Sodium battery negative electrode material of chemically tinned red phosphorus coated sodium battery negative electrode material as well as preparation method and application of sodium battery negative electrode material

Abstract

The invention belongs to the technical field of battery manufacturing, and relates to a sodium battery negative electrode material with red phosphorus coated by chemical tin plating and a preparation method and application thereof, and the sodium battery negative electrode material comprises a red phosphorus core and a chemical tin plating layer coated on the surface of the red phosphorus core. The preparation method comprises the following steps: (1) mixing red phosphorus powder and an acid solution, uniformly dispersing, carrying out solid-liquid separation, washing red phosphorus to be neutral, dispersing in deionized water, adding a stabilizer, and adjusting the pH value to obtain a red phosphorus dispersion liquid; (2) the tin salt solution and the red phosphorus dispersion liquid are mixed, a reducing agent is added for a chemical tinning reaction, and the surface of red phosphorus is evenly coated with metal tin; and (3) carrying out solid-liquid separation on the reaction mixture, and sequentially washing and drying a solid product to obtain the sodium battery negative electrode material with red phosphorus coated by chemical tin plating. The surface of the red phosphorus material is coated with the chemical tin coating, so that volume expansion of the red phosphorus is effectively inhibited, the oxidation resistance and the electronic conductivity of the material are improved, and meanwhile, the processing difficulty and the coating cost are reduced.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and relates to a sodium battery anode material, particularly to a sodium battery anode material with chemically plated tin-coated red phosphorus, its preparation method and application. Background Technology

[0002] Phosphorus-based anodes, as anode materials for sodium-ion batteries, possess a theoretical specific capacity as high as 2596 mAh / g. Red phosphorus is abundant, inexpensive, and readily available, exhibiting moderate chemical stability, thus demonstrating enormous application potential. However, red phosphorus exhibits a high volume expansion rate of up to 300% in electrochemical reactions, while its electronic conductivity is extremely low, only 10⁻⁶. ⁻14 The low S / m ratio of red phosphorus severely hinders its industrial application. Despite these challenges, red phosphorus remains an important research subject in the field of sodium electrochemical materials due to its potential value in terms of safety and practicality.

[0003] Currently, existing methods for modifying red phosphorus mainly include nanostructuring, doping, carbon-based composites, and the construction of functionalized frameworks. However, these methods cannot solve the inherent problems of high volume expansion and low electronic conductivity of red phosphorus, nor can they guarantee the long-term stability of red phosphorus materials in complex battery environments. Coating modification, as an effective method, holds promise for simultaneously addressing the issues of large volume expansion, poor conductivity, and poor air stability of red phosphorus. Therefore, by coating with a layer of highly conductive material, it is possible to simultaneously suppress red phosphorus volume expansion, provide antioxidant protection, and improve electronic conductivity.

[0004] Traditional red phosphorus coating strategies can be broadly categorized into three types: inorganic, organic, and inorganic-organic composites. Existing inorganic coatings mostly employ chemical deposition and sol-gel methods to coat the surface of red phosphorus with hydroxide layers such as aluminum hydroxide and magnesium hydroxide. However, this method is difficult to process, prone to agglomeration during processing, and costly; moreover, the coating layer lacks electrochemical activity. Organic coatings utilize in-situ polymerization and interfacial condensation to coat the surface of red phosphorus with polymer films. However, this method suffers from poor air stability due to the hygroscopic nature of the polymer layer. Inorganic-organic composite coatings attempt to balance rigidity and flexibility, typically using an inorganic layer to provide a dense barrier before covering with an organic layer to improve interfacial compatibility and processing toughness. However, the bilayer, non-chemically active structure increases the total coating volume, dilutes the effective phosphorus content, and reduces the material's specific capacity. Simultaneously, the increased number of process steps leads to poor batch consistency and high energy consumption. More importantly, insufficient interlayer bonding can easily cause delamination during shearing or thermal cycling, resulting in the loss of barrier function.

[0005] Furthermore, while existing carbon coating methods can improve the conductivity of red phosphorus materials and buffer their volume changes to some extent, the carbon layer on the red phosphorus surface suffers from uneven dispersion and weak interfacial bonding, failing to fundamentally overcome the dual bottlenecks of electron transport and structural stability. At the same time, red phosphorus is highly susceptible to oxidation in air, further hindering its commercialization.

[0006] Therefore, how to provide a coating modification method for red phosphorus materials that can effectively suppress the volume expansion of red phosphorus, improve the oxidation resistance and electronic conductivity of the materials, and at the same time reduce the processing difficulty and coating cost has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a sodium electrode anode material with chemically tin-plated red phosphorus coating, its preparation method, and its application, which effectively suppresses the volume expansion of red phosphorus, improves the material's oxidation resistance and electronic conductivity, and reduces processing difficulty and coating cost.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a sodium electrode anode material with chemically plated tin-coated red phosphorus, comprising a red phosphorus core and a chemically plated tin layer coating the surface of the red phosphorus core.

[0010] This invention involves coating the surface of red phosphorus material with a chemically plated tin layer. The high conductivity of metallic tin significantly reduces charge transfer resistance and improves overall conductivity. Simultaneously, the dense and continuous tin layer acts as a physical barrier, effectively isolating oxygen and moisture, thereby slowing down or even blocking the oxidation reaction on the red phosphorus surface, greatly improving the storage and processing stability of the red phosphorus. Due to the good ductility, high elasticity, and chemical inertness of the tin coating, it can effectively absorb the volume expansion stress generated by the red phosphorus during charge and discharge, inhibiting particle breakage and electrode structure collapse, thus significantly extending the battery's cycle life. Furthermore, metallic tin itself possesses electrochemical sodium storage activity and a theoretical specific capacity as high as 847 mAh / g, giving the composite material a high overall energy density, providing additional capacity contribution to the battery compared to traditional coatings.

[0011] Preferably, the average thickness of the chemically plated tin layer is 0.01-2 μm.

[0012] Preferably, the mass ratio of the chemically plated tin layer to the red phosphorus core is 1:(10-100).

[0013] In a second aspect, the present invention provides a method for preparing a sodium-ion electrode material as described in the first aspect, comprising the following steps:

[0014] (1) Mix red phosphorus powder and acid solution, disperse evenly and then separate solid and liquid. Wash red phosphorus until neutral, then disperse it in deionized water, add stabilizer and adjust pH value to obtain red phosphorus dispersion;

[0015] (2) Mix the tin salt solution and the red phosphorus dispersion obtained in step (1), add a reducing agent to carry out a chemical tin plating reaction, and uniformly coat the surface of the red phosphorus with metallic tin;

[0016] (3) The reaction mixture obtained in step (2) is subjected to solid-liquid separation, and the solid product is washed and dried in sequence to obtain sodium electrode material with chemically plated tin and coated red phosphorus.

[0017] The preparation method provided by this invention does not require high temperature and high pressure, has simple equipment requirements, and is easy to operate, thus reducing energy consumption and cost and facilitating mass production. It simultaneously completes red phosphorus surface impurity removal, etching, and chemical tin plating in the same reaction system, eliminating the need for precious metal catalysts compared to traditional tin coating. Furthermore, it can rapidly form a uniform coating layer, effectively solving the problems of complex equipment, high cost, high energy consumption, and limited application of existing technologies, providing a more efficient, economical, and practical innovative solution for material surface coating modification.

[0018] Preferably, the acid solution in step (1) includes hydrochloric acid solution and / or sulfuric acid solution, more preferably hydrochloric acid solution.

[0019] Preferably, the concentration of the acid solution in step (1) is 2-5 wt%.

[0020] Preferably, the solid-liquid ratio of the red phosphorus powder and acid solution in step (1) is 0.1-5 g / mL.

[0021] Preferably, the mixing process in step (1) is accompanied by ultrasonic treatment.

[0022] Preferably, the washing in step (1) uses deionized water.

[0023] Preferably, the stabilizer in step (1) includes polyethylene glycol and / or polyvinylpyrrolidone.

[0024] Preferably, the amount of stabilizer added to the red phosphorus dispersion in step (1) is 0.1-0.5 g / L.

[0025] Preferably, the pH adjustment in step (1) is performed using hydrochloric acid solution and / or sulfuric acid solution, more preferably hydrochloric acid solution.

[0026] Preferably, the pH adjustment endpoint in step (1) is 2-2.5.

[0027] Preferably, the tin salt in the tin salt solution in step (2) includes stannous chloride and / or stannous sulfate.

[0028] Preferably, the concentration of the tin salt solution in step (2) is 10-30 g / L.

[0029] Preferably, the tin salt solution in step (2) also contains a complexing agent, a stabilizer, and a pH adjuster.

[0030] Preferably, the complexing agent comprises citric acid and / or sodium citrate, and the content in the tin salt solution is 5-15 g / L.

[0031] Preferably, the stabilizer comprises thiourea and / or potassium ferrocyanide, in a concentration of 0.05-0.2 g / L in the tin salt solution.

[0032] Preferably, the pH adjuster comprises hydrochloric acid solution and / or sulfuric acid solution, and the pH adjustment endpoint is 1-3.

[0033] Preferably, the reducing agent in step (2) includes sodium hypophosphite.

[0034] Preferably, the amount of reducing agent added to the mixed solution in step (2) is 20-30 g / L.

[0035] Preferably, the molar ratio of the reducing agent to the tin ions in the tin salt solution in step (2) is (1-2):1.

[0036] Preferably, the temperature of the chemical tin plating reaction in step (2) is 30-40℃.

[0037] Preferably, the washing in step (3) uses deionized water.

[0038] Thirdly, the present invention provides a sodium-ion battery anode sheet, comprising at least the sodium-ion battery anode material with chemically plated tin-coated red phosphorus as described in the first aspect.

[0039] Fourthly, the present invention provides a sodium-ion battery comprising at least a sodium-ion anode material with chemically plated tin-coated red phosphorus as described in the first aspect, or a sodium-ion anode sheet as described in the third aspect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) In this invention, a chemically plated tin layer is coated on the surface of red phosphorus material. The high conductivity of metallic tin can significantly reduce charge transfer resistance and improve overall conductivity. At the same time, the dense and continuous tin layer can effectively isolate oxygen and moisture as a physical barrier, thereby slowing down or even blocking the oxidation reaction on the surface of red phosphorus, which greatly improves the storage and processing stability of red phosphorus. Due to the good ductility of the tin coating layer, which has both high elasticity and chemical inertness, it can effectively absorb the volume expansion stress generated by red phosphorus during charging and discharging, inhibit particle breakage and electrode structure collapse, and thus significantly extend the cycle life of the battery. In addition, metallic tin itself has electrochemical sodium storage activity and a theoretical specific capacity of up to 847 mAh / g, which makes the composite material have a high overall energy density. Compared with traditional coating layers, it can provide additional capacity contribution to the battery.

[0042] (2) The preparation method provided by this invention does not require high temperature and high pressure, has simple equipment requirements, and is easy to operate, which reduces energy consumption and cost and facilitates mass production. Red phosphorus surface impurity removal, etching, and chemical tin plating are completed simultaneously in the same reaction system, eliminating the need for precious metal catalysts compared to traditional tin coating. Furthermore, it can rapidly form a uniform coating layer, effectively solving the problems of complex equipment, high cost, high energy consumption, and limited application in existing technologies, providing a more efficient, economical, and practical innovative solution for material surface coating modification. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the sodium-ion battery anode material structure provided by the present invention.

[0044] Figure 2 This is a transmission electron microscope (TEM) image of the sodium electrode anode material provided in Example 1.

[0045] Wherein: 1-Red phosphorus core; 2-Chemical tin plating layer. Detailed Implementation

[0046] 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.

[0047] One embodiment of the present invention provides a sodium electrode anode material with chemically plated tin-coated red phosphorus, comprising a red phosphorus core and a chemically plated tin layer coating the surface of the red phosphorus core.

[0048] This invention involves coating the surface of red phosphorus material with a chemically plated tin layer. The high conductivity of metallic tin significantly reduces charge transfer resistance and improves overall conductivity. Simultaneously, the dense and continuous tin layer acts as a physical barrier, effectively isolating oxygen and moisture, thereby slowing down or even blocking the oxidation reaction on the red phosphorus surface, greatly improving the storage and processing stability of the red phosphorus. Due to the good ductility, high elasticity, and chemical inertness of the tin coating, it can effectively absorb the volume expansion stress generated by the red phosphorus during charge and discharge, inhibiting particle breakage and electrode structure collapse, thus significantly extending the battery's cycle life. Furthermore, metallic tin itself possesses electrochemical sodium storage activity and a theoretical specific capacity as high as 847 mAh / g, giving the composite material a high overall energy density, providing additional capacity contribution to the battery compared to traditional coatings.

[0049] In some embodiments, the average thickness of the electroless tin plating layer is 0.01-2 μm, for example, it can be 0.01 μm, 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0050] In some embodiments, the mass ratio of the electroless tin plating layer to the red phosphorus core is 1:(10-100), for example, it can be 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90 or 1:100, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] One embodiment of the present invention also provides a method for preparing the sodium-ion battery anode material described in any of the above embodiments, comprising the following steps:

[0052] (1) Mix red phosphorus powder and acid solution, disperse evenly and then separate solid and liquid. Wash red phosphorus until neutral, then disperse it in deionized water, add stabilizer and adjust pH value to obtain red phosphorus dispersion;

[0053] (2) Mix the tin salt solution and the red phosphorus dispersion obtained in step (1), add a reducing agent to carry out a chemical tin plating reaction, and uniformly coat the surface of the red phosphorus with metallic tin;

[0054] (3) The reaction mixture obtained in step (2) is subjected to solid-liquid separation, and the solid product is washed and dried in sequence to obtain sodium electrode material with chemically plated tin and coated red phosphorus.

[0055] The preparation method provided by this invention does not require high temperature and high pressure, has simple equipment requirements, and is easy to operate, thus reducing energy consumption and cost and facilitating mass production. It simultaneously completes red phosphorus surface impurity removal, etching, and chemical tin plating in the same reaction system, eliminating the need for precious metal catalysts compared to traditional tin coating. Furthermore, it can rapidly form a uniform coating layer, effectively solving the problems of complex equipment, high cost, high energy consumption, and limited application of existing technologies, providing a more efficient, economical, and practical innovative solution for material surface coating modification.

[0056] In some embodiments, the acid solution in step (1) includes a hydrochloric acid solution and / or a sulfuric acid solution, more preferably a hydrochloric acid solution.

[0057] In some embodiments, the concentration of the acid in step (1) is 2-5 wt%, for example, it can be 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] This invention uniformly disperses red phosphorus powder in an acid solution of appropriate concentration, thereby effectively removing the oxide layer on the surface of the red phosphorus.

[0059] In some embodiments, the solid-liquid ratio of the red phosphorus powder and acid solution in step (1) is 0.1-5 g / mL, for example, it can be 0.1 g / mL, 0.5 g / mL, 1 g / mL, 1.5 g / mL, 2 g / mL, 2.5 g / mL, 3 g / mL, 3.5 g / mL, 4 g / mL, 4.5 g / mL or 5 g / mL, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] In some embodiments, the mixing process in step (1) is accompanied by ultrasonic treatment.

[0061] In some embodiments, the washing in step (1) uses deionized water.

[0062] In some embodiments, the stabilizer in step (1) includes polyethylene glycol and / or polyvinylpyrrolidone.

[0063] In some embodiments, the amount of stabilizer added in the red phosphorus dispersion in step (1) is 0.1-0.5 g / L, for example, it can be 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L or 0.5 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0064] The present invention adds a stabilizer to the red phosphorus dispersion, which significantly improves the stability of the dispersion, prevents the red phosphorus powder from settling or agglomerating, and facilitates a more uniform tin coating. If the amount of stabilizer added is insufficient, the red phosphorus dispersion will be difficult to stabilize, while if the amount of stabilizer added is too high, it will lead to an unnecessary increase in preparation costs.

[0065] In some embodiments, the pH adjustment in step (1) is performed using hydrochloric acid solution and / or sulfuric acid solution, more preferably hydrochloric acid solution.

[0066] In some embodiments, the pH adjustment endpoint in step (1) is 2-2.5, for example, it can be 2, 2.1, 2.2, 2.3, 2.4 or 2.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] In some embodiments, the tin salt in the tin salt solution of step (2) includes stannous chloride and / or stannous sulfate.

[0068] In some embodiments, the concentration of the tin salt solution in step (2) is 10-30 g / L, for example, it can be 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 24 g / L, 26 g / L, 28 g / L or 30 g / L, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0069] In this invention, the concentration of the tin salt solution has a significant impact on the formation of the tin layer. If the concentration of the tin salt solution is too low, the supply of tin ions is insufficient, resulting in slow tin layer growth; if the concentration of the tin salt solution is too high, it is easy to cause hydrolysis of tin ions, which is also not conducive to tin layer growth.

[0070] In some embodiments, the tin salt solution in step (2) also contains a complexing agent, a stabilizer, and a pH adjuster.

[0071] In some embodiments, the complexing agent comprises citric acid and / or sodium citrate, in a concentration of 5-15 g / L in the tin salt solution, for example, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L or 15 g / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0072] This invention involves adding a complexing agent to a tin salt solution, which can undergo a complexation reaction with tin ions, preventing their hydrolysis. If the content of the complexing agent is too low, the tin ions are easily hydrolyzed; if the content of the complexing agent is too high, it will lead to slow release of tin ions and a significant reduction in the deposition rate.

[0073] In some embodiments, the stabilizer comprises thiourea and / or potassium ferrocyanide in a concentration of 0.05-0.2 g / L in the tin salt solution, for example, 0.05 g / L, 0.06 g / L, 0.07 g / L, 0.08 g / L, 0.09 g / L, 0.1 g / L, 0.11 g / L, 0.12 g / L, 0.13 g / L, 0.14 g / L, 0.15 g / L, 0.16 g / L, 0.17 g / L, 0.18 g / L, 0.19 g / L, or 0.2 g / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0074] In this invention, the stabilizer can be adsorbed onto the surface of the reduced tin layer, preventing uneven growth of the tin layer. If the stabilizer content is too low, free tin particles are easily generated; if the stabilizer content is too high, the activity of the tin coated on the red phosphorus surface will decrease, causing the chemical tin plating reaction to stop prematurely.

[0075] In some embodiments, the pH adjuster includes hydrochloric acid solution and / or sulfuric acid solution, and the pH adjustment endpoint is 1-3, for example, it can be 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or 3, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0076] In some embodiments, the reducing agent in step (2) includes sodium hypophosphite, whose reaction equation for reducing tin ions is as follows:

[0077]

[0078] In some embodiments, the amount of reducing agent added to the mixed solution in step (2) is 20-30 g / L, for example, it can be 20 g / L, 21 g / L, 22 g / L, 23 g / L, 24 g / L, 25 g / L, 26 g / L, 27 g / L, 28 g / L, 29 g / L or 30 g / L, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0079] In this invention, an appropriate amount of reducing agent can ensure the complete reduction of tin ions. If the amount of reducing agent added is too low, the tin layer will not be complete; if the amount of reducing agent added is too high, it will cause the reducing agent to decompose on its own.

[0080] In some embodiments, the molar ratio of the reducing agent to the tin ions in the tin salt solution in step (2) is (1-2):1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1 or 2:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0081] In some embodiments, the temperature of the chemical tin plating reaction in step (2) is 30-40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0082] In some embodiments, the washing in step (3) uses deionized water.

[0083] One embodiment of the present invention also provides a sodium-ion battery anode sheet, comprising at least the sodium-ion battery anode material with chemically plated tin-coated red phosphorus as described in any of the above embodiments.

[0084] One embodiment of the present invention also provides a sodium-ion battery, comprising at least the sodium-ion anode material with chemically plated tin-coated red phosphorus as described in any of the above embodiments, or the sodium-ion anode sheet as described in any of the above embodiments.

[0085] 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.

[0086] Example 1

[0087] This embodiment provides a sodium electrode anode material with chemically plated tin-coated red phosphorus and its preparation method, the preparation method including the following steps:

[0088] (1) Add 10g of red phosphorus powder to 100mL of 2wt% hydrochloric acid solution and ultrasonically disperse for 30min to ensure uniform dispersion of red phosphorus. Then filter out the red phosphorus, wash with deionized water until neutral, then disperse the washed red phosphorus in deionized water, add 0.1g of polyethylene glycol, and add hydrochloric acid solution to adjust the pH to 2.5 to obtain red phosphorus dispersion.

[0089] (2) Add 0.5g citric acid and 0.05g thiourea to 100mL of stannous chloride solution with a concentration of 10g / L, and adjust the pH to 2.5 with hydrochloric acid solution. Then mix it evenly with the red phosphorus dispersion obtained in step (1), add 2g sodium hypophosphite to the mixed solution, and carry out a chemical tin plating reaction at 30℃ to deposit Sn. 2+ It is reduced to Sn and uniformly coated on the surface of red phosphorus.

[0090] (3) After the reaction is completed, the reaction mixture obtained in step (2) is filtered, and the solid product is repeatedly washed with deionized water to remove residual solvent and reactants. Then the washed sample is dried to obtain sodium electrode material with chemically plated tin-coated red phosphorus.

[0091] like Figure 1 As shown, the sodium-ion battery anode material obtained in this embodiment includes a red phosphorus core 1 and a chemically plated tin layer 2 coating the surface of the red phosphorus core 1. A transmission electron microscope (TEM) image is shown below. Figure 2 It can be seen that the average thickness of its chemical tin plating layer is about 0.3 μm.

[0092] Example 2

[0093] This embodiment provides a sodium electrode anode material with chemically plated tin-coated red phosphorus and its preparation method, the preparation method including the following steps:

[0094] (1) Add 40g of red phosphorus powder to 200mL of 3wt% hydrochloric acid solution and ultrasonically disperse for 30min to ensure uniform dispersion of red phosphorus. Then filter out the red phosphorus, wash with deionized water until neutral, then disperse the washed red phosphorus in deionized water, add 0.4g of polyethylene glycol, and add hydrochloric acid solution to adjust the pH value to 2 to obtain red phosphorus dispersion.

[0095] (2) Add 1.6g citric acid and 0.2g potassium ferrocyanide to 200mL of stannous chloride solution with a concentration of 30g / L, and adjust the pH to 2 with hydrochloric acid solution. Then mix it evenly with the red phosphorus dispersion obtained in step (1), add 5g sodium hypophosphite to the mixed solution, and carry out a chemical tin plating reaction at 35℃ to deposit Sn. 2+ It is reduced to Sn and uniformly coated on the surface of red phosphorus.

[0096] (3) After the reaction is completed, the reaction mixture obtained in step (2) is filtered, and the solid product is repeatedly washed with deionized water to remove residual solvent and reactants. Then the washed sample is dried to obtain sodium electrode material with chemically plated tin-coated red phosphorus.

[0097] The structure and microstructure of the sodium-ion battery anode material obtained in this embodiment are similar to those in Example 1, so they will not be described again here.

[0098] Example 3

[0099] This embodiment provides a sodium electrode anode material with chemically plated tin-coated red phosphorus and its preparation method, the preparation method including the following steps:

[0100] (1) Add 30g of red phosphorus powder to 100mL of 4wt% hydrochloric acid solution and ultrasonically disperse for 30min to ensure uniform dispersion of red phosphorus. Then filter out red phosphorus, wash with deionized water until neutral, then disperse the washed red phosphorus in deionized water, add 0.4g of polyethylene glycol, and add hydrochloric acid solution to adjust the pH value to 2 to obtain red phosphorus dispersion.

[0101] (2) Add 3g of citric acid and 1.5g of potassium ferrocyanide to 300mL of stannous chloride solution with a concentration of 15g / L, and adjust the pH to 2 with hydrochloric acid solution. Then mix it evenly with the red phosphorus dispersion obtained in step (1), add 5g of sodium hypophosphite to the mixed solution, and carry out a chemical tin plating reaction at 40℃ to deposit Sn. 2+ It is reduced to Sn and uniformly coated on the surface of red phosphorus.

[0102] (3) After the reaction is completed, the reaction mixture obtained in step (2) is filtered, and the solid product is repeatedly washed with deionized water to remove residual solvent and reactants. Then the washed sample is dried to obtain sodium electrode material with chemically plated tin-coated red phosphorus.

[0103] The structure and microstructure of the sodium-ion battery anode material obtained in this embodiment are similar to those in Example 1, so they will not be described again here.

[0104] Example 4

[0105] This embodiment provides a sodium electrode anode material with chemically plated tin-coated red phosphorus and its preparation method, the preparation method including the following steps:

[0106] (1) Add 25g of red phosphorus powder to 50mL of 5wt% hydrochloric acid solution and ultrasonically disperse for 30min to ensure uniform dispersion of red phosphorus. Then filter out the red phosphorus, wash with deionized water until neutral, then disperse the washed red phosphorus in deionized water, add 0.5g of polyvinylpyrrolidone, and add hydrochloric acid solution to adjust the pH to 2 to obtain red phosphorus dispersion.

[0107] (2) Add 4.5g sodium citrate and 0.3g thiourea to 300mL of stannous chloride solution with a concentration of 30g / L, and adjust the pH to 1 with hydrochloric acid solution. Then mix it evenly with the red phosphorus dispersion obtained in step (1), add 9g sodium hypophosphite to the mixed solution, and carry out a chemical tin plating reaction at 40℃ to deposit Sn. 2+ It is reduced to Sn and uniformly coated on the surface of red phosphorus.

[0108] (3) After the reaction is completed, the reaction mixture obtained in step (2) is filtered, and the solid product is repeatedly washed with deionized water to remove residual solvent and reactants. Then the washed sample is dried to obtain sodium electrode material with chemically plated tin-coated red phosphorus.

[0109] The structure and microstructure of the sodium-ion battery anode material obtained in this embodiment are similar to those in Example 1, so they will not be described again here.

[0110] Example 5

[0111] This embodiment provides a sodium electrode anode material with chemically plated tin-coated red phosphorus and its preparation method, the preparation method including the following steps:

[0112] (1) Add 200g of red phosphorus powder to 500mL of 4wt% hydrochloric acid solution and ultrasonically disperse for 30min to ensure uniform dispersion of red phosphorus. Then filter out red phosphorus, wash with deionized water until neutral, then disperse the washed red phosphorus in deionized water, add 2g of polyvinylpyrrolidone, and add hydrochloric acid solution to adjust the pH to 2 to obtain red phosphorus dispersion.

[0113] (2) Add 6g of sodium citrate and 5g of thiourea to 500mL of stannous chloride solution with a concentration of 20g / L, and adjust the pH to 1 with hydrochloric acid solution. Then mix it evenly with the red phosphorus dispersion obtained in step (1), add 7.5g of sodium hypophosphite to the mixed solution, and carry out a chemical tin plating reaction at 30℃ to deposit Sn. 2+ It is reduced to Sn and uniformly coated on the surface of red phosphorus.

[0114] (3) After the reaction is completed, the reaction mixture obtained in step (2) is filtered, and the solid product is repeatedly washed with deionized water to remove residual solvent and reactants. Then the washed sample is dried to obtain sodium electrode material with chemically plated tin-coated red phosphorus.

[0115] The structure and microstructure of the sodium-ion battery anode material obtained in this embodiment are similar to those in Example 1, so they will not be described again here.

[0116] Comparative Example 1

[0117] This comparative example uses untreated red phosphorus powder as the sodium electrode anode material.

[0118] Performance testing

[0119] Sodium-ion half-cells were prepared using the sodium-ion anode materials obtained in Examples 1-5 and Comparative Example 1. The preparation method was as follows: the sodium-ion anode material was mixed with binder (CMC) and conductive carbon (Super P) in a mass ratio of 8:1:1 to form a slurry and then coated. The resulting sodium-ion anode sheet and sodium sheet were assembled in a glove box with a water oxygen value of less than 0.01 ppm to obtain a sodium-ion half-cell.

[0120] The electrochemical performance of the obtained sodium-ion half-cell was tested on a new device. Specifically, the first charge-discharge cycle was performed at a current density of 100 mA / g to obtain the first charge specific capacity and first efficiency (first efficiency = first discharge specific capacity / first charge specific capacity). Then, the cell was cycled at a current density of 1000 mA / g and its cycle performance was compared. The capacity retention rate was the charge specific capacity after 200 cycles / the charge specific capacity of the first cycle. The relevant test results are shown in Table 1 below.

[0121] Table 1

[0122]

[0123] As shown in Table 1:

[0124] Compared to the untreated red phosphorus powder in Comparative Example 1, the sodium-ion battery anode materials with electroless tin plating and red phosphorus coating obtained in Examples 1-5 exhibit higher first-cycle charge specific capacity, first-cycle efficiency, and capacity retention. This is because the optimization effect of coating modification on the electrochemical performance of red phosphorus is mainly reflected in the following two aspects:

[0125] (1) The coating modification significantly improved the conductivity of red phosphorus. This change directly reduced the mass transfer resistance of sodium ions and effectively avoided the generation of severe kinetic obstacles. On this basis, the electron conduction efficiency inside the electrode was greatly improved, successfully solving the problem of slow electrochemical kinetics caused by the poor intrinsic conductivity of red phosphorus, and finally achieving higher capacity utilization and first-cycle coulombic efficiency (first-cycle efficiency).

[0126] (2) Red phosphorus materials exhibit significant volume expansion and contraction during charge-discharge cycles. The tin coating can buffer the internal stress generated by this volume change, reduce the cracking and pulverization of the electrode structure, and thus significantly improve the cycle stability of the electrode.

[0127] Therefore, this invention coats the surface of red phosphorus material with a chemically plated tin layer. The high conductivity of metallic tin significantly reduces charge transfer resistance and improves overall conductivity. Simultaneously, the dense and continuous tin layer acts as a physical barrier, effectively isolating oxygen and moisture, thereby slowing down or even blocking the oxidation reaction on the red phosphorus surface, greatly improving the storage and processing stability of red phosphorus. Due to the good ductility, high elasticity, and chemical inertness of the tin coating, it can effectively absorb the volume expansion stress generated by red phosphorus during charging and discharging, inhibiting particle breakage and electrode structure collapse, thus significantly extending the battery's cycle life. Furthermore, metallic tin itself possesses electrochemical sodium storage activity and a theoretical specific capacity as high as 847 mAh / g, giving the composite material a high overall energy density, providing additional capacity contribution to the battery compared to traditional coatings.

[0128] 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 sodium electrode anode material with chemically plated tin and coated red phosphorus, characterized in that, The sodium-ion anode material comprises a red phosphorus core and a chemically plated tin layer covering the surface of the red phosphorus core.

2. The sodium electrode anode material with chemically plated tin and coated red phosphorus according to claim 1, characterized in that, The average thickness of the chemically plated tin layer is 0.01-2 μm; And / or, the mass ratio of the chemically plated tin layer to the red phosphorus core is 1:(10-100).

3. A method for preparing the sodium-ion battery anode material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Mix red phosphorus powder and acid solution, disperse evenly and then separate solid and liquid. Wash red phosphorus until neutral, then disperse it in deionized water, add stabilizer and adjust pH value to obtain red phosphorus dispersion; (2) Mix the tin salt solution and the red phosphorus dispersion obtained in step (1), add a reducing agent to carry out a chemical tin plating reaction, and uniformly coat the surface of the red phosphorus with metallic tin; (3) The reaction mixture obtained in step (2) is subjected to solid-liquid separation, and the solid product is washed and dried in sequence to obtain sodium electrode material with chemically plated tin and coated red phosphorus.

4. The method for preparing the sodium-ion battery anode material according to claim 3, characterized in that, The acid solution in step (1) includes hydrochloric acid solution and / or sulfuric acid solution, more preferably hydrochloric acid solution; And / or, the concentration of the acid solution in step (1) is 2-5 wt%; And / or, the solid-liquid ratio of the red phosphorus powder and acid solution in step (1) is 0.1-5 g / mL; And / or, the mixing process described in step (1) is accompanied by ultrasonic treatment.

5. The method for preparing the sodium-ion battery anode material according to claim 3 or 4, characterized in that, The washing process in step (1) uses deionized water; And / or, the stabilizer in step (1) includes polyethylene glycol and / or polyvinylpyrrolidone; And / or, the amount of stabilizer added to the red phosphorus dispersion in step (1) is 0.1-0.5 g / L; And / or, the pH adjustment in step (1) is performed using hydrochloric acid solution and / or sulfuric acid solution, more preferably hydrochloric acid solution; And / or, the pH adjustment endpoint in step (1) is 2-2.

5.

6. The method for preparing the sodium-ion battery anode material according to claim 3, characterized in that, The tin salt in the tin salt solution in step (2) includes stannous chloride and / or stannous sulfate; And / or, the concentration of the tin salt solution in step (2) is 10-30 g / L; And / or, the tin salt solution in step (2) also contains a complexing agent, a stabilizer and a pH adjuster; The complexing agent includes citric acid and / or sodium citrate, and its content in the tin salt solution is 5-15 g / L; And / or, the stabilizer comprises thiourea and / or potassium ferrocyanide, in a concentration of 0.05-0.2 g / L in the tin salt solution; And / or, the pH adjuster includes hydrochloric acid solution and / or sulfuric acid solution, and the pH adjustment endpoint is 1-3.

7. The method for preparing the sodium-ion battery anode material according to claim 3 or 6, characterized in that, The reducing agent in step (2) includes sodium hypophosphite; And / or, the amount of reducing agent added to the mixed solution in step (2) is 20-30 g / L; And / or, the molar ratio of the reducing agent in step (2) to the tin ions in the tin salt solution is (1-2):

1.

8. The method for preparing the sodium-ion battery anode material according to claim 3 or 6, characterized in that, The temperature of the chemical tin plating reaction in step (2) is 30-40℃; And / or, the washing in step (3) uses deionized water.

9. A sodium-ion battery negative electrode, characterized in that, The sodium-ion anode sheet comprises at least the sodium-ion anode material with chemically plated tin-coated red phosphorus as described in claim 1 or 2.

10. A sodium-ion battery, characterized in that, The sodium-ion battery comprises at least the sodium-ion anode material with chemically plated tin-coated red phosphorus as described in claim 1 or 2, or the sodium-ion anode sheet as described in claim 9.

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