Sn4P3 composite tin elemental electrode material, and preparation method and application thereof

Abstract

The application discloses a kind of electrode material of tin phosphide composite tin element and its preparation method and application, belong to battery material technical field.Salt and graphene oxide are mixed, and precursor Sn6O4 (OH) 4 / GO is obtained by reacting with alkaline solution;Sn6O4 (OH) 4 / GO and NaH2PO2·H2O are 1:10 mass ratio, in inert atmosphere, with 5 ℃ / min speed to 500 ℃ calcination 3 h, and Sn / Sn4P3 / RGO is obtained.The application uses Sn6O4 (OH) 4 / GO with low crystallinity, rich hydroxyl and rich defect as reactive precursor, by controlling the amount of phosphorus source, phosphorization temperature and heating rate, tin element and tin phosphide form in situ in the reduction of graphene oxide conductive network Close heterojunction.The composite material can inhibit tin particle migration, agglomeration, improve electron / ion transport kinetics, suitable for lithium ion battery and sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to an electrode material of tin phosphide composite tin, its preparation method, and its application. Background Technology

[0002] As the global energy transition continues, secondary energy storage batteries have effectively alleviated dependence on fossil fuels and environmental pollution. Lithium-ion batteries, with their stable performance and wide range of applications, dominate the power battery and high-end energy storage fields; sodium-ion batteries, with their abundant resources, low cost, and excellent low-temperature performance, possess unique advantages in large-scale energy storage. Lithium / sodium secondary batteries complement each other and are a core technology for building green energy storage systems. As energy storage devices develop towards higher capacity, faster charging, and longer cycle life, the performance requirements for anode materials in lithium / sodium-ion batteries are constantly increasing. The theoretical specific capacity of traditional graphite anodes is only 372 mA hg. -1 However, these current methods cannot meet the development needs of high-performance and large-scale applications of lithium / sodium batteries. Tin-based anode materials possess advantages such as high theoretical capacity, good conductivity, low cost, and environmental friendliness, exhibiting excellent energy storage performance for both lithium and sodium ions, making them high-potential anode candidates for lithium / sodium ion batteries. However, pure tin anodes undergo drastic volume deformation exceeding 300% during repeated lithium and sodium ion intercalation and deintercalation, easily leading to active material pulverization and shedding, electrode structure collapse, and rapid capacity decay and poor cycle stability, severely limiting their commercial application in lithium / sodium ion batteries.

[0003] Tin-based materials can undergo alloying reactions with lithium or sodium ions, possessing advantages such as high theoretical capacity, good conductivity, relatively abundant resources, and environmental friendliness, making them important candidate systems for lithium / sodium-ion battery anode materials. However, tin-based anodes undergo drastic volume changes during lithium or sodium ion insertion / extraction. Repeated cycling easily leads to active particle pulverization, agglomeration, cracking of the solid electrolyte film on the electrode surface, and detachment from the current collector, resulting in rapid capacity decay and decreased cycle stability. Especially under high-rate charge-discharge conditions, charge transport and ion diffusion resistance increase, and volume stress concentration becomes more pronounced, severely limiting the practical application of tin-based anode materials. Tin phosphide combines excellent lithium / sodium storage activity with ionic conductivity, exhibits good compatibility with tin metal, can construct stable heterojunctions, and the Li3P / Na3P generated by the conversion reaction can effectively inhibit the agglomeration of tin nanoparticles, making it a high-quality modifying material suitable for lithium / sodium dual-cell systems. x P yNanoplate / Reduced Graphene Oxide Composites as Anode Materials for Lithium- / Sodium-Ion Batteries (Zhen Kong, ACS Appl. Nano Mater. 2021, 4, 12335-12345) used NaH2PO2·H2O as the phosphorus source to phosphate Sn / RGO to obtain SnP. 0.94 / RGO and Sn4P3 / RGO composites, but SnP 0.94 The interfacial bonding between / RGO and Sn4P3 / RGO is weak. Existing modification technologies generally suffer from problems such as unreasonable structural design, weak interfacial bonding, and poor modification uniformity, which fail to fully realize the synergistic effect of the two phases and make it difficult to balance fast-charging performance and long-cycle stability. Therefore, how to construct a structurally stable tin phosphide-modified tin metal composite electrode with excellent interfacial bonding, effectively buffer the volume deformation during charge and discharge, improve the electrochemical kinetics and structural stability of the dual system, and enable the material to simultaneously meet the high-speed charging and high-capacity requirements of lithium-ion batteries and the long-cycle energy storage requirements of sodium-ion batteries, is a key technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0004] To address the aforementioned limitations of existing technologies, the present invention aims to provide an electrode material composed of tin phosphide and tin phosphate, along with its preparation method and applications. The invention first prepares a graphene oxide-coated tin oxide nanocomposite precursor, Sn6O4(OH)4 / GO. Then, utilizing the precursor's low crystallinity, high hydroxyl content, high defect content, and high interfacial activity, it undergoes a gas-solid phosphating reduction reaction with phosphorus-containing gas generated from the thermal decomposition of a phosphorus source. This allows tin phosphate and tin phosphide to be generated in situ within the reduced graphene oxide network, forming a tight heterogeneous interface. This composite structure can buffer the volume changes of tin-based materials during lithium / sodium ion intercalation / deintercalation, suppress tin particle migration and aggregation, and improve electron / ion transport kinetics, making it suitable for lithium-ion and sodium-ion battery anode materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing an electrode material of tin phosphide composite tin, comprising the following steps: (1) Add tin salt and graphene oxide to an organic solvent and disperse them evenly to obtain a mixed dispersion; add alkaline solution dropwise to the mixed dispersion, stir the reaction at room temperature, separate, wash and dry to obtain the graphene oxide-coated tin oxide nanocomposite precursor Sn6O4(OH)4 / GO; the organic solvent is anhydrous ethylenediamine or ethylene glycol; (2) Sn6O4(OH)4 / GO and NaH2PO2·H2O were calcined in an inert atmosphere to obtain the electrode material Sn / Sn4P3 / RGO, which is a composite tin phosphide.

[0006] Preferably, in step (1), the tin salt is SnCl2·2H2O or SnCl4·5H2O.

[0007] Preferably, in step (1), the mass ratio of the tin salt, graphene oxide and the alkali contained in the alkaline solution is 8~15:1:2~4; the alkaline solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, sodium borohydride solution or potassium borohydride solution.

[0008] Preferably, in step (1), the dispersion is uniformly dispersed by ultrasonication for 30-60 min; the dropping time is 3-5 min; and the stirring reaction time is 90 min.

[0009] Preferably, in step (1), the separation is performed by centrifuging at 5000 rpm for 3 min; the washing is performed by washing twice with ethanol and then once with deionized water; and the drying is performed by freeze drying for 24 h.

[0010] Preferably, in step (2), the mass ratio of Sn6O4(OH)4 / GO to NaH2PO2·H2O is 1:10.

[0011] Preferably, in step (2), the inert atmosphere is argon; the calcination is performed by heating to 500°C at a heating rate of 5°C / min and calcining for 3 hours.

[0012] In a second aspect, the present invention provides an electrode material of tin phosphide composite tin obtained by the above preparation method, the electrode material comprising elemental tin, tin phosphide and reduced graphene oxide; wherein the elemental tin and tin phosphide form a heterojunction, and the reduced graphene oxide coats the heterojunction; wherein the tin phosphide is Sn4P3.

[0013] A third aspect of the present invention provides the application of tin phosphide composite tin elemental electrode materials in the preparation of lithium-ion batteries or sodium-ion batteries.

[0014] Preferably, the application includes improving the conductivity, lithium storage capacity, sodium storage capacity, electrochemical kinetics, and rate performance of the electrode material.

[0015] The beneficial effects of this invention are: (1) The present invention uses Sn6O4(OH)4 / GO as a reaction precursor. The precursor has a metastable structure with low crystallinity, porous, rich in hydroxyl groups and rich in defects, which can react efficiently with phosphorus-containing gas generated by the thermal decomposition of phosphorus source, which is beneficial to realize the in-situ construction and ratio control of elemental tin and tin phosphide phase.

[0016] (2) This invention enables elemental tin and tin phosphide to form a tight heterogeneous interface at the nanoscale through a gas-solid phosphating reduction reaction, avoiding the problems of insufficient contact and weak interfacial bonding caused by simple mechanical mixing. Elemental tin provides high capacity, while tin phosphide provides ion transport and buffering effects, and the two work together to improve the electrochemical reaction kinetics.

[0017] (3) The present invention utilizes reduced graphene oxide to coat and connect tin-based active particles to form a continuous conductive network, which can improve the electron transport capability of the electrode and buffer volume changes, inhibit the migration and agglomeration of tin particles and the pulverization and shedding of active materials during charging and discharging.

[0018] (4) The process route of the present invention is simple, the raw materials are readily available, the reaction conditions are mild and controllable, it is suitable for extended preparation, and it can simultaneously serve the high-capacity and high-rate applications of lithium-ion batteries and the long-cycle energy storage applications of sodium-ion batteries. Attached Figure Description

[0019] Figure 1 (a) XRD pattern of Sn6O4(OH)4 / GO, (b) XRD pattern of Sn / Sn4P3 / RGO, (c) XRD pattern of SnO2 / RGO, (d) XRD pattern of Sn x P y XRD patterns of Sn / RGO, (e) XRD patterns of Sn / RGO, (f) XRD patterns of composite materials prepared by Sn6O4(OH)4 / GO:NaH2PO2·H2O with different mass ratios. Figure 2 (a) SEM morphology of Sn6O4(OH)4 / GO, (b) SEM morphology of SnO2 / RGO, (c) SEM morphology of Sn / Sn4P3 / RGO, (d) Sn x P y SEM topography of / RGO; Figure 3(a) TEM image of Sn / Sn4P3 / RGO composite material, (b) HR-TEM image of Sn / Sn4P3 / RGO composite material, (c) Selected area electron diffraction pattern of Sn / Sn4P3 / RGO composite material, (d) EDS energy spectrum of Sn / Sn4P3 / RGO composite material, (e) Sn element distribution in Sn / Sn4P3 / RGO composite material, (f) P element distribution, (g) O element distribution, (h) C element distribution, (i) N element distribution; Figure 4 Thermogravimetric analysis diagram of Sn / Sn4P3 / RGO composite material; Figure 5 :Sn / Sn4P3 / RGO, SnO2 / RGO and Sn x P y Raman spectra of RGO composite materials; Figure 6 XPS fine spectra of Sn / Sn4P3 / RGO composites, including (a) high-resolution XPS spectra of Sn3d, (b) high-resolution XPS spectra of P2p, (c) high-resolution XPS spectra of N1s, and (d) high-resolution XPS spectra of C1s. Figure 7 Sn / Sn4P3 / RGO composite material at 0.2 mV s -1 CV curves for the first 5 scan cycles at the specified scan speed; Figure 8 Sn / Sn4P3 / RGO and SnO2 / RGO, Sn / RGO and Sn x P y / RGO composite material at 500 mA g -1 Cyclic performance at current density; Figure 9 Sn / Sn4P3 / RGO and Sn x P y / RGO-3, Sn x P y / RGO-5 and Sn x P y / RGO-15 composite material at 500 mAg -1 Cyclic performance at current density; Figure 10 Rate performance of Sn / Sn4P3 / RGO composite material at different current densities; Figure 11 Sn / Sn4P3 / RGO composite material at 2.0 A g -1 and 5.0 A g -1 Cyclic performance at current density; Figure 12 (a) Impedance curves of Sn / Sn4P3 / RGO and SnO2 / RGO composite materials after cycling; (b) Z' and ω at low frequencies. -1 / 2 A graph showing the relationship between the curves; Figure 13 Sn / Sn4P3 / RGO was used as the anode material for SIBs at 1.0 A g. -1 Cyclic performance at current density; Figure 14 Rate performance of Sn / Sn4P3 / RGO as anode material for SIBs at different current densities. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0021] As introduced in the background section, tin phosphide possesses excellent lithium / sodium storage activity and ionic conductivity, exhibits good compatibility with tin metal, and can construct stable heterogeneous interfaces. Furthermore, the Li3P / Na3P generated by the conversion reaction can effectively inhibit the aggregation of tin nanoparticles, making it a high-quality modifying material suitable for lithium / sodium dual-cell battery systems. However, existing modification technologies generally suffer from problems such as unreasonable structural design, weak interfacial bonding, and poor modification uniformity, failing to fully leverage the synergistic effect of the two phases and making it difficult to balance fast-charging performance and long-cycle stability.

[0022] Based on this, the purpose of this invention is to provide an electrode material composed of tin phosphide and elemental tin, its preparation method, and its application. This invention innovatively utilizes Sn6O4(OH)4 / GO nanocomposite material as a modification precursor. Sn6O4(OH)4 / GO belongs to the tin hydroxyl oxide precursor, exhibiting a low-crystallinity, porous, defect-rich metastable structure. This structure is loose, with high lattice stress and weak stability. It possesses numerous surface hydroxyl groups (–OH), vacancy defects, and unsaturated coordination sites, enabling efficient coordination and bonding reactions with the phosphorus source, facilitating structural and phase control. This provides a theoretical basis for subsequent precise control of the phase composition and proportion of the electrode material. By modifying Sn6O4(OH)4 / GO through a phosphating process, Sn6O4(OH)4 / GO can be transformed into an electrode material with elemental tin as the main phase. Introducing a small amount of tin phosphide is a strategy to utilize the synergistic effect of multiple phases to alleviate the volume expansion effect of tin-based electrode materials, thereby improving the rate performance and long-cycle performance of tin-based electrode materials. Specifically, using Sn6O4(OH)4 / GO nanocomposite materials as precursors allows for the full utilization of the structural defects of Sn6O4(OH)4 to achieve structural and compositional control during subsequent modification. Modifying the synthesis process during phosphating modification allows for control over the phase composition and proportion of the reaction products. Leveraging the metallic / semiconductor stable phase properties of tin phosphide, a tight lattice-matched interface is formed with elemental tin, and strong electronic coupling inhibits tin grain migration and agglomeration. Simultaneously, utilizing the heterostructure between the two materials, the built-in electric / strain field at the heterostructure interface reduces the Li... + / Na + The desolvation barrier and solid-phase diffusion resistance accelerate ion transport kinetics and enhance electrochemical performance. Furthermore, tin phosphide generates Li3P / Na3P during discharge, which can serve as a flexible ion-conducting matrix, allowing for plastic deformation, dispersing local stress, buffering the volume abrupt changes during tin alloying, and preventing particle cracking. The graphene-coated structure, combined with multi-phase composites and heterogeneous structures, significantly increases the active sites of the electrode material, while effectively mitigating volume expansion during energy storage and enhancing structural stability, potentially leading to high-rate, long-cycle life for lithium / sodium-ion batteries.

[0023] Research has revealed that Sn / Sn x P y The successful preparation of / RGO stems from two aspects: firstly, the control of the mass ratio of Sn6O4(OH)4 / GO to NaH2PO2·H2O; and secondly, the control of calcination parameters. Specifically, different products are obtained by varying the mass ratio of Sn6O4(OH)4 / GO to NaH2PO2·H2O, as well as by changing the heating rate and decreasing the calcination temperature. When the mass ratio of Sn6O4(OH)4 / GO to NaH2PO2·H2O is 1:10, and the calcination temperature is 5℃·min... -1The product was calcined at a heating rate of 500 °C. Sn elemental occupied the main phase, accelerating particle transport. However, Sn elemental was prone to agglomeration. The introduction of a small amount of Sn₄P₃ into the product generated Li₃P / Na₃P during discharge, which served as a flexible ion-conducting matrix, inhibiting tin grain migration and agglomeration. Furthermore, Sn elemental and Sn₄P₃ could form a heterojunction, resulting in stronger interfacial bonding. This improved the conductivity of the electrode material and exhibited high charge-discharge specific capacity, excellent rate performance, and high-rate, long-cycle stability.

[0024] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0025] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0026] Example 1: Preparation of Sn / Sn4P3 / RGO (1) Add 0.45 g of stannous chloride dihydrate (SnCl2·2H2O) and 40 mg of graphene oxide sequentially to a beaker containing 30 mL of anhydrous ethylenediamine, and sonicate for 30 min until completely dispersed to obtain a mixed solution. Add 0.12 g of potassium hydroxide to a beaker containing 30 mL of deionized water, and stir until completely dissolved to obtain an alkaline solution. Add the alkaline solution dropwise to the mixed solution, and stir the reaction at room temperature for 90 min. After the reaction is complete, centrifuge at 5000 rpm for 3 min to separate the precipitate. Wash the precipitate twice with ethanol, then wash it once with deionized water, and freeze-dry it at -80℃ for 24 h to obtain the Sn6O4(OH)4 / GO precursor.

[0027] (2) Sn6O4(OH)4 / GO and NaH2PO2·H2O were placed in two different positions on an alumina ceramic boat at a mass ratio of 1:10, and then placed in a tube furnace under an argon atmosphere and heated at 5 °C·min. -1 The temperature is increased to 500℃ at a heating rate, and the phosphating treatment is carried out for 3 hours. After natural cooling, the phosphating modified composite material Sn / Sn4P3 / RGO can be obtained.

[0028] Comparative Example 1: Preparation of SnO2 / RGO The difference from step (2) of Example 1 is that Sn6O4(OH)4 / GO is placed alone under an argon atmosphere and heated at 5°C·min. -1 The SnO2 / RGO composite material can be obtained by heating the temperature to 500 ℃ at a heating rate, holding it at that temperature for 3 h, and then allowing it to cool naturally.

[0029] Comparative Example 2: Sn x Py / RGO preparation The difference from Example 1 is that: at 1 °C·min -1 The heating rate was increased to 350 °C, and the phosphating modified composite material Sn was finally obtained. x P y / RGO.

[0030] Comparative Example 3: Preparation of Sn / RGO The difference from Example 1 is that the temperature was raised to 550 °C, and the final result was the phosphating modified composite material Sn / RGO.

[0031] Comparative Example 4 The difference from step (2) of Example 1 is that the mass ratio of Sn6O4(OH)4 / GO to NaH2PO2·H2O is 1:3, 1:5, and 1:15. Three composite materials were finally prepared, denoted as Sn6O4(OH)4 / GO and NaH2PO2·H2O, respectively. x P y / RGO-3、Sn x P y / RGO-5 and Sn x P y / RGO-15.

[0032] Example 2: Characterization (1) Figure 1 The Sn6O4(OH)4 / GO prepared in step (1) of Example 1, the Sn / Sn4P3 / RGO prepared in Example 1, the SnO2 / RGO prepared in Comparative Example 1, and the Sn prepared in Comparative Example 2 are as follows: x P y XRD patterns of Sn / RGO prepared in Comparative Example 3, and the nanocomposites prepared in Comparative Example 4 with different mass ratios of Sn6O4(OH)4 / GO:NaH2PO2·H2O were obtained. The testing apparatus used was a Bruker D8 Advance X-ray diffractometer (Cu target, λ=1.5406Å). Comparison with the standard card shows that Sn6O4(OH)4 / GO can be successfully prepared in Example 1. Figure 1 In section (a), the successful synthesis of the hydroxytin oxide precursor laid the foundation for subsequent modification. Figure 1 (b) shows the XRD pattern of Sn / Sn4P3 / RGO. Under the process conditions of Example 1, NaH2PO2·H2O is decomposed into PH3 gas upon heating. PH3 further undergoes a redox reaction with Sn6O4(OH)4 / GO, which can prepare a composite material with elemental tin as the main phase and Sn4P3 as the auxiliary phase. This can fully leverage the advantages of both phases to improve the electrochemical performance of the composite material. Figure 1(c) shows the XRD pattern of the SnO2 / RGO composite material; Figure 1 In the middle (d), Sn x P y XRD pattern of / RGO, Sn x P y / RGO composite materials with Sn4P3 and SnP 0.94 The mixed phase is dominant. Compared with Sn / Sn4P3 / RGO, it can be seen that the heating rate has a significant impact on the phase composition of the product. Figure 1 In the middle (e), the XRD pattern of the Sn / RGO composite material is shown. Compared with Sn / Sn4P3 / RGO, it can be seen that the calcination temperature during the phosphating process has a significant impact on the phase composition of the product. Figure 1 Figure (f) shows the XRD patterns of composite materials prepared by Sn6O4(OH)4 / GO and NaH2PO2·H2O at different mass ratios. As can be seen from the figure, when the material ratio is 1:3, the product is mainly Sn. When the ratio becomes 1:5, in addition to the Sn phase, a phase that is suspected to be a phosphide begins to appear. When the ratio is increased to 1:15, the main phase is completely dominated by phosphides. The above results indicate that the phase of the product can be controlled by adjusting the proportion of phosphorus source.

[0033] (2) Figure 2 The Sn6O4(OH)4 / GO prepared in step (1) of Example 1, the Sn / Sn4P3 / RGO prepared in Example 1, the SnO2 / RGO prepared in Comparative Example 1, and the Sn prepared in Comparative Example 2 are as follows: x P y SEM morphology images of / RGO. The testing equipment used was a ZESSIS Sigma 300 field emission scanning electron microscope (SEM). (The image was obtained through...) Figure 2 The SEM image in (a) reveals that the Sn6O4(OH)4 / GO composite material exhibits a graphene-coated structure with obvious wrinkles and varying particle sizes. Figure 2 Although the SnO2 / RGO composite material in (b) still maintains the graphene-coated structure, some SnO2 nanoparticles are exposed on the surface and are severely agglomerated. Figure 2 The Sn / Sn4P3 / RGO composite material in (c) exhibits a graphene-coated, uniformly sized nanoparticle structure with obvious wrinkles, presenting a three-dimensional structure. This structure is beneficial for alleviating the volume expansion of tin-based materials and accelerating the ion transport rate. Figure 2 Sn in (d) x P y The / RGO composite material exhibits a denser structure, with tin-based phosphide nanoparticles anchored on the graphene matrix.

[0034] (3) Figure 3TEM images, selected area diffraction patterns, and elemental energy dispersive spectroscopy (EDS) spectra of the Sn / Sn4P3 / RGO composite material prepared in Example 1 are shown. The TEM was performed using a Thermo Fisher Scientific Talos F200X S transmission electron microscope (TEM). The EDS was performed using an energy-dispersive X-ray spectroscopy (EDS, Horiba EMAX energy EX-350) integrated into the SEM. Figure 3 The TEM image in (a) shows that the Sn / Sn4P3 / RGO composite material is a graphene-coated nanoparticle structure. Most of the nanoparticles are uniform in size and distributed evenly, with only a few nanoparticles being larger in size. Figure 3 In (b), it can be further observed that the Sn / Sn4P3 / RGO composite material contains lattice fringes with interplanar spacing of 0.29 nm and 0.32 nm, which correspond to the (200) crystal plane of Sn and the (014) crystal plane of Sn4P3, respectively. Figure 3 Six different lattice fringes can be observed in the selected area electron diffraction pattern in (c), which correspond to the (220) and (101) crystal planes of Sn elemental, and the (104), (101), (009) and (006) crystal planes of Sn4P3, indicating that the composite phase material was successfully synthesized. Figure 3 (d) Figure 3 In Figure (i), the energy dispersive spectroscopy (EDS) results of the composite material show that the five elements tin, phosphorus, oxygen, carbon, and nitrogen are evenly distributed, proving that the Sn / Sn4P3 / RGO composite material has a uniform elemental distribution.

[0035] (4) Figure 4 The TGA spectrum of the Sn / Sn4P3 / RGO composite material prepared in Example 1 was obtained using a NETZSCH STA 449 F3 experimental setup. The results show that the Sn / Sn4P3 / RGO composite material experiences mass loss below 350°C, which can be attributed to the evaporation of adsorbed water and the combustion reaction of reduced graphene oxide. Above 400°C, the mass gradually increases, then stabilizes, and finally decreases slightly. The increase in mass can be attributed to the oxidation of elemental Sn to SnO2 and the conversion of Sn4P3 to SnO2 and P2O5. The subsequent decrease can be attributed to the reduction reaction of the SnO2 product at high temperatures, converting it back to elemental Sn.

[0036] (5) Figure 5 Sn / Sn4P3 / RGO prepared in Example 1, SnO2 / RGO prepared in Comparative Example 1, and Sn prepared in Comparative Example 2 x P yRaman spectra of / RGO were obtained using an Andor SR-500i excitation device at 532 nm. It can be seen that the prepared SnO2 / RGO, Sn / Sn4P3 / RGO, and Sn... x P y / RGO composite material I D / I G The values ​​were 1.17, 1.11, and 1.09, respectively, indicating that although the phases of the products prepared by different processes were different, I D / I G The ratios showed no significant difference, indicating that various preparation conditions only slightly altered local defects and did not significantly damage the overall sp of RGO. 2 The carbon skeleton structure does not affect the RGO's ability to improve ion transport efficiency during energy storage.

[0037] (6) Figure 6 The high-resolution XPS spectra of Sn3d, P2p, N1s, and C1s of the Sn / Sn4P3 / RGO composite material prepared in Example 1 were obtained using a Thermo Fisher Scientific ESCALAB QXI instrument. Figure 6 As shown in (a), the Sn / Sn4P3 / RGO sample has two peaks at 487.7 eV and 496.2 eV, corresponding to the Sn3d phase of tin, respectively. 5 / 2 and Sn3d 3 / 2 The orbital, while the two weak peaks at 485.6 eV and 493.9 eV correspond to zero-valent tin. Figure 6 Image (b) shows the P2p energy spectrum of Sn / Sn4P3 / RGO, with the peaks at 132.6 eV and 133.3 eV attributed to the P2p of the tin-phosphorus bond, respectively. 3 / 2 With P 2p 1 / 2 The characteristic peaks confirm the presence of tin phosphide; the peak at 138.7 eV corresponds to the surface oxide of pentavalent phosphorus, which is due to the oxidation of phosphorus with incomplete passivation on the sample surface in the air. Figure 6 Figure 6(c) shows the N1s spectrum of Sn / Sn4P3 / RGO. The three peaks at 397.5 eV, 399.6 eV, and 406.6 eV can be attributed to graphitic nitrogen, pyrrole nitrogen, and pyridine nitrogen, respectively. Figure 6(d) shows the C1s spectrum of Sn / Sn4P3 / RGO, which contains C=C (284.8 eV) and C–O bonds (285.6 eV). These functional groups originate from the graphene substrate and are of great significance for improving the conductivity of the material.

[0038] Test Example: Performance Testing The composite materials prepared in Example 1 and Comparative Examples 1-3 were used to fabricate button batteries, and their performance was tested. Specifically, the composite materials prepared in Example 1 or Comparative Examples 1-3 were used as active materials. Acetylene black and polyvinylidene fluoride were mixed uniformly at a mass ratio of 80:10:10. N-methyl-2-pyrrolidine (NMP) was added dropwise as a solvent to obtain an electrode slurry, ideally just enough to flow. The electrode slurry was uniformly coated onto copper foil cleaned with alcohol using a coater. After pre-drying, it was vacuum dried at 110°C for 12 hours. After naturally cooling to room temperature, it was cut to obtain electrode sheets with a diameter of 12 mm and an active material loading of 0.8-1.2 mg per electrode sheet.

[0039] When using the above electrode sheet as the negative electrode material for LIBs, the electrolyte used is 1M LiPF6, which contains EC:DMC:EMC (1:1:1, wt%), 2.0% FEC, a polypropylene membrane (Celgard 2320) is used as the separator, and a pure lithium metal sheet is used as the counter electrode. When the above electrode sheet is used as the negative electrode material for SIBs, the electrolyte used is 1M NaClO4, in which EC:DEC (1:1, wt%), containing 5.0% FEC, glass fiber (Whatman GF / D) is used as the separator, and pure sodium metal sheet is used as the counter electrode.

[0040] 2032-type button cells were assembled in a glove box filled with Ar atmosphere (oxygen and moisture less than 1 ppm) using metal springs and spacers. Charge-discharge tests were performed using a NEWARE battery measurement system with a cutoff voltage range of 3V to 0.01V, and the specific capacity was calculated based on the total mass of the active material.

[0041] (1) Electrochemical behavior test when used as a negative electrode of LIBs The Sn / Sn4P3 / RGO composite material prepared in Example 1 was tested at 0.2 mV s. -1 The first 5 cycles of CV curves at the scan rate, using a Chenhua 760E electrochemical workstation. Figure 7As shown, during the initial discharge cycle, the peak at 1.45 V originates from the formation of the solid electrolyte interphase (SEI) film. The two peaks at 1.05 V and 0.52 V correspond to the lithiation reaction of the Sn / Sn4P3 / RGO composite material, while the peak below 0.35 V is generated by the alloying reaction. During the initial charge cycle, the peaks at 0.56 V and 0.83 V are due to the dealloying reaction, and the peak at 1.14 V is due to the reversible formation of the Sn / Sn4P3 / RGO composite material. Due to the formation of the SEI film, the lithiation / delithiation peaks shift slightly after the first cycle. At the start of the second cycle, the CV curves show high overlap, indicating that the Sn / Sn4P3 / RGO composite material exhibits stable electrochemical performance and good cycle stability during charge-discharge cycling.

[0042] (2) Cyclic stability test when used as the negative electrode of LIBs Figure 8 The Sn / Sn4P3 / RGO composite material prepared in Example 1, the SnO2 / RGO prepared in Comparative Example 1, and the Sn prepared in Comparative Example 2 are all examples of such composite materials. x P y Cycling performance curves of Sn / RGO and Sn / RGO prepared in Comparative Example 3 were obtained. The testing apparatus was a Xinwei charge-discharge tester with a current density of 0.5 A / g and a voltage range of 0.01-3.0 V. As shown in Figure 8, the specific capacity of Sn / Sn4P3 / RGO was significantly higher than that of the other three comparative samples in the initial stage of cycling, proving that this material has superior initial lithium storage performance. The reason for this is that, on the one hand, the unique structure of the three-dimensional graphene-coated nanoparticles can effectively accelerate lithium-ion diffusion; on the other hand, Sn and Sn4P3 in the system produce a synergistic effect, providing abundant active sites for the lithium storage reaction. During long-term cycling, the specific capacity of SnO2 / RGO decayed significantly. The root cause is that the electrode structure is easily damaged, and a large amount of active material is lost. After 200 cycles, the specific capacity was only 557 mAh / g. Similarly, the capacity decay of Sn / RGO was also rapid. After 105 cycles, the capacity decreased from 1511.0 mAh / g in the first cycle to 616.7 mAh / g. x P yThe capacity of / RGO is relatively stable, maintaining 829.4 mAh / g after 150 cycles. In contrast, the capacity decay of Sn / Sn4P3 / RGO is gradual, remaining stable at 1125 mAh / g after 200 cycles, indicating that phosphating modification can significantly improve the cycling stability of the composite material. The coulombic efficiency of the Sn / Sn4P3 / RGO composite material is 62% in the first cycle, increasing to 91% in the second cycle, and further reaching 94% in the third cycle. The gradual recovery of coulombic efficiency is mainly due to the gradual activation of the electrode and the sufficient wetting of the electrode interface by the electrolyte, which also confirms that the Sn / Sn4P3 / RGO electrode possesses stable lithium storage characteristics.

[0043] Figure 9 The Sn / Sn4P3 / RGO composite material prepared in Example 1 and the Sn prepared in Comparative Example 4 are presented. x P y / RGO-3, Sn x P y / RGO-5 and Sn x P y The cycle performance curves of / RGO-15 were obtained using a Xinwei charge-discharge tester with a current density of 0.5 A / g and a voltage range of 0.01-3.0 V. Figure 9 It can be seen that Sn x P y / RGO-3 only maintains a capacity of 458.0 mAh / g after 100 cycles, while Sn x P y / RGO-5 maintains a capacity of 625.3 mAh / g after 100 cycles, Sn x P y After 160 cycles, / RGO-15 achieved a capacity of 833.3 mAh / g. Although this is slightly lower than the capacity of Sn / Sn4P3 / RGO (1125 mAh / g), it shows that the capacity gradually increases with phosphating. The electrode material exhibits optimal cycling performance when the phosphating ratio is 1:10. These results fully demonstrate that Sn4P3 modification of elemental Sn can effectively improve the electrochemical performance of electrode materials.

[0044] (3) Rate performance test when used as the negative electrode of LIBs Figure 10The rate performance curves for the Sn / Sn4P3 / RGO composite material prepared in Example 1 show the rate discharge performance of the electrode material at different current densities ranging from 0.2 to 20.0 A / g. The curves clearly show that the average discharge specific capacity of Sn / Sn4P3 / RGO reaches 1209, 921, 849, 789, 651, 503, and 312 mAh / g at current densities of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 20.0 A / g, respectively. When the current density returns to 0.2 A / g, the specific capacity recovers to 997.2 mAh / g, indicating that the Sn / Sn4P3 / RGO composite material possesses excellent rate performance. This superior performance stems from the stable three-dimensional conductive network formed internally after phosphating modification. In addition, the synergistic effect between metal Sn and Sn4P3 can effectively buffer the volume expansion effect during charging and discharging, thereby significantly optimizing the overall electrochemical kinetics and rate lithium storage capacity of the material.

[0045] (4) High-current long-cycle stability test when used as the negative electrode of LIBs Figure 11 The Sn / Sn4P3 / RGO composite material prepared for Example 1 was subjected to a reaction at 2.0 A g. -1 and 5.0 A g -1 Cyclic performance at current density. The graph shows that Sn / Sn4P3 / RGO at 2.0 A g... -1 It can stably cycle for 1000 cycles at current density, maintaining a capacity of 676.2 mA hg. -1 , at 5.0 Ag -1 After 1000 cycles at the current density, the capacity still remains at 388.1 mAh g. -1 The above results indicate that the graphene-coated structure obtained by phosphating modification, in conjunction with the Sn and Sn4P3 multiphase composite strategy, can effectively improve the cycle stability and high-rate performance of the electrode material. The nanostructure and multiphase composite structure constructed by phosphating modification play an extremely important role in stabilizing the electrode structure, increasing active sites, and improving lithium-ion transport efficiency.

[0046] (5) Electrochemical impedance spectroscopy when used as the negative electrode of LIBs Figure 12 When the SnO2 / RGO prepared in Comparative Example 1 and the Sn / Sn4P3 / RGO composite material prepared in Example 1 are used as anode materials, at 0.5 A g -1 EIS impedance spectrum after 200 cycles at current density and corresponding Z' and ω in the low-frequency region -1 / 2 A graph showing the relationship between the curves. Figure 12The EIS impedance curve shown in (a) shows that the Sn / Sn4P3 / RGO electrode exhibits a minimum impedance semicircle after cycling, indicating that the charge transfer resistance is minimal during charge and discharge. Figure 12 Z' and ω shown in (b) -1 / 2 The curve relationship graph shows that the slope of the fitted curve for the Sn / Sn4P3 / RGO electrode is 43.1, which is much smaller than the slope of 58.9 for the SnO2 / RGO electrode. Based on the negative correlation between the ion diffusion coefficient and the slope value, the Sn / Sn4P3 / RGO electrode exhibits the fastest ion diffusion rate. This is attributed to the fact that the phosphating-modified nanostructure synergistic multi-phase composite and graphene coating structure effectively improve the structural stability of the electrode material and reduce the ion transport barrier.

[0047] (6) Cyclic performance test when used as the negative electrode of SIBs Cyclic performance curves of the Sn / Sn4P3 / RGO composite material prepared in Example 1 as the anode material for SIBs were obtained. The testing apparatus was a Xinwei charge-discharge tester with a current density of 1.0 A g. -1 The voltage range is 0.01-3.0 V. As shown in Figure 13, the initial cycling stage is at 200 mA g. -1 After 10 cycles at the current density, the discharge / charge specific capacity of the first cycle was 947.2 / 480.5 mA hg. -1 The capacity loss stems from the formation of the solid electrolyte and electrolyte side reactions. Starting from cycle 11, the current density is adjusted to 1.0 A g. -1 The discharge / charge specific capacities are 372.6 / 349.9 mA hg, respectively. -1 The corresponding coulombic efficiency is 93.9%, demonstrating the material's excellent reversibility. After 200 cycles, the specific capacity remains at 180.6 mA hg. -1 The corresponding coulombic efficiency is 98.7%, indicating that the Sn / Sn4P3 / RGO electrode has excellent sodium storage characteristics.

[0048] (7) Rate performance test when used as the negative electrode of SIBs The rate performance of Sn / Sn4P3 / RGO prepared in Example 1 as the SIBs anode material was tested in the range of 0.2–10.0 A g. -1 Discharge performance at different current densities. Figure 14 As can be clearly seen from the curves, Sn / Sn4P3 / RGO at 0.2, 0.5, 1.0, 2.0, 5.0, and 10.0 Ag... -1 At different current densities, the average discharge specific capacity reached 547.3, 381.9, 345.3, 256.8, 179.4, and 129.2 mA hg, respectively.-1 When the current density recovers to 0.2 A g -1 At that time, the specific capacity increased to 437.7 mA hg -1 The above results indicate that Sn / Sn4P3 / RGO exhibits excellent rate performance. This is attributed to the formation of a stable three-dimensional conductive network within the electrode material after phosphating modification. The nano-particle size, combined with the heterojunction effect between metallic Sn and Sn4P3, enhances the electrochemical kinetics and rate performance of the electrode material.

[0049] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrode material composed of tin phosphide and elemental tin, characterized in that, The electrode material includes elemental tin, tin phosphide, and reduced graphene oxide; the elemental tin and tin phosphide form a heterojunction, and the reduced graphene oxide coats the heterojunction; the tin phosphide is Sn4P3; The electrode material is prepared by the following method: (1) Add tin salt and graphene oxide to an organic solvent and disperse them evenly to obtain a mixed dispersion; add alkaline solution dropwise to the mixed dispersion, stir the reaction at room temperature, separate, wash and dry to obtain the graphene oxide-coated tin oxide nanocomposite precursor Sn6O4(OH)4 / GO; the organic solvent is anhydrous ethylenediamine or ethylene glycol; (2) Sn6O4(OH)4 / GO and NaH2PO2·H2O were placed separately and calcined in an inert atmosphere to obtain the electrode material Sn / Sn4P3 / RGO of tin phosphide composite tin; the mass ratio of Sn6O4(OH)4 / GO to NaH2PO2·H2O was 1:10; the inert atmosphere was argon; the calcination was carried out by heating to 500℃ at a heating rate of 5℃ / min and calcining for 3 h.

2. The electrode material according to claim 1, characterized in that, In step (1), the tin salt is SnCl2·2H2O or SnCl4·5H2O.

3. The electrode material according to claim 1, characterized in that, In step (1), the mass ratio of the tin salt, graphene oxide and the alkali contained in the alkaline solution is 8~15:1:2~4; the alkaline solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, sodium borohydride solution or potassium borohydride solution.

4. The electrode material according to claim 1, characterized in that, In step (1), the dispersion is uniform by ultrasonication for 30-60 min; the dropping time is 3-5 min; and the stirring reaction time is 90 min.

5. The electrode material according to claim 1, characterized in that, In step (1), the separation is performed by centrifuging at 5000 rpm for 3 min; the washing is performed by washing twice with ethanol and then once with deionized water; and the drying is performed by freeze drying for 24 h.

6. The use of the electrode material according to any one of claims 1 to 5 in the preparation of lithium-ion batteries or sodium-ion batteries.

7. The application according to claim 6, characterized in that, The applications include improving the conductivity, lithium storage capacity, sodium storage capacity, electrochemical kinetics, and rate performance of electrode materials.

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