Electrode components and their preparation methods, batteries

Abstract

This invention discloses an electrode assembly, its fabrication method, and a battery. The electrode assembly includes a first layer obtained by in-situ polymerization and a second layer obtained by in-situ polymerization. The first layer includes a first polymer, an active material, and a first filler. The second layer is disposed on one side of the first layer and includes a second polymer and a second filler. One of the first filler and the second filler includes an inert filler, and the other includes an active filler comprising lithium. The electrode assembly provided by this application has low impedance, which is beneficial for improving the cycle performance and rate performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to an electrode assembly and its preparation method, and a battery. Background Technology

[0002] With the development of portable electronic devices such as mobile phones, digital cameras, and laptops, people's demand for portable power sources is becoming increasingly strong. As a result, rechargeable batteries with small size, large capacity, long life, low self-discharge, and good safety have been developed.

[0003] Currently, rechargeable batteries on the market use organic liquid electrolytes. Under extreme conditions such as puncture or short circuit, these electrolytes can cause fires and explosions due to thermal runaway. In contrast, using solid electrolytes can significantly reduce the flammable components in the battery, greatly improving its safety performance. However, in such an electrode structure, the solid-solid interface impedance between the battery electrodes and the solid electrolyte is very high, which affects the ionic conductivity of the electrodes, resulting in poor charge / discharge performance and rate capability.

[0004] To address the aforementioned issues, in-situ solidification combined with the addition of inorganic fillers is commonly employed to deposit solid electrolytes on the electrode surface, thereby reducing interfacial impedance. For example, one existing method involves adding a uniformly mixed electrolyte precursor into the battery cell and then forming a composite electrolyte through in-situ polymerization under heating. However, in this method, the inorganic filler in the precursor remains outside the battery cell after the cell has been stacked and assembled, preventing it from reaching the electrode surface and thus failing to achieve its intended functionality. Another existing technology provides a method for preparing solid electrolytes through in-situ polymerization, comprising polymer monomers, crosslinking agents, electrolyte salts, and initiators, and including inorganic fillers. While this method directly forms a solid electrolyte layer containing inorganic fillers on the electrode surface, its effect on reducing interfacial impedance is limited, and the conductivity of lithium ions between the electrode and the electrolyte is poor. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one object of this invention is to provide an electrode assembly and its preparation method, as well as a battery, wherein the electrode assembly has good ionic conductivity, thereby improving the charge / discharge performance and rate performance of the battery.

[0006] In a first aspect, the present invention provides an electrode assembly. According to an embodiment of the present invention, the electrode assembly includes a first layer obtained by in-situ polymerization and a second layer obtained by in-situ polymerization. The first layer includes a first polymer, an active material, and a first filler. The second layer is disposed on one side of the first layer and includes a second polymer and a second filler. The first filler and the second filler include an inert filler and the other includes an active filler, wherein the active filler includes lithium.

[0007] According to the electrode assembly of the above embodiments of the present invention, the addition of inert filler and active filler can disrupt the orderliness of the chain segments in the first polymer and the second polymer, reduce the crystallinity of the first polymer and the second polymer, enhance the chain segment mobility of the first polymer and the second polymer, which is beneficial to the transport of lithium ions, thereby improving the ionic conductivity of the solid electrolyte. The active filler can also provide lithium ions as an active material and become a lithium ion transport carrier, while the groups on the surface of the inert filler can promote the dissociation of lithium salt and interact with the polar groups in the first polymer or the second polymer, weakening the complexation between lithium ions and the first polymer or the second polymer, thereby promoting the transfer of lithium ions in the solid electrolyte and reducing the impedance of the electrode assembly. Furthermore, by layering inert and active fillers (e.g., inert filler in the first layer and active filler in the second layer; or active filler in the first layer and inert filler in the second layer), the inert filler enhances the ionic conductivity at the interface between the active material particles and the electrolyte layer. After lithium ions continuously diffuse into the electrolyte layer through the interface phase, the active filler itself also contributes to ionic conductivity, acting as a lithium ion permeation channel. This ensures the uniformity of lithium ion transport across each layer, thereby further improving the conductivity of the solid-state electrolyte. Thus, through the interaction between the first and second layers, the impedance of the electrode assembly can be reduced, which is beneficial for improving the battery's cycle performance and rate performance.

[0008] In addition, the electrode assembly according to the above embodiments of the present invention may also have the following additional technical features: In some embodiments of the present invention, the first filler comprises an inert filler, and the second filler comprises an active filler. This facilitates a reduction in the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0009] In some embodiments of the present invention, the crystallinity of the first polymer is 5%-30%. This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0010] In some embodiments of the present invention, the first polymer includes at least one selected from polymethyl methacrylate, polyethyl methacrylate, polyvinyl carbonate, polymethoxyethylene glycol acrylate, polyethylene glycol dimethacrylate, polyvinyl carbonate, polyethylene sulfite, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, and vinylidene fluoride hexafluoropropylene copolymer. This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0011] In some embodiments of the present invention, the crystallinity of the second polymer is 8%-35%. This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0012] In some embodiments of the present invention, the second polymer comprises at least one selected from polymethyl methacrylate, polyethyl methacrylate, polyvinyl carbonate, polymethoxyethylene glycol acrylate, polyethylene glycol dimethacrylate, polyvinyl carbonate, polyethylene sulfite, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, and vinylidene fluoride hexafluoropropylene copolymer. This facilitates a reduction in the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0013] In some embodiments of the present invention, the first polymer and the second polymer are identical. This facilitates a reduction in the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0014] In some embodiments of the present invention, the particle size of the inert filler is 10 nm-500 nm. This helps to reduce the impedance of the electrode assembly and improves the cycle performance and rate performance of the battery.

[0015] In some embodiments of the present invention, the inert filler includes Al2O3, TiO2, SiO2, ZrO2, BaTiO3, and SrBi4Ti4O. 15 It contains at least one of carbon nanotubes, montmorillonite, and talc. This effectively improves the electrical conductivity of the electrode active material, thereby reducing the impedance of the electrode assembly.

[0016] In some embodiments of the present invention, the particle size of the active filler is 0.5 μm-5 μm. This allows the active filler to fill the first layer, acting as an active material to conduct lithium ions and reduce the impedance of the electrode assembly.

[0017] In some embodiments of the present invention, the active filler includes Li 0.75 La 0.5 TiO3, Li 1.3 Al 0.3 Ti1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li7La3Zr2O 12 Li 6.55 La3Zr2Ga 0.45 O 12 Li 2.8 Zn 0.6 GeO4, Li 3.25 Si 0.25 P 0.75 O4, Li 3.6 Ge 0.8 S 0.2 At least one of O4 and LiPON. This reduces contact resistance and interface loss, which helps to lower the impedance of the electrode assembly and improves the cycle performance and rate performance of the battery.

[0018] In some embodiments of the present invention, the first layer comprises a first lithium salt. This helps to reduce the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0019] In some embodiments of the present invention, the first lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBOB, and LiClO4. This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0020] In some embodiments of the present invention, the second layer comprises a second lithium salt. This helps to reduce the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0021] In some embodiments of the present invention, the second lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBOB, and LiClO4. This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0022] In some embodiments of the present invention, the active material includes a positive electrode active material. This enables the storage and release of lithium ions.

[0023] In some embodiments of the present invention, the electrode assembly further includes a current collector, wherein the first layer is disposed on the surface of the current collector, and the second layer is disposed on the surface of the first layer away from the current collector.

[0024] In some embodiments of the present invention, the thickness of the first layer is 25 μm-130 μm. This helps to reduce the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0025] In some embodiments of the present invention, the thickness of the second layer is 5 μm-50 μm. This helps to reduce the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0026] In a second aspect, the present invention provides a method for preparing the aforementioned electrode assembly. According to an embodiment of the invention, the method includes in-situ polymerization to prepare a first layer; and in-situ polymerization on the first layer to form a second layer, thereby obtaining the electrode assembly. Thus, through the interaction of the bilayer structures, the ionic conductivity of the solid electrolyte can be improved, which is beneficial for reducing the impedance of the electrode assembly and can improve the cycle performance and rate performance of the battery.

[0027] In some embodiments of the present invention, the method includes: mixing a first filler, a first lithium salt, a first polymer monomer, a first crosslinking agent, and a first initiator to obtain a first slurry; transferring the first slurry onto an electrode, allowing the first slurry to enter the active material layer of the electrode, and heating it for the first time to obtain a first layer, wherein the active material layer includes active material; mixing a first filler, a second lithium salt, a second polymer monomer, a second crosslinking agent, and a second initiator to obtain a second slurry; transferring the second slurry onto the first layer, and heating it a second time to obtain a second layer, thus obtaining an electrode assembly. This allows for the acquisition of an electrode assembly with a dual-functional layer structure. Through the interaction of the dual-layer structure, the ionic conductivity of the solid electrolyte can be improved, which is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0028] In some embodiments of the present invention, the mass ratio of the first slurry to the second slurry is (5-20):(1-10). This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0029] In some embodiments of the present invention, the molar concentration of the first lithium salt in the first slurry is 0.5 mol / L to 2 mol / L. This optimizes ion transport performance, improves the stability of ionic conductivity, and consequently enhances battery safety.

[0030] In some embodiments of the present invention, the mass ratio of the first polymer monomer to the first crosslinking agent is (10-20):(1-8). This improves the ion transport capability of the first polymer, which helps reduce the impedance of the electrode assembly and improves the cycle performance and rate performance of the battery.

[0031] In some embodiments of the present invention, the mass of the first filler is A, the mass of the first polymer monomer is B, and the mass of the first crosslinking agent is C, wherein 0

[0032] In some embodiments of the present invention, the first polymer monomer includes at least one selected from methoxy polyethylene glycol acrylate, ethylene glycol dimethacrylate, methyl methacrylate, vinylene carbonate, vinyl sulfite, ethyl methacrylate, acrylonitrile, ethylene oxide, vinylidene fluoride, ethylene oxide, and a blend monomer of vinylidene fluoride hexafluoropropylene. This reduces interfacial impedance and improves the interfacial stability between the solid electrolyte and the electrode.

[0033] In some embodiments of the present invention, the first crosslinking agent includes at least one selected from polyethylene glycol diacrylate, glycidyl methacrylate, tetraethylene glycol dimethacrylate, and pentaerythritol tetraacrylate. This promotes the crosslinking reaction of the first polymer, forming a first polymer with a three-dimensional network structure, which is beneficial for ion transport and diffusion, thereby reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0034] In some embodiments of the present invention, the first initiator includes at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and dodecyl peroxide. This facilitates the crosslinking reaction between the first crosslinking agent and the first polymer monomer, resulting in a first polymer having a three-dimensional network structure.

[0035] In some embodiments of the present invention, the temperature of the first heating is 45°C-100°C. This increases the crosslinking reaction rate between the first polymer monomer and the first crosslinking agent, which is beneficial for obtaining a first polymer with a three-dimensional network structure, reducing the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0036] In some embodiments of the present invention, the first heating time is 60s-600s. This allows control over the degree of cross-linking reaction of the first polymer monomer, thereby controlling the structure of the first polymer. This facilitates obtaining a first polymer with a three-dimensional network structure, reducing the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0037] In some embodiments of the present invention, the molar concentration of the second lithium salt in the second slurry is 0.5 mol / L to 2 mol / L. This optimizes ion transport performance, improves the stability of ionic conductivity, and consequently enhances battery safety.​

[0038] In some embodiments of the present invention, the mass ratio of the second polymer monomer to the second crosslinking agent is (10 - 20):(1 - 8). Thus, it is possible to affect the movement ability of the second polymer segment, improve the ion transport ability of the second polymer, facilitate the reduction of the impedance of the electrode assembly, and improve the cycle performance and rate performance of the battery.

[0039] In some embodiments of the present invention, the mass of the second filler is M, the mass of the second polymer monomer is F, and the mass of the second crosslinking agent is N, where 0 < M / (F + N)×100% ≤ 30%. Thus, more ion transport channels can be provided to promote ion transport, thereby increasing the ionic conductivity of the solid electrolyte, facilitating the reduction of the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0040] In some embodiments of the present invention, the second polymer monomer includes at least one of methoxypolyethylene glycol acrylate, ethylene glycol dimethacrylate, methyl methacrylate, vinylene carbonate, ethylene vinyl sulfite, ethyl methacrylate, acrylonitrile, ethylene oxide, vinylidene fluoride, ethylene oxide and vinylidene fluoride - hexafluoropropylene blend monomer. Thus, it is possible to reduce the interfacial impedance and improve the interfacial stability between the solid electrolyte and the electrode.

[0041] In some embodiments of the present invention, the second crosslinking agent includes at least one of polyethylene glycol diacrylate, glycidyl methacrylate, tetraethylene glycol dimethacrylate and pentaerythritol tetraacrylate. Thus, it can react with the second polymer monomer to promote the crosslinking reaction of the second polymer, forming a second polymer with a three - dimensional network structure, which is beneficial to ion transport and diffusion.

[0042] In some embodiments of the present invention, the second initiator includes at least one of azobisisobutyronitrile, azobisisoheptonitrile, dibenzoyl peroxide and lauroyl peroxide. Thus, it is beneficial to ion transport and diffusion, facilitates the reduction of the impedance of the electrode assembly, and improves the cycle performance and rate performance of the battery.

[0043] In some embodiments of the present invention, the temperature of the second heating is 45°C - 100°C. Thus, the crosslinking reaction rate between the second polymer monomer and the second crosslinking agent can be increased, which is beneficial to obtaining a second polymer with a three - dimensional network structure, increasing the ionic conductivity of the solid electrolyte, reducing the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0044] In some embodiments of the present invention, the second heating time is 60s-600s. This allows for control of the degree of cross-linking reaction of the second polymer monomers, thereby enabling control of the structure of the second polymer. This facilitates obtaining a second polymer with a three-dimensional network structure, reducing the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0045] In some embodiments of the present invention, the transfer method is at least one of spraying, dripping, coating, and screen printing. This results in an electrode assembly with a dual-functional layer structure. Through the interaction of the dual layers, the ionic conductivity of the solid electrolyte can be improved, which helps to reduce the impedance of the electrode assembly and improves the cycle performance and rate performance of the battery.

[0046] In a third aspect, the present invention provides a battery. This battery includes the electrode assembly described above or an electrode assembly obtained using the method described above. Compared with the prior art, this battery has better overall performance, possessing both better cycle performance and rate performance.

[0047] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0048] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This shows a schematic diagram of the electrode assembly according to an embodiment of the present invention; Figure 2 A schematic diagram of a method for preparing an electrode assembly according to an embodiment of the present invention is shown.

[0049] Icon labels: Electrode assembly 100, first layer 10, active material 11, first filler 12, first polymer 13, second layer 20, second filler 21, second polymer 22. Detailed Implementation

[0050] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0051] With the development of portable electronic devices such as mobile phones, digital cameras, and laptops, people's demand for portable power sources is becoming increasingly strong. As a result, rechargeable batteries with small size, large capacity, long life, low self-discharge, and good safety have been developed.

[0052] Currently, rechargeable batteries on the market use organic liquid electrolytes. Under extreme conditions such as puncture or short circuit, these electrolytes can cause fires and explosions due to thermal runaway. In contrast, using solid electrolytes can significantly reduce the flammable components in the battery, greatly improving its safety performance. However, in such an electrode structure, the solid-solid interface impedance between the battery electrodes and the solid electrolyte is very high, which affects the ionic conductivity of the electrodes, resulting in poor charge / discharge performance and rate capability.

[0053] In view of this, in a first aspect, the present invention provides an electrode assembly 100, see [link to previous document]. Figure 1 According to an embodiment of the present invention, the electrode assembly 100 includes a first layer 10 obtained by in-situ polymerization and a second layer 20 obtained by in-situ polymerization. The first layer 10 includes a first polymer 13, an active material 11 and a first filler 12. The second layer 20 is disposed on one side of the first layer 10. The second layer 20 includes a second polymer 22 and a second filler 21. One of the first filler 12 and the second filler 21 includes an inert filler, and the other includes an active filler, wherein the active filler includes lithium.

[0054] According to the electrode assembly of the above embodiments of the present invention, the addition of inert filler and active filler can disrupt the orderliness of the chain segments in the first polymer or the second polymer, reduce the crystallinity of the first polymer or the second polymer, enhance the chain segment mobility of the first polymer or the second polymer, which is beneficial to the transport of lithium ions, thereby improving the ionic conductivity of the solid electrolyte. The active filler can also provide lithium ions as an active material and become a lithium ion transport carrier, while the groups on the surface of the inert filler can promote the dissociation of lithium salt and interact with the polar groups in the first polymer or the second polymer, weakening the complexation between lithium ions and the first polymer or the second polymer, thereby promoting the transfer of lithium ions in the solid electrolyte and reducing the impedance of the electrode assembly. Furthermore, by layering inert and active fillers (e.g., inert filler in the first layer and active filler in the second layer; or active filler in the first layer and inert filler in the second layer), the inert filler enhances the ionic conductivity at the interface between the active material particles and the electrolyte layer. After lithium ions continuously diffuse into the electrolyte layer through the interface phase, the active filler itself also contributes to ionic conductivity, acting as a lithium ion permeation channel. This ensures the uniformity of lithium ion transport across each layer, thereby further improving the conductivity of the solid-state electrolyte. Thus, through the interaction between the first and second layers, the impedance of the electrode assembly can be reduced, which is beneficial for improving the battery's cycle performance and rate performance.

[0055] It is understood that in the embodiments of this application, inert filler refers to a substance that does not contain lithium and does not undergo a chemical reaction in the battery, while active filler refers to a substance that contains lithium.

[0056] It should be noted that, in the embodiments of this application, the solid electrolyte includes a first polymer, a second polymer, a first filler, and a second filler.

[0057] It should be noted that active materials refer to materials in battery electrodes that can undergo redox reactions in the battery reaction. This application does not specifically limit the type of active material. For example, active materials can be positive electrode active materials or negative electrode active materials.

[0058] According to some embodiments of the present invention, the first filler includes an inert filler, and the second filler includes an active filler. The inert filler, as the first filler, fills the first layer and can disrupt the orderliness of the chain segments in the first polymer, reduce the crystallinity of the first polymer, and enhance the chain segment mobility of the first polymer, which is beneficial for lithium ion transport. This, in turn, can improve the ionic conductivity of the solid electrolyte. The inert filler can also enter the pores between the active material particles, be placed close to the active material, and through strong interfacial interaction with the polymer electrolyte, establish a rapid Li+ transport channel at the organic-inorganic interface, completing the first "acceleration" of lithium ion transport in the electrolyte from the active material, thus improving the ion transport performance of the first polymer at the interface between the active material and the solid electrolyte. Furthermore, the acidic / basic groups on the surface of the inert filler have strong Lewis acid-base interactions with the cations / anions in the Li salt, promoting the L+ ion transport. The dissociation of the i-salt also plays a reinforcing role. On the other hand, it interacts with polar groups in the first polymer, such as hydroxyl, nitrile, ester, and carboxyl groups, weakening the complexation between lithium ions and the first polymer, thereby promoting lithium ion transfer in the solid electrolyte. The active filler, as the second filler, fills the second layer, disrupting the orderliness of the chain segments in the second polymer, reducing its crystallinity, and enhancing its chain segment mobility, which is beneficial for lithium ion transport. This, in turn, improves the ionic conductivity of the solid electrolyte. The active filler can also provide lithium ions as an active material and act as a lithium ion transport carrier, further improving the ionic conductivity of the solid electrolyte. Furthermore, the active filler can also act as a reinforcing phase, tightly binding with the second polymer through physical or chemical forces, enhancing the mechanical properties of the solid electrolyte. Therefore, with the inert filler in the first layer and the active filler in the second layer, the synergistic effect of the two layers helps reduce the impedance of the electrode assembly, improving the battery's cycle performance and rate performance.

[0059] According to some embodiments of the present invention, the crystallinity of the first polymer is 5%-30%, for example, it can be 5%, 10%, 20%, 30%, etc. By limiting the crystallinity of the first polymer to the above range, the microstructure of the first polymer is relatively disordered, the interaction between molecular chains is weakened, and the chain segments are easier to move, thereby enhancing the chain segment mobility of the first polymer, which can promote ion transport. As a result, the ionic conductivity of the solid electrolyte can be improved, which is beneficial to reducing the impedance of the electrode components and improving the cycle performance and rate performance of the battery.

[0060] According to some embodiments of the present invention, the first polymer comprises at least one selected from polymethyl methacrylate, polyethyl methacrylate, polyvinyl carbonate, polymethoxyethylene glycol acrylate, polyethylene glycol dimethacrylate, polyvinyl carbonate, polyethylene sulfite, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, and a copolymer of polyethylene oxide and polyvinylidene fluoride hexafluoropropylene. The selected first polymer possesses strong chain segment mobility, and the functional groups in the first polymer (such as -O- in polyethylene oxide and -C≡N- in polyacrylonitrile) continuously couple and decouple with lithium ions, providing strong ion transport channels, which is beneficial for ion diffusion and transport, thereby improving the ionic conductivity of the solid electrolyte.

[0061] According to some embodiments of the present invention, the crystallinity of the second polymer is 8%-35%, for example, it can be 8%, 10%, 15%, 20%, 30%, 35%, etc. By limiting the crystallinity of the second polymer to the above range, the microstructure of the second polymer is relatively disordered, the interaction between molecular chains is weakened, and the chain segments are easier to move, thereby enhancing the chain segment mobility of the second polymer, which can promote ion transport. As a result, the ionic conductivity of the solid electrolyte can be improved, which is beneficial to reducing the impedance of the electrode components and improving the cycle performance and rate performance of the battery.

[0062] According to some embodiments of the present invention, the second polymer comprises at least one of polymethyl methacrylate, polyethyl methacrylate, polyvinyl carbonate, polymethoxyethylene glycol acrylate, polyethylene glycol dimethacrylate, polyvinyl carbonate, polyethylene sulfite, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, and a copolymer of polyethylene oxide and polyvinylidene fluoride hexafluoropropylene. The selected second polymer possesses strong chain segment mobility, and the functional groups in the second polymer (such as -O- in polyethylene oxide and -C≡N- in polyacrylonitrile) continuously couple and decouple with lithium ions, providing strong ion transport channels, which is beneficial for ion diffusion and transport. This improves the ionic conductivity of the solid electrolyte, reduces the impedance of the electrode assembly, and enhances the cycle performance and rate performance of the battery.

[0063] According to some embodiments of the present invention, the first polymer and the second polymer are the same; due to their similar polarity and crystallinity, the first polymer and the second polymer have good compatibility and low interfacial impedance; furthermore, when the first polymer and the second polymer are the same, the connection between the first layer and the second layer can be further improved on this basis, preventing the formation of a delamination structure between the two layers.

[0064] According to some embodiments of the present invention, the particle size of the inert filler is 10 nm to 500 nm. For example, it can be 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 500 nm, etc. By limiting the particle size of the inert filler to the above range, the inert filler can enter the pores between the active material particles in the first layer, improving the ion transport performance of the polymer at the interface between the active material and the solid electrolyte. Moreover, the surface functional groups on the surface of the inert filler are coordinated with lithium ions and polymers respectively, weakening the interaction between lithium ions and polymers and lowering the energy barrier for lithium ion transport, thereby promoting the transfer of lithium ions in the solid electrolyte, which in turn can improve the ionic conductivity of the solid electrolyte, which is beneficial to reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0065] According to some embodiments of the present invention, the inert filler includes Al2O3, TiO2, SiO2, ZrO2, BaTiO3, and SrBi4Ti4O. 15 At least one of carbon nanotubes, montmorillonite, and talc. The groups on the surface of the above-mentioned inert filler can promote the dissociation of lithium salts and interact with the polar groups of polymers, weakening the complexation between lithium ions and polymers, thereby promoting the transfer of lithium ions in the solid electrolyte, which can improve the ionic conductivity of the solid electrolyte, help reduce the impedance of electrode components, and improve the cycle performance and rate performance of the battery.

[0066] According to some embodiments of the present invention, the particle size of the active filler is 0.5 μm-5 μm. For example, it can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. By limiting the particle size of the active filler to the above range, the active filler can be filled in the second layer, which can act as an active material to conduct lithium ions and become a lithium ion transport carrier, thereby improving the ionic conductivity of the solid electrolyte, which is beneficial to reducing the impedance of the electrode assembly, improving the cycle performance and rate performance of the battery, and enhancing the mechanical strength of the solid electrolyte.

[0067] According to some embodiments of the present invention, the active filler comprises Li 0.75 La 0.5 TiO3, Li 1.3 Al0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li7La3Zr2O 12 Li 6.55 La3Zr2Ga 0.45 O 12 Li 2.8 Zn 0.6 GeO4, Li 3.25 Si 0.25 P 0.75 O4, Li 3.6 Ge 0.8 S 0.2 At least one of O4 and LiPON. All of the above-mentioned active fillers contain lithium, enabling them to provide lithium ions as active materials and act as lithium ion transport carriers, thereby improving the ionic conductivity of the solid electrolyte. Furthermore, lithium-containing active fillers can improve the interfacial contact between the solid electrolyte and the electrode, reducing the resistance of lithium ions across the interface, thus increasing the ionic conductivity of the solid electrolyte. This is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0068] According to some embodiments of the present invention, the first layer includes a first lithium salt. The addition of the first lithium salt, as a component of the solid electrolyte, provides a channel for lithium ion migration within the solid electrolyte, offering a migration path for lithium ions. This allows lithium ions to move more easily within the solid electrolyte under the influence of an electric field. The first lithium salt also reduces the interfacial energy between the solid electrolyte and the electrode, reducing the resistance of lithium ions across the interface. This improves the ionic conductivity of the solid electrolyte, which is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0069] According to some embodiments of the present invention, the first lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBOB, and LiClO4. By selecting the above-mentioned first lithium salt, a channel for lithium ion migration can be provided, providing a migration path for lithium ions, making it easier for lithium ions to move in the solid electrolyte under the action of an electric field. It can also reduce the interfacial energy between the solid electrolyte and the electrode, reducing the resistance of lithium ions across the interface. As a result, the ionic conductivity of the solid electrolyte can be improved, which is beneficial to reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0070] According to some embodiments of the present invention, the second layer includes a second lithium salt. The addition of the second lithium salt, as a component of the solid electrolyte, provides a channel for lithium ion migration, offering a migration path for lithium ions. This allows lithium ions to move more easily within the solid electrolyte under the influence of an electric field. It also reduces the interfacial energy between the solid electrolyte and the electrode, decreasing the resistance of lithium ions across the interface. Consequently, it improves the ionic conductivity of the solid electrolyte, which is beneficial for reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0071] According to some embodiments of the present invention, the second lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBOB, and LiClO4. By selecting the above-mentioned second lithium salt, a channel for lithium ion migration can be provided, providing a migration path for lithium ions, making it easier for lithium ions to move in the solid electrolyte under the action of an electric field. It can also reduce the interfacial energy between the solid electrolyte and the electrode, reducing the resistance of lithium ions across the interface. As a result, the ionic conductivity of the solid electrolyte can be improved, which is beneficial to reducing the impedance of the electrode assembly and improving the cycle performance and rate performance of the battery.

[0072] According to some embodiments of the present invention, the active material includes a positive electrode active material. The positive electrode active material can store and release lithium ions in the battery. During charging, lithium ions flow from the negative electrode to the positive electrode, and the positive electrode active material receives the lithium ions, thereby storing electrical energy. During discharging, lithium ions flow from the positive electrode to the negative electrode, and the positive electrode active material releases the lithium ions, releasing the stored electrical energy.

[0073] According to some embodiments of the present invention, the electrode assembly further includes a current collector, the first layer being disposed on the surface of the current collector, and the second layer being disposed on the surface of the first layer away from the current collector.

[0074] According to some embodiments of the present invention, the thickness of the first layer is 25μm-130μm, for example, it can be 25μm, 50μm, 70μm, 100μm, 130μm, etc. This reduces the impedance of the electrode assembly, thereby improving the cycle performance and rate performance of the battery.

[0075] According to some embodiments of the present invention, the thickness of the second layer is 5μm-50μm, for example, it can be 5μm, 10μm, 20μm, 30μm, 50μm, etc., thereby reducing the impedance of the electrode assembly, which in turn helps to improve the cycle performance and rate performance of the battery.

[0076] In a second aspect, the present invention provides a method for preparing the above-described electrode assembly. See also embodiments of the present invention. Figure 2 The method includes: S100: In-situ polymerization to prepare the first layer.

[0077] In this step, a first layer is prepared by in-situ polymerization. The first layer includes a first polymer, an active material, and a first filler. The addition of the first filler can disrupt the orderliness of the first polymer chain segments in the first layer, reduce the crystallinity of the first polymer, enhance the chain segment mobility of the first polymer, which is beneficial to ion transport and thus improves the ionic conductivity of the solid electrolyte. In addition, the first filler can also fill the pores between the active material particles, improve the ion transport performance of the first polymer at the interface between the active material and the solid electrolyte, improve the ionic conductivity of the solid electrolyte, reduce the impedance of the electrode assembly, and improve the cycle performance and rate performance of the battery.

[0078] In some implementations, step S100 further includes steps S110 and S120.

[0079] S110: Mix the first filler, the first lithium salt, the first polymer monomer, the first crosslinking agent and the first initiator to obtain the first slurry.

[0080] In this step, a first slurry can be obtained by mixing a first filler, a first lithium salt, a first polymer monomer, a first crosslinking agent, and a first initiator.

[0081] According to some embodiments of the present invention, the molar concentration of the first lithium salt in the first slurry is 0.5 mol / L to 2 mol / L. For example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, etc. By limiting the molar concentration of the first lithium salt within the above range, the ion transport performance can be optimized, the stability of ionic conductivity can be improved, and thus the safety performance of the battery can be improved.

[0082] According to some embodiments of the present invention, the mass ratio of the first polymer monomer to the first crosslinking agent is (10-20):(1-8). For example, it can be 10:1, 10:5, 10:8, 15:1, 15:8, 20:1, 20:8, etc. The first crosslinking agent can promote crosslinking between the segments of the first polymer monomer to form the first polymer. By limiting the mass ratio of the first polymer monomer to the first crosslinking agent within the above range, the molecular weight and molecular weight distribution of the first polymer can be controlled, thereby affecting the mobility of the first polymer segments, improving the ion transport capacity of the first polymer, and thus improving the ionic conductivity of the solid electrolyte.

[0083] According to some embodiments of the present invention, the mass of the first filler is A, the mass of the first polymer monomer is B, and the mass of the first crosslinking agent is C, wherein, 0

[0084] According to some embodiments of the present invention, the first polymer monomer includes at least one selected from methoxy polyethylene glycol acrylate, ethylene glycol dimethacrylate, methyl methacrylate, vinylene carbonate, vinyl sulfite, ethyl methacrylate, acrylonitrile, ethylene oxide, vinylidene fluoride, ethylene oxide, and a blend monomer of vinylidene fluoride hexafluoropropylene. The aforementioned first polymer monomer can serve as an ion transport channel, improving ion transport capability, and can also interact with the electrode active material to form a stable interface layer, reducing interface impedance and improving the interface stability between the solid electrolyte and the electrode.

[0085] According to some embodiments of the present invention, the first crosslinking agent includes at least one selected from polyethylene glycol diacrylate, glycidyl methacrylate, tetraethylene glycol dimethacrylate, and pentaerythritol tetraacrylate. The aforementioned first crosslinking agent can react with the first polymer monomer to promote the crosslinking reaction of the first polymer, forming a first polymer with a three-dimensional network structure. This facilitates ion transport and diffusion, improves the ionic conductivity of the solid electrolyte, reduces the impedance of the electrode assembly, and improves the cycle performance and rate performance of the battery.

[0086] According to some embodiments of the present invention, the first initiator includes at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and dodecyl peroxide. Using the above-mentioned first initiator can promote the crosslinking reaction between the first crosslinking agent and the first polymer monomer, which is beneficial for obtaining a first polymer with a three-dimensional network structure, facilitating ion transport and diffusion, thereby improving the ionic conductivity of the solid electrolyte, reducing the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0087] S120: The first slurry is transferred to the electrode, so that the first slurry enters the active material layer of the electrode, and the first layer is obtained by heating for the first time, wherein the active material layer includes active material.

[0088] ​In this step, by transferring the first slurry onto the electrode, the first filler can flow into the pores between the active material particles inside the electrode along with the slurry components, improving the ion transport performance of the first polymer at the interface between the active material and the solid electrolyte. Heating then promotes the cross-linking reaction between the first polymer monomers and the first cross-linking agent under the action of the first initiator, resulting in the first polymer. Furthermore, the first filler can disrupt the orderliness of the chain segments in the first polymer, reducing its crystallinity and enhancing its chain segment mobility, which is beneficial for lithium-ion transport. This, in turn, improves the ionic conductivity of the solid electrolyte, thereby reducing the impedance of the electrode assembly and improving the battery's cycle performance and rate performance.

[0089] It should be noted that there is no particular limitation on the transfer method, and those skilled in the art can make flexible choices as needed. For example, the transfer method can be at least one of spraying, dripping, coating and screen printing.

[0090] According to some embodiments of the present invention, the temperature of the first heating is 45°C-100°C. For example, the temperature of the first heating can be 45°C, 50°C, 70°C, 90°C, 100°C, etc. By limiting the temperature of the first heating to the above range, the crosslinking reaction rate between the first polymer monomer and the first crosslinking agent can be increased, which is beneficial to obtaining a first polymer with a three-dimensional network structure and to improving the ionic conductivity of the solid electrolyte.

[0091] According to some embodiments of the present invention, the first heating time is 60s-600s, for example, it can be 60s, 100s, 200s, 400s, 500s, 600s, etc. By limiting the first heating time within the above range, the degree of cross-linking reaction of the first polymer monomer can be controlled, thereby controlling the structure of the first polymer, which is beneficial to obtaining a first polymer with a three-dimensional network structure and to improving the ionic conductivity of the solid electrolyte.

[0092] S200: A second layer is formed on the first layer to obtain an electrode assembly.

[0093] In this step, a second layer is formed on the first layer. The second layer includes a second polymer and a second filler. The addition of the second filler disrupts the orderliness of the second polymer chain segments in the second layer, reduces the crystallinity of the second polymer, enhances the chain segment mobility of the second polymer, which is beneficial to ion transport and thus can improve the ionic conductivity of the solid electrolyte.

[0094] Step S200 also includes steps S210 and S220.

[0095] S210: Mix the first filler, the second lithium salt, the second polymer monomer, the second crosslinker, and the second initiator to obtain a second slurry.

[0096] In this step, by mixing the first filler, the second lithium salt, the second polymer monomer, the second crosslinker, and the second initiator, a second slurry can be obtained.

[0097] According to some embodiments of the present invention, the molar concentration of the second lithium salt in the second slurry is 0.5 mol / L - 2 mol / L. For example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, etc. By limiting the molar concentration of the second lithium salt within the above range, the ion transport performance can be optimized, the stability of the ionic conductivity can be improved, and thus it is beneficial to improve the safety performance of the battery.

[0098] According to some embodiments of the present invention, the mass ratio of the second polymer monomer to the second crosslinker is (10 - 20):(1 - 8). For example, it can be 10:1, 10:5, 10:8, 15:1, 15:8, 20:1, 20:8, etc. The second crosslinker can promote crosslinking between the second polymer monomer segments to form a second polymer. By limiting the mass ratio of the second polymer monomer to the second crosslinker within the above range, the molecular weight and molecular weight distribution of the second polymer can be controlled, and thus the movement ability of the second polymer segments can be affected, the ion transport ability of the second polymer can be improved, and it is beneficial to improve the ionic conductivity of the solid electrolyte.

[0099] According to some embodiments of the present invention, the mass of the second filler is M, the mass of the second polymer monomer is F, and the mass of the second crosslinker is N, where 0 < M / (F + N)×100% ≤ 30%. For example, it can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc. By limiting the content of the second filler within the above range, more ion transport channels can be provided, ion transport can be promoted, the ionic conductivity of the solid electrolyte can be improved, it is beneficial to reduce the impedance of the electrode assembly, and the cycle performance and rate performance of the battery can be improved.

[0100] According to some embodiments of the present invention, the second polymer monomer includes at least one of methoxypolyethylene glycol acrylate, ethylene glycol dimethacrylate, methyl methacrylate, vinylene carbonate, ethylene vinyl sulfite, ethyl methacrylate, acrylonitrile, ethylene oxide, vinylidene fluoride, ethylene oxide and vinylidene fluoride - hexafluoropropylene blend monomer. The above - mentioned second polymer monomer can serve as an ion transport channel to improve the ion transport ability, and can also interact with the electrode active material to form a stable interfacial layer, reduce the interfacial impedance, and improve the interfacial stability between the solid electrolyte and the electrode.

[0101] According to some embodiments of the present invention, the second crosslinking agent includes at least one selected from polyethylene glycol diacrylate, glycidyl methacrylate, tetraethylene glycol dimethacrylate, and pentaerythritol tetraacrylate. The aforementioned second crosslinking agent can react with the second polymer monomer to promote the crosslinking reaction of the second polymer, forming a second polymer with a three-dimensional network structure. This facilitates ion transport and diffusion, improves the ionic conductivity of the solid electrolyte, reduces the impedance of the electrode assembly, and improves the cycle performance and rate performance of the battery.

[0102] According to some embodiments of the present invention, the second initiator includes at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and dodecyl peroxide. Using the above-mentioned second initiator can promote the crosslinking reaction between the second crosslinking agent and the second polymer monomer, which is beneficial for obtaining a second polymer with a three-dimensional network structure, facilitating ion transport and diffusion, thereby improving the ionic conductivity of the solid electrolyte, reducing the impedance of the electrode assembly, and improving the cycle performance and rate performance of the battery.

[0103] S220: The second slurry is transferred onto the first layer, and then heated a second time to obtain the second layer, thus obtaining the electrode assembly.

[0104] In this step, by transferring the second slurry onto the first layer, the second filler is filled into the second layer, which enhances the chain segment mobility of the second polymer and improves the ion diffusion capacity of the second polymer, thus improving the ionic conductivity of the electrode assembly. Furthermore, by heating, the second polymer monomers can undergo a cross-linking reaction with the second cross-linking agent under the action of the second initiator to obtain the second polymer. This improves the ionic conductivity of the solid electrolyte, reduces the impedance of the electrode assembly, and improves the cycle performance and rate performance of the battery.

[0105] It should be noted that there is no particular limitation on the transfer method, and those skilled in the art can make flexible choices as needed. For example, the transfer method can be at least one of spraying, dripping, coating and screen printing.

[0106] According to some embodiments of the present invention, the temperature of the second heating is 45°C-100°C. For example, the temperature of the second heating can be 45°C, 50°C, 70°C, 90°C, 100°C, etc. By limiting the temperature of the second heating within the above range, the crosslinking reaction rate between the second polymer monomer and the second crosslinking agent can be increased, which is beneficial to obtaining a second polymer with a three-dimensional network structure and to improving the ionic conductivity of the solid electrolyte.

[0107] According to some embodiments of the present invention, the second heating time is 60s-600s. For example, it can be 60s, 100s, 200s, 400s, 500s, 600s, etc. By limiting the second heating time within the above range, the degree of cross-linking reaction of the second polymer monomer can be controlled, thereby controlling the structure of the second polymer. This is beneficial for obtaining a second polymer with a three-dimensional network structure and for improving the ionic conductivity of the solid electrolyte.

[0108] According to some embodiments of the present invention, the mass ratio of the first slurry to the second slurry is (5-20):(1-10), for example, it can be 5:1, 5:10, 5:5, 20:1, 20:10, etc. By limiting the mass ratio of the first slurry and the second slurry within the above range, the thickness of the first layer and the thickness of the second layer can be controlled, which can reduce the impedance of the electrode assembly, improve the room temperature conductivity of the polymer, thereby improving the cycle performance and rate performance of the battery, and enhancing the mechanical strength of the electrolyte layer.

[0109] In other embodiments, the electrode assembly can also be fabricated using the following methods: In the preparation of the electrode sheet (taking the positive electrode sheet as an example), a first filler is added to the positive electrode slurry, and the slurry containing the first filler is coated on the positive electrode current collector. After drying, the positive electrode sheet is obtained. Then, a slurry containing a first polymer monomer, a second polymer monomer, a second filler, a first lithium salt, a second lithium salt, a first crosslinking agent, a second crosslinking agent, a first initiator, and a second initiator is coated on the positive electrode sheet.

[0110] In a third aspect, the present invention provides a battery comprising the electrode assembly described above or an electrode assembly prepared by the method described above. According to embodiments of the present invention, compared with the prior art, this battery has better overall performance, and can possess both better cycle performance and rate performance. It should be noted that the features and advantages described above for the electrode assembly and its preparation method also apply to this battery, and will not be repeated here.

[0111] The present disclosure will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0112] Example 1 Preparation of the first layer: (1) The first polymer monomer and the first crosslinking agent are mixed at a mass ratio of 19:1. 1 mol / L of the first lithium salt and 1.5 wt% of the first initiator are added until completely dissolved. Then, 15% of the first filler is added, and the mixture is stirred until it is evenly dispersed to obtain the first slurry. Wherein, the first polymer monomer is ethylene glycol dimethacrylate, the first crosslinking agent is tetraethylene glycol diacrylate, the first lithium salt is LiPF6, the first initiator is azobisisobutyronitrile, the first filler is Al2O3, and the particle size of the first filler is 15 nm.

[0113] (2) Take the first slurry prepared above and add it into the coating machine box. Coat the first slurry onto the positive electrode by transfer coating. Let it stand for 30 minutes. Then heat it in the coating machine oven at 80°C to initiate polymerization and form the first polymer. After reacting for 100 seconds, a first layer with a thickness of 50 μm is obtained. The first polymer is polyethylene glycol dimethacrylate and the crystallinity of the first polymer is 5%.

[0114] Preparation of the second layer: (1) The second polymer monomer and the second crosslinking agent are mixed at a mass ratio of 19:1. 1 mol / L of the second lithium salt and 1.5 wt% of the second initiator are added until completely dissolved. Then, 3 g of the second filler is added, and the mixture is stirred until evenly dispersed to obtain the second slurry. The second polymer monomer is ethylene glycol dimethacrylate, the second crosslinking agent is tetraethylene glycol diacrylate, the second lithium salt is LiPF6, the second initiator is azobisisobutyronitrile, and the second filler is Li... 1.3 Al 0.3 Ti 1.7 (PO4)3, the particle size of the first filler is 1μm.

[0115] (2) Take the second slurry prepared above and add it into the coating machine material box. Coat the second slurry onto the positive electrode sheet by transfer coating. Let it stand for 30 minutes. Then heat it in the coating machine oven at 80°C to initiate polymerization and form the second polymer. After reacting for 100 seconds, a second layer with a thickness of 30 μm is obtained, which is the electrode assembly. The second polymer is polyethylene glycol dimethacrylate and the crystallinity of the second polymer is 8%.

[0116] Battery preparation: The positive electrode assembly, high-porosity separator, and negative electrode prepared above are wound or stacked to prepare the battery cell, which is then assembled into an aluminum-plastic film, an appropriate amount of liquid electrolyte is added, vacuum sealed, and left to stand for 24 hours.

[0117] The electrode assemblies of Examples 2-29 and Comparative Examples 1-2 are the same as those of Example 1, except for the different experimental parameters (see Table 1).

[0118] The experimental parameters of the electrode assemblies of Examples 1-29 and Comparative Examples 1-2 of this application are shown in Table 1.

[0119] Table 1

[0120] " / " indicates no.

[0121] Testing and Analysis Under the same conditions, the batteries prepared in Examples 1-29 and Comparative Examples 1-2 were subjected to impedance testing, rate testing, and cycle performance testing. The specific testing methods are as follows: Battery impedance: The electrode assemblies of each embodiment and comparative example were assembled with the separator and negative electrode to form a single cell, i.e., positive electrode / separator / negative electrode. Their AC impedance spectra were measured on an electrochemical workstation with an AC voltage signal amplitude of 5mV and a test frequency range of 10. 6 -10 -1 Hz; Rate testing: The electrode components of each embodiment and comparative example are assembled with the separator and negative electrode sheet into a single cell, i.e., positive electrode / separator / negative electrode. The rate performance is tested using the Blue Battery Testing System. The capacity retention rate is tested at 1C, 2C, 3C, 4C and 5C respectively. Finally, the capacity retention rate at 5C rate is compared. Capacity retention at 5C rate = (Discharge capacity at 5C / Discharge capacity at 1C) × 100%; Cycle performance testing: The electrode assemblies of each embodiment and comparative example were assembled with the separator and negative electrode sheet into a single cell, i.e., positive electrode / separator / negative electrode. The Blue Battery testing system was used at 0.1 mA / cm². 2 Cyclic testing was performed at current density, and the capacity retention rate was recorded after 100 cycles. Capacity retention after 100 weeks = (Discharge capacity at week 100 / Discharge capacity at week 1) × 100%; The test results are shown in Table 2.

[0122] Table 2

[0123] As shown in Table 2, compared with the batteries of Comparative Examples 1-2, the batteries of Examples 1-29 exhibit superior cycle performance and rate performance. This is because the batteries of Examples 1-29 are manufactured using the electrode assembly provided by this invention. This electrode assembly includes a first layer obtained by in-situ polymerization and a second layer obtained by in-situ polymerization, with inert filler and active filler layered (for example, when the inert filler is in the first layer, the active filler is in the second layer; when the active filler is in the first layer, the inert filler is in the second layer). The inert filler improves the ionic conductivity at the interface between the active material particles and the electrolyte layer. After lithium ions continuously diffuse into the electrolyte layer through the interface phase, the active filler itself also plays a role in ionic conductivity, becoming a lithium ion permeation channel, which can ensure the uniformity of lithium ion transport in each layer, thereby further improving the conductivity of lithium ions in the solid electrolyte. Thus, through the interaction between the first and second layers, the impedance of the electrode assembly can be reduced, which is beneficial to improving the cycle performance and rate performance of the battery.

[0124] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," "some implementations," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0125] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an electrode assembly, characterized in that, include: The first filler, the first lithium salt, the first polymer monomer, the first crosslinking agent and the first initiator are mixed to obtain the first slurry; The first slurry is transferred onto the electrode, allowing it to enter the active material layer of the electrode. The first layer is obtained by in-situ polymerization under heating for the first time, wherein the active material layer includes active material. The second filler, the second lithium salt, the second polymer monomer, the second crosslinking agent, and the second initiator are mixed to obtain the second slurry; The second slurry is transferred onto the first layer, and then subjected to a second heating and in-situ polymerization to obtain the second layer, thus yielding the electrode assembly. The mass of the first filler is A, the mass of the first polymer monomer is B, the mass of the first crosslinking agent is C, and so on. The mass of the second filler is M, the mass of the second polymer monomer is F, and the mass of the second crosslinking agent is N, and so on. <M / (F+N)×100%≤30%, The electrode assembly includes: The first layer obtained by in-situ polymerization includes a first polymer, an active substance, and a first filler. The second layer is obtained by in-situ polymerization and is disposed on one side of the first layer. The second layer includes a second polymer and a second filler. Wherein, the first filler is an inert filler, and the second filler is an active filler, wherein the active filler includes lithium. The inert filler has a particle size of 10 nm to 500 nm; the active filler has a particle size of 0.5 μm to 5 μm. The crystallinity of the first polymer is 5%-30%; The inert filler includes Al2O3, TiO2, SiO2, ZrO2, BaTiO3, and SrBi4Ti4O. 15 At least one of carbon nanotubes, montmorillonite, and talc. The active filler includes Li 0.75 La 0.5 TiO3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li7La3Zr2O 12 Li 6.55 La3Zr2Ga 0.45 O 12 Li 2.8 Zn 0.6 GeO4, Li 3.25 Si 0.25 P 0.75 O4, Li 3.6 Ge 0.8 S 0.2 At least one of O4 and LiPON.

2. The method according to claim 1, characterized in that, The first polymer includes at least one of polymethyl methacrylate, polyethyl methacrylate, polyvinyl carbonate, polymethoxyethylene glycol acrylate, polyethylene glycol dimethacrylate, polyvinyl carbonate, polyethylene sulfite, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, and vinylidene fluoride hexafluoropropylene copolymer. The crystallinity of the second polymer is 8%-35%; The second polymer includes at least one of polymethyl methacrylate, polyethyl methacrylate, polyvinyl carbonate, polymethoxyethylene glycol acrylate, polyethylene glycol dimethacrylate, polyvinyl carbonate, polyethylene sulfite, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, and a copolymer of vinylidene fluoride and hexafluoropropylene. The first polymer and the second polymer are the same. The first layer includes a first lithium salt; 3. The method according to claim 1, characterized in that, The second layer includes a second lithium salt; The first lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBOB, and LiClO4; The second lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiBOB, and LiClO4; The active material includes a positive electrode active material; The electrode assembly further includes a current collector, with the first layer disposed on the surface of the current collector and the second layer disposed on the surface of the first layer away from the current collector. The thickness of the first layer is 25μm-130μm; 4. The method according to claim 1, characterized in that, The thickness of the second layer is 5μm-50μm. ​ 5. The method according to claim 1, characterized in that, The mass ratio of the first slurry to the second slurry is (5-20):(1-10); The molar concentration of the first lithium salt in the first slurry is 0.5 mol / L-2 mol / L; The molar concentration of the second lithium salt in the second slurry is 0.5 mol / L-2 mol / L; The mass ratio of the first polymer monomer to the first crosslinking agent is (10-20):(1-8); The mass ratio of the second polymer monomer to the second crosslinking agent is (10-20):(1-8).

6. The method according to claim 1, characterized in that, The first polymer monomer includes at least one of the following: methoxy polyethylene glycol acrylate, ethylene glycol dimethacrylate, methyl methacrylate, vinylene carbonate, vinyl sulfite, ethyl methacrylate, acrylonitrile, ethylene oxide, vinylidene fluoride, ethylene oxide, and vinylidene fluoride hexafluoropropylene blend monomers; The second polymer monomer includes at least one of the following: methoxy polyethylene glycol acrylate, ethylene glycol dimethacrylate, methyl methacrylate, vinylene carbonate, vinyl sulfite, ethyl methacrylate, acrylonitrile, ethylene oxide, vinylidene fluoride, ethylene oxide, and vinylidene fluoride hexafluoropropylene blend monomers; The first crosslinking agent includes at least one of polyethylene glycol diacrylate, glycidyl methacrylate, tetraethylene glycol dimethacrylate, and pentaerythritol tetraacrylate; The second crosslinking agent includes at least one of polyethylene glycol diacrylate, glycidyl methacrylate, tetraethylene glycol dimethacrylate, and pentaerythritol tetraacrylate; The first initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and dodecyl peroxide; The second initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and dodecyl peroxide.

7. The method according to claim 1, characterized in that, The temperature of the first heating is 45℃-100℃; The second heating temperature is 45℃-100℃; The duration of the first heating is 60s-600s; The second heating time is 60s-600s.

8. The method according to claim 1, characterized in that, The transfer method is at least one of spraying, dripping, coating, and screen printing.

9. A battery, characterized in that, The battery includes an electrode assembly manufactured using the method described in any one of claims 1-8.

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