Composite negative pole piece and solid-state battery

Abstract

The invention discloses a composite negative pole piece and a solid-state battery, and relates to the technical field of new energy batteries. The composite negative pole piece comprises a current collector layer and at least one composite functional layer located on the side face of the current collector layer, the composite functional layer comprises an energy storage layer and an interface layer, the energy storage layer comprises a carbon material, a binding agent, a dispersing agent, an ionic conductor and a metal-philic activation point, and the interface layer comprises a binding agent, an ionic conductor and / or a dielectric reinforcing material. Wherein the carbon material and the binder of the energy storage layer form a three-dimensional porous structure of which the porosity is greater than 80% and the aperture is any one of 1-10 [mu] m through a pore-foaming agent. The pore diameter of the energy storage layer of the composite negative pole piece is uniform, so that metal ions can be deeply, uniformly and compactly deposited in the energy storage layer, and the ion conductor and / or the dielectric reinforcing material of the interface layer further optimizes the ion introduction efficiency of the interface of the electrode material.

Description

A composite negative electrode and a solid-state battery Technical Field

[0001] This invention relates to the field of energy battery technology, specifically to a composite negative electrode and a solid-state battery. Background Technology

[0002] The energy structure transformation places higher comprehensive requirements on secondary batteries. With the rapid expansion of dual-carbon strategies and scenarios such as artificial intelligence, robotics, new energy vehicles, and eVTOL, the energy density, safety, and resource sustainability of traditional lithium-ion batteries are approaching their limits. Specifically, the mass energy density of nickel-cobalt-manganese ternary materials is close to 300Wh / kg. -1 The mass energy density of lithium iron phosphate cathode material is 180 Wh / kg. -1 It is difficult to meet the 400Wh kg requirement. -1 Even 500Wh kg -1 Applications requiring higher energy density.

[0003] In existing technologies, the theoretical specific capacity of lithium metal anodes is 3860 mAh g. -1 Redox potential -3.04V vs. SHE: Lithium metal batteries paired with high-energy cathodes, such as high-nickel cathodes, can achieve ≥400 Wh / kg. -1 With its device-level energy density, lithium metal batteries are considered the preferred choice for the post-lithium battery era. However, lithium metal batteries are prone to phenomena such as lithium pulverization / dead lithium, electrode expansion, and lithium dendrite formation during charging and discharging. Lithium pulverization / dead lithium affects the battery's cycle life, electrode expansion affects battery safety and system reliability, and the gradual growth of lithium dendrites can lead to internal short circuits, battery fires, and explosions, thus limiting the safety and structural stability of secondary batteries.

[0004] Furthermore, the existing three-dimensional porous structures are usually framework structures formed by a single carbon material. Although the framework forms lithium- and sodium-affinity activation points to induce the deposition of lithium and sodium, the porosity of such three-dimensional structures is not high, meaning that the deposition capacity for storage is relatively low. The uneven pore structure leads to uneven distribution of activation points, resulting in poor metal deposition and easy precipitation on the surface of the three-dimensional structure, ultimately affecting the energy storage performance of the battery.

[0005] Therefore, how to provide a three-dimensional porous negative electrode to solve the problems of large volume expansion, low initial efficiency and low cycle life in the existing technology during charge and discharge cycles is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] One objective of the first aspect of this invention is to provide a composite negative electrode sheet that solves the technical problem that the three-dimensional porous structure of the negative electrode sheet in the prior art is only a carbon material skeleton, which easily leads to uneven pore distribution and volume changes during charging and discharging, resulting in reduced battery structural stability.

[0007] Another objective of the first aspect of this invention is to further improve the porosity and structural stability of the energy storage layer.

[0008] The second aspect of the present invention is to provide a solid-state battery having the above-described composite negative electrode.

[0009] According to a first aspect of the present invention, the present invention provides a composite negative electrode sheet, comprising a current collector layer and at least one composite functional layer located on the side of the current collector layer, the composite functional layer comprising an energy storage layer and an interface layer, the energy storage layer comprising a carbon material, a binder, a dispersant, an ion conductor, and metalophilic activation sites, the energy storage layer having a thickness of any value between 10 μm and 60 μm, and the carbon material and the binder of the energy storage layer forming a three-dimensional porous structure with a porosity greater than 80% and a pore size of any value between 1 μm and 10 μm through a pore-forming agent, the interface layer comprising a binder, an ion conductor, and / or The dielectric reinforcement material has an interface layer thickness of any value between 1 μm and 10 μm; wherein the weight ratio of the carbon material, the binder, the dispersant, the pore-forming agent, the ionic conductor, and the metal activation point used to prepare the energy storage layer is any value within the range of (10-40):(10-60):(1-10):(20-90):(5-20):(5-20), and the binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, succinate, polyvinyl alcohol, styrene-butadiene rubber, or polyacrylic acid.

[0010] Optionally, the porogen is at least one of sodium chloride, sodium bromide, potassium chloride, aluminum chloride, calcium chloride, potassium sulfate, potassium phosphate, ammonium bicarbonate, ammonium carbonate, urea, oxalic acid, ammonium oxalate, ammonium hydrogen oxalate, gelatin, glycerol, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, dibutyl phthalate, naphthalene, or camphor, and the particle size distribution D50 of the porogen is any value between 1 μm and 10 μm.

[0011] Optionally, the weight ratio of the adhesive, the ionic conductor, and the dielectric reinforcement material in the interface layer is any one of (20-40):(30-60):(30-60).

[0012] Optionally, the ionic conductor is at least one of the following: oxide ionic conductor solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, gel electrolytes, and organic and inorganic composite solid electrolytes.

[0013] Optionally, the current collector layer is made of at least one of copper, aluminum, nickel, gold, silver, magnesium, zinc, aluminum, tin, platinum, and stainless steel, or an alloy or composite thereof, forming a foil or mesh.

[0014] Optionally, the number of composite functional layers is two, with the two composite functional layers located on both sides of the current collector layer.

[0015] Optionally, the material of the metalophilic activation point is at least one of aluminum, gold, silver, magnesium, zinc, tin, platinum, indium, rubidium, cesium, antimony and their oxides.

[0016] Optionally, the dielectric reinforcing material is at least one of tantalum pentoxide, zirconium oxide, titanium dioxide, yttrium trioxide, lanthanum trioxide, silicon dioxide, niobium pentoxide, barium titanate, strontium titanate, calcium titanate, and lead titanate.

[0017] Optionally, the resistivity of the composite negative electrode is less than or equal to 100 Ω·cm.

[0018] According to a second aspect of the present invention, the present invention also provides a solid-state battery, which is a semi-solid-state battery, a quasi-solid-state battery, or an all-solid-state battery, and the solid-state battery includes the composite negative electrode sheet described in any of the above.

[0019] This invention achieves effective synergy among electron conduction, ion conduction, and metal deposition distribution in the composite negative electrode by designing a layered structure of current collector, energy storage layer, and first interface layer. In particular, the carbon material and binder in the energy storage layer, under the induction and sacrificial effect of the pore-forming agent, jointly construct a three-dimensional porous structure with uniform pore size and porosity greater than 80%, enabling metal ions to be deposited deeply, uniformly, and densely inside the energy storage layer. Furthermore, the ion conductor and dielectric enhancement material in the first interface layer further optimize the ion introduction efficiency of the solid electrolyte. This allows the entire negative electrode system to construct a synergistic functional system of metalophilic attraction in the current collector layer, three-dimensional deposition framework in the energy storage layer, and interface ion regulation in the first interface layer. This significantly improves the cycle stability and safety of the battery, solves the volume expansion problem of lithium metal batteries and sodium metal batteries during charge and discharge, avoids dendrite formation, dead lithium, dead sodium, etc., reduces the interface impedance of the solid battery during charge and discharge, and improves the cycle performance of the solid battery.

[0020] Furthermore, the particle size distribution D50 of the porogen of the present invention is 1μm-10μm, which enables the porogen to have good dispersibility in the negative electrode slurry and form micron-sized pores with uniform size between the carbon material and the binder. This not only generates a three-dimensional porous structure with more concentrated pore size and more uniform pore distribution after drying, ablation, extraction or elution, but also avoids macropore defects caused by excessively large particle size or discontinuous pore structure caused by uneven particle size, thereby giving the energy storage layer higher pore uniformity and structural stability.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] The following description will focus on specific embodiments of the invention by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: FIG1 is a schematic structural diagram of a composite negative electrode sheet according to an embodiment of the invention; FIG2 is a scanning electron microscope image of a composite negative electrode sheet according to an embodiment of the invention; FIG3 is a schematic structural diagram of a composite negative electrode sheet according to another embodiment of the invention; FIG4 is a capacity retention rate-cycle count curve of a solid-state battery according to Embodiment 1 of the invention; FIG5 is a capacity retention rate-cycle count curve of a solid-state battery according to Comparative Example 1 of the invention; FIG6 is a capacity retention rate-cycle count curve of a solid-state battery according to Comparative Example 2 of the invention; FIG7 is a capacity retention rate-cycle count curve of a solid-state battery according to Comparative Example 3 of the invention; FIG8 is a capacity retention rate-cycle count curve of a solid-state battery according to Comparative Example 4 of the invention.

[0023] Reference numerals: 100-composite negative electrode, 10-current collector layer, 20-composite functional layer, 21-energy storage layer, 22-interface layer. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0026] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] Figure 1 is a schematic structural diagram of a composite negative electrode sheet according to an embodiment of the present invention, and Figure 2 is a scanning electron microscope image of a composite negative electrode sheet according to an embodiment of the present invention.

[0029] As shown in Figure 1, the present invention provides a composite negative electrode 100, which includes a current collector layer 10 and at least one composite functional layer 20 located on the side of the current collector layer. The composite functional layer includes an energy storage layer 21 and an interface layer 22. The energy storage layer 21 includes carbon material, binder, dispersant, and metalophilic activation sites. The energy storage layer 21 has a three-dimensional porous structure with a thickness of any value between 10 μm and 60 μm. The interface layer 22 includes an ion conductor, dielectric enhancement material, and binder. The thickness of the interface layer 22 is any value between 1 μm and 10 μm. The weight ratio of carbon material, binder, dispersant and pore-forming agent in the preparation of energy storage layer 21 is any value in (10-40):(10-40):(1-10):(20-90). The carbon material and binder of energy storage layer 21 form a three-dimensional porous structure with a porosity greater than 80% and a pore size of any value between 1μm and 10μm through the pore-forming agent. The binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, succinate, polyvinyl alcohol, styrene-butadiene rubber or polyacrylic acid. Here, the metal at the metalophilic activation point can be at least one of aluminum, gold, silver, magnesium, zinc, tin, platinum, indium, rubidium, cesium, antimony and their oxides. The thickness of the energy storage layer 21 can be 10μm, 20μm, 30μm, 40μm, 50μm or 60μm, or any other value between 10μm and 60μm. The thickness of the interface layer 22 can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm, or any other value between 1μm and 10μm. The carbon material can be at least one of carbon nanotubes, carbon fibers, graphene, and conductive carbon black. The dispersant is polyvinylpyrrolidone. The composite negative electrode 100 can be applied in a solid-state battery 200 or a semi-solid-state battery.

[0030] In this embodiment, by designing a layered structure of current collector layer 10, energy storage layer 21, and interface layer 22, effective synergy among electron conduction, ion conduction, and metal deposition distribution in the composite negative electrode 100 is achieved. In particular, the carbon material and binder in the energy storage layer 21, under the induction and sacrificial effect of the pore-forming agent, jointly construct a three-dimensional porous structure with uniform pore size and porosity greater than 80% (see Figure 2), enabling metal ions to be deposited deeply and uniformly inside the energy storage layer 21. Furthermore, the ion conductor and dielectric enhancement material of the interface layer 22 further optimize the ion introduction efficiency of the solid electrolyte, so that the entire negative electrode system constructs a synergistic functional system of metalophilic attraction of current collector layer 10, three-dimensional deposition framework of energy storage layer 21, and interface ion regulation of interface layer 22. This significantly improves the cycle stability and safety of the battery, solves the volume expansion problem of lithium metal batteries and sodium metal batteries during charging and discharging, avoids dendrite formation, dead lithium, and other phenomena, reduces the interface impedance of solid battery 200 during battery charging and discharging, and improves the cycle performance of solid battery 200.

[0031] In this embodiment, the weight ratio of carbon material, binder, dispersant, pore-forming agent, ionic conductor and metal activation point in energy storage layer 21 is any value of (10-40):(10-40):(1-10):(20-90):(5-20):(5-20), that is, the weight ratio of carbon material, binder, dispersant, pore-forming agent, ionic conductor and metal activation point can be 10:10:5:65:5:5, 10:20:5:55:5:5, 10:30:5:45:5:5, 10:40:5:35:5:5, 10:40:10:30:5:5 or 20:10:10:45:10:5, or it can be any other value of (10-40):(10-40):(1-10):(20-90):(5-20):(5-20). The increased carbon content facilitates the construction of a continuous electron conduction network, significantly reducing the sheet resistance of the energy storage layer 21 and enhancing electron mobility. Simultaneously, the introduction of a certain proportion of ionic conductors, distributed synergistically with the carbon material, can form interconnected ion transport channels within the porous framework, avoiding the limitation of ion diffusion due to excessive carbon material. This achieves a synergistic match between electronic electrodynamics and ionic conductivity. At a higher proportion, the pore-forming agent promotes the formation of a highly porous, interconnected three-dimensional porous structure in the energy storage layer 21, providing a spatial basis for the uniform dispersion of ionic conductors and metal activation points, further shortening the ion diffusion path. Within the aforementioned proportion range, the binder and dispersant ensure stable bonding and uniform distribution of each component without excessively covering the active interface and weakening conductivity and transport performance. The metal activation points provide metalophilic nucleation sites in the porous carbon / ionic conductor composite network, promoting uniform deposition of metal ions and suppressing local current concentration. Therefore, through the synergistic design of the aforementioned multi-component ratios, a three-dimensional porous structure with a porosity greater than 80%, a pore size of 1μm-10μm, uniform pore distribution, continuous electronic pathways, and sufficient mechanical strength is formed. This allows the energy storage layer 21 to maintain excellent electronic conductivity while also ensuring efficient ion transport and structural stability, thereby comprehensively improving the rate performance, cycle stability, and first-cycle efficiency of the composite negative electrode. In other embodiments, excessive carbon material content will reduce the available pore volume and specific capacity utilization, while excessive dispersant content will weaken the mechanical strength and electronic pathway continuity of the electrode.

[0032] In this embodiment, the energy storage layer 21 has a three-dimensional porous structure with a thickness ranging from 10 μm to 60 μm. Through the synergistic effect of the binder and pore-forming agent, it forms a network framework with a porosity greater than 80% and uniform pore size. This provides sufficient space for metal deposition even with a thinner electrode, avoiding the ion transport limitation problem of traditional thick electrodes. The interface layer 22 is configured with a thickness ranging from 1 μm to 10 μm, composed of ion conductors, dielectric reinforcing materials, and binders, providing both ion guidance and interface passivation functions, allowing for more thorough adhesion between the solid electrolyte curing process and the electrode.

[0033] In this embodiment, the pore-forming agent in the energy storage layer 21 provides temporary support vacancies during the coating-drying-removal process, allowing the binder to be uniformly distributed between carbon particles along the pore-forming agent interface during curing, thereby forming a uniform and continuous pore wall framework structure. This structure differs from the random pores generated solely by the accumulation of carbon materials in traditional methods. Instead, it utilizes the mechanism of binder migration and distribution along with the pore-forming agent template. That is, the binder can be uniformly distributed in the energy storage layer 21 along with the pore-forming agent, forming a pore structure with uniform pore distribution when the thick pore-forming agent is removed. This results in a three-dimensional network structure in the energy storage layer 21 with pore sizes of 1μm-10μm and a porosity higher than 80% at the microscale. The three-dimensional network structure provides continuous and deeply accessible deposition space for metal ions while maintaining the mechanical strength of the framework, ensuring that pore wall collapse or localized densification does not occur during repeated charge-discharge cycles.

[0034] In this embodiment, due to the uniformity of pore size and pore distribution, the energy storage layer 21 can guide alkali metal ions such as lithium ions and sodium ions to deposit deep into the three-dimensional framework, rather than being confined to the surface of the energy storage layer 21. Under the combined action of ion conductors and metalophilic activation sites, metal ions are uniformly dispersed into the pores and densely deposited on the framework, significantly reducing the problems of surface deposition, dendrite formation, and uneven growth commonly found in traditional metal anodes. The spatial capacity of the three-dimensional network effectively buffers volume expansion, preventing metal deposition from causing significant local stress concentration, thereby improving cycle life and stability under high areal capacity conditions, achieving an overall performance improvement that is difficult to achieve with a single material system.

[0035] In this embodiment, the top interface layer 22 constructs a stable ion transport interface through ion conductors and / or dielectric reinforcement materials, allowing the solid electrolyte and / or dielectric reinforcement materials to fully penetrate into the upper part of the three-dimensional porous structure during the curing process, achieving close adhesion with the energy storage layer 21 and significantly reducing the solid-solid interface impedance. Simultaneously, because the interface layer 22 blocks electron leakage to the solid electrolyte side, it prevents side reactions or dendrite formation of metal ions on the surface of the energy storage layer 21, thereby improving the safety of the negative electrode interface. The lithium-philic / sodium-philic composite layer of the bottom current collector layer 10 further works synergistically with the porous structure, enabling metal ions to be uniformly deposited from bottom to top, forming a complete three-dimensional deposition mode and creating a synergistic reaction system of electrons, ions, and deposition morphology.

[0036] In this embodiment, the preparation of the energy storage layer 21 also includes a solvent, which is at least one of N-methylpyrrolidone, N,N-dimethylformamide, methyl lactate, propanol, isopropanol, acetone, and deionized water, used to dissolve and disperse the carbon material, binder, dispersant, and pore-forming agent. Here, the pore-forming agent is removed by baking, ablation, extraction, or elution, wherein the baking temperature is below 150°C.

[0037] In this embodiment, the energy storage layer 21 and the interface layer 22 are coated by any one of slot extrusion, transfer, micro-recession or spraying to achieve uniform coating of the energy storage layer 21 or the interface layer 22.

[0038] In a further embodiment, the porogen is at least one of sodium chloride, sodium bromide, potassium chloride, aluminum chloride, calcium chloride, potassium sulfate, potassium phosphate, ammonium bicarbonate, ammonium carbonate, urea, oxalic acid, ammonium oxalate, ammonium hydrogen oxalate, gelatin, glycerol, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, dibutyl phthalate, naphthalene, or camphor, and the particle size distribution D50 of the porogen is any value between 1 μm and 10 μm, that is, the particle size distribution D50 of the porogen is 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 10 μm, or any other value between 1 μm and 10 μm. In this embodiment, the particle size distribution D50 of the porogen is 1μm-3μm, which enables the porogen to have good dispersibility in the active material slurry. It can form micron-sized pores with uniform size between the carbon material and the binder. This not only generates a three-dimensional porous structure with more concentrated pore size and more uniform pore distribution after drying or ablation, but also avoids macropore defects caused by excessively large particle size or discontinuous pore structure caused by uneven particle size. As a result, the energy storage layer 21 has higher porosity and structural stability. At the same time, it is also conducive to the uniform penetration of metal ions into the porous structure and dense deposition at metalophilic activation points, reducing surface accumulation and dendrite formation, improving the cycling stability and safety of the electrode, and increasing the effective utilization rate of the three-dimensional porous structure.

[0039] In this embodiment, the pore-forming agent is at least one of sodium chloride, sodium bromide, potassium chloride, aluminum chloride, calcium chloride, potassium sulfate, potassium phosphate, ammonium bicarbonate, ammonium carbonate, urea, oxalic acid, ammonium oxalate, ammonium hydrogen oxalate, gelatin, glycerol, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, dibutyl phthalate, naphthalene, or camphor. Based on the fact that such pore-forming agents have the characteristics of being easily soluble, easily volatile, or thermally decomposable during the electrode preparation process, they can be completely removed from the carbon material and binder system during slurry drying or subsequent processing. Furthermore, the above-mentioned pore-forming agents and binders have good compatibility and dispersibility, and can form a stable spatial distribution in the slurry system. Thus, after the pore-forming agent is removed, a uniformly distributed and size-controllable micron-sized pore structure is formed in the energy storage layer 21.

[0040] In this embodiment, inorganic salt porogens, namely sodium chloride, sodium bromide, potassium chloride, aluminum chloride, calcium chloride, potassium sulfate, potassium phosphate, ammonium bicarbonate, and ammonium carbonate, can form regular crystalline pores through dissolution, improving pore uniformity. Thermally decomposable porogens, namely urea, oxalic acid, and gelatin, release gases during heating, generating more interconnected channels. Organic small molecule or plasticizing porogens, namely glycerol, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, dibutyl phthalate, naphthalene, or camphor, can improve the fluidity of the binder, allowing the binder to spread uniformly on the pore walls, improving the integrity and mechanical strength of the three-dimensional porous framework. Therefore, the synergistic effect of the above-mentioned porogens and binders can construct a three-dimensional porous structure with uniform pore size, high porosity, and good connectivity within the energy storage layer 21, thereby increasing the penetration depth and uniform deposition ability of metal ions in the channels, effectively inhibiting dendrite formation, and improving the cycle stability and interface safety of the negative electrode sheet.

[0041] In a further embodiment, the weight ratio of the ionic conductor, dielectric reinforcement material, and binder in the interface layer 22 is any value among (20-60):(10-40):(30-60), that is, the weight ratio of the ionic conductor, dielectric reinforcement material, and binder in the interface layer 22 can be 20:20:60, 20:30:50, 20:40:40, 30:10:60, 30:20:50, 30:30:40, 30:40:30, 40:10:50, 40:20:40, 40:30:30, 50:10:40, 50:20:30, or 60:10:30, or any other value among (20-60):(10-40):(30-60). In this embodiment, by using any one of the following weight ratios for the ion conductor, dielectric reinforcement material, and binder in the interface layer 22: (20-60):(10-40):(30-60), the interface layer 22 is ensured to simultaneously possess ion conductivity, dielectric regulation capability, and mechanical stability. This allows the interface layer 22 to maintain a stable structure and performance under different electrochemical environments, thereby further reducing the electrode / electrolyte interface impedance and improving cycle stability and rate performance. Here, the solvent for the interface layer 22 is at least one of N-methylpyrrolidone, N,N-dimethylformamide, methyl lactate, propanol, isopropanol, acetone, and deionized water.

[0042] In this embodiment, when the proportion of ion conductors is in the range of 20-60, the interface layer can be guaranteed to have sufficient lithium / sodium ion transport channels, thereby maintaining a low interface impedance. When the dielectric reinforcement material is varied in the range of 10-40, the dielectric constant and local electric field distribution of the interface layer can be effectively adjusted, enhancing the interface charge homogenization ability and suppressing the formation of interface dendrites or local hot spots. The binder proportion is kept in the range of 30-60, so that the interface layer can maintain structural stability while having mechanical flexibility, preventing pulverization, delamination or cracking during cycling, thereby improving the ion conductivity and dielectric regulation ability of the interface layer 22.

[0043] In a further embodiment, the ion conductor is at least one of oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, gel electrolytes, and organic-inorganic composite solid electrolytes. The dielectric reinforcing material is at least one of tantalum pentoxide, zirconium oxide, titanium dioxide, yttrium trioxide, lanthanum trioxide, silicon dioxide, niobium pentoxide, barium titanate, strontium titanate, calcium titanate, and lead titanate, enabling the interface layer 22 to simultaneously possess excellent ion conductivity and dielectric regulation capabilities. Simultaneously, the introduction of dielectric reinforcing material particles enhances the mechanical support and structural compactness of the interface layer, suppressing microcrack propagation during cycling. Through the combined application of the ion conductor and the dielectric reinforcing material, the interface layer 22 can improve ion transport efficiency while further enhancing interface stability, thereby reducing polarization, increasing cycle life, and improving rate performance.

[0044] In a further embodiment, the viscosity of the interface layer 22 is any value between 50 mPa·s and 300 mPa·s. That is, the viscosity of the interface layer 22 can be 50 mPa·s, 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, or 300 mPa·s, or any other value between 50 mPa·s and 300 mPa·s. This allows the interface layer to have both good fluidity and sufficient film-forming support when coated onto the electrode surface. In this embodiment, when the viscosity is within the above range, the interface layer 22 material can fully wet the microporous structure on the surface of the positive and negative electrode sheets, achieving uniform spreading, thereby improving the adhesion between the interface layer 22 and the energy storage layer 21 and avoiding local accumulation or sagging caused by excessively low viscosity. At the same time, the viscosity is not high enough to affect the self-leveling ability of the material on the electrode surface, which can prevent the formation of microscale breaks or voids in the interface layer and make the interface layer 22 formed by subsequent curing more dense and continuous. This can significantly reduce the interfacial contact impedance between the solid electrolyte and the electrode, improve ion transport efficiency, and enhance the stability of the solid-solid interface and electrochemical cycle life.

[0045] In a further embodiment, the metalophilic activation site is made of at least one of copper, aluminum, nickel, gold, silver, magnesium, zinc, aluminum, tin, platinum, indium, rubidium, cesium, antimony, and their oxides. In this embodiment, the above-mentioned metals and their oxides all have low metal ion nucleation overpotentials or high surface affinity, which can form a large number of uniformly distributed nucleation centers inside the three-dimensional porous structure, thereby inducing lithium, sodium, potassium, and other metal ions to preferentially deposit inside the pores and avoid the formation of dendrites on the outer surface of the pores. At the same time, these metals or metal oxides have good chemical stability and conductivity, which can further improve the continuity of electron transport inside the energy storage layer 21, making the metal deposition process more compact and uniform, reducing local stress concentration, reducing the risk of volume expansion and structural pulverization during cycling, and improving the metal deposition stability and cycle life of the energy storage layer 21.

[0046] In a further embodiment, the mass fraction of the metalophilic activation points is any value between 5% and 30%, meaning the mass fraction of the metalophilic activation points in the energy storage layer 21 can be 5%, 10%, 15%, 20%, 25%, or 30%, or any other value between 5% and 30%. In this embodiment, by setting the mass fraction of the metalophilic activation points to any value between 5% and 30%, the energy storage layer 21 achieves an optimal balance between nucleation density and pore utilization in metal ion deposition behavior. This enables dense and uniform metal deposition, improving deposition reversibility and coulombic efficiency, while also effectively suppressing volume expansion and extending cycle life, further enhancing the stability and rate performance of the negative electrode in the high-energy-density solid-state battery 200.

[0047] In a further embodiment, the current collector layer 10 is made of at least one of copper, aluminum, nickel, gold, silver, magnesium, zinc, aluminum, tin, platinum, and stainless steel, or an alloy or composite thereof, forming a foil or mesh. This material provides stable electronic conductivity and excellent chemical compatibility for different electrochemical systems, enabling the current collector layer 10 to achieve low interfacial resistance, high chemical stability, and excellent electronic conductivity while ensuring mechanical strength. This provides a reliable electronic framework for the uniform deposition of the upper three-dimensional porous energy storage layer 21. Copper, nickel, and stainless steel possess high electrical conductivity and good mechanical strength, maintaining low internal resistance and stable support even under thin foil conditions. Aluminum, magnesium, and their alloys can achieve lighter mass density, suitable for high-energy-density batteries. Inert metals such as gold, silver, and platinum have higher corrosion resistance and interfacial stability, avoiding interfacial side reactions in sulfur- or halogen-containing solid electrolyte systems. The foil structure ensures a continuous current collection path, while the mesh structure further enhances the penetration and bonding area of ​​active materials, improving the overall electronic contact efficiency and adhesion stability of the negative electrode.

[0048] In this embodiment, the thickness of the current collector layer 10 is any value between 4μm and 30μm. That is, the thickness of the current collector layer 10 can be 4μm, 5μm, 10μm, 15μm, 20μm, 25μm or 30μm, or any other value between 4μm and 30μm. This allows the current collector to maintain sufficient electron transport capacity and mechanical support capacity while minimizing its mass and volume ratio, thereby improving the overall energy density of the solid-state battery 200.

[0049] As shown in Figure 3, in a further embodiment, the number of composite functional layers 20 is two, with the two composite functional layers 20 located on opposite sides of the current collector layer 10, i.e., the two composite functional layers 20 are respectively disposed on opposite sides of the current collector layer 10, with the current collector layer 10 located between the two composite functional layers 20, thereby forming a double-sided functionalized composite negative electrode sheet 100 structure. By simultaneously introducing composite functional layers 20 on both sides of the current collector layer 10, the symmetrical construction of the electrochemical reaction interface on both sides of the negative electrode can be achieved while ensuring the continuity of electron conduction, making the current distribution more uniform and effectively reducing the excessively high local current density and polarization phenomenon caused by unilateral load. At the same time, this double-sided structure significantly improves the effective utilization rate and deposition capacity of the negative electrode sheet per unit area, which is beneficial to improving the energy density of the battery under the same space occupation conditions. In addition, the composite functional layers 20 on both sides can form stable contact interfaces with the adjacent interface layer 10 and solid electrolyte, respectively, synergistically improving the interface ion transport conditions, suppressing interface dendrites, and reducing interface impedance, thereby further improving the rate performance, cycle stability, and overall structural reliability of the solid-state battery.

[0050] In a further embodiment, the resistivity of the composite negative electrode sheet is less than or equal to 100 Ω·cm, which can significantly reduce the ohmic polarization of the negative electrode during charging and discharging, enabling electrons to be transported rapidly and uniformly between the current collector layer 10 and the three-dimensional porous energy storage layer. This avoids uneven current density and local overheating caused by excessive local resistance. A suitable electrode resistivity helps maintain the consistency of the potential distribution of the negative electrode sheet structure, allowing metal ions to achieve synchronous nucleation and uniform deposition at the metalophilic activation points, reducing dendrite and volume expansion problems caused by local preferential deposition and growth. At the same time, the uniformly distributed potential characteristics of the three-dimensional structure of the negative electrode sheet can also improve the response capability of the composite negative electrode under high current density conditions, reduce energy loss during high-rate charging and discharging, thereby improving the rate performance, cycle stability, and overall energy utilization efficiency of the battery. Here, the resistance of the composite negative electrode sheet is obtained by testing with a four-probe resistivity meter.

[0051] The present invention also provides a solid-state battery including the above-described composite negative electrode 100, wherein the solid-state battery is a semi-solid-state battery, a quasi-solid-state battery, or an all-solid-state battery. The composite negative electrode 100 will not be described in detail here.

[0052] The technical solution of this application will be further described below with reference to specific embodiments.

[0053] In some embodiments, the composite negative electrode 100 includes a current collector layer 10 and at least one composite functional layer 20 located on the side of the current collector layer. The composite functional layer includes an energy storage layer 21 and an interface layer 22. The energy storage layer 21 includes carbon material, binder, dispersant, pore-forming agent, and metalophilic activation sites. The energy storage layer 21 is a three-dimensional porous structure with a thickness of any value between 10 μm and 60 μm. The interface layer 22 includes an ion conductor, a dielectric enhancement material, and a binder. The thickness of the interface layer 22 is any value between 1 μm and 10 μm. The weight ratio of carbon material, binder, dispersant, and pore-forming agent required to prepare the energy storage layer 21 is (10-40):(10-40):(1- 10): Any value in (20-90), the carbon material and binder of the energy storage layer 21 form a three-dimensional porous structure with a porosity greater than 80% and a pore size of any value in 1μm-10μm through a pore-forming agent, the binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, succinic acid, polyvinyl alcohol, styrene-butadiene rubber or polyacrylic acid, the particle size distribution D50 of the pore-forming agent is any value in 1μm-3μm, and the weight ratio of the binder, ion conductor and dielectric reinforcement material of the interface layer 22 is any value in (20-40):(30-60):(30-60).

[0054] Example 1: The composite negative electrode 100 includes a current collector layer 10 and a composite functional layer 20 located on one side of the current collector layer 10. The composite functional layer includes an energy storage layer 21 and an interface layer 22. The energy storage layer 21 includes carbon material, binder, dispersant, pore-forming agent, and metal-philic activation points. The energy storage layer 21 has a three-dimensional porous structure with a thickness of 30 μm. The interface layer 22 includes an ion conductor, a dielectric enhancement material, and a binder. The interface layer 22 has a thickness of 5 μm. The weight ratio of carbon material, binder, dispersant, pore-forming agent, ion conductor, and metal activation points in the energy storage layer 21 is 20:30:5:30:10:5. The carbon material and binder in the energy storage layer 21 form a three-dimensional porous structure with a porosity greater than 90% and a pore size of 3 μm through the pore-forming agent. The binder is PVDF, and the particle size distribution D50 of the pore-forming agent is 2 μm.

[0055] Example 2 The only difference between Example 2 and Example 1 is that the weight ratio of carbon material, binder, dispersant, pore-forming agent, ionic conductor and metal activation point in the energy storage layer 21 is 20:20:5:42.5:5:7.5.

[0056] Example 3 differs from Example 1 only in that the weight ratio of carbon material, binder, dispersant, pore-forming agent, ionic conductor and metal activation point in the energy storage layer 21 is 10:30:5:42.5:7.5:5.

[0057] Example 4 differs from Example 1 only in that the weight ratio of carbon material, binder, dispersant, pore-forming agent, ionic conductor and metal activation point required to prepare energy storage layer 21 is 30:10:5:42.5:7.5:5.

[0058] Comparative Example 1 differs from Example 1 only in that it does not have an interface layer 22.

[0059] The only difference between Comparative Example 2 and Example 1 is that no pore-forming agent was added when preparing the energy storage layer 22.

[0060] Comparative Example 3 differs from Example 1 only in that the energy storage layer 21 does not include a dispersant.

[0061] Comparative Example 4 differs from Example 1 only in that the interface layer 22 does not include an ion conductor.

[0062] The only difference between Comparative Example 5 and Example 1 is that the weight ratio of carbon material, binder, dispersant and pore-forming agent required to prepare energy storage layer 21 is 5:35:5:42.5:7.5:5.

[0063] The only difference between Comparative Example 6 and Example 1 is that the weight ratio of carbon material, binder, dispersant and pore-forming agent required to prepare energy storage layer 21 is 35:5:5:42.5:7.5:5.

[0064] Figure 4 is a capacity retention rate-cycle count curve of the solid-state battery according to Embodiment 1 of the present invention; Figure 5 is a capacity retention rate-cycle count curve of the solid-state battery according to Comparative Example 1 of the present invention; Figure 6 is a capacity retention rate-cycle count curve of the solid-state battery according to Comparative Example 2 of the present invention; Figure 7 is a capacity retention rate-cycle count curve of the solid-state battery according to Comparative Example 3 of the present invention; and Figure 8 is a capacity retention rate-cycle count curve of the solid-state battery according to Comparative Example 4 of the present invention.

[0065] First, the battery performance of the batteries composed of composite negative electrode sheets in Example 1 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1 and Figures 4-8.

[0066] As shown in Table 1 and Figures 4-8, Example 1, with a complete interface layer 22, significantly outperformed Comparative Example 1 (without interface layer 22) in terms of first-cycle efficiency (90.8%) and 500-cycle capacity retention (80.2%), and Comparative Example 4 (without interface layer 22, 87.5% first-cycle efficiency, 62.1% 500-cycle capacity retention) in terms of both first-cycle efficiency (90.8%) and 500-cycle capacity retention (80.2%). This indicates that the presence of interface layer 22, especially the design containing ion conductors, significantly improves interfacial ion conductivity and overall electrode stability. Comparative Example 2 (without pore-forming agent) showed slightly lower performance than Example 1 (first-cycle efficiency 88.9%, 500-cycle capacity retention 69.8%), suggesting that the pore-forming agent helps the energy storage layer 21 form a uniform, high-porosity three-dimensional structure, optimizing the uniformity of metal ion deposition. Comparative Example 3 (without dispersant) showed little change in performance, indicating that the dispersant has a limited direct impact on battery performance but is beneficial for material dispersion and pore structure uniformity during the preparation process.

[0067] Next, the battery performance of the batteries composed of composite negative electrode sheets in Examples 2-4 and Comparative Examples 5-6 was tested, and the test results are shown in Table 2.

[0068] As shown in Table 2, the weight ratio of carbon materials, binders, dispersants, and pore-forming agents in the energy storage layer 21 has a significant impact on battery performance. The energy storage layers 21 with reasonable proportions in Examples 2-4 exhibited good performance in first-cycle efficiency (89.2%-91.1%) and capacity retention after 300 cycles (84.1%-84.9%). However, in Comparative Examples 5-6, when the proportion of carbon materials or binders was too low or too high, both the first-cycle efficiency (85.4%-86.3%) and capacity retention (68.6%-69.8%) decreased. This indicates that the rationality of the component proportions in the energy storage layer 21 is crucial for the balance of electron and ion conduction and the stability of the three-dimensional porous structure. The uniform pore structure formed by the pore-forming agent ensures uniform deposition of metal ions within the energy storage layer 21, reducing dendrite formation and local expansion, thereby improving the cycle stability and energy utilization efficiency of the composite negative electrode 100. This demonstrates the synergistic effect of the components and pore structure of the energy storage layer 21.

[0069] In summary, the battery performance of the composite negative electrode 100 mainly depends on the setting of the interface layer 22, the composition ratio of the energy storage layer 21, and the role of the pore-forming agent. Specifically, the presence of the interface layer 22, especially the design containing ion conductors, can significantly improve ion conductivity, reduce polarization, and enhance first-cycle efficiency and cycle stability. The reasonable ratio of carbon materials, binders, and ion conductors in the energy storage layer 21 ensures the balance of electron and ion transport, affecting capacity utilization and cycle performance. The pore-forming agent, by forming a uniform, high-porosity three-dimensional porous structure and lithium-affinity activation points, helps metal ions to be uniformly deposited in the energy storage layer 21, reducing dendrite growth and electrode expansion, thereby improving the battery's rate performance, cycle stability, and overall energy utilization efficiency. The synergistic effect of the energy storage layer 21, the interface layer, and the pore-forming agent achieves the optimized performance, long lifespan, and safety of the composite negative electrode 100 in solid-state batteries.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A composite negative electrode sheet, characterized in that, The device includes a current collector layer and at least one composite functional layer located on the side of the current collector layer. The composite functional layer includes an energy storage layer and an interface layer. The energy storage layer includes carbon material, a binder, a dispersant, an ion conductor, and metalophilic activation sites. The energy storage layer has a thickness of any value between 10 μm and 60 μm. The carbon material and the binder of the energy storage layer are combined with a pore-forming agent to form a three-dimensional porous structure with a porosity greater than 80% and a pore size of any value between 1 μm and 10 μm. The interface layer includes a binder, an ion conductor, and / or a dielectric reinforcing material. The thickness is any value between 1 μm and 10 μm; wherein, the weight ratio of the carbon material, the binder, the dispersant, the pore-forming agent, the ionic conductor and the metal activation point used to prepare the energy storage layer is any value among (10-40):(10-60):(1-10):(20-90):(5-20):(5-20), and the binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, succinate, polyvinyl alcohol, styrene-butadiene rubber or polyacrylic acid.

2. The composite negative electrode sheet according to claim 1, characterized in that, The porogen is at least one of sodium chloride, sodium bromide, potassium chloride, aluminum chloride, calcium chloride, potassium sulfate, potassium phosphate, ammonium bicarbonate, ammonium carbonate, urea, oxalic acid, ammonium oxalate, ammonium hydrogen oxalate, gelatin, glycerol, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, dibutyl phthalate, naphthalene, or camphor, and the particle size distribution D50 of the porogen is any value between 1 μm and 10 μm.

3. The composite negative electrode sheet according to claim 2, characterized in that, The weight ratio of the adhesive, the ionic conductor, and the dielectric reinforcement material in the interface layer is any one of (20-40):(30-60):(30-60).

4. The composite negative electrode sheet according to claim 3, characterized in that, The ionic conductor is at least one of the following: oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, gel electrolytes, and organic and inorganic composite solid electrolytes.

5. The composite negative electrode sheet according to claim 4, characterized in that, The current collector layer is made of at least one of copper, aluminum, nickel, gold, silver, magnesium, zinc, aluminum, tin, platinum, and stainless steel, or an alloy or composite thereof, forming a foil or mesh.

6. The composite negative electrode sheet according to claim 5, characterized in that, The number of composite functional layers is two, and the two composite functional layers are located on both sides of the current collector layer.

7. The composite negative electrode sheet according to claim 6, characterized in that, The material of the metalophilic activation point is at least one of aluminum, gold, silver, magnesium, zinc, tin, platinum, indium, rubidium, cesium, antimony and their oxides.

8. The composite negative electrode sheet according to any one of claims 1-7, characterized in that, The dielectric enhancement material is at least one of tantalum pentoxide, zirconium oxide, titanium dioxide, yttrium trioxide, lanthanum trioxide, silicon dioxide, niobium pentoxide, barium titanate, strontium titanate, calcium titanate, and lead titanate.

9. The composite negative electrode sheet according to claim 8, characterized in that, The resistivity of the composite negative electrode is less than or equal to 100 Ω·cm.

10. A solid-state battery, wherein the solid-state battery is a semi-solid-state battery, a quasi-solid-state battery, or an all-solid-state battery, characterized in that, The solid-state battery includes the composite negative electrode sheet according to any one of claims 1-9.

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