Phosphorus-based composite negative electrode material, preparation method and battery

Abstract

The invention relates to a phosphorus-based composite negative electrode material, a preparation method and a battery. The phosphorus-based composite negative electrode material comprises a phosphorus-based negative electrode core and a tin phosphate coating layer coating the phosphorus-based negative electrode core. The tin phosphate coating layer is compact and continuous and can form a physical barrier on the surface of the phosphorus-based negative electrode core to prevent direct contact of oxygen, so that surface oxidation is slowed down or even blocked; the tin phosphate is reduced into metallic tin in the charging process, the conductivity is good, the generated phosphate and fluoride salt double-layer SEI film forms a continuous conductive network, the interface resistance is reduced through the cooperation of the phosphate and the fluoride salt double-layer SEI film, and the overall conductivity is improved; in addition, the double-layer SEI film can buffer volume expansion stress generated in the charging and discharging process, and the cycle life is prolonged; and the preparation method is simple to operate, reduces energy consumption and cost, is convenient for batch production, and provides an efficient, economical and practical technical scheme for surface coating modification.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology and relates to a negative electrode material, particularly a phosphorus-based composite negative electrode material, its preparation method, and a battery. Background Technology

[0002] The requirements for energy density, cycle life, and safety of anode materials in secondary lithium batteries are constantly increasing. Phosphorus-based anode materials, especially red phosphorus, have become promising materials for the "post-lithium" era due to their theoretical capacity of 2596 mAh / g. However, red phosphorus has a room temperature conductivity of only 10. -14 Its capacity decays rapidly, especially at high rates or high temperatures, and its surface is prone to oxidation. Modification methods such as carbon coating and nano-sizing are difficult to maintain stability in complex electrochemical environments for a long time.

[0003] Traditional modifications to phosphorus-based anode materials revolve around a synergistic strategy of "size-composition-interface," including nano-sizing, elemental doping, carbon-based composites, coating modification, and functionalized frameworks, aiming to overcome the problems of poor conductivity and volume expansion. However, most of these methods do not specifically address the oxidation defects of phosphorus-based anode materials and each has its limitations. For example, nano-sizing processes are complex, and carbon-based composites are difficult to simultaneously provide oxidation protection, thus failing to comprehensively optimize performance.

[0004] Coating is crucial for mitigating the oxidation of phosphorus-based anode materials. Traditional coating methods include inorganic coating, organic coating, and inorganic-organic composite coating. Inorganic coating offers high-temperature resistance but suffers from brittleness and poor matrix compatibility; organic coating improves dispersion but has poor high-temperature resistance; composite coating involves multiple steps and is prone to interlayer peeling. These three traditional coating methods are costly and inefficient, making them unsuitable for practical applications. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a phosphorus-based composite anode material, its preparation method and application. The preparation method is simple to operate and can form a uniform coating layer. It effectively solves the problems of complex equipment, high cost, high energy consumption and poor coating modification effect of the existing technology, and provides an efficient, economical and practical technical solution for the surface coating modification of anode materials.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a phosphorus-based composite anode material, the phosphorus-based composite anode material comprising a phosphorus-based anode core and a tin phosphate coating layer covering the phosphorus-based anode core.

[0008] The dense and continuous tin phosphate coating forms a physical barrier on the surface of the phosphorus-based anode core, preventing direct contact with oxygen and thus slowing down or even blocking surface oxidation. During charging, tin phosphate is reduced to metallic tin, which has good conductivity. The resulting phosphate and fluoride bilayer SEI film forms a continuous conductive network, which synergistically reduces the interfacial resistance and improves the overall conductivity. In addition, the bilayer SEI film can buffer the volume expansion stress generated during charging and discharging, extending the cycle life. Moreover, the preparation method is simple to operate, reduces energy consumption and cost, and is easy to mass-produce, providing an efficient, economical and practical technical solution for surface coating modification.

[0009] In some embodiments, the phosphorus-based anode core includes any one or a combination of at least two of red phosphorus, black phosphorus, blue phosphorus, or phosphorus-containing compounds. Typical but non-limiting combinations include combinations of red phosphorus and black phosphorus, combinations of black phosphorus and blue phosphorus, combinations of black phosphorus, blue phosphorus, and phosphorus-containing compounds, or combinations of red phosphorus, black phosphorus, blue phosphorus, and phosphorus-containing compounds.

[0010] Secondly, the present invention provides a method for preparing a phosphorus-based composite anode material, the method comprising the following steps:

[0011] A dispersion was obtained by mixing a phosphorus-based anode core, a tin salt, and an acidic solution.

[0012] The phosphorus source solution and the dispersion are mixed to obtain the first aspect of the phosphorus-based composite anode material.

[0013] The preparation method provided by this invention is a chemical plating method for tin phosphate, which constructs a continuous and dense tin phosphate coating layer in situ on the surface of the phosphorus-based anode core. This tin phosphate coating layer possesses both high conductivity and excellent mechanical elasticity, significantly reducing charge transfer impedance and effectively absorbing stress and inhibiting particle pulverization during charge and discharge, thus greatly improving cycle life. Simultaneously, the dense tin phosphate coating layer has high chemical inertness, maintaining stability under high temperature and strong oxidation conditions, thereby permanently isolating the phosphorus-based anode core from air, significantly suppressing oxidation side reactions, and achieving a synergistic breakthrough in conductivity, structural stability, and air stability.

[0014] In some embodiments, the concentration of the phosphorus-based anode core in the dispersion is 0.1 g / mL to 1 g / mL.

[0015] In some embodiments, the acidic solution includes hydrochloric acid.

[0016] In some embodiments, the pH of the dispersion is 1 to 2.

[0017] In some embodiments, the tin salt includes a water-soluble stannous ion salt.

[0018] In some embodiments, the water-soluble stannous ion salt includes stannous chloride and / or stannous sulfate.

[0019] In some embodiments, Sn in the dispersion 2+ The concentration is 0.1 g / mL to 0.25 g / mL.

[0020] In some embodiments, the phosphorus source in the phosphorus source solution includes sodium dihydrogen phosphate and / or sodium phosphate.

[0021] In some embodiments, the concentration of the phosphorus source in the phosphorus source solution is 0.1 mol / L to 0.3 mol / L.

[0022] In some embodiments, the method of mixing the phosphorus source solution with the dispersion includes: adding the phosphorus source solution to the dispersion at a rate of 5 mL / min to 10 mL / min, while maintaining the pH of the dispersion at 1 to 2 during the addition process.

[0023] In some embodiments, the phosphorus source in the phosphorus source solution and the Sn in the dispersion 2+ The molar ratio is 1:0.9 to 1:1.1.

[0024] In some embodiments, the phosphorus-based anode core is ultrasonically dispersed before being mixed with tin salt and acidic solution to remove the surface oxide layer.

[0025] Thirdly, the present invention provides a battery comprising the phosphorus-based composite anode material described in the first aspect, or the phosphorus-based composite anode material prepared by the preparation method described in the second aspect.

[0026] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The dense and continuous tin phosphate coating can form a physical barrier on the surface of the phosphorus-based anode core, preventing direct contact with oxygen and thus slowing down or even blocking surface oxidation. Tin phosphate is reduced to metallic tin during charging, which has good conductivity. The generated phosphate and fluoride double-layer SEI film constitutes a continuous conductive network. The two work together to reduce the interface resistance and improve the overall conductivity. In addition, the double-layer SEI film can buffer the volume expansion stress generated during charging and discharging, and extend the cycle life. Moreover, the preparation method is simple to operate, reduces energy consumption and cost, and is also easy to mass-produce, providing an efficient, economical and practical technical solution for surface coating modification.

[0029] (2) The preparation method provided by this invention is a chemical plating method for tin phosphate, which constructs a continuous and dense tin phosphate coating layer in situ on the surface of the phosphorus-based anode core. This tin phosphate coating layer has both high conductivity and excellent mechanical elasticity, which can significantly reduce charge transfer impedance and effectively absorb stress and inhibit particle pulverization during charging and discharging, thus greatly improving cycle life. At the same time, the tin phosphate coating layer is dense and chemically inert, and can remain stable under high temperature and strong oxidation conditions, thereby isolating the phosphorus-based anode core from air for a long time, significantly inhibiting oxidation side reactions, and achieving a synergistic breakthrough in conductivity, structural stability and air stability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing sodium intercalation occurring in the phosphorus-based composite anode material of the present invention during discharge. Detailed Implementation

[0031] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0032] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for specific parameters, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this invention, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0033] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0035] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0036] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0038] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0039] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0040] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0041] In this invention, "room temperature" generally refers to 4℃ to 35℃, and may refer to 20℃ ± 5℃. In some embodiments of this invention, room temperature refers to 20℃ to 30℃.

[0042] The rapid iteration of secondary lithium batteries has presented anode materials with three major challenges: higher energy density, longer cycle life, and more stringent safety requirements. Red phosphorus, with its theoretical capacity of 2596 mAh / g, is considered a potential star in the "post-lithium" era, but it has long been hampered by three inherent weaknesses: a room temperature conductivity as low as 10. -14 The surface is prone to oxidation, and the volume expansion during cycling can reach up to 300%, especially under high-rate or high-temperature conditions, the capacity drops rapidly. Although various modification ideas such as carbon coating and nano-sizing have emerged, most of them remain at the "stopgap" level and are difficult to maintain long-term stability in complex electrochemical environments.

[0043] Red phosphorus surface modification can be broadly categorized into three main approaches: inorganic coating, organic coating, and inorganic-organic composite coating. Inorganic methods often utilize chemical deposition or sol-gel to grow ceramic layers such as Al2O3 and SiO2 on the surface of red phosphorus. While this enhances thermal stability, it offers minimal contribution to conductivity and results in significant particle agglomeration. Organic methods typically use phenolic or melamine-formaldehyde resins as shells, achieving coating through in-situ polymerization or interfacial polycondensation. While this improves dispersion and reduces PH3 release, it is prone to moisture absorption, high-temperature decomposition, and even formaldehyde release. Composite methods attempt to combine the advantages of both approaches, but they involve long process chains, significantly increased costs, and high difficulty in mass production. In addition, other auxiliary strategies also have their own limitations: surfactant modification can only fine-tune wettability and has almost no benefit to conductivity and anti-oxidation; hydrothermal synthesis requires reaction at 150℃~200℃ in a high-pressure reactor for more than 20 hours, which has high equipment threshold and high energy consumption; although in-situ polymerization microencapsulation can construct a complete shell, it is accompanied by problems such as lengthy process, organic residues and potential harmful gas escape.

[0044] In addition, to achieve better coating, noble metals are often added to increase the number of surface active sites. For red phosphorus coating, water washing, alcohol washing, and drying are often required to remove impurities. Other coating substrates also often require complex pretreatment of the substrate.

[0045] An embodiment of the present invention provides a phosphorus-based composite anode material, the phosphorus-based composite anode material comprising a phosphorus-based anode core and a tin phosphate coating layer covering the phosphorus-based anode core.

[0046] The tin phosphate coating of phosphorus-based composite anode materials can improve the overall conductivity of the phosphorus-based anode core without sacrificing capacity. Simultaneously, the chemical inertness of Sn3(PO4)2 to water and oxygen significantly inhibits the oxidation of the phosphorus-based anode core, greatly extending storage life. More importantly, the tin phosphate coating exhibits a mechanically "flexible yet rigid" property, providing elastic buffering during the alloying volume expansion of the phosphorus-based composite anode material and maintaining structural integrity during the shrinkage phase, thus effectively suppressing pulverization and significantly improving cycle life. Furthermore, the tin phosphate coating reacts with the electrolyte to form a bilayer SEI film with an inner phosphate-rich layer (e.g., Na3PO4) and an outer fluoride-rich layer (e.g., NaF), possessing both high mechanical strength and fast transport channels, further stabilizing the interface and reducing polarization.

[0047] The dense and continuous tin phosphate coating forms a physical barrier on the surface of the phosphorus-based anode core, preventing direct contact with oxygen and thus slowing down or even blocking surface oxidation. During charging, tin phosphate is reduced to metallic tin, which has good conductivity. The resulting phosphate and fluoride bilayer SEI film forms a continuous conductive network, which synergistically reduces the interfacial resistance and improves the overall conductivity. In addition, the bilayer SEI film can buffer the volume expansion stress generated during charging and discharging, extending the cycle life. Moreover, the preparation method is simple to operate, reduces energy consumption and cost, and is easy to mass-produce, providing an efficient, economical and practical technical solution for surface coating modification.

[0048] In some embodiments, the phosphorus-based negative electrode core includes any one or a combination of at least two of red phosphorus, black phosphorus, blue phosphorus, or phosphorus-containing compounds. Typical but non-limiting combinations include combinations of red phosphorus and black phosphorus, combinations of black phosphorus and blue phosphorus, combinations of black phosphorus, blue phosphorus, and phosphorus-containing compounds, or combinations of red phosphorus, black phosphorus, blue phosphorus, and phosphorus-containing compounds, preferably red phosphorus.

[0049] An embodiment of the present invention provides a method for preparing a phosphorus-based composite anode material, the method comprising the following steps:

[0050] A dispersion was obtained by mixing a phosphorus-based anode core, a tin salt, and an acidic solution.

[0051] By mixing the phosphorus source solution with the dispersion, a phosphorus-based composite anode material of any embodiment can be obtained.

[0052] The theoretical capacity of the phosphorus anode is as high as 2596 mAh / g, but its conductivity at room temperature is only 10. -14 The S / cm and the 300% volume expansion of alloying make it difficult to put into practical use. Although existing carbon coating can partially improve conductivity and buffer volume changes, the carbon layer is unevenly dispersed on the surface of the phosphorus-based anode core and has weak interfacial bonding, failing to fundamentally solve the dual bottlenecks of electron transport and structural stability. In addition, the phosphorus-based anode core is extremely easy to oxidize in air, further hindering its commercialization.

[0053] The preparation method provided by this invention is a chemical plating method for tin phosphate, which constructs a continuous and dense tin phosphate coating layer in situ on the surface of the phosphorus-based anode core. This tin phosphate coating layer possesses both high conductivity and excellent mechanical elasticity, significantly reducing charge transfer impedance and effectively absorbing stress and inhibiting particle pulverization during charge and discharge, thus greatly improving cycle life. Simultaneously, the dense tin phosphate coating layer has high chemical inertness, maintaining stability under high temperature and strong oxidation conditions, thereby permanently isolating the phosphorus-based anode core from air, significantly suppressing oxidation side reactions, and achieving a synergistic breakthrough in conductivity, structural stability, and air stability.

[0054] This invention first constructs a continuous and dense tin phosphate coating layer on the surface of a phosphorus-based anode core through electroless tin phosphate plating. The high conductivity of tin phosphate significantly reduces charge transfer impedance, while the tin phosphate coating layer acts as a physical barrier to isolate oxygen and moisture, greatly improving the storage and processing stability of the phosphorus-based anode core. The tin phosphate coating layer possesses both high elasticity and chemical inertness, effectively absorbing the volumetric stress of the phosphorus-based anode core during charge and discharge, inhibiting particle breakage and electrode structure collapse, thereby significantly extending cycle life. Its dense and stable structure can also continuously block oxygen penetration in high-temperature or strong oxidizing environments, endowing the phosphorus-based anode core with excellent oxidation resistance, achieving a synergistic improvement in conductivity, mechanical stability, and air stability. Simultaneously, the chemical inertness of Sn3(PO4)2 to oxygen and water significantly inhibits the oxidation of the phosphorus-based anode core, greatly extending its storage life. More importantly, this coating layer exhibits a "flexible yet rigid" mechanical property, providing elastic buffering during the volume expansion of red phosphorus alloying and maintaining structural integrity during the shrinkage phase, thereby effectively inhibiting pulverization and significantly improving cycle life compared to uncoated samples. In addition, the double-layer SEI film formed by the side reaction of tin phosphate with electrolyte, consisting of an inner phosphate-rich layer (e.g., Na3PO4) and an outer fluoride-rich layer (e.g., NaF), combines high mechanical strength with fast transport channels, further stabilizing the interface and reducing polarization.

[0055] In some embodiments, the concentration of the phosphorus-based anode core in the dispersion is 0.1 g / mL to 1 g / mL, for example, it can be 0.1 g / mL, 0.3 g / mL, 0.5 g / mL, 0.8 g / mL or 1 g / mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] An appropriate concentration of phosphorus-based anode cores can ensure sufficient dispersion of phosphorus-based anode cores in the dispersion solution.

[0057] In some embodiments, the acidic solution includes hydrochloric acid.

[0058] In some embodiments, the pH of the dispersion is 1 to 2.

[0059] The pH of the dispersion is adjusted by an acidic solution. A suitable pH can inhibit the hydrolysis of tin salt to generate Sn(OH)2 or SnO2·xH2O. Moreover, the acidic solution can etch the surface of the phosphorus-based anode core, roughening its surface and making its bonding with the tin phosphate coating layer tighter.

[0060] In some embodiments, the tin salt includes a water-soluble stannous ion salt.

[0061] In some embodiments, the water-soluble stannous ion salt includes stannous chloride and / or stannous sulfate.

[0062] Stannous chloride can also be a stannous chloride hydrate salt.

[0063] Stannous sulfate can also be a stannous sulfate hydrate.

[0064] Sn in dispersion 2+ If the concentration is too high, it is prone to rapid hydrolysis in areas with increased local pH, forming SnO2·xH2O colloids, leading to impurity contamination and a decrease in the purity of the coating layer; Sn 2+ If the concentration is too low, it will lead to an excessive amount of phosphate adsorbed on the surface, forming an amorphous coating layer, which will affect the subsequent conductivity.

[0065] In some embodiments, Sn in the dispersion 2+ The concentration is 0.1 g / mL to 0.25 g / mL, for example, it can be 0.1 g / mL, 0.15 g / mL, 0.2 g / mL or 0.25 g / mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0066] In some embodiments, the phosphorus source in the phosphorus source solution includes sodium dihydrogen phosphate and / or sodium phosphate.

[0067] In a phosphorus source solution, when the concentration of the phosphorus source is too high, the local supersaturation increases suddenly, and PO4... 3- With Sn 2+ Rapid and massive nucleation can easily lead to the formation of amorphous precipitates, affecting the structural strength of the coating layer; while when the concentration is too low, the nucleation driving force is weak, crystal growth is slow, and the yield is low.

[0068] In some embodiments, the concentration of the phosphorus source in the phosphorus source solution is 0.1 mol / L to 0.3 mol / L, for example, it can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the method of mixing the phosphorus source solution with the dispersion includes: adding the phosphorus source solution to the dispersion at a rate of 5 mL / min to 10 mL / min, while maintaining the pH of the dispersion at 1 to 2 during the addition process.

[0070] In some embodiments, the phosphorus source solution is added to the dispersion by slow injection with a syringe or dripping with a peristaltic pump.

[0071] The rate at which the phosphorus source solution is added to the dispersion keeps the entire system in a state of low supersaturation, preventing explosive nucleation. Specifically, an excessively fast rate will cause a sharp increase in instantaneous supersaturation, with the nucleation rate exceeding the growth rate. This results in a large number of crystal nuclei erupting instantaneously within the system, leading to an uneven coating layer or amorphous particles. Simultaneously, large local pH or concentration gradients can easily induce the formation of secondary phases such as Sn(OH)2, reducing purity. While an excessively low rate can maintain low supersaturation, it prolongs the crystal growth time, making the system more sensitive to impurity ions, dust, or temperature fluctuations, potentially leading to heterogeneous nucleation and the formation of impurity crystals. Furthermore, it also results in increased energy consumption and decreased efficiency.

[0072] Phosphorus source and Sn 2+ The molar ratio needs to be controlled. If the phosphorus source is excessive, it will rapidly increase the local supersaturation, inducing explosive nucleation and resulting in an amorphous coating layer; while if the phosphorus source is insufficient, free Sn will... 2+ Increased concentration makes it easier for impurities to hydrolyze into SnO2·xH2O in regions with pH > 2, affecting the purity of the coating layer.

[0073] In some embodiments, the phosphorus source in the phosphorus source solution and the Sn in the dispersion 2+ The molar ratio is 1:0.9 to 1:1.1, for example, it can be 1:0.9, 1:1 or 1:1.1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] In some embodiments, after mixing the phosphorus source solution with the dispersion, post-treatment is also included.

[0075] The post-processing includes solid-liquid separation to separate the tin phosphate-coated phosphorus-based anode core, followed by washing with deionized water and ethanol to remove residual chemical reagents on the surface, and then drying to obtain the phosphorus-based composite anode material.

[0076] The drying method includes any one or a combination of at least two of the following: vacuum drying, forced air drying, or freeze drying.

[0077] The temperature for vacuum drying and forced-air drying can be between 40℃ and 120℃. Too low a temperature will reduce drying efficiency; if the temperature is too high, without an atmosphere protection, it is easy to react with oxygen in the air and cause oxidation of the phosphorus-based negative electrode core. Moreover, excessively high temperatures will also result in excessive energy consumption and are uneconomical.

[0078] In some embodiments, the protective atmosphere during the drying process includes, but is not limited to, any one or a combination of at least two of nitrogen, argon, or carbon dioxide.

[0079] In some embodiments, the phosphorus-based anode core is ultrasonically dispersed before being mixed with tin salt and acidic solution to remove the surface oxide layer.

[0080] The phosphorus-based composite anode material prepared by the preparation method provided in certain embodiments of the present invention has a median particle size of 0.5 μm to 20 μm for the phosphorus-based anode core and a coating thickness of 0.05 μm to 2 μm.

[0081] An embodiment of the present invention provides a battery comprising the phosphorus-based composite anode material described in any embodiment, or the phosphorus-based composite anode material prepared by the preparation method described in any embodiment.

[0082] The battery in this invention includes a sodium-ion battery or a lithium-ion battery.

[0083] Using a sodium-ion battery as an example, the phosphorus-based composite negative electrode material provided by this invention undergoes sodium intercalation in the tin phosphate coating layer during discharge (see...). Figure 1 ):

[0084] P + 3Na + +3e - →Na3P;

[0085] Sn3(PO4)2+6Na + +6e - →3Sn + 2Na3PO4;

[0086] 4Sn+15Na + +15e - →Na 15 Sn4;

[0087] After sodium intercalation, a sodium phosphate-rich SEI film is formed on the surface. This SEI film has high conductivity, which reduces impedance. In synergy with the subsequently generated NaF-rich film, it ensures the structural stability of the phosphorus-based composite anode material during cycling.

[0088] Example 1

[0089] This embodiment provides a phosphorus-based composite anode material, including a phosphorus-based anode core (red phosphorus) and a tin phosphate coating layer covering the phosphorus-based anode core;

[0090] The preparation method of this phosphorus-based composite anode material includes the following steps:

[0091] S1. Prepare a red phosphorus dispersion with a concentration of 0.5 g / mL, and ultrasonically disperse it for 30 min to ensure uniform dispersion of red phosphorus and remove the surface oxide layer; centrifuge to separate solid and liquid, mix the obtained solid powder with hydrochloric acid, then add stannous chloride and disperse it fully to obtain a dispersion;

[0092] In the dispersion, the concentration of red phosphorus was 0.5 g / mL, the pH value was 1, and Sn... 2+ The concentration was 0.15 g / mL;

[0093] S2. Prepare a phosphorus source solution. The phosphorus source in the phosphorus source solution is sodium dihydrogen phosphate with a concentration of 0.1 mol / L.

[0094] S3. Using a syringe, the phosphorus source solution is slowly added to the dispersion at a rate of 5 mL / min, while maintaining the pH of the dispersion at 1-2. After the reaction is complete, the mixture is poured into a centrifuge to separate the tin phosphate-coated red phosphorus composite material. The material is then washed three times with deionized water and ethanol to remove residual chemical reagents from the surface. The material is then dried in a vacuum drying oven at 40°C for 12 hours to obtain the phosphorus-based composite anode material.

[0095] The amount of phosphorus source solution used is equal to the amount of sodium dihydrogen phosphate and Sn in the dispersion. 2+ The molar ratio is 1:1.

[0096] Example 2

[0097] This embodiment provides a phosphorus-based composite anode material, including a phosphorus-based anode core (red phosphorus) and a tin phosphate coating layer covering the phosphorus-based anode core;

[0098] The preparation method of this phosphorus-based composite anode material includes the following steps:

[0099] S1. Prepare a red phosphorus dispersion with a concentration of 0.1 g / mL, and ultrasonically disperse it for 30 min to ensure uniform dispersion of red phosphorus and remove the surface oxide layer; centrifuge to separate solid and liquid, mix the obtained solid powder with hydrochloric acid, then add SnSO4·2H2O and disperse it fully to obtain a dispersion.

[0100] In the dispersion, the concentration of red phosphorus was 0.1 g / mL, the pH value was 1, and Sn... 2+ The concentration is 0.1 g / mL;

[0101] S2. Prepare a phosphorus source solution. The phosphorus source in the phosphorus source solution is sodium dihydrogen phosphate with a concentration of 0.3 mol / L.

[0102] S3. Using a syringe, the phosphorus source solution is slowly added to the dispersion at a rate of 5 mL / min, while maintaining the pH of the dispersion at 1-2. After the reaction is complete, the mixture is poured into a centrifuge to separate the tin phosphate-coated red phosphorus composite material. The material is then washed three times with deionized water and ethanol to remove residual chemical reagents from the surface. The material is then dried in a vacuum drying oven at 50°C for 12 hours to obtain the phosphorus-based composite anode material.

[0103] The amount of phosphorus source solution used is equal to the amount of sodium dihydrogen phosphate and Sn in the dispersion. 2+ The molar ratio is 1:1.

[0104] Example 3

[0105] This embodiment provides a phosphorus-based composite anode material, including a phosphorus-based anode core (red phosphorus) and a tin phosphate coating layer covering the phosphorus-based anode core;

[0106] The preparation method of this phosphorus-based composite anode material includes the following steps:

[0107] S1. Prepare a red phosphorus dispersion with a concentration of 0.5 g / mL, and ultrasonically disperse it for 30 min to ensure uniform dispersion of red phosphorus and remove the surface oxide layer; centrifuge to separate solid and liquid, mix the obtained solid powder with hydrochloric acid, then add SnSO4·2H2O and disperse it fully to obtain a dispersion.

[0108] In the dispersion, the concentration of red phosphorus was 0.5 g / mL, the pH value was 2, and Sn... 2+ The concentration was 0.2 g / mL;

[0109] S2. Prepare a phosphorus source solution. The phosphorus source in the phosphorus source solution is sodium phosphate with a concentration of 0.2 mol / L.

[0110] S3. Using a syringe, the phosphorus source solution is slowly added to the dispersion at a rate of 8 mL / min, while maintaining the pH of the dispersion at 1-2. After the reaction is complete, the mixture is poured into a centrifuge to separate the tin phosphate-coated red phosphorus composite material. The material is then washed three times with deionized water and ethanol to remove residual chemical reagents from the surface. The material is then dried in a vacuum drying oven at 60°C for 12 hours to obtain the phosphorus-based composite anode material.

[0111] The amount of phosphorus source solution used is equal to the amount of sodium phosphate and Sn in the dispersion. 2+ The molar ratio is 1:1.1.

[0112] Example 4

[0113] This embodiment provides a phosphorus-based composite anode material, including a phosphorus-based anode core (red phosphorus) and a tin phosphate coating layer covering the phosphorus-based anode core;

[0114] The preparation method of this phosphorus-based composite anode material includes the following steps:

[0115] S1. Prepare a red phosphorus dispersion with a concentration of 1 g / mL, and ultrasonically disperse it for 30 min to ensure uniform dispersion of red phosphorus and remove the surface oxide layer; centrifuge to separate solid and liquid, mix the obtained solid powder with hydrochloric acid, then add SnSO4·2H2O and disperse it fully to obtain a dispersion.

[0116] In the dispersion, the concentration of red phosphorus was 1 g / mL, the pH value was 1.5, and Sn... 2+ The concentration was 0.25 g / mL;

[0117] S2. Prepare a phosphorus source solution. The phosphorus source in the phosphorus source solution is sodium dihydrogen phosphate with a concentration of 0.1 mol / L.

[0118] S3. Using a syringe, the phosphorus source solution is slowly added to the dispersion at a rate of 10 mL / min, while maintaining the pH of the dispersion at 1-2. After the reaction is complete, the mixture is poured into a centrifuge to separate the tin phosphate-coated red phosphorus composite material. The material is then washed three times with deionized water and ethanol to remove residual chemical reagents from the surface. The material is then dried in a vacuum drying oven at 80°C for 12 hours to obtain the phosphorus-based composite anode material.

[0119] The amount of phosphorus source solution used is equal to the amount of sodium dihydrogen phosphate and Sn in the dispersion. 2+ The molar ratio is 1:0.9.

[0120] Example 5

[0121] This embodiment provides a phosphorus-based composite anode material, including a phosphorus-based anode core (red phosphorus) and a tin phosphate coating layer covering the phosphorus-based anode core;

[0122] The preparation method of this phosphorus-based composite anode material includes the following steps:

[0123] S1. Prepare a red phosphorus dispersion with a concentration of 0.3 g / mL, and ultrasonically disperse it for 30 min to ensure uniform dispersion of red phosphorus and remove the surface oxide layer; centrifuge to separate solid and liquid, mix the obtained solid powder with hydrochloric acid, then add SnCl2·2H2O and disperse it fully to obtain a dispersion.

[0124] In the dispersion, the concentration of red phosphorus was 0.3 g / mL, the pH value was 1, and Sn... 2+ The concentration was 0.15 g / mL;

[0125] S2. Prepare a phosphorus source solution. The phosphorus source in the phosphorus source solution is sodium dihydrogen phosphate with a concentration of 0.15 mol / L.

[0126] S3. Using a syringe, the phosphorus source solution is slowly added to the dispersion at a rate of 6 mL / min, while maintaining the pH of the dispersion at 1-2. After the reaction is complete, the mixture is poured into a centrifuge to separate the tin phosphate-coated red phosphorus composite material. The material is then washed three times with deionized water and ethanol to remove residual chemical reagents from the surface. The material is then dried in a vacuum drying oven at 100°C for 12 hours to obtain the phosphorus-based composite anode material.

[0127] The amount of phosphorus source solution used is equal to the amount of sodium dihydrogen phosphate and Sn in the dispersion. 2+ The molar ratio is 1:1.

[0128] Example 6

[0129] This embodiment provides a phosphorus-based composite anode material, including a phosphorus-based anode core (red phosphorus) and a tin phosphate coating layer covering the phosphorus-based anode core;

[0130] The preparation method of this phosphorus-based composite anode material includes the following steps:

[0131] S1. Prepare a red phosphorus dispersion with a concentration of 0.7 g / mL, and ultrasonically disperse it for 30 min to ensure uniform dispersion of red phosphorus and remove the surface oxide layer; centrifuge to separate solid and liquid, mix the obtained solid powder with hydrochloric acid, then add SnSO4·2H2O and disperse it fully to obtain a dispersion.

[0132] In the dispersion, the concentration of red phosphorus was 0.7 g / mL, the pH value was 2, and Sn... 2+ The concentration was 0.22 g / mL;

[0133] S2. Prepare a phosphorus source solution. The phosphorus source in the phosphorus source solution is sodium dihydrogen phosphate with a concentration of 0.25 mol / L.

[0134] S3. Using a syringe, the phosphorus source solution is slowly added to the dispersion at a rate of 7 mL / min, while maintaining the pH of the dispersion at 1-2. After the reaction is complete, the mixture is poured into a centrifuge to separate the tin phosphate-coated red phosphorus composite material. The material is then washed three times with deionized water and ethanol to remove residual chemical reagents from the surface. The material is then dried in a vacuum drying oven at 120°C for 12 hours to obtain the phosphorus-based composite anode material.

[0135] The amount of phosphorus source solution used is equal to the amount of sodium dihydrogen phosphate and Sn in the dispersion. 2+ The molar ratio is 1:1.

[0136] Comparative Example 1

[0137] This comparative example provides a negative electrode material, which is the phosphorus-based negative electrode core (red phosphorus) in Example 1.

[0138] Performance Characterization

[0139] The phosphorus-based composite anode material provided in the above embodiments and comparative examples were mixed with binder (CMC) and conductive agent (Super-P) at a mass ratio of 8:1:1 to form a slurry, which was then coated onto copper foil. The resulting anode sheet and sodium sheet (positive electrode sheet) were assembled in a glove box with water and oxygen values ​​both less than 0.01 ppm to obtain a sodium-ion half-cell, and its electrochemical performance was tested. Specifically, the first charge-discharge cycle was performed at a current density of 100 mA / g to obtain the first charge-discharge specific capacity and the first efficiency (first efficiency = first charge specific capacity / first discharge specific capacity). Then, the cells were cycled at a current density of 1000 mA / g, and their cycle performance was compared. The capacity retention rate was calculated as the charge specific capacity after 200 cycles / the charge specific capacity after the first cycle. The results are shown in Table 1.

[0140] Table 1

[0141] First week charging capacity (mAh / g) First-efficacy (%) Capacity retention rate (%) Example 1 2209 85 85 Example 2 1762 82 86 Example 3 1843 84 80 Example 4 1957 83 71 Example 5 2175 79 83 Example 6 1983 86 79 Comparative Example 1 1597 72 62

[0142] Table 1 shows that each embodiment exhibits a higher first-cycle charge specific capacity and first-cycle efficiency than uncoated tin phosphate red phosphorus. This is attributed to the improved conductivity of the coated red phosphorus, which significantly reduces the mass transfer resistance of sodium ions, preventing severe kinetic hindrance. This allows electrons to conduct more efficiently within the electrode, successfully addressing the problem of sluggish electrochemical kinetics caused by the poor conductivity of red phosphorus itself. Consequently, the capacity utilization is higher, resulting in a higher first-cycle efficiency. Furthermore, during charge and discharge, red phosphorus undergoes significant volume changes. The tin phosphate coating can alleviate the stress caused by these volume changes, reducing damage to the electrode structure and thus significantly improving cycle performance.

[0143] In summary, the dense and continuous tin phosphate coating layer forms a physical barrier on the surface of the phosphorus-based anode core, preventing direct contact with oxygen and thus slowing down or even blocking surface oxidation. During charging, tin phosphate is reduced to metallic tin, exhibiting good conductivity. The resulting phosphate and fluoride bilayer SEI film constitutes a continuous conductive network, synergistically reducing interfacial resistance and improving overall conductivity. Furthermore, the bilayer SEI film buffers the volume expansion stress generated during charging and discharging, extending cycle life. Moreover, the preparation method is simple, reducing energy consumption and cost, and facilitating mass production, providing an efficient, economical, and practical technical solution for surface coating modification. The preparation method provided by this invention is a chemical tin phosphate plating method, constructing a continuous and dense tin phosphate coating layer in situ on the surface of the phosphorus-based anode core. This tin phosphate coating layer possesses both high conductivity and excellent mechanical elasticity, significantly reducing charge transfer impedance and effectively absorbing stress and inhibiting particle pulverization during charging and discharging, thus greatly improving cycle life. Meanwhile, the tin phosphate coating is dense and chemically inert, and can remain stable under high temperature and strong oxidation conditions, thus isolating the phosphorus-based anode core from the air for a long time, significantly suppressing oxidation side reactions, and achieving a synergistic breakthrough in conductivity, structural stability and air stability.

[0144] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A phosphorus-based composite anode material, characterized in that, The phosphorus-based composite anode material includes a phosphorus-based anode core and a tin phosphate coating layer covering the phosphorus-based anode core.

2. The phosphorus-based composite anode material according to claim 1, characterized in that, The phosphorus-based anode core includes any one or a combination of at least two of red phosphorus, black phosphorus, blue phosphorus, or phosphorus-containing compounds.

3. A method for preparing a phosphorus-based composite anode material, characterized in that, The preparation method includes the following steps: A dispersion was obtained by mixing a phosphorus-based anode core, a tin salt, and an acidic solution. The phosphorus source solution and the dispersion are mixed to obtain the phosphorus-based composite anode material according to claim 1 or 2.

4. The preparation method according to claim 3, characterized in that, In the dispersion, the concentration of the phosphorus-based anode core is 0.1 g / mL to 1 g / mL.

5. The preparation method according to claim 3 or 4, characterized in that, The acidic solution includes hydrochloric acid; And / or, the pH value of the dispersion is 1 to 2.

6. The preparation method according to any one of claims 3 to 5, characterized in that, The tin salt includes water-soluble stannous ion salts; And / or, the water-soluble stannous ion salt includes stannous chloride and / or stannous sulfate; And / or, Sn in the dispersion 2+ The concentration is 0.1 g / mL to 0.25 g / mL.

7. The preparation method according to any one of claims 3 to 6, characterized in that, The phosphorus source in the phosphorus source solution includes sodium dihydrogen phosphate and / or sodium phosphate; And / or, in the phosphorus source solution, the concentration of the phosphorus source is 0.1 mol / L to 0.3 mol / L.

8. The preparation method according to any one of claims 3 to 7, characterized in that, The method for mixing the phosphorus source solution with the dispersion includes: adding the phosphorus source solution to the dispersion at a rate of 5 mL / min to 10 mL / min, while maintaining the pH of the dispersion at 1 to 2 during the addition process; And / or, the phosphorus source in the phosphorus source solution and the Sn in the dispersion 2+ The molar ratio is 1:0.9 to 1:1.

1.

9. The preparation method according to any one of claims 3 to 8, characterized in that, The phosphorus-based anode core is ultrasonically dispersed before being mixed with tin salt and acidic solution to remove the surface oxide layer.

10. A battery, characterized in that, The battery includes the phosphorus-based composite anode material as described in claim 1 or 2, or the phosphorus-based composite anode material prepared by the preparation method described in any one of claims 3 to 9.

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