Light-weight intermediate layer based on compression molding, lithium metal composite negative electrode, solid-state battery and preparation method of solid-state battery

Abstract

The invention belongs to the technical field of solid-state batteries, and particularly relates to a light-weight middle layer based on compression molding, a lithium metal composite negative electrode, a solid-state battery and a preparation method of the light-weight middle layer based on compression molding. The upper layer and the lower layer of the light-weight middle layer based on compression molding are carbon-based material powder film layers formed by compressing a carbon-based material, and the middle layer is an ultrathin lithium film layer; the lightweight intermediate layer design of the sandwich structure can inhibit the growth of lithium dendrites, significantly improve the safety of the battery, relieve the volume expansion of the negative electrode and improve the specific discharge capacity of the battery, and has the advantages of high charge transfer efficiency, high initial coulombic efficiency, simple preparation process and industrialization universality.

Description

Lightweight interlayer based on compression molding, lithium metal composite anode, solid-state battery and its preparation method Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to the field of lithium metal anode solid-state battery technology, and particularly to a lightweight intermediate layer based on compression molding, a lithium metal composite anode, a solid-state battery and its preparation method. Background Technology

[0002] Lithium metal, with its superior electrochemical properties, has become an ideal material for next-generation high-energy-density solid-state battery anodes: its theoretical specific capacity reaches 3860 mAh / g, the highest among currently known metal electrode materials; its electrochemical potential is as low as -3.04V (vs. SHE), which can impart higher open-circuit voltage to the battery; and it also possesses low density characteristics, which can effectively improve the volumetric energy density and gravimetric energy density of the battery. Compared with silicon-based anodes, such as silicon-carbon composites, lithium metal has unique advantages in solid-state battery systems: it can achieve integrated assembly and long-cycle testing of pouch cells under lower assembly pressure, without the need for complex pressure maintenance systems, significantly reducing the process difficulty and equipment cost of large-scale battery production, and showing broad commercial application prospects.

[0003] However, two major technological bottlenecks in the practical application of lithium metal anodes severely restrict the industrialization of high-safety, high-energy-density solid-state batteries: First, lithium metal undergoes drastic volume changes during charge-discharge cycles. This volume effect easily leads to electrode structure collapse, active material shedding, and interfacial contact failure between lithium metal and the solid electrolyte, resulting in a sharp increase in battery internal resistance and rapid capacity decay. Second, the electrochemical deposition process of lithium metal is uncontrollable, easily forming lithium dendrites. These dendrites can continuously grow and pierce the solid electrolyte membrane, causing internal short circuits and serious safety hazards such as thermal runaway. They also exacerbate side reactions, further deteriorating the battery's cycle stability and lifespan. Therefore, developing efficient modification technologies for lithium metal anodes, using core strategies such as interface control, three-dimensional current collector design, and artificial solid electrolyte interface (SEI) construction to solve the two major problems of volume expansion and lithium dendrite growth, is a key breakthrough for promoting the development of high-energy-density, high-safety solid-state batteries, and has significant academic value and industrial application implications.

[0004] Among numerous strategies for modifying lithium metal anodes, constructing a three-dimensional lithiophilic framework is one of the most widely studied and promising technical approaches. This strategy, by introducing a three-dimensional support structure with high specific surface area, good conductivity, and lithiophilic properties onto the lithium metal anode side, achieves the following core functions: First, it provides sufficient lithium deposition sites, inducing uniform nucleation and deposition of lithium metal, thereby suppressing the growth of lithium dendrites at the source; second, it utilizes the spatial confinement effect of the three-dimensional framework to buffer the volume expansion during lithium metal cycling, maintaining the integrity of the electrode structure; and third, it improves the interfacial contact between the electrode and the electrolyte, reduces interfacial impedance, and enhances charge transport efficiency.

[0005] Several existing technologies have disclosed methods for preparing composite anodes based on three-dimensional lithiophilic frameworks of lithium metal. For example, Chinese patent application CN114231954A discloses a method for preparing composite anodes by modifying commercial foam metals (such as foamed copper and foamed nickel) with cobalt oxide nanosheets and then using a molten lithium hot-injection process. This method has the advantages of relatively simple process and low raw material cost, and to a certain extent, it achieves lithium dendrite suppression and improves the coulombic efficiency and cycle life of the battery. However, it still has significant drawbacks: the molten lithium injection process needs to be carried out in a high-temperature environment, which poses serious safety risks and requires extremely high process safety control; the foam metal framework itself has a high density, which will significantly increase the mass ratio of inactive materials in the battery, leading to a decrease in the overall energy density of the battery; the chemical and electrochemical stability of the lithiophilic coating formed by cobalt oxide nanosheets during long-term charge-discharge cycles has not been fully verified, and it is prone to peeling or failure, affecting the long-term cycle reliability of the battery.

[0006] Chinese patent application CN116230871A discloses a technical solution for forming a nanoscale in-situ protective layer by combining high-temperature hot-melt composite lithium metal with a three-dimensional support material and utilizing a non-metallic reactive fluid. This in-situ protective layer can alleviate volume changes in lithium metal and reduce interfacial side reactions to some extent, thereby improving the cycle stability of the battery. However, it still has the following technical limitations: the high-temperature hot-melt process places stringent requirements on the high-temperature resistance and temperature control precision of the production equipment, resulting in high production costs; the in-situ formed protective layer is difficult to precisely control in terms of compositional uniformity and structural integrity, easily leading to local defects and failing to form a continuous and effective protective barrier; compared to non-in-situ prepared protective layers, the in-situ protective layer has poor controllability in chemical composition, thickness, and microstructure, making it difficult to adapt to the needs of different solid-state battery systems.

[0007] Chinese patent CN119601603B discloses a technical solution that combines lithium metal, metal X, and a polymer substrate film modified with polar functional groups to form a molecularly welded anchoring structure, and then derives a solid electrolyte at the negative electrode interface. This solution achieves lithium dendrite suppression, improved cycle stability, and enhanced safety through molecular-level interfacial bonding and in-situ electrolyte deriver. However, it still has the following shortcomings: the polymer substrate film is prone to chemical degradation or electrochemical redox reactions in the complex electrochemical environment of long-term charge-discharge cycles, leading to insufficient structural stability; the process of deriving the solid electrolyte at the interface is affected by various factors such as temperature, reaction time, and component ratio, making precise control of the deriver process difficult, and the uniformity of the derived products is poor, easily causing interfacial impedance inhomogeneity; this solution involves multi-step composite reactions and precise process control, resulting in a complex preparation process and high production costs, which is not conducive to large-scale production.

[0008] In summary, existing lithium metal anode modification technologies based on three-dimensional lithiophilic frameworks all suffer from varying degrees of drawbacks, such as high process complexity, significant safety risks, high costs, insufficient structural stability, and unresolved issues related to volume expansion and protective layer failure. Therefore, developing a structurally stable, simple-to-process, and lightweight lithium metal composite anode that can effectively control the volume expansion of lithium metal during cycling and prevent protective layer cracking or failure, while simultaneously meeting the demands of low cost and large-scale production, has become a pressing technical challenge in the field of high-energy-density solid-state batteries. Summary of the Invention

[0009] The present invention aims to provide a lithium metal composite anode with stable structure, simple process and light weight, so as to alleviate the technical problems of volume expansion and lithium dendrite growth during the cycling process of lithium metal anode, which lead to protective layer cracking or battery failure, while taking into account the needs of low cost and large-scale production.

[0010] In view of this, the present invention provides a lightweight intermediate layer based on compression molding, wherein the lightweight intermediate layer is used to form a lithium metal composite anode with lithium foil, the lightweight intermediate layer comprising a lithium film layer in the middle and carbon-based material powder film layers on both sides of the lithium film layer, wherein the carbon-based material powder film layers are prepared using one or more of zero-dimensional, one-dimensional, and two-dimensional carbon-based materials.

[0011] Furthermore, the carbon-based material powder film is prepared using micro / nano carbon materials and / or MXene materials.

[0012] Furthermore, the micro / nano carbon material is selected from one or more of graphene, carbon nanofibers, carbon nanotubes, fullerenes, carbon quantum dots, graphyne and super C carbon black.

[0013] Furthermore, the MXene material is selected from one or more of Ti3C2, Ti2C, V2C, Nb2C, Mo2C, Ti3CN, and Nb4C3.

[0014] Furthermore, the number of graphene and carbon nanotube layers is less than or equal to 15, and the lateral dimension of the graphene is 3-50 μm.

[0015] Furthermore, the carbon nanotubes have an outer diameter of 1-100 nm and a length of 200 nm-50 μm.

[0016] Furthermore, the outer diameter of the carbon nanofiber is 10-500 nm, and the length is 0.5-50 μm.

[0017] Furthermore, the MXene material has 20 or fewer layers and a lateral dimension of 100 nm to 40 μm.

[0018] Furthermore, the thickness of the lithium film layer is 1-20 μm.

[0019] A method for preparing a lightweight intermediate layer based on compression molding is provided. The method includes the following steps: coating a dispersion of carbon-based material onto a planar medium and drying it to obtain a carbon-based material powder film; stacking the carbon-based material powder film and a lithium film in the order of "carbon-based material powder film | lithium film | carbon-based material powder film" to obtain a stacked film; and pressing the stacked film to obtain a lightweight intermediate layer.

[0020] Furthermore, the thickness of the carbon-based material powder film obtained by coating is 1-100 μm.

[0021] Furthermore, the process of stacking carbon-based material powder film layers and lithium film layers to form a stacked film is carried out under inert gas protection.

[0022] Furthermore, the stacked membranes are pressed using a pressure of 0.1-1.5 ton.

[0023] A lightweight lithium metal composite anode based on compression molding includes a lithium foil layer, and the aforementioned lightweight intermediate layer is laminated on the surface of the lithium foil layer.

[0024] Furthermore, the lithium metal composite negative electrode also includes a current collector, which is prepared using one or more of copper foil, aluminum foil, copper foam, titanium foil, and stainless steel foil.

[0025] Furthermore, the structure of the lithium metal composite anode is a lightweight intermediate layer | lithium foil layer | current collector.

[0026] A method for preparing a lightweight lithium metal composite anode based on compression molding, used to prepare the aforementioned lightweight lithium metal composite anode based on compression molding, the method comprising the steps of: stacking a lightweight intermediate layer and lithium foil together and pressing them to obtain a lightweight lithium metal composite anode.

[0027] Further steps include: firstly, stacking a lightweight intermediate layer with a lithium foil and pressing them together; then stacking the resulting composite of the lightweight intermediate layer and lithium foil with a current collector and pressing them together to obtain a lightweight lithium metal composite anode.

[0028] Furthermore, in preparing the lightweight lithium metal composite anode, the pressing pressure is controlled at 0.2-1.5 tons.

[0029] Furthermore, the process of preparing the lightweight lithium metal composite anode is carried out under an inert atmosphere.

[0030] A solid-state battery comprising the aforementioned lightweight lithium metal composite anode based on compression molding.

[0031] Compared with the prior art, the lightweight intermediate layer, lithium metal composite anode, solid-state battery and its preparation method based on compression molding described in this invention have the following advantages: (1) Suppressing lithium dendrite growth and significantly improving battery safety: The lightweight intermediate layer with sandwich structure in the lithium metal composite anode of this invention is prepared using micro-nano carbon materials such as graphene and carbon nanotubes, as well as MXene materials such as Ti3C2. Therefore, it has a layered lithium-loving structure. For example, the lithium-loving functional groups such as -O and -F on the surface of the MXene material can work synergistically with the high specific surface area of ​​the carbon material, which can not only greatly disperse the local current density, but also provide a large number of uniformly distributed nucleation sites, reduce the lithium nucleation energy barrier to a low level, and guide the lateral orderly deposition of lithium ions. This design can avoid the formation of dendrites caused by uneven lithium deposition from the root, and effectively solve the safety hazard of dendrites piercing the electrolyte in traditional lithium metal anodes, allowing the battery to maintain structural integrity during long-term cycling.

[0032] (2) Alleviating negative electrode volume expansion and extending cycle life: The sandwich structure of the lightweight intermediate layer in this invention, through the layered composite structure design of "carbon-based skeleton - ultra-thin lithium film - carbon-based skeleton", provides sufficient buffer space for lithium deposition / stripping. At the same time, the composite skeleton formed by carbon materials and MXene has excellent mechanical strength (e.g., the elastic modulus of MXene material can reach 330 GPa), which can effectively restrain the volume expansion of lithium metal during charging and discharging, and avoid electrode cracking, pulverization and conductive network breakage. Meanwhile, the stable structural support keeps the electrode interface impedance at a low level for a long time, significantly extending the battery cycle life and solving the core pain point of poor cycle stability of traditional lithium metal negative electrodes.

[0033] (3) Lightweight design to break through the energy density bottleneck of full battery: Compared with the traditional heavy metal foam skeleton, the micro-nano carbon materials and MXene used in this invention have ultra-low density characteristics, which are much lower than those of metal matrix, thus significantly reducing the weight ratio of composite anode. Without sacrificing the active material loading, the energy density is improved by optimizing the electrode mass ratio, providing key support for the breakthrough of solid-state battery energy density and adapting to the application requirements of high-endurance new energy equipment.

[0034] (4) Enhanced charge transport efficiency and improved rate performance: The high conductivity of carbon materials, such as graphene and carbon nanotubes, combined with the synergistic effect of MXene interlayer channels, constructs a continuous and efficient electron / ion transport network. Carbon materials ensure rapid electron migration, while the functional groups and channel structure of MXene interlayers reduce the lithium-ion diffusion barrier. In addition, the tight contact between the carbon skeleton and the lithium film brought about by the pressing process enables rapid charge transport and low interface impedance. This allows the battery to maintain stable capacity output under high-rate charging and discharging scenarios, significantly improving rate performance and adapting to fast charging requirements.

[0035] (5) Simplified preparation process with industrial applicability: This invention uses a simple compression molding process to assemble the lightweight intermediate layer and composite anode, eliminating the need for complex high-temperature treatment or chemical modification steps. This reduces safety risks during production and decreases equipment investment and process costs. Furthermore, this process is highly compatible with existing battery production lines and can be flexibly adapted to the preparation of solid-state batteries of different specifications. It is also applicable to composite systems of various carbon-based materials and MXene, possessing broad applicability and potential for large-scale application. Attached Figure Description

[0036] Figure 1 is a voltage-specific capacity diagram of the first cycle of the mold battery assembled with lithium metal composite anode in Example 1 of the present invention; Figure 2 is a voltage-specific capacity diagram of the first cycle of the mold battery assembled with lithium metal composite anode in Example 2 of the present invention; Figure 3 is a voltage-specific capacity diagram of the first cycle of the mold battery assembled with lithium metal composite anode in Example 3 of the present invention; Figure 4 is a voltage-specific capacity diagram of the first cycle of the mold battery assembled with lithium metal composite anode in Example 4 of the present invention; Figure 5 is a voltage-specific capacity diagram of the first cycle of the mold battery assembled with lithium metal anode in Comparative Example 1 of the present invention. Detailed Implementation

[0037] The technical solutions in this application will be clearly described below with reference to specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application are within the scope of protection of this application.

[0038] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0039] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] In view of the problems existing in the prior art, the present invention provides a lightweight intermediate layer based on compression molding, which is used to form a lithium metal composite anode with lithium foil. The lightweight intermediate layer is used to suppress the generation and growth of lithium dendrites, and at the same time, it can prevent the structural collapse of the lithium metal composite anode by inducing uniform deposition of lithium ions. This results in the lithium metal composite anode containing the lightweight intermediate layer having good interface stability and excellent initial specific capacity and initial coulombic efficiency.

[0042] The structure and preparation process of the lightweight intermediate layer of the present invention are described in detail below: Specifically, the lightweight intermediate layer has a sandwich structure, which includes a lithium film layer in the middle and carbon-based material powder film layers on both sides of the lithium film layer. The carbon-based material powder film layers are prepared using one or more of zero-dimensional, one-dimensional or two-dimensional carbon-based material powders.

[0043] It should be noted that in the field of materials science, dimension specifically refers to the dimensional characteristics of a material along the three coordinate axes in space. The core difference between zero-dimensional, one-dimensional, and two-dimensional materials lies in the limited number of spatial dimensions. Zero-dimensional materials refer to materials whose length, width, and height are all at the nanometer scale (e.g., 1-100 nm), exhibiting a "point-like" or "spherical" structure with no obvious directionality. One-dimensional materials refer to materials with only one spatial dimension (e.g., length at the micrometer scale, 1-1000 μm) and the other two dimensions (diameter / thickness) at the nanometer scale (e.g., 1-100 nm), exhibiting a "linear," "tubular," or "fibrous" structure with obvious length directionality. Two-dimensional materials refer to materials with only two spatial dimensions (e.g., length and width at the micrometer scale, 1-1000 μm) and the third dimension (e.g., thickness at the nanometer scale, 1-100 nm), exhibiting a "sheet-like" or "layered" structure with obvious planar extensibility.

[0044] As a preferred example of the present invention, the carbon-based material powder film is prepared using micro / nano carbon materials and / or MXene materials.

[0045] As some specific examples of the present invention, the micro / nano carbon material is selected from one or more of graphene, carbon nanofibers, carbon nanotubes, fullerenes, carbon quantum dots, graphyne and super C carbon black.

[0046] As some specific examples of the present invention, the MXene material is selected from one or more of Ti3C2, Ti2C, V2C, Nb2C, Mo2C, Ti3CN, and Nb4C3.

[0047] As a preferred example of the present invention, the number of graphene and carbon nanotube layers is less than or equal to 15 layers, and more preferably 1-5 layers.

[0048] As a preferred example of the present invention, the graphene has a lateral dimension of 3-50 μm, more preferably 15-35 μm.

[0049] As a preferred example of the present invention, the outer diameter of the carbon nanotube is 1-100 nm, more preferably 20-50 nm.

[0050] As a preferred example of the present invention, the length of the carbon nanotube is 200nm-50μm, more preferably 1-30μm.

[0051] As a preferred example of the present invention, the outer diameter of the carbon nanofiber is 10-500 nm, more preferably 30-100 nm.

[0052] As a preferred example of the present invention, the length of the carbon nanofiber is 0.5-50 μm, more preferably 20-35 μm.

[0053] As a preferred example of the present invention, the MXene material has 20 or fewer layers and a lateral dimension of 100 nm to 40 μm; more preferably, it has 1 to 10 layers and a lateral dimension of 5 to 15 μm.

[0054] As a preferred example of the present invention, the thickness of the lithium film layer is 1-20 μm; more preferably 5-10 μm.

[0055] The preferred dimensions described above provide a high specific surface area, thereby reducing local current density.

[0056] Furthermore, the present invention also provides a method for preparing the above-mentioned lightweight intermediate layer based on compression molding, comprising the following steps: S1, dispersing carbon-based material powder in a dispersion medium to obtain a dispersion of carbon-based material; S2, coating the dispersion of carbon-based material obtained in step S1 onto a planar medium, and drying it to obtain a carbon-based material powder film layer; S3, stacking the carbon-based material powder film layer obtained in step S2 and a pre-made lithium film layer together in the order of "carbon-based material powder film layer | lithium film layer | carbon-based material powder film layer" to obtain a stacked film; S4, pressing the stacked film obtained in step S3 to obtain the lightweight intermediate layer.

[0057] As some examples of the present invention, the content of carbon-based material in the dispersion of the carbon-based material is 0.05~30wt%.

[0058] As some examples of the present invention, the dispersion medium is water, preferably deionized water.

[0059] As other examples of the present invention, in addition to water, other media such as NMP, DMF, THF, ethanol, ethylene glycol, and aqueous buffer solutions (such as Tris-HCl) can be used as dispersion media for the dispersion of carbon-based materials.

[0060] As some examples of the present invention, in addition to carbon-based material powder and dispersion medium, additives such as dispersants and surfactants may also be added to the dispersion of the carbon-based material.

[0061] As some examples of the present invention, the specific process of step S1 is as follows: carbon-based material powder is dispersed in a dispersion medium, and after being dispersed evenly in an ultrasonic machine or a vibrating homogenizer, a dispersion of carbon-based material is obtained.

[0062] As some other examples of the present invention, the specific process of step S1 is as follows: the water solvent of carbon-based material is directly used as raw material, and the water solvent of carbon-based material is redispersed evenly in an ultrasonic machine or a vibrating homogenizer to obtain a water dispersion of carbon-based material, ensuring that the powder in the water solvent does not re-agglomerate.

[0063] As some examples of the present invention, the specific process of step S2 is as follows: the aqueous dispersion of the carbon-based material obtained in step S1 is coated on a planar medium such as a glass plate or PET film, and after natural drying, a carbon-based material powder film is obtained.

[0064] As a preferred example of the present invention, the natural air-drying time in step S2 is 6-36 hours, more preferably 24-32 hours.

[0065] As a preferred example of the present invention, the thickness of the carbon-based material powder film obtained in step S2 is 1-100 μm, more preferably 5-30 μm. It should be noted that the thickness of the carbon-based material powder film here refers to its size after coating and drying.

[0066] As a preferred example of the present invention, step S3 is performed under inert gas protection.

[0067] As some specific examples of the present invention, the inert gas in step S3 is nitrogen or argon.

[0068] As some examples of the present invention, the specific process of step S4 is as follows: the stacked film obtained in step S3 is pressed under the action of a press to finally obtain a lightweight intermediate layer with a sandwich structure.

[0069] As a preferred example of the present invention, the pressure of the press in step S4 is 0.1-1.5 ton, more preferably 0.2-0.5 ton.

[0070] During the pressing process, since the thickness of the lithium film layer is very small, if the pressure is too high, it will cause the lithium film layer to be damaged and crushed. In order to ensure the stability of the sandwich structure, the pressure of the press in step S4 is set to 0.1-1.5 ton.

[0071] In addition, the present invention also provides a lightweight lithium metal composite anode based on compression molding, wherein the lithium metal composite anode includes a lithium foil layer and the aforementioned lightweight intermediate layer is laminated on the surface of the lithium foil layer.

[0072] As some examples of the present invention, the lithium metal composite negative electrode further includes a current collector, which is prepared using one or more of copper foil, aluminum foil, copper foam, titanium foil, and stainless steel foil.

[0073] Preferably, the structure of the lithium metal composite anode is a lightweight intermediate layer | lithium foil layer | current collector.

[0074] Furthermore, the present invention also provides a method for preparing the above-mentioned lightweight lithium metal composite anode based on compression molding, which includes the following steps: P1, stacking the lightweight intermediate layer and lithium foil together and pressing them to obtain a lightweight lithium metal composite anode.

[0075] As some examples of the present invention, when the lightweight lithium metal composite anode further includes a current collector, the preparation method of the lightweight lithium metal composite anode based on compression molding includes the following steps: P1, firstly, the lightweight intermediate layer and lithium foil are stacked together and pressed; P2, then the resulting composite of the lightweight intermediate layer and lithium foil layer is stacked together with the current collector and pressed to obtain the lightweight lithium metal composite anode.

[0076] As a preferred example of the present invention, when preparing the lightweight lithium metal composite anode, the pressing pressure in steps P1 and P2 is controlled at 0.2-1.5 ton, more preferably 0.2-0.5 ton.

[0077] As a preferred example of the present invention, the process of preparing the lightweight lithium metal composite anode is carried out under an inert atmosphere.

[0078] As some specific examples of the present invention, the lightweight lithium metal composite anode based on pressing can be stamped in a 10mm punch to obtain a lithium metal composite anode with a diameter of 10mm, which is used for solid-state pressurized mold battery assembly and its electrochemical performance is tested.

[0079] The present invention also provides a solid-state battery comprising the above-described lightweight lithium metal composite anode based on compression molding.

[0080] In this invention, the upper and lower layers of the lightweight intermediate layer are carbon-based material powder films formed by pressing carbon-based material powder, and the middle layer is an ultra-thin lithium film layer, which can be used as the skeleton of the negative electrode. When this sandwich structure lightweight intermediate layer design replaces the traditional thick negative electrode skeleton such as foamed copper, the overall mass ratio of the negative electrode can be significantly reduced due to the low weight ratio of the carbon-based material itself. At the same time, the electrode space utilization rate is optimized, reserving capacity for more active materials, and ultimately achieving an effective improvement in the energy density of the soft-pack battery cell.

[0081] Furthermore, the carbon-based framework formed by the upper and lower carbon-based material powder films possesses lithium-affinity properties, which can guide the uniform distribution of the lithium film layer in the middle, thereby suppressing the problem of local current density imbalance. This homogenization design can avoid uneven stripping and deposition of lithium ions during charging and discharging, reduce the risk of lithium dendrite growth, and significantly improve the reversibility of lithium metal charging and discharging, ensuring the stability of electrode reactions.

[0082] Furthermore, the carbon-based framework formed by the upper and lower carbon-based material powder films is prepared using zero-dimensional, one-dimensional, or two-dimensional materials. These materials combine high conductivity with lightweight properties, providing the negative electrode with reliable current collection functionality. Even under extreme conditions where lithium metal is completely desorbed, the continuity of the electrode's conductive path can still be maintained, preventing a sharp drop in battery performance due to conductivity failure.

[0083] Meanwhile, the carbon-based framework formed by this carbon-based material powder film possesses excellent mechanical properties, which can effectively buffer the volume deformation of the electrodes during battery cycling and suppress structural collapse. Furthermore, the stable framework structure can constrain the uniformity of electrochemical reactions, avoid performance degradation caused by localized overcharging and discharging, extend battery cycle life, and improve safety.

[0084] Compared with the prior art, the lightweight intermediate layer, lithium metal composite anode, solid-state battery and its preparation method based on compression molding provided by the present invention have the following technical advancements: (1) Suppressing lithium dendrite growth and significantly improving battery safety: The lightweight intermediate layer with sandwich structure in the lithium metal composite anode of the present invention is prepared using micro-nano carbon materials such as graphene and carbon nanotubes, as well as MXene materials such as Ti3C2. Therefore, it has a layered lithium-loving structure. For example, the lithium-loving functional groups such as -O and -F on the surface of the MXene material can work synergistically with the high specific surface area of ​​the carbon material, which can not only greatly disperse the local current density, but also provide a large number of uniformly distributed nucleation sites, reduce the lithium nucleation energy barrier to a low level, and guide the lateral orderly deposition of lithium ions. This design can avoid the formation of dendrites caused by uneven lithium deposition from the root, and effectively solve the safety hazard of dendrites piercing the electrolyte in traditional lithium metal anodes, allowing the battery to maintain structural integrity during long-term cycling.

[0085] (2) Alleviating negative electrode volume expansion and extending cycle life: The sandwich structure of the lightweight intermediate layer in this invention, through the layered composite structure design of "carbon-based skeleton - ultra-thin lithium film - carbon-based skeleton", provides sufficient buffer space for lithium deposition / stripping. At the same time, the composite skeleton formed by carbon materials and MXene has excellent mechanical strength (e.g., the elastic modulus of MXene material can reach 330 GPa), which can effectively restrain the volume expansion of lithium metal during charging and discharging, and avoid electrode cracking, pulverization and conductive network breakage. Meanwhile, the stable structural support keeps the electrode interface impedance at a low level for a long time, significantly extending the battery cycle life and solving the core pain point of poor cycle stability of traditional lithium metal negative electrodes.

[0086] (3) Lightweight design to break through the energy density bottleneck of full battery: Compared with the traditional heavy metal foam skeleton, the micro-nano carbon materials and MXene used in this invention have ultra-low density characteristics, which are much lower than those of metal matrix, thus significantly reducing the weight ratio of composite anode. Without sacrificing the active material loading, the energy density is improved by optimizing the electrode mass ratio, providing key support for the breakthrough of solid-state battery energy density and adapting to the application requirements of high-endurance new energy equipment.

[0087] (4) Enhanced charge transport efficiency and improved rate performance: The high conductivity of carbon materials, such as graphene and carbon nanotubes, combined with the synergistic effect of MXene interlayer channels, constructs a continuous and efficient electron / ion transport network. Carbon materials ensure rapid electron migration, while the functional groups and channel structure of MXene interlayers reduce the lithium-ion diffusion barrier. In addition, the tight contact between the carbon skeleton and the lithium film brought about by the pressing process enables rapid charge transport and low interface impedance. This allows the battery to maintain stable capacity output under high-rate charging and discharging scenarios, significantly improving rate performance and adapting to fast charging requirements.

[0088] (5) Simplified preparation process with industrial applicability: This invention uses a simple compression molding process to assemble the lightweight intermediate layer and composite anode, eliminating the need for complex high-temperature treatment or chemical modification steps. This reduces safety risks during production and decreases equipment investment and process costs. Furthermore, this process is highly compatible with existing battery production lines and can be flexibly adapted to the preparation of solid-state batteries of different specifications. It is also applicable to composite systems of various carbon-based materials and MXene, possessing broad applicability and potential for large-scale application.

[0089] To facilitate understanding of the present invention, specific examples and embodiments are provided below. Those skilled in the art should understand that these embodiments are merely illustrative and should not be considered as specific limitations of the invention.

[0090] Example 1 This example provides a lightweight lithium metal composite anode, which includes a 15μm lightweight intermediate layer and a 30μm lithium copper composite strip. The sandwich intermediate layer includes a 5μm ultrathin lithium film layer and a 5μm graphene film layer.

[0091] The preparation method of the lightweight lithium metal composite anode includes the following steps: 4 ml of a single-layer graphene aqueous dispersion is uniformly coated onto the surface of a PET film and dried at room temperature for 12 hours to obtain a graphene film; the graphene film is transferred to a glove box with argon as the inert gas, a 5 μm ultrathin lithium film is placed on the graphene film, and another graphene film is placed on top of the ultrathin lithium film. The three layers are then pressed together under a pressure of 0.2 tons to obtain a lightweight sandwich-structured intermediate layer; the PET film is peeled off, and a lithium-copper composite strip is placed on top of the graphene film and pressed again under a pressure of 0.5 tons to finally obtain the composite anode. During the preparation process, the interfaces of each layer have good contact, with no obvious bubbles or wrinkles, effectively ensuring the mechanical stability and electrochemical performance of the battery.

[0092] Example 2 This example provides a lightweight lithium metal composite anode, which includes a 9μm lightweight intermediate layer and a 30μm lithium-copper composite strip. The sandwich intermediate layer includes a 5μm ultrathin lithium film and a 2μm carbon nanotube film.

[0093] The preparation method of the lightweight lithium metal composite anode includes the following steps: 2 ml of carbon nanotube aqueous dispersion is uniformly coated onto a PET surface and dried at room temperature for 16 hours to obtain a carbon nanotube film; the carbon nanotube film is transferred to a glove box with argon as the inert gas, a 5 μm ultrathin lithium film is placed on the carbon nanotube film, and another layer of carbon nanotube film is placed on top of the ultrathin lithium film. The three layers are then pressed together under a pressure of 0.5 tons to obtain a lightweight sandwich-structured intermediate layer; the PET film is peeled off, and a lithium-copper composite strip is placed on top of the carbon nanotube film, and the mixture is pressed again to obtain the final composite anode. During the preparation process, the interfaces between the layers are in good contact, with no obvious bubbles or wrinkles, effectively ensuring the mechanical stability and electrochemical performance of the battery.

[0094] Example 3 This example provides a lightweight lithium metal composite anode, which includes a 21μm lightweight interlayer and a 30μm lithium-copper composite strip. The sandwich interlayer includes a 5μm ultrathin lithium film and an 8μm nanofiber film.

[0095] The preparation method of the lightweight lithium metal composite anode includes the following steps: 6 ml of nanofiber aqueous dispersion is uniformly coated onto a PET surface and dried at room temperature for 20 hours to obtain a nanofiber membrane; the nanofiber membrane is transferred to a glove box with argon as the inert gas, a 5 μm ultrathin lithium membrane is placed on the nanofiber membrane, and another nanofiber membrane is placed on top of the ultrathin lithium membrane. The three layers are then pressed together at a pressure of 0.4 ton to obtain a lightweight sandwich-structured intermediate layer; the PET membrane is peeled off, a lithium-copper composite strip is placed on top of the nanofiber membrane, and the membrane is pressed again to obtain the final composite anode. During the preparation process, the interfaces between the layers are in good contact, with no obvious bubbles or wrinkles, effectively ensuring the mechanical stability and electrochemical performance of the electrode.

[0096] Example 4 This example provides a lightweight lithium metal composite anode, which includes a 25μm lightweight interlayer and a 30μm lithium copper composite strip. The sandwich interlayer includes a 5μm ultrathin lithium film and a 10μm Ti3C2 film.

[0097] The preparation method of the lightweight lithium metal composite anode includes the following steps: 6 ml of a single-layer or few-layer Ti3C2 aqueous solvent dispersion is uniformly coated onto a PET surface and dried at room temperature for 20 hours to obtain a graphene film; the graphene film is transferred to a glove box with argon as the inert gas, a 5 μm ultrathin lithium film is placed on the Ti3C2 film, and another Ti3C2 film is placed on top of the ultrathin lithium film. The three layers are then pressed together under a pressure of 0.3 ton to obtain a lightweight sandwich-structured intermediate layer; the PET film is peeled off, and a lithium-copper composite strip is placed on top of the Ti3C2 film, and the mixture is pressed again to obtain the final composite anode. During the preparation process, the interfaces between the layers are in good contact, with no obvious bubbles or wrinkles, effectively ensuring the mechanical stability and electrochemical performance of the electrode.

[0098] The only difference between Comparative Example 1 and Example 1 is that no lightweight intermediate layer was added, and only a 30μm lithium-copper composite strip was used. All other conditions were the same as in Example 1.

[0099] Test Example 1: The lithium metal anodes prepared in Examples 1 to 4 and Comparative Example 1 were assembled with NCM811 cathode sheets to form a mold battery, and the first-cycle voltage-specific capacity was measured to obtain the first-cycle voltage-specific capacity diagrams shown in Figures 1 to 5.

[0100] As shown in Figures 1-5, the first-time efficiency of Examples 1 (83.72%), 2 (80.43%), 3 (77.81%), and 4 (82.59%) is relatively high. In contrast, the first-time efficiency of the lithium metal anode prepared in Comparative Example 1, which does not have the lightweight intermediate layer described in this invention, is only 53.21%. This indicates that the lithium metal composite anodes of these three examples have more reversible lithium ion insertion / extraction processes during the first charge and discharge, and better electrode structure stability and reaction kinetics.

[0101] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A lightweight intermediate layer based on compression molding, characterized in that, The lightweight intermediate layer is used to form a lithium metal composite negative electrode with lithium foil. The lightweight intermediate layer includes a lithium film layer in the middle and carbon-based material powder film layers on both sides of the lithium film layer. The carbon-based material powder film layers are prepared using one or more of zero-dimensional, one-dimensional, and two-dimensional carbon-based materials.

2. The lightweight intermediate layer based on compression molding according to claim 1, characterized in that, The carbon-based material powder film is prepared using micro / nano carbon materials and / or MXene materials.

3. The lightweight intermediate layer based on compression molding according to claim 2, characterized in that, The micro / nano carbon material is selected from one or more of graphene, carbon nanofibers, carbon nanotubes, fullerenes, carbon quantum dots, graphyne and super C carbon black.

4. The lightweight intermediate layer based on compression molding according to claim 2, characterized in that, The MXene material is selected from one or more of Ti3C2, Ti2C, V2C, Nb2C, Mo2C, Ti3CN, and Nb4C3.

5. The lightweight intermediate layer based on compression molding according to claim 3, characterized in that, The graphene and carbon nanotubes have 15 or fewer layers, and the graphene has a lateral dimension of 3-50 μm.

6. The lightweight intermediate layer based on compression molding according to claim 3, characterized in that, The carbon nanotubes have an outer diameter of 1-100 nm and a length of 200 nm-50 μm.

7. The lightweight intermediate layer based on compression molding according to claim 3, characterized in that, The outer diameter of the carbon nanofiber is 10-500 nm, and the length is 0.5-50 μm.

8. The lightweight intermediate layer based on compression molding according to claim 2 or 4, characterized in that, The MXene material has 20 or fewer layers and a lateral dimension of 100nm-40μm.

9. The lightweight intermediate layer based on compression molding according to claim 1, characterized in that, The thickness of the lithium film layer is 1-20 μm.

10. A method for preparing a lightweight interlayer based on compression molding, characterized in that, The method for preparing the lightweight intermediate layer based on compression molding according to any one of claims 1 to 9 includes the steps of: coating a dispersion of carbon-based material onto a planar medium and drying it to obtain a carbon-based material powder film layer. Carbon-based material powder film and lithium film are stacked together in the order of "carbon-based material powder film | lithium film | carbon-based material powder film" to obtain a stacked film; The stacked films are pressed to obtain a lightweight intermediate layer.

11. The method for preparing a lightweight intermediate layer based on compression molding according to claim 10, characterized in that, The thickness of the carbon-based material powder film obtained by coating is 1-100 μm.

12. The method for preparing a lightweight intermediate layer based on compression molding according to claim 10, characterized in that, The process of stacking carbon-based material powder film layers with lithium film layers to form a stacked film is carried out under the protection of inert gas.

13. The method for preparing a lightweight intermediate layer based on compression molding according to claim 10, characterized in that, The stacked films are pressed using a pressure of 0.1-1.5 ton.

14. A lightweight lithium metal composite anode based on compression molding, characterized in that, It includes a lithium foil layer, on the surface of which is laminated the lightweight intermediate layer as described in any one of claims 1 to 9.

15. The lightweight lithium metal composite anode based on compression molding according to claim 14, characterized in that, The lithium metal composite negative electrode also includes a current collector, which is prepared using one or more of copper foil, aluminum foil, copper foam, titanium foil, and stainless steel foil.

16. The lightweight lithium metal composite anode based on compression molding according to claim 15, characterized in that, The structure of the lithium metal composite anode is a lightweight intermediate layer | lithium foil layer | current collector.

17. A method for preparing a lightweight lithium metal composite anode based on compression molding, characterized in that, The method for preparing the lightweight lithium metal composite anode based on compression molding according to any one of claims 14 to 16 includes the step of: stacking a lightweight intermediate layer and a lithium foil together and pressing them to obtain a lightweight lithium metal composite anode.

18. The method for preparing a lightweight lithium metal composite anode based on compression molding according to claim 17, characterized in that, The process includes the following steps: First, a lightweight intermediate layer is stacked together with a lithium foil and pressed; then, the resulting composite of the lightweight intermediate layer and lithium foil is stacked together with a current collector and pressed to obtain a lightweight lithium metal composite anode.

19. The method for preparing a lightweight lithium metal composite anode based on compression molding according to claim 17, characterized in that, When preparing the lightweight lithium metal composite anode, the pressing pressure is controlled at 0.2-1.5 tons.

20. The method for preparing a lightweight lithium metal composite anode based on compression molding according to claim 17, characterized in that, The process of preparing the lightweight lithium metal composite anode was carried out under an inert atmosphere.

21. A solid-state battery, characterized in that, It includes the lightweight lithium metal composite anode based on compression molding as described in any one of claims 14 to 16.

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