Sulfide composite solid electrolyte and preparation method and application thereof

Abstract

The invention provides a sulfide composite solid-state electrolyte and a preparation method and application thereof, and relates to the technical field of solid-state batteries. Specifically, the method comprises the following steps: performing lithiation treatment on silk fibroin to obtain a lithiated silk fibroin aqueous solution; mixing the silk fibroin aqueous solution, a lithium salt and an ionic liquid to obtain a conductive ion precursor solution; and carrying out atomization treatment on the conductive ion precursor solution, spraying the atomized conductive ion precursor solution to the surfaces of sulfide electrolyte particles to form a coating layer, and then carrying out aging treatment to obtain the sulfide composite solid electrolyte with the core-shell structure. According to the invention, a coating layer which is high in toughness, high in conductivity, wide in window and capable of adsorbing H2S is designed on the surface of the sulfide electrolyte, so that the whole composite electrolyte has efficient interface transmission property and electrochemical stability, excellent mechanical property and processability and good application prospect.

Description

Technical Field

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

[0002] Sulfide solid electrolytes are considered the core material for all-solid-state batteries due to their ultra-high ionic conductivity; however, their industrialization process is severely constrained by the following three inherent pain points.

[0003] Firstly, there is poor solid-solid contact between rigid electrolyte particles. Because the surfaces of rigid particles are relatively rough, and it is difficult to achieve a tight, seamless fit between them, a large number of gaps exist between the particles. These gaps significantly hinder the transport path of lithium ions, making their migration within the electrolyte extremely difficult. During battery charging and discharging, lithium ions need to migrate rapidly and efficiently between the positive and negative electrodes to store and release energy. The obstructed ion transport caused by poor solid-solid contact significantly reduces ionic conductivity, thereby affecting the battery's charging and discharging efficiency and power performance, failing to meet the high energy density and high power output requirements of all-solid-state batteries.

[0004] Secondly, it releases hydrogen sulfide, a toxic gas, upon contact with air. Sulfide solid electrolytes are chemically reactive; when exposed to air, they react violently with moisture to release hydrogen sulfide. Hydrogen sulfide not only endangers the lives of production workers and increases safety costs for enterprises, but also requires specialized waste gas treatment equipment to handle the released toxic gases and meet environmental protection requirements. This undoubtedly increases the complexity and cost of production, limiting the large-scale industrial application of sulfide solid electrolytes.

[0005] Thirdly, solid electrolyte pressed films or sheets are highly brittle and easily broken. This brittleness makes the pressed material extremely prone to breakage under external forces, such as slight impacts, vibrations, or bending. During battery assembly, the solid electrolyte film / sheet needs to be precisely laminated and encapsulated with the positive and negative electrode materials. The brittle electrolyte film / sheet is easily broken due to improper handling during this process, leading to a significant increase in the scrap rate and production costs. Furthermore, during battery use, the battery may be subjected to various mechanical stresses, such as vehicle bumps and vibrations. The brittle electrolyte film / sheet cannot withstand these stresses and is prone to cracking, which can lead to internal short circuits and other safety issues, seriously affecting the battery's reliability and lifespan. This poses a significant challenge to the industrial application of sulfide solid electrolytes in all-solid-state batteries.

[0006] To improve interfacial contact defects, the "interfacial wetting" strategy is currently widely adopted. For example, patent CN119627199A uses ionic liquid electrowetting modification to prepare sulfide solid electrolytes, confining the ionic liquid BMIMPF6 within Li6PS5Cl sheets to improve the interfacial contact between the electrolyte and the electrode. However, its effect is mainly concentrated on the macroscopic interface between the electrolyte and the electrode, and it does not solve the solid-solid contact problem between sulfide electrolyte particles. Another example is patent CN120497426A, which uses rigid oxide coating to improve the electrolyte's air stability. However, its coating modulus >100 GPa is mismatched with the sulfide SSE (shear modulus ≈12 GPa), generating circumferential tensile stress during bending, leading to brittle fracture of the shell and a rebound in interfacial impedance. Yet another example is patent CN113782824A, which coats the electrolyte surface with polymers. Although this improves flexibility, polymers such as PEO freeze at room temperature, hindering ion transport and reducing the electrolyte's ionic conductivity.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The primary objective of this invention is to provide a method for preparing a sulfide composite solid electrolyte, which addresses the three core issues of interparticle interface, environmental stability, and bulk brittleness by starting with material and microstructure design. This invention provides an integrated electrolyte material that can construct efficient ion channels at the particle level and provide excellent mechanical toughness and air barrier properties, solving the multi-objective balance problem that cannot be overcome by a single material.

[0009] The second objective of this invention is to provide a sulfide composite solid electrolyte.

[0010] A third objective of this invention is to provide a solid-state battery.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for preparing a sulfide composite solid electrolyte includes the following steps: (1) Lithate the silk fibroin to obtain a lithiumized silk fibroin aqueous solution; (2) The silk fibroin aqueous solution, lithium salt and ionic liquid are mixed to obtain an ion-conducting precursor solution; (3) The ion-conducting precursor solution is atomized and sprayed onto the surface of sulfide electrolyte particles to form a coating layer, and then aged to obtain a core-shell structured sulfide composite solid electrolyte.

[0012] Preferably, the lithiation process includes: A mixture containing a lithium reagent and the silk fibroin was prepared, and after stirring, an aqueous solution of the lithium-ionized silk fibroin was obtained. The lithium-ionizing agent includes at least one of lithium hydroxide and lithium carbonate, and the mass ratio of the lithium-ionizing agent to the silk fibroin is 0.05~0.2:1.

[0013] Preferably, the concentration of the lithium-ionized silk fibroin aqueous solution is 3 wt.% to 8 wt.%.

[0014] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0015] Preferably, the ionic liquid comprises an ionic liquid of the imidazole cation and sulfonamide anion type.

[0016] Preferably, the concentration of the lithium salt in the ion-conducting precursor solution is 0.5 mol / L to 2 mol / L.

[0017] Preferably, the mass ratio of the ionic liquid to the silk fibroin aqueous solution is 2 to 4.

[0018] Preferably, the ion-conducting precursor solution further includes a co-solvent, which includes at least one of ethanol or dimethyl sulfoxide; More preferably, the mass ratio of the co-solvent to the ion-conducting precursor solution is 2 wt.% to 5 wt.%.

[0019] Preferably, the atomization process includes: The ion-conducting precursor solution is delivered to the ultrasonic nozzle via a delivery device, and the solution is sprayed out and formed into atomized droplets by ultrasonic atomization. More preferably, the feed rate of the solution is 1 mL / min to 3 mL / min, the atomization pressure is 0.8 bar to 1.2 bar, the ultrasonic frequency is 20 kHz to 40 kHz, and the ultrasonic power is 100 W / cm². 2 ~400W / cm 2 .

[0020] Preferably, the coating thickness in a single application is 100nm to 500nm, and the coating layer is obtained by several applications of the spraying process.

[0021] Preferably, the weight gain of the coated material compared to the sulfide electrolyte particles is 5 wt.% to 15 wt.% after the spraying.

[0022] A sulfide composite solid electrolyte is obtained by a preparation method comprising the aforementioned sulfide composite solid electrolyte; The sulfide composite solid electrolyte has a core-shell structure, wherein the core layer includes the sulfide electrolyte particles, and the shell layer includes a flexible interface layer composed of silk fibroin and ionic liquid.

[0023] A solid-state battery comprising the aforementioned sulfide composite solid electrolyte.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a novel composite electrolyte material and its preparation process that combine ion-conducting, flexible, and gas-barrier properties. It features a core-shell structure, and by constructing a flexible ion-conducting interface layer on the surface of each sulfide particle, soft contact between particles is achieved during molding, reducing electrode-electrolyte interface impedance at the microscopic level and solving interface contact problems. The dense core-shell structure provides a physical barrier for each particle, while the functional groups on the interface layer surface have chemical adsorption capacity for hydrogen sulfide, achieving a combination of active and passive hydrogen sulfide suppression. Furthermore, silk fibroin, a high-strength biopolymer, is used as the framework of the flexible phase, enhancing the flexibility and toughness of the electrolyte material and improving its processing performance for large-scale production of electrolyte membranes. Specifically, this invention has the following significant effects: (1) Synergistic Multiple Effects: This invention solves the three major technical problems of sulfide electrolytes simultaneously through the innovative design of the core-shell structure of electrolyte particles, especially the coating material, using silk fibroin (SF)-ionic liquid (IL) composite material; furthermore, in the spray coating stage, the dual induction mechanism of "ultrasonic atomization and low concentration alcohol" drives the hydrogen bond rearrangement between SF peptide chains, resulting in a β-sheet conformational change, forming a stable sheet cross-linked network as a protein secondary structure framework with both flexibility and rigidity. At the same time, the amide groups (-NH2) in SF can undergo acid-base neutralization reaction with H2S gas to achieve chemical adsorption; and the IL composite with SF acts as an ion-conducting phase to ensure Li + Conduction between electrolyte particles. This invention ingeniously integrates three functions—"flexible silk fibroin framework, ionic liquid ion-conducting phase, and active H2S gas protection"—on the surface of a sulfide electrolyte, forming a highly tough, highly conductive, wide-window interface coating layer capable of adsorbing H2S. This provides a novel material design path for constructing a rigid-flexible sulfide composite electrolyte.

[0025] (2) High efficiency and electrochemical stability of interfacial transport: During the subsequent pressing process of solid-state battery fabrication, the outer flexible SF / IL layer of the core-shell structure of this invention undergoes plastic deformation, seamlessly filling the interparticle gaps. This transforms discontinuous solid-solid point contacts into large-area, continuous surface contacts, constructing a hybrid ion transport network and significantly reducing grain boundary and interfacial impedance. Simultaneously, the wide electrochemical window of the SF / IL coating layer (0~5.5V vs. Li / Li) +It can fundamentally suppress harmful side reactions between sulfide electrolytes and high-voltage cathode materials, significantly improving the cycle life and coulombic efficiency of all-solid-state batteries.

[0026] (3) Excellent mechanical properties and processability of electrolyte membrane: The silk fibroin matrix rich in β-sheet structure has the intrinsic property of being "tough as silk" to construct a nanofiber network that can effectively disperse and absorb external stress. This helps to compress and extend brittle and fragile sulfide particles into a flexible composite electrolyte membrane, enabling it to withstand mechanical processing such as bending and winding. This lays the foundation for large-scale roll-to-roll production process and solid-state battery cell manufacturing.

[0027] (4) Excellent environmental tolerance and industrialization potential: The dense SF / IL composite interface layer can effectively physically isolate water vapor molecules, and the bioactive groups in the SF chain have a chemical adsorption effect on the trace amounts of H2S molecules that may be generated. Through the dual mechanism of passive barrier and active anchoring, the environmental stability of the material and the safety of production operations are significantly improved. Moreover, the preparation method of this invention is clear and simple, and the spray coating and other technologies used are mature and reliable, which are easy to realize and scale up in industrial production, and have broad prospects for industrial application. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] The first aspect of this invention is to provide a method for preparing a sulfide composite solid electrolyte, which mainly includes the following steps: (1) Lithate the silk fibroin to obtain a lithiumized silk fibroin aqueous solution; (2) The silk fibroin aqueous solution, lithium salt and ionic liquid are mixed to obtain an ion-conducting precursor solution; (3) The ion-conducting precursor solution is atomized and sprayed onto the surface of sulfide electrolyte particles to form a coating layer, and then aged to obtain a core-shell structured sulfide composite solid electrolyte.

[0030] For the sulfide composite solid electrolyte of the present invention: by constructing a shell composed of silk fibroin and ionic liquid on the surface of the sulfide electrolyte particles, this shell is a composite interface layer that combines ionic conductivity, mechanical flexibility and environmental barrier properties, thereby forming a core-shell structure composite particle of "rigid ionic conductor core - flexible ionic conductor shell".

[0031] (a) This invention achieves electrolyte toughening. Specifically, the ultrasonic atomization process of the silk fibroin (SF)-ionic liquid (IL) composite precursor solution used for coating during the spraying stage causes the SF peptide chain to undergo a β-sheet transition. That is, a large number of interchain hydrogen bonds are formed between the carbonyl oxygen atom on one peptide chain and the amide hydrogen atom on the adjacent peptide chain, thereby rearranging the SF peptide chain to form a stable and rigid sheet network with parallel or antiparallel connections, thus self-assembling to form a β-sheet crystal structure. As a type of protein secondary structure, the dense hydrogen bond network in the β-sheet causes the peptide chain to be arranged in a highly extended zigzag pattern, resulting in higher modulus (about 3 GPa) and mechanical strength, which is the core source of the mechanical properties of natural silk. The SF / IL coating layer designed in this invention disperses these rigid β-folded microcrystalline regions within a flexible ionic liquid amorphous matrix, forming a composite structure similar to reinforced concrete. The β-fold structure's modulus lies between that of the rigid sulfide electrolyte (SSE) and the soft IL phase, creating a gradient modulus. When the material is subjected to external forces, it can effectively disperse and transfer stress, and can also absorb a large amount of energy through its own fracture, thereby preventing microcrack propagation. This greatly enhances the toughness and mechanical strength of the electrolyte material, transforming it from brittle to flexible. Furthermore, the rigid framework provided by the β-fold network for the IL also prevents the IL from accumulating or being lost due to long-term cycling, maintaining a continuous ion pathway.

[0032] (b) This invention achieves low interfacial impedance and a wide electrochemical window. Specifically, in the SF / IL@SSE core-shell composite electrolyte of this invention, Li + It can conduct rapidly both within the sulfide core particles and within the continuous SF / IL phase of the coating layer. The SF / IL phase seamlessly connects the individual SSE particles, eliminating traditional grain boundary barriers and thus achieving lower interfacial impedance. For the selection of ionic liquids, imidazole cations and sulfonylimide anions or fluoride anions, which have wide electrochemical windows, high stability, and numerous hydrogen bond acceptor sites (facilitating connection with the SF backbone), are chosen, giving the composite solid electrolyte of this invention a >5V vs. Li / Li ratio. + The electrochemical window.

[0033] (c) This invention improves air stability and safety. Specifically, the dense SF-IL gel coating layer has extremely low gas permeability and strong hydrophobicity, forming a physical barrier to effectively prevent water molecules from penetrating the core. Meanwhile, the polar groups such as amides (-NH2) and hydroxyl groups (-OH) abundant on the silk fibroin peptide chains can undergo acid-base neutralization reactions with H2S molecules, thereby capturing trace amounts of H2S that may be generated during the use of sulfide electrolytes in solid-state batteries, providing active safety protection. This synergistic protection mechanism greatly improves the air stability of the sulfide electrolyte material and the safety of actual production operations.

[0034] As a preferred embodiment, the silk fibroin of the present invention can be purchased through commercial channels or prepared by oneself; the preparation of the silk fibroin can be achieved through core steps such as degumming, dissolving, purification and concentration, and can be prepared by various methods under different dissolution systems or operating conditions.

[0035] As a more preferred embodiment, the degumming includes, but is not limited to, alkaline methods, boiling water methods, soaping methods, organic acid methods, and enzymatic methods. In some embodiments, the degumming is carried out by alkaline methods, specifically including: cutting silkworm cocoons to a suitable volume and then treating them in a boiling sodium carbonate solution.

[0036] In a more preferred embodiment, the dissolving process includes the following method: placing the degummed silk fibroin fibers into a high-concentration lithium bromide solution and dissolving them under heat treatment for a certain period of time; in some embodiments, the concentration of the lithium bromide solution is 8 mol / L to 15 mol / L, the heat treatment temperature is 50℃ to 70℃, and the dissolving time is 3h to 6h.

[0037] As a more preferred embodiment, the purification and concentration include, but are not limited to, filtration, centrifugation, ultrafiltration, and one or more combinations of membrane concentration and dialysis concentration.

[0038] In a preferred embodiment, the lithiation treatment includes the following steps: preparing a mixture containing a lithiation reagent and the silk fibroin, and after stirring, obtaining the lithated silk fibroin aqueous solution; in some embodiments, the lithiation reagent includes at least one of lithium hydroxide and lithium carbonate, the mass ratio of the lithiation reagent to the silk fibroin is 0.05~0.2:1, and the mass of the silk fibroin should be based on its solid mass (or dry weight).

[0039] In a preferred embodiment, the concentration of the lithium-ionized silk fibroin aqueous solution is 3 wt.% to 8 wt.%.

[0040] In a preferred embodiment, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or lithium bis(trifluoromethanesulfonyl)imide (LiFSI), more preferably lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0041] In a preferred embodiment, the ionic liquid includes ionic liquids of the type of imidazole cation and sulfonamide anion, wherein the imidazole cation includes, but is not limited to, alkyl imidazoles such as 1-methylimidazolium and 1-ethyl-3-methylimidazolium, and the sulfonamide anion includes, but is not limited to, bis(trifluoromethanesulfonyl)imide anion or bis(fluorosulfonyl)imide anion, more preferably 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0042] In a preferred embodiment, the concentration of the lithium salt in the ion-conducting precursor solution is 0.5 mol / L to 2 mol / L.

[0043] In a preferred embodiment, the mass ratio of the ionic liquid to the silk fibroin aqueous solution is 2 to 4.

[0044] In a preferred embodiment, the ion-conducting precursor solution further includes a co-solvent, which includes at least one of ethanol and dimethyl sulfoxide; in some embodiments, the mass ratio of the co-solvent to the ion-conducting precursor solution is 2 wt.% to 5 wt.%.

[0045] As a preferred embodiment, the mixing in step (2) can be assisted by methods such as oscillation, stirring, shaking, centrifugation, ultrasound, or heating, which helps to accelerate dispersion and obtain a relatively uniform dispersion system. In some embodiments, the mixing is carried out by mechanical stirring at a speed of 50 rpm to 700 rpm for a duration of 8 h to 20 h.

[0046] As a preferred embodiment, step (2) is carried out under a protective gas, including but not limited to nitrogen, helium, neon, argon, etc.; in some embodiments, it is carried out in a glove box, and the oxygen or moisture content of the gas environment is <0.1ppm.

[0047] In a preferred embodiment, the sulfide electrolyte particles include Li6PS5X and Li 5.4 PS 4.4 X 1.6 Li 10 GeP2S 12 Li7P3S 11 At least one of the following, where X is one of Cl, Br, and I.

[0048] In a preferred embodiment, the particle size of the sulfide electrolyte particles should be maintained at D. 50 The particle size is between 1.0 μm and 10 μm. In some embodiments, the sulfide electrolyte particles are obtained by pulverization or fluidization to achieve a specific particle size.

[0049] In a preferred embodiment, the atomization process includes: a conveying device delivering the ion-conducting precursor solution to an ultrasonic nozzle, and using ultrasonic atomization to spray the solution and form atomized droplets; in some embodiments, the feed rate of the solution is 1 mL / min to 3 mL / min, the atomization pressure is 0.8 bar to 1.2 bar, the ultrasonic frequency is 20 kHz to 40 kHz, and the ultrasonic power is 100 W / cm². 2 ~400W / cm 2 .

[0050] As a preferred embodiment, the atomization treatment and the spraying in step (3) can be carried out by fluidized bed coating method, that is, the process technology of using airflow to suspend solid particles to form a fluidized state and achieving surface coating by spraying coating liquid. The equipment used includes, but is not limited to, top spray fluidized bed, bottom spray fluidized bed, side spray fluidized bed, etc.

[0051] In a preferred embodiment, the coating thickness of a single spray is 100 nm to 500 nm. In some embodiments, the desired coating thickness is achieved by repeated spraying 2 to 8 times. In some embodiments, the weight gain of the coated material compared to the sulfide electrolyte particles is 5 wt.% to 15 wt.% after spraying.

[0052] As a preferred embodiment, the aging process includes: standing in a glove box protective atmosphere for 20 to 30 hours.

[0053] A second aspect of the present invention is to provide a sulfide composite solid electrolyte prepared based on the first aspect. For the core-shell structured sulfide composite solid electrolyte, the core layer comprises the sulfide electrolyte particles, and the shell layer comprises a flexible interface layer obtained by combining silk fibroin and an ionic liquid.

[0054] In a preferred embodiment, the ionic conductivity of the sulfide composite solid electrolyte is not less than 1×10⁻⁶ at 20℃~30℃. -3 S / cm.

[0055] Understandably, the silk fibroin backbone rich in β-sheet structures provides the sulfide electrolyte core layer with excellent flexibility and toughness, preventing the initiation and propagation of cracks and improving its processing performance; the dense silk fibroin dry gel network structure in the shell layer effectively blocks environmental water molecules by encapsulating the electrolyte particles, while the functional groups on the protein peptide chains can also form chemical adsorption of hydrogen sulfide gas, effectively improving the electrolyte's air stability; the ionic liquid provides a wide electrochemical window for the electrolyte to further prevent adverse side reactions of the electrolyte, and as a flexible ion-conducting phase, it connects the lithium ion transport pathway between electrolyte particles, reducing interfacial impedance.

[0056] A third aspect of the present invention is to provide a solid-state battery comprising a sulfide composite solid electrolyte as described in the second aspect.

[0057] It is understood that, apart from the sulfide composite solid electrolyte, the solid battery should include positive and negative electrodes, as well as other necessary or non-necessary functional elements or packaging components, which can be arbitrarily selected and combined by those skilled in the art; when the solid battery includes the sulfide composite solid electrolyte of the present invention, regardless of whether other conventional or unconventional solid electrolytes are used in the solid battery, it can be regarded as an embodiment of the present invention.

[0058] Example 1 S1. Cut silkworm cocoons into small pieces and boil them in a boiling 0.02M sodium carbonate aqueous solution for 30 minutes to remove sericin. Rinse repeatedly with deionized water and dry to obtain pure silk fibroin. Dissolve the silk fibroin in a 9.3M LiBr aqueous solution and stir at 60°C until completely dissolved. Transfer the solution to a regenerated cellulose dialysis bag and dialyze with deionized water for 72 hours, changing the water every 8 hours to completely remove LiBr. Centrifuge the dialyzed silk fibroin aqueous solution at 9000 rpm for 20 minutes to remove insoluble matter, obtaining a clear solution with a concentration of 5 wt%. Then, add a molar equivalent of LiOH to the solution in the form of a 1.2 mol / L aqueous solution. The molar equivalent is determined by the molar amount of carboxyl functional groups on the amino acid chain of the silk fibroin that can be replaced by lithium ions. In this example, each gram of silk fibroin contains 0.04 mmol of carboxyl groups. After adding, stir to perform lithiation treatment to obtain a lithium-ionized silk fibroin solution.

[0059] S2. Take 20.0g of lithium-ionized silk fibroin solution and 40.0g of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, then add 1.0M LiTFSI and mix thoroughly. Add 1.8g of anhydrous ethanol as a co-solvent and stir magnetically for 12h to form a homogeneous SF / IL composite ion-conducting precursor solution.

[0060] S3, Weigh 10.0g of sulfide solid electrolyte Li 5.4 PS 4.4 Cl 1.6 The powder (particle size D50 = 5.0 μm) was dried in an argon-atmosphere glove box at 60°C in a vacuum oven for 12 h. Subsequently, the dried powder was fed into the hopper of a fluidized bed coating machine. The fluidized bed inlet temperature was set to 50°C, the atomization pressure to 1.0 bar, the precursor solution feed rate to 2.0 mL / min, and the ultrasonic atomizer was activated at a frequency of 28 kHz and a power density of 200 W / cm³. 2 The equipment was started for coating. After all the precursor solution was sprayed, fluidized drying continued for 30 minutes. The resulting powder was then aged in a glove box for 24 hours to obtain the core-shell composite powder of this embodiment. The coating weight gain was 10.2 wt.%.

[0061] Example 2 The process is essentially the same as in Example 1, except that in step S2, the amount of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt added is 60.0 g. In this example, the coating weight gain was 10.5 wt.%.

[0062] Example 3 The process is essentially the same as in Example 1, except that in step S2, the amount of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt added is 80.0 g. In this example, the coating weight gain was 10.8 wt.%.

[0063] Example 4 This example is essentially the same as Example 1, except that in step S2, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is replaced with 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. In this example, the coating weight gain was 9.9 wt.%.

[0064] Example 5 The process is essentially the same as in Example 1, except that in step S3, the solution feed rate is 1.0 mL / min. In this example, the coating weight gain was measured to be 5.5 wt.%.

[0065] Example 6 The process is essentially the same as in Example 1, except that in step S3, the solution feed rate is 3.0 mL / min. In this example, the coating weight gain was 14.6 wt.%.

[0066] Example 7 The process is basically the same as in Example 1, except that in step S3, Li is... 5.4 PS 4.4 Cl 1.6Powder replaced with D 50 Li particle size 10 GeP2S 12 In this embodiment, the coating weight gain was 9.8 wt.%.

[0067] Example 8 The process is essentially the same as in Example 1, except that in step S2, the amount of anhydrous ethanol added is 3.0 g. In this example, the coating weight gain was 10.3 wt.%.

[0068] Comparative Example 1 Weigh 10.0g of sulfide solid electrolyte Li 5.4 PS 4.4 Cl 1.6 The powder (particle size D50 = 5.0 μm) was dried in an argon atmosphere glove box in a vacuum oven at 60°C for 12 h.

[0069] Comparative Example 2 The process is essentially the same as in Example 1, except that step S2 is omitted, and the lithium-ionized silk fibroin solution obtained in S1 is used instead of the precursor solution for fluidized bed feeding in S3. In this comparative example, the coating weight gain was 10.1 wt.%.

[0070] Comparative Example 3 The results were essentially the same as in Example 1, except that step S1 was omitted, and the addition of lithium-ionized silk fibroin solution to obtain the precursor solution was omitted in step S2. In this comparative example, the coating weight gain was 9.7 wt.%.

[0071] Comparative Example 4 It is basically the same as Example 1, except that the aging process in step S3 is omitted.

[0072] Test case (1) Ionic conductivity test, the method is as follows: Weigh 200mg of solid electrolyte of each example and comparative example, pour it into the mold, manually rotate it until it is uniform and flat, apply pressure of 108MPa, and hold the pressure for 1min; use a micrometer to measure the thickness of the pressed electrolyte sheet and record the data; place the small mold into the metal kit, apply pressure of 216MPa, and tighten the 3 knobs on the kit; use an electrochemical workstation to test the impedance of the mold battery and record the electrolyte resistance, which is recorded in Table 1.

[0073] (2) Interfacial impedance test, the method is as follows: Weigh 100mg of solid electrolyte of each example and comparative example, pour it into the mold, manually rotate it until it is uniform and flat, apply pressure of 108MPa, and hold the pressure for 1min; cut two lithium foils with a diameter of 10mm and a thickness of 50μm, place them on the positive and negative electrode sides respectively, apply pressure of 36MPa on each side, hold the pressure for 30s, and assemble the Li|SF@IL-SSE|Li symmetric cell; place the small mold in the metal kit, apply pressure of 216MPa, and tighten the 3 knobs on the kit; test the impedance of the mold battery with an electrochemical workstation and record it in Table 1.

[0074] (3) Electrolyte fatigue resistance test, the method is as follows: the change of polarization voltage during the cycling process of solid electrolyte membrane is used to characterize its electrochemical fatigue resistance; the Li|SF@IL-SSE|Li symmetric cells corresponding to each embodiment or comparative example are assembled in the manner of experimental example (2); the current is set to 0.1mA / cm 2 A constant current charge and discharge cycle lasting 30 minutes constitutes one cycle. The voltage difference between the charging and discharging ends, ΔV = |E|, is recorded for the 100th cycle. charge E discharge |

[0075] (4) Hydrogen sulfide accumulation test, the method is as follows: (4.1) Weigh 200 mg of solid electrolytes from each example or comparative example and place them in a 50 mL polytetrafluoroethylene container. Introduce 10 mL of 0.5 M Pb(CH3COO)2 absorption solution into the headspace. After 24 h, remove the absorption solution and measure its absorbance using a UV-Vis spectrophotometer. (4.2) Based on the reaction equation of hydrogen sulfide with Pb(CH3COO)2, the strong absorption peak of PbS colloidal particles at 320 nm, and the absorbance and S 2- The principle that absorbance is directly proportional to mass concentration applies to absorbance A. S2- With respect to the mass concentration of sulfide ions C S2- There is a linear relationship between them. This relationship (slope) can be calculated using a Na₂S standard solution, yielding the formula A for their relationship. S2- =k·C S2- +b, in this example, k is taken as 0.385 L·mg -1 ·cm -1 b is 0.008; (4.3) Read the absorbance data at 320 nm after the absorbent has adsorbed hydrogen sulfide for 24 hours. S2- Substituting into the formula from the previous step, we get C. S2- The calculated H2S release amount (ppm) = C S2- The volume of the absorption liquid is recorded in Table 1.

[0076] Table 1

[0077] As shown in Table 1, the solid electrolytes prepared in the embodiments of the present invention all exhibited lower interfacial impedance, lower cyclic polarization voltage, and lower hydrogen sulfide accumulation. In contrast, Comparative Example 1 (original sulfide) had the highest interfacial impedance, significantly increasing the polarization voltage, which was detrimental to long-term battery cycling, and the hydrogen sulfide accumulation was an order of magnitude higher than that of the embodiments. Comparative Example 2 (silk fibroin coating only) also increased the polarization voltage due to the lack of ionic phase connection between particles. Comparative Example 3 (ionic liquid treatment only) was difficult to anchor due to the lack of skeletal support, making it prone to migration under cyclic stress and electric field. The effective thickness also decreased with each cycle, and the interfacial point contacts were re-exposed. After 100 cycles, the polarization voltage also increased, and because there was no SF phase that could actively absorb hydrogen sulfide, it was difficult to provide protection against the gas.

[0078] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a sulfide composite solid electrolyte, characterized in that, Includes the following steps: (1) Lithate the silk fibroin to obtain a lithiumized silk fibroin aqueous solution; (2) The silk fibroin aqueous solution, lithium salt and ionic liquid are mixed to obtain an ion-conducting precursor solution; (3) The ion-conducting precursor solution is atomized and sprayed onto the surface of sulfide electrolyte particles to form a coating layer, and then aged to obtain a core-shell structured sulfide composite solid electrolyte.

2. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, The lithiation process includes: A mixture containing a lithium reagent and the silk fibroin was prepared, and after stirring, an aqueous solution of the lithium-ionized silk fibroin was obtained. The lithium-ionizing agent includes at least one of lithium hydroxide and lithium carbonate, and the mass ratio of the lithium-ionizing agent to the silk fibroin is 0.05~0.2:

1.

3. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, The concentration of the lithium-ionized silk fibroin aqueous solution is 3 wt.% to 8 wt.%.

4. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. And / or, the ionic liquid includes ionic liquids of the imidazole cation and sulfonamide anion types.

5. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, In the ion-conducting precursor solution, the concentration of the lithium salt is 0.5 mol / L to 2 mol / L; And / or, the mass ratio of the ionic liquid to the silk fibroin aqueous solution is 2 to 4.

6. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, The ion-conducting precursor solution also includes a co-solvent, which includes at least one of ethanol or dimethyl sulfoxide. Preferably, the mass ratio of the co-solvent to the ion-conducting precursor solution is 2 wt.% to 5 wt.%.

7. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, The atomization process includes: The ion-conducting precursor solution is delivered to the ultrasonic nozzle via a delivery device, and the solution is sprayed out and formed into atomized droplets by ultrasonic atomization. Preferably, the feed rate of the solution is 1 mL / min to 3 mL / min, the atomization pressure is 0.8 bar to 1.2 bar, the ultrasonic frequency is 20 kHz to 40 kHz, and the ultrasonic power is 100 W / cm². 2 ~400W / cm 2 .

8. The method for preparing the sulfide composite solid electrolyte according to claim 1, characterized in that, The coating thickness in a single application is 100nm~500nm, and the coating layer is obtained by several applications of the spraying process. And / or, through the spraying, the weight gain of the coated material relative to the sulfide electrolyte particles is 5 wt.% to 15 wt.%.

9. A sulfide composite solid electrolyte, characterized in that, The electrolyte is obtained by a method comprising the preparation of a sulfide composite solid electrolyte as described in any one of claims 1 to 8; The sulfide composite solid electrolyte has a core-shell structure, wherein the core layer includes the sulfide electrolyte particles, and the shell layer includes a flexible interface layer composed of silk fibroin and ionic liquid.

10. A solid-state battery, characterized in that, Including the sulfide composite solid electrolyte as described in claim 9.

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