Multifunctional graft polymer coated sulfide solid electrolyte and preparation method thereof
By constructing a polyionic liquid-grafted polymer interface layer on the surface of sulfide solid electrolyte particles, the problems of interfacial chemical instability and mechanical contact failure of sulfide solid electrolytes are solved, achieving efficient ion transport and improved battery safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-04-07
AI Technical Summary
Existing technologies have failed to construct a comprehensive interface layer on the surface of sulfide solid electrolyte particles that possesses strong binding force, high ionic conductivity, excellent mechanical flexibility, outstanding chemical/electrochemical stability, and the ability to intelligently respond and dynamically adjust according to the internal environment of the battery. This results in interfacial chemical instability, mechanical contact failure, and environmental sensitivity issues.
A smart interface layer, formed by grafting a polyionic liquid onto a polymer backbone, is constructed on the surface of sulfide solid electrolyte particles using chemical bonding grafting technology. The synergistic effect of the polymer backbone and the polyionic liquid creates a dynamically responsive ion transport path and an over-temperature protection mechanism.
It achieves improved interfacial chemical stability, mitigates mechanical contact failure, exhibits environmental responsiveness and electrochemical stability, dynamically adjusts ion transport pathways, and enhances battery cycle stability and safety.
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Figure CN121812700A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid-state battery technology and relates to a composite electrolyte for solid-state batteries and its preparation method. Specifically, it relates to a multifunctional grafted polymer-coated sulfide solid electrolyte and its preparation method, in order to improve the interface performance and safety of sulfide solid-state batteries. Background Technology
[0002] Solid-state batteries, as a representative of next-generation high-performance energy storage technology, eliminate the flammable and leak-prone organic liquid electrolytes found in traditional lithium-ion batteries, theoretically possessing higher energy density, intrinsic safety, and cycle life. Among numerous solid-state electrolyte material systems, sulfide solid-state electrolytes (such as Li) are... 10 GeP2S 12 Li6PS5Cl, etc., are known for their excellent lithium-ion conductivity (up to 10). -2 S cm -1 With a molecular weight (on the order of magnitude) comparable to liquid electrolytes and good mechanical ductility, it is considered one of the most promising candidate materials for application.
[0003] However, the industrial application of sulfide solid electrolytes still faces a series of severe interface science and engineering challenges, which constitute the core problem that this invention aims to solve:
[0004] 1. Interfacial Chemical Instability and Side Reactions: Sulfide electrolytes, especially those rich in phosphorus and sulfur, have narrow chemical windows and insufficient thermodynamic stability. When they come into direct contact with highly active lithium metal anodes, severe reduction reactions occur, generating a mixed conductive interfacial layer of electrons and ions, such as Li₂S and Li₃P. This not only continuously consumes active lithium and electrolyte, leading to a decrease in coulombic efficiency and capacity decay, but may also induce interfacial passivation, causing a sharp increase in ion transport impedance. Simultaneously, on the positive electrode side, sulfide electrolytes are detrimental to high-voltage oxide cathode materials (such as LiCoO₂ and LiNi). x Co y Mn 1-x-y O2 has poor oxidation resistance and is easily corroded by active oxygen or transition metal ions released from the cathode material during charging and discharging. More challenging is that in sulfur-based cathode systems (such as sulfur-carbon composite cathodes), soluble polysulfide intermediates can shuttle to the electrolyte side and undergo irreversible chemical reactions with the sulfide electrolyte, leading to electrolyte structure destruction and increased interfacial impedance.
[0005] 2. Interface Mechanical Contact Failure and Stress Adaptability Issues: During battery cycling, electrode materials (especially silicon-based or lithium metal anodes) undergo significant volume expansion and contraction. This periodic deformation generates enormous mechanical stress on rigid or brittle sulfide electrolyte particles, leading to microcracks or even breakage of the electrolyte and disrupting the integrity of ion conduction pathways. In traditional physically mixed or simply cold-pressed solid-state batteries, this solid-solid contact interface is extremely fragile and prone to contact failure during cycling, manifesting as a significant increase in battery internal resistance and rapid capacity decay.
[0006] 3. Environmental Sensitivity and Electrochemical Stability Limitations: Sulfide electrolytes are extremely sensitive to moisture. Even trace amounts of water vapor in the air can react with them, producing highly toxic H2S gas and causing electrolyte structural damage and loss of ionic conductivity. This places extremely stringent requirements on production processes and environmental control. Furthermore, under an electric field, anions in traditional polymer or liquid electrolytes migrate and polarize, undergoing reduction and decomposition at the negative electrode interface. The limited electrochemical stability window of sulfide electrolytes also restricts their compatibility with high-capacity electrode materials.
[0007] To address the above challenges, existing technologies have made various attempts:
[0008] 1. Physical Coating: An inert oxide (such as LiNbO3, Al2O3) is used to coat the surface of sulfide electrolyte particles to construct a physical barrier layer. Although this method can isolate side reactions to a certain extent, the bonding force between the coating layer and the electrolyte matrix is usually weak and it is easy to detach under mechanical stress; moreover, most inorganic coating layers have low ionic conductivity, which will introduce additional interfacial impedance.
[0009] 2. Polymer Composites: This approach combines sulfide electrolytes with flexible polymer electrolytes such as polyethylene oxide (PEO) to improve interfacial contact. However, these polymer matrices themselves exhibit low ionic conductivity (especially at room temperature) and poor stability against lithium metal; their wide electrochemical window is insufficient to suppress lithium dendrite growth. More importantly, the interfacial bonding of this physical blend is limited, and it lacks intelligent response capabilities, failing to dynamically adapt to complex operating conditions during battery operation.
[0010] 3. Interface Modification Layer: Introducing some functional intermediate layers. However, these layers often have a single function, either focusing solely on improving ion transport or solely on blocking side reactions, making it difficult to achieve multifunctional synergy. For example, a simple ion-conducting layer may not effectively prevent polysulfide shuttle; while a simple physical barrier layer will severely hinder lithium-ion transport.
[0011] In summary, existing technologies have not yet provided an ideal solution for constructing a comprehensive interface layer on the surface of sulfide solid electrolyte particles that possesses strong bonding, high ionic conductivity, excellent mechanical flexibility, outstanding chemical / electrochemical stability, and the ability to intelligently respond and dynamically adjust according to the internal battery environment (such as temperature and stress). Therefore, developing an innovative structure that can fundamentally and synergistically solve the aforementioned multiple interface problems has become a key bottleneck in promoting the practical application of sulfide-based all-solid-state batteries. This invention aims to fill this technological gap. Summary of the Invention
[0012] To overcome the shortcomings of existing technologies, this invention provides a multifunctional grafted polymer-coated sulfide solid electrolyte and its preparation method. This coating layer can enhance interfacial chemical stability, improve interfacial mechanical contact failure, and endow the electrolyte interface with a dynamically responsive and intelligently controlled capability.
[0013] To achieve the above objectives, the present invention adopts the following technical solution:
[0014] The core of this invention lies in constructing a "smart interface layer" on the surface of sulfide solid electrolyte particles using chemical bonding grafting technology. This "smart interface layer" is formed by grafting polyionic liquid onto a polymer backbone. By designing the functional groups of the ionic liquid monomer and the structure of the polymer backbone, the "smart interface layer" can influence the lithium-ion transport dynamics.
[0015] The multifunctional grafted polymer-coated sulfide solid electrolyte consists of sulfide solid electrolyte particles and a polymer layer coating its surface; the polymer layer is a grafted polymer formed by chemically grafting a polyionic liquid onto a polymer backbone.
[0016] Preferably, the chemical bond grafting is achieved through thermally initiated free radical polymerization, carboxyl-amino condensation, or epoxy-amino ring-opening reaction. These reaction pathways ensure that the polyionic liquid segments are firmly anchored to the polymer backbone in the form of covalent bonds, thereby enabling the entire coating layer to form a stable and durable bond with the sulfide electrolyte particle matrix, effectively avoiding the problem of peeling off under mechanical stress.
[0017] Preferably, the sulfide solid electrolyte is LiPS4, Li3PS4, Li6PS5Cl, or Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 These materials possess high intrinsic ionic conductivity, making them an ideal foundation for constructing high-performance all-solid-state batteries.
[0018] Preferably, the polymer backbone contains specific functional groups or structures, including one or more combinations of hydroxyl, amino, carboxyl groups, and unsaturated polymers containing carbon-carbon double bonds. The unsaturated polymers containing carbon-carbon double bonds include polyacrylic acid, polyethyleneimine, or modified polyethers with double bonds in their side chains. These functional groups serve as grafting sites, providing a chemical basis for the introduction of polyionic liquids. Simultaneously, the polymer backbone itself endows the coating layer with excellent flexibility and mechanical toughness to accommodate volume changes in the electrode during cycling.
[0019] Preferably, the polyionic liquid contains specific functional groups that can react with the polymer backbone, including one or more combinations of amino, carboxyl, isocyanate, epoxy, hydroxyl, and vinyl groups. Examples include 1-vinyl-3-alkylimidazolium salts and epoxy-containing quaternary ammonium salt ionic liquids. Through graft polymerization, the polyionic liquid provides a high concentration of directionally migratable lithium ion carriers for the interface layer.
[0020] Furthermore, the grafted polymer layer is endowed with environmental responsiveness. In terms of temperature response, it exhibits a "dynamic ion gate effect": when the battery temperature exceeds a safe threshold, the thermal motion of the polymer backbone intensifies, leading to the obstruction or closure of ion transport paths and a spontaneous decrease in ion conductivity, forming an inherent over-temperature protection mechanism. In terms of mechanical stress response, it exhibits a "stress-conductivity feedback" mechanism: when the interface is subjected to compressive stress generated by changes in electrode volume, the entanglement of the polymer backbone chains increases, and the ion channels are physically compressed, resulting in a momentary increase in local interface impedance. This impedance change spontaneously reduces local current density, inhibiting the growth of lithium dendrites. In summary, the grafted polymer layer can respond to temperature or mechanical stress changes during battery operation, dynamically adjusting its chain segment movement and ion transport paths, thereby altering its ion conductivity and achieving over-temperature self-protection and stress distribution regulation.
[0021] The present invention also provides a method for preparing the multifunctional grafted polymer-coated sulfide solid electrolyte, comprising the following steps:
[0022] S1: The polymer backbone and ionic liquid monomer are dissolved or dispersed together in an organic solvent to form a homogeneous solution A;
[0023] S2: Add sulfide solid electrolyte particles to solution A and mix thoroughly to form slurry B;
[0024] S3: The slurry B is heated or left to stand at room temperature to allow the ionic liquid monomer to undergo a graft polymerization reaction on the polymer backbone. At the same time, the graft polymer forms a coating layer on the surface of the sulfide particles through chemical reaction or strong physical interaction.
[0025] S4: Dry the treated slurry to obtain a multifunctional grafted polymer-coated sulfide solid electrolyte.
[0026] Furthermore, in step one, solution A also includes a necessary initiator or catalyst, wherein the initiator is benzoyl peroxide or azobisisobutyronitrile; and the catalyst is one of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) or N,N-dicyclohexylcarbodiimide (DCC). The mass of the initiator or catalyst is 0.1%-1% of the total mass of the polymer backbone, ionic liquid monomer, and sulfide solid electrolyte.
[0027] Furthermore, in step one, the mass ratio of the polymer backbone, ionic liquid monomer, and sulfide solid electrolyte is 1:0.8:10, and the amount of sulfide solid electrolyte added at one time is greater than 0.5g.
[0028] Furthermore, in step three, the heating temperature is 50℃-70℃, the time is 2-24 hours, and the standing time at room temperature is no less than 2 hours.
[0029] Compared with the prior art, the beneficial effects of the present invention are:
[0030] 1. A "smart interface layer" combining excellent flexibility (polymer backbone) and high ionic conductivity (polyionic liquid) is constructed on the surface of sulfide particles through a coating layer formed by chemical bonding grafting. The conformational relaxation of the polymer backbone segments and the fixed charge sites of the polyionic liquid work synergistically to form a dynamic gate. Under normal operating conditions, the ion channel is open, ensuring efficient conduction. When local overheating of the battery causes intensified movement of the polymer chain segments, the gate dynamically contracts, passively increasing the ion transport resistance and slowing down the reaction rate, thereby achieving an intrinsic over-temperature protection mechanism.
[0031] 2. Because the anions in polyionic liquids are fixed by covalent bonds, they cannot move in an electric field, thus avoiding their own reduction and decomposition, and reducing electrolyte consumption. Under the action of an electric field, these fixed anions form an extremely stable and uniformly distributed negative charge layer on the surface of sulfide electrolyte particles, electrostatically repelling harmful anions such as polysulfides, preventing them from directly contacting the electrolyte, and reducing chemical corrosion of the interface.
[0032] 3. When the negative electrode volume expansion exerts enormous pressure on the interface, the coating layer is compressed, the polymer chain entanglement increases, and the tortuosity of the ion transport path increases, leading to a momentary increase in local interfacial impedance. This change spontaneously reduces the current density in that region, providing more time for lithium ions to redistribute uniformly. Attached Figure Description
[0033] Figure 1This is a flowchart illustrating the preparation of a multifunctional grafted polymer-coated electrolyte.
[0034] Figure 2 This is a cycling diagram of the batteries prepared in Example 1 and Comparative Example 1 at 0.5 C. Detailed Implementation
[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0036] Example 1:
[0037] A method for preparing a multifunctional grafted polymer-coated sulfide solid electrolyte includes the following steps:
[0038] 1. At 80°C, 0.1 g of polyvinyl alcohol (PVA, a hydroxyl-containing polymer) was dissolved in 10 mL of anhydrous N-methylpyrrolidone, and then 0.08 g of isocyanate-functionalized 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt (NCO-IL TFSI) was added and stirred thoroughly to obtain solution A;
[0039] 2. Add 1.0 g of Li6PS5Cl sulfide solid electrolyte particles to solution A, and stir continuously for 2 h to obtain solution B.
[0040] 3. Under nitrogen protection, the reaction system was reacted at 60℃ for 4 h. During this process, the hydroxyl groups on the polymer backbone reacted with the isocyanate groups of the ionic liquid monomer to form urethane bonds, achieving chemical grafting. The grafted polymer was uniformly coated on the surface of the electrolyte particles.
[0041] 4. The slurry was cast into a film and vacuum dried at 60°C for 12 h to obtain a multifunctional grafted polymer-coated sulfide solid electrolyte film.
[0042] Example 2
[0043] A method for preparing a multifunctional grafted polymer-coated sulfide solid electrolyte includes the following steps:
[0044] 1. At 50°C, 0.1 g of hyperbranched polyethyleneimine (PEI, an amino-containing polymer) was dissolved in 10 mL of acetonitrile, and then 0.08 g of epoxy-functionalized 1-amino-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (Epoxy-ILTFSI) was added and stirred thoroughly to obtain solution A;
[0045] 2. Add 1.0 g Li to solution A 10 GeP2S 12 Sulfide solid electrolyte particles were stirred continuously for 2 hours to obtain solution B.
[0046] 3. Under nitrogen protection, the reaction system was reacted at 50℃ for 12 h. During this process, the primary amines on the polymer backbone undergo ring-opening reactions with the epoxy groups of the ionic liquid monomers to form CN bonds, achieving chemical grafting. The grafted polymer is uniformly coated on the surface of the electrolyte particles.
[0047] 4. The slurry is coated onto the substrate and vacuum dried at 60°C for 12 h to obtain a multifunctional grafted polymer-coated sulfide solid electrolyte powder.
[0048] Example 3
[0049] A method for preparing a multifunctional grafted polymer-coated sulfide solid electrolyte includes the following steps:
[0050] 1. Dissolve 0.1 g of polyacrylic acid (PAA, a carboxyl-containing polymer) in 10 mL of N-methylpyrrolidone, then add 0.08 g of amino-functionalized 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (NH2-IL TFSI) and 0.01 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) as catalysts, and stir thoroughly to obtain solution A;
[0051] 2. Add 1.0 g Li to solution A 10 GeP2S 12 Sulfide solid electrolyte particles were stirred continuously for 2 hours to obtain solution B.
[0052] 3. Under nitrogen protection, the reaction system was reacted at 30℃ for 24 h. During this process, the carboxyl groups on the polymer backbone undergo a condensation reaction with the amino groups of the ionic liquid monomer to form amide bonds, achieving chemical grafting. The grafted polymer is uniformly coated on the surface of the electrolyte particles.
[0053] 4. The slurry was cast into a film and vacuum dried at 60°C for 12 h to obtain a multifunctional grafted polymer-coated sulfide solid electrolyte film.
[0054] Example 4
[0055] A method for preparing a multifunctional grafted polymer-coated sulfide solid electrolyte includes the following steps:
[0056] 1. Dissolve 0.1 g of hydroxyl-terminated liquid polybutadiene-acrylonitrile copolymer (a polymer containing carbon-carbon double bonds) in 10 mL of tetrahydrofuran, then add 0.08 g of 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt (vinyl ILTFSI) and 0.005 g of azobisisobutyronitrile (AIBN) as initiators, and stir thoroughly to obtain solution A;
[0057] 2. Add 1.0 g of Li3PS4 sulfide solid electrolyte particles to solution A, and stir continuously for 2 h to obtain solution B.
[0058] 3. Under argon protection, the reaction system was reacted at 70℃ for 6 h. During this process, the free radicals generated by the decomposition of AIBN simultaneously initiated the polymerization of vinyl ionic liquids, and through the free radical copolymerization mechanism, reacted with the carbon-carbon double bonds on the polymer backbone to form carbon-carbon covalent bonds, realizing chemical grafting. The grafted polymer was uniformly coated on the surface of the electrolyte particles.
[0059] 4. The slurry is coated onto the substrate and vacuum dried at 60°C for 12 h to obtain a multifunctional grafted polymer-coated sulfide solid electrolyte powder.
[0060] Comparative Example 1
[0061] A method for preparing a sulfide solid electrolyte includes the following steps:
[0062] 1. Dissolve 0.1 g of polyvinyl alcohol (PVA) and 0.08 g of polymerized poly(1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide) (PIL TFSI) together in 10 mL of acetonitrile.
[0063] 2. Add 1.0g of Li6PS5Cl granules and stir until well mixed.
[0064] 3. The slurry was dried into a film under the same conditions as in Example 1.
[0065] 4. In the sample obtained in this comparative example, the polymer and ionic liquid were only physically mixed, and there were no chemical grafting bonds.
[0066] As attached Figure 2 As shown, solid-state batteries were assembled in solid-state battery molds using the electrolytes prepared in Example 1 and Comparative Example 1, respectively. The composite cathode used was LiNi9Co. 0.5 Mn 0.5 O2, Li 5.5 PS 4.5 Cl 1.5Conductive carbon black (VGCF) was ground at a mass ratio of 70:30:2, and the negative electrode was a micron-sized silicon electrode sheet. In an argon-filled glove box, 100 mg of solid electrolyte, 20 mg of composite positive electrode, and the silicon negative electrode sheet were assembled into a solid-state battery. A pressure of 360 MPa was applied and the mold was tightened. The battery was activated at 0.1 C for 3 cycles and then cycled at 0.5 C for testing. During battery cycling, as the internal temperature and internal resistance of the battery increased, the intelligent dynamic interface layer in Example 1 responded, adjusting the interface to adaptively enhance or weaken ion transport efficiency, resulting in a significant increase in cycle stability. However, in Comparative Example 1, the above effect did not occur, and its capacity continuously decreased, exhibiting poor stability.
[0067] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A multifunctional grafted polymer-coated sulfide solid electrolyte, characterized in that: The surface of the sulfide solid electrolyte is coated with a polymer layer, which is a grafted polymer formed by chemically bonding a polyionic liquid to a polymer backbone.
2. The multifunctional grafted polymer-coated sulfide solid electrolyte according to claim 1, characterized in that: The polymer backbone contains one or more combinations of hydroxyl, amino, carboxyl, and carbon-carbon double bonds.
3. The multifunctional grafted polymer-coated sulfide solid electrolyte according to claim 1, characterized in that: The polyionic liquid contains one or more combinations of amino, carboxyl, isocyanate, epoxy, hydroxyl, and vinyl groups.
4. The multifunctional grafted polymer-coated sulfide solid electrolyte according to claim 1, characterized in that: The sulfide solid electrolyte is LiPS4, Li3PS4, Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 10 GeP2S 12 One of them.
5. The multifunctional grafted polymer-coated sulfide solid electrolyte according to claim 1, characterized in that: The chemical bond grafting is achieved through thermally initiated free radical polymerization, carboxyl-amino condensation, or epoxy-amino ring-opening reaction.
6. A method for preparing a multifunctional grafted polymer-coated sulfide solid electrolyte according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Dissolve or disperse the polymer backbone and ionic liquid monomer uniformly in an organic solvent to form solution A; Step 2: Add the sulfide solid electrolyte particles to solution A and mix thoroughly to form slurry B; Step 3: Heat or allow the slurry B to stand at room temperature to allow the ionic liquid monomers to undergo graft polymerization on the polymer backbone, while forming a coating layer on the surface of the sulfide particles. Then, dry the slurry to obtain a multifunctional grafted polymer coated sulfide solid electrolyte.
7. The preparation method according to claim 6, characterized in that: In step one, the mass ratio of the polymer backbone, ionic liquid monomer, and sulfide solid electrolyte is 1:0.8:10, and the amount of sulfide solid electrolyte added at one time is greater than 0.5g.
8. The preparation method according to claim 6, characterized in that: In step one, solution A also includes an initiator or a catalyst, wherein the initiator is benzoyl peroxide or azobisisobutyronitrile; and the catalyst is one of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride or N,N-dicyclohexylcarbodiimide.
9. The preparation method according to claim 8, characterized in that: The mass of the initiator or catalyst is 0.1%-1% of the total mass of the polymer backbone, ionic liquid monomer, and sulfide solid electrolyte.
10. The preparation method according to claim 6, characterized in that: In step three, the heating temperature is 50℃-70℃, the time is 2-24 hours, and the standing time at room temperature is no less than 2 hours.