A lithiophilic polymer microsphere, a preparation method thereof and an application thereof

Abstract

The present invention discloses a lithiumophilic polymer microsphere and its preparation method and application. The lithiumophilic polymer microsphere is composed of a lithiumophilic polymer matrix and a sulfide electrolyte coated inside it. The lithiumophilic polymer is preferably selected from modified poly(ethylene oxide) (PEO), and its lithiumophilicity is improved by methods such as lithium salt doping or copolymerization with lithium-containing monomers. The sulfide electrolyte is preferably selected from argyrodite-type electrolytes. The preparation method of the lithiumophilic polymer is also disclosed. In the present invention, the solvent evaporation method is combined with an oil-in-oil (O / O) emulsion system to prepare microspheres, realizing the effective encapsulation of the sulfide electrolyte. The prepared lithiumophilic polymer microspheres are used in all-solid-state lithium metal batteries, which can have good ionic conductivity and electrochemical stability, and can effectively improve the interfacial contact and cycling performance of all-solid-state lithium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state lithium batteries, and particularly to a lithiumophilic polymer microsphere, a preparation method thereof, and an application thereof. Background Art

[0002] All-solid-state batteries are considered promising candidates for next-generation energy storage technologies due to their potential high energy density and safety. Among them, sulfide solid electrolytes have received extensive attention due to their high ionic conductivity, good mechanical ductility, and ease of processing. However, problems such as poor interfacial contact between sulfide electrolytes and electrodes and air sensitivity limit their applications. Poor interfacial contact is an important reason for the increase in ionic transport impedance and the decline in cycling performance. In response to the solid-solid interfacial contact problem, researchers have proposed a variety of improvement strategies, mainly including the following aspects:

[0003] Interface modification: By chemically or physically modifying the interface, such as surface modification, doping, etc., to improve the compatibility and ionic transport performance between interfaces.

[0004] Film preparation: Using thin-film technology to prepare an intermediate layer at the interface, such as a buffer layer, a conductive layer, etc., to optimize interfacial contact and reduce impedance.

[0005] In-situ curing: Through methods such as in-situ polymerization and curing, a good interfacial contact between the solid electrolyte and the electrode is directly formed during the battery assembly process.

[0006] These methods can improve interfacial contact to a certain extent and have achieved some research results. However, these methods also generally have some problems, mainly reflected in:

[0007] Complex preparation process: Many methods require complex preparation steps and strict process control, making it difficult to achieve simplicity and standardization.

[0008] High cost: Some methods require the use of expensive materials or equipment, resulting in high manufacturing costs.

[0009] Difficult to mass-produce: Due to factors such as process complexity and cost, these methods are difficult to apply to large-scale industrial production.

[0010] These problems limit the value of these methods in practical applications. Therefore, developing simpler, more economical, and mass-producible interface improvement strategies is one of the important research directions in the current field of solid-state batteries. Summary of the Invention

[0011] The object of the present invention is to provide a lithiumophilic polymer microsphere, its preparation method and application. The microsphere can effectively encapsulate the sulfide electrolyte, improve the interfacial contact, and enhance the electrochemical performance of the battery, aiming to overcome the problem of practical application limitations existing in the traditional method of improving interfacial contact by applying pressure. The polymer microsphere shows great potential in improving the interfacial contact of solid-state batteries. Specifically, the polymer microsphere can improve the contact angle problem between the sulfide electrolyte and the negative electrode through the following mechanisms: on the one hand, the microsphere-coated electrolyte can achieve a more uniform interface, and the microsphere encapsulation can make the electrolyte distribute more uniformly on the electrode surface, forming a more uniform interfacial contact; on the other hand, the microsphere encapsulation can achieve a more effective ion transport channel, and the lithiumophilic polymer can construct a more effective ion transport channel to improve the ionic conductivity; furthermore, the microsphere encapsulation can achieve better interfacial stability, and the physical isolation effect of the microsphere can better inhibit interfacial side reactions.

[0012] The method of encapsulating the sulfide electrolyte with the polymer microsphere proposed by the present invention can significantly enhance the electrochemical performance of all-solid-state batteries and make it closer to the requirements of practical applications by improving interfacial contact, increasing ion transport efficiency, and inhibiting side reactions. This method provides an effective solution to the key problems in the development of all-solid-state batteries. The microsphere-coated electrolyte of the present invention can still maintain more than 90% of the capacity after 500 cycles when applied to all-solid-state lithium metal batteries, and the cycle life is increased by about 1000%.

[0013] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0014] In the first aspect, the present invention provides a lithiumophilic polymer microsphere, which includes a lithiumophilic polymer matrix and a sulfide electrolyte encapsulated in the lithiumophilic polymer matrix.

[0015] In the present invention, the "lithiumophilic polymer" refers to a class of polymer materials, which are characterized by having a strong affinity for lithium ions (Li + ), or lithium metal, being able to promote the transport of lithium ions, and improving the interfacial compatibility between the polymer and the lithium metal negative electrode. The "lithiumophilicity" is mainly reflected in the lithium ion coordination ability: the polymer structure contains functional groups capable of coordinating with lithium ions, such as ether bonds (-O-), nitrogen atoms (-N-), sulfur atoms (-S-), etc. Through the coordination effect, the interaction between the polymer and lithium ions is enhanced, promoting the dissolution and dissociation of lithium salts, and improving the lithium ion conductivity.

[0016] As some specific embodiments of the present invention, the lithiumophilic polymer matrix is selected from at least one of polyether polymers, nitrogen-containing polymers, sulfur-containing polymers, and modified poly(ethylene oxide).

[0017] Further, the modified polyethylene oxide is polyethylene oxide modified by doping with a lithium salt or polyethylene oxide (PEO) modified by copolymerization with a lithium-containing monomer.

[0018] As some specific embodiments of the present invention, the polyether polymer is selected from at least one of polyoxymethylene, phenolic epoxy resin, and polytetrahydrofuran.

[0019] As some specific embodiments of the present invention, the nitrogen-containing polymer is selected from at least one of polyaniline, polyvinylpyrrolidone, and polyethyleneimine.

[0020] As some specific embodiments of the present invention, the sulfur-containing polymer is selected from at least one of polyphenylene sulfide, polyethersulfone, and polythiophene.

[0021] As some specific embodiments of the present invention, the lithium salt in the polyethylene oxide modified by doping with a lithium salt is selected from at least one of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0022] As some specific embodiments of the present invention, in the polyethylene oxide modified by doping with a lithium salt, based on the ethylene oxide repeating unit (EO) and lithium ion (Li + ), the EO / Li + molar ratio is 5:1 - 50:1, preferably 10:1 - 30:1, and more preferably 20:1.

[0023] As some specific embodiments of the present invention, the polyethylene oxide modified by doping with a lithium salt is obtained by separately dissolving the lithium salt and polyethylene oxide in an organic solvent to prepare a lithium salt solution and a polyethylene oxide solution, and then slowly dropping the lithium salt solution into the polyethylene oxide solution under vigorous stirring; the mass-volume fraction of the polyethylene oxide solution is 1% - 20% (w / v), preferably 5% - 10% (w / v); the volume ratio of the polyethylene oxide solution to the lithium salt solution is 1:1 - 10:1, preferably 2:1 - 5:1.

[0024] As some specific embodiments of the present invention, the lithium-containing monomer in the polyethylene oxide modified by copolymerization with a lithium-containing monomer is selected from at least one of lithiated acrylate, lithiated methacrylate, and lithium-containing vinyl monomer.

[0025] In some specific embodiments of the present invention, the lithium-containing monomer copolymer-modified polyethylene oxide is obtained by dissolving polyethylene oxide, a lithium-containing monomer, and an initiator in an organic solvent and heating them under the protection of an inert atmosphere for a polymerization reaction; the mass ratio of the polyethylene oxide, the lithium-containing monomer, and the initiator is 10 - 50:1:0.02 - 0.1.

[0026] In some specific embodiments of the present invention, the initiator is selected from at least one of azobisisoheptonitrile, azobis(2-methylbutyronitrile), and azobisisobutyronitrile.

[0027] In some specific embodiments of the present invention, the lithiumophilic polymer matrix is a lithium-containing monomer copolymer-modified polyethylene oxide, and the mass ratio of the lithium-containing monomer copolymer-modified polyethylene oxide to the sulfide electrolyte is 2:1 - 10:1, preferably 3:1 - 5:1.

[0028] In some specific embodiments of the present invention, the sulfide electrolyte is selected from at least one of Li3PS4, Li 10 GeP2S 12 , and thiogermanate-type electrolytes (Li6PS5X), where X is selected from any one of Cl, Br, and I. The sulfide electrolyte is preferably the thiogermanate-type electrolyte Li6PS5Cl.

[0029] In some specific embodiments of the present invention, the median particle size D 50 = 300 - 500 nm of the sulfide electrolyte. Preferably, D 50 = 500 nm.

[0030] In some specific embodiments of the present invention, the average particle size of the polymer microspheres is 1 μm - 10 μm.

[0031] The average particle size of the microspheres has a significant impact on the performance of all-solid-state lithium metal batteries, especially in the system where polymer microspheres are used to coat sulfide electrolytes. The particle size is directly related to interface contact, ion transport, electrode structure, and the overall performance of the battery. When the particle size is too large, the following problems will occur: Larger microspheres will lead to a reduction in the interface contact area, fewer contact points between the electrode and the solid electrolyte, and an increase in interface impedance. This will hinder the effective transport of lithium ions, reducing the ionic conductivity and rate performance of the battery. Larger microspheres mean that lithium ions need to travel a longer distance to move between the electrode and the electrolyte, increasing the resistance of ion transport and reducing the ionic conductivity. Larger microspheres are difficult to uniformly fill the electrode pores, resulting in an uneven electrode structure, forming uneven local current density, and easily triggering the growth of lithium dendrites, affecting the cycle life and safety of the battery. When the particle size is too small, the following problems will occur: Nanoscale microspheres have a huge surface area and high surface energy, and are prone to agglomeration, forming larger aggregates, which instead leads to poor interface contact and an increase in ion transport resistance. Preparing nanoscale microspheres usually requires more precise process control, such as higher shear force, a more stable emulsion system, etc., increasing the preparation difficulty and cost. Nanoscale microspheres have a larger specific surface area and are more likely to undergo side reactions with electrode materials or other components, reducing the electrochemical stability of the battery. Uniformly dispersing nanoscale microspheres into the electrode or electrolyte is a challenge, and uneven dispersion will lead to local performance differences, affecting the overall performance of the battery.

[0032] In a second aspect, the present invention provides a method for preparing the lithiophilic polymer microspheres as described in any one of the above, comprising the following steps:

[0033] S1. Dissolve the lithiophilic polymer in an oil-phase solvent to form an oil phase;

[0034] S2. Disperse the sulfide electrolyte in a dispersion-phase solvent to form a dispersion phase;

[0035] S3. Slowly add the dispersion phase of step S2 to the oil phase of step S1 under vigorous stirring to form an emulsion by emulsification;

[0036] S4. Volatilize the solvent in the emulsion to form microspheres; obtain them after washing and drying.

[0037] As some specific embodiments of the present invention, in step S1, the oil-phase solvent is selected from at least one of dichloromethane (DCM), chloroform (CHCl3), carbon tetrachloride (CCl4), n-hexane, and cyclohexane.

[0038] As some specific embodiments of the present invention, in step S2, the dispersion-phase solvent is selected from at least one of acetonitrile (ACN), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF).

[0039] In some specific embodiments of the present invention, in step S2, in the dispersion phase, the mass-volume ratio of the sulfide electrolyte to the dispersion phase solvent is 1:50 - 1:200, preferably 1:80 - 1:120.

[0040] In some specific embodiments of the present invention, in step S3, the rotation speed of the vigorous stirring is 600 - 1000 rpm.

[0041] In some specific embodiments of the present invention, in step S3, the emulsification is carried out by high-shear dispersion or ultrasonic homogenization, and the formed emulsion is an oil-in-oil (O / O) emulsion.

[0042] In some specific embodiments of the present invention, the rotation speed of the high-shear dispersion is 6000 - 11000 rpm, and the time is 10 - 60 min;

[0043] and / or, the power of the ultrasonic homogenization is 100 - 400 W, the time is 5 - 30 min, and the ultrasonic homogenization is carried out in an intermittent manner, with each ultrasonic wave for 3 - 10 S and stopping for 2 - 5 S.

[0044] In a third aspect, the present invention provides a all-solid-state lithium metal battery, including a battery positive electrode and a negative electrode, and the lithiophilic polymer microspheres described in any one of the above as the electrolyte of the all-solid-state lithium metal battery.

[0045] In some specific embodiments of the present invention, the battery positive electrode is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganate, lithium manganese phosphate, lithium titanate, lithium nickelate, and lithium manganate.

[0046] In some specific embodiments of the present invention, the material of the battery negative electrode is lithium metal and an alloy, and the alloy is an alloy formed by lithium and at least one of Al, Sn, Si, Mg, and Zn.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1) There are often problems of poor interfacial contact between traditional solid electrolytes (such as ceramics or sulfides) and electrode materials, resulting in an increase in ion transport impedance and affecting the performance of the battery. By preparing the electrode / electrolyte layer by methods such as pressing or coating, this simple mixing method is difficult to form effective interfacial contact, and voids and cracks are likely to appear at the solid-solid interface. The present invention uses lithiophilic polymer microspheres to coat the sulfide electrolyte. Utilizing the flexibility and plasticity of the polymer, it can better fill the voids between electrode materials, increase the contact area, improve the interfacial wettability, thereby significantly reducing the interfacial impedance and promoting the effective transport of lithium ions. The spherical structure of the microspheres is also beneficial to form a more uniform distribution inside the electrode and improve the interfacial uniformity.

[0049] 2) The ionic conductivity of traditional solid electrolytes is relatively low, especially at room temperature, which limits the rate performance and energy density of the battery. Poor interfacial contact further exacerbates the hindrance of ion transport. The polar groups (such as ether bonds, amide groups, etc.) in the lithium-philic polymer of the present invention can have weak interactions with lithium ions, providing more ion transport channels and promoting the migration of lithium ions. By constructing microspheres, a continuous ion transport network can be formed between the electrode and the electrolyte, reducing the ion transport barrier at the interface and improving the overall ionic conductivity. The flexibility of the polymer can buffer the volume change of the electrode during charge and discharge, reducing interfacial stress concentration and crack generation, thus maintaining a stable ion transport channel.

[0050] 3) Sulfide electrolytes in the prior art are prone to react with moisture and oxygen in the air, resulting in performance degradation. At the same time, when in contact with the lithium metal anode, interfacial side reactions may also occur, affecting the cycle life of the battery. The polymer microspheres of the present invention can play a certain physical isolation role, reducing the direct contact between the sulfide electrolyte and the air and electrode materials, thereby inhibiting the occurrence of side reactions and improving the electrochemical stability and cycle life of the battery. Description of the Drawings

[0051] Other features, objectives, and advantages of the present invention will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0052] Figure 1 Cycling performance graph of the microsphere-coated sulfide electrolyte of Example 1 applied to all-solid-state lithium metal;

[0053] Figure 2 Coulombic efficiency graph of the microsphere-coated sulfide electrolyte of Example 1 applied to all-solid-state lithium metal battery;

[0054] Figure 3 Cycling performance comparison graph of the all-solid-state lithium metal battery of Example 1 and Comparative Example 1 of the present invention;

[0055] Figure 4 Schematic structural diagram of the microsphere-coated sulfide electrolyte of the present invention;

[0056] Figure 5 Transmission electron microscope (TEM) graph of the microsphere-coated sulfide electrolyte of Example 1;

[0057] Figure 6 Scanning electron microscope (SEM) graph of the microsphere-aggregated electrolyte of Comparative Example 6. Detailed Embodiments

[0058] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0059] Example 1

[0060] This example provides a polymer microsphere of a lithium salt-doped PEO-coated sulfide electrolyte. The sulfide electrolyte used in this example is the argyrodite-type electrolyte Li6PS5Cl (purchased from Ganfeng Lithium Industry), the lithiumophilic polymer matrix is polyethylene oxide modified with a lithium salt, polyethylene oxide PEO (Mw = 400 g / mol, purchased from Sigma-Aldrich), the lithium salt LiTFSI (purchased from Sigma-Aldrich), the oil-phase solvent is dichloromethane (DCM) (purchased from Sinopharm Group), and the dispersed-phase solvent is acetonitrile (ACN) (purchased from Sinopharm Group).

[0061] All operations involving lithium salts in this example need to be carried out in a glove box filled with argon or nitrogen to avoid the reaction of lithium salts with moisture and oxygen in the air. The preparation method of this example specifically includes the following steps:

[0062] 1. Solution preparation:

[0063] (1) Polyethylene oxide (PEO) solution: At room temperature, 1.0 g of PEO was dissolved in 10 mL of DCM to prepare a 10% (w / v) solution. Use a magnetic stirrer to stir for at least 2 hours until the PEO is completely dissolved to form a uniform and transparent solution, which is the PEO solution.

[0064] (2) Lithium salt solution: In this example, the doping ratio of polyethylene oxide (PEO) to lithium salt (LiTFSI) is based on the molar ratio of ethylene oxide repeating units (EO) to lithium ions (Li + ) and is set to EO / Li + = 20:1. In the glove box, 0.326 g of LiTFSI was dissolved in 5 mL of ACN. Use a magnetic stirrer to stir for at least 30 minutes until the LiTFSI is completely dissolved.

[0065] (3) Sulfide electrolyte dispersion: In the glove box, 0.2 g of the sulfide electrolyte Li6PS5Cl was dispersed in 20 mL of ACN (mass-volume ratio Li6PS5Cl:ACN = 1:100), and it was uniformly dispersed by ultrasonic treatment.

[0066] 2. Preparation of an emulsion of lithiumophilic polymer microspheres (performed in a glove box):

[0067] (1) Preparation of lithium salt-modified poly(ethylene oxide): Under vigorous stirring at 600 rpm on a magnetic stirrer, slowly (1 - 2 drops per second) add the ACN solution of the lithium salt to the DCM solution of PEO using a syringe, controlling the dropping rate to avoid forming overly large droplets.

[0068] (2) Mixing the oil phase and the dispersed phase: Continuing under vigorous stirring at 600 rpm on a magnetic stirrer, slowly (1 - 2 drops per second) add the sulfide electrolyte dispersion to the reaction solution from the previous step using a syringe. Similarly, control the dropping rate to avoid forming overly large droplets.

[0069] (3) Emulsification: Use a high-shear disperser (IKA Ultra-Turrax T25) to perform emulsification to obtain an emulsion. Set the rotation speed of the dispersing head to 8000 rpm and the emulsification time to 30 minutes.

[0070] 3. Microsphere curing:

[0071] (1) Preliminary curing: Transfer the emulsion to an open beaker and slowly stir overnight (about 12 hours) at 300 rpm using a magnetic stirrer at room temperature to allow the slow evaporation of DCM. To better control the evaporation rate, this can be carried out in a fume hood and the ventilation volume can be appropriately controlled.

[0072] (2) Complete curing: Transfer the preliminarily cured microspheres to a vacuum drying oven and vacuum dry at 40 °C for 24 hours to remove the residual ACN. This step needs to be carried out in a glove box to prevent the lithium salt from reacting with moisture in the air.

[0073] 4. Washing and collection (carried out in a glove box):

[0074] (1) Washing: In the glove box, wash the microspheres 3 times with dry diethyl ether, using 10 mL of diethyl ether each time. Disperse the microspheres in diethyl ether, stir for 10 minutes, then centrifuge (centrifuge at 3000 rpm for 5 minutes), pour off the supernatant, and repeat this step 3 times.

[0075] (2) Collection: Vacuum dry the washed microspheres (average particle size of 5 μm) in the glove box for at least 12 hours, and then store them in the glove box for later use.

[0076] Figure 5 is the transmission electron microscope image of the polymer microspheres prepared in Example 1. It can be seen that the sulfide electrolyte is coated in the lithiumophilic polymer matrix. The schematic structural diagram of the polymer microspheres coated with the sulfide electrolyte formed in the present invention is as Figure 4 shown.

[0077] Example 2

[0078] This example provides a polymer microsphere with a lithium-containing monomer copolymerized PEO-coated sulfide electrolyte. The sulfide electrolyte used in this example is the argyrodite-type electrolyte Li6PS5Cl (purchased from Yili Technology). The lithiumophilic polymer matrix is poly(ethylene oxide) copolymerized and modified with a lithium-containing monomer. The polymer matrix is PEO (Mw = 400 g / mol, purchased from Sigma-Aldrich). The lithium-containing monomer is lithium methacrylate (LiMAA), an acrylate monomer containing lithium (purchased from Macklin, CAS: 13234-23-6). The copolymerization initiator is AIBN (azobisisobutyronitrile) (purchased from Sigma-Aldrich). The oil-phase solvent is dichloromethane (DCM) (purchased from Sinopharm Chemical Reagent Co., Ltd.). The dispersion-phase solvent is acetonitrile (CAN) (purchased from Sinopharm Chemical Reagent Co., Ltd.).

[0079] All operations in this example need to be carried out in a glove box filled with argon or nitrogen to avoid the reaction of the electrolyte with moisture and oxygen in the air. The preparation method of this example specifically includes the following steps:

[0080] 1. Preparation of poly(ethylene oxide) copolymerized and modified with a lithium-containing monomer by copolymerization reaction:

[0081] Dissolve PEO, the lithium-containing monomer, and the copolymerization initiator in the solvent N-methylpyrrolidone (NMP) according to the mass ratio of PEO:LiMAA:AIBN = 10:1:0.1. Weigh 1.0 g of PEO, 0.1 g of LiMAA, 0.01 g of AIBN, and 10 mL of NMP. Add the weighed PEO to NMP and stir to dissolve at room temperature. Then, under stirring conditions, slowly add LiMAA and AIBN. After ensuring that all substances are completely dissolved, place the reaction flask in an oil bath or heating mantle and heat to 65 °C (the decomposition temperature of AIBN) under the protection of nitrogen or argon for polymerization reaction. The reaction time is 12 hours.

[0082] After the reaction is completed, purify it through steps such as precipitation, washing, and drying to obtain a lithium-containing copolymer. The specific operations are as follows:

[0083] (1) Precipitation: Under vigorous stirring (stirring with a magnetic stirrer at a speed of 800 rpm), slowly drip the reacted polymer solution into 100 mL of diethyl ether (1-2 drops per second) using a constant-pressure dropping funnel. After the dripping is completed, continue stirring for 30 minutes to completely precipitate the precipitate.

[0084] (2) Washing: The precipitated polymer was separated by filtration through a Buchner funnel and filter paper. The filter cake was transferred to a beaker, 30 mL of ether was added, and it was stirred for 15 minutes to dissolve the impurities. The polymer was separated again by filtration, and the supernatant was poured off. The washing step was repeated at least 3 times until there were no obvious impurities in the washing liquid.

[0085] (3) Drying: The washed polymer was transferred to a vacuum drying oven and dried under vacuum at 40 °C for 24 hours. After drying, the polymer (lithium-containing monomer copolymer-modified poly(ethylene oxide)) was stored in a desiccator or glove box for later use.

[0086] 2. Solution preparation

[0087] (1) Lithium-containing monomer copolymer-modified poly(ethylene oxide) solution: Outside the glove box, the lithium-containing monomer copolymer-modified poly(ethylene oxide) synthesized in step 1 (weighing 1.0 g) was dissolved in 20 mL of DCM to prepare a 5% (w / v) solution.

[0088] (2) Sulfide electrolyte dispersion: Inside the glove box, 0.2 g of the sulfide electrolyte Li6PS5Cl was dispersed in 20 mL of ACN (mass-volume ratio Li6PS5Cl:ACN = 1:100), and it was uniformly dispersed by ultrasonic treatment.

[0089] 3. Preparation of the emulsion of lithiumophilic polymer microspheres (performed inside the glove box):

[0090] (1) Mixing: Under vigorous stirring, the ACN dispersion of the sulfide electrolyte was slowly added dropwise to the DCM solution of the lithium-containing monomer copolymer-modified poly(ethylene oxide).

[0091] (2) Emulsification: An ultrasonic homogenizer was used for emulsification. The ultrasonic power and time were controlled. The power was 150 W, the time was 15 minutes, and it was intermittent ultrasonic treatment, ultrasonic for 5 seconds and stop for 2 seconds.

[0092] 4. Microsphere curing:

[0093] (1) Preliminary curing: The emulsion was transferred to an open beaker and slowly stirred overnight (about 12 hours) at 300 rpm using a magnetic stirrer at room temperature to allow the DCM to slowly volatilize. To better control the volatilization rate, it could be carried out in a fume hood and the ventilation volume could be appropriately controlled.

[0094] (2) Complete curing: The preliminarily cured microspheres were transferred to a vacuum drying oven and dried under vacuum at 40 °C for 24 hours to remove the residual ACN. This step needed to be carried out inside the glove box to prevent the electrolyte from reacting with moisture in the air.

[0095] 5. Washing and collection (performed inside the glove box):

[0096] (1) Washing: In the glove box, wash the microspheres 3 times with dry diethyl ether, using 10 mL of diethyl ether each time. Disperse the microspheres in diethyl ether, stir for 10 minutes, then centrifuge (centrifuge at 3000 rpm for 5 minutes), pour off the supernatant, and repeat this step 3 times.

[0097] (2) Collection: Vacuum dry the washed microspheres (average particle size of 5 μm) in the glove box for at least 12 hours, and then store them in the glove box for later use.

[0098] Example 3

[0099] This example provides a polymer microsphere with a lithium salt-doped PEO-coated sulfide electrolyte. The difference between this example and Example 1 is only that the rotation speed of the dispersion head of the high-speed shearing machine is set to 6000 rpm in the emulsification step, and the remaining steps and parameters are the same as those in Example 1. Finally, microspheres (average particle size of 10 μm) are obtained after washing.

[0100] Example 4

[0101] This example provides a polymer microsphere with a lithium salt-doped PEO-coated sulfide electrolyte. The difference between this example and Example 1 is only that the rotation speed of the dispersion head of the high-shear disperser is set to 11000 rpm in the emulsification step, and the remaining steps and parameters are the same as those in Example 1. Finally, microspheres (average particle size of 1 μm) are obtained after washing.

[0102] Example 5

[0103] This example provides a polymer microsphere with a polyether-coated sulfide electrolyte. The sulfide electrolyte used in this example is Li 10 GeP2S 12 (LGPS, purchased from Ganfeng Lithium Co., Ltd.), the lithiumophilic polymer matrix is a polyether polymer, specifically polytetrahydrofuran (PTHF, Mw = 400 g / mol, purchased from Sigma-Aldrich), the oil-phase solvent is chloroform (CHCl3, purchased from Sinopharm Chemical Reagent Co., Ltd.), and the dispersed-phase solvent is dimethyl sulfoxide (DMSO, purchased from Sinopharm Chemical Reagent Co., Ltd.).

[0104] All operations involving the sulfide electrolyte in this example need to be carried out in a glove box filled with argon or nitrogen to avoid the reaction of the sulfide with moisture and oxygen in the air. The preparation method of this example specifically includes the following steps:

[0105] 1. Solution preparation:

[0106] (1) PTHF solution: At room temperature (20 - 25 °C), dissolve 1.0 g of PTHF in 10 mL of chloroform (CHCl3) to prepare a 10% (w / v) solution. Use a magnetic stirrer to stir at a speed of 300 rpm for at least 2 hours until the PTHF is completely dissolved to form a uniform and transparent solution.

[0107] (2) Sulfide electrolyte dispersion: In a glove box, add 0.2 g of Li 10 GeP2S 12 to 20 mL of dimethyl sulfoxide (DMSO). Use an ultrasonic homogenizer to ultrasonicate at a power of 100 W for 10 minutes with intermittent sonication (sonicate for 5 seconds and stop for 2 seconds) to make it uniformly dispersed. After dispersion, visually observe that the dispersion should be uniform without precipitation.

[0108] 2. Preparation of polyether-coated sulfide electrolyte microspheres emulsion (performed in a glove box):

[0109] (1) Mixing: Under vigorous stirring of a magnetic stirrer at a speed of 600 rpm, slowly (1 - 2 drops per second) add the dimethyl sulfoxide (DMSO) dispersion of the sulfide electrolyte dropwise to the chloroform (CHCl3) solution of PTHF using a syringe. Control the dropping speed to avoid forming overly large droplets.

[0110] (2) Emulsification: Use a high-shear disperser (IKA Ultra-Turrax T25) to perform emulsification to obtain an emulsion. Set the rotation speed of the dispersion head to 8000 rpm and the emulsification time to 30 minutes.

[0111] 3. Microsphere curing:

[0112] (1) Preliminary curing: Transfer the emulsion to an open beaker and slowly stir at a speed of 300 rpm using a magnetic stirrer overnight (12 hours) at room temperature (20 - 25 °C) to allow the chloroform (CHCl3) to volatilize preliminarily and form partially cured microspheres.

[0113] (2) Complete curing (drying): Transfer the preliminarily cured microspheres to a vacuum drying oven and vacuum dry at 40 °C for 24 hours to completely remove the residual dimethyl sulfoxide (DMSO). This step needs to be performed in a glove box to prevent the sulfide from reacting with moisture in the air.

[0114] 4. Washing and collection (performed in a glove box):

[0115] (1) Washing: In a glove box, wash the microspheres 3 times with 10 mL of dry ether each time. Disperse the microspheres in ether, stir for 10 minutes, then centrifuge (centrifuge at 3000 rpm for 5 minutes), pour off the supernatant, and repeat this step 3 times.

[0116] (2) Collection: Vacuum dry the washed microspheres in a glove box for at least 12 hours, and then store them in the glove box for later use.

[0117] Example 6

[0118] This example provides polymer microspheres with a nitrogen-containing polymer-coated sulfide electrolyte. The sulfide electrolyte used in this example is Li3PS4 (purchased from Yili Technology), the lithiumophilic polymer matrix is a nitrogen-containing polymer, specifically polyvinylpyrrolidone (PVP, Mw = 400 g / mol, purchased from Sigma-Aldrich), the oil-phase solvent is n-hexane (purchased from Sinopharm Group), and the dispersion-phase solvent for dispersing the sulfide electrolyte is DMF (purchased from Sinopharm Group).

[0119] All operations involving the sulfide electrolyte in this example need to be carried out in a glove box filled with argon or nitrogen to avoid the reaction of the sulfide with moisture and oxygen in the air. The preparation method of this example specifically includes the following steps:

[0120] 1. Solution preparation:

[0121] (1) PVP solution: At room temperature (20 - 25 °C), dissolve 1.0 g of PVP in 10 mL of n-hexane to prepare a 10% (w / v) solution. Since PVP has good solubility, it is usually completely dissolved by stirring with a magnetic stirrer at a speed of 300 rpm for 1 hour to form a uniform and transparent solution.

[0122] (2) Sulfide electrolyte dispersion: In the glove box, add 0.2 g of Li3PS4 to 20 mL of DMF. Since the solubility of Li3PS4 in DMF may be low, use an ultrasonic homogenizer to ultrasonicate for 15 minutes at a power of 150 W, with intermittent ultrasonication (ultrasonication for 5 seconds, stop for 2 seconds) to promote its uniform dispersion. After dispersion, visually observe that the dispersion should be uniform without obvious precipitation.

[0123] 2. Preparation of an emulsion of nitrogen-containing polymer-coated sulfide electrolyte microspheres (performed in a glove box):

[0124] (1) Mixing: Under vigorous stirring with a magnetic stirrer at a speed of 600 rpm, slowly (1 - 2 drops per second) add the DMF dispersion of the sulfide electrolyte dropwise to the n-hexane solution of PVP using a syringe. Control the dropping speed to avoid forming overly large droplets.

[0125] (2) Emulsification: Use an ultrasonic homogenizer for emulsification to obtain an emulsion. Control the ultrasonic power to 150 W and the ultrasonic time to 15 minutes, with intermittent ultrasonication (ultrasonication for 5 seconds, stop for 2 seconds).

[0126] 3. Microsphere curing:

[0127] (1) Preliminary curing: Transfer the emulsion to an open beaker and slowly stir it overnight (12 hours) at room temperature (20 - 25 °C) using a magnetic stirrer at a speed of 300 rpm to allow the n - hexane to evaporate preliminarily and form partially cured microspheres.

[0128] (2) Complete curing: Transfer the preliminarily cured microspheres to a vacuum drying oven and vacuum - dry them at 40 °C for 24 hours to completely remove the residual DMF. This step needs to be carried out in a glove box to prevent the sulfide from reacting with the moisture in the air.

[0129] 4. Washing and collection (carried out in a glove box):

[0130] (1) Washing: In the glove box, wash the microspheres 3 times with dry diethyl ether, using 10 mL of diethyl ether each time. Disperse the microspheres in diethyl ether, stir for 10 minutes, then centrifuge (centrifuge at 3000 rpm for 5 minutes), pour off the supernatant, and repeat this step 3 times.

[0131] (2) Collection: Vacuum - dry the washed microspheres in the glove box for at least 12 hours, and then store them in the glove box for later use.

[0132] Example 7

[0133] This example provides polymer microspheres with a sulfur - containing polymer - coated sulfide electrolyte. The sulfide electrolyte used in this example is Li6PS5Br (purchased from Yili Technology), the lithium - philic polymer matrix is a sulfur - containing polymer, specifically polyphenylene sulfide, PPS, with an average molecular weight of about 400 g / mol (purchased from Sigma - Aldrich), the oil - phase solvent is dichloromethane (DCM) (purchased from Sinopharm Chemical Reagent Co., Ltd.), and the solvent used to disperse the sulfide electrolyte is acetonitrile (ACN) (purchased from Sinopharm Chemical Reagent Co., Ltd.).

[0134] All operations involving the sulfide electrolyte in this example need to be carried out in a glove box filled with argon or nitrogen to avoid the sulfide reacting with the moisture and oxygen in the air. The preparation method of this example specifically includes the following steps:

[0135] 1. Solution preparation:

[0136] (1) PPS solution: At room temperature (20 - 25 °C), dissolve 1.0 g of PPS in 10 mL of DCM to prepare a 10% (w / v) solution. Since the solubility of PPS is not as good as that of PEO, use a magnetic stirrer to stir at a speed of 300 rpm for at least 4 hours, or stir overnight, until PPS is completely dissolved to form a uniform and transparent solution.

[0137] (2) Sulfide electrolyte dispersion: In a glove box, 0.2 g of Li6PS5Br was added to 20 mL of ACN. Since the solubility of Li6PS5Br in ACN is low, an ultrasonic homogenizer was used to ultrasonicate for 15 minutes at a power of 150 W, with intermittent ultrasonication (ultrasonication for 5 seconds, stop for 2 seconds) to promote its uniform dispersion. After dispersion, visually observe that the dispersion should be uniform without obvious precipitation.

[0138] 2. Preparation of an emulsion of sulfur-containing polymer-coated sulfide electrolyte (performed in a glove box):

[0139] (1) Mixing: Under vigorous stirring at a speed of 600 rpm on a magnetic stirrer, the ACN dispersion of the sulfide electrolyte was slowly added dropwise (1 - 2 drops per second) to the DCM solution of PPS using a syringe. Control the dropping speed to avoid forming overly large droplets.

[0140] (2) Emulsification: An ultrasonic homogenizer was used for emulsification to obtain an emulsion. Control the ultrasonic power to 150 W and the ultrasonic time to 15 minutes, with intermittent ultrasonication (ultrasonication for 5 seconds, stop for 2 seconds).

[0141] 3. Microsphere curing:

[0142] (1) Preliminary curing: Transfer the emulsion to an open beaker and slowly stir overnight (12 hours) at a speed of 300 rpm using a magnetic stirrer at room temperature (20 - 25 °C) to allow the DCM to volatilize preliminarily and form partially cured microspheres.

[0143] (2) Complete curing (drying): Transfer the preliminarily cured microspheres to a vacuum drying oven and vacuum dry at 40 °C for 24 hours to completely remove the residual ACN. This step needs to be performed in a glove box to prevent the sulfide from reacting with moisture in the air.

[0144] 4. Washing and collection (performed in a glove box):

[0145] (1) Washing: In a glove box, wash the microspheres 3 times with 10 mL of dry ether each time. Disperse the microspheres in ether, stir for 10 minutes, then centrifuge (centrifuge at 3000 rpm for 5 minutes), pour off the supernatant, and repeat this step 3 times.

[0146] (2) Collection: Vacuum dry the washed microspheres in the glove box for at least 12 hours and then store them in the glove box for later use.

[0147] Comparative Example 1

[0148] This comparative example provides a sulfide electrolyte without polymer microspheres, using only Li6PS5Cl (purchased from Ganfeng Lithium) as the sulfide electrolyte without polymer coating.

[0149] Comparative Example 2

[0150] This comparative example provides a lithium salt-doped polymer microsphere. The difference from Example 1 is only that the rotation speed of the dispersion head of the high-shear disperser is set to 5000 rpm in the emulsification step, and the remaining steps and parameters are the same as those in Example 1. Finally, the microspheres (with an average particle size of 11 μm) are obtained after washing.

[0151] Comparative Example 3

[0152] This comparative example provides a lithium salt-doped polymer microsphere. The difference from Example 1 is only that the rotation speed of the dispersion head is set to 12000 rpm in the emulsification step, and the other steps and parameters are the same as those in Example 1. Finally, the microspheres (with an average particle size of 900 nm) are obtained after washing.

[0153] Comparative Example 4

[0154] This comparative example provides a lithium salt-doped polyethylene oxide as a lithiumophilic polymer matrix, without coating a sulfide electrolyte therein, and only uses this lithiumophilic polymer matrix as an electrolyte for all-solid-state lithium metal batteries.

[0155] Compared with Example 1, in the preparation method of this comparative example, in the first step of preparing the solution, only a polyethylene oxide solution and a lithium salt solution are prepared, and the lithium salt solution is slowly (1-2 drops per second) added dropwise to the DCM solution of PEO under vigorous stirring at a speed of 600 rpm on a magnetic stirrer to prepare a lithium salt-modified polyethylene oxide.

[0156] And the preparation of the sulfide electrolyte dispersion is not carried out, nor is the sulfide electrolyte dispersion mixed and emulsified with the lithium salt-modified polyethylene oxide. The lithium salt-modified polyethylene oxide is directly prepared into an electrolyte, and the specific steps are as follows:

[0157] 1. Solution casting: Slowly pour the prepared polymer solution onto a flat and clean substrate (the substrate is selected as a polytetrafluoroethylene PTFE plate). The doctor blade method can be used to control the uniform spreading of the solution and the film thickness (50 μm).

[0158] 2. Solvent evaporation and drying: Naturally evaporate the solvent DCM of the cast solution in a fume hood. After the DCM is basically evaporated, transfer the film to a vacuum drying oven and vacuum dry it at 40 °C for 24 hours to completely remove the residual solvents ACN and DCM. This step needs to be carried out in a glove box to prevent the lithium salt from reacting with moisture in the air.

[0159] 3. Film collection (carried out in a glove box):

[0160] (1)Peeling: After drying is completed, carefully peel the PEO-LiTFSI polymer electrolyte film from the substrate. When using a PTFE substrate, it is usually easy to peel.

[0161] (2)Storage: Store the peeled PEO-LiTFSI polymer electrolyte film in a dry environment in a glove box for future performance testing and battery assembly.

[0162] Comparative Example 5

[0163] This comparative example provides a lithium-containing monomer copolymer-modified polyethylene oxide as a lithiumophilic polymer matrix, without coating a sulfide solid electrolyte therein, and only using this lithiumophilic polymer matrix as an electrolyte in a all-solid-state lithium metal battery.

[0164] The preparation method of this comparative example compared with Example 2, when preparing the solution in Step 2, only prepare a solution of lithium-containing monomer copolymer-modified polyethylene oxide, without preparing a sulfide electrolyte dispersion, and in the subsequent steps, do not emulsify the sulfide electrolyte with the copolymer solution, but directly prepare this lithium-containing monomer copolymer-modified polyethylene oxide into an electrolyte, and the steps for preparing the lithium salt-modified polyethylene oxide into an electrolyte with reference to Comparative Example 4 are available for the operation method.

[0165] Comparative Example 6

[0166] This comparative example provides a lithium salt-doped polyethylene oxide as a lithiumophilic polymer matrix. The difference between this comparative example and Example 1 is only that no emulsification operation is carried out, and only the sulfide electrolyte dispersion is simply mixed with the lithium salt-modified polyethylene oxide solution, and the remaining steps and parameters are the same as those in Example 1, and finally microsphere aggregates are obtained after washing. As Figure 6 shown, it is the scanning electron microscope image of the microsphere aggregate electrolyte obtained in this comparative example. Without carrying out the emulsification operation, irregular particles or aggregates will be formed, and it is difficult to form a good structure of polymer microsphere-coated electrolyte.

[0167] Comparative Example 7

[0168] This comparative example provides an un-doped polyethylene oxide with lithium salt. The difference from Example 1 is only that polyethylene oxide is not doped and modified with lithium salt. That is, when preparing the lithium salt solution in the solution preparation stage, lithium salt LiTFSI is not added, and only 5 mL of acetonitrile is used as the solvent, and it is used to replace the lithium salt solution in the subsequent steps, and the remaining steps and parameters are the same as those in Example 1, and finally microspheres are obtained after washing.

[0169] Comparative Example 8

[0170] In this comparative example, compared with Example 1, the lithiophilic polymer matrix was replaced with a conventional non-lithiophilic polymer polytetrafluoroethylene (PTFE), and no lithium salt doping was carried out. The specific operation method was referred to Comparative Example 7.

[0171] Comparative Example 9

[0172] In this comparative example, compared with Example 1, the lithiophilic polymer matrix was replaced with a conventional non-lithiophilic polymer polyethylene, and no lithium salt doping was carried out. The specific operation method was referred to Comparative Example 7.

[0173] Comparative Example 10

[0174] In this comparative example, compared with Example 1, the lithiophilic polymer matrix was replaced with a conventional non-lithiophilic polymer polypropylene, and no lithium salt doping was carried out. The specific operation method was referred to Comparative Example 7.

[0175] Comparative Example 11

[0176] In this comparative example, compared with Example 1, the lithiophilic polymer matrix was replaced with a conventional non-lithiophilic polymer polyacrylonitrile, and no lithium salt doping was carried out. The specific operation method was referred to Comparative Example 7.

[0177] Effect Example 1

[0178] The alternating current impedance values of the inorganic sulfide electrolytes prepared in Examples 1-7 and Comparative Examples 1-11 above were measured using an electrochemical workstation, and the ionic conductivity was calculated. The calculation formula was σ = S / RL.

[0179] Among them, S is the area of the electrolyte sheet, L is the thickness of the electrolyte sheet, R is the resistance value, and σ is the ionic conductivity.

[0180] The products prepared in the above examples and comparative examples were assembled: in an inert gas glove box with a water and oxygen content ≤ 0.01 ppm, the lithiophilic polymer microspheres prepared in each example and comparative example were used as the electrolyte layer, the positive electrode was a pole piece with a unit area NCM811 loading of 10 mg / cm 2 and the lithium metal was the negative electrode layer to assemble a all-solid-state lithium metal battery. Finally, without external pressure, cyclic discharge was carried out first at 0.1 C for one cycle, and then long-term cycling tests were carried out at 0.5 C. The initial efficiency was tested, and the capacity retention rate was tested after 500 cycles. The results are shown in Table 1 below:

[0181] Table 1

[0182]

[0183] As can be seen from Table 1, when the polymer microspheres composed of a lithiumophilic polymer matrix and a sulfide electrolyte encapsulated therein according to the present invention are used as the electrolyte of an all-solid-state lithium metal battery, they can have a relatively high ionic conductivity, enabling the all-solid-state lithium metal battery to exhibit a higher initial efficiency and capacity retention rate, and improving the performance of the all-solid-state lithium metal battery in terms of lifespan. Figure 1 The excellent cycling ability and capacity retention rate of Example 1 can be seen; Figure 2 Its excellent Coulomb efficiency can be seen; Figure 3 It can also be seen that there is a huge difference in the discharge specific capacity between the lithium metal battery of Example 1 of the present invention and the lithium metal battery in Comparative Example 1 that does not use polymer microspheres as the electrolyte. The application of the polymer microspheres of the present invention to an all-solid-state lithium metal battery can significantly improve its performance.

[0184] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A lithium-philic polymer microsphere, characterized in that: It includes a lithium-philic polymer matrix, and a sulfide electrolyte coated in the lithium-philic polymer matrix; The lithium-philic polymer matrix includes polyethylene oxide copolymerized and modified by lithium-containing monomers; The polyethylene oxide modified by copolymerization of the lithium-containing monomer is obtained by dissolving polyethylene oxide, the lithium-containing monomer and the initiator in an organic solvent and heating them under the protection of an inert atmosphere for polymerization reaction, wherein the mass ratio of the polyethylene oxide, the lithium-containing monomer and the initiator is 10-50:1:0.02-0.1; The lithium-containing monomer is selected from at least one of lithiated acrylate, lithiated methacrylate, and lithium-containing vinyl monomer; The initiator is selected from at least one of azobisisoheptanitrile, azobis(2-methylbutyronitrile) and azobisisobutyronitrile.

2. The lithium-philic polymer microspheres according to claim 1, characterized in that The sulfide electrolyte is selected from Li3PS4, Li 10 GeP2S 12 , at least one of argyrodite-type electrolytes Li6PS5X; wherein X is selected from any one of Cl, Br, and I; The median particle size D of the sulfide electrolyte 50 =300 nm-500 nm.

3. The lithium-philic polymer microspheres according to claim 1, characterized in that The average particle size of the lithium-philic polymer microspheres is 1 μm-10 μm.

4. A method for preparing lithium-philic polymer microspheres according to any one of claims 1 to 3, characterized in that: The steps include: S1, dissolving the lithium-philic polymer in an oil phase solvent to form an oil phase; S2, dispersing the sulfide electrolyte in a dispersed phase solvent to form a dispersed phase; S3, slowly adding the dispersed phase of step S2 into the oil phase of step S1 under vigorous stirring to emulsify and form an emulsion; S4, volatilize the solvent in the emulsion, solidify to form microspheres; wash and dry to obtain.

5. The preparation method according to claim 4, characterized in that: In step S1, the oil phase solvent is selected from at least one of dichloromethane, chloroform, carbon tetrachloride, n-hexane, and cyclohexane; And / or, in step S2, the dispersed phase solvent is selected from at least one of acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide.

6. The preparation method according to claim 4, characterized in that: In step S3, the rotation speed of the vigorous stirring is 600-1000 rpm; And / or, the emulsification is performed by high shear dispersion or ultrasonic homogenization, and the emulsion formed is an oil-in-oil emulsion; The high shear dispersion has a rotation speed of 6000-11000 rpm and a time of 10-60 min; And / or, the power of the ultrasonic homogenization is 100-400 W, the time is 5-30 min, and the ultrasonic homogenization is performed in an intermittent operation, with each ultrasonication for 3-10 s and a stop time of 2-5 s.

7. An all-solid-state lithium metal battery, characterized in that: A battery comprising a positive electrode and a negative electrode, and the lithium-philic polymer microspheres as claimed in any one of claims 1 to 3 as an electrolyte; The positive electrode of the battery is selected from at least one of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese phosphate, lithium titanate, lithium nickel oxide, and lithium manganese oxide; The material of the negative electrode of the battery is lithium metal or an alloy, and the alloy is an alloy formed by lithium and at least one of Al, Sn, Si, Mg, and Zn.

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