A modification method and application of a lithium metal negative electrode

Abstract

The application discloses a modification method and application of a lithium metal negative electrode, and relates to the technical field of batteries. The method comprises the following steps: providing a substrate containing a lithium metal layer; preparing a spraying slurry; atomizing and depositing the spraying slurry on the surface of the lithium metal layer by using an electrostatic spraying process to form a spraying coating; and performing post-treatment on the lithium metal layer substrate after spraying. The modification method provided by the application can solve the problems of poor uniformity of a coating, incomplete dendrite inhibition and low process compatibility in the existing interface modification technology of a lithium metal negative electrode.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a method for modifying lithium metal anodes and their applications. Background Technology

[0002] Lithium metal batteries are rechargeable batteries that rely on the migration of lithium ions between the positive and negative electrodes to achieve charging and discharging. Due to their advantages such as high energy density, high operating voltage, and light weight, they are widely used in mobile phones, computers, energy storage, and electric vehicles. With the development of the new energy industry, the demand for high energy density in power batteries is becoming increasingly urgent, driving the technological upgrade of lithium metal battery anode materials.

[0003] Currently, most commercially available lithium metal batteries use graphite-based anodes, which have a theoretical specific capacity of only 372 mAh / g, becoming a bottleneck for improving battery energy density. Lithium metal, with its ultra-high theoretical specific capacity of 3860 mAh / g and extremely low electrode potential, is widely recognized as the ultimate anode material for next-generation lithium metal batteries. However, the commercial application of lithium metal anodes still faces three major challenges: dendrite growth, interfacial side reactions, and significant volume changes, which can easily lead to problems such as battery short circuits, performance degradation, and poor cycle stability.

[0004] To address the aforementioned issues, interface engineering modification is one of the most direct and effective technical approaches. Among these, artificial SEI layer technology, by constructing a protective layer on the lithium metal surface, can effectively suppress dendrite growth and interfacial side reactions. However, existing preparation technologies have many drawbacks. The thickness of the liquid lithium alloy coating formed by physical coating methods is difficult to control and it is prone to peeling off from the substrate. Gas-phase reaction methods produce polluting byproducts and have uneven coating layers with high brittleness. Wet immersion methods suffer from solvent residue and cannot be used for continuous production, all of which are difficult to meet the needs of large-scale production.

[0005] Therefore, developing a lithium metal anode modification method with good coating uniformity, excellent dendrite suppression effect, and adaptability to continuous production has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] This application provides a method and application for modifying lithium metal anodes to solve problems such as poor coating uniformity, incomplete dendrite suppression, and low process compatibility in existing lithium metal anode interface modification technologies.

[0007] In a first aspect, this application provides a method for modifying a lithium metal anode, comprising the following steps: Provide a substrate containing a lithium metal layer; Preparation of spray coating slurry; An electrostatic spraying process is used to atomize and deposit the spraying slurry onto the surface of the lithium metal layer to form a sprayed coating. Post-treatment is performed on the lithium-containing metal layer substrate after spraying.

[0008] In some embodiments, the spray slurry comprises the following components by mass percentage: 70-85 wt% solid electrolyte, 5-15 wt% LiF functional filler, and 8-12 wt% binder, with the balance being dispersion medium and additives.

[0009] In some embodiments, the particle size of the solid electrolyte is 0.1-5 μm.

[0010] In some embodiments, the solid electrolyte includes at least one of lithium lanthanum zirconium oxide series solid electrolyte and lithium silicon phosphate solid electrolyte, wherein the lithium lanthanum zirconium oxide series solid electrolyte includes lithium lanthanum zirconium tantalum oxide solid electrolyte.

[0011] In some embodiments, the adhesive comprises a composite system of polyvinylidene fluoride-hexafluoropropylene copolymer and polyethylene oxide.

[0012] In some embodiments, the adhesive is dissolved in a solvent to form an adhesive solution, the solvent including at least one of N,N-dimethylformamide, acetone, ethyl acetate and dimethyl sulfoxide, and the solid content of the adhesive solution is 12-15 wt%.

[0013] In some embodiments, the dispersion medium includes cyclohexane.

[0014] In some embodiments, the LiF functional filler comprises nanoscale lithium fluoride.

[0015] In some embodiments, the additive includes a rheology modifier, which includes hydroxypropyl methylcellulose.

[0016] In some embodiments, the electric field strength of the electrostatic spraying is 10-80kV.

[0017] In some embodiments, the electrostatic spraying distance is 15-20cm.

[0018] In some embodiments, the electrostatic spraying delivery pressure is 0.4-0.6 MPa.

[0019] In some embodiments, the substrate temperature during electrostatic spraying is 20-80°C.

[0020] In some embodiments, the thickness of the lithium metal layer is 5-30 μm.

[0021] In some embodiments, the thickness of the substrate is 4-12 μm.

[0022] In some embodiments, the thickness of the sprayed coating is 0.3-5 μm.

[0023] In some embodiments, the particle size of the atomized charged particles in the electrostatic spraying is 0.1-5 μm.

[0024] Secondly, this application provides a lithium metal anode, which is prepared using the modification method described in the first aspect.

[0025] Thirdly, this application provides a lithium metal battery, which includes the lithium metal negative electrode described in the second aspect. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A process flow diagram of lithium metal anode modification provided in the embodiments of this application; Figure 2 This is a schematic diagram of the electrostatic spraying modified lithium copper composite strip structure provided in the embodiments of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Currently, graphite-based materials are the primary anode materials for commercially available lithium-ion batteries, with a theoretical specific capacity of only 372 mAh / g, which is a key factor limiting further improvements in battery energy density. To meet the urgent demand for high-energy-density energy storage devices in fields such as electric vehicles and portable electronic devices, developing novel anode materials has become an industry consensus. Lithium metal, with its ultra-high theoretical specific capacity of 3860 mAh / g and the lowest electrode potential of -3.04V vs. SHE, is widely recognized as the ultimate anode material for next-generation lithium-ion batteries. Using lithium metal anodes can significantly improve battery energy density, meeting the application requirements of high-energy-storage scenarios.

[0030] However, the commercial application of lithium metal anodes still faces three major challenges: First, the dendrite problem. During battery cycling, lithium ions are unevenly deposited on the electrode surface to form lithium dendrites, which not only reduces the battery's coulombic efficiency but may also puncture the separator and cause internal short circuits, posing a serious safety hazard. Second, the interfacial side reaction problem. Lithium metal has extremely high reactivity and is prone to irreversible side reactions with the electrolyte, consuming the active materials in the battery and forming an unstable solid electrolyte interphase (SEI) film, leading to battery performance degradation. Third, the volume change problem. The volume change rate of lithium metal during charge and discharge exceeds 300%. The large expansion and contraction can easily cause electrode pulverization and interfacial contact failure, reducing the battery's cycle stability.

[0031] To address the aforementioned issues, current research primarily focuses on three main areas: electrolyte additive optimization, solid-state electrolyte development, and interface engineering modification. Among these, interface engineering modification, which can directly improve the surface state of lithium metal, is considered one of the most direct and effective technical pathways to solve the core problems of lithium metal anodes. In particular, the artificial SEI layer technology, which has emerged in recent years, can effectively suppress dendrite growth and interfacial side reactions by constructing a stable protective coating on the lithium metal surface. However, existing artificial SEI layer preparation technologies generally suffer from complex processes, high costs, and insufficient coating uniformity, making it difficult to meet the practical needs of large-scale production.

[0032] In existing technologies, preparing artificial SEI layers through physical coating is one of the mainstream technical approaches. For example, the lithium metal composite strip preparation technology proposed in the public document CN112447978A involves coating the lithium metal surface with liquid lithium alloy through spraying, brushing, or spraying to form a liquid lithium alloy protective coating, thereby modifying the lithium metal anode. However, this technology has significant drawbacks: first, the thickness of the liquid lithium alloy coating is difficult to control precisely, easily leading to uneven coating; second, the high-temperature characteristics of the liquid alloy easily cause the lithium metal substrate to melt, further exacerbating the uneven coating problem; and third, the thermal expansion coefficients of the lithium alloy and the pure lithium substrate differ significantly, making it easy for microcracks to form during the coating cooling process. During the volume changes of the battery during cyclic charging and discharging, the alloy layer is prone to peeling off from the lithium metal substrate, losing its protective effect.

[0033] Chemical in-situ reaction is another mainstream lithium metal anode interface modification technology, mainly divided into gas-phase reaction and wet immersion methods. Publication CN110846610A proposes a Freon gas-phase reaction technology, which utilizes CF2Cl2 to react with lithium metal to generate a LiF protective layer. This LiF layer possesses high ionic conductivity and low electronic conductivity, promoting uniform lithium-ion deposition. Publication CN117334850A proposes a wet solution immersion technology, in which lithium metal is immersed in a solution containing CuSCF3, forming a Cu / LiF / Li-SR composite protective coating through in-situ reaction. Cu enhances interfacial conductivity, and the Li-SR organic layer strengthens the coating's flexibility. However, this type of in-situ chemical reaction technology still has many shortcomings: chlorine byproducts are generated during the gas phase reaction, which pollutes the environment and requires additional exhaust gas treatment equipment. Insufficient contact between the gas and solid phases leads to a LiF coating thickness deviation of ±30%, and local weak points are prone to preferential dendrite growth. At the same time, the LiF layer is brittle and cannot adapt to the volume changes during lithium metal cycling, making it prone to cracking. Wet immersion technology is prone to solvent residue problems, which leads to a surge in the interface impedance of the lithium metal anode. Moreover, this process cannot be adapted to continuous roll-to-roll production, resulting in low production efficiency and making it difficult to achieve industrial application.

[0034] The applicant discovered that an electrostatic spraying process driven by a high-voltage electrostatic field atomizes a spray slurry composed of a solid electrolyte, LiF functional filler, and composite binder into uniform charged particles, which are then directionally deposited onto the lithium metal surface. This achieves uniform coating with nanoscale precision. Combined with specific substrate pretreatment and post-treatment processes, a multi-layered synergistic artificial SEI protective layer can be constructed. This protective layer can simultaneously meet the requirements of high ionic conductivity, high mechanical strength, and good flexibility, effectively suppressing lithium dendrite growth and interfacial side reactions. Moreover, the entire process is a low-pressure, non-contact processing method, suitable for roll-to-roll continuous production of ultra-thin lithium strips, thus solving many defects of existing technologies.

[0035] In view of this, this application provides a method for modifying lithium metal anodes and its application, in order to solve the problems of poor coating uniformity, incomplete dendrite suppression, and low process compatibility in existing lithium metal anode interface modification technologies.

[0036] In a first aspect, this application provides a method for modifying a lithium metal anode. According to an embodiment of this application, the modification method includes the following steps: Provide a substrate containing a lithium metal layer; Preparation of spray coating slurry; An electrostatic spraying process is used to atomize and deposit the spraying slurry onto the surface of the lithium metal layer to form a sprayed coating. Post-treatment is performed on the lithium-containing metal layer substrate after spraying.

[0037] The lithium metal anode modification method provided in this application achieves uniform preparation of the solid electrolyte protective layer by atomizing and depositing the spray slurry onto the surface of the lithium metal layer using an electrostatic spraying process. This effectively solves the problem of insufficient interface uniformity in traditional wet coating technology. The electrostatic field in the electrostatic spraying process can atomize the slurry into uniform charged particles, achieving uniform deposition at the micron to nanometer scale through charge repulsion. This ensures that the thickness deviation of the sprayed coating is controlled within ±5%, avoiding local current density concentration caused by uneven thickness. Simultaneously, this process employs a non-contact, low-pressure processing method, achieving non-destructive processing of the lithium metal strip, effectively preventing deformation and damage to the lithium metal during processing. Furthermore, this method is compatible with roll-to-roll continuous production processes for lithium metal strips, which is beneficial for improving production efficiency.

[0038] According to an embodiment of this application, see Figure 1 The modification method specifically includes: S100, providing a substrate containing a lithium metal layer.

[0039] In this step, by providing a substrate containing a lithium metal layer, a stable material foundation is laid for subsequent modification treatment.

[0040] In some embodiments of this application, the thickness of the lithium metal layer is 5-30 μm. This thickness range helps ensure that the lithium metal layer has sufficient mechanical stability to withstand the impact of charged particles during subsequent electrostatic spraying without damage.

[0041] In some embodiments of this application, the thickness of the substrate is 4-12 μm. A substrate within this thickness range provides sufficient mechanical strength to support the lithium metal layer and subsequent coatings, and helps prevent deformation and breakage of the lithium layer during electrostatic spraying and subsequent rolling processes. Furthermore, the substrate material is preferably copper foil.

[0042] In some embodiments of this application, after providing the lithium metal layer substrate, a pretreatment of the lithium metal layer substrate is further included. Specifically, the pretreatment includes the following steps: First, the lithium metal layer is cleaned by placing the lithium-copper composite strip (lithium metal layer thickness of 5-30 μm and copper foil thickness of 4-12 μm) in dimethyl ethylene glycol (DME) and ultrasonically cleaning it for 30 s with a power of 300W and a power density of 0.3-0.6 W / cm² to remove grease contaminants and oxide layers from the lithium metal surface; then, the lithium metal layer is dried by using a gentle heating method to completely dry the residual DME to avoid organic solvent residue affecting the adhesion of subsequent coatings; finally, surface activation treatment is performed by treating the lithium metal layer with argon plasma in a high-purity argon protective atmosphere with a treatment power of 150W and a treatment time of 60 s. Plasma bombardment increases the surface energy of the lithium metal and enhances the density of surface active sites, providing an excellent interfacial bonding foundation for the subsequent electrostatic spraying coating and ensuring that the peel strength between the coating and the substrate is increased by more than 40%.

[0043] S200, Prepare the spray coating slurry.

[0044] In this step, a spray slurry is obtained by mixing a solid electrolyte, LiF functional filler, binder, dispersion medium, and additives.

[0045] In some embodiments of this application, the spraying slurry comprises, by mass percentage: 70-85 wt% solid electrolyte, 5-15 wt% LiF functional filler, and 8-12 wt% binder, with the balance being dispersion medium and additives.

[0046] In this application, a high proportion of solid electrolyte ensures excellent ionic conductivity and mechanical strength of the coating, while an appropriate amount of LiF functional filler reduces the lithium-ion diffusion barrier, induces uniform lithium-ion deposition, and inhibits dendrite growth. A suitable binder system provides sufficient mechanical strength and electrolyte tolerance while improving the coating's flexibility, allowing it to adapt to volume changes during lithium metal charging and discharging. Thus, the specific proportions of each component enable the spray slurry to achieve an optimal viscosity of 3000±500 mPa·s, ensuring good atomization and uniform deposition during electrostatic spraying while avoiding component sedimentation and segregation. This results in a dense, uniformly thick spray coating (with deviations controlled within ±5%), constructing a multi-layered synergistic protection mechanism where LiF provides ion channels, solid electrolyte enhances interface stability, and binder improves flexibility. This is beneficial for improving the cycle stability and safety of lithium metal batteries.

[0047] In some embodiments of this application, the particle size of the solid electrolyte is 0.1-5 μm.

[0048] In this application, the particle size of the solid electrolyte is limited to the aforementioned range. On the one hand, this particle size matches the 0.1-5μm charged particle size formed during electrostatic spraying, ensuring that the sprayed slurry can be uniformly atomized and stably deposited in the electrostatic field. This avoids the problems of uneven coating caused by large particles and easy agglomeration of small particles, keeping the coating thickness deviation within ±5%. On the other hand, the 0.1-5μm particle size range optimizes the contact interface between particles, forming a continuous ion conduction network, which is beneficial to improving the ionic conductivity of the coating. At the same time, it ensures the high mechanical strength characteristics of the solid electrolyte (Young's modulus up to 150GPa), enabling it to effectively physically block the penetration of lithium dendrites. In addition, this particle size range can also form a multi-scale composite structure with LiF functional fillers, ensuring the compactness of the coating and avoiding the problem of interfacial stress concentration caused by excessively large particles. This allows the coating to maintain structural integrity under volume changes during lithium metal charging and discharging, thereby improving the cycle stability and safety of lithium metal batteries.

[0049] In some embodiments of this application, the solid electrolyte includes at least one of lithium lanthanum zirconium oxide (LLZO) series solid electrolyte and lithium silicon phosphate (LSPO) solid electrolyte, wherein the lithium lanthanum zirconium oxide series solid electrolyte includes lithium lanthanum zirconium tantalum oxide solid electrolyte.

[0050] In this application, LLZO, as a garnet-type solid electrolyte, possesses excellent mechanical strength (Young's modulus up to 150 GPa) and good lithium-ion conductivity (up to 10 at room temperature). -4 ~10 -3 The S / cm concentration effectively blocks lithium dendrite penetration while exhibiting good chemical stability against metallic lithium; LSPO (or similar NASICON-type electrolytes) provides even higher ionic conductivity (up to 10 at room temperature). -3 The materials (on the order of S / cm) reduce interfacial impedance and promote rapid lithium-ion transport. Thus, the appropriate selection or combination of these two materials ensures both the mechanical stability and dendrite barrier of the coating, as well as sufficient ion conduction performance. In addition, the good interfacial compatibility between these two materials and lithium metal avoids serious side reactions with lithium metal, allowing the coating to maintain structural integrity and functional stability during long-term battery cycling, which is beneficial to improving the cycle life and safety of lithium metal batteries.

[0051] In some embodiments of this application, the adhesive comprises a composite system of polyvinylidene fluoride-hexafluoropropylene copolymer and polyethylene oxide.

[0052] In this application, a two-component binder composite system consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and polyethylene oxide (PEO) is used. PVDF-HFP, as the rigid component, provides excellent mechanical strength and electrolyte resistance, effectively enhancing the structural stability of the coating and preventing swelling or degradation during battery operation. PEO, as the flexible component, improves lithium-ion conductivity and interfacial adhesion. The ether oxygen groups in its molecular chain can coordinate with lithium ions, reducing interfacial impedance and promoting uniform lithium-ion transport. Therefore, the combined use of these two components results in a coating structure that combines rigidity and flexibility, maintaining sufficient mechanical strength (moderate Young's modulus) while possessing excellent flexibility. This effectively accommodates volume changes of up to 50%-300% during lithium metal charging and discharging, avoiding the coating cracking or peeling problems that are common in traditional single-binder systems.

[0053] In some embodiments of this application, the binder is dissolved in a solvent to form a binder solution, the solvent including at least one of N,N-dimethylformamide, acetone, ethyl acetate, and dimethyl sulfoxide, and the solid content of the binder solution is 12-15 wt%. Using the above-mentioned solvent system facilitates the complete dissolution and uniform dispersion of the binder, thereby avoiding phase separation problems; further limiting the solid content within the above range can prevent nozzle clogging during electrostatic spraying.

[0054] In some embodiments of this application, the dispersion medium includes cyclohexane. The selection of the above-mentioned dispersion medium, with a dielectric constant of 25.3, optimizes the atomization effect.

[0055] In some embodiments of this application, the LiF functional filler comprises nanoscale lithium fluoride.

[0056] In this application, the LiF functional filler is selected as nano-sized lithium fluoride. On the one hand, the nano-sized size can provide a large specific surface area and interfacial activity, enabling LiF to effectively reduce the diffusion barrier of lithium ions at the interface, promote the uniform migration and deposition of lithium ions, and solve the problem of lithium dendrite growth caused by uneven current density distribution. On the other hand, nano-sized LiF has higher reactivity and can preferentially react with active lithium at the interface to form a stable solid electrolyte interfacial film (SEI) rich in LiF in situ, which protects the lithium metal matrix.

[0057] In some embodiments of this application, the additive includes a rheology modifier, which includes hydroxypropyl methylcellulose.

[0058] In this application, the additive includes a rheology modifier, which includes hydroxypropyl methylcellulose (HPMC). HPMC, as a nonionic polymeric surfactant, can raise the Zeta potential of the slurry system to >40mV, which is far higher than the critical value for colloidal stability (±30mV), thereby enhancing the electrostatic repulsion between particles and thus helping to prevent the sedimentation of the sprayed slurry. Furthermore, the preferred amount of hydroxypropyl methylcellulose added is 0.2wt%.

[0059] S300, forming a spray coating.

[0060] In this step, an electrostatic spraying process is used to atomize and deposit the obtained spraying slurry onto the surface of the lithium metal layer to form a sprayed coating.

[0061] In some embodiments of this application, the electric field strength for electrostatic spraying is 10-80 kV. When the electric field strength is below 10 kV, the sprayed slurry droplets are insufficiently charged, and the Coulomb repulsion cannot effectively overcome their surface tension, resulting in a wide particle size distribution (>10 μm) of atomized particles. Furthermore, these particles are prone to agglomeration during flight, ultimately leading to a coating thickness deviation exceeding ±15%, with localized weak points becoming preferred growth sites for lithium dendrites. When the electric field strength is above 80 kV, it easily triggers corona discharge at the tip, making the trajectory of charged particles uncontrollable and preventing the formation of a uniform coating. By controlling the electric field strength within the preferred range of 10-80 kV, it is possible to ensure uniform charging of atomized particles, achieving self-dispersion in the electrostatic field, while avoiding over-discharge, thereby obtaining a sprayed coating with a thickness deviation within ±5% and a dense, defect-free structure.

[0062] In some embodiments of this application, the electrostatic spraying distance is 15-20 cm. This limited spraying distance provides sufficient flight time for charged particles, allowing the solvent in the spray slurry to fully evaporate before reaching the lithium metal surface, ensuring that the residual solvent content in the coating is less than 0.1 wt%, and avoiding porosity and interface defects caused by solvent residue.

[0063] In some embodiments of this application, the electrostatic spraying delivery pressure is 0.4-0.6 MPa. This limited delivery pressure can be matched with the 0.3 mm micron-level nozzle diameter, ensuring that the sprayed slurry passes through the nozzle at a stable flow rate, controlling the atomized particle size within the range of 0.1-3 μm, and effectively preventing nozzle clogging caused by particle aggregation.

[0064] In some embodiments of this application, the substrate temperature during electrostatic spraying is 20-80°C. Limiting the substrate temperature within this range can accelerate the evaporation of solvents in the spraying slurry and promote the interfacial fusion between the solid electrolyte particles and the lithium metal matrix.

[0065] In some embodiments of this application, the thickness of the sprayed coating is 0.3-5 μm. If the coating thickness is less than 0.3 μm, the mechanical strength of the artificial SEI layer is insufficient to physically block lithium dendrites, and lithium dendrites can easily penetrate the coating during cycling, causing short circuits. If the coating thickness is greater than 5 μm, it will significantly increase the diffusion path of lithium ions at the interface, leading to a surge in interface impedance. At the same time, the coating is prone to cracking or peeling due to excessive internal stress when the lithium metal expands in volume. By controlling the thickness within the range of 0.3-5 μm, the high mechanical strength of the solid electrolyte can be used to effectively block dendrites while maintaining a low interface impedance. Meanwhile, the flexibility of the coating itself is sufficient to adapt to the volume changes of the lithium metal, achieving the best balance between protective effectiveness and electrochemical performance.

[0066] In some embodiments of this application, the particle size of the atomized charged particles in the electrostatic spraying is 0.1-5 μm. Controlling the particle size of the atomized charged particles within the 0.1-5 μm range in electrostatic spraying serves two purposes: firstly, it matches the high-voltage electrostatic field (10-80 kV), allowing the charged particles to achieve highly uniform dispersion during flight through Coulomb repulsion, avoiding uneven coating thickness caused by particle aggregation and ensuring that the coating thickness deviation is controlled within ±5%; secondly, it adapts to the 0.3 mm nozzle diameter, preventing nozzle clogging while allowing the particles to complete solvent evaporation within a 15-20 cm spraying distance (residual solvent <0.1 wt%), forming a dense, defect-free coating structure.

[0067] S400, post-processing.

[0068] In this step, the lithium-metal layer substrate after spraying undergoes post-processing. Specifically, the post-processing includes two steps: hot pressing and slitting. First, hot pressing is performed, where the coated lithium-metal layer substrate is processed through a twin-roll calender. The pressure is controlled at 0.5 t, the temperature at 100℃, and the linear speed at 1 m / min. This combination of process parameters allows the coating to form a tight physical-chemical bond with the lithium metal layer surface, thereby enhancing the interfacial bonding strength (by more than 40%) and eliminating micropore defects. Subsequently, slitting is performed in an ultra-dry environment with a dew point below -40℃. The ambient moisture content is controlled to be below 1 ppm, effectively preventing moisture from reacting with the active lithium metal to form harmful byproducts such as lithium hydroxide. This ensures the interfacial stability and electrochemical performance of the final product during storage and subsequent battery assembly.

[0069] Secondly, this application provides a lithium metal anode. According to an embodiment of this application, the lithium metal anode 100 is prepared using the above-described modification method. See [link to relevant documentation]. Figure 2The lithium metal anode 100 includes a substrate 10, a lithium metal layer 20, and a spray coating 30. The lithium metal layer 20 is disposed on at least one side of the substrate 10, and the spray coating 30 is disposed on the side of the lithium metal layer 20 away from the substrate 10.

[0070] The lithium metal anode provided in this application is prepared by electrostatic spraying modification method. The surface of the lithium metal anode forms a multifunctional spray coating with uniform thickness and exhibits excellent cycle stability and safety, effectively suppressing lithium dendrite growth.

[0071] Thirdly, this application provides a lithium metal battery, which, according to an embodiment of this application, includes the aforementioned lithium metal negative electrode.

[0072] The lithium metal battery provided in this application includes the above-mentioned modified lithium metal anode. The battery forms a coating by electrostatic spraying, which can solve the dendrite growth problem caused by uneven anode interface in traditional lithium metal batteries and improve the cycle performance of lithium metal batteries.

[0073] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0074] Unless otherwise specified, the lithium lanthanum zirconium oxide (LLZO) solid electrolyte and lithium silicon phosphate (LSPO) solid electrolyte used in the examples and comparative examples are all industrial-grade powders with a particle size of 0.1-2 μm, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and polyethylene oxide (PEO) are battery-grade raw materials, nano-sized LiF is a battery-grade powder with an average particle size of 50 nm, and hydroxypropyl methylcellulose (HPMC) is an industrial-grade rheology modifier. All of the above raw materials are commercially available products; the mixed solvents, cyclohexane, etc. are all analytical grade reagents and were also purchased commercially.

[0075] In the examples and comparative examples, the lithium-containing metal layer substrate used was a lithium-copper composite strip, with a copper foil substrate thickness of 4-12 μm and a lithium metal layer thickness of 5-30 μm; the nozzle diameter of the electrostatic spraying equipment was 0.3 mm.

[0076] Example 1 Example 1 of this application provides a lithium metal anode and a lithium metal battery, and the specific preparation methods of the two are as follows: 1. Lithium metal anode: 1) Provide a substrate containing a lithium metal layer: Select a lithium-copper composite strip with a copper foil thickness of 5μm and a lithium metal layer thickness of 20μm; 2) Substrate pretreatment: The above-mentioned lithium copper composite strip is cleaned in an ultrasonic bath of ethylene glycol dimethyl ether (DME) (power 300W, power density 0.5W / cm², time 30s), heated and dried to remove residual DME, and then subjected to argon plasma treatment in an argon atmosphere (power 150W, time 60s). 3) Preparation of spray coating slurry: By mass percentage, the spray coating slurry consists of 76% LLZO solid electrolyte, 10% nano-sized LiF functional filler, and 10% binder, with the balance being cyclohexane dispersion medium and 0.2 wt% HPMC rheology modifier; the binder is a composite system of PVDF-HFP and PEO in a mass ratio of 7:3. The binder is dissolved in a mixed solvent of acetone:N-methylpyrrolidone=7:3 to prepare a slurry with a solid content of 13 wt%. Then, LLZO and nano-LiF are added sequentially and ball-milled for 4 h (300 rpm, zirconia ball diameter 0.5 mm). Finally, HPMC is added and ultrasonically dispersed for 30 min to obtain a spray coating slurry with a viscosity of 3000±500 mPa·s. 4) Electrostatic spraying process: Set the electric field strength to 30kV, the spraying distance to 18cm, the conveying pressure to 0.5MPa, and the substrate temperature to 60℃. Atomize the spraying slurry into charged particles with a particle size of 0.1-5μm and deposit them on the surface of the lithium metal layer to form a spray coating with a thickness of 2μm. 5) Post-processing: The coated lithium-copper composite strip is hot-pressed and shaped by a twin-roll calender (pressure 0.5t, temperature 100℃, linear speed 1m / min), and then wound and cut in a drying room with a dew point <-40℃ to obtain the modified lithium metal anode.

[0077] 2. Lithium metal battery: The modified lithium metal anode is used as the anode, NCM811 is used as the cathode, polypropylene porous membrane is used as the separator, and carbonate mixed electrolyte is used as the electrolyte. The battery is assembled into a 3Ah soft-pack lithium metal battery using conventional soft-pack battery manufacturing process.

[0078] Example 2 Example 2 provides a lithium metal anode and a lithium metal battery, the specific preparation methods of which are as follows: 1. Lithium metal anode: 1) Provide a substrate containing a lithium metal layer: Select a lithium-copper composite strip with a copper foil thickness of 4μm and a lithium metal layer thickness of 5μm; 2) Substrate pretreatment: The above-mentioned lithium copper composite strip is cleaned in an ultrasonic bath of ethylene glycol dimethyl ether (DME) (power 300W, power density 0.3W / cm², time 30s), heated and dried to remove residual DME, and then subjected to argon plasma treatment in an argon atmosphere (power 150W, time 60s). 3) Preparation of spray coating slurry: By mass percentage, the spray coating slurry consists of 70% LLZO solid electrolyte, 15% nano-sized LiF functional filler, and 12% binder, with the balance being cyclohexane dispersion medium and 0.2wt% HPMC rheology modifier; the binder is a composite system of PVDF-HFP and PEO in a mass ratio of 7:3. The binder is dissolved in a mixed solvent of acetone:N-methylpyrrolidone=7:3 to prepare a slurry with a solid content of 12wt%. Then, LLZO and nano-LiF are added sequentially and ball-milled for 4 hours (300 rpm, zirconia ball diameter 0.5 mm). Finally, HPMC is added and ultrasonically dispersed for 30 minutes to obtain a spray coating slurry with a viscosity of 3000±500 mPa·s. 4) Electrostatic spraying process: Set the electric field strength to 10kV, the spraying distance to 15cm, the conveying pressure to 0.4MPa, and the substrate temperature to 20℃. Atomize the spraying slurry into charged particles with a particle size of 0.1-5μm and deposit them on the surface of the lithium metal layer to form a spray coating with a thickness of 0.3μm. 5) Post-processing: The coated lithium-copper composite strip is hot-pressed and shaped by a twin-roll calender (pressure 0.5t, temperature 100℃, linear speed 1m / min), and then wound and cut in a drying room with a dew point <-40℃ to obtain the modified lithium metal anode.

[0079] 2. Lithium metal battery: Same as in Example 1.

[0080] Example 3 Example 3 provides a lithium metal anode and a lithium metal battery, the specific preparation methods of which are as follows: 1. Lithium metal anode: 1) Provide a substrate containing a lithium metal layer: Select a lithium-copper composite strip with a copper foil thickness of 12μm and a lithium metal layer thickness of 30μm; 2) Substrate pretreatment: The above-mentioned lithium copper composite strip is cleaned in an ultrasonic bath of ethylene glycol dimethyl ether (DME) (power 300W, power density 0.6W / cm², time 30s), heated and dried to remove residual DME, and then subjected to argon plasma treatment in an argon atmosphere (power 150W, time 60s). 3) Preparation of spray coating slurry: By mass percentage, the spray coating slurry consists of 85% LLZO solid electrolyte, 5% nano-sized LiF functional filler, and 8% binder, with the balance being cyclohexane dispersion medium and 0.2 wt% HPMC rheology modifier; the binder is a composite system of PVDF-HFP and PEO in a mass ratio of 7:3. The binder is dissolved in a mixed solvent of acetone:N-methylpyrrolidone=7:3 to prepare a slurry with a solid content of 15 wt%. Then, LLZO and nano-LiF are added sequentially and ball-milled for 4 h (300 rpm, zirconia ball diameter 0.5 mm). Finally, HPMC is added and ultrasonically dispersed for 30 min to obtain a spray coating slurry with a viscosity of 3000±500 mPa·s. 4) Electrostatic spraying process: Set the electric field strength to 80kV, the spraying distance to 20cm, the conveying pressure to 0.6MPa, and the substrate temperature to 80℃. Atomize the spraying slurry into charged particles with a particle size of 0.1-5μm and deposit them on the surface of the lithium metal layer to form a spray coating with a thickness of 5μm. 5) Post-processing: The coated lithium-copper composite strip is hot-pressed and shaped by a twin-roll calender (pressure 0.5t, temperature 100℃, linear speed 1m / min), and then wound and cut in a drying room with a dew point <-40℃ to obtain the modified lithium metal anode.

[0081] 2. Lithium metal battery: Same as in Example 1.

[0082] Comparative Example 1 Comparative Example 1 was prepared using the same method as Example 1, except that electrostatic spraying was not used; instead, a brush coating process was used to coat the lithium metal layer with the sprayed slurry. All other parameters were the same.

[0083] Performance testing The lithium metal anodes and lithium metal batteries prepared in Examples 1-3 and Comparative Example 1 were subjected to performance tests. The test process included: Coating thickness uniformity test: Using a scanning electron microscope (SEM) at 5000x magnification, 10 equidistant points were transversely intercepted along the lithium metal anode, and the coating thickness at each point was measured. The relative standard deviation (RSD, %) was calculated to characterize the thickness uniformity. The smaller the RSD value, the better the uniformity.

[0084] Cyclic performance test: The assembled 0.5Ah soft-pack lithium metal battery was cycled at 25±2℃ with a charge / discharge rate of 0.5C / 0.5C, and the capacity retention rate (%) after 100 cycles was calculated.

[0085] Lithium metal surface dendrite test: After the battery has completed 100 cycles, it is disassembled in an argon glove box, the lithium metal anode is removed, and its surface morphology is observed using a scanning electron microscope (SEM) to evaluate the growth of lithium dendrites.

[0086] The test results are shown in Table 1.

[0087] Table 1 Test Results

[0088] Table 1 shows that the lithium metal anodes prepared using the electrostatic spraying process of this application (Examples 1-3) have a smaller coating thickness deviation than Comparative Example 1, indicating that electrostatic spraying achieves highly uniform coating deposition. The capacity retention rate after 100 cycles is much better than that of Comparative Example 1, and no or very few lithium dendrites appear on the surface of the anode, while a large number of dendrites appear in Comparative Example 1.

[0089] The above results demonstrate that the lithium metal anode modification method provided in this application, through precise control of electrostatic spraying process parameters and coating composition, can construct a multifunctional composite coating with uniform thickness and strong adhesion on the lithium metal surface. This coating can effectively inhibit lithium dendrite growth and stabilize the electrode interface during long-term cycling, thereby significantly improving the cycle life and safety of lithium metal batteries. Comparative Example 1, due to its brush coating process, suffers from poor coating uniformity and adhesion, failing to provide continuous and effective protection, resulting in rapid performance degradation of the battery.

[0090] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0091] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0092] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for modifying a lithium metal anode, characterized in that, Includes the following steps: Provide a substrate containing a lithium metal layer; Preparation of spray coating slurry; An electrostatic spraying process is used to atomize and deposit the spraying slurry onto the surface of the lithium metal layer to form a sprayed coating. Post-treatment is performed on the lithium-containing metal layer substrate after spraying.

2. The modification method as described in claim 1, characterized in that, The spray coating slurry comprises, by mass percentage: 70-85 wt% solid electrolyte, 5-15 wt% LiF functional filler, and 8-12 wt% binder, with the balance being dispersion medium and additives.

3. The modification method as described in claim 2, characterized in that, The solid electrolyte has a particle size of 0.1-5 μm; and / or, The solid electrolyte includes at least one of lithium lanthanum zirconium oxide series solid electrolytes and lithium silicon phosphate solid electrolytes, wherein the lithium lanthanum zirconium oxide series solid electrolytes include lithium lanthanum zirconium tantalum oxide solid electrolytes; and / or... The adhesive comprises a composite system of polyvinylidene fluoride-hexafluoropropylene copolymer and polyethylene oxide.

4. The modification method as described in claim 3, characterized in that, The adhesive is dissolved in a mixed solvent to form an adhesive solution, the mixed solvent including at least one of N,N-dimethylformamide, acetone, ethyl acetate and dimethyl sulfoxide, and the solid content of the adhesive solution is 12-15 wt%.

5. The modification method as described in claim 2, characterized in that, The dispersion medium includes cyclohexane; and / or, The LiF functional filler includes nano-sized lithium fluoride; and / or, The additive includes a rheology modifier, which includes hydroxypropyl methylcellulose.

6. The modification method as described in claim 1, characterized in that, The electric field strength of the electrostatic spraying is 10-80kV; and / or, The electrostatic spraying distance is 15-20cm; and / or, The electrostatic spraying process uses a conveying pressure of 0.4-0.6 MPa; and / or, The substrate temperature during electrostatic spraying is 20-80℃.

7. The modification method as described in claim 1, characterized in that, The thickness of the lithium metal layer is 5-30 μm; and / or, The thickness of the substrate is 4-12 μm; and / or, The thickness of the sprayed coating is 0.3-5 μm.

8. The modification method as described in claim 1, characterized in that, In the electrostatic spraying process, the particle size of the atomized charged microparticles is 0.1-5 μm.

9. A lithium metal anode, characterized in that, The lithium metal anode is prepared using the modification method described in any one of claims 1-8.

10. A lithium metal battery, characterized in that, The lithium metal battery includes the lithium metal anode as described in claim 9.

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