Composite binder and its use in sulfide all-solid-state lithium batteries

Abstract

The application provides a composite binder and application thereof in sulfide all-solid-state lithium batteries. The composite binder comprises an elastomer material and a polar polymer containing a polar functional group, wherein the weight ratio of the elastomer material to the polar polymer is (40:60) ‑ (60:40), preferably 50:50. The application also provides a method for preparing the composite binder, a sulfide solid electrolyte film comprising the composite binder, and a lithium battery silicon negative electrode and positive electrode. The application solves the technical problem that the binder is difficult to simultaneously meet the requirements of high mechanical stability and low interface ion transmission impedance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and more particularly to binders for sulfide all-solid-state lithium batteries. Specifically, it relates to a composite binder for sulfide all-solid-state lithium batteries and its application in sulfide all-solid-state lithium batteries. Background Technology

[0002] Sulfide-based all-solid-state lithium batteries are considered an important component of next-generation energy storage technology due to their high safety and high energy density. Lithium batteries mostly use traditional binders such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC).

[0003] However, the industrialization of sulfide all-solid-state lithium batteries faces the problem that the ion / electron contact network inside the electrode, especially at the solid-solid interface, is prone to failure during cycling.

[0004] Chinese invention patent CN 117844403 A discloses a binder for a composite electrode in solid-state lithium batteries. The solid-state battery positive electrode binder is prepared by mixing and dissolving one or more of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), hydrogenated nitrile butadiene rubber (HNBR), ethyl cellulose (EC), and styrene-butadiene rubber (SBR) with a solvent. The solvent is one or more of 4,6-dimethyl-2-heptanone (GT), anisole, butyl butyrate, isobutyl isobutyrate, and p-xylene. This invention improves upon commonly used solid-state battery binders by copolymerizing hexafluoropropylene (HFP) with the traditional binder polyvinylidene fluoride (PVDF) to obtain PVDF-HFP, and then preparing the composite positive electrode binder solution by stirring with a suitable solvent capable of dissolving it. However, it suffers from shortcomings in ionic conductivity and transport path, as well as mechanical properties.

[0005] Traditional binders have some application problems, such as poor interface compatibility and high solid-solid interface contact resistance; insufficient mechanical stability, and binder cracking caused by electrode volume changes during cycling, resulting in the shedding of active material; PVDF, CMC and other binders need to be dissolved in polar solvents, and sulfide electrolytes are incompatible with polar solvents and will react, making them unsuitable for sulfide all-solid-state lithium batteries.

[0006] There is currently no good solution to the above problems. Summary of the Invention

[0007] This application provides a modified composite polymer binder and its application in sulfide all-solid-state lithium batteries, so as to at least solve the technical problem that existing binders are unable to simultaneously meet the requirements of high mechanical stability and low interfacial ion transport impedance.

[0008] According to one aspect of the embodiments of this application, a composite adhesive is provided, comprising: an elastomeric material and a polar polymer, the polar polymer containing polar functional groups; wherein the weight ratio of the elastomeric material to the polar polymer is (40:60) - (60:40), preferably 50:50.

[0009] Further, the elastomer material is selected from hydrogenated nitrile butadiene rubber (HNBR), nitrile butadiene rubber (NBR), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene triblock copolymer (SIS), or combinations thereof; and / or the polar polymer is selected from polyacrylate polymers, polyvinylidene fluoride copolymers, polycarbonate polymers, polyethylene oxide, or combinations thereof, preferably polyacrylate polymers are selected from polymethyl methacrylate (PMMA), polymethyl methacrylate (PMA), polyethyl methacrylate, or combinations thereof, preferably polyvinylidene fluoride copolymers are selected from polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene (PVDF-TFE), or combinations thereof, preferably polycarbonate polymers are selected from polypropylene carbonate, polyvinyl carbonate, polytrimethylene carbonate, or combinations thereof.

[0010] According to another aspect of the embodiments of this application, a method for preparing a composite adhesive is also provided, comprising the following steps: blending an elastomer material with a polar polymer containing polar functional groups at a weight ratio of (40:60) - (60:40) to form a composite adhesive; preferably, the blending includes melt blending and solution blending, and more preferably, the blending is solution blending.

[0011] Further, solution blending includes the following steps: dissolving an elastomer material in a first solvent to form a first adhesive solution, dissolving a polar polymer containing polar functional groups in a second solvent to form a second adhesive solution, and blending the first adhesive solution and the second adhesive solution to form a composite adhesive solution.

[0012] Furthermore, the first solvent may be the same as or different from the second solvent, and is selected from anisole, butyl butyrate, ethyl acetate, isobutyl isobutyrate, or combinations thereof.

[0013] According to another aspect of the embodiments of this application, a sulfide solid electrolyte membrane is also provided, comprising: a sulfide solid electrolyte, and the composite binder described in this invention; wherein the weight of the composite binder is 0.5 wt% - 10 wt% based on the total weight of the sulfide solid electrolyte membrane.

[0014] Furthermore, the sulfide solid electrolyte is selected from:

[0015] A sulfide solid electrolyte of silver-germanium sulfide type, Li6PS5X, wherein X is Cl, Br or I;

[0016] Lithium germanium phosphorus sulfur oxide Li 10 GeP2S 12 ;

[0017] Thio-LISICON type Li 3+x Ge x P 1-x S4, where 0 < x < 1;

[0018] Li2S-P2S5-based glass ceramics;

[0019] Amorphous sulfide electrolytes;

[0020] Halogen-doped sulfide Li3PS4-X, where X is Cl or Br; or

[0021] Their combination.

[0022] Furthermore, the sulfide solid electrolyte membrane has a thickness of 5-750 μm, an impedance of 4-300 Ω, and an ionic conductivity of 0.1-10 mS / cm.

[0023] According to another aspect of the embodiments of this application, a lithium battery silicon anode is also provided, comprising the composite binder described in this invention; the weight of the composite binder is 0.5 wt% - 10 wt% based on the total weight of the lithium battery silicon anode; and preferably the silicon anode is selected from silicon-carbon composite anodes, pre-lithiated silicon-based anodes, nanostructured silicon anodes, or combinations thereof.

[0024] According to another aspect of the embodiments of this application, a lithium battery cathode is also provided, comprising the composite binder described in this invention; the weight of the composite binder is 0.5 wt% - 10 wt% based on the total weight of the lithium battery cathode; and preferably the cathode is selected from ternary cathode, lithium iron phosphate cathode, lithium-rich manganese cathode, lithium cobalt oxide cathode, lithium nickel manganese oxide cathode or a combination thereof.

[0025] In this embodiment, a composite binder comprising an elastomer material and a polar polymer containing polar functional groups in a specific weight ratio is provided. The elastomer material, as a binder component that provides mechanical properties, forms a continuous, highly elastic three-dimensional network (like "steel bars"), effectively absorbing and dispersing the stress generated by the volume change of the active material during charging and discharging, significantly suppressing the generation and propagation of electrode cracks, thereby ensuring the long-term integrity of the electrode structure and significantly improving the cycle life of the battery. In addition, the polar polymer component (like "high-performance cement") provides excellent interfacial compatibility. Its polar functional groups interact strongly with the surface of the sulfide electrolyte particles, significantly improving the compatibility of the binder / electrolyte interface, providing a low-impedance channel for the transport of lithium ions between sulfide electrolyte particles, effectively reducing battery polarization, and improving the rate performance and release capacity of the battery.

[0026] The composite binder of this invention is not a simple physical mixture, but rather provides a synergistic "rigid-flexible" structure. Through the interaction between molecular chains, a multiphase synergistic structure is formed, where the polymeric elastomer provides toughness and the polar polymer optimizes the interface. This structure overcomes the disadvantage of high interfacial impedance of pure elastomers and compensates for the insufficient mechanical strength of pure polar polymers, achieving a synergistic effect and thus solving the problem of electrode contact failure.

[0027] In addition, this composite binder system can be processed using a solution method, is highly compatible with existing electrode fabrication processes, requires no complex equipment, is easy to scale up for production, and has excellent prospects for commercial application. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This is a rate curve of a mold battery based on a positive electrode with a composite binder (HNBR / PMA) according to Embodiment 1 of this application;

[0030] Figure 2 This is an AC impedance diagram of a sulfide solid electrolyte membrane based on a composite binder (HNBR / PVDF-HFP) according to Example 5 of this application. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] As described in the background section, existing binders used in sulfide all-solid-state lithium batteries (ASSLB) have the problem of failing to simultaneously meet the requirements of mechanical and electrochemical performance. To solve the above technical problems, this application provides a composite binder comprising an elastomer material and a polar polymer. Through the synergistic effect of the two, the interfacial impedance is significantly reduced while maintaining the stability of the electrode structure, thereby improving the overall performance of the battery.

[0034] The present invention provides a composite adhesive comprising: an elastomer material and a polar polymer containing polar functional groups; wherein the weight ratio of the elastomer material to the polar polymer is (40:60) - (60:40), preferably 50:50.

[0035] In the composite binder of this invention, the elastomer material, as a binder component that provides mechanical properties, forms a continuous, highly elastic three-dimensional network (like "steel bars"), effectively absorbing and dispersing the stress generated by the volume change of the active material during charging and discharging, significantly suppressing the generation and propagation of electrode cracks, thereby ensuring the long-term integrity of the electrode structure and significantly improving the cycle life of the battery; the polar polymer component (like "high-performance cement") provides excellent interfacial compatibility, and its polar functional groups generate strong interactions with the surface of sulfide electrolyte particles, significantly improving the compatibility of the binder / electrolyte interface, providing a low-impedance channel for the transport of lithium ions between sulfide electrolyte particles, effectively reducing battery polarization, and improving the rate performance and release capacity of the battery.

[0036] Furthermore, this invention ensures a dynamic balance of functions between the elastomer and polar polymer by limiting the weight ratio of the elastomer to the polar polymer to (40:60) - (60:40), for example, 40:60, 50:60, 60:60, 50:50, 50:40, 60:50, and 60:40. When the weight ratio is below 40:60, the excessive polar component leads to system embrittlement and insufficient mechanical strength; when the weight ratio is above 60:40, the elastomer excessively weakens the ion conduction network. Within the weight ratio range of this invention, the composite binder exhibits optimal consistency in cycle life, rate performance, interfacial impedance, and other indicators, demonstrating excellent reproducibility and engineering reliability.

[0037] The elastomer material is selected from hydrogenated nitrile butadiene rubber (HNBR), nitrile butadiene rubber (NBR), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene triblock copolymer (SIS), or combinations thereof; and / or the polar polymer is selected from polyacrylate polymers, polyvinylidene fluoride copolymers, polycarbonate polymers, polyethylene oxide, or combinations thereof. Preferably, the polyacrylate polymer is selected from polymethyl methacrylate (PMMA), polymethyl methacrylate (PMA), polyethyl methacrylate, or combinations thereof. Preferably, the polyvinylidene fluoride copolymer is selected from polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene (PVDF-TFE), or combinations thereof. Preferably, the polycarbonate polymer is selected from polypropylene carbonate, polyvinyl carbonate, polytrimethylene carbonate, or combinations thereof.

[0038] The specific type of elastomer material within the scope of this invention can provide high elasticity and stress buffering, and the specific type of polar polymer within the scope of this invention can achieve low impedance interfacial conduction. The two work together to construct a "rigid-flexible" structure, which not only inhibits electrode cracking but also improves lithium-ion transport efficiency, and is compatible with non-polar solvents, avoiding the risk of sulfide decomposition, further extending cycle life and improving rate performance, achieving a dual breakthrough in performance and process.

[0039] This invention provides a method for preparing a composite adhesive, comprising the following steps: blending an elastomer material with a polar polymer containing polar functional groups at a weight ratio of (40:60) - (60:40) to form the composite adhesive; preferably, the blending includes melt blending and solution blending, more preferably, the blending is solution blending. For example, the blending weight ratios are 40:60, 50:60, 60:60, 50:50, 50:40, 60:50, and 60:40. This invention uses a specific weight ratio to blend an elastomer material with a polar polymer containing polar functional groups to prepare a composite adhesive. The process is simple and the conditions are mild, avoiding the damage to the elastomer structure caused by harsh conditions, ensuring that the polar polymer is uniformly dispersed in the elastomer network, thereby contributing to the construction of a "rigid-flexible synergistic" structure.

[0040] The solution blending process includes the following steps: dissolving the elastomer material in a first solvent to form a first adhesive solution; dissolving the polar polymer containing polar functional groups in a second solvent to form a second adhesive solution; and blending the first and second adhesive solutions to form a composite binder solution. This invention achieves uniform dispersion and structural synergy of the two components at the molecular scale through a stepwise dissolution process of the elastomer and polar polymer followed by mixing to form a composite binder solution. This method is controllable, highly reproducible, and directly adaptable to existing slurry coating production lines without equipment modification. It balances high performance with industrial feasibility, providing process support for the large-scale preparation of sulfide all-solid-state batteries.

[0041] The first solvent may be the same as or different from the second solvent, and is selected from anisole, butyl butyrate, ethyl acetate, isobutyl isobutyrate, or combinations thereof. Within the scope of this invention, the first and second solvents ensure the dissolution of the elastomer and polar polymer while avoiding the decomposition risk of sulfide electrolytes caused by traditional polar solvents (such as NMP and DMF). These solvents are chemically inert to the sulfide system, enabling safe processing without side reactions, gas generation, or interface degradation. Simultaneously, this solvent system is highly compatible with existing coating processes, offers fast drying speeds and low residue, improves production efficiency and yield, and enables the green, safe, and scalable preparation of high-performance binders, laying the technological foundation for the industrialization of sulfide all-solid-state batteries.

[0042] This invention provides a sulfide solid electrolyte membrane, comprising: a sulfide solid electrolyte, and the composite binder described in this invention; wherein, based on the total weight of the sulfide solid electrolyte membrane, the weight of the composite binder is 0.5 wt% - 10 wt%. For example, the weight of the composite binder is 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%. This invention introduces the composite binder into the sulfide solid electrolyte membrane, significantly improving the membrane's mechanical toughness and interfacial adhesion, and effectively suppressing cracking and delamination of the membrane during pressing and cycling. The amount of composite binder added within the scope of this invention can achieve synergistic effects: the elastomer component buffers stress, the polar polymer enhances the interfacial bonding between electrolyte particles, reduces interfacial impedance, and improves ionic conductivity, while avoiding excessive binder from clogging ion transport channels.

[0043] The sulfide solid electrolyte is selected from:

[0044] A sulfide solid electrolyte of silver-germanium sulfide type, Li6PS5X, wherein X is Cl, Br or I;

[0045] Lithium germanium phosphorus sulfur oxide Li 10 GeP2S 12 ;

[0046] Thio-LISICON type Li 3+x Ge x P 1-x S4, where 0 < x < 1;

[0047] Li2S-P2S5-based glass ceramics;

[0048] Amorphous sulfide electrolytes;

[0049] Halogen-doped sulfide Li3PS4-X, where X is Cl or Br; or

[0050] Their combination.

[0051] Within the scope of this invention, the sulfide solid electrolyte exhibits excellent chemical compatibility with the composite binder, preventing sulfide decomposition caused by solvents or polar functional groups and ensuring that the intrinsic high conductivity of the electrolyte remains intact. The binder constructs a stable, low-resistance ion transport network between electrolyte particles, significantly improving the mechanical integrity and interfacial contact of the membrane. This design enables the binder to achieve a synergistic effect of strong adhesion, low loss, and high stability without affecting ion conduction, further improving the preparation yield and cycle durability of the electrolyte membrane, and providing high energy density, long-life all-solid-state batteries.

[0052] The sulfide solid electrolyte membrane has a thickness of 5-750 μm, an impedance of 4-300 Ω, and an ionic conductivity of 0.1-10 mS / cm. For example, thicknesses of 5 μm, 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, and 750 μm are available. For example, impedance values ​​of 4 Ω, 10 Ω, 20 Ω, 50 Ω, 100 Ω, 150 Ω, 200 Ω, 250 Ω, and 300 Ω are available. For example, the ionic conductivity can be 0.1 mS / cm, 0.5 mS / cm, 1 mS / cm, 2 mS / cm, 3 mS / cm, 4 mS / cm, 5 mS / cm, 6 mS / cm, 7 mS / cm, 8 mS / cm, 9 mS / cm, 10 mS / cm, etc. The thickness, impedance, and ionic conductivity of the sulfide solid electrolyte membrane are within the scope of this invention, which can improve mechanical strength and provide low surface resistivity, further increasing the battery energy density. The binder constructs continuous ion channels at the interface, causing the impedance to increase non-linearly with thickness, ensuring high conductivity, thus providing key material support for the flexible design and industrial mass production of all-solid-state batteries.

[0053] This invention provides a silicon anode for lithium-ion batteries, comprising the composite binder described herein. Based on the total weight of the silicon anode, the weight of the composite binder is 0.5 wt% - 10 wt%. Preferably, the silicon anode is selected from silicon-carbon composite anodes, pre-lithiated silicon-based anodes, nanostructured silicon anodes, or combinations thereof. For example, the weight of the composite binder is 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, etc. The composite binder within the weight range of this invention, when applied to the silicon anode, significantly improves its cycle stability and interface integrity. The elastomeric components form a highly resilient network, effectively buffering the volume expansion of silicon materials and inhibiting particle pulverization and electrode cracking. The polar polymer forms a strong interaction with the silicon surface and SEI layer, stabilizing the interface and reducing charge transfer impedance. The composite binder of this invention is suitable for various high-capacity systems such as silicon-carbon composite anodes, pre-lithiated silicon-based anodes, and nanostructured silicon anodes. It is compatible with existing slurry processes, improves first-cycle efficiency and cycle life, and enables the silicon anode to maintain structural stability during long-cycle charge and discharge, providing material support for the practical application of high-energy-density lithium-ion batteries.

[0054] This invention provides a lithium battery cathode comprising the composite binder described herein. Based on the total weight of the lithium battery cathode, the weight of the composite binder is 0.5 wt% - 10 wt%. Preferably, the cathode is selected from ternary cathodes, lithium iron phosphate cathodes, lithium-rich manganese cathodes, lithium cobalt oxide cathodes, lithium nickel manganese oxide cathodes, or combinations thereof. For example, the weight of the composite binder is 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, etc. The composite binder within the weight range of this invention, when applied to cathode systems such as ternary cathodes, lithium iron phosphate cathodes, lithium-rich manganese cathodes, and lithium cobalt oxide cathodes, significantly improves electrode structural stability and interfacial ion transport efficiency. The elastomer component effectively mitigates electrode cracking during cathode cycling, while the polar polymer enhances the compatibility of the cathode / electrolyte interface, reduces interfacial impedance, and suppresses transition metal dissolution and side reactions. The lithium-ion battery cathode of this invention can significantly improve rate performance and cycle life, and is particularly suitable for high-voltage, high-energy-density cathode materials. It is compatible with traditional slurry processes, providing a universal, high-performance bonding solution for next-generation high-energy-density lithium-ion batteries.

[0055] 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.

[0056] Example 1: HNBR / PMA composite binder and its application in the positive electrode

[0057] Preparation of composite adhesive:

[0058] Hydrogenated nitrile butadiene rubber (HNBR) and polymethyl methacrylate (PMA) were blended at a weight ratio of 50:50. First, HNBR was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution A. Then, polymethyl methacrylate was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution B. Solution A and solution B were then mixed at a weight ratio of 1:1 to form composite solution C. The preparation process was carried out in a drying room with a dew point less than -40°C.

[0059] Preparation of positive electrode:

[0060] The ternary cathode active material (NCM811), sulfide solid electrolyte (Li6PS5Cl), conductive agent (VGCF), and composite binder (HNBR / PMA) were weighed in a weight ratio of 60:30:3:2 to prepare the cathode slurry. The cathode slurry was uniformly coated onto an aluminum foil current collector using a doctor blade. The coated electrode was then vacuum-dried at 80°C for 12 hours to thoroughly remove the solvent. The cathode was then rolled to achieve an areal capacity of 2.7 mAh / cm². 2 .

[0061] Assembly of all-solid-state batteries:

[0062] A mold battery was fabricated using the prepared positive electrode as the working electrode, a lithium-indium alloy as the counter electrode, and Li6PS5Cl as the solid electrolyte membrane layer, under a pressure of 400 MPa. The battery rate performance is as follows: Figure 1 As shown, the mold battery retained 93% of its capacity after 500 cycles at room temperature at a 0.5C rate.

[0063] Example 2: HNBR / PVDF-HFP composite binder and its application in the cathode

[0064] Preparation of composite adhesive:

[0065] Hydrogenated nitrile butadiene rubber (HNBR) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) were blended at a weight ratio of 50:50. First, the hydrogenated nitrile butadiene rubber (HNBR) was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution A. Then, the polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution B. Finally, solutions A and B were mixed at a weight ratio of 1:1 to form composite solution C. The preparation process was carried out in a drying room with a dew point less than -40°C.

[0066] Preparation of positive electrode:

[0067] The ternary cathode active material (NCM811), sulfide solid electrolyte (Li6PS5Cl), conductive agent (VGCF), and composite binder (HNBR / PVDF-HFP) were weighed in a weight ratio of 60:30:3:2 to prepare the cathode slurry. The cathode slurry was uniformly coated onto an aluminum foil current collector using a doctor blade. The coated electrode was then vacuum-dried at 80°C for 12 hours to thoroughly remove the solvent. The cathode was then rolled to achieve an areal capacity of 2.7 mAh / cm². 2 .

[0068] Assembly of all-solid-state batteries:

[0069] A mold battery was fabricated using the prepared positive electrode as the working electrode, a lithium-indium alloy as the counter electrode, and Li6PS5Cl as the solid electrolyte membrane layer under a pressure of 400 MPa. The initial coulombic efficiency of the battery was 90%. After 500 cycles at room temperature at 0.5C, the mold battery retained 91% of its capacity.

[0070] Example 3: HNBR / PVDF-CTFE composite binder and its application in the cathode

[0071] Preparation of composite adhesive:

[0072] Hydrogenated nitrile butadiene rubber (HNBR) and polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE) were blended at a weight ratio of 50:50. First, the hydrogenated nitrile butadiene rubber (HNBR) was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and heated and stirred to form compound A. Then, the polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE) was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and heated and stirred to form compound B. Compound A and compound B were then mixed at a weight ratio of 1:1 to form composite compound C. The preparation process was carried out in a drying room with a dew point less than -40°C.

[0073] Preparation of positive electrode:

[0074] The ternary cathode active material (NCM811), sulfide solid electrolyte (Li6PS5Cl), conductive agent (VGCF), and composite binder (HNBR / PVDF-CTFE) were weighed in a weight ratio of 60:30:3:2 to prepare the cathode slurry. The cathode slurry was uniformly coated onto an aluminum foil current collector using a doctor blade. The coated electrode was then vacuum-dried at 80°C for 12 hours to thoroughly remove the solvent. The cathode was then rolled to achieve an areal capacity of 2.7 mAh / cm². 2 .

[0075] Assembly of all-solid-state batteries:

[0076] Using the prepared positive electrode as the working electrode, lithium-indium alloy as the counter electrode, and Li6PS5Cl as the solid electrolyte membrane layer, a mold battery was fabricated under a pressure of 400 MPa. The mold battery retained 88% of its capacity after 500 cycles at room temperature at 0.5C.

[0077] Example 4: HNBR / PMMA composite binder and its application in the positive electrode

[0078] Preparation of composite adhesive:

[0079] Hydrogenated nitrile butadiene rubber (HNBR) and polymethyl methacrylate (PMMA) were blended at a weight ratio of 50:50. First, HNBR was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution A. Then, PMMA was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution B. Solution A and solution B were then mixed at a weight ratio of 1:1 to form composite solution C. The preparation process was carried out in a drying room with a dew point less than -40°C.

[0080] Positive electrode preparation:

[0081] The ternary cathode active material (NCM811), sulfide solid electrolyte (Li6PS5Cl), conductive agent (VGCF), and composite binder (HNBR / PMMA) were weighed in a weight ratio of 60:30:3:1 to prepare the cathode slurry. The cathode slurry was uniformly coated onto an aluminum foil current collector using a doctor blade. The coated electrode was then vacuum-dried at 80°C for 12 hours to thoroughly remove the solvent. The cathode was then rolled to achieve an areal capacity of 2.8 mAh / cm². 2 .

[0082] Assembly of all-solid-state batteries:

[0083] Using the prepared positive electrode as the working electrode, lithium-indium alloy as the counter electrode, and Li6PS5Cl as the solid electrolyte membrane layer, a mold battery was fabricated under a pressure of 400 MPa. The mold battery retained 90% of its capacity after 500 cycles at room temperature at 0.5C.

[0084] Example 5: HNBR / PVDF-HFP composite binder and its application in electrolyte membranes

[0085] Preparation of composite adhesive:

[0086] Hydrogenated nitrile butadiene rubber (HNBR) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) were blended at a weight ratio of 50:50. First, the hydrogenated nitrile butadiene rubber (HNBR) was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution A. Then, the polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) was dissolved in butyl butyrate solvent at a weight percentage of 5 wt%, and the mixture was heated and stirred to form solution B. Finally, solutions A and B were mixed at a weight ratio of 1:1 to form composite solution C. The preparation process was carried out in a drying room with a dew point less than -40°C.

[0087] Preparation of electrolyte membranes:

[0088] A Li6PS5Cl solid electrolyte with a weight ratio of 98:2 was mixed with the aforementioned composite binder (HNBR / PVDF-HFP) to prepare an electrolyte membrane slurry. The electrolyte slurry was then uniformly coated onto an aluminum foil current collector using a doctor blade. The coated electrolyte membrane was vacuum dried at 60°C for 12 hours to thoroughly remove the solvent. The thickness of the electrolyte membrane was 100 μm.

[0089] Testing of ionic conductivity of electrolyte membranes:

[0090] Multiple electrolyte membranes as described above were assembled into a mold battery to test the ionic conductivity. The mold battery assembly pressure was 400 MPa, and the test pressure was 200 MPa. The impedance EIS plot is shown below. Figure 2 As shown, the electrolyte membrane has a thickness of 730 μm, an impedance of 54 Ω, and an ionic conductivity of 1.79 mS / cm.

[0091] Example 6: HNBR / PMA Composite Binder and its Application in Positive Electrode

[0092] The preparation process was the same as in Example 1, except that the weight ratio of hydrogenated nitrile butadiene rubber (HNBR) to polymethyl methacrylate (PMA) was 60:40. The mold battery retained 89% of its capacity after 500 cycles at room temperature at 0.5C.

[0093] Example 7: HNBR / PMA Composite Binder and its Application in Positive Electrode

[0094] The preparation process was the same as in Example 1, except that the weight ratio of hydrogenated nitrile butadiene rubber (HNBR) to polymethyl methacrylate (PMA) was 40:60. The mold battery retained 87% of its capacity after 500 cycles at room temperature at 0.5C.

[0095] Comparative Example 1: SBR binder and its application in the positive electrode

[0096] The preparation process was the same as in Example 1, except that only SBR was used as the binder. The mold battery retained 72% of its capacity after 500 cycles at room temperature at 0.5C.

[0097] Comparative Example 2: Application of PVDF-HFP binder in positive electrode

[0098] The preparation process was the same as in Example 1, except that only PVDF-HFP was used as the binder. The mold battery retained 68% of its capacity after 500 cycles at room temperature at 0.5C.

[0099] Comparative Example 3: HNBR / PMA Composite Binder and its Application in the Positive Electrode

[0100] The preparation process was the same as in Example 1, except that the weight ratio of hydrogenated nitrile butadiene rubber (HNBR) to polymethyl methacrylate (PMA) was 65:35. The mold battery retained 78% of its capacity after 500 cycles at room temperature at 0.5C.

[0101] Comparative Example 4: HNBR / PMA Composite Binder and its Application in the Positive Electrode

[0102] The preparation process was the same as in Example 1, except that the weight ratio of hydrogenated nitrile butadiene rubber (HNBR) to polymethyl methacrylate (PMA) was 35:65. The mold battery retained 76% of its capacity after 500 cycles at room temperature at 0.5C.

[0103] Comparative Example 5: SBR / CMC Composite Binder and its Application in the Positive Electrode

[0104] The preparation process was the same as in Example 1, except that the weight ratio of styrene-butadiene rubber (SBR) to carboxymethyl cellulose (CMC) was 35:65. The mold battery retained 65% of its capacity after 500 cycles at room temperature at 0.5C.

[0105] Comparative Example 6: SBR / CMC Composite Binder and its Application in Electrolyte Membranes

[0106] The preparation process was the same as in Example 5, except that the weight ratio of styrene-butadiene rubber (SBR) to carboxymethyl cellulose (CMC) was 35:65. The electrolyte membrane had a thickness of 730 μm, an impedance of 120 Ω, and an ionic conductivity of 0.85 mS / cm.

[0107] Table 1

[0108]

[0109] As can be seen from the above description, Examples 1-7 of the present invention achieve a composite binder with strong mechanical stability and low interfacial ion transport impedance, resulting in a significant improvement in the cycle life of the sulfide all-solid-state battery electrode. In contrast, the binders of Comparative Examples 1-6, which are not within the scope of the present invention, have low mechanical stability and high interfacial ion transport impedance, resulting in a short cycle life of the sulfide all-solid-state battery electrode.

[0110] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A composite adhesive, characterized in that, Include: Elastomer materials, and A polar polymer containing polar functional groups; The weight ratio of the elastomer material to the polar polymer is (40:60) - (60:40), preferably 50:

50.

2. The composite adhesive according to claim 1, characterized in that, The elastomer material is selected from hydrogenated nitrile butadiene rubber (HNBR), nitrile butadiene rubber (NBR), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene triblock copolymer (SIS), or combinations thereof; and / or The polar polymer is selected from polyacrylate polymers, polyvinylidene fluoride copolymers, polycarbonate polymers, polyethylene oxide, or combinations thereof. Preferably, the polyacrylate polymer is selected from polymethyl methacrylate (PMMA), polymethyl methacrylate (PMA), polyethyl methacrylate, or combinations thereof. Preferably, the polyvinylidene fluoride copolymer is selected from polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene (PVDF-TFE), or combinations thereof. Preferably, the polycarbonate polymer is selected from polypropylene carbonate, polyvinyl carbonate, polytrimethylene carbonate, or combinations thereof.

3. A method for preparing a composite adhesive, characterized in that, Includes the following steps: The composite adhesive is formed by blending an elastomer material with a polar polymer containing polar functional groups in a weight ratio of (40:60) - (60:40). Preferably, the blending includes melt blending and solution blending, and more preferably, the blending is solution blending.

4. The method according to claim 3, characterized in that, The solution blending includes the following steps: The elastomer material is dissolved in a first solvent to form a first adhesive solution. A polar polymer containing polar functional groups is dissolved in a second solvent to form a second gel solution. The first adhesive solution and the second adhesive solution are mixed to form a composite adhesive solution.

5. The method according to claim 4, characterized in that, The first solvent may be the same as or different from the second solvent, and is selected from anisole, butyl butyrate, ethyl acetate, isobutyl isobutyrate, or combinations thereof.

6. A sulfide solid electrolyte membrane, characterized in that, Include: Sulfide solid electrolytes, and The composite adhesive according to claim 1 or 2; The weight of the composite binder is 0.5 wt% - 10 wt% based on the total weight of the sulfide solid electrolyte membrane.

7. The sulfide solid electrolyte membrane according to claim 6, characterized in that, The sulfide solid electrolyte is selected from: A sulfide solid electrolyte of silver-germanium sulfide type, Li6PS5X, wherein X is Cl, Br or I; Lithium germanium phosphorus sulfur oxide Li 10 GeP2S 12 ; Thio-LISICON type Li 3+x Ge x P 1-x S4, where 0 < x < 1; Li2S-P2S5-based glass ceramics; Amorphous sulfide electrolytes; Halogen-doped sulfide Li3PS4-X, where X is Cl or Br; or Their combination.

8. The sulfide solid electrolyte membrane according to claim 6, characterized in that, The sulfide solid electrolyte membrane has a thickness of 5-750 μm, an impedance of 4-300 Ω, and an ionic conductivity of 0.1-10 mS / cm.

9. A silicon anode for a lithium battery, characterized in that, It includes the composite adhesive as described in claim 1 or 2; Based on the total weight of the lithium-ion battery silicon anode, the weight of the composite binder is 0.5 wt% - 10 wt%; and Preferably, the silicon anode is selected from silicon-carbon composite anodes, pre-lithiated silicon-based anodes, nanostructured silicon anodes, or combinations thereof.

10. A lithium battery positive electrode, characterized in that, It includes the composite adhesive as described in claim 1 or 2; Based on the total weight of the lithium battery cathode, the weight of the composite binder is 0.5 wt% - 10 wt%; and Preferably, the positive electrode is selected from ternary positive electrode, lithium iron phosphate positive electrode, lithium-rich manganese positive electrode, lithium cobalt oxide positive electrode, lithium nickel manganese oxide positive electrode or a combination thereof.

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