Preparation method of pre-lithiation negative electrode for solid-state battery and solid-state battery

Abstract

The invention belongs to the technical field of solid-state lithium ion batteries, and relates to a preparation method of a pre-lithiated negative electrode for a solid-state battery and the solid-state battery. The method comprises the following steps: mixing liquid metal with a solvent, and adding a polymer to obtain a mixed dispersion liquid; preparing a polymer liquid metal fiber skeleton from the mixed dispersion liquid through an electrostatic spinning method; mixing and stirring an active material, a binder and a conductive agent to obtain negative electrode slurry; preparing a composite negative electrode active layer from the PET substrate, the polymer liquid metal fiber skeleton and the negative electrode slurry; and finally, rolling and compounding the composite negative electrode active layer and the lithium-copper composite belt to obtain the pre-lithiated negative electrode. A high-conductivity liquid metal polymer lithium-loving framework and a framework for buffering volume expansion are constructed in the negative electrode by adopting an electrostatic spinning technology, the framework can be used as lithium-loving sites of lithium ions to induce uniform deposition of the lithium ions, and the volume expansion in the charging and discharging process of the negative electrode can be effectively buffered by the self-healing capability of the liquid metal; the cycle life and the stability of the battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium-ion batteries, and particularly relates to a preparation method of a prelithiated anode for a solid-state battery and a solid-state battery. Background Art

[0002] In recent years, the new energy battery industry has developed rapidly. In the context of achieving the goals of carbon peak and carbon neutrality, it is crucial to develop lithium-ion batteries with high energy density, high safety, and long life. Compared with traditional graphite anodes, silicon-based materials with higher theoretical specific capacity are considered promising anode materials for solid-state lithium-ion batteries. However, silicon-based anodes have large volume changes during charge and discharge, accompanied by material structure pulverization and interfacial side reactions between the electrode and the electrolyte, which limit their cycle life. Moreover, during the first charging process of lithium-ion batteries, a solid electrolyte interface (SEI) film will be formed, which will irreversibly consume a large amount of lithium ions from the positive electrode, resulting in a low Coulomb efficiency in the first cycle and reducing the capacity and energy density of lithium-ion batteries. Currently, prelithiation is often used to directly supplement Li+ and supplemented with other methods to significantly improve the first efficiency, thereby enhancing the overall performance of the battery.

[0003] In the invention patent "Prelithiated lithiumophilic three-dimensional structure anode and its preparation method and application" with the application number CN202410935446, the prelithiated lithiumophilic three-dimensional structure anode includes a three-dimensional conductive framework and lithiumophilic sites located at the pores of the three-dimensional conductive framework, and a prelithiated layer is loaded on the side of the three-dimensional conductive framework facing away from the electrolyte. It can solve the problems of volume expansion during lithium insertion and extraction of existing lithium metal anodes and low first Coulomb efficiency of existing lithiumophilic anode materials. However, this technology has disadvantages such as complex processes, difficult control of the uniform dispersion of lithiumophilic sites, and low prelithiation efficiency.

[0004] In the invention patent "A prelithiated or prenated electrode and its preparation method, battery" with the application number CN2024105867933, its preparation method at least includes the following steps: first, obtain a negative electrode current collector prepared by a traditional wet process, or a self-supporting structure negative electrode with a copper or liquid metal coating prepared by a dry electrode process; subsequently, design a Li or Na‖PEG-PFPE‖PET composite film with a "sandwich" structure, and the middle layer contains a small amount of photoinitiator; finally, co-roll the composite film with the obtained negative electrode, and under the action of pressure, the active material will undergo a prelithiation or prenation reaction, remove the PET film, and induce a photoinitiated polymerization reaction to obtain a dense encapsulation film. Its preparation method has many steps and complex preparation processes, making it difficult to achieve large-scale application. In addition, the degree and consistency of photopolymerization are difficult to control, so it will have a certain impact on the final performance of the battery cell. Summary of the Invention

[0005] The first object of the present invention is to provide a prelithiated anode for a solid-state battery, which can simultaneously supplement the irreversible lithium loss during the cycle, alleviate the volume expansion during charge and discharge, construct ionophilic lithium sites, and induce uniform deposition of lithium ions.

[0006] The second object of the present invention is to provide a preparation method for the above-mentioned prelithiated anode for a solid-state battery.

[0007] The third object of the present invention is to provide a solid-state battery, in which the above-mentioned prelithiated anode for a solid-state battery is applied.

[0008] In order to achieve the above objects, the technical solutions adopted by the present invention are as follows: A preparation method for a prelithiated anode for a solid-state battery specifically includes the following steps: Step 1: Mix a liquid metal with a solvent, and obtain a liquid metal dispersion solution after ultrasonic dispersion. Add an appropriate amount of polymer to the above liquid metal dispersion solution, and stir evenly to form a uniform mixed dispersion liquid; Step 2: Prepare a polymer liquid metal fiber framework by electrospinning the mixed dispersion liquid obtained in Step 1; Step 3: Mix the active material, binder, and conductive agent in proportion and stir for 2 - 8 h to obtain a negative electrode paste; Step 4: Place the polymer liquid metal fiber framework prepared in Step 2 on the surface of a PET substrate, and then coat the negative electrode paste on the surface of the polymer liquid metal fiber framework. After drying, a composite negative electrode active layer for a solid-state battery is prepared; Step 5: Integrally roll and compound the above composite negative electrode active layer with a lithium copper composite tape to prepare a prelithiated negative electrode sheet.

[0009] Further, in Step 1, the stirring time is 3 - 5 h, and the stirring temperature is 40°C - 80°C.

[0010] Further, in Step 1, the liquid metal is at least one of gallium, gallium-indium alloy, gallium-tin alloy, gallium-zinc alloy, gallium-indium-tin alloy, gallium-indium-tin-zinc alloy, and liquid sodium-potassium alloy; the solvent is one of dimethylformamide, chloroform, trifluoroethanol, acetone, methanol, and deionized water; the polymer is one of polyacrylonitrile, poly(ethylene oxide), polycaprolactone, polyacrylate, and polyamide.

[0011] Further, in Step 1, the ratio of the liquid metal to the solvent is 1:2 - 6. Preferably, the ratio of the liquid metal to the solvent is 1:3 - 5.

[0012] Further, in Step 1, the addition ratio of the polymer to the liquid metal is 1:1 - 0.5.

[0013] Further, in step 2, the conditions for electrospinning are as follows: the feeding speed is 0.005 - 0.015 mL / min, the high voltage is 10 - 20 KV, the distance between the emitting needle and the collector is 5 - 20 cm, the temperature is 20 - 30 °C, and the spinning time is set to 60 - 360 min.

[0014] Preferably, in step 2, the conditions for electrospinning are as follows: the feeding speed is 0.008 - 0.01 mL / min, the high voltage is set to 15 - 18 KV, the distance between the emitting needle and the collector is 10 - 15 cm, the temperature is 25 °C, and the time is 180 - 300 h.

[0015] Further, in step 3, specifically, the homogenization is carried out according to the ratio of active material: binder: conductive agent of 93 - 98.5 wt%: 1 - 5 wt%: 0.5 - 2 wt%. The stirring speed is 400 - 800 rpm / min, and the stirring time is 2 - 8 h to obtain a stable negative electrode slurry, wherein the active material is at least one of silicon oxide, silicon carbide, pure silicon, and graphite.

[0016] Further, in step 4, the drying temperature is 80 - 110 °C, and the drying time is 8 - 15 h.

[0017] A negative electrode plate for a solid-state battery is prepared according to the above preparation method of a prelithiated negative electrode for a solid-state battery. It includes a negative electrode current collector and a composite negative electrode active layer coated on the surface of the negative electrode current collector. A polymer liquid metal fiber skeleton is disposed inside the composite negative electrode active layer, and the thickness of the polymer liquid metal fiber skeleton is 2 - 8 μm.

[0018] A solid-state battery is prepared by laminating a negative electrode plate prepared by using the above preparation method of a prelithiated negative electrode for a solid-state battery, an electrolyte membrane, and a positive electrode plate in sequence, and then performing aluminum-plastic film encapsulation and tab welding.

[0019] Further, the preparation method of the positive electrode plate includes the following steps: mixing NCM811, Li6PS5Cl, carbon nanotubes, and polytetrafluoroethylene according to a mass ratio of 80 - 85:10 - 20:1 - 1.5:1 - 1.5, grinding, and hot roll-pressing to obtain a positive electrode active layer. After laminating the positive electrode active layer with an aluminum foil, the positive electrode of the solid-state battery is obtained.

[0020] Further, the preparation method of the electrolyte membrane includes the following steps: mixing an electrolyte and polytetrafluoroethylene according to a mass ratio of 94 - 98:6 - 2, grinding, and hot roll-pressing to obtain the electrolyte membrane of the solid-state battery; the electrolyte is at least one of sulfide electrolytes, polymer electrolytes, oxide electrolytes, and halide electrolytes.

[0021] The beneficial effects of the present invention are as follows: 1. The present invention provides a method for preparing a negative electrode sheet for a solid-state battery. By means of electrospinning, a highly conductive liquid metal polymer lithium-philic framework and a skeleton for buffering volume expansion are constructed inside the negative electrode. It can not only serve as a lithium-philic site for lithium ions to induce uniform deposition of lithium ions, but also, due to the good self-healing ability of the liquid metal, the liquid metal framework inside it can effectively buffer the volume expansion during the charge and discharge process of the negative electrode, increasing the cycle life and stability of the battery.

[0022] 2. The electrospinning method adopted by the present invention constructs a liquid metal polymer skeleton on the negative electrode side. At the same time, the self-supporting negative electrode structure can achieve efficient prelithiation. The liquid metal polymer skeleton therein not only serves as a fast channel for ion transport, but also, due to the good self-healing ability of the liquid metal, the liquid metal framework inside it can effectively buffer the volume expansion during the charge and discharge process of the negative electrode. And the simple and efficient prelithiation can be realized through the self-supporting active material layer, improving the initial efficiency and subsequent cycle life and stability of the battery. Through experimental comparison, it can be seen that the solid-state battery assembled with this negative electrode exhibits excellent electrochemical performance. At the same time, the thickness of the lithium foil in the lithium-copper composite tape is controllable, and good cycle stability can also be achieved when the lithium supplement amount is large, providing a certain reference direction for the development of subsequent lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a cross-sectional schematic diagram of a prelithiated negative electrode for a solid-state battery of the present invention; wherein 001 is the negative electrode current collector, 002 is the polymer liquid metal fiber skeleton, and 003 is the composite negative electrode active layer coated on the surface of the negative electrode current collector.

[0024] Figure 2 It is a comparison diagram of the cycle capacity retention rates of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] A method for preparing a prelithiated negative electrode for a solid-state battery is specifically prepared by the following steps: Step 1: Mix the liquid metal with a solvent, and obtain a liquid metal dispersion solution after ultrasonic dispersion. Add an appropriate amount of polymer to the above liquid metal dispersion solution, and stir evenly to form a uniform mixed dispersion liquid. Preferably, the stirring time is 3 to 5 h, and the stirring temperature is 40 °C to 80 °C.

[0027] Wherein the liquid metal is at least one of gallium, gallium-indium alloy, gallium-tin alloy, gallium-zinc alloy, gallium-indium-tin alloy, gallium-indium-tin-zinc alloy, and liquid sodium-potassium alloy; the solvent is one of dimethylformamide, chloroform, trifluoroethanol, acetone, methanol, and deionized water; the polymer is one of polyacrylonitrile, polyethylene oxide, polycaprolactone, polyacrylate, and polyamide.

[0028] In step 1, the ratio of the liquid metal to the solvent is 1:2 to 6, and the preferred ratio is 1:3 to 5; the addition ratio of the polymer to the liquid metal is 1:1 to 0.5.

[0029] Step 2: Prepare a polymer liquid metal fiber skeleton from the mixed dispersion obtained in step 1 by electrospinning.

[0030] The conditions for the electrospinning are as follows: the feeding rate is 0.005 to 0.015 mL / min, the high voltage is 10 to 20 KV, the distance between the emitting needle and the collector is 5 to 20 cm, the temperature is 20 to 30 °C, and the spinning time is set to 60 to 360 min.

[0031] In step 2, the preferred electrospinning conditions are as follows: the feeding rate is 0.008 to 0.01 mL / min, the high voltage is set to 15 to 18 KV, the distance between the emitting needle and the collector is 10 to 15 cm, the temperature is 25 °C, and the time is 180 to 300 h.

[0032] Step 3: Mix and stir the active material, binder, and conductive agent in proportion for 2 to 8 h to obtain a negative electrode slurry.

[0033] Specifically, homogenization is carried out according to the ratio of active material: binder: conductive agent of 93 to 98.5 wt%: 1 to 5 wt%: 0.5 to 2 wt%. The stirring speed is 400 to 800 rpm / min, and the stirring time is 2 to 8 h to obtain a stable negative electrode slurry, wherein the active material is at least one of silicon oxide, silicon carbon, pure silicon, and graphite.

[0034] Step 4: Place the polymer liquid metal fiber skeleton prepared in step 2 on the surface of a PET substrate, and then coat the negative electrode slurry on the surface of the polymer liquid metal fiber skeleton. After drying, a composite negative electrode active layer for a solid-state battery is prepared. Preferably, the drying temperature is 80 to 110 °C, and the drying time is 8 to 15 h.

[0035] Step 5: Integrally roll and laminate the above composite negative electrode active layer with a lithium-copper composite tape to prepare a prelithiated negative electrode sheet.

[0036] According to the above preparation method, a prelithiated anode for a solid-state battery is obtained. As Figure 1 shown in Figure 1 , it includes a negative current collector and a composite negative active layer coated on the surface of the negative current collector. A polymer liquid metal fiber skeleton is disposed inside the composite negative active layer, and the thickness of the polymer liquid metal fiber skeleton is 2-8 μm.

[0037] The prelithiated anode sheet for a solid-state battery obtained above is used to prepare a solid-state battery.

[0038] To prepare a solid-state battery, a positive electrode is required. The preparation method of the positive electrode sheet includes the following steps: Mix NCM811, Li6PS5Cl, carbon nanotubes, and polytetrafluoroethylene in a mass ratio of 80-85:10-20:1-1.5:1-1.5, grind, and hot roll press to obtain a positive active layer. After the positive active layer is compounded with an aluminum foil, the positive electrode of the solid-state battery is obtained.

[0039] In addition, an electrolyte membrane is also required for preparing a solid-state battery. The preparation method includes the following steps: Mix an electrolyte and polytetrafluoroethylene in a mass ratio of 94-98:6-2, grind, and hot roll press to obtain the electrolyte membrane of the solid-state battery; the electrolyte is at least one of a sulfide electrolyte, a polymer electrolyte, an oxide electrolyte, and a halide electrolyte.

[0040] Stack the prepared positive electrode sheet, electrolyte membrane, and prelithiated anode sheet in sequence, and then perform aluminum-plastic film encapsulation and ear welding to prepare the solid-state battery.

[0041] Example 1 A preparation method of a prelithiated anode for a solid-state battery includes the following steps: Step 1: Disperse 5.5 g of gallium-indium-tin (GaInSn) alloy liquid metal in 16.5 g of a solvent and ultrasonically disperse for 10 min until the metal particles with a metallic bright color in the solution are completely dispersed into uniform gray nano liquid metal particles without obvious precipitation, obtaining a uniform liquid metal dispersion solution; add 6.88 g of polyacrylonitrile to the above liquid metal dispersion solution and stir at 60 °C for 4 h until the polymer is completely dissolved to form a homogeneous mixed dispersion; among them, the mass ratios of gallium, indium, and tin in the gallium-indium-tin (GaInSn) alloy liquid metal are 7:2:1 respectively; the solvent is dimethylformamide.

[0042] Step 2: Add the mixed dispersion obtained in Step 1 to an injection pump, and prepare a polymer liquid metal fiber skeleton with a thickness of 3 μm on the surface of a collector through electrospinning. The collector is a 15-μm aluminum foil, and after collection, it is dried at 90 °C for 4 h. The electrostatic voltage of the electrostatic spraying equipment is 15 kV, the collection distance is 10 cm, the propulsion speed is 0.008 mL / min, and the time is set to 180 min.

[0043] Step 3: Mix 19.3 g of nanosilicon, 0.2 g of polyacrylic acid (PAA), 0.1 g of carboxymethyl cellulose (CMC), and 0.4 g of carbon nanotubes (CNT), and then perform double-planet stirring. Stir at 600 rpm for 4 h to obtain the anode slurry.

[0044] Step 4: Place the polymer liquid metal skeleton prepared in Step 2 on the surface of the PET substrate, then perform blade coating of the anode slurry on the surface of the polymer liquid metal skeleton, and then dry at 90 °C for 12 h to obtain the self-supporting composite anode active layer.

[0045] Step 5: Integrally compound the prepared self-supporting composite anode active layer with PET and the lithium copper composite tape by rolling. The lithium metal is on the side of the self-supporting anode. The thickness of the lithium foil in the lithium copper composite tape is 5 μm, the thickness of the copper foil is 6 μm, and the thickness of the roller is set to 95 μm. After rolling, remove the PET substrate to prepare the prelithiated solid-state silicon alloy anode.

[0046] According to the above preparation method, a prelithiated anode for a solid-state battery is obtained. It includes an anode current collector and a composite anode active layer coated on the surface of the anode current collector. A polymer liquid metal fiber skeleton is disposed inside the composite anode active layer, and the thickness of the polymer liquid metal fiber skeleton is 3 μm.

[0047] Use the above-obtained prelithiated anode for a solid-state battery to prepare a solid-state battery. An electrolyte membrane and a cathode are also required for the preparation of the solid-state battery. The specific preparation method is described as follows.

[0048] Preparation of the electrolyte membrane: Mix the sulfide electrolyte Li6PS5Cl and PTFE according to a mass ratio of 95:5. Place the mixture in an agate mortar and grind for 30 min to obtain a rectangular sulfide electrolyte sheet. Perform hot rolling on the obtained rectangular electrolyte sheet. The rolling temperature is 120 °C, and roll until the thickness reaches 40 μm to prepare the sulfide electrolyte membrane. Cut the electrolyte membrane into pieces for standby.

[0049] Preparation of the cathode electrode sheet: Mix NCM811, Li6PS5Cl, CNT, and PTFE in a ratio of 82:15:1.5:1.5. After mixing, place the mixture in an agate mortar and grind for 40 min. Then perform hot rolling on the obtained rectangular sheet of the electrode active material. The rolling temperature is 120 °C. After rolling, the thickness is 120 μm, and the areal capacity is 6 mAh / cm2. Compound the prepared active material layer with an aluminum foil and cut into pieces for standby.

[0050] Cell Assembly and Testing: The prepared positive electrode, electrolyte membrane, and prelithiated negative electrode are stacked in sequence, followed by aluminum-plastic film encapsulation and tab welding to prepare a solid-state cell. Subsequently, cyclic testing (+0.5C / -0.5C@25°C) is carried out.

[0051] Example 2 A method for preparing a prelithiated negative electrode for a solid-state battery, comprising the following steps: Step 1, Disperse 5.5 g of gallium-indium (GaIn) alloy liquid metal in 16.5 g of solvent and ultrasonically disperse for 10 min until the metallic particles with metallic luster in the solution are completely dispersed into uniform gray nano-sized liquid metal particles without obvious precipitation, obtaining a uniform liquid metal dispersion solution; Add 6.88 g of polyethylene oxide to the above liquid metal dispersion and stir at 60°C for 4 h until the polymer is completely dissolved to form a homogeneous mixed dispersion; Among them, the mass ratios of gallium and indium in the gallium-indium-tin (GaIn) alloy liquid metal are 3:1 respectively; The solvent is deionized water.

[0052] Step 2, Add the mixed dispersion obtained in Step 1 to an injection pump, and prepare a 3-μm-thick polymer liquid metal fiber framework on the surface of the collector through electrospinning. The collector is a 15-μm aluminum foil, and after collection, it is dried at 90°C for 4 h. The electrostatic voltage of the electrostatic spraying equipment is 15 kV, the collection distance is 10 cm, the propulsion speed is 0.008 mL / min, and the time is set to 180 min.

[0053] Step 3, Mix 19.3 g of silicon-oxygen material, 0.2 g of polyacrylic acid (PAA), 0.1 g of styrene-butadiene latex (SBR), and 0.4 g of carbon nanotubes (CNT), and carry out double-planet stirring at 600 rpm for 4 h to obtain a negative electrode slurry.

[0054] Step 4, Place the polymer liquid metal fiber framework prepared in Step 2 on the surface of the PET substrate, then carry out doctor blade coating of the negative electrode slurry on the surface of the polymer liquid metal fiber framework, and then dry at 90°C for 12 h to obtain a self-supporting composite negative electrode active layer.

[0055] Step 5, Carry out roll pressing integration of the prepared composite negative electrode active layer with PET self-support and the lithium-copper composite tape. One side of the self-supporting composite negative electrode active layer faces the lithium metal. The thickness of the lithium foil in the lithium-copper composite tape is 5 μm, the thickness of the copper foil is 6 μm, the thickness of the roller is set to 95 μm. After roll pressing, remove the PET substrate to prepare a prelithiated solid-state silicon alloy negative electrode.

[0056] The pre-lithiated anode for a solid-state battery obtained above is used to prepare a solid-state battery. To prepare a solid-state battery, an electrolyte membrane and a positive electrode are also required. In this embodiment, the preparation method of the electrolyte membrane and the preparation method of the positive electrode sheet are the same as those in Example 1. The prepared positive electrode sheet, electrolyte membrane, and pre-lithiated anode are stacked in sequence, and then an aluminum-plastic film is used for encapsulation and the tabs are welded to prepare a solid-state battery cell. Subsequently, a cycling test (+0.5C / -0.5C@25°C) is carried out.

[0057] Example 3 The difference between the preparation method of the pre-lithiated anode for a solid-state battery in this embodiment and that in Example 1 is that in this Example 3, the electrospinning time for preparing the polymer liquid metal fiber framework is set to 60 min, and the corresponding thickness is 2 μm.

[0058] Example 4 The difference between the preparation method of the pre-lithiated anode for a solid-state battery in this embodiment and that in Example 1 is that in this Example 4, the electrospinning time for preparing the polymer liquid metal fiber framework is set to 360 min, and the corresponding thickness is 6 μm.

[0059] Example 5 The difference between the preparation method of the pre-lithiated anode for a solid-state battery in this embodiment and that in Example 1 is that in this Example 5, the thickness of the lithium copper composite lithium foil is 3 μm.

[0060] Example 6 The difference between the preparation method of the pre-lithiated anode for a solid-state battery in this embodiment and that in Example 1 is that in this embodiment, the thickness of the lithium copper composite lithium foil is 20 μm.

[0061] Example 7 The difference between the preparation method of the pre-lithiated anode for a solid-state battery in this embodiment and that in Example 1 is that in Example 7, the negative electrode directly uses a 30-μm-thick lithium copper composite strip as the negative electrode, and the preparation and assembly of a lithium metal battery are tested. It mainly includes the following steps: Step 1, Disperse 5.5 g of gallium indium tin (GaInSn) alloy liquid metal in 16.5 g of solvent and ultrasonically disperse for 10 min until the metal particles with a metallic bright color in the solution are completely dispersed into uniform gray nano-sized liquid metal particles without obvious precipitation, that is, a uniform liquid metal dispersion solution is obtained; add 6.88 g of polyacrylonitrile to the above liquid metal dispersion solution and stir at 60°C for 4 h until the polymer is completely dissolved to form a homogeneous mixed dispersion; among them, the mass ratio of gallium, indium, and tin in the gallium indium tin (GaInSn) alloy liquid metal is 7:2:1; the solvent is dimethylformamide; Step 2: Add the mixed dispersion obtained in Step 1 into an injection pump, and prepare a 3-μm-thick polymer liquid metal fiber skeleton on the surface of a collector through electrospinning. The collector is a 15-μm aluminum foil, which is dried at 90 °C for 4 h after collection. The electrostatic voltage of the electrostatic spraying equipment is 15 kV, the collection distance is 10 cm, the propulsion speed is 0.008 mL / min, and the time is set to 180 min.

[0062] Step 3: Directly roll and integrally compound the prepared polymer liquid metal fiber skeleton with a lithium-copper composite tape. Among them, the lithium metal faces the self-supporting negative electrode side. The thickness of the lithium foil in the lithium-copper composite tape is 30 μm, the thickness of the copper foil is 6 μm, and the thickness of the roller is set to 35 μm, that is, a modified lithium metal negative electrode protected by liquid metal polymer is prepared.

[0063] Use the modified lithium metal negative electrode obtained by the above method to prepare a solid-state battery. The preparation methods of the electrolyte membrane and the positive electrode required for preparing the solid-state battery are the same as those in Example 1, and the specific preparation methods are described as follows.

[0064] Preparation of electrolyte membrane: Mix sulfide electrolyte Li6PS5Cl and PTFE in a mass ratio of 95:5, place the mixture in an agate mortar and grind for 30 min to obtain a rectangular sulfide electrolyte sheet. Perform hot rolling on the obtained rectangular electrolyte sheet, with the rolling temperature of 120 °C, and roll until the thickness reaches 40 microns to prepare a sulfide electrolyte membrane, and cut the electrolyte membrane into pieces for standby.

[0065] Preparation of positive electrode sheet: Mix NCM811, Li6PS5Cl, CNT, and PTFE in a ratio of 82:15:1.5:1.5. After mixing, place the mixture in an agate mortar and grind for 40 min. Then perform hot rolling on the obtained rectangular sheet of electrode active material, with the rolling temperature of 120 °C. After rolling, the thickness is 120 μm and the areal capacity is 6 mAh / cm2. Composite the prepared active material layer with an aluminum foil and cut into pieces for standby.

[0066] Cell assembly and testing: Stack the prepared positive electrode sheet, electrolyte membrane, and modified lithium metal negative electrode in sequence, then perform aluminum-plastic film encapsulation and tab welding to prepare a solid-state cell. Subsequently, perform a cycle test (+0.5C / -0.5C@25 °C).

[0067] Comparative Example 1 The preparation method of the prelithiated negative electrode for the solid-state battery in this comparative example is roughly the same as that in Example 1. The difference between the preparation method in this comparative example and Example 1 is that the prelithiated negative electrode sheet for the solid-state battery in Comparative Example 1 does not add a liquid metal polymer fiber skeleton.

[0068] Comparative Example 2 The preparation method of the prelithiated anode for the solid-state battery in this comparative example is substantially the same as that in Example 1. The difference between the preparation method in this comparative example and that in Example 1 is that no liquid metal is added to the fiber skeleton in the prelithiated anode sheet for the solid-state battery in Comparative Example 2, and it is only a polymer fiber skeleton.

[0069] Comparative Example 3 The preparation method of the prelithiated anode for the solid-state battery in this comparative example is substantially the same as that in Example 1. The difference between the preparation method in this comparative example and that in Example 1 is that no prelithiation treatment is performed on the anode sheet for the solid-state battery in Comparative Example 3, and it mainly includes the following steps: Step 1: Disperse 5.5 g of gallium-indium (GaIn) alloy liquid metal in 16.5 g of solvent and ultrasonically disperse for 10 min until the metal particles with metallic luster in the solution are completely dispersed into uniform gray nano liquid metal particles without obvious precipitation, thus obtaining a uniform liquid metal dispersion solution; add 6.88 g of polyethylene oxide to the above liquid metal dispersion and stir at 60 °C for 4 h until the polymer is completely dissolved to form a homogeneous mixed dispersion; among them, the mass ratio of gallium and indium in the gallium-indium-tin (GaIn) alloy liquid metal is 3:1 respectively; the solvent is deionized water.

[0070] Step 2: Add the polymer-liquid metal mixed solution obtained in Step 1 to an injection pump, and prepare a 3-μm-thick polymer-liquid metal fiber skeleton on the surface of the collector through electrospinning. The collector is a 15-μm aluminum foil, and after collection, it is dried at 90 °C for 4 h. The electrostatic voltage of the electrostatic spraying equipment is 15 kV, the collection distance is 10 cm, the propulsion speed is 0.008 mL / min, and the time is set to 180 min.

[0071] Step 3: Mix 19.3 g of silicon-oxygen material, 0.2 g of polyacrylic acid (PAA), 0.1 g of styrene-butadiene latex (SBR), and 0.4 g of carbon nanotubes (CNT), and perform double planetary stirring at 600 rpm for 4 h to obtain the anode slurry.

[0072] Step 4: Apply the anode active slurry onto the surface of the liquid metal-polymer fiber skeleton prepared in Step 2 placed on the surface of the copper foil by doctor blade coating, and dry at 90 °C for 12 h to obtain the anode sheet with a polymer-liquid metal fiber skeleton.

[0073] Use the obtained anode sheet with a polymer-liquid metal fiber skeleton to prepare a solid-state battery. The preparation methods of the electrolyte membrane and the cathode sheet required for preparing the solid-state battery are the same as those in Example 1. Stack the prepared cathode sheet, electrolyte membrane, and anode sheet with a polymer-liquid metal fiber skeleton in sequence, and then perform aluminum-plastic film encapsulation and tab welding to prepare the solid-state battery cell.

[0074] The solid-state batteries of Examples 1-7 and Comparative Examples 1-3 were tested for cycle performance under the cycle test conditions of +0.5 C / -0.5 C@25 °C. The test results are shown in the following table: From the comparison of the initial efficiency and the capacity retention rate after 300 cycles of Example 1 and Comparative Example 1, as Figure 2 shown, during the cycling process, the polymer liquid metal fiber skeleton can effectively buffer the volume expansion of the negative electrode, improve the negative electrode and structural strength, and enable it to exhibit excellent cycle performance; while in Example 2 where liquid metal was not added to the fiber skeleton, the polymer fiber skeleton has limited effects on volume expansion and uniform lithium deposition; from the comparison of Comparative Example 3 and Example 1, through this simple and efficient prelithiation method, the irreversible lithium loss during the first charge and discharge process of the battery and the lithium loss during the cycling process can be effectively supplemented, greatly improving the first Coulombic efficiency and cycle stability of the battery cell.

[0075] Therefore, by using electrospinning to construct a highly conductive liquid metal framework and a volume expansion buffer layer inside the negative electrode, it can not only serve as a lithiumophilic site for lithium ions to induce uniform lithium ion deposition, but also due to the good self-healing ability of liquid metal, the liquid metal framework inside can effectively buffer the volume expansion during the charge and discharge process of the negative electrode, increasing the cycle life and stability of the battery. The solid-state battery assembled with this negative electrode exhibits excellent electrochemical performance.

Claims

1. A preparation method of a prelithiated negative electrode for a solid-state battery, characterized in that, Specifically, it includes the following steps: Step 1: Mix liquid metal with a solvent, and after ultrasonic dispersion, obtain a liquid metal dispersion solution. Add an appropriate amount of polymer to the liquid metal dispersion solution, and stir evenly to form a homogeneous mixed dispersion; Step 2: Use the mixed dispersion obtained in Step 1 to prepare a polymer liquid metal fiber framework by electrospinning; Step 3: Mix the active material, binder, and conductive agent in proportion and stir for 2 - 8 h to obtain a negative electrode paste; Step 4: Place the polymer liquid metal fiber framework prepared in Step 2 on the surface of a PET substrate, and then coat the negative electrode paste on the surface of the polymer liquid metal fiber framework. After drying, a composite negative electrode active layer for a solid-state battery is prepared; Step 5: Integrally roll and bond the above composite negative electrode active layer with a lithium copper composite tape to prepare a prelithiated negative electrode sheet.

2. The preparation method of a prelithiated anode for a solid-state battery according to claim 1, characterized in that, In Step 1, the stirring time is 3 - 5 h, and the stirring temperature is 40°C - 80°C.

3. The preparation method of a prelithiated negative electrode for a solid-state battery according to claim 1, wherein, In Step 1, the liquid metal is at least one of gallium, gallium-indium alloy, gallium-tin alloy, gallium-zinc alloy, gallium-indium-tin alloy, gallium-indium-tin-zinc alloy, liquid sodium-potassium alloy; the solvent is one of dimethylformamide, chloroform, trifluoroethanol, acetone, methanol, deionized water; the polymer is one of polyacrylonitrile, poly(ethylene oxide), polycaprolactone, polyacrylate, polyamide.

4. The preparation method of a prelithiated anode for a solid-state battery according to claim 1 or 3, characterized in that, In Step 1, the ratio of liquid metal to solvent is 1:2 - 6.

5. The preparation method of a prelithiated negative electrode for a solid-state battery according to claim 1 or 3, characterized in that, In Step 1, the ratio of liquid metal to solvent is 1:3 - 5.

6. The preparation method of a prelithiated negative electrode for a solid-state battery according to claim 1 or 3, characterized in that, In Step 1, the addition ratio of the polymer to the liquid metal is 1:1 - 0.

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7. The preparation method of a prelithiated anode for a solid-state battery according to claim 1, wherein, In Step 2, the conditions of the electrospinning are as follows: the feeding speed is 0.005 - 0.015 mL / min, the high voltage is 10 - 20 KV, the distance between the emitting needle and the collector is 5 - 20 cm, the temperature is 20 - 30°C, and the spinning time is set to 60 - 360 min.

8. The preparation method of a prelithiated negative electrode for a solid-state battery according to claim 1, characterized in that, In Step 2, the conditions of the electrospinning are as follows: the feeding speed is 0.008 - 0.01 mL / min, the high voltage is set to 15 - 18 KV, the distance between the emitting needle and the collector is 10 - 15 cm, the temperature is 25°C, and the time is 180 - 300 h.

9. The preparation method of a prelithiated negative electrode for a solid-state battery according to claim 1, wherein, In Step 3, homogenize according to the ratio of active material: binder: conductive agent of 93 - 98.5 wt%: 1 - 5 wt%: 0.5 - 2 wt%. The stirring speed is 400 - 800 rpm / min, and the stirring time is 2 - 8 h to obtain a stable negative electrode paste, where the active material is at least one of silicon oxide, silicon carbon, pure silicon, graphite.

10. The preparation method of a prelithiated anode for a solid-state battery according to claim 1, characterized in that, In Step 4, the drying temperature is 80 - 110°C, and the drying time is 8 - 15 h.

11. A negative electrode sheet for a solid-state battery, which is prepared by the preparation method of a pre-lithiated negative electrode for a solid-state battery according to any one of claims 1 to 10, is characterized in that, It includes a negative electrode current collector and a composite negative electrode active layer coated on the surface of the negative electrode current collector. The composite negative electrode active layer contains a polymer liquid metal fiber framework inside, and the thickness of the polymer liquid metal fiber framework is 2 - 8 μm.

12. A solid-state battery, characterized in that, The negative electrode sheet is obtained by using the preparation method of a prelithiated negative electrode for a solid-state battery described in any one of claims 1 to 10. After laminating the negative electrode sheet, an electrolyte membrane, and a positive electrode sheet in sequence, an aluminum-plastic film is used for encapsulation and the tabs are welded to prepare a solid-state battery.

13. A solid-state battery according to claim 12, characterized in that, The preparation method of the positive electrode sheet includes the following steps: NCM811, Li6PS5Cl, carbon nanotubes, and polytetrafluoroethylene are mixed, ground, and hot roll-pressed according to a mass ratio of 80 to 85: 10 to 20: 1 to 1.5: 1 to 1.5 to obtain a positive electrode active layer. After the positive electrode active layer is compounded with aluminum foil, the positive electrode of the solid battery is obtained.

14. A solid-state battery according to claim 12, characterized in that, The preparation method of the electrolyte membrane includes the following steps: the electrolyte and polytetrafluoroethylene are mixed according to a mass ratio of 94 to 98: 6 to 2, ground, and hot roll-pressed to obtain the electrolyte membrane of the solid battery; the electrolyte is at least one of a sulfide electrolyte, a polymer electrolyte, an oxide electrolyte, and a halide electrolyte.

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