Method for preparing si / mxene electrode by solid adhesive bonding coating

Abstract

The application provides a method for preparing a Si / MXene electrode by solid adhesive bonding and coating, and comprises the following steps: preparing porous silicon microspheres; preparing a MXene suspension; embedding MXene in the pores of the porous silicon microspheres to obtain Si / MXene composite powder; coating the Si / MXene composite material with a solid adhesive GS, and compacting the coating layer by using a mold to obtain an electrode sheet; and carbonizing the adhesive layer to finally obtain a Si / MXene@GS three-dimensional structure electrode. In the application, the MXene is combined with micron-sized porous silicon in an embedded manner, and a solid organic adhesive is used as a bonding agent before coating and as a conductive agent after carbonization, so that a more stable and higher-performance Si / MX@GS three-dimensional structure electrode is prepared by a simple method. The process not only avoids a complicated electrode preparation process, but also increases carbon coating on the basis of the MXene embedded three-dimensional structure, and the solid adhesive carbon coating layer which plays a dual role provides effective support for the structural strength of the embedded Si / MXene composite material.

Description

Technical Field

[0001] This invention relates to an electrode material in the field of lithium-ion batteries, and in particular to a method for preparing Si / MXene electrodes by bonding and encapsulating with solid adhesive. Background Technology

[0002] Common graphite-based anode materials for lithium-ion batteries have a relatively low theoretical specific capacity (372 mAh g). -1 The current technology can no longer meet the demands of the rapidly developing market, while silicon materials, due to their high theoretical specific capacity (4200 mAh g), are more suitable. -1 and lower lithium potential (0.37V vs Li / Li) + While silicon possesses significant development potential, it also exhibits substantial volume expansion (>300%) alongside its high theoretical specific capacity. The resulting internal stress not only leads to the pulverization of the active material but can also cause it to detach from the current collector. This severely impacts effective electron and ion conduction within the electrode material, resulting in rapid capacity decay and damage to the solid electrolyte interphase (SEI), consuming a limited amount of electrolyte. In conclusion, the enormous volume effect and semiconductor characteristics limit the commercial application of silicon as a negative electrode material for lithium-ion batteries.

[0003] To mitigate the volume expansion of silicon, minimize internal mechanical stress, and prevent structural breakage, current technologies often employ methods that modify silicon materials at the microstructural level. These methods include nanostructure modification (such as silicon nanowires, silicon nanosheets, and silicon nanospheres), core-shell structures, hollow structures, and porous structures. Furthermore, multidimensional composite materials formed by combining silicon with specific materials in certain ways often possess both excellent electrical conductivity and mechanical properties, thus addressing, to some extent, the scientific and practical problems inherent in silicon itself.

[0004] Patent document CN108183212A discloses a composite electrode material of MXene-coated porous silicon and its preparation method. In addition, other existing technologies also attach silicon nanoparticles to Ti3C2T. X MXene forms a porous, layered structure through cross-linking between its surface and interlayer layers. These existing technologies effectively utilize the high electrical conductivity of MXene, but they are all based on nano-silicon and generally suffer from the following drawbacks:

[0005] (1) Nano-silicon is expensive, has low tap density, low coulombic efficiency and complex preparation process, which makes it difficult to scale up and hinders its further commercialization. In particular, the low tap density of nano-silicon leads to a low volumetric capacity of the prepared electrodes.

[0006] (2) MXene is usually combined with nano-silicon particles in a coating manner, but this coating technology is not suitable for micron-scale silicon because MXene is a two-dimensional sheet structure. To coat micron-scale spheres, a large sheet size is required, as well as a certain degree of mechanical bending. However, the sheet structure of MXene is usually nanoscale, and it is difficult to achieve a large size. In other words, the existing method of combining MXene with silicon particles in a coating manner is only applicable to nano-scale silicon and is not applicable to micron-scale silicon particles.

[0007] (3) Due to the two-dimensional sheet structure of MXene, it cannot achieve complete protection of nano-silicon.

[0008] (4) When preparing traditional electrodes, grinding and coating methods are often used. However, the external force during the grinding process will destroy the original structure of the active material to a certain extent, resulting in most of the silicon material being exposed on the electrode surface. In addition, conductive additives usually agglomerate during the grinding process, making it difficult to disperse evenly. This leads to failure of electron transport or lithium ion diffusion, exacerbates electrode polarization, and significantly reduces electrode reversibility. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the present invention provides a method for preparing Si / MXene electrodes by bonding and encapsulating with solid adhesive, which utilizes the combination of MXene and micron-sized silicon particles to prepare high-performance silicon negative electrodes.

[0010] The technical solution adopted by this invention to solve its technical problem is: a method for preparing Si / MXene electrodes by bonding and coating with solid adhesive, comprising the following steps:

[0011] S1. Preparation of porous silica microspheres;

[0012] S2. Prepare MXene suspension;

[0013] S3. Porous silicon microspheres are added to a certain amount of MXene suspension, wherein the mass ratio between Si and MXene is 2 to 5:1. The mixture is stirred continuously in an ice bath for 20 to 30 hours. After vacuum filtration and drying, Si / MXene composite powder with MXene embedded in porous silicon microspheres is obtained.

[0014] S4. Cut copper foil, apply solid glue GS to the surface of copper foil, then spread a certain amount of Si / MXene composite powder on the area of ​​copper foil with the colloid layer, apply another layer of solid glue, and use a mold to press the coating to obtain the electrode sheet;

[0015] S5. Dry the electrode in a vacuum drying oven at 50-70℃ for 8-15 hours, and then heat it in an argon tube furnace at 420-480℃ for 1.5-3 hours to carbonize the colloidal layer, finally obtaining the Si / MXene@GS three-dimensional structure electrode.

[0016] Preferably, step S1 is performed as follows: 3-6g of aluminum-silicon alloy powder with a particle size of 6-10μm is added to 180-220ml of hydrochloric acid solution, wherein the concentration of hydrochloric acid solution is 1-2mol / L. The mixture is stirred at a constant speed at room temperature for 20-30 hours, then vacuum filtered and the product is washed with deionized water. The washing and filtration are repeated until the filtrate is neutral. The product is then placed in a vacuum constant temperature drying oven at 55-65℃ and dried for 10-15 hours to obtain porous silicon microspheres, which are reserved for later use.

[0017] Preferably, the specific operation of step S2 is as follows:

[0018] Add 0.8–1.2 g of titanium aluminum carbide MAX phase to a mixed solution containing 15–25 mL of hydrochloric acid (9–12 mol / L) and 1.7–2.4 g of LiF. Stir continuously in an oil bath at 38–45 °C for 30–40 hours. Then centrifuge the solution at 6000–10000 r / min. Repeat the washing and centrifugation of the precipitate until the supernatant is neutral and then collect the precipitate.

[0019] The precipitate was added to 15-25 ml of tetramethylammonium hydroxide solution and sonicated for 1.5-2.5 hours. Then it was centrifuged at 8000-12000 r / min for 8-15 minutes. The supernatant obtained was the MXene suspension.

[0020] Preferably, the mass ratio of Si to MXene in step S3 is 4:1.

[0021] Preferably, in step S4, every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region is 0.06–0.1 g.

[0022] Preferably, in step S5, the mass percentage of carbon after carbonization of the colloidal layer is 18-23% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0023] Preferably, the tetramethylammonium hydroxide solution is an aqueous solution with a mass concentration of 22-28%.

[0024] The positive effects of this invention:

[0025] 1. This invention uses micron-sized silicon and MXene to prepare a high-performance electrode composite material. MXene can not only effectively accelerate the electronic conduction of electrochemical active sites, but its two-dimensional structure and excellent mechanical properties also enable lithium ions to be embedded in the MXene interlayer without destroying the structure and occupy abundant electrochemical active sites, thus realizing the rapid insertion and extraction and transport of lithium ions. At the same time, compared with nanoscale silicon, micron-sized silicon has a lower price and higher tap density, which makes it more suitable for practical application.

[0026] 2. The volume effect of micron-sized silicon cannot be ignored. Therefore, this invention uses micron-sized aluminum-silicon alloy as raw material to prepare porous silicon, so as to alleviate the volume effect problem of silicon to a certain extent. Unlike the existing encapsulation structure, MXene is embedded in the channels of the porous micron-sized silicon spheres in this invention. This MXene embedded structure plays a role in supporting the channels of the porous micron-sized silicon, improving the structural strength of the composite material, increasing the pore density inside the material, and providing a large number of efficient and fast migration channels for lithium ions and electrons. This is something that the MXene encapsulation structure cannot achieve. In addition, the structural advantages of the porous silicon microspheres themselves also reserve sufficient buffer space for the volume expansion of silicon.

[0027] 3. In a simple MXene-embedded micron-sized porous silicon material structure, the silicon surface is still exposed to the electrolyte, making it difficult to maintain structural stability under long-term cycling. However, the solid adhesive carbonization layer on the periphery of this invention effectively isolates the silicon from the electrolyte, which is conducive to the formation of a stable solid electrolyte phase (SEI). This avoids the problem of excessive consumption of lithium ions and rapid battery capacity decay caused by repeated breakage and recombination of the SEI layer. Moreover, the carbon coating layer and the embedded MXene conductive network provide dual support for the structural strength of the electrode, enabling the three-dimensional electrode to have long-term effective conductivity and structural integrity.

[0028] 4. The Si / MXene@GS three-dimensional electrode of this invention eliminates the need for the addition of conductive agents and binders in the traditional silicon electrode preparation process, greatly simplifying the preparation process. Compared with the traditional grinding and coating method, it also avoids the risk of damage to the active material structure. At the same time, the solid organic adhesive coating method is more suitable for large-scale industrial production. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the fabrication of the Si / MXene@GS three-dimensional structure electrode described in this invention;

[0030] Figure 2a This is the SEM image of pSiMS described in Example 1;

[0031] Figure 2b It is the SEM image of MXene described in Example 1;

[0032] Figure 2c This is a SEM image of the Si / MXene composite material described in Example 1;

[0033] Figure 2d These are SEM images of Si / MXene@GS as described in Example 1;

[0034] Figure 3 These are the XRD patterns of MXene, Si / MXene, and Si / MXene@GS described in Example 1;

[0035] Figure 4 These are constant current charge-discharge cycle test diagrams for MXene, Si / MXene, and Si / MXene@GS as described in Example 1;

[0036] Figure 5 These are the rate performance test graphs of Si / MXene@GS at different current densities described in Example 1;

[0037] Figure 6 This is a comparison chart of the constant current charge-discharge cycle test of Si / MXene@GS described in Example 1 and the coated Si@MX described in Comparative Example 1. Detailed Implementation

[0038] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] Reference Figure 1 This invention provides a method for preparing Si / MXene electrodes by bonding and encapsulating with solid adhesive, comprising the following steps:

[0040] S1. Preparation of porous silicon microspheres: 3-6 g of aluminum-silicon alloy powder with a particle size of 6-10 μm was added to 180-220 ml of hydrochloric acid solution with a concentration of 1-2 mol / L. The mixture was stirred at a constant speed at room temperature for 20-30 hours. The mixture was then vacuum filtered and washed with deionized water. The washing and filtration were repeated until the filtrate was neutral. The product was then placed in a vacuum constant temperature drying oven at 65-65℃ and dried for 10-15 hours to obtain porous silicon microspheres (denoted as pSiMS), which were set aside for later use. The pore size of the porous silicon microspheres was about 200 nm, which was large enough to embed MXene nanosheets.

[0041] S2. Preparation of MXene suspension, the specific steps are as follows:

[0042] Add 0.8–1.2 g of titanium aluminum carbide MAX phase to a mixed solution containing 15–25 mL of hydrochloric acid (9–12 mol / L) and 1.7–2.4 g of LiF. Stir continuously in an oil bath at 38–45 °C for 30–40 hours. Then centrifuge the solution at 6000–10000 r / min. Repeat the washing and centrifugation of the precipitate until the supernatant is neutral and then collect the precipitate.

[0043] The precipitate was added to 15-25 ml of tetramethylammonium hydroxide solution (aqueous solution with a mass concentration of 22-28%) and sonicated for 1.5-2.5 hours. Then it was centrifuged at 8000-12000 r / min for 8-15 minutes. The supernatant obtained was the MXene suspension.

[0044] S3. Porous silicon microspheres are added to a certain amount of MXene suspension, wherein the mass ratio between Si and MXene is 2 to 5:1. The mixture is stirred continuously in an ice bath for 20 to 30 hours. After vacuum filtration and drying, Si / MXene composite powder with MXene embedded in porous silicon microspheres is obtained.

[0045] S4. Cut copper foil, apply solid adhesive GS to the surface of the copper foil, then spread a certain amount of Si / MXene composite powder evenly on the area of ​​the copper foil with the adhesive layer, apply another layer of solid adhesive, and use a mold to compact the coating to obtain the electrode sheet; wherein, every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region is 0.06–0.1 g.

[0046] S5. Dry the electrode in a vacuum drying oven at 50-70℃ for 8-15 hours, and then heat it in an argon tube furnace at 420-480℃ for 1.5-3 hours to carbonize the colloidal layer, finally obtaining the Si / MXene@GS three-dimensional structure electrode, wherein the mass ratio of carbon after colloidal layer carbonization is 18-23% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0047] This invention integrates MXene with micron-sized porous silicon via embedding, and uses a solid organic adhesive as both a binder before coating and a conductive agent after carbonization. This simple method produces a more stable and higher-performance Si / MX@GS three-dimensional electrode. Specifically, this invention innovatively uses a solid organic adhesive instead of a binder, directly coating it onto copper foil. Simultaneously, it achieves a coating effect on the Si / MXene composite material. After carbonization, the solid adhesive coating layer transforms into a conductive agent, similar to that in traditional electrodes, thus combining embedding and coating. This process not only avoids cumbersome electrode fabrication procedures but also adds carbon coating to the embedded MXene three-dimensional structure. Furthermore, the dual-functional solid adhesive carbon coating layer effectively supports the structural strength of the embedded Si / MXene composite material.

[0048] Example 1

[0049] Embodiment 1 of the present invention provides a method for preparing Si / MXene electrodes by bonding and encapsulating with solid adhesive, comprising the following steps:

[0050] S1. Preparation of porous silicon microspheres: 5g of aluminum-silicon alloy powder with a particle size of about 8μm was added to 200ml of 1.5mol / L hydrochloric acid solution and stirred at a constant speed for 24 hours at room temperature. Then, the product was vacuum filtered and washed with deionized water. The washing and filtration were repeated until the filtrate was neutral. The product was then placed in a vacuum constant temperature drying oven at 60℃ and dried for 12 hours to obtain porous silicon microspheres (denoted as pSiMS), which were reserved for later use.

[0051] S2. Preparation of MXene suspension, the specific steps are as follows:

[0052] 1g of titanium aluminum carbide MAX phase (Ti3C2Tx) was added to a mixed solution containing 20mL of 10mol / L hydrochloric acid and 2g of LiF. The solution was stirred continuously in an oil bath at 40℃ for 36 hours. The solution was then centrifuged at 6000-10000r / min. The precipitate was repeatedly washed and centrifuged until the supernatant was neutral before the precipitate was collected.

[0053] The precipitate was added to 20 ml of tetramethylammonium hydroxide solution (a 25% aqueous solution) and sonicated for 2 hours. Then it was centrifuged at 10000 r / min for 10 minutes. The supernatant obtained was the MXene suspension.

[0054] S3. Add 0.3g of porous silica microspheres to 30ml of MXene suspension, wherein the mass ratio of Si to MXene is 4:1. Stir continuously in an ice bath for 24 hours. After vacuum filtration and drying, obtain Si / MXene composite powder with MXene embedded in porous silica microspheres.

[0055] S4. Cut copper foil, apply GS (3M Scotch 6015 solid adhesive) to the surface of the copper foil, then spread a certain amount of Si / MXene composite powder evenly on the area of ​​the copper foil with the adhesive layer, apply another layer of solid adhesive, and use a mold to compact the coating to obtain the electrode sheet; wherein, every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region was 0.08 g;

[0056] S5. The electrode is dried in a vacuum drying oven at 60℃ for 12 hours, and then heated in an argon tube furnace at 450℃ for 2 hours to carbonize the colloidal layer, finally obtaining a Si / MXene@GS three-dimensional structure electrode; wherein the mass ratio of carbon after the colloidal layer carbonization is 20% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0057] Example 2

[0058] Embodiment 2 of the present invention provides a method for preparing Si / MXene electrodes by bonding and coating with solid adhesive, comprising the following steps:

[0059] S1. Preparation of porous silicon microspheres: 3g of aluminum-silicon alloy powder with a particle size of about 6μm was added to 220ml of 1mol / L hydrochloric acid solution and stirred at a constant speed for 30 hours at room temperature. Then, the product was vacuum filtered and washed with deionized water. The washing and filtration were repeated until the filtrate was neutral. The product was then placed in a vacuum constant temperature drying oven at 55℃ and dried for 10 hours to obtain porous silicon microspheres for later use.

[0060] S2. Preparation of MXene suspension, the specific steps are as follows:

[0061] 0.8 g of titanium aluminum carbide MAX phase (Ti2CTx) was added to a mixed solution containing 15 mL of hydrochloric acid (9 mol / L) and 1.8 g of LiF. The solution was stirred continuously in an oil bath at 45 °C for 30 hours. The solution was then centrifuged at 6000 r / min. The precipitate was repeatedly washed and centrifuged until the supernatant was neutral before the precipitate was collected.

[0062] The precipitate was added to 25 ml of tetramethylammonium hydroxide solution (a 23% aqueous solution) and sonicated for 2.5 hours. Then it was centrifuged at 8000 r / min for 15 minutes. The supernatant obtained was the MXene suspension.

[0063] S3. Porous silicon microspheres were added to a certain amount of MXene suspension, wherein the mass ratio between Si and MXene was 2:1. The mixture was stirred continuously in an ice bath for 30 hours. After vacuum filtration and drying, Si / MXene composite powder with MXene embedded in porous silicon microspheres was obtained.

[0064] S4. Cut copper foil, apply solid adhesive GS to the surface of the copper foil, then spread a certain amount of Si / MXene composite powder evenly on the area of ​​the copper foil with the adhesive layer, apply another layer of solid adhesive, and use a mold to compact the coating to obtain the electrode sheet; wherein, every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region is 0.06 g;

[0065] S5. The electrode is dried in a vacuum drying oven at 70℃ for 15 hours, and then heated in an argon tube furnace at 420℃ for 3 hours to carbonize the colloidal layer, finally obtaining a Si / MXene@GS three-dimensional structure electrode; wherein the mass ratio of carbon after the colloidal layer carbonization is 18% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0066] Example 3

[0067] Embodiment 3 of the present invention provides a method for preparing Si / MXene electrodes by bonding and coating with solid adhesive, comprising the following steps:

[0068] S1. Preparation of porous silicon microspheres: 6g of aluminum-silicon alloy powder with a particle size of about 10μm was added to 180ml of 2mol / L hydrochloric acid solution and stirred at a constant speed for 20 hours at room temperature. Then, the product was vacuum filtered and washed with deionized water. The washing and filtration were repeated until the filtrate was neutral. The product was then placed in a vacuum constant temperature drying oven at 65℃ and dried for 15 hours to obtain porous silicon microspheres for later use.

[0069] S2. Preparation of MXene suspension, the specific steps are as follows:

[0070] 1.2 g of titanium aluminum carbide MAX phase (Ti3C2Tx) was added to a mixed solution containing 25 mL of hydrochloric acid (12 mol / L) and 2.4 g of LiF. The solution was stirred continuously in an oil bath at 38 °C for 40 hours. The solution was then centrifuged at 10000 r / min. The precipitate was repeatedly washed and centrifuged until the supernatant was neutral before the precipitate was collected.

[0071] The precipitate was added to a 1,6-tetramethylammonium hydroxide solution (a 28% aqueous solution) and sonicated for 1.6 hours. Then it was centrifuged at 8000 r / min for 8 minutes. The resulting supernatant was the MXene suspension.

[0072] S3. Porous silicon microspheres were added to a certain amount of MXene suspension, wherein the mass ratio between Si and MXene was 5:1. The mixture was stirred continuously in an ice bath for 20 hours. After vacuum filtration and drying, Si / MXene composite powder with MXene embedded in porous silicon microspheres was obtained.

[0073] S4. Cut copper foil, apply solid adhesive GS to the surface of the copper foil, then spread a certain amount of Si / MXene composite powder evenly on the area of ​​the copper foil with the adhesive layer, apply another layer of solid adhesive, and use a mold to compact the coating to obtain the electrode sheet; wherein, every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region is 0.1 g;

[0074] S5. The electrode is dried in a vacuum drying oven at 50℃ for 8.5 hours, and then heated in an argon tube furnace at 480℃ for 1.5 hours to carbonize the colloidal layer, finally obtaining a Si / MXene@GS three-dimensional structure electrode; wherein the mass ratio of carbon after the colloidal layer carbonization is 23% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0075] Example 4

[0076] Example 4 of this invention provides a method for preparing a Si / MXene electrode by bonding and encapsulating it with a solid adhesive, comprising the following steps:

[0077] S1. Preparation of porous silicon microspheres: 3.5g of aluminum-silicon alloy powder with a particle size of 8.5μm was added to 195ml of 1.2mol / L hydrochloric acid solution and stirred at a constant speed for 23 hours at room temperature. Then, the product was vacuum filtered and washed with deionized water. The washing and filtration were repeated until the filtrate was neutral. The product was then placed in a vacuum constant temperature drying oven at 58℃ and dried for 11 hours to obtain porous silicon microspheres for later use.

[0078] S2. Preparation of MXene suspension, the specific steps are as follows:

[0079] 1.1 g of titanium aluminum carbide MAX phase (Ti3C2Tx) was added to a mixed solution containing 22 mL of hydrochloric acid (10 mol / L) and 1.9 g of LiF. The solution was stirred continuously in an oil bath at 42 °C for 36 hours. The solution was then centrifuged at 7500 r / min. The precipitate was repeatedly washed and centrifuged until the supernatant was neutral before the precipitate was collected.

[0080] The precipitate was added to 19 ml of tetramethylammonium hydroxide solution (a 24% aqueous solution) and sonicated for 1.9 hours. Then it was centrifuged at 9000 r / min for 12 minutes. The resulting supernatant was the MXene suspension.

[0081] S3. Porous silicon microspheres were added to a certain amount of MXene suspension, wherein the mass ratio of Si to MXene was 3:1. The mixture was stirred continuously in an ice bath for 25 hours. After vacuum filtration and drying, Si / MXene composite powder with MXene embedded in porous silicon microspheres was obtained.

[0082] S4. Cut copper foil, apply solid adhesive GS to the surface of the copper foil, then spread a certain amount of Si / MXene composite powder evenly on the area of ​​the copper foil with the adhesive layer, apply another layer of solid adhesive, and use a mold to compact the coating to obtain the electrode sheet; where every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region is 0.07 g;

[0083] S5. The electrode is dried in a vacuum drying oven at 55℃ for 11 hours, and then heated in an argon tube furnace at 460℃ for 2.5 hours to carbonize the colloidal layer, finally obtaining a Si / MXene@GS three-dimensional structure electrode; wherein the mass ratio of carbon after the colloidal layer carbonization is 19% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0084] Example 5

[0085] Embodiment 5 of the present invention provides a method for preparing a Si / MXene electrode by bonding and coating with a solid adhesive, comprising the following steps:

[0086] S1. Preparation of porous silicon microspheres: 5.2g of aluminum-silicon alloy powder with a particle size of about 8μm was added to 210ml of 1.8mol / L hydrochloric acid solution and stirred at a constant speed for 26 hours at room temperature. Then, the product was vacuum filtered and washed with deionized water. The product was then placed in a vacuum constant temperature drying oven at 62℃ and dried for 14 hours to obtain porous silicon microspheres for later use.

[0087] S2. Preparation of MXene suspension, the specific steps are as follows:

[0088] 0.95 g of titanium aluminum carbide MAX phase (Ti3C2Tx) was added to a mixed solution containing 23 mL of hydrochloric acid (11 mol / L) and 2.2 g of LiF. The solution was stirred continuously in an oil bath at 42 °C for 37 hours. The solution was then centrifuged at 9000 r / min. The precipitate was repeatedly washed and centrifuged until the supernatant was neutral before the precipitate was collected.

[0089] The precipitate was added to 24 ml of tetramethylammonium hydroxide solution (a 26% aqueous solution) and sonicated for 2.5 hours. Then it was centrifuged at 11,000 r / min for 13 minutes. The supernatant obtained was the MXene suspension.

[0090] S3. Porous silicon microspheres were added to a certain amount of MXene suspension, wherein the mass ratio between Si and MXene was 3.5:1. The mixture was stirred continuously in an ice bath for 25 hours. After vacuum filtration and drying, Si / MXene composite powder with MXene embedded in porous silicon microspheres was obtained.

[0091] S4. Cut copper foil, apply solid adhesive GS to the surface of the copper foil, then spread a certain amount of Si / MXene composite powder evenly on the area of ​​the copper foil with the adhesive layer, apply another layer of solid adhesive, and use a mold to compact the coating to obtain the electrode sheet; where every 100cm 2 The amount of Si / MXene composite powder applied to the colloidal layer region was 0.09 g;

[0092] S5. The electrode is dried in a vacuum drying oven at 65℃ for 12 hours, and then heated in an argon tube furnace at 440℃ for 2 hours to carbonize the colloidal layer, finally obtaining a Si / MXene@GS three-dimensional structure electrode; wherein the mass ratio of carbon after the colloidal layer carbonization is 21.5% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

[0093] Comparative Example 1

[0094] The coated Si@MX composite electrode was prepared using a hydrothermal method based on existing technology. The specific preparation steps are as follows:

[0095] First, take 0.5g of aluminum-silicon alloy powder with a particle size of about 8μm and 20ml of 1M acetic acid and add it to 80ml of deionized water. Place the mixture in a 50℃ water bath and stir for 3 hours. This is recorded as solution A. After solution A cools to room temperature, use a pipette to add 3mL of 115mg / ml MXene suspension (the suspension described in Example 1) to it. Stir at room temperature for 30 minutes. This is recorded as solution B. Then pour solution B into the inner liner of a 200ml hydrothermal reactor and seal it. Next, place the hydrothermal reactor in a forced-air drying oven at a temperature of 180℃ and keep it at that temperature for 6 hours. After the hydrothermal reactor has completely cooled, the hydrothermal solution C is freeze-dried under vacuum for 36 hours to obtain the hydrothermal product. The hydrothermal product is then washed with 1M hydrochloric acid and 5% hydrofluoric acid, vacuum filtered, and washed with deionized water and anhydrous ethanol until the filtrate is neutral. The product is then placed in a vacuum constant temperature drying oven at 60°C and dried for 12 hours to obtain a composite material electrode of MXene-coated porous micron-sized silicon, denoted as Si@MX.

[0096] like Figure 2a As shown in Figure d, the MXene-embedded composite material Si / MXene prepared by this invention has densely distributed MXene throughout the pores of porous silicon. This not only enhances the electrical conductivity of the material and provides more diffusion channels for Li+, but also provides good structural strength support for the expansion and contraction of silicon. Simultaneously, after coating with a solid adhesive carbonization layer, it protects the silicon exposed on the pore walls, facilitating the formation of a complete and stable SEI film.

[0097] like Figure 3As shown, the elemental composition of MXene, Si / MXene, and Si / MXene@GS materials was determined, and the appearance of characteristic peaks corresponding to each element confirmed the integrity of their structure.

[0098] MXene, Si / MXene, and Si / MXene@GS were used as electrodes to assemble lithium-ion half-cells for electrochemical testing (electrolytes were 1M LiPF6, EC:DEC:EMC = 1:1:1 vol% and 5% FEC). The electrolytes were measured at 0.1 A g. -1 After activation, at a current density of 1 A g -1 Under the condition of 300 cycles, such as Figure 4 As shown, the reversible specific capacity of the Si / MX@GS electrode is 970.1 mAh g. -1 The capacity retention rate after 50 cycles was 75.2%, with an average decay of only 0.09% per cycle, demonstrating excellent electrochemical performance; the reversible specific capacity of the Si / MXene electrode was 805.4 mAh g. -1 The corresponding decay rate after 50 cycles was 69.0%, while the micron-sized porous silicon pSiMS electrode only lasted for about 120 cycles at this current density.

[0099] like Figure 5 As shown, in 2Ag -1 At high current density, the average specific capacity of Si / MX@GS is 769.9 mAh g. -1 When the current density recovers to 1Ag -1 At that time, its reversible specific capacity also recovered to 1097.3 mAh g immediately. -1 It demonstrates good rate capability and reversibility.

[0100] like Figure 6 As shown, the comparative example shows a coated Si@MX composite electrode, which operates at a current density of 1 Ag. -1 Under these conditions, the reversible specific capacity after 300 cycles is 465.4 mAh g. -1 Its performance is far inferior to the embedded Si / MX@GS three-dimensional structure electrode described in this invention.

[0101] The above description is only a preferred embodiment of the present invention. It should be understood that the above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, etc. made within the idea and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing Si / MXene electrode by solid adhesive bonding coating, characterized in that, Comprising the following steps: S1. Preparing porous silicon microspheres, specifically: adding 3-6 g of aluminum-silicon alloy powder with a particle size of 6-10 μm to 180-220 ml of a hydrochloric acid solution, stirring at room temperature for 20-30 hours, then vacuum filtering and washing the product with deionized water, repeating the washing and filtering until the filtrate is neutral, and then drying the product in a vacuum constant temperature drying oven at 55-65°C for 10-15 hours to obtain porous silicon micrometer balls, which are ready for use; S2. Preparing a MXene suspension; S3. Adding porous silicon microspheres to a certain amount of MXene suspension, with a mass ratio of Si to MXene of 2-5:1, continuously stirring in an ice bath for 20-30 hours, vacuum filtering and drying to obtain Si / MXene composite material powder with MXene embedded in the porous silicon microspheres; S4. Cutting a copper foil, applying a solid glue GS to the surface of the copper foil, then spreading a certain amount of Si / MXene composite material powder on the area of the copper foil where the glue layer is applied, applying another layer of solid glue, and using a mold to compact the coating to obtain an electrode sheet; S5. Drying the electrode sheet in a vacuum drying oven at 50-70°C for 8-15 hours, then carbonizing the glue layer in an argon tube furnace at 420-480°C for 1.5-3 hours, and finally obtaining a Si / MXene@GS three-dimensional structure electrode.

2. The method for preparing Si / MXene electrode by solid adhesive bonding coating according to claim 1, characterized in that, The specific operation of step S2 is: Add 0.8-1.2 g of titanium aluminum carbide MAX phase to a mixed solution containing 15-25 mL of hydrochloric acid and 1.7-2.4 g of LiF, continuously stirring in an oil bath at 38-45°C for 30-40 hours, then centrifuging the solution at a speed of 6000-10000 r / min, and repeating the washing and centrifuging of the precipitate until the supernatant is neutral, then taking the precipitate; Add the obtained precipitate to 15-25 ml of tetramethylammonium hydroxide solution and ultrasonic for 1.5-2.5 hours, then centrifuge at a speed of 8000-12000 r / min for 8-15 minutes, and the obtained centrifugal supernatant is the MXene suspension.

3. The method for preparing Si / MXene electrode by solid adhesive bonding coating according to claim 1, characterized in that: The mass ratio of Si to MXene in step S3 is 4:

1.

4. The method for preparing Si / MXene electrode by solid adhesive bonding coating according to claim 1, characterized in that: The amount of the Si / MXene composite powder applied in step S4 is 0.06-0.1 g per 100 cm2. 2 The amount of the Si / MXene composite powder applied in step S4 is 0.06-0.1 g per 100 cm2.

5. The method for preparing Si / MXene electrode by solid adhesive bonding coating according to claim 1, characterized in that: After carbonization of the glue layer in step S5, the mass fraction of carbon is 18-23% of the total mass of the obtained Si / MXene@GS three-dimensional structure electrode.

6. The method of claim 2, wherein the method is characterized by: The tetramethylammonium hydroxide solution is an aqueous solution with a mass concentration of 22-28%.

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