Three-dimensional Si (at) FeSe (at) C nanosphere structure material, preparation method thereof and application of three-dimensional Si (at) FeSe (at) C nanosphere structure material in lithium ion battery negative electrode and liquid / all-solid-state battery

Abstract

The invention provides a three-dimensional Si (at) FeSe (at) C nanosphere structure material, a preparation method thereof and application of the three-dimensional Si (at) FeSe (at) C nanosphere structure material in a lithium ion battery negative electrode and a liquid / all-solid-state battery, compared with the prior art, porous Si and an iron source are subjected to reaction and selenylation, then a carbon layer is coated, and the Si (at) FeSe (at) C composite material of a three-dimensional porous structure is obtained. The porous structure effectively relieves the problem of volume expansion, so that the battery has better stability. The FeSe intermediate layer constructs an efficient electron transport network by virtue of metalloid high conductivity, and meanwhile, the strong mechanical property of the FeSe intermediate layer is combined with a closer interface of the silicon core, so that the volume expansion is greatly inhibited, and the structural integrity is maintained; in addition, the lithium ion diffusion kinetics is obviously improved by selenium vacancies easily formed at the interface; the structure has excellent rate capability while realizing high specific capacity, and the iron-based material is low in cost and has more commercial potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon negative electrode materials of lithium ion batteries, and particularly relates to a three-dimensional Si@FeSe@C nanosphere structure material, a preparation method thereof and application of the material in lithium ion battery negative electrodes and liquid-state / full-solid-state batteries. BACKGROUND

[0002] With the increasing demand for high energy density of electric vehicles and portable electronic devices, the development of high-performance lithium ion battery negative electrode materials has become a key. The traditional commercial graphite negative electrode (theoretical specific capacity of about 372 mAh g -1 ) has been difficult to meet the requirements. Silicon is considered as a potential next-generation negative electrode material due to its extremely high theoretical specific capacity and low operating potential, and has attracted great attention. However, the silicon-based negative electrode will undergo significant volume expansion (> 300%) during the charging and discharging process, which leads to repeated rupture and regeneration of the SEI film, continuous consumption of active lithium and electrolyte. At the same time, the huge stress will cause the pulverization, cracking and peeling failure of the electrode material particles and the current collector. In addition, the low conductivity of silicon itself seriously limits the transmission rate of lithium ions and electrons, significantly degrading the rate performance and cycle stability of the battery. These problems greatly restrict the practical application of the silicon negative electrode.

[0003] At the same time, the liquid electrolyte system commonly used in traditional lithium ion batteries also has obvious shortcomings. The liquid electrolyte has the risk of leakage, which not only may damage the battery performance, but also is more likely to cause short circuit, fire and even explosion in special use scenarios such as high temperature environment and external force impact. In addition, the ionic conductivity of the liquid electrolyte and its stability with the electrode interface are limited, which is not conducive to the further improvement of the overall charging and discharging performance of the battery, and affects the endurance and reliability of the terminal device.

[0004] In recent years, in order to solve the inherent defects of silicon negative electrode materials and the safety and performance bottlenecks brought by traditional liquid electrolyte, full-solid-state battery technology has gradually become a research hotspot. This technology fully replaces the liquid electrolyte with a solid-state electrolyte, aiming to utilize the excellent mechanical strength of the solid-state electrolyte to inhibit the volume expansion of the silicon negative electrode, higher intrinsic safety, and potentially wider electrochemical window and better interface stability, thereby opening up a new path for the development of high-performance silicon negative electrode lithium ion batteries. SUMMARY

[0005] The purpose of the application is to provide a three-dimensional Si@FeSe@C nanosphere structure material and a preparation method thereof. The application utilizes SiO2 small balls to obtain porous Si through a magnesium hot reduction method, then reacts with an iron source through a hydrothermal method, and then selenizes to obtain Si@FeSe, and finally calcines a carbon layer to obtain a Si@FeSe@C composite material.

[0006] Another objective of this invention is to provide an application of a three-dimensional Si@FeSe@C nanosphere structure material in lithium-ion battery anodes and liquid / all-solid-state batteries. The three-dimensional Si@FeSe@C nanosphere structure material is used to prepare lithium-ion battery anodes, which can then be used to prepare liquid batteries or all-solid-state batteries.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for preparing a three-dimensional Si@FeSe@C nanosphere structure material includes the following steps:

[0009] 1) Add the iron source to water and mix, then add porous Si, disperse by ultrasonication, heat and react, mix the resulting product with selenium powder, and calcine to obtain Si@FeSe;

[0010] 2) Coating Si@FeSe with a carbon layer yields a three-dimensional Si@FeSe@C nanosphere structure material.

[0011] In step 1), the ratio of the iron source to water is 0.01-0.015 mol / L, and the ratio of the porous Si to water is 0.01-0.02 mol / L.

[0012] In step 1), the iron source is selected from soluble iron salts, preferably FeCl3·6H2O.

[0013] In step 1), the ultrasonic dispersion takes 1-24 hours.

[0014] In step 1), the size of the porous silicon is 300-500 nm. Using larger porous silicon microspheres is beneficial for subsequent FeSe coating on the surface.

[0015] In step 1), the porous silicon is obtained by using SiO2 microspheres via a magnesothermic reduction method. Preferably, the specific steps are as follows: SiO2 and Mg powder are mixed and ground, then calcined in a hydrogen-argon mixed gas atmosphere. After calcination, the mixture is soaked in HCl solution, filtered, washed, and dried to obtain the desired product. The mass ratio of SiO2 to Mg powder is 1.0-2.5:1, and the calcination conditions are 650℃ for 6 hours. The concentration of the HCl solution is 1-5M, and the soaking time is 3-10 hours. Preferably, the concentration of the HCl solution used is 1M, and the soaking time is 5 hours.

[0016] In step 1), the heating reaction is carried out under the following conditions: temperature 80-180℃ and reaction time 12-30h.

[0017] In step 1), after the heating reaction is completed, the product is cooled to room temperature, separated, washed, and dried to obtain the product, which is then reacted with selenium powder.

[0018] In step 1), the mass ratio of the product to the selenium powder is 1:5.

[0019] In step 1), the calcination conditions are as follows: the atmosphere is a hydrogen-argon mixture, with a volume fraction of 95% argon and 5% hydrogen; the temperature is 500-600℃, and the calcination time is 1-5h; preferably 500℃, and the calcination time is 3h.

[0020] In step 2), the method for coating the carbon layer is as follows: Si@FeSe and tris(hydroxymethyl)aminomethane are dispersed in water, the pH is adjusted to 8-9 with hydrochloric acid solution, dopamine hydrochloride is added, and after the reaction, the resulting product is calcined in a protective atmosphere to obtain the product.

[0021] In step 2), the mass ratio of Si@FeSe to tris(hydroxymethyl)aminomethane is 1:10-15; the amount of Si@FeSe to water is 0.001-0.004 g / mL; the concentration of tris(hydroxymethyl)aminomethane in water is 0.1-0.5 M, and the concentration of dopamine hydrochloride in water is 0.006-0.010 M; the reaction is carried out at room temperature for 20-30 h, preferably 24 h; the calcination is carried out under a nitrogen atmosphere at 500-550 °C for 2-3 h; preferably, the concentration of tris(hydroxymethyl)aminomethane in water is 0.3 M, the pH is adjusted to 8.5, and the concentration of dopamine hydrochloride in water is 0.0095 M; the calcination conditions are 500 °C for 2 h.

[0022] This invention obtains porous Si from SiO2 through thermal reduction of magnesium powder, followed by calcination to obtain a three-dimensional porous Si@FeSe@C composite material. The porous structure effectively alleviates the volume expansion problem, resulting in better battery stability. FeCl3·6H2O is then dissolved in deionized water, and porous silicon is added to the solution. The mixture is then subjected to a hydrothermal reaction in an oven, followed by carbon coating to transform it into a three-dimensional Si@FeSe@C composite material. The porous structure not only increases the specific surface area but also effectively alleviates the volume expansion of silicon particles, thereby improving battery cycle stability.

[0023] In this invention, porous silicon nanoparticles are coated with FeSe, and their spherical structure further increases the specific surface area, finally covered with a thin carbon shell. The conductive network formed by the internal porous and spherical structures provides a rapid electron / ion transport channel, thereby promoting electrode reaction kinetics. Simultaneously, the external carbon shell protects the silicon nanoparticles, buffers the internal voids of the material, and mitigates Li... + The significant volume changes of materials during insertion / extraction ensure the integrity of the electrode structure and can greatly improve the cycle life of the battery.

[0024] Due to severe silicon volume expansion and repeated damage and formation of the SEI film, capacity decay occurs rapidly. To overcome this problem, this invention prepares a composite material, but the preparation process presents challenges: (FeCl3·6H2O dissolved in deionized water undergoes a hydrothermal reaction in an oven to generate FeOOH). The nucleation and growth rate of FeOOH under hydrothermal conditions needs precise control. This invention controls the temperature and time of the hydrothermal reaction in step 1). If nucleation is too rapid, independent FeOOH nanoparticles will be generated instead of heterogeneous nucleation on the silicon surface to form a coating layer. If growth is too rapid, the coating layer will be too thick and uneven. Simultaneously, the target product is FeSe, and excessive selenium powder should be avoided; otherwise, other selenium-rich phases, such as FeSe2 or a mixture of FeSe and FeSe2, are easily generated under high-temperature atmospheres. By nanostructuring the composite material and combining it with a multi-level spatial structure design, its specific surface area and active sites can be synergistically optimized. In this invention, porous silicon particles are synthesized, FeSe is grown on their surface, and finally a carbon layer is coated, effectively improving the battery's capacity and cycle life. At the same time, all-solid-state batteries effectively reduce the safety risks of liquid batteries.

[0025] This invention provides a three-dimensional Si@FeSe@C nanosphere structure material, prepared using the method described above. Spherical porous silicon nanoparticles are coated with FeSe, and their spherical structure further increases the specific surface area. Finally, a thin carbon shell is applied. The size of the three-dimensional Si@FeSe@C nanosphere structure material is 300-500 nm.

[0026] The present invention provides a lithium-ion battery anode, which is prepared using a three-dimensional Si@FeSe@C nanosphere structure material as the active material.

[0027] The present invention provides a liquid battery comprising the above-mentioned lithium-ion battery negative electrode.

[0028] The present invention provides an all-solid-state battery, comprising the above-mentioned lithium-ion battery negative electrode.

[0029] In this invention, the prepared Si@FeSe@C nanomaterials exhibit a well-maintained three-dimensional porous spherical structure in the carbon layer. Meanwhile, FeSe, as a transition metal selenide, possesses high conductivity and a layered buffer structure. Its unique two-dimensional interlayer gaps can accommodate lithium-ion insertion while absorbing the expansion stress of the silicon core through plastic deformation. The chemical bonding between FeSe and the silicon interface enhances interface stability and reduces contact resistance. The synergistic effect of Se vacancies and the heterogeneous interface: During synthesis, the hydroxyl groups in FeOOH on the porous Si surface are reducing agents. These hydroxyl groups possess lone pairs of electrons and are thermodynamically unstable, tending to undergo auto-redox reactions through dehydration. This process inevitably produces reducing Fe... 2+ It acts as a reducing agent to drive Fe3+ To Fe 2+ The valence state transition, producing Fe 2+ Reacts with Se vapor (Fe 2+ + Se 2- →FeSe), in-situ Si@FeSe heterostructures were constructed on porous Si surfaces. Furthermore, the dynamic volatilization of selenium at high temperatures and the kinetic constraints of interfacial ion diffusion led to the formation of selenium vacancies at the FeSe lattice interface. The concentration of selenium vacancies was controlled by the synergistic effect of heterointerfacial reaction kinetics and the selenium atom migration equilibrium, thereby synergistically optimizing structural stability and dual-channel ion / electron transport performance.

[0030] Compared with existing technologies, this invention utilizes three-dimensional Si@FeSe@C nanosphere structures to address the technical challenges of silicon-based materials as electrode materials, such as easy volume expansion and poor cycle stability. It provides a low-cost nanomaterial with synergistic effects of Se vacancies and heterostructures as a solution. The Si@FeSe@C nanocomposite material prepared by this invention is chemically stable, not easily oxidized in air, and easy to store. Due to the presence of Li... + Significant differences in silicon volume before and after insertion / extraction lead to a rapid decrease in capacity. The carbon matrix of this invention shortens the electron / ion path and mitigates the strain caused by volume changes. Since all-solid-state batteries have higher safety and commercial value than liquid batteries, the product of this invention can be used not only in liquid batteries but also in all-solid-state batteries, and has a broader application prospect. Attached Figure Description

[0031] Figure 1 SEM image of the porous Si microspheres prepared in Example 1;

[0032] Figure 2 SEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 1;

[0033] Figure 3 TEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 1;

[0034] Figure 4 XRD pattern of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 1;

[0035] Figure 5 SEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 2;

[0036] Figure 6 SEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 3;

[0037] Figure 7 SEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 4;

[0038] Figure 8 SEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 5;

[0039] Figure 9 SEM image of the three-dimensional porous Si@FeSe@C nanospheres prepared in Example 7;

[0040] Figure 10 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 1 were used as a negative electrode in a lithium-ion battery at 0.1 A g. -1 Charge-discharge curves at current density;

[0041] Figure 11 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 1 were used as a negative electrode in a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0042] Figure 12 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 1 were used as a negative electrode in a lithium-ion battery at 0.5 A g. -1 Charge-discharge curves at current density;

[0043] Figure 13 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 1 were used as a negative electrode in a lithium-ion battery at 0.5 A g. -1 Cyclic performance at current density;

[0044] Figure 14 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 1 were used as a negative electrode in lithium-ion batteries in the range of 0.1-0.5 A g. -1 Rate performance at current density;

[0045] Figure 15 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 2 were used as a negative electrode in a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0046] Figure 16 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 3 were used as a negative electrode in a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0047] Figure 17The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 4 were used as a negative electrode in a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0048] Figure 18 The three-dimensional porous Si@FeSe@C nanomaterials prepared in Example 5 were used as a negative electrode in a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0049] Figure 19 In Example 6, Si particles purchased from Aladdin were used as the negative electrode in a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0050] Figure 20 The FeSe prepared in Example 7 was used as the negative electrode for a lithium-ion battery at 0.1 A g. -1 Cyclic performance at current density;

[0051] Figure 21 The three-dimensional porous Si@MoSe2@C nanomaterials prepared in Example 8 were used as a negative electrode for lithium-ion batteries in the range of 0.1-0.5 A g. -1 Rate performance at current density;

[0052] Figure 22 The Si@FeSe@C prepared in Example 9 was used as the anode of an all-solid-state half-cell at 0.1 A g. -1 Charge-discharge curves at current density;

[0053] Figure 23 The Si@FeSe@C prepared in Example 9 was used as the anode of an all-solid-state half-cell at 0.1 A g. -1 Cyclic performance at current density;

[0054] Figure 24 The FeSe all-solid-state half-cell anode prepared in Example 10 was used at 0.1 A g. -1 Cyclic performance at current density;

[0055] Figure 25 The Si@FeSe@C prepared in Example 11 is used as the anode in an all-solid-state full cell at 0.1 A g. -1 Cyclic performance at current density. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0058] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0059] Unless otherwise specified, the water used in this invention is deionized water. The porous silicon with a size of 300-500 nm is obtained by magnesium thermal reduction of silicon dioxide.

[0060] The battery is prepared during the performance testing of this invention using the following specific method:

[0061] The preparation method of liquid batteries is as follows:

[0062] A three-dimensional Si@FeSe@C nanosphere structure was mixed with a conductive agent and a binder, and then ground to obtain a slurry. This slurry was then stretched and coated onto copper foil. After drying, it was used as the negative electrode of a liquid lithium-ion battery, with a lithium sheet as the counter electrode. The electrolyte was a 1:1 volume ratio of ethylene carbonate (EC) and diethyl carbonate (DEC), and the electrolyte was LiPF6. The liquid lithium-ion battery was assembled in a glove box. The mass ratio of the three-dimensional Si@FeSe@C nanosphere structure to the conductive agent and binder was 7:2:1; the conductive agent was conductive carbon black; the binder was polyvinylidene fluoride; the film stretching was performed on copper foil, and the drying conditions were 60-80℃ for 20-24 hours; after drying, it was cut into small discs.

[0063] The preparation method of the all-solid-state battery is as follows: the three-dimensional Si@FeSe@C nanosphere structure material, conductive agent LPSCl electrolyte and NCM811@LiNbO3 are mixed and compacted in a solid-state battery mold as the negative electrode of the all-solid-state lithium-ion battery, and assembled into an all-solid-state lithium-ion battery in a glove box.

[0064] Example 1

[0065] A method for preparing a three-dimensional Si@FeSe@C nanosphere structure material includes the following steps:

[0066] 1) Preparation of porous Si microspheres:

[0067] Porous Si microspheres were prepared by thermal reduction of SiO2 microspheres with magnesium powder. Specifically, 0.1 g of SiO2 and 0.1 g of Mg powder were mixed and ground for 10 min, then calcined in a hydrogen-argon mixed gas atmosphere (hydrogen volume percentage 5%) at 650 °C for 6 h at a heating rate of 5 °C / min. After calcination, the sample was soaked in 1 M HCl solution for 5 h, and finally washed three times alternately with HCl solution and deionized water. The sample was then dried in a 60 °C oven to obtain porous Si microspheres. The SEM image is shown below. Figure 1 As shown in the figure, it has a porous structure with a size of 300-500 nm. Using larger porous silicon microspheres is beneficial for subsequent FeSe coating on the surface.

[0068] 2) Preparation of porous Si@FeSe@C:

[0069] Under magnetic stirring, 0.54 g of FeCl3·6H2O was dissolved in 200 mL of deionized water, and then 0.1 g of porous Si was added. The mixture was ultrasonically dispersed for 1 h. A hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, separated, washed, and dried to obtain the product, which was then reacted with selenium powder. The resulting product was selenized with Se powder at a mass ratio of 1:5 in a mixed gas atmosphere. The calcination conditions were: a hydrogen-argon mixed gas atmosphere (95% argon + 5% hydrogen by volume), a temperature of 500 °C, and a calcination time of 3 h. 0.1 g of the prepared selenized product was dispersed in 50 mL of deionized water and ultrasonically dissolved for 10 min. Under magnetic stirring, 1.21 g of tris(hydroxymethyl)aminomethane was added to the solution. The pH was then adjusted to 8.5 with hydrochloric acid solution, and 60 mg of dopamine hydrochloride was added. The reaction was carried out at room temperature for 24 h. The composite material was collected and washed multiple times with deionized water and ethanol. The sample was then dried in a 60 °C oven. The dried nanomaterials were calcined at 500℃ in a nitrogen atmosphere for 2 hours at a heating rate of 3℃ / min, finally yielding porous Si@FeSe@C. Its SEM image is shown below. Figure 2 As shown in the image, it can be seen that it is a clustered spherical structure. (TEM image shown). Figure 3 As shown.

[0070] The XRD pattern of the Si@FeSe@C composite material obtained in this embodiment is as follows: Figure 4 As shown, the obtained product is Si@FeSe@C.

[0071] The specific applications of the aforementioned three-dimensional Si@FeSe@C nanosphere structure material in batteries are as follows:

[0072] Liquid lithium-ion battery: The three-dimensional porous Si@FeSe@C composite material obtained in Example 1 was used as the negative electrode of the lithium-ion battery, lithium sheet was used as the counter electrode, and LiPF6 with a volume ratio of ethylene carbonate (EC) and diethyl carbonate (DEC) was used as the electrolyte. The liquid lithium-ion battery was assembled in a glove box.

[0073] All-solid-state battery: The three-dimensional porous Si@FeSe@C composite material obtained in Example 1 was mixed with a conductive agent and an electrolyte to serve as the negative electrode. At the same time, LPSCl electrolyte and Li-In alloy or NCM811@LiNbO3 were added. The mixture was pressed into thin sheets by a tablet press and assembled into an all-solid-state lithium-ion battery in a glove box.

[0074] Example 2 (as a comparison)

[0075] A method for preparing a Si@FeSe@C composite material includes the following steps:

[0076] 1) The preparation of porous Si is the same as in Example 1;

[0077] 2) Preparation of porous Si@FeSe@C:

[0078] Under magnetic stirring, 1.08 g of FeCl3·6H2O was dissolved in 200 mL of deionized water, with other steps the same as in Example 1; the SEM image is shown below. Figure 5 As shown in the figure, it can be seen that it is a clustered spherical structure.

[0079] Example 3 (as a comparison)

[0080] A method for preparing a Si@FeSe@C composite material includes the following steps:

[0081] 1) The preparation of porous Si is the same as in Example 1;

[0082] 2) Preparation of porous Si@FeSe@C:

[0083] Under magnetic stirring, 0.27 g of FeCl3·6H2O was dissolved in 200 mL of deionized water, with other steps the same as in Example 1; the SEM image is shown below. Figure 6 As shown, it is not possible to discern the fabrication process of nanospheres.

[0084] The preparation could not be successfully completed due to the low iron concentration.

[0085] Example 4

[0086] A method for preparing a Si@FeSe@C composite material includes the following steps:

[0087] 1) The preparation of porous Si is the same as in Example 1;

[0088] 2) Preparation of porous Si@FeSe@C:

[0089] Under magnetic stirring, 0.54 g of FeCl3·6H2O was dissolved in 200 mL of deionized water, and then 0.1 g of porous Si was added and dissolved completely by ultrasonication; the reaction was carried out hydrothermally at 80 °C for 30 h; other steps were the same as in Example 1; the SEM image is shown below. Figure 7 As shown. Compared with Example 1, Example 4 increased the reaction time and decreased the temperature, and it was also successfully prepared, but the effect was not as good as that of Example 1.

[0090] Example 5

[0091] A method for preparing a Si@FeSe@C composite material includes the following steps:

[0092] Under magnetic stirring, 0.54 g of FeCl3·6H2O was dissolved in 200 mL of deionized water, and then 0.1 g of porous Si was added and dissolved completely by ultrasonication; the reaction was carried out hydrothermally at 180 °C for 12 h; other steps were the same as in Example 1; the SEM image is shown below. Figure 8 As shown, compared to Example 1, Example 5 reduced the reaction time while increasing the reaction temperature. This was successful, but the effect was not as good as that of Example 1.

[0093] Example 6 (as a comparison)

[0094] A method for preparing porous Si includes the following steps:

[0095] The preparation of porous Si is the same as step 1 in Example 1).

[0096] A comparative experiment was conducted using 0.1g of the prepared porous silicon, and the electrochemical performance of the assembled battery was tested.

[0097] Example 7 (as a comparison)

[0098] A method for preparing FeSe includes the following steps:

[0099] 0.54 g of FeCl3·6H2O was dissolved in 200 mL of deionized water under magnetic stirring, and the mixture was subjected to a hydrothermal reaction at 120 °C for 24 h. Then, it was selenized with Se powder at a mass ratio of 1:5 in a mixed gas atmosphere. The SEM image is shown below. Figure 9 As shown.

[0100] A comparative experiment was conducted using 0.1g of the product, and the electrochemical performance of the assembled battery was tested.

[0101] Example 8 (as a comparison)

[0102] A method for preparing a Si@MoSe2@C composite material includes the following steps:

[0103] 1) The preparation of porous Si is the same as step 1) in Example 1.

[0104] 2) Preparation of porous Si@MoSe2@C:

[0105] Under magnetic stirring, 0.158 g of Se powder was dissolved in 10 mL of hydrazine hydrate, and then a 0.242 g Na2MoO4·2H2O solution was prepared. The two were mixed, and finally 0.1 g of porous silicon was dispersed in the mixed solution. The mixture was subjected to hydrothermal reaction at 200 °C for 24 h. The carbon coating process was the same as in Example 1, and porous Si@MoSe2@C was obtained.

[0106] The materials prepared in Examples 2-8 were used to replace the materials prepared in Example 1, and liquid lithium-ion batteries were fabricated using the same method and their performance was tested.

[0107] Example 9 (as a comparison)

[0108] A Si@FeSe@C material was used for all-solid-state half-cell performance testing. The preparation method of the Si@FeSe@C material was the same as in Example 1, except that the counter electrode was a Li-In alloy during battery testing, and the all-solid-state lithium-ion battery was assembled in a glove box.

[0109] Example 10 (as a comparison)

[0110] A FeSe material was used for all-solid-state half-cell performance testing. The preparation method of the FeSe material was the same as in Example 7, except that the counter electrode was a Li-In alloy during battery testing, and an all-solid-state lithium-ion battery was assembled in a glove box.

[0111] Example 11

[0112] A method for testing the performance of Si@FeSe@C in an all-solid-state full-cell battery was described. The preparation method of the Si@FeSe@C material was the same as in Example 1, except that during battery testing, an all-solid-state lithium-ion battery was assembled in a glove box using NCM811@LiNbO3.

[0113] The assembled lithium-ion batteries were tested for charge-discharge performance using a Newway battery tester. Cycle stability test results at different current densities are as follows: Figures 10-14 As shown, 0.1A g -1 After 50 cycles at the current density, the battery discharge specific capacity is 1189 mAh g. -1 The average charge / discharge efficiency remains above 97%; 0.5A g -1 After 50 cycles at the current density, the battery discharge specific capacity is 926 mAh g. -1The coulombic efficiency remains around 100%. This is true when the current density is between 0.1 and 0.5 A / g. -1 Back to 0.1A g -1 At that time, the battery's discharge specific capacity was still 1248 mAh g. -1 This indicates that it has good reversibility.

[0114] Figures 15-25 The figures show the cycle performance of lithium-ion batteries using the composite materials from Examples 2-11 as the negative electrode. (At 0.1 A g) -1 At different current densities, the lithium-ion batteries assembled from the composite materials synthesized in different embodiments showed discharge specific capacities of 217, 322, 1014, 980, 190, and 207 mAh g⁻¹ after 50 cycles, respectively. -1 It can be seen that Examples 2 and 3 failed because both excessively high and low iron concentrations are detrimental to the subsequent formation of FeSe on the silicon surface. Even when the iron concentration is too high, although the morphology is similar to that of Example 1, the product performance is still relatively poor due to the high Fe concentration. Examples 4 and 5 were successfully prepared, but the final performance was not as good as that of Example 1.

[0115] This invention first obtains porous Si using SiO2 via thermal reduction of magnesium powder, then selenizes it and finally coats it with a carbon layer to obtain a Si@FeSe@C composite material with a three-dimensional structure. The porous silicon nanoparticles combined with FeSe provide a rapid diffusion electron transport channel through the FeSe nanostructure, thereby promoting electrode reaction kinetics. The outermost thin carbon shell alleviates the volume expansion of silicon and also provides support, ensuring the stability of the composite material and significantly improving the cycle stability of the battery. This material can be applied to the anode of liquid and all-solid-state lithium-ion batteries, and the material prepared in Example 1 exhibits better cycle performance and rate performance compared to pure Si and FeSe lithium-ion batteries.

[0116] The performance diagram of the product in Example 8 is as follows. Figure 21 Through rate performance comparison, the performance of Example 8 is significantly lower than that of Example 1. This significant difference is closely related to the structural design and reaction mechanism. Compared with Si@MoSe2@C, the Si@FeSe@C of this invention exhibits superior overall performance. The fundamental reason is that the FeSe intermediate layer, with its metal-like high conductivity, constructs an efficient electron transport network. At the same time, its robust mechanical properties and tighter interface bonding with the silicon core greatly suppress volume expansion and maintain structural integrity. In addition, the selenium vacancies that are easily formed at the interface significantly enhance lithium-ion diffusion kinetics. This structure achieves high specific capacity while possessing superior rate performance, and the iron-based material is inexpensive, making it more commercially viable.

[0117] Figures 22-25 The graph shows the performance of the all-solid-state half-cell, with performance values ​​of 141 and 79 mAh g, respectively. -1 At the same time Figure 25 The performance of the all-solid-state battery is 57 mAh g. -1 .

[0118] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional Si@FeSe@C nanosphere structure material, characterized in that, The preparation method includes the following steps: 1) Add the iron source to water and mix, then add porous Si, disperse by ultrasonication, heat and react, mix the resulting product with selenium powder, and calcine to obtain Si@FeSe; 2) Coating Si@FeSe with a carbon layer yields a three-dimensional Si@FeSe@C nanosphere structure material.

2. The preparation method according to claim 1, characterized in that, In step 1), the ratio of the iron source to water is 0.01-0.015 mol / L, and the ratio of the porous Si to water is 0.01-0.02 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that, In step 1), the heating reaction is carried out under the following conditions: temperature 80-180℃ and reaction time 12-30h.

4. The preparation method according to claim 1 or 2, characterized in that, In step 1), the mass ratio of the product to selenium powder is 1:5, and the calcination conditions are: a hydrogen-argon mixture atmosphere, a temperature of 500-600℃, and a calcination time of 1-5h.

5. The preparation method according to claim 1, characterized in that, In step 2), the method for coating the carbon layer is as follows: Si@FeSe and tris(hydroxymethyl)aminomethane are dispersed in water, the pH is adjusted to 8-9 with hydrochloric acid solution, dopamine hydrochloride is added, and after the reaction, the resulting product is calcined in a protective atmosphere to obtain the product.

6. The preparation method according to claim 1, characterized in that, In step 2), the mass ratio of Si@FeSe to tris(hydroxymethyl)aminomethane is 1:10-15; the concentration of tris(hydroxymethyl)aminomethane in water is 0.1-0.5M, and the concentration of dopamine hydrochloride in water is 0.006-0.010M; the reaction time is 20-30 hours; the calcination is carried out under a nitrogen atmosphere at 500-550°C for 2-3 hours.

7. A three-dimensional Si@FeSe@C nanosphere structure material prepared by the preparation method according to any one of claims 1-6, wherein spherical porous silicon nanoparticles are coated with FeSe and finally coated with a thin carbon shell.

8. A lithium-ion battery anode, prepared using the three-dimensional Si@FeSe@C nanosphere structure material as described in claim 7 as the active material.

9. A liquid battery, characterized in that, Includes the lithium-ion battery negative electrode as described in claim 8.

10. An all-solid-state battery, characterized in that, Includes the lithium-ion battery negative electrode as described in claim 8.

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