A battery electrode, a solid-state battery, and a method for preparing the same.

Abstract

This invention discloses a battery electrode, a solid-state battery, and a method for preparing the same, relating to the field of lithium battery technology. The method for preparing the battery electrode includes: forming a flexible electrode film containing a three-dimensional fiber network from a mixture comprising electrode active material, conductive additives, a fibrillable polymer, and a transient additive under mechanical shearing; wherein the transient additive is a solid organic compound with a high saturated vapor pressure at a temperature below 150°C; removing the transient additive from the flexible electrode film to obtain a self-supporting electrode. This preparation method can completely remove the transient additive, reducing the risk of battery electrode cracking during battery use and ensuring the battery's electrochemical performance and cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a battery electrode, a solid-state battery, and a method for preparing the same. Background Technology

[0002] Currently, the manufacturing of lithium-ion battery electrodes primarily relies on wet slurry coating processes. This process typically involves dispersing active materials, conductive agents, and binders in a toxic and expensive organic solvent (such as N-methyl-2-pyrrolidone, NMP) to form a slurry, which is then coated onto a current collector. Following this, a high-energy-consuming drying step removes the solvent, requiring a complex solvent recovery system. This not only significantly increases production costs and equipment footprint but also poses serious environmental problems. Furthermore, during the drying process, solvent evaporation can cause internal stress within the electrode, easily leading to problems such as electrode cracking, uneven distribution of active materials, and binder migration, ultimately impairing the battery's electrochemical performance and cycle life. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a battery electrode, a solid-state battery, and a method for preparing the same. In the process of preparing the battery electrode, by selecting a solid organic compound with a high saturated vapor pressure at a temperature below 150°C as a transient additive, the fibrillation of the fibrillable polymer can be effectively improved, ensuring the self-support of the formed electrode and reducing the risk of electrode collapse and cracking. At the same time, the transient additive can be removed relatively completely during the preparation of the self-supporting electrode, which can ensure the uniform distribution of active materials in the prepared self-supporting electrode and further avoid the risk of cracking of the self-supporting electrode, effectively ensuring the electrochemical performance and cycle life of the battery.

[0004] To achieve the above objectives, in a first aspect, according to embodiments of the present invention, a method for preparing a battery electrode is provided, comprising: Step 1: Under mechanical shearing, a mixture comprising electrode active material, conductive additive, fibrillable polymer and transient additive forms a flexible electrode membrane comprising a three-dimensional fiber network, wherein the transient additive is a solid organic compound having a high saturated vapor pressure at a temperature below 150°C. Step 2: Remove the transient additive from the flexible electrode film to obtain a self-supporting electrode.

[0005] Optionally, the above preparation method further includes: The mixture is obtained by mixing solid electrode active material, solid conductive additive, fibrillable polymer and transient additive using a high-speed shear mixer; Optionally, the fibrillable polymer includes: polytetrafluoroethylene, modified polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, nanocellulose, carboxymethyl cellulose, polyvinyl butyral, and sericin.

[0006] Optionally, step 1 includes: extruding the mixture using a roller press or calender to form a flexible electrode membrane containing a three-dimensional fiber network.

[0007] Optionally, step 2 includes: removing the transient additive from the flexible electrode film by vacuum drying or low-temperature heat treatment.

[0008] Optionally, the transient additive includes one or more of camphor, naphthalene, adamantane, and low molecular weight organic acids.

[0009] Optionally, the transient additive accounts for 1% to 15% of the mass percentage in the mixture.

[0010] Optionally, the porosity of the prepared self-supporting electrode is 40% to 60%.

[0011] Optionally, the thickness of the self-supporting electrode is 10 μm to 300 μm.

[0012] Optionally, the conductive additive includes one or more of the following: conductive carbon black, carbon nanotubes, carbon nanofibers, graphene, graphite, metal powder, and conductive polymers.

[0013] In a second aspect, embodiments of the present invention provide a method for preparing a solid-state battery, comprising: the method for preparing a battery electrode provided in the first aspect embodiment above.

[0014] Optionally, a flexible electrode film corresponding to the positive electrode and a flexible electrode film corresponding to the negative electrode are formed on the two main surfaces of the solid electrolyte, respectively.

[0015] Optionally, a flexible electrode film corresponding to the positive electrode and a flexible electrode film corresponding to the negative electrode are formed on the current collector.

[0016] Thirdly, embodiments of the present invention provide a battery electrode prepared by the preparation method provided in the first aspect of the embodiments described above.

[0017] Fourthly, embodiments of the present invention provide a battery electrode prepared by the preparation method provided in the second aspect of the embodiments described above.

[0018] One embodiment of the above invention has the following advantages or beneficial effects: The method for preparing battery electrodes provided by the embodiments of the present invention, by combining mechanical shearing with a solid organic compound containing a transient additive that has a high saturated vapor pressure at a temperature below 150°C, can effectively enhance the fibrillation of the fibrillable polymer contained in the mixture to form a three-dimensional fiber network structure. This allows the electrode active material and conductive additives to be uniformly embedded in the three-dimensional fiber network structure to form a flexible electrode film. Furthermore, by selecting a solid organic compound with a high saturated vapor pressure at a temperature below 150°C as a transient additive, the transient additives in the flexible electrode film can be removed relatively completely. Moreover, the three-dimensional fiber network structure ensures the formation of a self-supporting electrode, guaranteeing the self-supporting property of the self-supporting electrode. In addition, since the transient additives can be removed as completely as possible during the preparation process, the risk of collapse and cracking of the self-supporting electrode can be reduced or even avoided after the self-supporting electrode is applied to the battery. It can also reduce the migration risk of electrode active materials and conductive additives, ensuring the uniform dispersion of electrode active materials and conductive additives, and effectively guaranteeing the electrochemical performance and cycle life of the battery.

[0019] The further effects of the aforementioned unconventional alternative methods will be explained below in conjunction with specific implementation methods. Attached Figure Description

[0020] The accompanying drawings are provided to better understand the invention and are not intended to unduly limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the main process of a battery electrode preparation method according to an embodiment of the present invention. Detailed Implementation

[0021] To overcome the drawbacks of wet processes mentioned in the background section for lithium-ion batteries, solvent-free dry battery electrode (DBE) technology has emerged. This technology not only eliminates the need for expensive organic solvents but also simplifies the production process, effectively reducing energy consumption and costs while improving environmental friendliness. Specifically, the principle of DBE technology is that under shear force, the binder used to prepare the battery electrode (such as polytetrafluoroethylene) undergoes fibrillation, forming a three-dimensional fibrous network structure. This three-dimensional fibrous network structure can firmly bond the active materials and conductive agents of the battery electrode together, thereby imparting the battery electrode performance. The degree of fibrillation of the binder directly affects the self-support and reliability of the battery electrode. This is because insufficient fibrillation of the binder leads to poor mechanical properties, easy pulverization, and an inability to form a self-supporting structure.

[0022] Research has found that the key to achieving sufficient and uniform fibrillation of the binder lies in effectively transferring externally applied shear forces to the binder. In this process, active materials and conductive additives act as shear force transfer mediators. However, due to the limited shear forces transferred by active materials and conductive additives, the degree of fibrillation of binders in existing battery electrodes remains unsatisfactory.

[0023] To address the aforementioned problems in the existing technology, this invention provides a novel preparation method for battery electrodes. This novel method introduces a transient additive. On one hand, the transient additive can effectively transfer shear force to the fibrillable polymer, enabling the fibrillable polymer to fully fibrillate and form a reliable three-dimensional fiber network structure. On the other hand, the transient additive can be completely removed, avoiding side reactions caused by the residual transient additive and the resulting poor battery performance. Therefore, the preparation scheme provided by this invention can prepare a pure, mechanically strong, and porous battery electrode with a specific microstructure. This battery electrode not only has superior performance but also forms a good synergy with the solid electrolyte, which helps to improve subsequent solid electrolyte infiltration or co-sintering processes.

[0024] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0025] It should be noted that, unless otherwise specified, the embodiments of the present invention and the technical features thereof can be combined with each other.

[0026] Specifically, embodiments of the present invention provide a method for preparing a battery electrode. For example... Figure 1 As shown, the method for preparing this battery electrode may include the following steps: Step S101: Under mechanical shearing, a mixture comprising electrode active material, conductive additive, fibrillable polymer and transient agent forms a flexible electrode membrane comprising a three-dimensional fiber network, wherein the transient agent is a solid organic compound having a high saturated vapor pressure at a temperature below 150°C.

[0027] The electrode active material can be either a positive or negative electrode active material. For the positive electrode active material, it can be NCM (NiCoMn), LFP (LiFePO4), LMO (LiMn2O4), or LRLO (Li-rich Mn-based), and the self-supporting electrode prepared from it is used as the positive electrode of the battery. For the negative electrode active material, it can be graphite, silicon, or SiO2. x Self-supporting electrodes made from materials such as silicon suboxide, Si / C (silicon-carbon composite), or lithium metal are used as the negative electrode in batteries.

[0028] The conductive additive may include one or more of the following: conductive carbon black, carbon nanotubes, carbon nanofibers, graphene, graphite, metal powder, and conductive polymers.

[0029] The fibrillable polymers include one or more of the following: polytetrafluoroethylene (PTFE), modified PTFE, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride (PVDF), nanocellulose, carboxymethyl cellulose, polyvinyl butyral, and sericin. Preferably, the fibrillable polymer is PTFE, which is a low-cost polymer commonly used in batteries, and can effectively control the manufacturing cost of battery electrodes.

[0030] In this context, the three-dimensional fiber network is generally formed by the fibrillation of fibrillable polymers under mechanical shearing. This three-dimensional fiber network can encapsulate electrode active materials and conductive additives, enabling the electrode active materials and conductive additives to be uniformly dispersed in the three-dimensional fiber network. It can also prevent the agglomeration and migration of electrode active materials and conductive additives, thereby improving the reliability and stability of the self-supporting electrode formed subsequently.

[0031] In this context, fibrillation refers to the process where mechanical shearing forces are applied to a fibrillable polymer, causing the surface of the polymer to split into nanoscale microfibers through mechanical friction. These microfibers then interweave to form a three-dimensional fiber network on the surface of the fibrillable polymer.

[0032] Step S102: Remove the transient additives from the flexible electrode film to obtain a self-supporting electrode.

[0033] The battery electrode preparation method provided in this invention, by combining mechanical shearing with a solid organic compound containing a transient additive with a high saturated vapor pressure at a temperature below 150°C, can effectively enhance the fibrillation of the fibrillable polymer contained in the mixture to form a three-dimensional fiber network structure. This allows the electrode active material and conductive additives to be uniformly embedded in the three-dimensional fiber network structure to form a flexible electrode film. Furthermore, by selecting a solid organic compound with a high saturated vapor pressure at a temperature below 150°C as a transient additive, the transient additives in the flexible electrode film can be removed relatively completely. The three-dimensional fiber network structure ensures the formation of a self-supporting electrode, guaranteeing its self-supporting properties. In addition, since the transient additives can be removed as completely as possible during the preparation process, the risk of collapse and cracking of the self-supporting electrode can be reduced or even avoided after it is applied to the battery. It can also reduce the migration risk of electrode active materials and conductive additives, ensuring the uniform dispersion of electrode active materials and conductive additives, and effectively guaranteeing the electrochemical performance and cycle life of the battery.

[0034] In addition, this preparation method promotes more complete fibrillation of the fibrillable polymer by adding transient additives, resulting in a self-supporting electrode with higher compaction density, better mechanical strength, and better interparticle electrical contact, thereby improving the volumetric energy density, rate performance, and cycle stability of the battery.

[0035] Furthermore, the above-mentioned method for preparing battery electrodes has mild preparation conditions, reduces equipment requirements, and completely avoids the use of solvents and energy-intensive drying and recycling steps, significantly reducing production costs and carbon footprint.

[0036] It is worth noting that the mixture in step S101 above can be a directly purchased product or a mixture prepared during the preparation process. Specifically, the preparation method may further include: mixing solid electrode active material, solid conductive additive, fibrillable polymer, and transient additive using a high-speed shear mixer to obtain a mixture. The high-speed shear mixer can break up agglomerated electrode active material and solid conductive additive, ensuring uniform dispersion of these components. Simultaneously, it can induce initial fibrillation of the fibrillable polymer, which helps improve the electrode strength, conductivity, and bonding ability with the current collector of the obtained self-supporting electrode. The rotation speed of the high-speed shear mixer is generally 1000 rpm to 5000 rpm, for example, 1000 rpm, 1500 rpm, 2000 rpm, 3000 rpm, 4000 rpm, or 5000 rpm.

[0037] The preparation process of the mixture is described in detail using NCM811 as the positive electrode active material, carbon nanotubes (CNTs) as the conductive additive, polytetrafluoroethylene (PTFE) powder as the fibrillable polymer, and camphor as the transient additive as an example: NCM811 with a particle size D50 of 12 μm and a particle strength of 20 MPa is selected as the positive electrode active material, carbon nanotubes (CNTs) as the conductive additive, polytetrafluoroethylene (PTFE) powder (particle size 5 μm, fiber aspect ratio 1500:1) as the fibrillable polymer, and camphor as the transient additive; all materials are vacuum dried to remove moisture and impurities and are ready for use. Next, NCM811 and CNTs were added to the mixing chamber according to a specific mass ratio. The mixing speed was set to 1500 rpm for 8 minutes of low-speed premixing to ensure initial mixing. Then, PTFE powder was added, and premixing continued at 1500 rpm for 4 minutes to ensure uniform distribution of the PTFE powder in the mixture. Camphor was then added, and the speed was adjusted to 3000 rpm for 20 minutes of high-speed shear mixing. During the mixing process, the temperature inside the chamber was controlled at 50±5℃ using the equipment's built-in temperature control system to prevent PTFE melting and excessively rapid volatilization of transient additives. CNTs were uniformly coated on the surface of the NCM811 active particles. The CNT-coated NCM811 active particles were tightly entangled and mixed with fibrillated PTFE to form a fluffy, lumpy mixture without lumps. This mixture exhibits elasticity and a fibrous structure.

[0038] The mixing process of the electrode active material and conductive additives employs a relatively low mixing rate to break up agglomeration of the two materials. Mechanical collisions and friction between particles allow the conductive additives to uniformly coat the surface of the electrode active material, initially constructing a uniformly dispersed particle system. This ensures the uniformity of subsequent dispersion while avoiding damage to the particle structure of the electrode active material. The subsequent addition of a fibrillable polymer increases the mixing rate, ensuring the fibrillation of the polymer. The addition of transient additives can reduce the surface tension and frictional resistance between the electrode active material, conductive additives, and fibrillable polymers, thereby reducing particle agglomeration and promoting uniform dispersion of each component. On the other hand, transient additives can wet the surface of the fibrillable polymers, lowering the shear force threshold required for fibrillation, assisting the fibrillable polymers to stretch into fibers more quickly and fully, and improving the integrity and uniformity of the three-dimensional fiber network. Simultaneously, due to the volatile and residue-free nature of transient additives, they can be completely volatilized during or after mixing through vacuum extraction or room temperature standing, leaving no residue in the self-supporting electrode and avoiding negative impacts on subsequent electrode performance and interfacial compatibility with the solid electrolyte. It is worth noting that the mass ratio of the solid electrode active material, solid conductive additives, fibrillable polymers, and transient additives can be selected according to requirements and is not limited here.

[0039] Regardless of whether the preparation method provided in the embodiments of the present invention includes the specific process of obtaining the mixture described above, the specific implementation of step S101 may include: extruding the mixture using a roller press or calender to form a flexible electrode film containing a three-dimensional fiber network. This step can further fibrillate the fibrillable polymer in the mixture, improve the supporting strength of the three-dimensional fiber network structure, and reduce the risk of collapse of the three-dimensional fiber network structure.

[0040] The mechanical extrusion force applied to the mixture by a roller press or calender can form a dense, flexible electrode film and further enhance the fibrillation of the fibrillable polymer. Although the fibrillable polymer in the mixture has initially formed a three-dimensional fiber network, problems such as loose fiber weaving, excessively large network pores, and local fiber breakage still exist. Through the synergistic action of axial pressure (50-200MPa) and shear force applied by the roller press or calender, the fibrillable polymer is further stretched and oriented. The originally loose three-dimensional fiber network becomes more dense and continuous, while filling the pores in the premix, making the contact between the electrode active particles, conductive additives, and fibrillable polymer tighter and improving the interfacial bonding force.

[0041] It is worth noting that the extrusion temperature is generally controlled between 50℃ and 120℃, which can maintain the good ductility of fibrillable polymers (especially polytetrafluoroethylene), avoid the brittle fracture of the three-dimensional fiber network during extrusion, optimize the integrity of the three-dimensional fiber network, and, in addition, the thickness and areal density of the flexible electrode film can be precisely controlled through extrusion, ensuring that the flexible electrode film has a uniform structure and stable performance, and helping to improve the hot-pressing composite of battery electrodes and current collectors, the electronic conduction efficiency of battery electrodes, and the mechanical stability of battery electrodes.

[0042] Specifically, for step S102 above, a specific implementation scheme may include: removing transient additives from the flexible electrode film using vacuum drying or low-temperature heat treatment. The temperature of the low-temperature heat treatment is generally no higher than 80°C, causing the transient additives to sublimate and thus completely remove them from the electrode film. This ensures complete removal of the transient additives while preventing the collapse and breakage of the three-dimensional fiber network.

[0043] More specifically, the transient additives can be selected from one or more of camphor, naphthalene, adamantane, and low molecular weight organic acids. Low molecular weight organic acids generally have 6 or fewer carbon atoms. They possess moderate volatility and surface activity, ensuring they do not evaporate too quickly, resulting in insufficient auxiliary effect, nor remain in the premix and affect subsequent performance. Specifically, selecting the above-mentioned transient additives can, on the one hand, reduce the surface tension and frictional resistance between the electrode active materials and conductive additives and the fibrillable polymer, reducing the probability of particle agglomeration and promoting uniform dispersion of each component; on the other hand, these transient additives can wet the surface of the fibrillable polymer, acting as plasticizers and shear force transmission media, lowering the shear force threshold required for fibrillation of the fibrillable polymer. In particular, the plate-like structures of camphor and naphthalene can embed into the interparticle gaps of the fibrillable polymer, assisting the fibrillable polymer particles to stretch into fibers more quickly and fully under shear force, improving the integrity of the three-dimensional fiber network. In addition, since the above-mentioned transient additives are volatile and leave no residue, they can be completely removed in step S102 and will not remain in the self-supporting electrode, thus avoiding negative impacts on the performance of the self-supporting electrode and the interfacial compatibility between the self-supporting electrode and the solid electrolyte.

[0044] The transient additive comprises 1% to 15% by mass in the mixture. This mass percentage of the transient additive represents its proportion to the total mass of the mixture. By controlling the amount of transient additive added, its auxiliary effect can be ensured, enabling the fibrillable polymer to fully fibrillate and guaranteeing the support of the formed three-dimensional fiber network. Furthermore, it effectively controls the porosity of the formed self-supporting electrode and avoids incomplete volatilization or excessive residue due to excessive transient additive.

[0045] Furthermore, the porosity of the self-supporting electrodes prepared in the above embodiments is 40% to 60%. For example, the porosity of the self-supporting electrode can be 40%, 50%, or 60%, etc. By controlling the porosity of the self-supporting electrode within this range, the self-supporting electrode can balance ion conduction efficiency and electrode mechanical strength, providing sufficient channels for subsequent ion transport while ensuring the self-support of the electrode. In addition, controlling the porosity can also make the contact between the electrode active particles, conductive additives, and three-dimensional fiber network more compact, improving the interfacial bonding force.

[0046] The thickness of the self-supporting electrode ranges from 10 μm to 300 μm. It's worth noting that the thickness of the self-supporting electrode generally differs depending on whether it's used as a positive or negative electrode. Furthermore, the thickness of the self-supporting electrode typically differs depending on whether it's used in a liquid lithium battery or a solid-state lithium battery. The thickness of the self-supporting electrode can be controlled within this range during actual manufacturing. This thickness, in conjunction with the aforementioned porosity range, allows the self-supporting electrode to possess ion conduction efficiency, electrode mechanical strength, and self-supporting properties, providing ample channels for subsequent ion transport while ensuring good self-support.

[0047] It should be noted that the self-supporting electrode prepared in any of the above embodiments can be widely used in various electrode systems. It can be applied to liquid lithium batteries as well as solid-state lithium batteries. Preferably, it is applied to solid-state lithium batteries.

[0048] The above-mentioned method for preparing battery electrodes avoids damage to the electrode active materials and conductive additives caused by high pressure or high temperature throughout the process, thus preserving their electrochemical performance to the greatest extent.

[0049] Furthermore, embodiments of the present invention provide a method for preparing a solid-state battery. Specifically, the method for preparing the solid-state battery may include the method for preparing the battery electrode provided in any of the above embodiments. The solid-state battery prepared in this way can reduce the risk of battery electrode cracking, ensure uniform dispersion of electrode active materials and conductive additives, and improve the electrochemical performance and cycle life of the solid-state battery.

[0050] More specifically, regarding the fabrication method of solid-state batteries, there are two implementation schemes for forming a flexible electrode film containing a three-dimensional fiber network. The first implementation scheme involves forming a flexible electrode film corresponding to the positive electrode and a flexible electrode film corresponding to the negative electrode on the two main surfaces of the solid electrolyte, respectively. The second implementation scheme involves forming a flexible electrode film corresponding to the positive electrode and a flexible electrode film corresponding to the negative electrode on the current collector.

[0051] Furthermore, embodiments of the present invention provide a battery electrode. This battery electrode is prepared by the method for preparing the battery electrode provided in any of the above embodiments.

[0052] Furthermore, embodiments of the present invention provide a solid-state battery. This solid-state battery is prepared by the preparation method of the solid-state battery provided in any of the above embodiments.

[0053] Furthermore, the performance of electrodes prepared by various processes was compared.

[0054] Example 1: A self-supporting electrode was prepared using the preparation method provided in the above examples, in which camphor was introduced into the mixture as a transient additive, PTFE was selected as a fibrillable polymer, conductive carbon black was selected as a conductive additive, and NCM811 was selected as the positive electrode active material.

[0055] Comparative Example 1 differs from Example 1 in that camphor was removed, i.e., camphor was omitted from the mixture.

[0056] Comparative Example 2 differs from Example 1 in that camphor was replaced with ethanol.

[0057] The products prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to scanning electron microscopy (SEM) to detect tensile strength, porosity, transient additive residue content, and SSE-permeable ionic conductivity. The results are shown in Table 1 below. Existing standard testing methods were used for all tests, which will not be elaborated further here. The SSE-permeable ionic conductivity refers to the ionic conductivity of the battery electrode when applied to a solid-state battery.

[0058] Table 1

[0059] As can be seen from Table 1 above, compared with Comparative Example 1, the addition of liquid additive (ethanol) in Comparative Example 2 and the use of solid transient additive in Example 1 both contribute to PTFE fibrillation. In particular, the use of solid transient additive in Example 1 makes the fiber network denser and more uniform. In addition, compared with the use of liquid additive (ethanol) in Comparative Example 2, the use of volatile solid transient additive in the embodiments of the present invention enables the battery electrode to obtain higher mechanical strength while creating higher porosity, and leaves almost no chemical residue. Furthermore, the battery electrode prepared in the embodiments of the present invention allows the solid electrolyte to permeate more effectively, thereby achieving an ionic conductivity that is an order of magnitude higher in the final solid-state battery.

[0060] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a battery electrode, characterized in that, include: Step 1: Under mechanical shearing, a mixture comprising electrode active material, conductive additive, fibrillable polymer and transient additive forms a flexible electrode membrane comprising a three-dimensional fiber network, wherein the transient additive is a solid organic compound having a high saturated vapor pressure at a temperature below 150°C. Step 2: Remove the transient additive from the flexible electrode film to obtain a self-supporting electrode.

2. The preparation method according to claim 1, characterized in that, Also includes: The mixture is obtained by mixing solid electrode active material, solid conductive additive, fibrillable polymer and transient additive using a high-speed shear mixer; Optionally, the fibrillable polymer includes one or more of the following: polytetrafluoroethylene, modified polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, nanocellulose, carboxymethyl cellulose, polyvinyl butyral, and sericin.

3. The preparation method according to claim 1 or 2, characterized in that, Step 1 includes: extruding the mixture using a roller press or calender to form a flexible electrode film containing a three-dimensional fiber network; And / or, Step 2 includes removing the transient additive from the flexible electrode film using vacuum drying or low-temperature heat treatment.

4. The preparation method according to claim 3, characterized in that, The transient additives include one or more of camphor, naphthalene, adamantane, and low molecular weight organic acids. And / or, The transient additive is present in the mixture at a mass percentage of 1% to 15%.

5. The preparation method according to any one of claims 1, 2, and 4, characterized in that, The porosity of the prepared self-supporting electrode is 40%~60%; And / or, The thickness of the self-supporting electrode is 10μm~300μm.

6. The preparation method according to any one of claims 1, 2, and 4, characterized in that, The conductive additives include one or more of the following: conductive carbon black, carbon nanotubes, carbon nanofibers, graphene, graphite, metal powder, and conductive polymers.

7. A method for preparing a solid-state battery, characterized in that, include: The method for preparing the battery electrode according to any one of claims 1 to 6.

8. The preparation method according to claim 7, characterized in that, Flexible electrode films corresponding to the positive electrode and flexible electrode films corresponding to the negative electrode are formed on the two main surfaces of the solid electrolyte, respectively. or, Flexible electrode films corresponding to the positive electrode and flexible electrode films corresponding to the negative electrode are formed on the current collector.

9. A battery electrode, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 6.

10. A solid-state battery, characterized in that, It is prepared by the preparation method described in claim 7 or 8.

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