Fused salt method nano-phosphorus tin composite graphene negative electrode material and application thereof

Abstract

The application belongs to the technical field of lithium battery electrode material, and particularly relates to a molten salt method nano tin phosphide composite graphene negative electrode material and application thereof. The application uses a molten salt method to combine tin salt, lithium chloride and potassium chloride as molten salt materials, designs and synthesizes nano tin dioxide composite graphene, and then obtains carbon-based tin phosphide nano composite material through phosphorization treatment. The raw materials used in the application are widely sourced, cheap and easy to obtain, and the preparation process is simple, effectively solving the problems of harsh preparation experimental conditions, dangerous operation and complex process of tin particle composite materials in the prior art. Meanwhile, the prepared tin phosphide nano particle composite graphene high-performance lithium storage material has regular morphology, uniform size and uniform particle size distribution, has high structural stability, large specific surface area, high surface activity and short ion transmission distance, thereby being capable of providing higher capacity and better cycle stability for lithium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a molten salt method nano-tin phosphide composite graphene anode material and its application. Background Technology

[0002] With continuous technological advancements and the dwindling supply of traditional energy sources, coupled with increasing environmental degradation, the search for and development of new energy sources has become paramount. Traditional batteries, due to their low energy density and environmental pollution, can no longer meet current market demands. Lithium-sodium ion batteries, with their unique advantages, have experienced rapid development. Tin phosphide, with its high theoretical specific capacity, low cost, and environmental friendliness, has attracted widespread attention as a potential anode material for lithium-sodium ion batteries. However, its poor conductivity during cycling, volume effect, and capacity decay severely limit its commercial application.

[0003] In existing technologies, tin phosphide is mainly prepared through methods such as mechanical ball milling, low-temperature hydrothermal phosphating, vapor-phase phosphating, and solution-liquid-solid phase growth. For example, Chinese invention patent CN201911243058.8 discloses a tin phosphide / expanded graphite anode composite material for sodium-ion batteries and its preparation method. This method loads the tin phosphide / expanded graphite composite material onto exfoliated graphite sheets to form a conductive network. The spherical composite material, compared to irregular blocky materials, facilitates full electrolyte wetting, alleviates volume expansion, and maintains a spherical structure during cycling, thus improving electrochemical performance. However, the resulting material exhibits significant differences in size and morphology, affecting its further improvement in electrochemical performance as a lithium-ion battery anode material. Therefore, there is an urgent need for a method to prepare a high-performance battery anode material with regular morphology, uniform size, and uniform particle size distribution of nano-tin phosphide composite graphene. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a molten salt method nano-tin phosphide composite graphene anode material and its application.

[0005] The first aspect of this invention provides a molten salt method for preparing nano-tin phosphide composite graphene anode material, the preparation method of which includes the following steps:

[0006] S1. Dissolve soluble tin salt, molten salt material, and graphene oxide in water by stirring, then evaporate to dryness in an oil bath, calcine, wash and dry to obtain precursor particles;

[0007] S2. The precursor particles obtained in step S1 are mixed with NaH2PO2, ground, and calcined. After the reaction is completed, the mixture is cooled, washed, and dried to obtain nano-tin phosphide composite graphene anode material.

[0008] Preferably, in step S1, the soluble tin salt comprises one or more of tin dichloride and stannous sulfate.

[0009] Preferably, in step S1, the molten salt material comprises one or more of lithium chloride and potassium chloride.

[0010] Preferably, in step S1, the method for preparing the graphene oxide includes the following steps:

[0011] (1) Add graphite sheets and sodium nitrate to a container containing concentrated sulfuric acid placed in an ice bath and stir;

[0012] (2) Add KMnO4 to the container and continue stirring;

[0013] (3) Transfer the container to a water bath and stir at 20-50 ℃;

[0014] (4) Add ultrapure water droplets into the container to lower the solution temperature to below 40°C;

[0015] (5) Transfer the container to an oil bath at 95-100℃ and keep stirring vigorously for 20-40 minutes. Then add ultrapure water and H2O2 continuously at room temperature to obtain GO solution.

[0016] (6) After centrifuging the GO solution, dialyze it until the pH value is close to neutral to obtain a concentrated GO solution. Then, vacuum dry the GO solution at 80°C.

[0017] Preferably, in step S1, the molar ratio of tin salt, lithium chloride, and potassium chloride is 1:20-30:5-10.

[0018] Preferably, in step S1, the oil bath temperature is 80-100℃ and the time is 12-24 h.

[0019] Preferably, in step S1, the calcination temperature is 500-580℃, the heating rate is 2-8℃ / min, and the reaction time is 2-6 h.

[0020] Preferably, in step S2, the calcination temperature is 240-320℃, the heating rate is 2-8℃ / min, and the reaction time is 5-30min.

[0021] A second aspect of the present invention is to provide a battery containing the molten salt method nano-tin phosphide composite graphene material as described above.

[0022] Preferably, the preparation method includes the following steps:

[0023] A. Weigh out nano-tin phosphide composite graphene material, acetylene black and sodium alginate, add an appropriate amount of distilled water, mix well, grind and stir into a paste, and coat it on copper foil;

[0024] B. The copper foil coated in step A is dried, sliced, assembled, and pressed to obtain the battery.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention utilizes the molten salt method to design and synthesize nano-tin dioxide composite graphene by using tin salt, supplemented with lithium chloride and potassium chloride as molten salt materials, and then obtains carbon-based tin phosphide nanocomposite material through phosphating treatment.

[0027] The raw materials used in this invention are widely available, inexpensive, and easy to obtain, and the preparation process is simple, effectively solving the problems of harsh experimental conditions, dangerous operations, and complex processes in the preparation of tin particle composite materials in existing technologies. Simultaneously, the prepared tin phosphide nanoparticle composite graphene high-performance lithium storage material has a regular morphology, uniform size, and uniform particle size distribution, exhibiting high structural stability, large specific surface area, high surface activity, and short ion transport distance, thereby providing higher capacity and better cycle stability for lithium-ion batteries.

[0028] In this invention, tin phosphide nanoparticles combined with graphene are used as high-performance lithium storage materials for lithium-ion batteries. In some embodiments of this invention, the prepared tin phosphide nanoparticles combined with graphene are used as the negative electrode material in lithium-ion batteries, achieving a performance of 100 mA g⁻¹. -1 At a current density of 973 mAh g, the battery capacity after 100 charge-discharge cycles is 973 mAh g. -1 Its specific capacity is 372 mAh g compared to that of commercial graphite anodes. -1 In terms of performance, this invention offers significant improvements and exhibits good cycle stability. Therefore, the tin phosphide nanoparticle composite graphene high-performance lithium storage material proposed in this invention is suitable for widespread use as a lithium-ion battery anode. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0030] Figure 1 This is a scanning electron microscope (TEM) image of the tin phosphide nanoparticle composite graphene high-performance lithium storage material prepared in Example 1 of the present invention;

[0031] Figure 2This is a scanning electron microscope (SEM) image of the tin phosphide nanoparticle composite graphene high-performance lithium storage material prepared in Example 1 of the present invention.

[0032] Figure 3 The X-ray diffraction patterns are shown for the tin phosphide nanoparticle composite graphene high-performance lithium storage materials prepared in Examples 1, 2, and 3 of this invention.

[0033] Figure 4 The tin phosphide nanoparticle composite graphene prepared in Example 1 of this invention was used as a negative electrode material for lithium-ion batteries at 100 mA g. -1 Cyclic stability test graphs and charge-discharge curves at current density;

[0034] Figure 5 The tin phosphide nanoparticle composite graphene prepared in Example 1 of this invention was used as a negative electrode material for lithium-ion batteries at 1000 mA g. -1 Cyclic stability test diagram at current density: charge-discharge curve;

[0035] Figure 6 The graph shows the rate cycling performance of the tin phosphide nanoparticle composite graphene prepared in Example 1 of this invention as a negative electrode material for lithium-ion batteries at different current densities. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Example 1

[0038] S1. Weigh 0.900g tin dichloride, 7.461g potassium chloride, 2.546g lithium chloride, and 40ml graphene oxide, dissolve them in 50ml ultrapure water, stir well, and then place the reaction solution in a 90°C container. o C-oil bath for 12-24 hours, evaporate all moisture (later transfer to 80°C) o (C oven for further drying); the dried solid mixture was ground in an agate mortar for 20 minutes, then collected in an alumina crucible and placed in a muffle furnace, heated to 540 ℃ at a heating rate of 5 ℃ / min, calcined for 4 hours, and then cooled naturally; the product obtained from the reaction was desalted by immersion in deionized water, dried, and the precursor particles were obtained.

[0039] S2. Weigh 0.1g of precursor particles and 3g of NaH2PO2, grind for 3 minutes, then place the mixed powder in a tube furnace under a nitrogen atmosphere and react at 280℃ for 10 minutes (heating rate is 5). oAfter the reaction was completed and cooled to room temperature, the nano-tin phosphide composite graphene anode material was obtained by filtration and washing with 0.1 mol / L hydrochloric acid, deionized water and ethanol respectively, and then dried.

[0040] S3. Weigh out nano-tin phosphide composite graphene material, acetylene black and sodium alginate, add an appropriate amount of distilled water, mix evenly, grind and stir into a paste, and coat it on copper foil.

[0041] S4. The copper foil coated in step A is dried, sliced, assembled, and pressed to obtain a lithium-ion battery.

[0042] Graphene oxide was prepared by the following method: A certain amount of graphite sheets and sodium nitrate were added to a beaker containing a certain amount of concentrated sulfuric acid and placed in an ice bath. The suspension was continuously stirred mechanically for 2 hours. A certain amount of KMnO4 was then slowly added, and the mixture was stirred for another 2 hours. The beaker was then transferred to a water bath and heated at 35°C. o Stir at C for 1 hour. Add a certain amount of ultrapure water dropwise into the beaker to lower the solution temperature below 40°C. o C. Then, transfer the beaker to 98°C. o The GO solution was placed in an oil bath at C and stirred vigorously for 30 minutes. Then, a certain amount of ultrapure water and H2O2 were continuously added at room temperature. Finally, the GO solution was centrifuged with ultrapure water, and the resulting product was dialyzed in a dialysis bag until the pH was close to neutral. It was then stored in a dark brown, sealed glass bottle. The concentration of GO nanosheets in the obtained concentrated GO solution was estimated by the mass of the GO nanosheets, i.e., at 80... o It is obtained by vacuum drying of GO solution at C.

[0043] Example 2

[0044] S1. Weigh 0.900 g of tin dichloride, 7.461 g of potassium chloride, 2.546 g of lithium chloride, and 40 ml of graphene oxide, dissolve them in 50 ml of ultrapure water, stir well, and then place the reaction solution in a 90°C container. o C-oil bath for 12-24 hours, evaporate all moisture (later transfer to 80°C) o (C) Further drying in an oven. The resulting solid mixture was ground in an agate mortar for 20 minutes, then collected in an alumina crucible and placed in a muffle furnace. The temperature was increased to 540 °C at a rate of 5 °C / min and calcined for 4 hours, followed by natural cooling. The product obtained from the reaction was desalted by immersion in deionized water and dried to obtain precursor particles.

[0045] S2. Weigh 0.1g of precursor particles and 3g of NaH2PO2, grind for 3 minutes, then place the mixed powder in a tube furnace under a nitrogen atmosphere and react at 280℃ for 30 minutes (heating rate 5). o After the reaction was completed and cooled to room temperature, the nano-tin phosphide composite graphene anode material was obtained by filtration and washing with 0.1 mol / L hydrochloric acid, deionized water and ethanol respectively, and then dried.

[0046] S3. Weigh out nano-tin phosphide composite graphene material, acetylene black and sodium alginate, add an appropriate amount of distilled water, mix evenly, grind and stir into a paste, and coat it on copper foil.

[0047] S4. The copper foil coated in step A is dried, sliced, assembled, and pressed to obtain a lithium-ion battery.

[0048] Graphene oxide was prepared by the following method: A certain amount of graphite sheets and sodium nitrate were added to a beaker containing a certain amount of concentrated sulfuric acid and placed in an ice bath. The suspension was continuously stirred mechanically for 2 hours. A certain amount of KMnO4 was then slowly added, and the mixture was stirred for another 2 hours. The beaker was then transferred to a water bath and heated at 35°C. o Stir at C for 1 hour. Add a certain amount of ultrapure water dropwise into the beaker to lower the solution temperature below 40°C. o C. Then, transfer the beaker to 98°C. o The GO solution was placed in an oil bath at C and stirred vigorously for 30 minutes. Then, a certain amount of ultrapure water and H2O2 were continuously added at room temperature. Finally, the GO solution was centrifuged with ultrapure water, and the resulting product was dialyzed in a dialysis bag until the pH was close to neutral. It was then stored in a dark brown, sealed glass bottle. The concentration of GO nanosheets in the obtained concentrated GO solution was estimated by the mass of the GO nanosheets, i.e., at 80... o It is obtained by vacuum drying of GO solution at C.

[0049] Example 3

[0050] S1. Weigh 0.900 g of tin dichloride, 7.461 g of potassium chloride, 2.546 g of lithium chloride, and 40 ml of graphene oxide, dissolve them in 50 ml of ultrapure water, stir well, and then place the reaction solution in a 90°C container. o C-oil bath for 12-24 hours, evaporate all moisture (later transfer to 80°C) o (C) Further drying in an oven. The resulting solid mixture was ground in an agate mortar for 20 minutes, then collected in an alumina crucible and placed in a muffle furnace. The temperature was increased to 540 °C at a rate of 5 °C / min and calcined for 4 hours, followed by natural cooling. The product obtained from the reaction was desalted by immersion in deionized water and dried to obtain precursor particles.

[0051] S2. Weigh 0.1g of precursor particles and 3g of NaH2PO2, grind for 3 minutes, and then place the mixed powder in a tube furnace under a nitrogen atmosphere and react at 280℃ for 5 minutes (heating rate 5). o After the reaction was completed and cooled to room temperature, the nano-tin phosphide composite graphene anode material was obtained by filtration, washing and drying with 0.1 mol / L hydrochloric acid, deionized water and ethanol respectively.

[0052] S3. Weigh out nano-tin phosphide composite graphene material, acetylene black and sodium alginate, add an appropriate amount of distilled water, mix evenly, grind and stir into a paste, and coat it on copper foil.

[0053] S4. The copper foil coated in step A is dried, sliced, assembled, and pressed to obtain a lithium-ion battery.

[0054] Graphene oxide was prepared by the following method: A certain amount of graphite sheets and sodium nitrate were added to a beaker containing a certain amount of concentrated sulfuric acid and placed in an ice bath. The suspension was continuously stirred mechanically for 2 hours. A certain amount of KMnO4 was then slowly added, and the mixture was stirred for another 2 hours. The beaker was then transferred to a water bath and heated at 35°C. o Stir at C for 1 hour. Add a certain amount of ultrapure water dropwise into the beaker to lower the solution temperature below 40°C. o C. Then, transfer the beaker to 98°C. o The GO solution was placed in an oil bath at C and stirred vigorously for 30 minutes. Then, a certain amount of ultrapure water and H2O2 were continuously added at room temperature. Finally, the GO solution was centrifuged with ultrapure water, and the resulting product was dialyzed in a dialysis bag until the pH was close to neutral. It was then stored in a dark brown, sealed glass bottle. The concentration of GO nanosheets in the obtained concentrated GO solution was estimated by the mass of the GO nanosheets, i.e., at 80... o It is obtained by vacuum drying of GO solution at C.

[0055] Microscopic characterization

[0056] The following are microscopic characterizations of the graphene-based tin phosphide nanocomposite high-performance lithium storage materials prepared in Examples 1-3 using different methods:

[0057] Figure 1This is a TEM image of the graphene-based tin phosphide nanocomposite high-performance lithium storage material from Example 1. The TEM image shows that the graphene-based tin phosphide nanoparticles are all around 20 nm in size and have a relatively uniform spherical morphology. Furthermore, the image shows that the tin phosphide particles are "anchored" to the graphene sheets. The molten salt preparation method allows the tin phosphide particles to be uniformly "anchored" to the graphene surface, forming a composite material, thereby effectively suppressing particle aggregation and mitigating the volume expansion of the matrix during the electrochemical process of the tin phosphide particles. At high magnification, the TEM clearly shows a layer of gauze-like graphene sheets attached to the tin phosphide particles, indicating that the tin phosphide particles are adhered to the graphene nanolayer structure. Because the hydroxyl groups and epoxides of graphene form bonds with the tin phosphide particles, the tin phosphide is stably attached to the sheet structure. These graphene fragment structures help suppress the volume change of the tin phosphide particles during the electrode reaction process and mitigate volume expansion.

[0058] Figure 2 This is a SEM image of the graphene-based tin phosphide nanocomposite high-performance lithium storage material prepared in Example 1. Due to the encapsulation of tin phosphide nanoparticles by graphene and the aggregation of graphene itself, the morphology of the composite cannot be well characterized in SEM, especially the distribution of tin phosphide on the graphene. However, it can still be observed that the tin phosphide nanoparticles and graphene are successfully composited.

[0059] Figure 3 The images show the X-ray diffraction patterns of the graphene-based tin phosphide nanocomposite high-performance lithium storage materials prepared in Examples 1, 2, and 3. As can be seen from the figures, the samples obtained after reacting at 540℃ for 5 min, 10 min, and 30 min respectively showed the following differences: Example 2, due to the short reaction time, resulted in tin phosphide particles with poor crystallinity and a small amount of unreacted tin dioxide particles; Example 3, due to the long reaction time, gradually generated other phosphorus-rich tin phosphide impurities; while Example 1, representing the optimal reaction time, yielded tin phosphide that was completely consistent with the comparison card and exhibited strong crystallinity.

[0060] Electrochemical performance characterization

[0061] Figure 4 100 mA g of the graphene-based tin phosphide nanocomposite high-performance lithium storage material prepared in Example 1 -1 Comparison of cycling stability tests at current densities. It can be seen that the graphene-based tin phosphide nanocomposite high-performance lithium storage anode material exhibits good performance at 100 mA g / L. -1 At current density, the capacity still has 967 mAh g after 100 cycles. -1 Furthermore, the capacity remains essentially unchanged; at the same time, the charge-discharge curves of the material in the 5th, 10th, 15th, and 30th cycles show a high degree of overlap, indicating good cycle stability, which is consistent with the cycle performance graph.

[0062] Figure 5 1000 mA g of the graphene-based tin phosphide nanocomposite high-performance lithium storage material prepared in Example 1 -1 Comparison of cycling stability tests at current densities. It can be seen from the graph that the graphene-based tin phosphide nanocomposite high-performance lithium storage anode material of Example 1 exhibits good performance at 1000 mA g / L. -1 At current density, the capacity still has 649 mAh g after 200 cycles. -1 During this period, the capacity showed a decreasing trend, but after 700 cycles, the capacity increased to 1560mAh g. -1 Furthermore, the capacity is still showing an upward trend, which may be related to the activation stage of the electrode during the cycling process. At the same time, the charge-discharge curves of the material in the 5th, 10th, 15th and 30th cycles have a high degree of overlap, indicating that the material has good cycling stability, which is consistent with the cycling performance diagram.

[0063] Figure 6 This is a comparison of the cycling stability tests of the graphene-based tin dioxide nanocomposite high-performance lithium storage material prepared in Example 1 at different current densities. It can be seen that the graphene-based tin phosphide nanocomposite high-performance lithium storage anode material of Example 1 exhibits different cycling stability at different rate factors (100, 200, 500, 1000, 2000 mA g). -1 They have capacities of 730, 665, 602, 561, and 523 mAh g, respectively. -1 The reversible capacity, even at 2000 mA g -1 Even at high current densities, it still maintains a 63% capacity retention, attributed to the presence of graphene in the sample. This graphene effectively prevents particle aggregation during cycling, maintaining structural stability and providing a suitable environment for Li... + The transmission provides more channels, and the significant nano-sized particles resulting from the molten salt preparation method give it superior electrochemical performance, especially when the current returns to 100 mA g. -1 At that time, the specific capacity can still be maintained at 760mAh / g, and the coulombic efficiency is 92%, which proves that it has very good cycle stability.

[0064] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A molten salt method nano-tin phosphide composite graphene anode material, characterized in that, Its preparation method includes the following steps: S1. Dissolve soluble tin salt, molten salt material, and graphene oxide in water by stirring, then evaporate to dryness in an oil bath, calcine, wash and dry to obtain precursor particles; S2. The precursor particles obtained in step S1 are mixed with NaH2PO2, ground and calcined. After the reaction is completed, the mixture is cooled, washed and dried to obtain nano-tin phosphide composite graphene anode material. In step S1, the soluble tin salt comprises one or more of tin dichloride and stannous sulfate, and the molten salt material comprises one or more of lithium chloride and potassium chloride. The molar ratio of the tin salt, lithium chloride, and potassium chloride is 1:20-30:5-10. In step S1, the oil bath temperature is 80-100℃, and the time is 12-24 hours. In step S1, the calcination temperature is 500-580℃, the heating rate is 2-8℃ / min, and the reaction time is 2-6 h. In step S2, the calcination temperature is 240-320℃, the heating rate is 2-8℃ / min, and the reaction time is 5-30min.

2. The molten salt method nano-tin phosphide composite graphene anode material according to claim 1, characterized in that, In step S1, the method for preparing the graphene oxide includes the following steps: (1) Add graphite sheets and sodium nitrate to a container containing concentrated sulfuric acid placed in an ice bath and stir; (2) Add KMnO4 to the container and continue stirring; (3) Transfer the container to a water bath and stir at 20-50 ℃; (4) Add ultrapure water droplets into the container to lower the solution temperature to below 40°C; (5) Transfer the container to an oil bath at 95-100℃ and keep stirring vigorously for 20-40 minutes. Then add ultrapure water and H2O2 continuously at room temperature to obtain GO solution. (6) After centrifuging the GO solution, dialyze it until the pH value is close to neutral to obtain a concentrated GO solution. Then, vacuum dry the GO solution at 80°C.

3. A battery containing the molten salt method nano-tin phosphide composite graphene material as described in claim 1 or 2.

4. The battery as described in claim 3, characterized in that... Its preparation method includes the following steps: A. Weigh out nano-tin phosphide composite graphene material, acetylene black and sodium alginate, add an appropriate amount of distilled water, mix well, grind and stir into a paste, and coat it on copper foil; B. The copper foil coated in step A is dried, sliced, assembled, and pressed to obtain the battery.

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