehensive requirements for energy density, safety and low temperature adaptability, and are especially suitable for high-reliability energy storage application scenarios under solid-state battery architecture.

[0059] Furthermore, the InSnBi alloy-modified lithium iron phosphate cathode material prepared in this application not only significantly improves the electrochemical performance of lithium-ion batteries under high-rate and low-temperature environments, but is also more suitable for long-term energy storage system requirements. This material possesses high volumetric energy density and excellent cycle stability (capacity retention >85% after >10,000 cycles), efficiently supporting the operation of large-scale energy storage power stations at 4-hour (4h) and 8-hour (8h) levels, meeting the stringent requirements for high-capacity batteries in application scenarios such as grid peak shaving and smooth output of renewable energy.

[0060] The beneficial effects of this application will be explained below with reference to specific embodiments and comparative examples.

[0061] Example 1

[0062] Preparation of InSnBi alloy powder:

[0063] In powder, Sn powder, and Bi powder were weighed according to the atomic ratio In0.38Sn0.33Bi0.29 and placed in an Ar atmosphere furnace. They were melted at 180℃ for 50 min, rapidly cooled, and then ball-milled to a particle size of 80 nm to obtain InSnBi powder (containing InBi and InSn4) biphase, with a mass ratio of 50:50.

[0064] Preparation of InSnBi modified LFP precursor:

[0065] Weigh 1 mol Li2CO3, 0.98 mol FeC2O4·2H2O, and 1 mol (NH4)2HPO4 and add them to deionized water to make a slurry. Add 3% InSnBi alloy powder of the total mass of the slurry, sonicate at a frequency of 60 kHz, sonicate for 2.5 h, vacuum dry at 90 ℃ for 14 h, and grind evenly to obtain the precursor.

[0066] Preparation of modified LFP by sintering: The precursor was placed in an Ar atmosphere furnace and sintered at 350℃ for 3 h to remove impurities and moisture. The temperature was then raised to 700℃ and calcined for 7 h. After cooling, the mixture was ground and sieved to obtain LiFe. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0067] Example 2

[0068] The difference from Example 1 is that 1 mol of Li₂CO₃, 0.98 mol of FeC₂O₄·2H₂O, and 1 mol of (NH₄)₂HPO₄ were weighed and added to deionized water to prepare a slurry. Then, 2.5% of InSnBi alloy powder was added to the slurry to obtain the precursor; finally, LiFe was obtained. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0069] Example 3

[0070] The difference from Example 1 is that 1 mol of Li₂CO₃, 0.98 mol of FeC₂O₄·2H₂O, and 1 mol of (NH₄)₂HPO₄ were weighed and added to deionized water to prepare a slurry. Then, 3.5% of InSnBi alloy powder was added to the slurry to obtain the precursor; finally, LiFe was obtained. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0071] Example 4

[0072] The difference from Example 1 is that 1 mol of Li₂CO₃, 0.98 mol of FeC₂O₄·2H₂O, and 1 mol of (NH₄)₂HPO₄ were weighed and added to deionized water to prepare a slurry. Then, 2.0% of InSnBi alloy powder was added to the slurry to obtain the precursor; finally, LiFe was obtained. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0073] Example 5

[0074] The difference from Example 1 is that the modified LFP was prepared by sintering: the precursor was placed in an Ar atmosphere furnace and sintered at 400°C for 3 hours to remove impurities and moisture, then heated to 750°C and calcined for 7 hours. After cooling, it was ground and sieved to obtain LiFe. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0075] Example 6

[0076] The difference from Example 1 is that the modified LFP was prepared by sintering: the precursor was placed in an Ar atmosphere furnace and sintered at 650°C for 3 hours to remove impurities and moisture, then calcined at 650°C for 7 hours, cooled, ground, and sieved to obtain LiFe. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33Bi 0.29 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0077] Example 7

[0078] The difference from Example 1 is that, according to the atomic ratio In0.39Sn0.33Bi0.28, In powder, Sn powder, and Bi powder were weighed and placed in an Ar atmosphere furnace, melted at 180°C for 50 min, rapidly cooled, and then ball-milled to a particle size of 80 nm to obtain InSnBi powder (containing InBi and InSn4) biphase, with a mass ratio of 29:33; finally, LiFe was obtained. 0.98 (InSnBi) 0.02 PO4@In 0.39 Sn 0.33 Bi 0.28 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0079] Example 8

[0080] The difference from Example 1 is that, according to the atomic ratio In0.36Sn0.30Bi0.34, In powder, Sn powder, and Bi powder were weighed and placed in an Ar atmosphere furnace, melted at 180°C for 50 min, rapidly cooled, and then ball-milled to a particle size of 80 nm to obtain InSnBi powder (containing InBi and InSn4) biphase, with a mass ratio of 25:30; finally, LiFe was obtained. 0.98 (InSnBi) 0.02 PO4@In 0.36 Sn 0.30 Bi 0.34 Modified material; wherein the mass ratio of indium tin bismuth alloy doped in the lattice of lithium iron phosphate to coated on the surface of lithium iron phosphate is 40%:60%.

[0081] Example 9

[0082] The difference from Example 1 is that, by changing the doping amount and surface coating amount of the InSnBi alloy within the LFP lattice, LiFe was ultimately obtained. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 The modified material contains an indium tin bismuth alloy doped within the lattice of lithium iron phosphate and coated on the surface of lithium iron phosphate in a mass ratio of 30%:70%.

[0083] Example 10

[0084] The difference from Example 1 is that the doping amount and surface coating amount of the InSnBi alloy in the LFP lattice were controlled by changing the ultrasonic dispersion time and sintering heating rate of the InSnBi alloy powder, ultimately obtaining LiFe. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 The modified material contains an indium tin bismuth alloy doped within the lattice of lithium iron phosphate and coated on the surface of lithium iron phosphate in a mass ratio of 50%:50%.

[0085] Example 11

[0086] The difference from Example 1 is that the doping amount and surface coating amount of the InSnBi alloy in the LFP lattice were controlled by changing the ultrasonic dispersion time and sintering heating rate of the InSnBi alloy powder, ultimately obtaining LiFe. 0.98 (InSnBi) 0.02 PO4@In 0.38 Sn 0.33 Bi 0.29 The modified material contains an indium tin bismuth alloy doped within the lithium iron phosphate lattice and coated on the surface of the lithium iron phosphate in a mass ratio of 25%:75%.

[0087] Comparative Example 1

[0088] The difference from Example 1 is that In powder and Sn powder were weighed according to the atomic ratio of In0.55Sn0.55 and placed in an Ar atmosphere furnace. They were melted at 180°C for 50 minutes, rapidly cooled, and then ball-milled to a particle size of 80nm to obtain InSn powder; finally, lithium iron phosphate modified material was obtained.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that Sn powder and Bi powder were weighed according to the atomic ratio of Sn0.55Bi0.55 and placed in an Ar atmosphere furnace. They were melted at 180°C for 50 minutes, rapidly cooled, and then ball-milled to a particle size of 80 nm to obtain SnBi powder. Finally, lithium iron phosphate modified material was obtained.

[0091] Comparative Example 3

[0092] The difference from Example 1 is that In powder and Bi powder were weighed according to the atomic ratio of In0.55Bi0.55 and placed in an Ar atmosphere furnace. They were melted at 180°C for 50 minutes, rapidly cooled, and then ball-milled to a particle size of 80 nm to obtain InBi powder. Finally, lithium iron phosphate modified material was obtained.

[0093] Preparation of the positive electrode sheet: The lithium iron phosphate modified materials of the above examples and comparative examples were used as positive electrode active materials, and mixed according to the ratio of positive electrode active material: conductive agent: binder = 8:1:1. A small amount of N-methylpyrrolidone solvent was added and the mixture was ground evenly in agate to form a positive electrode slurry. The slurry was coated on the surface of an aluminum foil current collector and prepared by vacuum drying at 120°C for 12 hours in a vacuum oven.

[0094] Preparation of composite electrolyte and battery assembly: LiPSCl:LiPO3 was mixed at a mass ratio of 8:2, a small amount of anhydrous ethanol was added and ground evenly, and sintered at 600℃ in an inert atmosphere for 4h to obtain composite electrolyte. Li-In alloy was used as negative electrode. The positive electrode, composite electrolyte sheet and Li-In alloy negative electrode were stacked and assembled in sequence to obtain solid-state battery.

[0095] The solid-state batteries assembled in the above embodiments and comparative examples were tested under the conditions of 25°C and 0.5C charge / discharge rate to determine the cycle capacity retention, IC charging capacity, and cycle life performance. The test results are listed in Table 1.

[0096] Table 1

[0097]

[0098] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0099] This application applies an indium tin bismuth alloy to lithium iron phosphate (LFP) materials through both lattice doping and surface coating. The first alloy, doped within the lattice, effectively broadens lithium-ion migration channels, improves electronic conductivity, and stabilizes the crystal structure. The second alloy, coated on the particle surface, constructs a highly conductive and chemically stable interface layer, significantly suppressing side reactions between the cathode and electrolyte and reducing interfacial impedance. The indium tin bismuth alloy combines a low melting point, high conductivity, and good lithium compatibility. It forms an electron-ion synergistic conduction network within the lattice and an alloy-like buffer layer on the surface, synergistically addressing the inherent key technical bottlenecks of LFP materials, such as poor electronic conductivity, slow lithium-ion diffusion rate, and interfacial instability during cycling. Furthermore, this structural design eliminates the need for additional carbon coating or metal oxide modification, simplifying the process. Simultaneously, it forms a matched interface system with the Li-In alloy anode, achieving efficient charge transport and long-term cycle stability in the entire battery system, significantly improving the battery's energy density, power performance, and cycle life.

[0100] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode sheet, a composite electrolyte sheet, and a Li-In alloy negative electrode. The positive electrode sheet includes a positive electrode material, which includes a modified lithium iron phosphate material. The modified lithium iron phosphate material includes lithium iron phosphate, a first alloy, and a second alloy. The first alloy is doped within the crystal lattice of the lithium iron phosphate, and the second alloy is coated on the surface of the lithium iron phosphate. The first alloy includes an indium tin bismuth alloy, and the second alloy includes an indium tin bismuth alloy.

2. The battery cell according to claim 1, characterized in that, The mass ratio of the first alloy to the second alloy is 30%~50%:50%~70%.

3. The battery cell according to claim 1, characterized in that, The total mass of the first alloy and the second alloy accounts for 2.5 to 3.5% of the mass of the modified lithium iron phosphate material.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The mass ratio of In, Sn and Bi in the first alloy is 0.37~0.39:0.32~0.34:0.28~0.30; the first alloy includes InBi phase and InSn4 phase, and the mass ratio of InBi phase to InSn4 phase is 29:33~50:

50.

5. The battery cell according to any one of claims 1 to 3, characterized in that, The mass ratio of In, Sn and Bi in the second alloy is 0.37~0.39:0.32~0.34:0.28~0.30; the second alloy includes InBi phase and InSn4 phase, and the mass ratio of InBi phase to InSn4 phase is 29:33~50:

50.

6. A method for preparing a battery cell according to any one of claims 1 to 5, comprising preparing a positive electrode material and preparing a positive electrode sheet including the positive electrode material, and sequentially stacking and assembling the positive electrode sheet, a composite electrolyte sheet, and a Li-In alloy negative electrode to obtain the battery cell, characterized in that, The cathode material includes a modified lithium iron phosphate material, and the preparation method of the modified lithium iron phosphate material includes: Step S1: Mix the raw materials including lithium source, iron source, phosphorus source, solvent and indium tin bismuth alloy and dry them to obtain the precursor; Step S2: The precursor is sintered in a first inert atmosphere to obtain the modified lithium iron phosphate material.

7. The method for preparing a battery cell according to claim 6, characterized in that, Step S1 includes: A slurry is obtained by mixing raw materials including the lithium source, the iron source, the phosphorus source, and the solvent. The slurry is mixed with the indium tin bismuth alloy and then dried to obtain the precursor. The mass of the indium-tin-bismuth alloy is 2.5-3.5% of the mass of the slurry; And / or, the average particle size of the indium-tin-bismuth alloy is 50~100nm.

8. The method for preparing a single battery cell according to claim 6, characterized in that, The preparation process of the indium-tin-bismuth alloy includes: In a second inert atmosphere, raw materials including In powder, Sn powder and Bi powder are melted and ball-milled according to atomic ratio to obtain the indium-tin-bismuth alloy, wherein the melting temperature is 150~200℃ and the melting time is 30~60min; And / or, the second inert atmosphere is selected from any one or more of Ar, N2 and He.

9. The method for preparing a battery cell according to claim 6, characterized in that, In step S1, the first inert atmosphere is selected from any one or more of Ar, N2 and He; And / or, the lithium source is selected from one or more of Li2CO3, LiOH, LiNO3, LiCH3COO, and LiH2PO4; And / or, the iron source is selected from one or more of FeC2O4·2H2O, Fe2O3, Fe3O4, Fe(NO3)3, and FeSO4; And / or, the phosphorus source is selected from one or more of (NH4)2HPO4, NH4H2PO4, H3PO4, LiH2PO4, and P2O5; And / or, the solvent is selected from any one or more of water, ethanol, ethylene glycol and NMP.

10. The method for preparing a battery cell according to claim 6, characterized in that, In step S1, ultrasound is performed during the mixing process. The frequency of the ultrasound is 20~80kHz, and the duration of the ultrasound is 1.5~2.5h. And / or, the drying temperature is 70~90℃, and the drying time is 10~14h.

11. The method for preparing a battery cell according to claim 6, characterized in that, In step S2, the sintering includes a first sintering and a second sintering performed sequentially, wherein the temperature of the second sintering is higher than the temperature of the first sintering. And / or, the temperature of the first sintering is 300~400℃, and the time of the first sintering is 2~3h; And / or, the second sintering temperature is 650~750℃, and the second sintering time is 5~7h.

12. The method for preparing a battery cell according to claim 6, characterized in that, The preparation method further includes the preparation process of the composite electrolyte sheet, the preparation process including: The composite electrolyte is obtained by mixing raw materials including LiPSCl, LiPO3 and organic solvent, followed by grinding and calcination. The mass ratio of LiPSCl to LiPO3 is 7:3 to 8:

2. And / or, the organic solvent is selected from any one or more of ethanol, ethylene glycol and NMP.

13. The method for preparing a single battery cell according to claim 12, characterized in that, The calcination is carried out in a third inert atmosphere, which is selected from any one or more of Ar, N2 and He; And / or, the calcination temperature is 500~600℃, and the calcination time is 3~4h.

14. A battery device, characterized in that, The battery device includes the battery cell according to any one of claims 1 to 5, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

15. An electrical appliance, characterized in that, The electrical device includes the battery device of claim 14, the battery device being used to provide electrical energy.

16. An energy storage device, characterized in that, The energy storage device includes the battery device of claim 14, the battery device being used to store electrical energy.

Images