Composite material and preparation method therefor, negative electrode current collector, metal battery, and electrical apparatus

Abstract

The present application relates to the technical field of secondary batteries, and specifically relates to a composite material and a preparation method therefor, a negative electrode current collector, a metal battery, and an electrical apparatus. The composite material provided in the present application comprises: a MXene material, the MXene material comprising surface functional groups; silver nanoparticles, the silver nanoparticles being grown in situ on the surface of a sheet layer of the MXene material; and modified bacterial cellulose, the modified bacterial cellulose comprising bacterial cellulose and oxygen-containing functional groups modified on the surface of the bacterial cellulose. The modified bacterial cellulose is loaded on the surface of the MXene material, the manner of loading of the modified bacterial cellulose at least comprising: intermolecular interaction between the oxygen-containing functional groups of the modified bacterial cellulose and the surface functional groups of the MXene material. The composite material provided in the present application has excellent lithiophilic performance, and can delay the formation of lithium dendrites, thereby helping to improve the electrochemical performance of a metal battery.

Description

Composite materials and their preparation methods, negative electrode current collectors, metal batteries, and electrical devices. Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to composite materials and their preparation methods, negative electrode current collectors, metal batteries, and electrical devices. Background Technology

[0002] With the development of electronic devices, electric vehicles, and portable power devices, the demand for battery energy density is increasing. Lithium metal batteries, due to their ultra-high theoretical specific capacity (3860 mAh g⁻¹), are particularly valuable. -1 Low density (0.53g cm⁻¹) -3 Lithium metal anodes, with their extremely low electrochemical potential (-3.04V vs. standard hydrogen electrode), are considered to be highly promising secondary batteries.

[0003] Currently, the negative electrode widely used in lithium metal batteries is lithium metal sheet. During battery cycling, lithium deposits on the copper surface and forms lithium dendrites. The dendrites grow continuously and pierce the separator, causing battery short circuits, low coulombic efficiency, short cycle life, and even safety issues. Summary of the Invention

[0004] Based on this, this application provides a composite material and its preparation method, a negative electrode current collector, a metal battery, and an electrical device. When used as a negative electrode current collector, the composite material provided in this application exhibits excellent lithium affinity, which can delay the formation of lithium dendrites, thereby helping to improve the electrochemical performance of lithium metal batteries.

[0005] A first aspect of this application provides a composite material, comprising:

[0006] MXene material, wherein the MXene material includes surface functional groups;

[0007] Silver nanoparticles, which are grown in situ on the surface of the MXene material sheets;

[0008] Modified bacterial cellulose, comprising bacterial cellulose and oxygen-containing functional groups modified on the surface of the bacterial cellulose; the modified bacterial cellulose is loaded on the surface of the MXene material;

[0009] The loading mode of the modified bacterial cellulose includes at least the intermolecular interaction between the oxygen-containing functional groups of the modified bacterial cellulose and the surface functional groups of the MXene material.

[0010] In one embodiment, the composite material has one or more of the following characteristics:

[0011] (1) The chemical formula of the MXene material is M n+1 X n T x Where M is a transition metal element, X is carbon or nitrogen element, and T is a transition metal element. x The surface functional group is a surface functional group, where n is 1, 2, or 3, and the surface functional group includes at least one of -OH, -F, and =O;

[0012] (2) In the composite material, the mass ratio of the MXene material to the modified bacterial cellulose is 10:(0.1~10);

[0013] (3) In the modified bacterial cellulose, the oxygen-containing functional group includes at least one of -OH and =O.

[0014] A second aspect of this application provides a method for preparing a composite material, comprising the following steps:

[0015] MXene solution was prepared by etching MAX material with an etchant under stirring conditions.

[0016] The MXene solution is mixed with silver nitrate, and silver ions undergo a reduction reaction on the surface of the MXene material sheets, so that silver nanoparticles grow in situ on the surface of the MXene material sheets, thus preparing a silver-loaded MXene solution.

[0017] A modified bacterial cellulose solution was prepared by modifying bacterial cellulose with an alkaline solution; wherein the surface of the modified bacterial cellulose includes oxygen-containing functional groups.

[0018] The silver-loaded MXene solution and the modified bacterial cellulose solution are mixed to load the modified bacterial cellulose onto the surface of the MXene material, thereby preparing the composite material.

[0019] In one embodiment, the step of preparing the MXene solution further includes:

[0020] The etching agent is prepared by mixing a fluoride salt and hydrochloric acid;

[0021] The mass-to-volume ratio of the fluoride salt and the hydrochloric acid is 1 g: (10-20) mL.

[0022] In one embodiment, the step of preparing the MXene solution has one or more of the following features:

[0023] (1) The fluoride salt includes one or more of lithium fluoride, sodium fluoride and potassium fluoride;

[0024] (2) The molar concentration of the hydrochloric acid is 6 mol / L to 12 mol / L;

[0025] (3) The chemical formula of the MAX material is M m+1 AX m In this context, M is a transition metal element, A is a main group element of group IIIA or IVA, X is carbon or nitrogen, and m is 1, 2, or 3.

[0026] (4) The mass ratio of the fluoride salt included in the etching agent to the mass of the MAX material is 1:(0.8~1.5);

[0027] (5) After the etching process, the method further includes: centrifuging and washing the etched mixture, collecting the solid phase, dispersing the solid phase in a dispersant, collecting the supernatant, and preparing the MXene solution.

[0028] In one embodiment, the step of preparing the silver-loaded MXene solution has one or more of the following features:

[0029] (1) In the solution formed by mixing the MXene solution and silver nitrate, the mass concentration of silver nitrate is 0.3 mg / mL to 1 mg / mL;

[0030] (2) The process parameters of the reduction reaction include: stirring speed of 50 r / min to 300 r / min.

[0031] In one embodiment, the step of preparing the modified bacterial cellulose solution has one or more of the following features:

[0032] (1) The alkaline solution includes one or more of KOH and NaOH;

[0033] (2) The molar concentration of the alkaline solution is 0.8 mol / L to 1.5 mol / L;

[0034] (3) The process parameters of the modification treatment include: the modification temperature is 40℃~90℃.

[0035] A third aspect of this application provides a negative electrode current collector comprising the composite material described in any one of the first aspects of this application, or the composite material prepared by any one of the preparation methods described in any one of the second aspects of this application.

[0036] A fourth aspect of this application provides a metal battery including the negative electrode current collector described in any of the third aspects of this application.

[0037] In one embodiment, the metal battery has one or more of the following features:

[0038] (1) The thickness of the negative electrode current collector is 0.5 μm to 20 μm;

[0039] (2) The metal battery includes one or more of lithium metal batteries, sodium metal batteries and potassium metal batteries.

[0040] A fifth aspect of this application provides an electrical device including the metal battery described in the third aspect of this application.

[0041] The composite material provided in this application has at least the following beneficial effects:

[0042] The composite material provided in this application exhibits excellent electrochemical performance when used as a negative electrode current collector. Specifically, the composite material includes MXene material, which possesses excellent metallic conductivity, providing an effective electron transport channel. Simultaneously, the MXene sheet carrying silver nanoparticles can further modulate the local electric field and chemical environment around the MXene material, making the deposition or extraction of negative electrode active materials such as lithium more uniform, thus promoting the formation of uniform nucleation and helping to reduce battery performance degradation caused by intense local reactions such as the formation of lithium dendrites.

[0043] Furthermore, the intermolecular interactions between the oxygen-containing functional groups on the surface of modified bacterial cellulose and the surface functional groups of MXene material enable the composite of modified bacterial cellulose and MXene material. This further enhances the mechanical properties of the negative electrode current collector and prevents the MXene material from undergoing layer stacking or structural collapse during battery cycling. Moreover, the composite of modified bacterial cellulose and MXene material optimizes the interface between the negative electrode current collector and the negative electrode active material. This favorable interfacial interaction improves the adhesion of the negative electrode active material to the current collector, making it less prone to detachment during charge and discharge, thus ensuring consistently good electrical contact between the negative electrode active material and the negative electrode current collector, thereby improving the battery's cycle performance.

[0044] In addition, the composite material provided in this application has a flexible structure, which can meet the requirements of heterogeneous batteries. Attached Figure Description

[0045] Figure 1 shows the XRD patterns of MXene prepared in step (3) of Example 1 of this application, bacterial cellulose prepared in step (5), and flexible current collector prepared in step (8).

[0046] Figure 2 shows a digital image of the flexible current collector prepared in Example 1, and a thickness measurement image;

[0047] Figure 3 is a scanning electron microscope image of the flexible current collector prepared in Example 1 of this application;

[0048] Figure 4 is a nucleation overpotential test curve of the flexible current collector prepared in Example 1 of this application assembled into an asymmetric battery;

[0049] Figure 5 is a nucleation overpotential test curve of the flexible current collector prepared in Comparative Example 2 of this application assembled into an asymmetric battery;

[0050] Figure 6 is a coulombic efficiency test curve of the flexible current collector prepared in Example 1 of this application assembled into an asymmetric battery;

[0051] Figure 7 is a cycle performance curve of a lithium symmetric battery assembled with a flexible current collector prepared in Example 1 of this application. Detailed Implementation

[0052] The following detailed description, in conjunction with specific embodiments, provides a more complete and clear account of the composite material, its preparation method, the negative electrode current collector, the metal battery, and the electrical device of this application. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0053] In some specialized electronic products or devices, irregularly shaped batteries may be required to meet space and shape constraints. For example, wearable devices such as smartwatches and fitness trackers have limited internal space and irregular shapes. Flexible negative electrode current collectors can easily adapt to these special shapes, allowing the battery to be better embedded inside the device and improving space utilization.

[0054] The main problems in the development of lithium metal anodes are: First, lithium metal anodes themselves have poor electrochemical performance and are prone to dendrite formation during charging and discharging, which can cause problems such as battery short circuits, low coulombic efficiency, and short cycle life. Second, in the electrode preparation process, there are limited ways to combine lithium metal with current collectors, and the flexible function is difficult to achieve due to the limitations of the metal material of traditional current collectors.

[0055] Based on this, a first aspect of this application provides a composite material, comprising:

[0056] MXene material, wherein the MXene material includes surface functional groups;

[0057] Silver nanoparticles, which are grown in situ on the surface of the MXene material sheets;

[0058] Modified bacterial cellulose, comprising bacterial cellulose and oxygen-containing functional groups modified on the surface of the bacterial cellulose; the modified bacterial cellulose is loaded on the surface of the MXene material;

[0059] The loading mode of the modified bacterial cellulose includes at least the intermolecular interaction between the oxygen-containing functional groups of the modified bacterial cellulose and the surface functional groups of the MXene material.

[0060] The composite material provided in this application exhibits excellent electrochemical performance when used as a negative electrode current collector. Specifically, the composite material includes MXene material, which possesses excellent metallic conductivity, providing an effective electron transport channel. Simultaneously, the MXene nanosheets carrying silver nanoparticles can further modulate the local electric field and chemical environment around the MXene material, making the deposition or extraction of negative electrode active materials such as lithium more uniform, thus promoting the formation of uniform nucleation and helping to reduce battery performance degradation caused by intense local reactions such as the formation of lithium dendrites.

[0061] Furthermore, the intermolecular interactions between the oxygen-containing functional groups on the surface of modified bacterial cellulose and the surface functional groups of MXene material enable the composite of modified bacterial cellulose and MXene material. This further enhances the mechanical properties of the negative electrode current collector and prevents the MXene material from undergoing layer stacking or structural collapse during battery cycling. Moreover, the composite of modified bacterial cellulose and MXene material optimizes the interface between the negative electrode current collector and the negative electrode active material. This favorable interfacial interaction improves the adhesion of the negative electrode active material to the current collector, making it less prone to detachment during charge and discharge, thus ensuring consistently good electrical contact between the negative electrode active material and the negative electrode current collector, thereby improving the battery's cycle performance.

[0062] In addition, the composite material provided in this application has a flexible structure, which can meet the requirements of heterogeneous batteries.

[0063] In one example, the general chemical formula of the MXene material is M. n+1 X n T x Where M is a transition metal element, X is carbon or nitrogen element, and T is a transition metal element. x The surface functional group is n, which is 1, 2 or 3, and the surface functional group includes at least one of -OH, -F and =O.

[0064] MXene materials possess a two-dimensional layered structure, and the chemical bond between M and X atoms exhibits metallic properties, enabling rapid electron transport. Furthermore, MXene materials are obtained by etching MAX materials. Since A atoms are removed from MAX materials, the surface of the M atoms bonded to A atoms contains numerous dangling bonds and defects. These dangling bonds and defects are Ag loadings or Ag... + The reduction process provides active sites. Furthermore, the etched MXene material possesses a large number of surface functional groups, which allows it to better combine with modified bacterial cellulose.

[0065] Furthermore, in the MXene material, M includes, but is not limited to, Ti. For example, the MXene material includes Ti2CT. xTi3C2T x Ti3N4T x and Ti3CNT x One or more of them.

[0066] In one example, the mass ratio of the MXene material to the modified bacterial cellulose in the composite material is 10:(0.1 to 10). It is understood that the mass ratio of the MXene material to the modified bacterial cellulose can be selected from any value between 10:(0.1 to 10). For example, the mass ratio of the MXene material to the modified bacterial cellulose includes, but is not limited to, 10:0.1, 10:0.5, 10:1, 10:1.5, 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, or 10:10.

[0067] In one example, the modified bacterial cellulose contains oxygen-containing functional groups including at least one of -OH and =O.

[0068] In this application, oxygen-containing functional groups such as -OH and =O are used to modify bacterial cellulose, enabling intermolecular interactions such as hydrogen bonds between the oxygen-containing functional groups in the modified bacterial cellulose and the surface functional groups of MXene materials, thereby achieving the composite of modified cellulose and MXene materials.

[0069] A second aspect of this application provides a method for preparing a composite material, comprising the following steps:

[0070] S10. Under stirring conditions, MAX material is etched with an etchant to prepare MXene solution.

[0071] S20. Mix the MXene solution with silver nitrate. Silver ions undergo a reduction reaction on the surface of the MXene material sheets, allowing silver nanoparticles to grow in situ on the surface of the MXene material sheets, thus preparing a silver-loaded MXene solution.

[0072] S30. Modified bacterial cellulose is prepared by treating bacterial cellulose with an alkaline solution; wherein the surface of the modified bacterial cellulose includes oxygen-containing functional groups.

[0073] S40. The silver-loaded MXene solution and the modified bacterial cellulose solution are mixed to load the modified bacterial cellulose onto the surface of the MXene material, thereby preparing a composite material.

[0074] In one example, step S10, the step of preparing the MXene solution further includes:

[0075] S100. The etchant is prepared by mixing fluoride salt and hydrochloric acid.

[0076] In one example, in step S100, the mass-to-volume ratio of the fluoride salt and the hydrochloric acid mixture is 1 g:(10-20) mL. It is understood that the mass-to-volume ratio of the fluoride salt and the hydrochloric acid mixture can be selected from any value between 1 g:(10-20) mL. For example, the mass-to-volume ratio of the fluoride salt and the hydrochloric acid mixture includes, but is not limited to, 1 g:10 mL, 2 g:10 mL, 5 g:10 mL, 7 g:10 mL, 9 g:10 mL, or 10 g:10 mL.

[0077] In one example, in step S100, the molar concentration of the hydrochloric acid is 6 mol / L to 12 mol / L. For example, the molar concentration of the hydrochloric acid includes, but is not limited to, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, or 12 mol / L.

[0078] In one example, in step S100, the fluoride salt includes one or more of lithium fluoride, sodium fluoride, and potassium fluoride.

[0079] This application reveals that etchants prepared from fluoride salts and hydrochloric acid exhibit a gentler etching effect on MAX materials compared to etchants based on hydrofluoric acid. Furthermore, the metal ions in the fluoride salts can penetrate into the interlayer space during etching, widening the interlayer gap and facilitating nanosheet separation during the exfoliation process. Therefore, etchants that form hydrofluoric acid in situ not only increase the MXene nanosheet content in the solution but also yield high-quality nanosheets while ensuring the exposure of dangling bonds and defects on the M atoms' surfaces, thus facilitating Ag loading or Ag... + The reduction provides active sites.

[0080] In one example, in step S10, the general chemical formula of the MAX material is M. m+1 AX m In this context, M is a transition metal element, A is a main group element of group IIIA or IVA, X is carbon or nitrogen, and m is 1, 2, or 3.

[0081] For example, the MAX material is one or more of Ti2AlC, Ti3AlC2, Ti3AlN4, and Ti3AlCN.

[0082] To ensure the etching rate and the formation of dangling bonds and defects on the M-atom surface, in one example, in step S10, the mass ratio of the fluoride salt included in the etchant to the mass ratio of the MAX material is 1:(0.8 to 1.5). For example, the mass ratio of the fluoride salt included in the etchant to the mass ratio of the MAX material includes, but is not limited to, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5.

[0083] In one example, after the etching process in step S10, the process further includes: centrifuging and washing the etched mixture, collecting the solid phase, dispersing the solid phase in a dispersant, collecting the supernatant, and preparing the MXene solution.

[0084] In one example, the conditions for centrifugal washing include washing the mixture to a pH of 5–7.

[0085] In one example, the process parameters for dispersing the solid in the dispersant include: ultrasonication for 1 to 3 hours and a temperature of 5°C to 20°C.

[0086] The etched mixture is further centrifuged and washed, and the solid phase is collected. The solid phase is then dispersed in a dispersant to remove metal ions from the fluoride salt and purify the MXene material.

[0087] To ensure sufficient precipitation of impurities and maintain the separation efficiency of the Mxene material, the process parameters for collecting the supernatant in one example include: a centrifugation speed of 3000 r / min to 6000 r / min and a centrifugation time of 20 min to 40 min. For example, centrifugation speeds include, but are not limited to, 3000 r / min, 3500 r / min, 4000 r / min, 4500 r / min, 5000 r / min, 5500 r / min, or 6000 r / min. Centrifugation times include, but are not limited to, 20 min, 25 min, 30 min, 35 min, or 40 min.

[0088] To ensure Ag + Interactions with dangling bonds and defects of the M atom, and promote Ag +Reduction on the surface of MXene material. In one example, in step S20, the mass concentration of silver nitrate in the solution formed by mixing the MXene solution and silver nitrate is 0.3 mg / mL to 1 mg / mL. For example, in step S20, the mass concentration of silver nitrate in the solution formed by mixing the MXene solution and silver nitrate includes, but is not limited to, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, or 1 mg / mL.

[0089] In one example, in step S20, the process parameters of the reduction reaction include a stirring speed of 50 r / min to 300 r / min. For example, the stirring speed in the reduction reaction includes, but is not limited to, 50 r / min, 80 r / min, 100 r / min, 120 r / min, 140 r / min, 180 r / min, 200 r / min, 220 r / min, 250 r / min, 280 r / min, or 300 r / min.

[0090] In one example, in step S30, the alkaline solution includes one or more of KOH and NaOH.

[0091] In one example, in step S30, the molar concentration of the alkali solution is 0.8 mol / L to 1.5 mol / L. For example, the molar concentration of the alkali solution includes, but is not limited to, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or 1.5 mol / L.

[0092] In one example, in step S30, the process parameters for the modification treatment include: a modification temperature of 40℃ to 90℃. For example, the modification temperature includes, but is not limited to, 40℃, 50℃, 60℃, 70℃, 80℃, 85℃, or 90℃. Further, the modification time includes, but is not limited to, 20 min to 40 min.

[0093] By limiting the temperature and time of the modification treatment, as well as the molar concentration of the alkali solution, the surface of the bacterial cellulose after alkali treatment is loaded with abundant oxygen-containing functional groups. This ensures that it forms hydrogen bonds and other intermolecular interactions with the surface functional groups of the MXene material, so that the MXene material and the modified cellulose attract each other and form a stable connection at the interface of the two materials.

[0094] In one example, in step S40, the ratio of the mass of solids in the silver-loaded MXene solution to the mass of solids in the modified bacterial cellulose solution is 10:(0.1 to 10). For example, the ratio of the mass of solids in the silver-loaded MXene solution to the mass of solids in the modified bacterial cellulose solution includes, but is not limited to, 10:0.1, 10:0.2, 10:0.5, 10:1, 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, or 10:10.

[0095] In the preparation method provided in this application, under the synergy of the aforementioned steps and by limiting the process parameters of step S40, intermolecular interactions occur between the oxygen-containing functional groups of the modified bacterial cellulose and the surface functional groups of the MXene material. For example, hydrogen bonds can be formed between the surface functional groups of MXene and the functional groups on bacterial cellulose. At this point, the MXene nanosheets and bacterial cellulose fibers aggregate to form black gel clusters, which then settle. After standing for a period of time, it is obvious that the solution is divided into two parts: a clear solution at the top and gel clusters at the bottom. The formation of these gel clusters not only promotes the separation of water and precipitate, accelerating dehydration during the filtration process, but also avoids the layer stacking of the MXene nanosheets themselves, resulting in a large number of gaps in the first-formed film on the filter membrane surface to ensure smooth subsequent dehydration.

[0096] Furthermore, during the filtration of the aforementioned layered solution and the subsequent drying of the sample along with the filter membrane, the water-rich bacterial cellulose shrinks to a certain extent after losing water. Therefore, the prepared composite material automatically detaches from the filter membrane. Based on this characteristic, the difficulty of separating the composite material from the filter membrane is avoided.

[0097] A third aspect of this application provides a negative electrode current collector comprising the composite material described in the first aspect of this application, or the composite material prepared by the preparation method described in any embodiment of the second aspect of this application.

[0098] Understandably, the negative electrode current collector of this application possesses all the advantages of the aforementioned composite materials, and therefore will not be elaborated upon here. For example, the negative electrode current collector of this application exhibits good flexibility, lithium affinity, and light weight, which plays an important role in improving the energy density of metal batteries and broadening the application scenarios of negative electrode current collectors in heterogeneous batteries.

[0099] A fourth aspect of this application provides a metal battery including the negative electrode current collector described in any of the third aspects of this application.

[0100] For example, the metal battery includes one or more of lithium metal batteries, sodium metal batteries, and potassium metal batteries.

[0101] In one example, the metal battery is an asymmetric battery. For example, the asymmetric battery includes a negative electrode current collector, a lithium metal sheet, and an electrolyte disposed between the negative electrode current collector and the lithium metal sheet. The lithium metal sheet acts as a lithium source. The negative electrode current collector is the type shown in the third aspect of this application.

[0102] In one example, the metal battery is a symmetrical metal battery with a negative electrode. For example, the symmetrical metal battery with a negative electrode includes a positive electrode, a negative electrode, and an electrolyte disposed between the positive and negative electrode. The positive and negative electrode of the symmetrical metal battery are configured with lithium metal of the same capacity. The negative electrode current collector is the negative electrode current collector shown in the third aspect of this application.

[0103] In one example, the thickness of the negative electrode current collector is 0.5 μm to 20 μm. For example, the thickness of the negative electrode current collector includes, but is not limited to, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 17 μm, 18 μm, or 20 μm.

[0104] A fifth aspect of this application provides an electrical device including the metal battery described in the fourth aspect of this application.

[0105] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0106] Example 1

[0107] Embodiment 1 of this application provides a negative electrode current collector and its preparation method, including the following steps:

[0108] (1) Add 1g of lithium fluoride to 15mL of 9mol / L hydrochloric acid to prepare an etching agent.

[0109] (2) 1g of Ti3AlC2 powder was slowly added to the etchant and etched at room temperature for 24h. The etched mixture was then washed with deionized water by centrifugation until the pH reached 5. The solid phase was collected to prepare layered MXene material. In the MXene material, due to the removal of Al atoms, many dangling bonds and defects were formed in the Ti atom layers that were originally bonded to Al.

[0110] (3) Disperse the solid MXene material in 100 mL of water, sonicate in an ice bath (20℃) for 3 h, then centrifuge at 5000 r / min for 30 min, collect the supernatant and prepare the MXene solution.

[0111] (4) Take 10 mL of MXene solution, add silver nitrate to prepare a mixture. The mass concentration of silver nitrate in the mixture is 0.5 mg / mL. Stir for 30 min. Utilize the affinity between dangling bonds, defect sites and silver ions to reduce silver ions on the surface of MXene material sheets, i.e., grow silver nanoparticles in situ to prepare silver-loaded MXene solution.

[0112] (5) The bacterial cellulose blocks were immersed in a 1 mol / L KOH solution and heated at 90°C for 30 min for modification. Then, they were repeatedly washed with deionized water at the same temperature until the pH was neutral. After that, they were put into a juicer and run for 15 min to obtain a modified cellulose solution.

[0113] (6) The silver-loaded MXene solution and the modified cellulose solution were mixed, wherein the ratio of MXene solid content to modified cellulose solid content in the silver-loaded MXene solution was 10:0.5. After stirring for 30 min, hydrogen bonds were formed between the OH groups of the modified bacterial cellulose and the surface functional groups of the MXene material, allowing the modified bacterial cellulose to be loaded onto the surface of the MXene material. After the two were combined, black gel clusters were formed, which then settled. After standing for a period of time, it was obvious that the solution was divided into two parts: the upper part was a clear solution, and the lower part was a gel cluster.

[0114] (7) The above-mentioned layered solution was filtered, and the sample was then vacuum dried along with the filter membrane at a temperature of 40°C for 8 hours. During the drying process, the water-rich bacterial cellulose lost water and shrank to a certain extent. Therefore, the prepared flexible current collector would automatically detach from the filter membrane.

[0115] (8) After completing the above steps, a flexible current collector can be obtained. Cut the prepared flexible current collector into round pieces of appropriate size and put them in a glove box for later use.

[0116] The XRD patterns of MXene prepared in step (3), bacterial cellulose prepared in step (5), and flexible current collector prepared in step (8) of Example 1 are shown in Figure 1. The digital image of the flexible current collector prepared in Example 1 is shown in Figure 2. The scanning electron microscope image of the flexible current collector prepared in Example 1 is shown in Figure 3.

[0117] Example 2

[0118] Embodiment 2 of this application provides a negative electrode current collector and its preparation method, including the following steps:

[0119] (1) 1g of Ti3AlC2 powder was slowly added to 20mL of HF solution with a mass concentration of 49wt% and etched at room temperature for 6h. The etched mixture was washed with deionized water by centrifugation until the pH reached 5, and the solid phase was collected.

[0120] (2) Disperse the solid MXene material in 100 mL of water, sonicate in an ice bath (10℃) for 3 h, then centrifuge at 3500 r / min for 30 min, collect the supernatant and prepare the MXene solution.

[0121] (3) Take 10 mL of MXene solution, add silver nitrate to prepare a mixture. The mass concentration of silver nitrate in the mixture is 0.5 mg / mL. Stir for 30 min. Utilize the affinity between dangling bonds, defect sites and silver ions to reduce silver ions on the surface of MXene material sheets, i.e., grow silver nanoparticles in situ to prepare silver-loaded MXene solution.

[0122] (5) The bacterial cellulose was immersed in a 1 mol / L KOH solution and heated at 90°C for 30 min for modification. Then it was repeatedly washed with deionized water at the same temperature until the pH was neutral. After that, it was put into a juicer and run for 15 min to obtain a modified cellulose solution.

[0123] (6) The silver-loaded MXene solution and the modified cellulose solution were mixed, wherein the solid content of MXene in the silver-loaded MXene solution and the solid content of the modified cellulose were 10:0.5. After stirring for 30 min, hydrogen bonds were formed between the OH groups of the modified bacterial cellulose and the surface functional groups of the MXene material, so that the modified bacterial cellulose was loaded on the surface of the MXene material. After the two were combined, black gel clusters were formed, which then settled. After standing for a period of time, it was obvious that the solution was divided into two parts: the upper part was a clear solution and the lower part was a gel cluster.

[0124] (7) The above-mentioned layered solution was filtered, and the sample was then vacuum dried along with the filter membrane at a temperature of 40°C for 8 hours. During the drying process, the water-rich bacterial cellulose lost water and shrank to a certain extent. Therefore, the prepared flexible current collector would automatically detach from the filter membrane.

[0125] (8) After completing the above steps, a flexible current collector can be obtained. Cut the prepared flexible current collector into round pieces of appropriate size and put them in a glove box for later use.

[0126] Comparative Example 1

[0127] (1) Add 1g of lithium fluoride to 15mL of 9mol / L hydrochloric acid to prepare an etching agent.

[0128] (2) 1g of Ti3AlC2 powder was slowly added to the etchant and etched for 24 hours. The etched mixture was then washed with deionized water by centrifugation until the pH reached 5. The solid phase was then collected to prepare MXene material. In MXene material, due to the removal of Al atoms, many dangling bonds and defects were formed in the Ti atom layer that was originally bonded to Al.

[0129] (3) Disperse the solid MXene material in 100 mL of water, sonicate in an ice bath (20℃) for 3 h, then centrifuge at 5000 r / min for 30 min, collect the supernatant and prepare the MXene solution.

[0130] (4) Take 10 mL of MXene solution, add silver nitrate to prepare a mixture. The mass concentration of silver nitrate in the mixture is 0.5 mg / mL. Stir for 30 min. Utilize the affinity between dangling bonds, defect sites and silver ions to reduce silver ions on the surface of MXene material sheets, i.e., grow silver nanoparticles in situ to prepare silver-loaded MXene solution.

[0131] (5) The silver-loaded MXene solution was filtered, and the sample was then vacuum dried along with the filter membrane at a temperature of 40°C for 8 hours.

[0132] (6) After completing the above steps, a flexible current collector can be obtained. Cut the prepared flexible current collector into round pieces of appropriate size and put them in a glove box for later use.

[0133] Comparative Example 2

[0134] (1) Add 1g of lithium fluoride to 15mL of 9mol / L hydrochloric acid to prepare an etching agent.

[0135] (2) 1g of Ti3AlC2 powder was slowly added to the etchant and etched for 24 hours. The etched mixture was then washed with deionized water by centrifugation until the pH reached 5. The solid phase was then collected to prepare MXene material. In MXene material, due to the removal of Al atoms, many dangling bonds and defects were formed in the Ti atom layer that was originally bonded to Al.

[0136] (3) Disperse the solid MXene material in 100 mL of water, sonicate in an ice bath (20℃) for 3 h, then centrifuge at 5000 r / min for 30 min, collect the supernatant and prepare the MXene solution.

[0137] (4) The bacterial cellulose was immersed in a 1 mol / L KOH solution and heated at 90°C for 30 min for modification. Then it was repeatedly washed with deionized water at the same temperature until the pH was neutral. After that, it was put into a juicer and run for 15 min to obtain a modified cellulose solution.

[0138] (5) Mix the MXene solution and the modified cellulose solution, wherein the solid content of the MXene solution and the solid content of the modified cellulose are 10:0.5. Stir for 30 min. Hydrogen bonds are formed between the OH groups of the modified bacterial cellulose and the surface functional groups of the MXene material, so that the modified bacterial cellulose is loaded on the surface of the MXene material. After the two are combined, black gel clusters are formed and further sedimentation occurs. After standing for a period of time, it can be clearly seen that the solution is divided into two parts: the upper part is a clear solution and the lower part is gel clusters.

[0139] (6) The above-mentioned layered solution was filtered. After the filtration was completed, the sample was vacuum dried along with the filter membrane at a temperature of 40°C for 8 hours.

[0140] (7) After completing the above steps, a flexible current collector can be obtained. Cut the prepared flexible current collector into round pieces of appropriate size and put them in a glove box for later use.

[0141] Test Example 1

[0142] The negative electrode current collector, polypropylene separator, and lithium metal sheet prepared in the examples and comparative examples were assembled into an asymmetric battery with a Li|| negative electrode current collector in a glove box protected by an inert atmosphere. The electrolyte used in the battery includes lithium salt LiTFSI and an organic solvent, wherein the concentration of lithium salt is 1 mol / L, and the organic solvent is ethylene glycol dimethyl ether and 1,3-dioxane in a volume ratio of 1:1.

[0143] Using 0.2mA cm -2 The nucleation overpotential of the asymmetric cell was characterized using a current density of 0.2 mA, and the results are shown in Figure 4. As can be seen from Figure 4, the flexible current collector of Example 1 of this application exhibits a nucleation overpotential of 45 mV when assembled into an asymmetric cell. This low nucleation overpotential indicates that the lower the energy barrier required for lithium nucleation on the substrate, the stronger the lithium affinity. As can be seen from Figure 5, the nucleation overpotential of the asymmetric cell was also characterized using a current density of 0.2 mA. -2 The current density of the flexible current collector in Comparative Example 2 of this application, after being assembled into a lithium symmetric battery, shows a nucleation overpotential of 56 mV. The nucleation overpotential values ​​obtained from tests in other embodiments and comparative examples are shown in Table 1.

[0144] Table 1

[0145]

[0146] Reversible deposition / stripping on the current collector is characterized by coulombic efficiency; therefore, a 1 mA cm⁻¹ current collector is used. -2 The current density was deposited on the negative electrode current collector of Example 1 of this application for 1 hour (discharge process), and then the active lithium was stripped from the negative electrode current collector (charging process). It is assumed that the lithium stripping is complete when the charging voltage reaches 1V. The deposition / stripping efficiency on the current collector can be obtained by dividing the capacity obtained during the charging process by the capacity obtained during the discharging process. The specific test data curves are shown in Figure 6. As can be seen from Figure 6, when using the negative electrode current collector of Example 1, the deposition and stripping process of lithium on the current collector has good reversibility, which can effectively reduce the formation of lithium dendrites.

[0147] Test Example 2

[0148] Based on the asymmetric battery of Test Example 1, a 0.2mA cm -2 The current density was 4.8 mAh cm⁻¹ deposited on the flexible current collector of Example 1. -2 Lithium was used to prepare a composite lithium metal anode. The same electrolyte was used, and a lithium-symmetric battery was assembled based on the aforementioned composite lithium metal anode.

[0149] Performance characterization of lithium symmetric batteries directly reflects the performance of the lithium metal anode prepared based on this current collector and is a crucial step in verifying whether the current collector meets the standards. The cycle performance of the lithium symmetric battery was tested, and the corresponding test results are shown in Figure 7. As can be seen from Figure 7, the anode current collector provided in Example 1 of this application, after being assembled into a lithium symmetric battery, exhibits excellent performance at 1 mA cm⁻¹. -2 1mAh cm -2 It exhibited good cycling performance under the test conditions.

[0150] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0151] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A composite material, characterized in that, include: MXene material, wherein the MXene material includes surface functional groups; Silver nanoparticles, which are grown in situ on the surface of the MXene material sheets; Modified bacterial cellulose, wherein the modified bacterial cellulose comprises bacterial cellulose and oxygen-containing functional groups modified on the surface of the bacterial cellulose; The modified bacterial cellulose is loaded on the surface of the MXene material; The loading mode of the modified bacterial cellulose includes at least the intermolecular interaction between the oxygen-containing functional groups of the modified bacterial cellulose and the surface functional groups of the MXene material.

2. The composite material according to claim 1, characterized in that, The composite material has one or more of the following characteristics: (1) The chemical formula of the MXene material is M n+1 X n T x Where M is a transition metal element, X is carbon or nitrogen element, and T is a transition metal element. x The surface functional group is a surface functional group, where n is 1, 2, or 3, and the surface functional group includes at least one of -OH, -F, and =O; (2) In the composite material, the mass ratio of the MXene material to the modified bacterial cellulose is 10:(0.1~10); (3) In the modified bacterial cellulose, the oxygen-containing functional group includes at least one of -OH and =O.

3. A method for preparing a composite material, characterized in that, Includes the following steps: MXene solution was prepared by etching MAX material with an etchant under stirring conditions. The MXene solution is mixed with silver nitrate, and silver ions undergo a reduction reaction on the surface of the MXene material sheets, so that silver nanoparticles grow in situ on the surface of the MXene material sheets, thus preparing a silver-loaded MXene solution. A modified bacterial cellulose solution was prepared by modifying bacterial cellulose with an alkaline solution; wherein the surface of the modified bacterial cellulose includes oxygen-containing functional groups. The silver-loaded MXene solution and the modified bacterial cellulose solution are mixed to load the modified bacterial cellulose onto the surface of the MXene material, thereby preparing the composite material.

4. The method for preparing the composite material according to claim 3, characterized in that, The step of preparing the MXene solution further includes: The etching agent is prepared by mixing a fluoride salt and hydrochloric acid; The mass-to-volume ratio of the fluoride salt and the hydrochloric acid is 1 g: (10-20) mL.

5. The method for preparing the composite material according to claim 4, characterized in that, The step of preparing the MXene solution has one or more of the following characteristics: (1) The fluoride salt includes one or more of lithium fluoride, sodium fluoride and potassium fluoride; (2) The molar concentration of the hydrochloric acid is 6 mol / L to 12 mol / L; (3) The chemical formula of the MAX material is M m+1 AX m In this context, M is a transition metal element, A is a main group element of group IIIA or IVA, X is carbon or nitrogen, and m is 1, 2, or 3. (4) The mass ratio of the fluoride salt included in the etching agent to the mass of the MAX material is 1:(0.8~1.5); (5) After the etching process, the method further includes: centrifuging and washing the etched mixture, collecting the solid phase, dispersing the solid phase in a dispersant, collecting the supernatant, and preparing the MXene solution.

6. The method for preparing the composite material according to any one of claims 3 to 5, characterized in that, The step of preparing the silver-loaded MXene solution has one or more of the following characteristics: (1) In the solution formed by mixing the MXene solution and silver nitrate, the mass concentration of silver nitrate is 0.3 mg / mL to 1 mg / mL; (2) The process parameters of the reduction reaction include: stirring speed of 50 r / min to 300 r / min.

7. The method for preparing the composite material according to any one of claims 3 to 5, characterized in that, The step of preparing the modified bacterial cellulose solution has one or more of the following characteristics: (1) The alkaline solution includes one or more of KOH and NaOH; (2) The molar concentration of the alkaline solution is 0.8 mol / L to 1.5 mol / L; (3) The process parameters of the modification treatment include: the modification temperature is 40℃~90℃.

8. A negative electrode current collector, characterized in that, The composite material includes the composite material described in claim 1 or 2, or the composite material prepared by the preparation method described in any one of claims 3 to 7.

9. A metal battery, characterized in that, Includes the negative electrode current collector as described in claim 8; the metal battery has one or more of the following characteristics: (1) The thickness of the negative electrode current collector is 0.5 μm to 20 μm; (2) The metal battery includes one or more of lithium metal batteries, sodium metal batteries and potassium metal batteries.

10. An electrical appliance, characterized in that, Including the metal battery as described in claim 9.

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