Metal lithium negative electrode protective layer, preparation method thereof, negative electrode sheet and lithium battery
By using an integrated single-layer lithium metal anode protective layer, combined with chitosan coating and nano-metal particle design, the problems of interface instability and uncontrolled deposition morphology of lithium metal anodes are solved, achieving simple and efficient lithium deposition and long-term battery stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- MONTA VISTA ENERGY TECH CORP (ANHUI)
- Filing Date
- 2026-06-22
- Publication Date
- 2026-07-21
AI Technical Summary
Lithium metal anodes suffer from interfacial instability and uncontrolled deposition morphology. Existing technical solutions are complex and difficult to scale up. Multilayer structures exhibit poor interfacial compatibility during long-term cycling, making it difficult to simultaneously address interfacial stability and deposition uniformity.
Employing an integrated single-layer structure, a conductive network is formed by combining carbon materials modified with metal nanoparticles, thickeners, binders, and a 3D polyurethane framework, with chitosan coating and calcination. The nano-metal particles are uniformly loaded, and the 3D polyurethane framework provides mechanical strength and elasticity, achieving lithiophilicity and high ionic conductivity.
It simplifies the preparation process, reduces costs, improves the uniformity and interface stability of lithium deposition, enhances the cycle stability and safety of the battery, and avoids dendrite growth and short circuit risks.
Smart Images
Figure CN122436439A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery technology, and in particular to a metallic lithium anode protective layer and its preparation method, as well as an anode sheet and a lithium battery. Background Technology
[0002] Lithium-ion batteries play an indispensable role in the global energy electrochemical transition. However, the gravimetric energy density of graphite-based intercalation chemistry systems has approached 350 Wh kg. -1 The theoretical limit of lithium metal anodes is insufficient to meet the urgent needs of next-generation high-energy-density energy storage devices. Among numerous candidate anode materials, lithium metal anodes stand out due to their extremely high specific capacity (3860 mAh g / g). -1 Low density (0.53 g cm⁻¹) -3 Lithium metal stands out due to its low electrochemical potential (-3.04 V) compared to the standard hydrogen electrode. However, the inherent high reactivity and uncontrollable interfacial behavior of lithium metal result in extremely short battery cycle life, severely hindering its practical application. Specifically, lithium metal anodes face two major technical bottlenecks: 1) Interfacial instability: Continuous side reactions between lithium metal and the electrolyte lead to rapid electrolyte consumption and the formation of an unstable, increasingly thickened solid electrolyte interfacial film. This, coupled with the continuous accumulation of dead lithium, ultimately causes a surge in battery impedance and a sharp drop in capacity. 2) Uncontrolled deposition morphology: During dynamic deposition, due to uneven distribution of the interfacial electric field and ion concentration field, lithium tends to grow in non-uniform morphologies such as dendrites or moss. This not only causes significant volume changes and damages the electrode structure but can also lead to dendrites piercing the separator, causing internal short circuits and posing serious safety hazards.
[0003] To address these challenges, researchers have proposed strategies for constructing artificial protective layers to achieve uniform lithium deposition / stripping. However, existing technologies all have their limitations: For interfacial instability, existing technologies propose achieving both mechanical strength and interfacial stability through multi-component and in-situ reactions. However, the fabrication process involves complex electrospinning and subsequent treatments, posing significant challenges in terms of efficiency, cost control, and consistency for large-scale production. Furthermore, the interfacial bonding strength and chemical stability of this complex multilayer structure during long-term cycling remain to be verified. For the non-uniformity of the dynamic lithium deposition process, existing technologies design organic artificial bilayer protective layers, providing mechanical strength / ionic conductivity and flexibility / lithiophilicity, respectively. This functional layering design aims to synergistically solve multiple problems, including the uniformity of lithium deposition. However, its complex multilayer structure increases the steps and difficulty of the fabrication process, potentially leading to high production costs and reduced yield. More importantly, the long-term physical and chemical compatibility between layers is a severe test; the failure of any layer can cause the entire protective function to collapse.
[0004] Therefore, designing a negative electrode structure that is structurally stable, has good interfacial compatibility, and can be prepared by a simple and efficient process, so as to simultaneously achieve precise control of lithium deposition morphology and effective suppression of interfacial side reactions, is a technical challenge that must be overcome to promote the industrialization of lithium metal batteries from the laboratory. Summary of the Invention
[0005] This application provides a lithium metal anode protective layer and its preparation method, as well as an anode sheet and a lithium battery, to solve the problems of interface instability and uncontrolled deposition morphology in the prior art of lithium metal anodes.
[0006] In a first aspect, the present invention discloses a lithium metal anode protective layer, comprising a carbon material modified with metal nanoparticles, a thickener, a binder, and a 3D polyurethane skeleton. The raw materials for metal nanoparticle-modified carbon materials include carbon materials and metal salts in a mass ratio of (6-10):(3-6); The carbon material is coated with chitosan.
[0007] Currently, the technical solutions for artificial protective layers generally suffer from two major shortcomings. First, they are complex in structure, relying on multi-layer and heterogeneous designs, which leads to complicated preparation processes, high costs, and difficulty in scaling up, and also introduces the risk of interlayer compatibility failure. Second, they are single in function, making it difficult to simultaneously solve the core problems of interface stability and uniform deposition in long-term cycling.
[0008] By adopting the above technical solutions, this invention proposes an integrated, single-layer lithium metal anode. This design abandons complex multilayer architectures, achieving a synergistic improvement in lithiophilicity, high ionic conductivity, and mechanical strength within a simple structure by uniformly incorporating specific functional nanomaterials within or on the surface of lithium metal. Simultaneously, 3D polyurethane (TPU) is used to release the stress accumulated inside the electrode during cycling, and the abundant pore structure of TPU further provides sufficient space for lithium metal under high-cycling conditions, enhancing the mechanical and dimensional stability to the liquid electrolyte.
[0009] Specifically, carbon materials can react with Li to form LiC6. LiC6 exhibits excellent lithiophilic properties, reducing the overpotential for lithium nucleation and promoting uniform lithium deposition. Furthermore, when LiC6 is introduced at the electrode-electrolyte interface, it acts as a buffer layer, improving the contact between the electrode and electrolyte and thus reducing interfacial impedance. Chitosan, rich in amino and hydroxyl groups, can achieve uniform coating of carbon materials through hydrogen bonding. Simultaneously, under alkaline conditions, it coordinates with metal ions, providing anchoring sites for the uniform loading of subsequent nano-metal particles. The nano-metal particles themselves possess excellent lithiophilic properties, reducing the overpotential for Li nucleation and promoting uniform lithium deposition. +The deposition overpotential can also be combined with lithium-ion migration to accelerate the rapid lateral diffusion of lithium ions, thereby regulating the lithium plating / stripping behavior to achieve uniform and dense lithium deposition. 3D polyurethane (TPU) possesses a 3D framework, low density, and high elasticity. Its excellent flexibility releases the stress accumulated inside the electrode during cycling. Simultaneously, TPU's rich porous structure, ordered nanochannels, abundant lithiophilic sites, and good mechanical strength are used as a functional interface layer, adapting to the volume changes of lithium metal during repeated plating / stripping processes, thus enabling a lithium-dendrite-free state.
[0010] Preferably, the mass ratio of carbon material to chitosan solution is (1-3):(10-30).
[0011] Preferably, the carbon material includes one or more of graphite, hard carbon, carbon nanotubes, graphene, carbon fiber and carbon black. Preferably, the metal salt includes one of AgNO3 and AlCl3.
[0012] Preferably, the thickener includes one or a combination of several of hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), polyacrylic acid / acrylonitrile copolymer, sodium polyacrylate, and carboxymethyl cellulose.
[0013] Preferably, the binder includes styrene-butadiene rubber, polyvinylidene fluoride (PVDF), and PVDF-HFP copolymer.
[0014] Secondly, the present invention also discloses a method for preparing a negative electrode protective layer, comprising the following steps: S1. The carbon material is placed in an acetic acid solution containing chitosan and ultrasonically treated at room temperature. Then, ammonia is added for solidification to obtain solution 1. Solution 1 is filtered, washed and dried to obtain solid 1. S2. Solid 1 is added to deionized water and ultrasonically treated. Metal salt is added to react. After filtration and washing, solid 2 is obtained. S3. Calcine solid 2 under an inert gas to obtain solid 3; S4. Mix solid 3, thickener, binder and deionized water to obtain a slurry, then place 3D polyurethane in the slurry and dry to obtain a negative electrode protective layer.
[0015] Preferably, in step S1, the concentration of the acetic acid solution of chitosan is 0.5% to 2%.
[0016] Preferably, in step S1, the ultrasonic treatment time is 1 to 3 hours.
[0017] Preferably, in step S1, the mass of ammonia water is equal to 40% to 60% of the mass of the original solution.
[0018] Preferably, in step S2, the pH range of the reaction is 8 to 10, the reaction temperature is 85 to 95°C, and the reaction time is 1 to 3 hours.
[0019] Preferably, in step S3, the calcination temperature is 400–600°C, and the calcination holding time is 1–3 hours.
[0020] Preferably, in step S3, the inert gas includes N2 and argon.
[0021] Preferably, in step S4, the solid content of the slurry is 30% to 40%.
[0022] Preferably, in step S4, the thickness of the protective layer is 6–9 μm.
[0023] Preferably, in step S4, the ratio of solid 3, thickener, binder and deionized water is 1:(0.2-0.5):(0.1-0.3):(2-3).
[0024] Thirdly, the present invention also discloses a negative electrode sheet, including a negative electrode protective layer.
[0025] Preferably, the negative electrode sheet is formed by mechanically rolling the negative electrode protective layer and the lithium sheet.
[0026] Preferably, the roller spacing is 8 to 15 μm.
[0027] Fourthly, the present invention also discloses a lithium battery, including a negative electrode protective layer or a negative electrode sheet.
[0028] The beneficial effects of this invention are: This invention solves the problems of unstable lithium deposition and complex processes and poor interfacial compatibility of multilayer protective layers in existing technologies through an integrated single-layer structure design. Specifically, the chitosan-coated carbon material can coordinate with metal ions under alkaline conditions, providing anchoring points for the uniform loading of subsequent nano-metal particles. After calcination, the chitosan carbonizes to form a conductive network, and the metal ions are reduced in situ to nano-metal particles, which are firmly attached to the surface of the carbon material, forming a composite structure with excellent lithiophilic properties. In this structure, the nano-metal particles can reduce the lithium nucleation overpotential and induce uniform lithium ion deposition; the LiC6 generated by the reaction of carbon material and lithium metal has high ionic conductivity and lithiophilic properties, which can promote the rapid transport of lithium ions at the interface and reduce the interfacial impedance; the 3D polyurethane skeleton has low density, high elasticity and abundant pore structure, which on the one hand provides three-dimensional space for lithium metal deposition, effectively alleviates the volume expansion during cycling, and on the other hand releases the stress accumulated inside the electrode through its elastic deformation, preventing the protective layer from cracking and failing. Compared with existing technologies, this invention abandons the complex multilayer heterogeneous structure and achieves lithiophilicity and high ionic conductivity through a simple process. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the surface of the lithium metal composite negative electrode obtained in Example 3 of the present invention; Figure 2 This is a cross-sectional schematic diagram of the lithium metal composite negative electrode obtained in Example 3 of the present invention; Figure 3 The battery internal resistance and t(Li) of Examples 1-6 and Comparative Examples 1-3 of the present invention are shown. + Comparison chart; Figure 4 The graph shows a comparison of the battery cycle performance of Examples 1-6 and Comparative Examples 1-3 of the present invention. Detailed Implementation
[0030] 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.
[0031] A lithium metal anode protective layer comprises a carbon material modified with metal nanoparticles, a thickener, a binder, and a 3D polyurethane framework. The raw materials for metal nanoparticle-modified carbon materials include carbon materials and metal salts in a mass ratio of (6-10):(3-6); The carbon material is coated with chitosan.
[0032] Currently, the technical solutions for artificial protective layers generally suffer from two major shortcomings. First, they are complex in structure, relying on multi-layer and heterogeneous designs, which leads to complicated preparation processes, high costs, and difficulty in scaling up, and also introduces the risk of interlayer compatibility failure. Second, they are single in function, making it difficult to simultaneously solve the core problems of interface stability and uniform deposition in long-term cycling.
[0033] By adopting the above technical solutions, this invention proposes an integrated, single-layer lithium metal anode. This design abandons complex multilayer architectures, achieving a synergistic improvement in lithiophilicity, high ionic conductivity, and mechanical strength within a simple structure by uniformly incorporating specific functional nanomaterials within or on the surface of lithium metal. Simultaneously, 3D polyurethane (TPU) is used to release the stress accumulated inside the electrode during cycling, and the abundant pore structure of TPU further provides sufficient space for lithium metal under high-cycling conditions, enhancing the mechanical and dimensional stability to the liquid electrolyte.
[0034] Specifically, carbon materials can react with Li to form LiC6. LiC6 exhibits excellent lithiophilic properties, reducing the overpotential for lithium nucleation and promoting uniform lithium deposition. Furthermore, when LiC6 is introduced at the electrode-electrolyte interface, it acts as a buffer layer, improving the contact between the electrode and electrolyte and thus reducing interfacial impedance. Chitosan, rich in amino and hydroxyl groups, can achieve uniform coating of carbon materials through hydrogen bonding. Simultaneously, under alkaline conditions, it coordinates with metal ions, providing anchoring sites for the uniform loading of subsequent nano-metal particles. The nano-metal particles themselves possess excellent lithiophilic properties, reducing the overpotential for Li nucleation and promoting uniform lithium deposition. + The deposition overpotential can also be combined with lithium-ion migration to accelerate the rapid lateral diffusion of lithium ions, thereby regulating the lithium plating / stripping behavior to achieve uniform and dense lithium deposition. 3D polyurethane possesses a 3D framework, low density, and high elasticity. Its excellent flexibility releases the stress accumulated inside the electrode during cycling. Meanwhile, the CPU's rich porous structure, ordered nanochannels, abundant lithiophilic sites, and good mechanical strength are used as a functional interface layer, which can adapt to the volume changes of lithium metal during repeated plating / stripping processes, thus achieving a lithium-dendritic-free state.
[0035] In some embodiments, the mass ratio of carbon material to chitosan solution is (1-3):(10-30).
[0036] By adopting the above technical solutions, the above mass ratio can ensure that chitosan forms a uniform and complete coating layer on the surface of carbon materials. When the chitosan content is too low, it is impossible to completely coat the carbon materials, resulting in uneven loading of subsequent metal nanoparticles. When the chitosan content is too high, the coating layer is too thick, which increases the ion transport resistance and reduces the ionic conductivity of the protective layer.
[0037] In some embodiments, the carbon material includes one or more of graphite, hard carbon, carbon nanotubes, graphene, carbon fiber, and carbon black.
[0038] By employing the above technical solutions, graphite, with its layered structure and excellent conductivity, facilitates the insertion and extraction of lithium ions; hard carbon possesses more defect sites and porous structures, providing additional active sites for lithium storage; carbon nanotubes exhibit excellent one-dimensional conductive networks and mechanical strength, enabling the construction of efficient electron transport channels; graphene boasts ultra-high specific surface area and electron mobility, significantly reducing interfacial impedance; carbon fibers offer good flexibility and structural stability, adapting to volume changes; and carbon black offers advantages such as low cost and good dispersibility. All of these carbon materials can react with metallic lithium to form lithiophilic compounds such as LiC6, reducing the lithium nucleation overpotential and promoting uniform lithium deposition. Combining two or more carbon materials can achieve a synergistic effect, addressing multiple performance requirements including conductivity, mechanical strength, and lithiophilicity.
[0039] In some embodiments, the metal salt includes one of AgNO3 and AlCl3.
[0040] By employing the above technical solutions, metal salts coordinate with the amino groups on chitosan chains under alkaline conditions, and after calcination, are reduced to metal nanoparticles and uniformly dispersed on the surface of carbon materials. Ag has extremely high lithiophilicity and electronic conductivity, which can significantly reduce the lithium deposition overpotential; Al can form alloys with lithium, providing abundant nucleation sites. The introduction of these metal nanoparticles can not only regulate lithium deposition behavior through lithiophilicity, but also cooperate with lithium ion migration, accelerate the rapid lateral diffusion of lithium ions, effectively suppress the longitudinal growth of dendrites, and achieve a uniform and dense lithium deposition morphology.
[0041] In some embodiments, the thickener includes one or a combination of several of hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), polyacrylic acid / acrylonitrile copolymer, sodium polyacrylate, and carboxymethyl cellulose.
[0042] By adopting the above technical solutions, the introduction of thickeners can effectively regulate the rheological properties of the slurry, ensuring that the solid components are uniformly dispersed in the slurry and remain in a stable suspension state, preventing sedimentation and stratification; at the same time, it facilitates the impregnation and coating of the 3D polyurethane skeleton, forming a protective layer with a rich porosity structure after drying, which is beneficial for electrolyte wetting and rapid lithium ion transport.
[0043] In some embodiments, the binder includes styrene-butadiene rubber, polyvinylidene fluoride (PVDF), and PVDF-HFP copolymer.
[0044] By adopting the above technical solutions, the choice of adhesive ensures a strong bond between the components of the protective layer and between the protective layer and the 3D polyurethane skeleton; styrene-butadiene rubber has excellent elasticity, flexibility and bonding strength, which can effectively buffer the volume stress during the cycling process, and has good compatibility with the electrolyte.
[0045] A method for preparing a negative electrode protective layer includes the following steps: S1. The carbon material is placed in an acetic acid solution containing chitosan and ultrasonically treated at room temperature. Then, ammonia is added for solidification to obtain solution 1. Solution 1 is filtered, washed and dried to obtain solid 1. S2. Solid 1 is added to deionized water and ultrasonically treated. Metal salt is added to react. After filtration and washing, solid 2 is obtained. S3. Calcine solid 2 under an inert gas to obtain solid 3; S4. Mix solid 3, thickener, binder and deionized water to obtain a slurry, then place 3D polyurethane in the slurry and dry to obtain a negative electrode protective layer.
[0046] By adopting the above technical solutions, ultrasonic-assisted chitosan coating in S1 ensures a uniform coating layer; ammonia curing causes chitosan cross-linking and deposition, forming a stable coating layer; ultrasonic dispersion in S2, along with controlled pH and temperature reactions, allows metal ions to be fully adsorbed onto the chitosan coating layer and reduced in situ, achieving uniform loading of nanoparticles; calcination in S3 not only carbonizes the chitosan to form a conductive network but also reduces metal salts to nano-metal particles, while enhancing their bonding force with carbon materials. In S4, the composite slurry is impregnated in a 3D polyurethane framework, and an integrated protective layer can be obtained through simple drying, eliminating the need for complex coatings or multi-layer composites, significantly simplifying the process, reducing production costs, and avoiding interlayer interface problems.
[0047] In some embodiments, in step S1, the concentration of the acetic acid solution of chitosan is 0.5% to 2%.
[0048] In some embodiments, the ultrasonic treatment time in step S1 is 1 to 3 hours.
[0049] In some embodiments, in step S1, the mass of ammonia is 40% to 60% of the mass of the chitosan acetic acid solution.
[0050] By adopting the above technical solutions, the concentration of the acetic acid solution of chitosan is controlled within the range of 0.5% to 2%, which ensures that the chitosan molecules are fully dissolved and maintain good fluidity, facilitating uniform mixing with carbon materials. The ultrasonic treatment time is controlled within the range of 1 to 3 hours, which enables the carbon materials to be fully dispersed and uniformly coated in the chitosan solution, allowing the chitosan molecules to be uniformly adsorbed on the surface of the carbon materials, forming a stable coating structure, while maintaining the intrinsic structure and electrochemical properties of the carbon materials.
[0051] In some embodiments, in step S2, the pH range of the reaction is 8 to 10, the reaction temperature is 85 to 95°C, and the reaction time is 1 to 3 hours.
[0052] By adopting the above technical solutions, the weakly alkaline environment of pH 8-10 causes the amino groups on the chitosan molecular chain to be deprotonated and transformed into a free state. The lone pair electrons can form stable coordination bonds with metal ions, achieving uniform anchoring of metal ions. If the pH is too low, the coordination is incomplete, and if the pH is too high, metal ions are prone to form hydroxide precipitates.
[0053] In some embodiments, in step S3, the calcination temperature is 400–600°C, and the calcination holding time is 1–3 h; the inert gas includes N2 and argon.
[0054] By employing the above technical solutions, the calcination process transforms chitosan into a nitrogen-doped carbon layer, further enhancing the material's lithiophilicity and conductivity. Simultaneously, dispersed metal nanoparticles are obtained, significantly improving the electrochemical performance of the protective layer. Below 400℃, metal ion reduction is incomplete, and the degree of chitosan carbonization is low, resulting in poor conductivity. Above 600℃, metal nanoparticles are prone to Ostwald ripening, leading to growth and aggregation, and the carbon material structure may become excessively graphitized, causing a decrease in lithiophilicity.
[0055] In some embodiments, in step S4, the slurry solid content is 30% to 40%; the thickness of the protective layer is 6 to 9 μm.
[0056] By adopting the above technical solutions, the solid content of the slurry is controlled within the range of 30% to 40%, ensuring that the slurry has suitable viscosity and fluidity. This allows for sufficient impregnation of the porous structure of the 3D polyurethane skeleton without excessive drying shrinkage due to too low a solid content or incomplete impregnation due to too high a solid content. The slurry with a solid content of 30% to 40% fills the 3D polyurethane skeleton uniformly, forming a dense and porous protective layer structure after drying. The thickness of the protective layer is controlled within the range of 6 to 9 μm, which is a key parameter that has been optimized: if the thickness is too thin, the mechanical strength is insufficient, making it difficult to effectively suppress dendrite penetration, and the buffering capacity for volume changes is limited; if the thickness is too thick, the ion transport path lengthens, the interfacial impedance increases significantly, and the energy density of the battery decreases.
[0057] In some embodiments, in step S4, the ratio of solid 3, thickener, binder and deionized water is 1:(0.2-0.5):(0.1-0.3):(2-3).
[0058] By adopting the above technical solutions, the formulation system achieves synergistic optimization of functional materials, processing performance and electrochemical performance, so that the prepared protective layer has a uniform composition, suitable porous structure and good mechanical strength.
[0059] 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.
[0060] Example Example 1: A negative electrode sheet was prepared by the following method: S1. Place 10g of graphite into 100mL of acetic acid solution containing 1% chitosan, sonicate at room temperature for 1h, then add 42.5g of ammonia water for curing to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 3.2g of AgNO3 and stir for 1h at pH=8 and temperature 90℃. Filter and wash to obtain solid 2. S3. Place solid 2 in a tube furnace and keep it at 400°C for 2 hours under N2 protection to obtain solid 3; S4. Mix 5.01g solid 3, 1.12g carboxymethyl cellulose (CMC), 0.93g styrene-butadiene rubber (SBR), and 10.34g deionized water to obtain a slurry with a solid content of 30%. Then, place 1.1g 3D polyurethane in the slurry for 30min and dry at 60℃ to obtain a 6.2μm protective layer for the negative electrode. S5. The negative electrode protective layer is applied to the surface of the lithium sheet by mechanical rolling with a rolling gap of 9.3μm to obtain the negative electrode sheet.
[0061] Example 2: A negative electrode sheet was prepared by the following method: S1. Place 10g of hard carbon into 100mL of acetic acid solution containing 2% chitosan, sonicate at room temperature for 1h, then add 43.6g of ammonia water for solidification to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 3.1g of AlCl3 and stir for 1h at pH=9 and temperature 90℃. Filter and wash to obtain solid 2. S3. Place solid 2 in a tube furnace and keep it at 600°C for 2 hours under N2 protection to obtain solid 3; S4. Mix 5.11g of solid 3, 1.21g of carboxymethyl cellulose (CMC), 0.94g of styrene-butadiene rubber (SBR), and 10.12g of deionized water to obtain a slurry with a solid content of 35%. Then, place 1.03g of 3D polyurethane in the slurry for 30min and dry it at 60℃ to obtain the negative electrode protective layer. S5. The negative electrode protective layer is applied to the surface of the lithium sheet by mechanical rolling with a rolling gap of 8.6μm to obtain the negative electrode sheet.
[0062] Example 3: A negative electrode sheet was prepared by the following method: S1. Place 10g of carbon nanotubes into 100mL of acetic acid solution containing 1% chitosan, sonicate at room temperature for 2h, then add 42.8g of ammonia water for solidification to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 3.3g of AgNO3 and stir for 1h at pH=9 and temperature 90℃. Filter and wash to obtain solid 2. S3. Place solid 2 in a tube furnace and keep it at 600°C for 2 hours under N2 protection to obtain solid 3; S4. Mix 5.31g solid 3, 1.35g carboxymethyl cellulose (CMC), 0.95g styrene-butadiene rubber (SBR), and 10.31g deionized water to obtain a slurry with a solid content of 35%. Then, place 0.98g 3D polyurethane in the slurry for 30 minutes and dry it at 60°C to obtain the negative electrode protective layer. S5. The negative electrode protective layer is applied to the surface of the lithium sheet by mechanical rolling, with a rolling gap of 8.5μm to obtain the negative electrode sheet.
[0063] Example 4: A negative electrode sheet was prepared by the following method: S1. Place 10g of graphene into 100mL of acetic acid solution containing 0.5% chitosan, sonicate at room temperature for 1h, then add 41.2g of ammonia water for curing to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 4g of AgNO3 and stir at pH=8 and temperature 85℃ for 1h. Filter and wash to obtain solid 2. S3. Place solid 2 in a tube furnace and keep it at 400°C for 1 hour under N2 protection to obtain solid 3; S4. Mix 5.32g solid 3, 1.31g carboxymethyl cellulose (CMC), 0.96g styrene-butadiene rubber (SBR), and 10.25g deionized water to obtain a slurry with a solid content of 30%. Then, place 1.02g 3D polyurethane in the slurry for 30 minutes and dry it at 60°C to obtain the negative electrode protective layer. S5. The negative electrode protective layer is applied to the surface of the lithium sheet by mechanical rolling with a rolling gap of 7.01 μm to obtain the negative electrode sheet.
[0064] Example 5: A negative electrode sheet was prepared by the following method: S1. Place 10g of graphene into 100mL of acetic acid solution containing 1% chitosan, sonicate at room temperature for 1h, then add 41.3g of ammonia water for curing to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 5g of AgNO3 and stir for 1h at pH=9 and temperature 90℃. Filter and wash to obtain solid 2. S3. Place solid 2 in a tube furnace and keep it at 500°C for 2 hours under N2 protection to obtain solid 3; S4. Mix 5.24g solid 3, 1.28g carboxymethyl cellulose (CMC), 1.02g styrene-butadiene rubber (SBR), and 10.23g deionized water to obtain a slurry with a solid content of 35%. Then, place 1.01g 3D polyurethane in the slurry for 30 minutes and dry it at 60°C to obtain the negative electrode protective layer. S5. The negative electrode protective layer is applied to the surface of the lithium sheet by mechanical rolling with a rolling gap of 8.34μm to obtain the negative electrode sheet.
[0065] Example 6: A negative electrode sheet was prepared by the following method: S1. Place 10g of graphene into 100mL of acetic acid solution containing 2% chitosan, sonicate at room temperature for 1h, then add 40.25g of ammonia water for curing to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 6g of AgNO3 and stir at pH=10 and temperature 95℃ for 1h. Filter and wash to obtain solid 2. S3. Place solid 2 in a tube furnace and keep it at 600°C for 3 hours under N2 protection to obtain solid 3. S4. Mix 5.31g solid 3, 1.26g carboxymethyl cellulose (CMC), 1.01g styrene-butadiene rubber (SBR), and 7.32g deionized water to obtain a slurry with a solid content of 40%. Then, place 0.98g 3D polyurethane in the slurry for 30 minutes and dry it at 60°C to obtain the negative electrode protective layer. S5. The negative electrode protective layer is applied to the surface of the lithium sheet by mechanical rolling, with a rolling gap of 8.11 μm, to obtain the negative electrode sheet.
[0066] Comparative Example Comparative Example 1: A negative electrode, which is an unmodified lithium sheet.
[0067] Comparative Example 2, a negative electrode sheet, was prepared by the following method: S1. Place 10g of graphite into 100mL of acetic acid solution containing 1% chitosan, sonicate at room temperature for 1h, then add 49.51g of ammonia water for solidification to obtain solution 1. Filter, wash and freeze dry solution 1 for 10h to obtain solid 1. S2. Add 10g of solid 1 to 100mL of deionized water and sonicate for 2h. Add 0.5g of AgNO3 and stir for 1h at pH=8 and temperature 90℃. Filter and wash to obtain solid 2. S3. Mix 4.1g of solid 2, 1.12g of carboxymethyl cellulose (CMC), 0.99g of styrene-butadiene rubber (SBR), and 11.3g of deionized water to obtain a slurry with a solid content of 30%. Then, coat the slurry onto copper foil, dry it at 60°C, and modify it onto the surface of lithium sheet by mechanical rolling with a rolling gap of 8.2μm to obtain the negative electrode sheet.
[0068] Comparative Example 3: A negative electrode sheet was prepared by the following method: 3D polyurethane was applied to the surface of a lithium sheet by mechanical rolling with a rolling gap of 7.1 μm to obtain a negative electrode sheet.
[0069] Performance testing Battery fabrication: 1) Electrode preparation: ① Slurry preparation: NCM + conductive agent + binder (8:1:1) + solvent NMP, stir into a uniform slurry. ② Coating: Coat the slurry onto the current collector (positive electrode uses aluminum foil + negative electrode prepared in this application). ③ Drying: First, dry with forced air, then thoroughly remove moisture in a vacuum oven. ④ Cutting: After rolling and compacting, punch into small round pieces with a diameter of 14mm, weigh and set aside. 2) Battery assembly (argon glove box throughout): Stack in the following order: negative electrode shell → spring sheet → gasket → lithium sheet → electrolyte → separator → electrolyte → positive electrode (coating side down) → positive electrode shell. 3) Sealing: Seal under pressure using a sealing machine. 4) Static testing.
[0070] 1. Resistance Test: Create a new AC impedance (EIS) test program in the electrochemical workstation software. Select the open-circuit potential, meaning the test should be performed under the natural state of the battery with no applied current. Frequency range: set to high frequency up to 100 kHz and low frequency up to 0.01 Hz. AC amplitude: set to 5 mV. After setting the parameters, click Start to complete the test.
[0071] 2. Lithium-ion transference number: Assemble a symmetrical Li | electrolyte | Li battery in a glove box. Two lithium metal sheets serve as electrodes, with an electrolyte-wetted separator in between. Perform the test procedure. Connect the assembled symmetrical battery to the electrochemical workstation. Measure the initial impedance: ① First, perform an AC impedance test on the battery to obtain the initial interfacial impedance. The parameters are typically set to a frequency range of 100 kHz - 0.1 Hz and an amplitude of 10 mV.
[0072] ② After prolonged polarization, apply a very small constant voltage (10 mV) to the battery and perform a chronoamperometry test. ③ Measure the steady-state impedance: Immediately after polarization, measure the AC impedance again to obtain the steady-state interface impedance.
[0073] ④ Substitute into the formula to calculate.
[0074] 3. Cyclic Capability Testing: Constant current-constant voltage charging (CC-CV) and constant current discharging (DC) modes are used. ① Allow the battery to rest for 5-10 minutes to stabilize the voltage and state. ② Charging: Charge the battery with a constant current of 0.33C until the voltage reaches 4.2V. Switch to constant voltage charging, maintaining the voltage at the previous upper limit. The current will gradually decrease until it reaches 0.05C, at which point charging stops. Rest: After charging, allow the battery to rest for another 5-10 minutes to allow the voltage to return to a stable state. ③ Discharging: Discharge the battery with a high current of 3C using a constant current until the voltage drops to 3.3V. ④ Cycling: Set the cycle count to 500 times.
[0075] Table 1 Performance test results
[0076] A schematic diagram of the surface of the lithium metal composite anode obtained in Example 3 is shown below. Figure 1 As shown, the cross-sectional view is as follows Figure 2 As shown. The battery internal resistance and t of Examples 1-6 and Comparative Examples 1-3 of the present invention are shown. (Li + ) Please refer to the comparison chart. Figure 3 As shown in the diagram, please refer to the battery cycle performance comparison charts of Examples 1-6 and Comparative Examples 1-3 of the present invention. Figure 4 As shown.
[0077] According to the tests in Table 1, comparing the experimental results of the examples and the comparative examples, it can be seen that Comparative Example 1, being an unmodified lithium sheet, has the lowest resistance of 509 mΩ, but t （Li + ） Only 0.35, with only 86 cycles; comparative example 2, without a 3D polyurethane skeleton, had 105 cycles and t （Li + ） 0.43, Comparative Example 3 is 3D polyurethane only, with 131 cycles and t （Li + ）The cycling performance of all three methods was significantly worse than that of the example, with a value of 0.39, indicating that the synergistic effect of chitosan-coated carbon material supporting metal nanoparticles and the 3D polyurethane framework is the key to achieving excellent cycling stability. In summary, the integrated single-layer structure of this invention utilizes the synergistic effect of lithium deposition induced by lithiophilic metal nanoparticles, the formation of LiC6 by carbon materials to promote rapid lithium-ion transport, and the buffering effect of the 3D polyurethane framework to buffer volume expansion and release stress. These three elements work together in a single protective layer, significantly improving lithium-ion transport number and cycling stability while sacrificing some electrical resistance. This solves the problems of complex processes and poor interfacial compatibility in existing multilayer structures.
[0078] 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 protective layer for a lithium metal anode, characterized in that, The negative electrode protective layer comprises carbon material modified with metal nanoparticles, thickener, binder and 3D polyurethane skeleton; The raw materials for the metal nanoparticle-modified carbon material include carbon material and metal salt in a mass ratio of (6-10):(3-6); The carbon material is coated with chitosan.
2. The negative electrode protective layer according to claim 1, characterized in that, The mass ratio of the carbon material to the chitosan solution is (1-3):(10-30).
3. The negative electrode protective layer according to claim 1, characterized in that, The carbon material includes one or more of graphite, hard carbon, carbon nanotubes, graphene, carbon fiber, and carbon black.
4. The negative electrode protective layer according to claim 1, characterized in that, The metal salt includes one of AgNO3 and AlCl3.
5. A method for preparing a lithium metal anode protective layer according to any one of claims 1-4, characterized in that, Includes the following steps: S1. The carbon material is placed in an acetic acid solution containing chitosan and ultrasonically treated at room temperature. Then, ammonia is added for solidification to obtain solution 1. Solution 1 is filtered, washed and dried to obtain solid 1. S2. Solid 1 is added to deionized water and ultrasonically treated. Metal salt is added to react. After filtration and washing, solid 2 is obtained. S3. Calcine solid 2 under an inert gas to obtain solid 3; S4. Mix solid 3, thickener, binder and deionized water to obtain a slurry, then place 3D polyurethane in the slurry and dry to obtain a negative electrode protective layer.
6. The method according to claim 5, characterized in that, In step S2, the pH range of the reaction is 8 to 10, the reaction temperature is 85 to 95°C, and the reaction time is 1 to 3 hours.
7. The method according to claim 5, characterized in that, In step S3, the calcination temperature is 400–600°C, and the calcination holding time is 1–3 hours.
8. The method according to claim 5, characterized in that, In step S4, the solid content of the slurry is 30% to 40%; the thickness of the negative electrode protective layer is 6 to 9 μm.
9. A negative electrode sheet, characterized in that, Includes the negative electrode protective layer as described in any one of claims 1-4.
10. A lithium battery, characterized in that, It includes the lithium metal anode protective layer as described in any one of claims 1-4, or the anode sheet as described in claim 9.