A semi-solid battery positive electrode and a preparation method thereof, and a semi-solid battery

Abstract

This invention provides a semi-solid-state battery cathode and its preparation method, as well as a semi-solid-state battery. The semi-solid-state battery cathode includes: a current collector and an active material layer disposed on at least one side of the current collector; the active material layer includes at least two sub-active material layers; each active material layer has micropores, and the porosity of each sub-active material layer increases along the thickness direction of the semi-solid-state battery cathode away from the current collector. Based on the semi-solid-state battery cathode of this invention, the problems of low ion transport efficiency, high interfacial impedance, and unstable electrode structure in existing semi-solid-state battery cathodes are solved.

Description

Technical Field

[0001] This invention relates to the field of semi-solid-state battery technology, and more specifically, to a semi-solid-state battery cathode and its preparation method, and a semi-solid-state battery. Background Technology

[0002] In recent years, with the rapid development of electric vehicles and energy storage technologies, the demand for higher energy density and safer battery technologies has become increasingly urgent. Semi-solid batteries, as a technology path between traditional liquid lithium-ion batteries and all-solid batteries, have received widespread attention due to their combination of high ionic conductivity and high safety. In semi-solid batteries, the positive electrode usually includes solid components (active materials, solid electrolytes, etc.) and a small amount of liquid or gel electrolyte, and the amount of liquid electrolyte is much less than that of traditional liquid lithium-ion batteries. It still faces the following problems: (1) High solid-solid interface impedance inside the electrode. In the electrode of a semi-solid battery, active materials, solid electrolytes, and other components exist in solid form. There is a high ion migration resistance at the contact surface between these solid components, thereby increasing the interface impedance. (2) Poor electrode structure stability. For high-capacity materials, the huge volume effect during charging and discharging can easily lead to the pulverization and peeling of active materials, causing damage to the electrode structure and resulting in rapid decay of battery capacity and other performance.

[0003] Therefore, it is of great significance to develop a semi-solid-state battery electrode with good ion transport performance, low interface impedance and stable electrode structure. Summary of the Invention

[0004] The main objective of this invention is to provide a semi-solid battery cathode and its preparation method, as well as a semi-solid battery, to solve the problems of low ion transport efficiency, high interface impedance, and unstable electrode structure in the prior art.

[0005] To achieve the above objective, according to a first aspect of the present invention, a semi-solid-state battery positive electrode is provided, comprising: a current collector and an active material layer disposed on at least one side of the current collector; the active material layer comprises at least two sub-active material layers; each active material layer has micropores, and the porosity of each sub-active material layer increases along the thickness direction of the semi-solid-state battery positive electrode away from the current collector.

[0006] Furthermore, along the thickness direction of the positive electrode of the semi-solid battery, the porosity of the sub-active material layer closest to the current collector is 8% to 37%, and the porosity of the sub-active material layer farthest from the current collector is 38% to 65%.

[0007] Furthermore, the porosity difference between any two adjacent sub-active material layers is 5% to 18%.

[0008] Furthermore, the active material layer includes active materials, additives, solid electrolytes, and gel electrolytes. The gel electrolytes include a three-dimensional gel network formed by in-situ polymerization of polymeric monomers, lithium salts, and initiators. The active materials, additives, and solid electrolytes are dispersed in the three-dimensional gel network.

[0009] Furthermore, the active material includes one or two of ternary materials and lithium iron phosphate.

[0010] Furthermore, the polymerizing monomers include one or more of pentaerythritol tetraacrylate, methyl methacrylate, and ethylene glycol dimethacrylate.

[0011] Furthermore, the lithium salt includes one or more of LiPF6, LiTFSI, and LiBOB.

[0012] Furthermore, the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and tert-butyl peroxide.

[0013] Furthermore, the solid electrolyte includes one or more of the following: sulfide solid electrolyte, oxide solid electrolyte, or phosphate solid electrolyte.

[0014] Furthermore, the mass ratio of active material to additive is (92-98):(2-8).

[0015] Furthermore, the mass ratio of solid electrolyte to gel electrolyte is 100:(5-15), and the gel electrolyte comprises a three-dimensional gel network formed by in-situ polymerization of polymeric monomers, lithium salts and initiators in a mass ratio of 10:(0.5-1.5):(1-3).

[0016] Furthermore, the additives include conductive agents, which include one or more of Super P, carbon nanotubes, graphene, or conductive carbon black.

[0017] Furthermore, the additives include binders, which include one or more of polyvinylidene fluoride, polyethylene oxide, or polyvinyl alcohol.

[0018] Furthermore, the additives include lithium supplements, which include one or more of lithium nickelate, lithium oxalate, and lithium nitride.

[0019] According to a second aspect of the present invention, a method for preparing a semi-solid-state battery cathode is provided, comprising the following steps:

[0020] Active material raw material layers with different contents of pore-forming agent are sequentially laminated onto the current collector in order of increasing pore-forming agent content in the thickness direction away from the current collector, thus forming active material raw material layers with different contents of pore-forming agent. Then, the pore-forming agent is allowed to form micropores to obtain the semi-solid battery positive electrode.

[0021] Further, the active material raw material layer includes active materials, additives, a solid electrolyte, and a gel electrolyte precursor; the pore-forming agent includes one or more of ammonium bicarbonate, ammonium carbonate, and urea; the gel electrolyte precursor includes a polymer monomer, a lithium salt, and an initiator; the active material raw material layer with different contents of pore-forming agent is prepared by the following steps: mixing the active materials and additives to obtain a first mixture; mixing different masses of pore-forming agent with the gel electrolyte precursor to form gel electrolyte precursors with different contents of pore-forming agent; mixing the solid electrolyte with the gel electrolyte precursors with different contents of pore-forming agent to form gel electrolyte precursors with different contents of pore-forming agent. Semi-solid material; a first mixture is laid to form several first mixture layers, each first mixture layer being laid in layers along the thickness direction of the semi-solid battery positive electrode away from the current collector; semi-solid materials with different contents of pore-forming agents are laid sequentially on a first mixture layer in order of increasing pore-forming agent content in the thickness direction of the semi-solid battery positive electrode away from the current collector, and active material raw material layers with different contents of pore-forming agents are formed by lamination; the step of forming micropores by pore-forming agents includes heat-treating the active material raw material layers with different contents of pore-forming agents to decompose the pore-forming agents to form micropores, and in-situ polymerization of gel electrolyte precursor.

[0022] Furthermore, by weight percentage, along the thickness direction of the semi-solid battery cathode, the content of pore-forming agent in the active material raw material layer closest to the current collector is 4% to 6%, and the content of pore-forming agent in the active material raw material layer farthest from the current collector is 1% to 3%.

[0023] Furthermore, by weight percentage, the difference in the content of pore-forming agent in any two adjacent active material raw material layers is 1.5% to 3%.

[0024] Furthermore, the lamination pressure ranges from 4 MPa to 10 MPa.

[0025] Furthermore, the lamination temperature is 40°C to 50°C.

[0026] Furthermore, the heat treatment is carried out at a temperature of 60°C to 80°C for a time of 4 to 12 hours.

[0027] Furthermore, the lamination process employs gradient calendering, where the lamination pressure for each active material raw material layer decreases along the thickness direction of the semi-solid battery cathode, away from the current collector.

[0028] Furthermore, along the thickness direction away from the positive electrode of the semi-solid battery, the pressure of the active material raw material layer closest to the current collector is 6 MPa to 8 MPa, and the porosity of the active material raw material layer farthest from the current collector is 4 MPa to 5 MPa.

[0029] Furthermore, the pressure difference between the laminations of two adjacent active material raw material layers ranges from 0.5 MPa to 2 MPa.

[0030] According to a third aspect of the present invention, a semi-solid-state battery is provided, comprising the above-described semi-solid-state battery positive electrode or a semi-solid-state battery positive electrode prepared according to the above-described method for preparing the semi-solid-state battery positive electrode.

[0031] The present invention provides a semi-solid-state battery cathode comprising at least two sub-active material layers with increasing porosity along the electrode thickness direction away from the current collector. This gradient porosity structure significantly optimizes ion transport paths, improves the uniformity and efficiency of electrolyte (or gel electrolyte) distribution, thereby reducing solid-solid interface impedance within the electrode and enhancing the battery's rate performance and energy density. The sub-active material layer closer to the current collector has lower porosity, providing sufficient electronic conductivity and mechanical support, increasing electrode structural stability, strengthening the bond between the electrode and the current collector, and reducing the risk of active material peeling. The sub-active material layer further away from the current collector has higher porosity, providing more ample wetting space for the electrolyte, optimizing the ion transport environment, facilitating electrolyte (or gel electrolyte) wetting and ion transport, while mitigating volume changes in the active material during charge and discharge, reducing particle pulverization, and improving cycle stability. Based on the semi-solid-state battery cathode of the present invention, ion transport paths can be optimized, interface impedance reduced, electrode structural stability increased, and active material volume changes buffered, thereby improving the battery's rate performance, energy density, and cycle stability. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 The image shows a SEM image of a cross section parallel to the thickness direction of the positive electrode of the semi-solid battery in Embodiment 1 of the present invention. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] As described in the background section, in the prior art, the positive electrode of semi-solid-state batteries suffers from problems such as low ion transport efficiency, high interface impedance, and unstable electrode structure.

[0036] To address the aforementioned problems, according to a first aspect of the present invention, a semi-solid-state battery positive electrode is provided, comprising: a current collector and an active material layer disposed on at least one side of the current collector; the active material layer comprises at least two sub-active material layers; each active material layer has micropores, and the porosity of each sub-active material layer increases along the thickness direction of the semi-solid-state battery positive electrode away from the current collector.

[0037] Based on the technical solution of this invention, the positive electrode of a semi-solid-state battery includes at least two sub-active material layers with increasing porosity along the electrode thickness direction away from the current collector. This gradient pore structure can significantly optimize the ion transport path, improve the uniformity and efficiency of electrolyte (or gel electrolyte) distribution, thereby reducing the solid-solid interface impedance inside the electrode and improving the rate performance and energy density of the battery. The sub-active material layer closer to the current collector has lower porosity, which can provide sufficient electronic conductivity network and mechanical support, increase the stability of the electrode structure, enhance the bonding force between the electrode and the current collector, and reduce the risk of active material peeling. The sub-active material layer farther from the current collector has higher porosity, providing more sufficient wetting space for the electrolyte, optimizing the ion transport environment, facilitating electrolyte (or gel electrolyte) wetting and ion transport, while mitigating the volume change of the active material during charge and discharge, reducing particle pulverization, and improving cycle stability. Based on the semi-solid-state battery positive electrode of this invention, the ion transport path can be optimized, the interface impedance reduced, the electrode structure stability increased, and the volume change of the active material buffered, thereby improving the rate performance, energy density, and cycle stability of the battery.

[0038] In some embodiments, along the thickness direction of the semi-solid-state battery cathode, the porosity of the sub-active material layer closest to the current collector is 8% to 37%, and the porosity of the sub-active material layer farthest from the current collector is 38% to 65%. This gradient porosity structure effectively balances the electron conduction and ion transport requirements within the electrode. By maintaining a lower porosity in the sub-active material layer near the current collector, close contact and continuity of the electron path between the electrode and the current collector are ensured. Conversely, increased porosity in the sub-active material layer far from the current collector promotes electrolyte penetration and rapid ion transport. This not only reduces the impedance at the electrode-electrolyte interface, enhancing the battery's rate performance and energy density, but also buffers the volume changes of the high-capacity active material during charge and discharge through the aforementioned porosity gradient, significantly improving the electrode's cycle stability and overall structural integrity. Preferably, along the thickness direction of the semi-solid-state battery cathode, the porosity of the sub-active material layer closest to the current collector is 28% to 36%, and the porosity of the sub-active material layer farthest from the current collector is 45% to 55%.

[0039] In some embodiments, the porosity difference between any two adjacent sub-active material layers is 5% to 18%. Controlling the porosity difference between adjacent sub-active material layers within the range of 5% to 18% helps to form a gradual permeability and conductivity path, optimizes ion transport paths, reduces solid-solid interface impedance within the electrode, and facilitates uniform distribution and deep wetting of the electrolyte. This improves the efficiency and kinetic performance of the electrochemical reaction, and also effectively buffers the volume changes of the active material during cycling, reducing the resulting internal stress concentration and electrode structure damage, thereby enhancing the battery's rate performance, energy density, and cycle stability.

[0040] In some embodiments, the active material layer includes active materials, additives, a solid electrolyte, and a gel electrolyte. The gel electrolyte comprises a three-dimensional gel network formed by in-situ polymerization of monomers, lithium salts, and an initiator. The active materials, additives, and solid electrolyte are dispersed within the three-dimensional gel network. The active material layer includes active materials, additives, a solid electrolyte, and a three-dimensional gel network formed by in-situ polymerization of monomers, lithium salts, and an initiator. The active material, as the main component of the electrochemical reaction, carries the storage and release of energy. Additives, such as conductive agents and binders, can optimize electron conduction paths and the bonding forces between materials. The solid electrolyte constructs the framework for ion transport. The three-dimensional gel network formed by in-situ polymerization fills the spaces between the active materials, additives, and solid electrolyte, allowing the active materials, additives, and solid electrolyte to be dispersed within the three-dimensional gel network. This improves the interfacial compatibility between the active materials, solid electrolyte, and other solid components, facilitating rapid ion transport, reducing interfacial impedance, and improving the battery's rate performance and energy density. Furthermore, the three-dimensional gel network provides a buffer space for volume changes in the active material, reducing particle pulverization and extending cycle life.

[0041] In some embodiments, the active material includes one or two of ternary materials and lithium iron phosphate, but is not limited to these materials. Ternary materials are considered important for improving battery energy density due to their high specific capacity. By introducing ternary materials into the active material layer, especially into the high-porosity sub-active material layer, the high energy storage characteristics of ternary materials can be fully utilized, thereby improving the overall energy density of the battery. Lithium iron phosphate is known for its excellent cycle stability and long service life, maintaining stable performance even under high-current charge-discharge conditions. By using lithium iron phosphate in the active material layer, especially in the sub-active material layer near the current collector, the stability of the electrode and the cycle performance of the battery can be enhanced, reducing capacity decay during long-term charge-discharge processes.

[0042] In some embodiments, the polymerizing monomers include one or more of pentaerythritol tetraacrylate, methyl methacrylate, and ethylene glycol dimethacrylate, but are not limited to these materials. By using pentaerythritol tetraacrylate, methyl methacrylate, and ethylene glycol dimethacrylate as polymerizing monomers, a gel electrolyte with a highly ionicly conductive network can be formed, which not only increases the contact area between the electrolyte and the active material, but also promotes faster and more uniform lithium-ion transport, significantly improving the rate performance of the electrode.

[0043] In some embodiments, the lithium salt includes one or more of LiPF6, LiTFSI, and LiBOB, but is not limited to these materials. Using LiPF6, LiTFSI, or LiBOB as the lithium salt helps to improve the stable ionic conductivity and chemical stability of the electrode over a wide temperature range.

[0044] In some embodiments, the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and tert-butyl peroxide, but is not limited to these materials. Using azobisisobutyronitrile, benzoyl peroxide, or tert-butyl peroxide as initiators allows for more precise control of the polymerization rate and extent, achieving uniform formation of the gel electrolyte and further improving the cycle stability and safety of the battery.

[0045] In some embodiments, the solid electrolyte includes one or more of sulfide solid electrolytes, oxide solid electrolytes, or phosphate solid electrolytes, but is not limited to these materials. The selection of solid electrolytes includes sulfide, oxide, and phosphate-based materials, such as Li. 10 GeP2S 12 Li7La3Zr2O 12 Li 1.4 Al 0.4 Ti 1.6 (PO4)3, these materials have high ionic conductivity and good chemical stability, and can effectively construct stable ion transport pathways inside the electrode.

[0046] In some embodiments, the mass ratio of active material to additive is (92-98):(2-8). Setting the mass ratio of active material to additive to (92-98):(2-8) ensures a sufficiently high active material loading, thereby improving the energy density of the battery.

[0047] In some embodiments, the mass ratio of solid electrolyte to gel electrolyte is 100:(5-15), and the gel electrolyte includes a three-dimensional gel network formed by in-situ polymerization of polymeric monomers, lithium salts and initiators in a mass ratio of 10:(0.5-1.5):(1-3), which helps to achieve a balanced distribution of solid and gel electrolytes inside the electrode, ensuring both high ion conduction efficiency and improved battery safety performance; preferably, the mass ratio of solid electrolyte to gel electrolyte is 100:(7-10).

[0048] In some embodiments, the additives include conductive agents, which include, but are not limited to, one or more of Super P, carbon nanotubes, graphene, or conductive carbon black. The conductive agent enhances the electronic conductivity within the electrode, ensuring efficient current transfer between active material particles, thereby improving the electrochemical performance of the electrode. Using Super P, carbon nanotubes, graphene, or conductive carbon black as conductive agents can significantly reduce the electron transport impedance within the electrode and improve the rate performance of the battery.

[0049] In some embodiments, the additive includes a binder, which includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), or polyvinyl alcohol (PVA). The binder in the additive, such as PVDF, PEO, or PVA, effectively maintains the mechanical connection between the active material and the current collector, ensuring the structural stability of the electrode during cycling, thereby extending the battery's lifespan.

[0050] In some embodiments, the additive includes a lithium replenisher, which includes one or more of lithium nickelate, lithium oxalate, and lithium nitride, but is not limited to these materials. The addition of a lithium replenisher, such as lithium nickelate, lithium oxalate, or lithium nitride, can compensate for the loss of lithium ions during the charging and discharging process of the battery, especially the irreversible capacity loss during the first charge and discharge, thereby improving the battery's initial efficiency and energy density.

[0051] According to a second aspect of the present invention, a method for preparing a semi-solid-state battery cathode is provided, comprising the following steps:

[0052] Active material raw material layers with different contents of pore-forming agent are sequentially laminated onto the current collector in order of increasing pore-forming agent content in the thickness direction away from the current collector, thus forming active material raw material layers with different contents of pore-forming agent. Then, the pore-forming agent is allowed to form micropores to obtain the semi-solid battery positive electrode.

[0053] Based on the technical solution of this invention, a method for preparing a semi-solid-state battery cathode is provided. By controlling the pore-forming agent content to increase incrementally in the cathode thickness direction away from the current collector, the cathode is sequentially laminated onto the current collector to form an active material raw material layer. Subsequently, the pore-forming agent decomposes to form micropores, resulting in a semi-solid-state battery cathode. The pore-forming agent content gradient is key to achieving porosity distribution. A lower pore-forming agent content closer to the current collector enhances electron conduction pathways and mechanical strength, while a higher pore-forming agent content further away from the current collector effectively increases electrolyte (or gel electrolyte) wetting and ion transport channels. Furthermore, lamination ensures tight bonding within and between each layer. By controlling the pore-forming agent content, a porosity gradient is achieved, and combined with lamination, solid-solid interface impedance is reduced, optimizing ion transport pathways, especially improving the rate performance of the battery at high current densities. Simultaneously, the gradient pore structure provides buffer space for volume changes of the active material during charge and discharge, reducing interparticle stress. Lamination ensures tight bonding between each layer, thereby improving the cycle stability of the electrode and the reliability of the overall structure.

[0054] In some embodiments, the active material raw material layer includes an active material, an additive, a solid electrolyte, and a gel electrolyte precursor; the pore-forming agent includes one or more of ammonium bicarbonate, ammonium carbonate, and urea; the gel electrolyte precursor includes a polymer monomer, a lithium salt, and an initiator; the active material raw material layer with different contents of pore-forming agent is prepared by the following steps: mixing the active material and the additive to obtain a first mixture; mixing different masses of pore-forming agent with the gel electrolyte precursor to form a gel electrolyte precursor with different contents of pore-forming agent; mixing the solid electrolyte with the gel electrolyte precursor with different contents of pore-forming agent to form a pore-forming agent with different contents. The process involves: a semi-solid material containing a pore-forming agent; laying a first mixture to form several first mixture layers, each first mixture layer being laid in layers along the thickness direction of the semi-solid battery positive electrode away from the current collector; sequentially laying semi-solid materials with different contents of pore-forming agent onto a first mixture layer in order of increasing pore-forming agent content along the thickness direction of the semi-solid battery positive electrode away from the current collector, and forming active material raw material layers with different contents of pore-forming agent by lamination; and the step of forming micropores by the pore-forming agent includes: subjecting the active material raw material layers with different contents of pore-forming agent to heat treatment to decompose the pore-forming agent and form micropores, and in-situ polymerizing the gel electrolyte precursor.

[0055] Based on the technical solution of this invention, a pore-forming agent is mixed with a gel electrolyte precursor to form a gel electrolyte precursor with different contents of pore-forming agent, thereby introducing varying porosity at different depths of the electrode. A solid electrolyte is combined with the aforementioned gel electrolyte precursor to form a semi-solid material with different contents of pore-forming agent. A first mixture is laid to form several first mixture layers, and then semi-solid materials with different contents of pore-forming agent are laid on top of the first mixture layers and laminated to form active material raw material layers. During heat treatment, the pore-forming agent, such as ammonium bicarbonate, decomposes to generate gas, forming micropores within the electrode. Simultaneously, the gel electrolyte precursor solidifies, thereby constructing a structure with a gradient from low porosity to high porosity. This structural design allows the electrolyte to preferentially wet the high-porosity region of the electrode surface, promoting effective ion transport, while ensuring good electronic conductivity and mechanical stability of the electrode layer near the current collector. The gradient pore structure reduces the solid-solid interface impedance inside the battery, alleviates the volume expansion effect of high-capacity active materials during charge and discharge, and significantly improves the cycle stability and energy density of the battery. Furthermore, in-situ polymerization of gel electrolytes further enhances the interfacial contact between materials (e.g., active materials, solid electrolytes), reduces interfacial impedance within the battery, and improves the battery's rate performance and energy density. In addition, the in-situ formed three-dimensional gel network provides a buffer space for volume changes in active materials, reducing particle pulverization and extending cycle life, achieving synergistic optimization of high rate performance and long cycle life. By controlling the content of pore-forming agents to achieve a gradient change in porosity, combined with in-situ polymerization and lamination, problems such as poor ion transport, high interfacial impedance, and poor structural stability within the cathode of traditional semi-solid-state batteries are effectively solved, significantly improving the overall performance of the battery.

[0056] In some embodiments, by weight percentage, the pore-forming agent content in the active material layer closest to the current collector is 4% to 6% in the thickness direction of the semi-solid-state battery cathode, while the pore-forming agent content in the active material layer furthest from the current collector is 1% to 3%. Along the thickness direction of the semi-solid-state battery cathode, the pore-forming agent content in each sub-active material layer increases from near the current collector to away from it. By controlling the pore-forming agent content, differentiated porosity can be formed at different depths of the electrode, thereby optimizing the overall pore structure of the electrode. This optimizes both electron conduction (maintaining a high solid packing density in the region near the current collector) and electrolyte wetting and ion transport (providing higher porosity in the region away from the current collector). This design effectively balances electron conduction and ion migration pathways, reduces the interfacial impedance of the entire battery system, improves rate performance and cycle stability, and prevents particle pulverization and flaking through the buffering effect of the high-porosity layer on the volume changes of the active material, thus extending the battery's lifespan.

[0057] In some embodiments, the difference in pore-forming agent content between any two adjacent active material layers, by weight percentage, is 1.5% to 3%. By fine-tuning the pore-forming agent content, the pore formation of each sub-active material layer during heating can be precisely controlled, thereby ensuring the continuity of the porosity gradient from the current collector interface to the electrode surface. This gradual porosity distribution not only promotes uniform electrolyte wetting and optimization of ion transport pathways but also enhances the mechanical stability of the electrode, effectively balances electronic conductivity and ionic conductivity, and improves the overall electrochemical performance of the battery.

[0058] In some embodiments, the lamination pressure ranges from 4 MPa to 10 MPa. Under these pressure conditions, sufficient compression can be achieved to form a stable electron conduction network while reducing excessive pore compression, which is beneficial for improving the structural integrity of the increasing porosity from the current collector towards the electrode surface.

[0059] In some embodiments, the lamination temperature is between 40°C and 50°C. Setting the lamination temperature between 40°C and 50°C helps to ensure uniform contact between materials within and between the active material raw material layers, while also ensuring the physical and chemical stability of the materials during the lamination process, thereby improving the uniformity of the internal structure of the electrode and the stability of the active materials.

[0060] In some embodiments, the heat treatment is performed at a temperature of 60°C to 80°C for 4 to 12 hours. These heat treatment conditions facilitate in-situ polymerization, promote the uniform distribution of the gel electrolyte network within the electrode, and promote the orderly decomposition of the pore-forming agent, generating a finer and more uniformly distributed pore structure. This provides an efficient pathway for ion transport and significantly reduces solid-solid interface resistance.

[0061] In some embodiments, lamination employs gradient calendering, where the lamination pressure for each active material layer decreases along the thickness direction of the semi-solid-state battery cathode, away from the current collector. This controlled gradient calendering pressure helps manage the porosity of each active material layer, increasing porosity from the current collector towards the electrode surface. This optimizes the electrolyte wetting path and ion transport efficiency, reducing electron-ion conduction impedance in the semi-solid-state battery. Simultaneously, gradient calendering contributes to a more stable electrode structure, reducing material damage and pore structure disruption caused by excessive local pressure. It also promotes a strong bond between the active material and the current collector, close contact between materials in each active material layer, and uniform dispersion of active materials within the gel electrolyte precursor, enhancing the overall mechanical strength and cycle stability of the electrode. Furthermore, gradient calendering results in a more balanced stress distribution within the electrode, effectively mitigating volume changes in the active material during charge and discharge, reducing particle shedding and pulverization, and further improving the battery's cycle life and safety. By controlling the content of pore-forming agent to achieve a gradient change in porosity, combined with in-situ polymerization and gradient calendering, the ion transport environment inside the electrode is further optimized, enhancing the structural stability and mechanical strength of the electrode, and significantly improving the electrochemical performance and lifespan of the semi-solid-state battery.

[0062] In some embodiments, along the thickness direction away from the positive electrode of the semi-solid-state battery, the pressure of the active material raw material layer closest to the current collector is 6 MPa to 8 MPa, and the porosity of the active material raw material layer farthest from the current collector is 4 MPa to 5 MPa. This helps to precisely control the porosity of each active material raw material layer, construct a more stable electrode structure, effectively alleviate the volume change of the active material during charging and discharging, thereby optimizing the ion transport path, reducing interface impedance, increasing electrode structure stability, and improving the rate performance, energy density, and cycle stability of the battery. Preferably, along the thickness direction away from the positive electrode of the semi-solid-state battery, the pressure of the active material raw material layer closest to the current collector is 6 MPa, and the porosity of the active material raw material layer farthest from the current collector is 4 MPa. Preferably, the lamination pressure difference between two adjacent active material raw material layers is in the range of 0.5 MPa to 2 MPa, which helps to optimize the ion transport path, reduce interface impedance, increase electrode structure stability, and improve the rate performance, energy density, and cycle stability of the battery.

[0063] According to a third aspect of the present invention, a semi-solid-state battery is provided, comprising the above-described semi-solid-state battery cathode or a semi-solid-state battery cathode prepared according to the above-described method for preparing a semi-solid-state battery cathode. Employing a porosity gradient along the thickness direction in the semi-solid-state battery electrode optimizes ion transport paths, reduces interfacial impedance, increases electrode structural stability, and buffers volume changes in the active material, thereby contributing to improved rate performance, energy density, and cycle stability of the battery.

[0064] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0065] Example 1

[0066] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0067] Step 1: Dry-mix lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF in a mass ratio of 93:2:2:1:2 to obtain the first mixture.

[0068] Step 2: Take two equal portions of the first mixture and label them as the first active slurry and the second active slurry, respectively.

[0069] Step 3: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor.

[0070] Step four: Take two equal masses of gel electrolyte precursors, designated as the first gel electrolyte precursor and the second gel electrolyte precursor, respectively. Disperse ammonium bicarbonate in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, Li... 10 GeP2S 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li 10 GeP2S 12 The mass ratio of the first gel electrolyte precursor to the second gel electrolyte precursor is 100:8. Taking the sum of the masses of the active material slurry and the first pore-forming agent slurry as 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%. Ammonium bicarbonate is dispersed in the second gel electrolyte precursor to obtain a gel electrolyte precursor containing the pore-forming agent. Then, Li... 10 GeP2S 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the second pore-forming agent slurry. In the second pore-forming agent slurry, Li... 10 GeP2S 12 The mass ratio of the active material slurry to the second gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%, the pore-forming agent content in the second pore-forming agent slurry is 2%.

[0071] Step 5: First active slurry is laid on aluminum foil to form a first active slurry layer. First pore-forming agent slurry is then laid on top of the first active slurry layer to form a first pore-forming agent slurry layer, resulting in an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is then rolled at 45°C and 7.0 MPa. Second active slurry is then laid on the rolled first raw material layer to form a second active slurry layer. Second pore-forming agent slurry is then laid on top of the second active slurry layer to obtain an active material raw material layer with the second pore-forming agent content, denoted as the second raw material layer. The second raw material layer is then rolled at 45°C and 5.0 MPa to form a green electrode with a total thickness of 180 μm.

[0072] Step 6: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0073] Figure 1 This is a SEM image of a cross-section parallel to the thickness direction of the positive electrode of the semi-solid-state battery prepared in Example 1. Figure 1 Possible value, along the direction away from the aluminum foil (the aluminum foil is located) Figure 1 The thickness of the semi-solid battery cathode (at the bottom) increases, and the porosity increases significantly.

[0074] Example 2

[0075] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0076] Step 1: Dry-mix lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF in a mass ratio of 93:2:2:1:2 to obtain the first mixture.

[0077] Step 2: Take two equal portions of the first mixture and label them as the first active slurry and the second active slurry, respectively.

[0078] Step 3: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor.

[0079] Step four: Take two equal masses of gel electrolyte precursors, designated as the first gel electrolyte precursor and the second gel electrolyte precursor, respectively. Disperse ammonium bicarbonate in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, Li... 10 GeP2S 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li 10 GeP2S 12The mass ratio of the first gel electrolyte precursor to the second gel electrolyte precursor is 100:8. Taking the sum of the masses of the active material slurry and the first pore-forming agent slurry as 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%. Ammonium bicarbonate is dispersed in the second gel electrolyte precursor to obtain a gel electrolyte precursor containing the pore-forming agent. Then, Li... 10 GeP2S 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the second pore-forming agent slurry. In the second pore-forming agent slurry, Li... 10 GeP2S 12 The mass ratio of the active material slurry to the second gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%, the pore-forming agent content in the second pore-forming agent slurry is 2%.

[0080] Step 5: First, a first active slurry is laid on aluminum foil to form a first active slurry layer. Then, a first pore-forming agent slurry is laid on top of the first active slurry layer to form a first pore-forming agent slurry layer, resulting in an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is then rolled at 45°C and 6 MPa. Next, a second active slurry is laid on the rolled first raw material layer to form a second active slurry layer. Then, a second pore-forming agent slurry is laid on top of the second active slurry layer, resulting in an active material raw material layer with the second pore-forming agent content, denoted as the second raw material layer. The second raw material layer is then rolled at 45°C and 4 MPa to form a green electrode with a total thickness of 180 μm.

[0081] Step 6: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0082] Example 3

[0083] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0084] Step 1: Dry-mix lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF in a mass ratio of 93:2:2:1:2 to obtain the first mixture.

[0085] Step 2: Take two equal portions of the first mixture and label them as the first active slurry and the second active slurry, respectively.

[0086] Step 3: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor.

[0087] Step four: Take two equal masses of gel electrolyte precursors, designated as the first gel electrolyte precursor and the second gel electrolyte precursor, respectively. Disperse ammonium bicarbonate into the first gel electrolyte precursor containing a pore-forming agent, then... (The sentence is incomplete and requires further context to be fully translated.) 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li7La3Zr2O 12 The mass ratio of the first gel electrolyte precursor to the second gel electrolyte precursor is 100:8. Taking the sum of the masses of the active material slurry and the first pore-forming agent slurry as 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%. Ammonium bicarbonate is dispersed in the second gel electrolyte precursor to obtain a gel electrolyte precursor containing the pore-forming agent. Then, Li7La3Zr2O... 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the second pore-forming agent slurry. In the second pore-forming agent slurry, Li7La3Zr2O... 12 The mass ratio of the active material slurry to the second gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%, the pore-forming agent content in the second pore-forming agent slurry is 2%.

[0088] Step 5: First, a first active slurry is laid on aluminum foil to form a first active slurry layer. Then, a first pore-forming agent slurry is laid on top of the first active slurry layer to form a first pore-forming agent slurry layer, resulting in an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is then rolled at 45°C and 7.0 MPa. Next, a second active slurry is laid on the rolled first raw material layer to form a second active slurry layer. Then, a second pore-forming agent slurry is laid on top of the second active slurry layer, resulting in an active material raw material layer with the second pore-forming agent content, denoted as the second raw material layer. The second raw material layer is then rolled at 45°C and 5.0 MPa to form a green electrode with a total thickness of 180 μm.

[0089] Step 6: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0090] Example 4

[0091] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0092] Step 1: Dry-mix lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF in a mass ratio of 93:2:2:1:2 to obtain the first mixture.

[0093] Step 2: Take two equal portions of the first mixture and label them as the first active slurry and the second active slurry, respectively.

[0094] Step 3: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor.

[0095] Step four: Take two equal masses of gel electrolyte precursors, designated as the first gel electrolyte precursor and the second gel electrolyte precursor, respectively. Disperse ammonium bicarbonate in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, use Li7La3Zr2O... 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li7La3Zr2O 12 The mass ratio of the first gel electrolyte precursor to the second gel electrolyte precursor is 100:8. Taking the sum of the masses of the active material slurry and the first pore-forming agent slurry as 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%. Ammonium bicarbonate is dispersed in the second gel electrolyte precursor to obtain a gel electrolyte precursor containing the pore-forming agent. Then, Li7La3Zr2O... 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the second pore-forming agent slurry. In the second pore-forming agent slurry, Li7La3Zr2O... 12 The mass ratio of the active material slurry to the second gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%, the pore-forming agent content in the second pore-forming agent slurry is 2%.

[0096] Step 5: First, the first active slurry is laid on aluminum foil to form a first active slurry layer. Then, the first pore-forming agent slurry is laid on top of the first active slurry layer to form a first pore-forming agent slurry layer, resulting in an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is then rolled at 45°C and 6 MPa. Second, the second active slurry is laid on the rolled first raw material layer to form a second active slurry layer. Then, the second pore-forming agent slurry is laid on top of the second active slurry layer, resulting in an active material raw material layer with the second pore-forming agent content, denoted as the second raw material layer. The second raw material layer is then rolled at 45°C and 4 MPa to form a green electrode with a total thickness of 180 μm.

[0097] Step 6: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0098] Example 5

[0099] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0100] Step 1: Dry-mix lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF in a mass ratio of 93:2:2:1:2 to obtain the first mixture.

[0101] Step 2: Take two equal portions of the first mixture and label them as the first active slurry and the second active slurry, respectively.

[0102] Step 3: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor.

[0103] Step four: Take two equal masses of gel electrolyte precursors, designated as the first gel electrolyte precursor and the second gel electrolyte precursor, respectively. Disperse ammonium bicarbonate in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, Li... 1.4 Al 0.4 Ti 1.6 (PO4)3 is dispersed in a gel electrolyte precursor containing a pore-forming agent to form a semi-solid slurry, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li 1.4 Al 0.4 Ti 1.6 The mass ratio of (PO4)3 to the first gel electrolyte precursor is 100:8. Taking the sum of the masses of the active material slurry and the first pore-forming agent slurry as 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%. Ammonium bicarbonate is dispersed in the second gel electrolyte precursor to obtain a gel electrolyte precursor containing the pore-forming agent. Then, Li... 1.4 Al 0.4 Ti 1.6 (PO4)3 dispersed in a gel electrolyte precursor containing a pore-forming agent to form a semi-solid slurry, denoted as the second pore-forming agent slurry. In the second pore-forming agent slurry, Li... 1.4 Al 0.4 Ti 1.6 The mass ratio of (PO4)3 to the second gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%, the pore-forming agent content in the second pore-forming agent slurry is 2%.

[0104] Step 5: First, a first active slurry is laid on aluminum foil to form a first active slurry layer. Then, a first pore-forming agent slurry is laid on top of the first active slurry layer to form a first pore-forming agent slurry layer, resulting in an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is then rolled at 45°C and 7.0 MPa. Next, a second active slurry is laid on the rolled first raw material layer to form a second active slurry layer. Then, a second pore-forming agent slurry is laid on top of the second active slurry layer, resulting in an active material raw material layer with the second pore-forming agent content, denoted as the second raw material layer. The second raw material layer is then rolled at 45°C and 5.0 MPa to form a green electrode with a total thickness of 180 μm.

[0105] Step 6: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0106] Example 6

[0107] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0108] Step 1: Dry-mix lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF in a mass ratio of 93:2:2:1:2 to obtain the first mixture.

[0109] Step 2: Take two equal portions of the first mixture and label them as the first active slurry and the second active slurry, respectively.

[0110] Step 3: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor.

[0111] Step four: Take two equal masses of gel electrolyte precursors, denoted as the first gel electrolyte precursor and the second gel electrolyte precursor, respectively. Disperse ammonium bicarbonate in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then: Li 1.4 Al 0.4 Ti 1.6 (PO4)3 is dispersed in a gel electrolyte precursor containing a pore-forming agent to form a semi-solid slurry, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li 1.4 Al 0.4 Ti 1.6The mass ratio of (PO4)3 to the first gel electrolyte precursor is 100:8. Taking the sum of the masses of the active material slurry and the first pore-forming agent slurry as 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%. Ammonium bicarbonate is dispersed in the second gel electrolyte precursor to obtain a gel electrolyte precursor containing the pore-forming agent. Then: Li 1.4 Al 0.4 Ti 1.6 (PO4)3 is dispersed in a gel electrolyte precursor containing a pore-forming agent to form a semi-solid slurry, denoted as the second pore-forming agent slurry. In the second pore-forming agent slurry, Li... 1.4 Al 0.4 Ti 1.6 The mass ratio of (PO4)3 to the second gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%, the pore-forming agent content in the second pore-forming agent slurry is 2%.

[0112] Step 5: First, a first active slurry is laid on aluminum foil to form a first active slurry layer. Then, a first pore-forming agent slurry is laid on top of the first active slurry layer to form a first pore-forming agent slurry layer, resulting in an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is then rolled at 45°C and 6 MPa. Next, a second active slurry is laid on the rolled first raw material layer to form a second active slurry layer. Then, a second pore-forming agent slurry is laid on top of the second active slurry layer, resulting in an active material raw material layer with the second pore-forming agent content, denoted as the second raw material layer. The second raw material layer is then rolled at 45°C and 4 MPa to form a green electrode with a total thickness of 180 μm.

[0113] Step 6: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0114] Example 7

[0115] The only difference between this and Example 2 is that, in step four, the pore-forming agent content in the first pore-forming agent slurry is 4%, with the sum of the masses of the active material slurry and the first pore-forming agent slurry being 100%.

[0116] Example 8

[0117] The only difference between this and Example 2 is that, in step four, the pore-forming agent content in the first pore-forming agent slurry is 1%, with the sum of the masses of the active material slurry and the first pore-forming agent slurry being 100%.

[0118] Example 9

[0119] The only difference between this and Example 2 is that, in step four, the pore-forming agent content in the second pore-forming agent slurry is 3%, with the sum of the masses of the active material slurry and the second pore-forming agent slurry being 100%.

[0120] Example 10

[0121] The only difference between this and Example 2 is that, in step four, Li... 10 GeP2S 12 The mass ratio of Li to the first gel electrolyte precursor is 100:5; in the second pore-forming agent slurry, Li 10 GeP2S 12 The mass ratio of the precursor to the second gel electrolyte is 100:5.

[0122] Example 11

[0123] The only difference between this example and Example 2 is that, in step five, the preparation of the first and second raw material layers did not employ a layered laying method. Step five is detailed below:

[0124] The first active slurry and the first pore-forming agent slurry are mixed and laid on aluminum foil to form a first raw material layer. The first raw material layer is then rolled at 45°C and 6 MPa. The second active slurry and the second pore-forming agent slurry are mixed and laid on the first raw material layer to form a second raw material layer. The second raw material layer is then rolled at 45°C and 4 MPa to form a green electrode with a total thickness of 180 μm.

[0125] Comparative Example 1

[0126] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0127] Step 1: Lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF are dry-mixed in a mass ratio of 93:2:2:1:2 to obtain the first mixture, which is denoted as the first active slurry.

[0128] Step two: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor, denoted as the first gel electrolyte precursor. Ammonium bicarbonate is dispersed in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, Li… 10 GeP2S 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li 10 GeP2S 12The mass ratio of the active material slurry to the first gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the first pore-forming agent slurry being 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%.

[0129] Step 3: The first active slurry is laid on the aluminum foil to form the first active slurry layer, and the first pore-forming agent slurry is laid on the first active slurry layer to form the first pore-forming agent slurry layer, thus obtaining an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is rolled at 45°C and 7.0 MPa to form a green electrode with a total thickness of 180 μm.

[0130] Step four: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0131] Comparative Example 2

[0132] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0133] Step 1: Lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF are dry-mixed in a mass ratio of 93:2:2:1:2 to obtain the first mixture, which is denoted as the first active slurry.

[0134] Step two: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor, denoted as the first gel electrolyte precursor. Ammonium bicarbonate is dispersed in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, Li7La3Zr2O... 12 A semi-solid slurry is formed by dispersing a gel electrolyte precursor containing a pore-forming agent, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li7La3Zr2O 12 The mass ratio of the active material slurry to the first gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the first pore-forming agent slurry being 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%.

[0135] Step 3: The first active slurry is laid on the aluminum foil to form the first active slurry layer, and the first pore-forming agent slurry is laid on the first active slurry layer to form the first pore-forming agent slurry layer, thus obtaining an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is rolled at 45°C and 7.0 MPa to form a green electrode with a total thickness of 180 μm.

[0136] Step four: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0137] Comparative Example 3

[0138] A method for preparing a semi-solid-state battery cathode includes the following steps:

[0139] Step 1: Lithium nickel manganese cobalt oxide, lithium nickel oxide, Super P, carbon nanotubes and PVDF are dry-mixed in a mass ratio of 93:2:2:1:2 to obtain the first mixture, which is denoted as the first active slurry.

[0140] Step two: Pentaerythritol tetraacrylate, LiPF6, and azobisisobutyronitrile are mixed in a mass ratio of 10:1:2 to obtain a gel electrolyte precursor. Ammonium bicarbonate is dispersed in the first gel electrolyte precursor to obtain a gel electrolyte precursor containing a pore-forming agent. Then, Li… 1.4 Al 0.4 Ti 1.6 (PO4)3 is dispersed in a gel electrolyte precursor containing a pore-forming agent to form a semi-solid slurry, denoted as the first pore-forming agent slurry; wherein, in the first pore-forming agent slurry, Li 1.4 Al 0.4 Ti 1.6 The mass ratio of (PO4)3 to the first gel electrolyte precursor is 100:8. Based on the sum of the masses of the active material slurry and the first pore-forming agent slurry being 100%, the pore-forming agent content in the first pore-forming agent slurry is 5%.

[0141] Step 3: The first active slurry is laid on the aluminum foil to form the first active slurry layer, and the first pore-forming agent slurry is laid on the first active slurry layer to form the first pore-forming agent slurry layer, thus obtaining an active material raw material layer with the first pore-forming agent content, denoted as the first raw material layer. The first raw material layer is rolled at 45°C and 7.0 MPa to form a green electrode with a total thickness of 180 μm.

[0142] Step four: Place the green electrode in a rotatable curing chamber and heat-treat it at 70°C for 6 hours to decompose ammonium bicarbonate in the raw material layer to form micropores and to polymerize the gel electrolyte precursor in situ to obtain the positive electrode of the semi-solid battery.

[0143] Performance testing

[0144] I. Porosity Testing: Scanning electron microscopy (SEM) was used to characterize the cross-section of the semi-solid-state battery cathode parallel to its thickness direction. The pore size of the micropores in the inner layer cross-section was measured using PhineSpeed ​​Microscopy pore size measurement software, and the pore size distribution information of the inner layer cross-section was obtained through statistical analysis. Similarly, the pore size of the micropores in the outer layer cross-section was measured using the same software, and the pore size distribution information of the outer layer cross-section was obtained through statistical analysis. Based on the pore size distribution information of the inner layer cross-section, the total area S1 of the micropores in the inner layer cross-section was calculated, and the total area S2 of the micropores in the inner layer cross-section was calculated based on the pore size distribution. Then, the inner layer porosity and outer layer porosity were calculated as follows: Inner layer porosity = S1 / S2. i ×100%, outer layer porosity = S² / S x ×100% of S i S is the area of ​​the inner cross-section. x denoted as the area of ​​the outer layer cross-section. Along the thickness direction of the positive electrode of the semi-solid battery, the sub-active material layer closest to the current collector is denoted as the inner layer, and the sub-active material layer farthest from the current collector is denoted as the outer layer.

[0145] II. Tests were performed on the semi-solid-state battery cathodes prepared in the examples and comparative examples.

[0146] 1. Using the above-mentioned semi-solid-state battery as the positive electrode, assemble a semi-solid-state battery. The specific steps are as follows:

[0147] (1) The negative electrode active material is a mixture of graphite negative electrode material and silicon-oxygen negative electrode material with a mass ratio of 94.5:5.5. The conductive agent is carbon black, and the binder is a mixture of styrene-butadiene rubber and sodium carboxymethyl cellulose with a mass ratio of 1:1. The negative electrode active material, conductive agent and binder are dispersed in water at a mass ratio of 95.5:1.5:3 to obtain a uniformly dispersed negative electrode slurry. The negative electrode slurry is uniformly coated on copper foil with a coating surface density of 17 mg / cm². Subsequently, the coated copper foil is baked, rolled, slit and punched to obtain the negative electrode sheet.

[0148] (2) A pouch cell was prepared by stacking the positive electrode, separator, and negative electrode. In a low-humidity environment (moisture content below 40 ppm), the electrolyte (Shenzhen Xinzhoubang Technology Co., Ltd., LBC435A50) was injected into the pouch cell. After injection, the cell was left to stand for 24 hours, and then formed and aged at high temperature to obtain a semi-solid cell. The separator was a boehmite / PE / boehmite composite separator with thicknesses of 4 μm, 9 μm, and 4 μm for each layer. The formation conditions were: 0.02C constant current charging for 30 min, standing for 5 min, 0.05C constant current charging for 30 min, standing for 5 min, 0.1C constant current charging for 120 min, standing for 5 min, and 0.2C constant current charging for 30 min. The high-temperature aging conditions were: 50℃ for 12 h.

[0149] 2. The semi-solid-state battery was subjected to the following electrochemical performance tests:

[0150] (1) Initial charge-discharge efficiency test: Charge the battery at a 1C rate to the cutoff voltage of 4.35V, and then discharge it at a 1C rate to the voltage of 2.5V to perform the first charge-discharge test and calculate the initial charge-discharge efficiency. Initial charge-discharge efficiency = First discharge capacity / First charge capacity × 100%.

[0151] (2) 1C rate discharge capacity and cycle capacity retention rate test: The battery was charged at a 1C rate to the cutoff voltage of 4.35V, and then discharged at a 1C rate to 2.5V, and the charge-discharge cycle was continuously performed. The initial discharge capacity, the discharge capacity at the 100th charge-discharge cycle (recorded as the 100th discharge capacity), and the discharge capacity at the 500th charge-discharge cycle (recorded as the 500th discharge capacity) were recorded, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were calculated. Among them, the capacity retention rate after 100 cycles = 100th discharge capacity / initial discharge capacity × 100%, and the capacity retention rate after 500 cycles = 500th discharge capacity / initial discharge capacity × 100%, with the initial discharge capacity being taken as the 1C rate discharge capacity. The 1C rate discharge capacity, the capacity retention rate after 100 cycles, and the capacity retention rate after 500 cycles are shown in Table 1.

[0152] (3) Interface impedance test: The battery pack was placed in a constant temperature chamber at 25°C for 1 hour to allow the temperature of the solid electrolyte inside the battery to reach 25°C. The battery was connected to an electrochemical workstation and a 10mV AC voltage disturbance was applied. The constant voltage AC impedance was measured in the range of 0.01Hz to 1MHz to obtain the interface impedance. The results are shown in Table 1.

[0153] Table 1 shows the inner layer porosity, outer layer porosity, and electrochemical performance test results of the semi-solid-state battery cathodes prepared in the comparative examples and embodiments.

[0154]

[0155] Note: "-" in the table indicates that there is no corresponding layer.

[0156] As shown in Table 1, the batteries prepared using the gradient pore electrodes prepared in Examples 1 to 11 have high 1C rate discharge capacity, capacity retention rate after 100 cycles, capacity retention rate after 500 cycles, energy density, and low interface impedance. The batteries have excellent rate performance, cycle stability, and energy density, and also have good first charge and discharge efficiency.

[0157] Compared to Comparative Example 1, the gradient pore electrode prepared in Example 1 effectively optimizes the ion transport path, reduces interface impedance, and increases electrode structural stability. The battery exhibits higher rate performance, cycle stability, and energy density, especially with significantly improved long-cycle stability.

[0158] Compared to Comparative Example 2, the gradient pore electrode prepared in Example 3 effectively optimizes the ion transport path, reduces interface impedance, and increases electrode structural stability. The battery exhibits higher rate performance, cycle stability, and energy density, especially with significantly improved long-cycle stability.

[0159] Compared to Comparative Example 3, the gradient pore electrode prepared in Example 5 effectively optimizes the ion transport path, reduces interface impedance, and increases electrode structural stability. The battery exhibits higher rate performance, cycle stability, and energy density, especially with significantly improved long-cycle stability.

[0160] Compared to Example 1, the gradient pore electrode prepared in Example 2 has an inner layer porosity in the range of 28% to 36% and an outer layer porosity in the range of 45% to 55%. The resulting battery has a lower interface impedance and improved rate performance, cycle stability and energy density.

[0161] Compared to Example 3, the gradient pore electrode prepared in Example 4 has an inner layer porosity in the range of 28% to 36% and an outer layer porosity in the range of 45% to 55%. The resulting battery has a lower interface impedance and improved rate performance, cycle stability and energy density.

[0162] Compared to Example 5, the gradient porosity electrode prepared in Example 6 has an inner layer porosity in the range of 28% to 36% and an outer layer porosity in the range of 45% to 55%. The resulting battery has a lower interface impedance and improved rate performance, cycle stability and energy density.

[0163] Compared to Examples 7 and 8, the gradient pore electrode prepared in Example 2 has an inner layer porosity in the range of 28% to 36%, and the difference between the inner and outer layer porosities is in the range of 5% to 18%. The prepared battery has a lower interface impedance, and its cycle stability and energy density are significantly improved, which is significantly better than that of Example 8.

[0164] Compared to Example 9, the gradient pore electrode prepared in Example 2 has an outer layer porosity in the range of 45% to 55%, and the difference between the inner layer porosity and the outer layer porosity is in the range of 5% to 18%. The prepared battery has a lower interface impedance, and its cycle stability and energy density are significantly improved.

[0165] Compared to Example 10, in the gradient pore electrode prepared in Example 2, the mass ratio of solid electrolyte to gel electrolyte is in the range of 100:(7-10). The interfacial impedance of the prepared battery decreases, and its first charge-discharge efficiency, rate performance, cycle stability and energy density are significantly improved.

[0166] Compared to Example 11, which did not employ layered laying in the preparation of the first and second raw material layers, Example 2, which used layered laying, resulted in a gradient pore electrode with significantly increased porosity. This facilitates the uniform discharge of the pore-forming agent during gas generation and pore formation, resulting in more and more uniform pores. It also helps to optimize ion transport paths, reduce interfacial impedance, and increase electrode structural stability. Consequently, the rate performance, cycle stability, and energy density of the prepared battery are all significantly improved.

[0167] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a semi-solid battery positive electrode, characterized by, The semi-solid-state battery cathode includes: a current collector and an active material layer disposed on at least one side of the current collector; the active material layer includes at least two sub-active material layers; each active material layer has micropores, and the porosity of each sub-active material layer increases along the thickness direction of the semi-solid-state battery cathode away from the current collector; along the thickness direction of the semi-solid-state battery cathode, the porosity of the sub-active material layer closest to the current collector is 28% to 36%, and the porosity of the sub-active material layer farthest from the current collector is 45% to 55%; the active material layer includes active materials, additives, a solid electrolyte, and a gel electrolyte, the gel electrolyte including a three-dimensional gel network formed by in-situ polymerization of polymeric monomers, lithium salts, and an initiator, the active materials, the additives, and the solid electrolyte being dispersed in the three-dimensional gel network; the preparation method includes the following steps: Active material raw material layers with different contents of pore-forming agent are sequentially laminated onto the current collector in order of increasing content of the pore-forming agent in the thickness direction away from the current collector to form active material raw material layers with different contents of pore-forming agent. Then, the pore-forming agent is allowed to form micropores to obtain the semi-solid battery positive electrode. The active material raw material layer includes active materials, additives, solid electrolytes, and gel electrolyte precursors; the pore-forming agent includes one or more of ammonium bicarbonate, ammonium carbonate, and urea; the gel electrolyte precursor includes polymer monomers, lithium salts, and initiators. The active material raw material layer with different contents of pore-forming agent is prepared by the following steps: The active material and the additives are mixed to obtain a first mixture; Different masses of pore-forming agents were mixed with gel electrolyte precursors to form gel electrolyte precursors with different contents of pore-forming agents. The solid electrolyte is mixed with the gel electrolyte precursor with different contents of pore-forming agent to form a semi-solid material with different contents of pore-forming agent. The first mixture is laid to form several first mixture layers, and each first mixture layer is laid in layers along the thickness direction of the semi-solid battery positive electrode away from the current collector. The semi-solid materials with different contents of pore-forming agent are sequentially laid on a first mixture layer in order of increasing content of pore-forming agent in the thickness direction of the semi-solid battery positive electrode away from the current collector, and the active material raw material layers with different contents of pore-forming agent are formed by lamination respectively. The step of forming the micropores with the pore-forming agent includes heat-treating the active material raw material layer with different contents of the pore-forming agent to decompose the pore-forming agent to form the micropores, and polymerizing the gel electrolyte precursor in situ.

2. The method of producing a semi-solid battery cathode according to claim 1, characterized by, By weight percentage, along the thickness direction of the positive electrode of the semi-solid battery, the content of pore-forming agent in the active material raw material layer closest to the current collector is 4% to 6%, and the content of pore-forming agent in the active material raw material layer farthest from the current collector is 1% to 3%. And / or, The difference in pore-forming agent content between any two adjacent active material raw material layers, by weight percentage, is 1.5% to 3%. And / or, The lamination pressure range is 4 MPa to 10 MPa; And / or, The lamination temperature is 40°C to 50°C.

3. The method of producing a semi-solid battery cathode according to claim 2, characterized by, The heat treatment is carried out at a temperature of 60°C to 80°C for a time of 4 to 12 hours.

4. The method for preparing the positive electrode of a semi-solid-state battery according to any one of claims 1 to 3, characterized in that, The lamination process employs gradient calendering, and the lamination pressure for forming each active material raw material layer decreases along the thickness direction of the semi-solid battery positive electrode, away from the current collector.

5. The method of producing a semi-solid battery cathode according to claim 4, characterized by, Along the thickness direction opposite to the positive electrode of the semi-solid battery, the pressure of the active material layer closest to the current collector is 6 MPa to 8 MPa, and the porosity of the active material layer farthest from the current collector is 4 MPa to 5 MPa; and / or, The pressure difference between the laminations forming two adjacent active material raw material layers ranges from 0.5 MPa to 2 MPa.

6. The method for preparing the positive electrode of a semi-solid-state battery according to claim 1, characterized in that, The difference in porosity between any two adjacent sub-active material layers is 5% to 18%.

7. The method of claim 1, wherein the semi-solid battery cathode is prepared by a process comprising: The active material includes one or two of ternary materials and lithium iron phosphate; and / or, The polymeric monomer includes one or more of pentaerythritol tetraacrylate, methyl methacrylate, and ethylene glycol dimethacrylate; and / or, The lithium salt includes one or more of LiPF6, LiTFSI, and LiBOB; and / or, The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and tert-butyl peroxide; and / or The solid electrolyte includes one or more of sulfide solid electrolytes, oxide solid electrolytes, or phosphate solid electrolytes, and / or, The mass ratio of the active material to the auxiliary agent is (92-98):(2-8); and / or, The mass ratio of the solid electrolyte to the gel electrolyte is 100:(5-15), and the gel electrolyte comprises a three-dimensional gel network formed by in-situ polymerization of the polymeric monomer, the lithium salt, and the initiator at a mass ratio of 10:(0.5-1.5):(1-3); and / or, The additives include conductive agents, which include one or more of Super P, carbon nanotubes, graphene, or conductive carbon black; and / or, The additives include binders, which include one or more of polyvinylidene fluoride, polyethylene oxide, or polyvinyl alcohol; and / or, The additives include lithium supplements, which include one or more of lithium nickelate, lithium oxalate, and lithium nitride.

Images