A modified structure for a negative electrode, a lithium metal negative electrode including the modified structure for a negative electrode, and applications.

Abstract

This invention discloses a modified structure for an anode, a lithium metal anode containing the modified structure, and its applications, belonging to the field of new energy technology. The modified structure for the anode includes a tetramethylethylenediamine (TEDAM)-modified cellulose modification layer. The raw materials for the TDDAM-modified cellulose modification layer include cellulose, tetramethylethylenediamine, and a binder. In preparation, tetramethylethylenediamine is first reacted with cellulose to obtain TDDAM-modified cellulose, which is then mixed with the binder to form a slurry, which is then coated onto a substrate to form the modification layer. The modification layer of this invention utilizes the properties of tetramethylethylenediamine as a Lewis base catalyst to promote the reaction of amino groups with lithium metal to generate highly ionicly conductive Li3N, which helps to improve the ion transport rate of the lithium metal electrode. Simultaneously, the three-dimensional network structure constructed by nanoscale cellulose can uniformly disperse the lithium ion flux, suppress the growth of lithium dendrites and the instability of the solid electrolyte interface, and improve the safety of lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a modified structure for a negative electrode, a lithium metal negative electrode containing the modified structure for a negative electrode, and its applications. Background Technology

[0002] Lithium metal anode modification refers to the surface modification of lithium metal anodes to improve the performance and safety of lithium-ion batteries. Lithium metal anodes offer advantages in high capacity and high energy density in lithium-ion batteries, but they are prone to dendrite growth, electrolyte decomposition, and safety hazards during charge-discharge cycles. Therefore, surface modification is necessary to address these issues. Surface modification of lithium metal anodes aims to improve their electrochemical performance, reduce dendrite growth, enhance cycle stability, and improve safety. Common surface modification methods for lithium metal anodes include coating modification, nanostructure design, electrolyte additives, and chemical modification. While these methods can improve the performance of lithium metal anodes and increase battery cycle life and safety, providing important technical support for the commercial application of lithium-ion batteries, they still face challenges such as poor stability and durability, high cost, and difficulty in large-scale preparation, limiting their commercial application. Overcoming these difficulties requires in-depth research into novel surface modification materials and technologies, improving the stability and durability of modified layers, refining preparation processes to enhance consistency and repeatability, reducing costs and improving safety, and simultaneously seeking surface modification methods with good scalability. Summary of the Invention

[0003] The purpose of this invention is to provide a modified structure for the negative electrode to solve the problems of dendrite growth, electrolyte decomposition, and poor stability and safety of lithium metal batteries during long-term charge and discharge processes in the prior art.

[0004] The present invention also aims to provide a lithium metal anode with a modified structure for the anode, which has excellent cycle stability and safety.

[0005] Another objective of this invention is to provide an application of a modified negative electrode structure in lithium metal batteries.

[0006] In a first aspect, the present invention discloses a modified structure for a negative electrode, the modified structure comprising a tetramethylethylenediamine-modified cellulose modification layer; The raw materials for the tetramethylethylenediamine-modified cellulose trimming layer include cellulose, tetramethylethylenediamine, and binder; The mass ratio of cellulose to tetramethylethylenediamine is 1:(1-3).

[0007] By employing the above technical solutions, when tetramethylethylenediamine reacts with cellulose, on the one hand, tetramethylethylenediamine can act as a Lewis base catalyst in the cellulose modification reaction, promoting the reaction, increasing its activity, and facilitating the formation of amino group products. This makes it easier for the amino groups to react with lithium metal to form Li3N, which has high ionic conductivity and stability. This helps to improve the ion transport rate of the lithium metal electrode, thereby improving the charge-discharge performance of the battery, suppressing the growth of lithium dendrites and the instability of the solid electrolyte interface, and improving battery safety. On the other hand, the cellulose modification layer on the surface of the lithium metal anode can act as a protective film, enhancing the chemical and physical stability of the lithium metal electrode, improving the stability between the lithium metal electrode and the electrolyte, reducing the risk of thermal runaway or combustion, and providing a more uniform lithium deposition and dissolution process. This helps to reduce the growth and accumulation of lithium dendrites, improve battery cycle life, and enhance the cycle stability of the lithium metal electrode. Furthermore, the cellulose modified with tetramethylethylenediamine can increase the lithium ion transference number and strengthen the adsorption energy between lithium metal and cellulose, thereby improving the lithium ion diffusion rate and transport speed.

[0008] Preferably, the cellulose includes one or a combination of several of hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose ether, methylcellulose, ethylcellulose, cellulose sulfate and carboxymethyl cellulose ether.

[0009] The weight-average molecular weight of cellulose is ≥100,000, and the particle size of cellulose is in the nanometer range.

[0010] More preferably, the particle size of cellulose is 10–150 nm.

[0011] Preferably, the binder comprises one or a combination of several of sodium polyacrylate, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, and polyvinylidene fluoride.

[0012] Preferably, the tetramethylethylenediamine-modified cellulose layer is prepared by the following method: S1. Dissolve tetramethylethylenediamine in a first solvent to obtain a tetramethylethylenediamine solution; dissolve cellulose in a second solvent to obtain a cellulose solution; S2. Tetramethylethylenediamine solution is slowly added dropwise to cellulose solution, and the reaction is carried out at a temperature of 25-50℃ and a rotation speed of 400-2000 rpm / min for 2-12 hours. After centrifugation, washing and drying, tetramethylethylenediamine modified cellulose is obtained. S3. Tetramethylethylenediamine-modified cellulose and binder are added to the third solvent and stirred at 1500-3000 rpm / min for 2-5 hours to obtain a slurry; S4. Form a tetramethylethylenediamine-modified cellulose modification layer on the substrate using the slurry.

[0013] Preferably, the first solvent includes one or a combination of several of diethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, toluene, and acetonitrile.

[0014] Preferably, the second solvent includes one or a combination of several of water, methanol, ethanol, sodium hydroxide, dimethyl sulfoxide, and N,N-dimethylformamide.

[0015] Preferably, the third solvent includes one or a combination of several of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, ethanol, acetic acid, and dichloromethane.

[0016] Preferably, the cellulose solution concentration is 5% to 10%, the cellulose dissolution temperature is 60 to 80°C, and the cellulose stirring speed is 400 to 2000 rpm / min.

[0017] Preferably, in step S3, the solid content of the slurry is 20% to 35%.

[0018] Preferably, in step S4, the mass ratio of tetramethylethylenediamine modified cellulose to binder is (8-10):1.

[0019] Preferably, in step S4, the thickness of the tetramethylethylenediamine-modified cellulose layer is 2–10 μm; Preferably, in step S4, the substrate includes one or a combination of copper foil, aluminum foil, stainless steel foil or lithium foil; Preferably, in step S4, the method of forming a tetramethylethylenediamine modified cellulose layer on the substrate by the slurry includes one or a combination of one or more of the following processes: blade coating, spin coating, or electrospinning.

[0020] Preferably, the coating speed for both blade coating and spin coating processes is 10–30 m / min.

[0021] Preferably, in the electrospinning process, the solution feed rate is 0.5–2.5 mL / h. -1 .

[0022] Secondly, the present invention also discloses a lithium metal anode, comprising a modified structure for the anode and a lithium metal substrate; Methods for combining lithium metal substrates with modified structures for anodes include one or a combination of mechanical rolling, lithium implantation, electrochemical deposition, electrospinning, and blade coating processes.

[0023] Preferably, the pressure of the mechanical roller is 8 to 12 MPa.

[0024] Thirdly, this invention also discloses the application of a modified structure for the negative electrode in lithium metal batteries.

[0025] The beneficial effects of this invention are: 1. This invention constructs a composite modification layer with both high ionic conductivity and excellent mechanical stability by chemically modifying tetramethylethylenediamine with cellulose, significantly improving the overall performance of lithium metal anodes. Specifically, tetramethylethylenediamine, as a Lewis base catalyst, effectively promotes the introduction of amino groups during the reaction with cellulose. These amino groups readily react with lithium metal in the electrochemical environment to form a highly ionicly conductive Li3N interfacial layer, thereby significantly increasing the lithium ion transference number and diffusion rate, reducing interfacial impedance, and optimizing the charge-discharge performance of the battery. Simultaneously, cellulose itself possesses good film-forming properties and flexibility, enabling it to form a dense and uniform protective layer on the lithium metal surface. This effectively isolates the electrolyte from direct contact with lithium metal, reduces side reactions, and inhibits the nucleation and growth of lithium dendrites, thereby improving the structural stability and electrochemical reversibility of the electrode. Furthermore, the tetramethylethylenediamine-modified cellulose retains its three-dimensional network structure of nanofibers. This structure not only possesses excellent mechanical strength and flexibility, effectively buffering the volume expansion of lithium metal during charging and discharging, but its abundant porosity also provides rapid diffusion channels for lithium ions, increasing the lithium ion transport number and strengthening the adsorption energy between lithium metal and the modification layer. This results in uniform deposition of lithium ions on the electrode surface, avoiding localized lithium accumulation and the formation of dead lithium, significantly extending the battery's cycle life. In addition, the modified cellulose layer also enhances the interfacial bonding between lithium metal and the substrate, preventing peeling or detachment during long-term cycling, further improving the battery's cycle life and safety.

[0026] 2. This invention successfully constructs a high-efficiency, stable, and safe lithium metal anode modification layer through a simple and controllable preparation process. It not only solves the problems of dendrite growth and interface instability in traditional lithium metal anodes in practical applications, but also provides a new technical path for the development of high-energy-density lithium metal batteries, which has important scientific significance and industrial application value. Attached Figure Description

[0027] Figure 1 This is a cross-sectional scanning electron microscope image of a lithium metal anode with a tetramethylethylenediamine-modified cellulose layer proposed in Example 1 of this invention. Figure 2 This paper compares the coulombic efficiency curves of Example 1 and Comparative Example 1 of a lithium metal battery with a tetramethylethylenediamine-modified cellulose negative electrode assembly proposed in this invention. Figure 3 The cycling performance curves of Examples 1-4 and Comparative Examples 1-4 of a lithium metal battery with a tetramethylethylenediamine modified cellulose electrode assembly proposed in this invention are shown. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0029] A modified structure for an anode, the modified structure comprising a tetramethylethylenediamine-modified cellulose modification layer; The raw materials for the tetramethylethylenediamine-modified cellulose trimming layer include cellulose, tetramethylethylenediamine, and binder; The mass ratio of cellulose to tetramethylethylenediamine is 1:(1-3).

[0030] By employing the above technical solutions, when tetramethylethylenediamine reacts with cellulose, on the one hand, tetramethylethylenediamine can act as a Lewis base catalyst in the cellulose modification reaction, promoting the reaction, increasing its activity, and facilitating the formation of amino group products. This makes it easier for the amino groups to react with lithium metal to form Li3N, which has high ionic conductivity and stability. This helps to improve the ion transport rate of the lithium metal electrode, thereby improving the charge-discharge performance of the battery, suppressing the growth of lithium dendrites and the instability of the solid electrolyte interface, and improving battery safety. On the other hand, the cellulose modification layer on the surface of the lithium metal anode can act as a protective film, enhancing the chemical and physical stability of the lithium metal electrode, improving the stability between the lithium metal electrode and the electrolyte, reducing the risk of thermal runaway or combustion, and providing a more uniform lithium deposition and dissolution process. This helps to reduce the growth and accumulation of lithium dendrites, improve battery cycle life, and enhance the cycle stability of the lithium metal electrode. Furthermore, the cellulose modified with tetramethylethylenediamine can increase the lithium ion transference number and strengthen the adsorption energy between lithium metal and cellulose, thereby improving the lithium ion diffusion rate and transport speed.

[0031] In some embodiments, cellulose includes one or a combination of several of hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose ether, methylcellulose, ethylcellulose, cellulose sulfate, and carboxymethyl cellulose ether.

[0032] Cellulose has a weight-average molecular weight ≥100,000 and a particle size in the nanometer range, more specifically, a particle size of 10–150 nm.

[0033] By employing the above technical solutions and selecting cellulose with a weight-average molecular weight ≥100,000 and a particle size in the nanoscale, a three-dimensional network structure can be effectively constructed, enhancing the mechanical strength and flexibility of the modification layer. Nanoscale cellulose possesses a high specific surface area and abundant porous structure, which helps to uniformly disperse lithium-ion flux, avoid localized lithium deposition, and thus inhibit the growth of lithium dendrites. Simultaneously, high molecular weight cellulose provides excellent film-forming properties and interfacial adhesion, ensuring that the modification layer is not easily broken or detached during long-term cycling, further improving the structural stability and electrochemical reversibility of the lithium metal anode.

[0034] In some embodiments, the binder comprises one or a combination of several of sodium polyacrylate, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, and polyvinylidene fluoride.

[0035] By adopting the above technical solutions, the adhesion between the modified layer and the substrate can be effectively improved, ensuring that the modified layer does not peel off during charging and discharging. The binder also plays a role in dispersing and stabilizing the modified cellulose particles, forming a uniform and dense composite film, which further prevents direct contact between the electrolyte and lithium metal, reduces side reactions, and improves battery safety and cycle life.

[0036] In some embodiments, the tetramethylethylenediamine-modified cellulose layer is prepared by the following method: S1. Dissolve tetramethylethylenediamine in a first solvent to obtain a tetramethylethylenediamine solution; dissolve cellulose in a second solvent to obtain a cellulose solution; S2. Tetramethylethylenediamine solution is slowly added dropwise to cellulose solution, and the reaction is carried out at a temperature of 25-50℃ and a rotation speed of 400-2000 rpm / min for 2-12 hours. After centrifugation, washing and drying, tetramethylethylenediamine modified cellulose is obtained. S3. Tetramethylethylenediamine-modified cellulose and binder are added to the third solvent and stirred at 1500-3000 rpm / min for 2-5 hours to obtain a slurry; S4. Form a tetramethylethylenediamine-modified cellulose modification layer on the substrate using the slurry.

[0037] By adopting the above technical solutions, steps S1-S4 construct a controllable and repeatable process for preparing the modified layer. In S1, the solvent selection and dissolution conditions ensured the complete dissolution and uniform mixing of cellulose and tetramethylethylenediamine; in S2, the reaction conditions precisely controlled the degree of modification, ensuring that tetramethylethylenediamine was effectively grafted onto cellulose to generate highly reactive amino groups; in S3, the preparation of the high-solids-content slurry ensured the density and uniformity of the modified layer; and in S4, multiple coating methods adapted to different application scenarios, with controllable thickness, meeting the needs of industrial production.

[0038] In some embodiments, the first solvent includes one or a combination of several of diethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, toluene, and acetonitrile.

[0039] The second solvent includes one or a combination of several of the following: water, methanol, ethanol, sodium hydroxide, dimethyl sulfoxide, and N,N-dimethylformamide.

[0040] The third solvent includes one or a combination of several of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, ethanol, acetic acid, and dichloromethane.

[0041] By adopting the above technical solutions, the selection of the first, second, and third solvents is based on the solubility and reaction compatibility of the raw materials, ensuring the efficient reaction between tetramethylethylenediamine and cellulose while avoiding the introduction of impurities or side reactions. The polarity, volatility, and toxicity of the solvents have also been optimized to ensure reaction efficiency while also taking into account operational safety and environmental protection requirements.

[0042] In some embodiments, the concentration of the cellulose solution is 5% to 10%, the dissolution temperature of the cellulose is 60 to 80°C, and the stirring speed of the cellulose is 400 to 2000 rpm / min.

[0043] In some embodiments, in step S3, the solid content of the slurry is 20% to 35%.

[0044] By adopting the above technical solutions and controlling the solid content of the slurry between 20% and 35%, both the fluidity and uniformity of the slurry during the coating process can be guaranteed, and a dense, crack-free finishing layer can be formed after drying. Too low a solid content can lead to an excessively thin and uneven coating; too high a solid content may result in coating difficulties and increased coating brittleness.

[0045] In some embodiments, in step S4, the mass ratio of tetramethylethylenediamine modified cellulose to binder is (8-10):1.

[0046] By adopting the above technical solution, the electrochemical performance can be maximized while ensuring the structural stability of the modified layer. Modified cellulose, as the functional host, provides high ionic conductivity and a three-dimensional network framework through Li3N generation, while the binder ensures strong adhesion between the modified layer and the substrate, as well as the adhesion within the coating. If the binder ratio is too low, the modified layer is prone to cracking or peeling, affecting long-term cycle stability; if the binder ratio is too high, it may coat the active sites of the modified cellulose, hindering Li3N generation and increasing ion transport resistance, leading to increased impedance. This preferred ratio offers optimal interfacial bonding, ion conductivity, and mechanical toughness, effectively balancing the flexibility and structural integrity of the modified layer, further improving the cycle life and safety of the lithium metal anode.

[0047] In some embodiments, in step S4, the thickness of the tetramethylethylenediamine-modified cellulose modification layer is 2–10 μm; By employing the above technical solutions, the thickness of the tetramethylethylenediamine-modified cellulose modification layer is controlled to be 2–10 μm, which provides sufficient physical barriers and ion transport channels without significantly increasing the battery's internal resistance or volume. Too thin a layer leads to insufficient protection, making it easier for lithium dendrites to penetrate; too thick a layer increases ion diffusion paths, affecting rate performance.

[0048] In some embodiments, in step S4, the substrate includes one or a combination of copper foil, aluminum foil, stainless steel foil or lithium foil; By adopting the above technical solutions, the substrate can be selected from copper foil, aluminum foil, stainless steel foil, or lithium foil, possessing good conductivity and mechanical strength, and capable of forming a stable interface bond with the modification layer. Different substrates are suitable for different types of battery structures, meeting diverse application requirements.

[0049] In some embodiments, in step S4, the method of forming a tetramethylethylenediamine-modified cellulose modification layer on the substrate by means of one or a combination of a blade coating process, a spin coating process, or an electrospinning process.

[0050] The coating speed for both blade coating and spin coating processes is 10–30 m / min.

[0051] In the electrospinning process, the solution feed rate is 0.5–2.5 mL / h. -1 .

[0052] By adopting the above technical solutions, processes such as blade coating, spin coating, and electrospinning can be flexibly selected according to production scale and precision requirements. Blade coating is suitable for large-area continuous production, spin coating is suitable for high-precision thin film preparation, and electrospinning can construct three-dimensional network structures. Optimization of coating speed and feed rate ensures the uniformity and thickness controllability of the modified layer, improving product consistency and repeatability.

[0053] A lithium metal anode includes an anode modification structure and a lithium metal substrate; Methods for combining lithium metal substrates with modified structures for anodes include one or a combination of mechanical rolling, lithium implantation, electrochemical deposition, electrospinning, and blade coating processes.

[0054] Preferably, the pressure of the mechanical roller is 8 to 12 MPa.

[0055] By employing the above technical solutions, methods such as mechanical rolling, lithium implantation, and electrochemical deposition can achieve a strong bond between the modification layer and the lithium metal substrate. The mechanical rolling pressure is controlled at 8–12 MPa to ensure tight interface contact while avoiding excessive compaction that could damage the modification layer, thus ensuring the overall performance of the lithium metal anode.

[0056] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0057] Example Example 1: A lithium metal anode comprising a modified structure for the anode is prepared by the following method: S1. In an argon glove box (water and oxygen content <0.1ppm), 15g of tetramethylethylenediamine was dissolved in 50mL of N,N-dimethylformamide and stirred at 2000r / min for 2h to obtain a homogeneous tetramethylethylenediamine solution. 5g of hydroxypropyl cellulose with a weight average molecular weight of 120,000 and a particle size of 25nm was dissolved in 100mL of 5% sodium hydroxide solution, heated to 60℃, and stirred at 2000r / min for 2h to obtain a homogeneous hydroxypropyl cellulose solution.

[0058] S2. Tetramethylethylenediamine solution was slowly added dropwise to hydroxypropyl cellulose solution. The reaction was carried out at 25°C and stirred at 1000 r / min for 2 h to allow the reaction to proceed fully. The reaction mixture was centrifuged to separate the solid precipitate from the solution. The precipitate was then washed with ethanol and centrifuged again. Finally, the washed product was dried to remove residual solvent.

[0059] S3: In an argon glove box (water and oxygen content both <0.1ppm), prepare a slurry with a solid content of 25%: Add 22.5g of tetramethylethylenediamine-modified hydroxypropyl cellulose and 2.5g of polyvinylidene fluoride to 100ml of N,N-dimethylformamide solution, and stir for 4h at a speed of 2000r / min to obtain a uniform slurry; S4. Using a scraping process, the slurry is uniformly coated onto a 12μm copper foil at a coating speed of 15m / min to form a 5μm thick tetramethylethylenediamine-modified hydroxypropyl cellulose modified layer. S5. The obtained tetramethylethylenediamine-modified hydroxypropyl cellulose modification layer is mechanically rolled with a 100μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain a lithium metal anode containing a tetramethylethylenediamine-modified hydroxypropyl cellulose modification layer.

[0060] Example 2: A lithium metal anode comprising a modified structure for the anode is prepared by the following method: S1. In an argon glove box (water and oxygen content <0.1ppm), 15g of tetramethylethylenediamine was dissolved in 50mL of dimethyl sulfoxide and stirred at 1500r / min for 2h to obtain a homogeneous tetramethylethylenediamine solution. 10g of hydroxypropyl methylcellulose with a weight average molecular weight of 150,000 and a particle size of 35nm was dissolved in 100mL of 5% dimethyl sulfoxide solution, heated to 60℃, and stirred at 2000r / min for 2h to obtain a homogeneous hydroxypropyl methylcellulose solution.

[0061] S2. Tetramethylethylenediamine solution is slowly added dropwise to hydroxypropyl methylcellulose solution. The reaction temperature is 30℃ and the stirring speed is 1000 r / min for 2 hours to allow the reaction to proceed fully. The reaction mixture is centrifuged to separate the solid precipitate from the solution. The precipitate is then washed with ethanol and centrifuged again. Finally, the washed product is dried to remove residual solvent.

[0062] S3: In an argon glove box (water and oxygen content both <0.1ppm), prepare a slurry with a solid content of 35%: Add 31.5g of tetramethylethylenediamine-modified hydroxypropyl methylcellulose and 3.5g of polyvinylidene fluoride to 100mL of N,N-dimethylformamide solution, and stir for 4h at a speed of 2000r / min to obtain a uniform slurry; S4. Using a spin coating process, the slurry is uniformly coated onto a 12μm copper foil at a coating speed of 15m / min to form a 3μm thick tetramethylethylenediamine-modified hydroxypropyl methylcellulose modified layer. S5. The obtained tetramethylethylenediamine-modified hydroxypropyl methylcellulose modification layer is mechanically rolled with a 100μm lithium sheet at a mechanical rolling pressure of 10 MPa to obtain a lithium metal anode containing a tetramethylethylenediamine-modified hydroxypropyl methylcellulose modification layer.

[0063] Example 3: A lithium metal anode comprising a modified structure for the anode is prepared by the following method: S1. In an argon glove box (water and oxygen content <0.1ppm), 15g of tetramethylethylenediamine was dissolved in 50mL of diethyl ether and stirred at 1000r / min for 2h to obtain a homogeneous tetramethylethylenediamine solution. 8g of hydroxyethyl cellulose with a weight average molecular weight of 100,000 and a particle size of 80nm was dissolved in 100mL of 5% methanol solution, heated to 60℃, and stirred at 2000r / min for 2h to obtain a homogeneous hydroxyethyl cellulose solution.

[0064] S2. Tetramethylethylenediamine solution is slowly added dropwise to hydroxyethyl cellulose solution. The reaction temperature is 25℃ and the stirring speed is 1000 r / min for 2 hours to allow the reaction to proceed fully. The reaction mixture is centrifuged to separate the solid precipitate from the solution. The precipitate is then washed with ethanol and centrifuged again. Finally, the washed product is dried to remove residual solvent.

[0065] S3: In an argon glove box (water and oxygen content < 0.1 ppm), prepare a slurry with a solid content of 20%: add 18 g of tetramethylethylenediamine-modified hydroxyethyl cellulose and 2 g of sodium polyacrylate to 100 mL of N,N-dimethylformamide (DMF) solution and stir for 4 h at a speed of 2000 r / min to obtain a uniform slurry. S4. Transfer the slurry to an electrospinning needle and perform electrospinning on a copper foil substrate, wherein the solution feed rate is 0.5 mL / h. -1 An external voltage of 22kV was applied, the distance between the spinneret and the copper foil substrate was 10cm, the temperature was 35℃, and the relative humidity was 30%, resulting in a 5μm thick tetramethylethylenediamine-modified hydroxyethyl cellulose layer on the load and the copper foil substrate. S5. The obtained tetramethylethylenediamine-modified hydroxyethyl cellulose modification layer is mechanically rolled with an 80μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain a lithium metal anode containing a tetramethylethylenediamine-modified hydroxyethyl cellulose modification layer.

[0066] Example 4: A lithium metal anode comprising a modified structure for the anode is prepared by the following method: S1. In an argon glove box (water and oxygen content <0.1ppm), 15g of tetramethylethylenediamine was dissolved in 50mL of N,N-dimethylformamide and stirred at 1000r / min for 2h to obtain a homogeneous tetramethylethylenediamine solution. 7g of carboxymethyl cellulose with a weight average molecular weight of 145000 and a particle size of 95nm was dissolved in 100mL of 5% sodium hydroxide solution, heated to 60℃, and stirred at 2000r / min for 2h to obtain a homogeneous carboxymethyl cellulose solution.

[0067] S2. Tetramethylethylenediamine solution is slowly added dropwise to carboxymethyl cellulose solution. The reaction temperature is 25℃ and the stirring speed is 1000 r / min for 2 hours to allow the reaction to proceed fully. The reaction mixture is centrifuged to separate the solid precipitate from the solution. The precipitate is then washed with ethanol and centrifuged again. Finally, the washed product is dried to remove residual solvent.

[0068] S3: In an argon glove box (water and oxygen content < 0.1 ppm), prepare a slurry with a solid content of 35%: Add 31.5 g of tetramethylethylenediamine-modified carboxymethyl cellulose and 3.5 g of polyvinylidene fluoride to 100 mL of N,N-dimethylformamide solution, and stir for 4 h at a speed of 2000 r / min to obtain a uniform slurry. S4. Using a scraping process, the slurry is uniformly coated onto a 12μm aluminum foil at a coating speed of 15m / min to form a 5μm thick tetramethylethylenediamine-modified carboxymethyl cellulose modification layer. S5. The obtained tetramethylethylenediamine-modified carboxymethyl cellulose modification layer is mechanically rolled with a 60μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain a lithium metal anode containing a tetramethylethylenediamine-modified carboxymethyl cellulose modification layer.

[0069] Comparative Example Comparative Example 1: A lithium metal anode comprising a modified structure for the anode is prepared by the following method: S1. Add 18g of hydroxypropyl cellulose with a weight average molecular weight of 120,000 and a particle size of 25nm and 2g of polyvinylidene fluoride to 100mL of N,N-dimethylformamide solution and stir at 2000r / min for 2h to fully dissolve and obtain a uniform slurry. S2. Using a scraping process, the slurry in S1 is uniformly coated onto a 12μm copper foil at a coating speed of 15m / min to prepare a 5μm thick hydroxypropyl cellulose modified layer. S3. The obtained hydroxypropyl cellulose modified layer is mechanically rolled with a 100μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain the modified composite lithium metal anode.

[0070] Comparative Example 2: A lithium metal anode comprising a modified structure for the anode was prepared by the following method: S1. Add 22.5g of hydroxypropyl methylcellulose with a weight average molecular weight of 150,000 and a particle size of 50nm and 2.5g of polyvinylidene fluoride to 100mL of dimethylformamide solution and stir for 2h at a speed of 2000r / min to fully dissolve it and obtain a uniform slurry. S2. Using a scraping process, the slurry in S1 is uniformly coated onto a 12μm copper foil at a coating speed of 15m / min to prepare a 3μm thick hydroxypropyl methylcellulose modified layer. S3. The obtained hydroxypropyl methylcellulose modified layer is mechanically rolled with a 100μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain the modified composite lithium metal anode.

[0071] Comparative Example 3: A lithium metal anode comprising a modified structure for the anode was prepared by the following method: S1. Add 18g of hydroxyethyl cellulose with a weight average molecular weight of 120,000 and a particle size of 25nm and 2g of polyvinylidene fluoride to 100ml of methanol solution and stir for 2h at a speed of 2000r / min to fully dissolve and obtain a uniform slurry. S2. Transfer the slurry obtained in S1 to an electrospinning needle and perform electrospinning on a copper foil substrate, wherein the solution feed rate is 1 mL / h. -1 An external voltage of 25kV was applied, the distance between the spinneret and the current collector was 10cm, the temperature was 35℃, and the relative humidity was 30%, resulting in a hydroxyethyl cellulose modified layer with a thickness of 5μm loaded on the substrate.

[0072] S3. The obtained hydroxyethyl cellulose modified layer is mechanically rolled with a 100μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain the modified composite lithium metal anode.

[0073] Comparative Example 4: A lithium metal anode comprising a modified structure for the anode was prepared by the following method: S1. Add 27g of carboxymethyl cellulose with a weight average molecular weight of 180,000 and a particle size of 100nm and 3g of polyvinylidene fluoride to 100mL of dimethylformamide solution and stir at 2000r / min for 2h to fully dissolve and obtain a homogeneous solution. S2. Using a blade coating process, the solution obtained in S1 is uniformly coated onto a 12μm copper foil at a coating speed of 15m / min to prepare a carboxymethyl cellulose modified layer with a thickness of 5μm. S3. The obtained carboxymethyl cellulose modified layer is mechanically rolled with a 100μm lithium sheet at a mechanical rolling pressure of 10MPa to obtain the modified composite lithium metal anode.

[0074] Performance testing: 1. The lithium metal anodes obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were assembled into lithium metal batteries, and their electrochemical performance was tested. The specific lithium metal battery manufacturing process is as follows: Positive electrode preparation: LiNi was prepared using a vacuum stirrer. 0.8 Co 0.1 Mn 0.1O2, conductive agent (sp), and binder (PVDF) are mixed evenly in a ratio of 98:1:1, and then N-methylpyrrolidone (NMP) solvent is added and stirred into a slurry. The slurry is then evenly coated onto copper foil using a coating machine and dried to form a positive electrode sheet. Subsequently, the electrode sheet is baked at 85°C in a dryer to remove moisture and keep it dry. After drying, the electrode sheet is compacted using a roller press and a double roller press, and finally cut into the specifications required for the battery before use. Negative electrode preparation: In a glove box filled with argon (water and oxygen content <0.1ppm), the lithium metal negative electrode sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were die-cut into the specifications required for the battery using a die-cutting machine and then set aside for use. Electrolyte preparation: 1 M lithium bis(fluorosulfonyl)imide (LiFSI) was dissolved in an equal volume of 1,3-dioxolane (DOL) and dimethyl ethylene glycol (DME) to obtain a lithium metal battery electrolyte.

[0075] Cell fabrication: The prepared positive electrode sheet, negative electrode sheet and polyethylene separator with a thickness of 16μm are stacked to form a cell. The cell is then installed in an aluminum-plastic film shell, and the tabs are welded and the sides are sealed. Then, the electrolyte is injected in a glove box filled with argon gas (water and oxygen content are both <0.1 ppm). After encapsulation, the cell is allowed to stand, form, degas, age and capacity test to finally obtain a lithium metal battery.

[0076] 2. Cyclic capability test: At 25℃, the lithium metal battery is charged to 4.3V at a constant current and constant voltage of 0.1C, with a cutoff current of 0.05C. After resting for 10 minutes, it is discharged to 3.0V at a constant current of 0.3C. The number of cycles is recorded.

[0077] 3. Internal resistance test: The lithium metal batteries prepared in the examples and comparative examples were tested for internal resistance at 25°C using an internal resistance meter, and the internal resistance data were recorded.

[0078] 4. Needle penetration test: At 25℃, charge the lithium metal battery to 4.3V using a constant current and constant voltage at 0.1C, with a cutoff current of 0.05C. Place one K-type thermocouple and monitor the voltage (acquisition speed 10ms) on each side of the penetration point. Place the sample in the clamp mold, tighten the nuts on each stud with a torque wrench to a torque of 0.8Nm, place the clamp mold flat on the test platform, and fix the clamp mold (to prevent it from shifting when removing the needle). Use a 3mm diameter stainless steel needle to vertically penetrate the geometric center of the large surface of the battery at a speed of 10mm / s until it is completely pierced. Stop the test after 60 minutes of rest or when the sample shows signs of thermal runaway. Record whether the battery catches fire or explodes. If the sample does not catch fire or explode within 60 minutes, it is considered to have passed; if the sample catches fire or explodes within 60 minutes, it is considered to have failed.

[0079] The results of the above performance tests are listed in Table 1: Table 1 Performance test results

[0080] from Figure 1 The scanned image of the lithium sheet after modification with tetramethylethylenediamine-modified cellulose shows that the surface of the lithium sheet after modification with tetramethylethylenediamine-modified cellulose is smooth and flat, which helps to reduce the growth and accumulation of lithium dendrites and improve the cycling stability of the lithium metal electrode. Figure 2 , 3 It can be seen that the cycle performance of the soft-pack battery made with lithium sheet modified with tetramethylethylenediamine-modified cellulose is significantly improved.

[0081] This invention significantly improves the electrochemical performance and safety of batteries by constructing a tetramethylethylenediamine-modified cellulose modification layer on the surface of a lithium metal anode. Tetramethylethylenediamine, acting as a Lewis base catalyst, promotes the reaction of amino groups with lithium metal to generate highly ionicly conductive Li3N, effectively reducing interfacial impedance and increasing lithium-ion transference number and diffusion rate. Simultaneously, the three-dimensional network structure constructed from nanoscale cellulose uniformly disperses lithium-ion flux, suppressing lithium dendrite growth and solid electrolyte interface instability. Experimental results show that the battery in the example exhibits an impedance as low as 12.384 mΩ, a maximum cycle life of 496 cycles, a stable coulombic efficiency above 99%, and passes all nail penetration tests. In contrast, the comparative battery exhibits high impedance, short cycle life, and poor safety. This indicates that the modified cellulose modification layer synergistically enhances ion conduction, mechanical stability, and interfacial compatibility.

[0082] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A modified structure for a negative electrode, characterized in that, The modified structure includes a tetramethylethylenediamine-modified cellulose modification layer; The raw materials for the tetramethylethylenediamine-modified cellulose trimming layer include cellulose, tetramethylethylenediamine, and a binder; The mass ratio of cellulose to tetramethylethylenediamine is 1:(1-3).

2. The modified structure for the negative electrode according to claim 1, characterized in that, The cellulose includes cellulose derivatives, which include one or a combination of several of the following: hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose ether, methylcellulose, ethyl cellulose, cellulose sulfate, and carboxymethyl cellulose ether. The cellulose has a weight-average molecular weight ≥100,000 and a particle size in the nanometer range.

3. The modified structure for the negative electrode according to claim 1, characterized in that, The adhesive comprises one or a combination of several of sodium polyacrylate, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, and polyvinylidene fluoride.

4. The modified structure for the negative electrode according to claim 1, characterized in that, The tetramethylethylenediamine-modified cellulose layer was prepared by the following method: S1. Dissolve tetramethylethylenediamine in a first solvent to obtain a tetramethylethylenediamine solution; dissolve cellulose in a second solvent to obtain a cellulose solution; S2. Tetramethylethylenediamine solution is slowly added dropwise to cellulose solution, and the reaction is carried out at a temperature of 25-50℃ and a rotation speed of 400-2000 rpm / min for 2-12 hours. After centrifugation, washing and drying, tetramethylethylenediamine modified cellulose is obtained. S3. Tetramethylethylenediamine-modified cellulose and binder are added to the third solvent and stirred at 1500-3000 rpm / min for 2-5 hours to obtain a slurry; S4. Form a tetramethylethylenediamine-modified cellulose modification layer on the substrate using the slurry.

5. The modified structure for the negative electrode according to claim 4, characterized in that, The first solvent includes one or a combination of several of diethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, toluene, and acetonitrile; The second solvent includes one or a combination of several of the following: water, methanol, ethanol, sodium hydroxide, dimethyl sulfoxide, and N,N-dimethylformamide; The third solvent includes one or a combination of several of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, ethanol, acetic acid, and dichloromethane.

6. The modified structure for the negative electrode according to claim 4, characterized in that, In step S3, the solid content of the slurry is 20% to 35%.

7. The modified structure for the negative electrode according to claim 4, characterized in that, In step S4, the thickness of the tetramethylethylenediamine-modified cellulose layer is 2–10 μm.

8. A lithium metal anode, comprising the anode modification structure as described in any one of claims 1-7, characterized in that, It also includes lithium metal substrates; The method for combining the lithium metal substrate with the modified structure for the negative electrode includes one or a combination of several of the following processes: mechanical rolling, lithium injection melting, electrochemical deposition, electrospinning, and blade coating.

9. The lithium metal anode according to claim 8, characterized in that, The pressure of the mechanical roller is 8-12 MPa.

10. A lithium metal battery, characterized in that, Includes the negative electrode modified structure as described in any one of claims 1-7.

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