Solid-state battery multifunctional composite electrolyte membrane and preparation method and application thereof

Abstract

The invention provides a solid-state battery multifunctional composite electrolyte membrane and a preparation method and application thereof, and belongs to the field of all-solid-state lithium battery materials. The sulfide electrolyte prepared by the invention is used as an effective inorganic regulator, and can finely regulate and control the pore structure and the crystallization characteristic of CSE, so as to realize a rich-pore CSE membrane with excellent mechanical property and high ionic conductivity, so that an SEI interface layer rich in LiF / LiCl is constructed in situ between a Li anode and a CSE interface in a subsequently obtained lithium battery, and the performance of the lithium battery is improved. The direct contact between the sulfide electrolyte and the lithium anode is effectively isolated, and the formation and expansion of lithium dendrites are obviously inhibited; and meanwhile, the continuous and uniform SEI layer greatly promotes the uniform deposition behavior of lithium in the electroplating / stripping process by virtue of relatively high interface energy and excellent adhesion performance, and further enhances the interface compatibility between an electrolyte membrane and a lithium anode, thereby ensuring high reversibility in the cycle process of the battery.

Description

Technical Field

[0001] The present invention relates to the field of all-solid-state lithium battery materials, and in particular to a multifunctional composite electrolyte membrane for solid-state batteries and a preparation method and application thereof. Background Art

[0002] Rechargeable lithium-ion batteries (LIBs) have been widely used in electronic and energy storage devices, but graphite anodes are limited by energy density and cannot meet the requirements of high energy and long life, and organic liquid electrolytes are flammable and pose safety risks. -1 ) and low redox potential (-3.04Vvs.H / H + ), is regarded as a potential anode material for improving energy density. In order to balance high energy density and safety, the research on all-solid-state lithium metal batteries (ASSLMBs) using solid electrolytes (SEs) instead of liquid electrolytes has attracted much attention.

[0003] Sulfide solid electrolytes (SSEs) have high ionic conductivity (10 -3 ~10 -2 ) and good electrochemical compatibility. ASSLMBs based on SSEs show excellent cycling stability and rate capability, but the poor interface compatibility between SSEs and Li anode and the problem of Li dendrite formation limit their application. In order to reduce the volume expansion caused by Li dendrites, a granular SSE layer sintered by high pressure pressing is often used, but its thickness often exceeds 500μm, which not only affects the energy density, but also has high preparation cost, low production efficiency, and is incompatible with existing coating processes. Therefore, it is key to design an ASSLMBs material system with controllable thickness, dense structure and good interface compatibility.

[0004] In recent years, the method of combining sulfide and polymer has made a breakthrough in the preparation of independent composite solid electrolyte (CSE) films with high ionic conductivity. However, previous studies have focused on reducing the film thickness and ignored the interfacial stability between the CSE film and the Li anode, resulting in poor stability of the electrolyte film and unsatisfactory electrochemical performance.

[0005] Therefore, how to improve the interfacial stability between the CSE film and the Li anode has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0006] The purpose of the present invention is to provide a multifunctional composite electrolyte membrane for a solid-state battery and a preparation method and application thereof. The multifunctional composite electrolyte membrane for a solid-state battery provided by the present invention has enhanced ionic conductivity, a broadened electrochemical window, excellent lithium dendrite inhibition ability and ideal interface compatibility.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a multifunctional composite electrolyte membrane for a solid-state battery, comprising the following steps:

[0009] (1) Li 2 S.P. 2 S 5 After mixing with LiCl, cold pressing, heat treatment and grinding are carried out in sequence to obtain a sulfide electrolyte;

[0010] (2) mixing PVDF-HFP, a solvent and a lithium salt to obtain a mixture, and then adding the sulfide electrolyte obtained in step (1) to the mixture to mix and obtain an electrolyte membrane precursor;

[0011] (3) The electrolyte membrane precursor obtained in step (2) is dried and cold pressed in sequence to obtain a multifunctional composite electrolyte membrane for a solid-state battery.

[0012] Preferably, in step (1), Li 2 S.P. 2 S 5 The molar ratio of LiCl is (4-5):1:(2-3).

[0013] Preferably, the cold pressing pressure in step (1) is 1.2 to 1.4 T, and the cold pressing time is 5 to 10 min.

[0014] Preferably, the heat treatment temperature in step (1) is 500-550° C., and the heat treatment time is 10-12 hours.

[0015] Preferably, in step (2), the solvent is an organic solvent, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0016] Preferably, in step (2), the mass ratio of PVDF-HFP to lithium salt is (1-3):1.

[0017] Preferably, in the step (2), based on the total mass percentage of PVDF-HFP, lithium salt and sulfide electrolyte being 100%, the mass percentage of the sulfide electrolyte is ≤4%.

[0018] Preferably, the cold pressing pressure in step (3) is 0.2 to 0.5 T, and the cold pressing time is 5 to 10 min.

[0019] The present invention provides a solid-state battery multifunctional composite electrolyte membrane prepared by the preparation method described in the above technical solution.

[0020] The present invention provides the application of the solid-state battery multifunctional composite electrolyte membrane described in the above technical solution in a lithium battery.

[0021] The present invention provides a method for preparing a multifunctional composite electrolyte membrane for a solid-state battery, comprising the following steps: (1) 2 S.P. 2 S 5 and LiCl, followed by cold pressing, heat treatment and grinding to obtain a sulfide electrolyte; (2) mixing PVDF-HFP, a solvent and a lithium salt to obtain a mixture, and then adding the sulfide electrolyte obtained in step (1) to the mixture and mixing to obtain an electrolyte membrane precursor; (3) drying and cold pressing the electrolyte membrane precursor obtained in step (2) to obtain a multifunctional composite electrolyte membrane for solid-state batteries. The sulfide electrolyte prepared by the present invention, as an effective inorganic regulator, can finely control the pore structure and crystallization characteristics of CSE to achieve a porous CSE membrane with excellent mechanical properties and high ionic conductivity, so that in the subsequent lithium battery, a layer of SEI interface layer rich in LiF / LiCl is in situ constructed between the interface of Li anode and CSE, which not only effectively isolates the direct contact between the sulfide electrolyte and the lithium anode, but also significantly inhibits the formation and expansion of lithium dendrites; at the same time, the continuous and uniform SEI layer greatly promotes the uniform deposition behavior of lithium in the electroplating / stripping process by virtue of its high interfacial energy and excellent adhesion performance, and further enhances the interfacial compatibility between the electrolyte membrane and the lithium anode, thereby ensuring the high reversibility of the battery cycle process. The composite electrolyte membrane exhibits excellent physical properties and ideal electrochemical properties, and is a potential all-solid-state lithium battery material. The results of the embodiments show that the lithium symmetric battery prepared by the solid-state battery multifunctional composite electrolyte membrane provided by the present invention is far superior to the comparative example in terms of ionic conductivity, lithium ion migration number, electrochemical window and cycle performance. The ionic conductivity value of the lithium symmetric battery can be increased by up to 5.2 times; in addition, the lithium symmetric battery can achieve stable lithium plating / stripping behavior for more than 2000 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart for preparing a multifunctional composite electrolyte membrane for a solid-state battery provided by the present invention;

[0023] Figure 2 This is a physical picture of the solid-state battery multifunctional composite electrolyte membrane prepared in Example 2;

[0024] Figure 3 The scanning electron microscope and corresponding mapping image of the solid-state battery multifunctional composite electrolyte membrane prepared in Example 2;

[0025] Figure 4 X-ray diffraction patterns of the composite electrolyte membranes prepared in Examples 1 to 3 and Comparative Example 1;

[0026] Figure 5The EIS impedance spectra of the composite electrolyte membranes prepared in Examples 1 to 3 and Comparative Example 1;

[0027] Figure 6 LSV curves of lithium symmetric batteries prepared in Application Example 2 and Comparative Application Example 1;

[0028] Figure 7 At 0.1 mA cm -2 Constant current cycle curves of the lithium symmetric batteries prepared in Application Example 2 and Comparative Application Example 1 under current density. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a multifunctional composite electrolyte membrane for a solid-state battery, comprising the following steps:

[0030] (1) Li 2 S.P. 2 S 5 After mixing with LiCl, cold pressing, heat treatment and grinding are carried out in sequence to obtain a sulfide electrolyte;

[0031] (2) mixing PVDF-HFP, a solvent and a lithium salt to obtain a mixture, and then adding the sulfide electrolyte obtained in step (1) to the mixture to mix and obtain an electrolyte membrane precursor;

[0032] (3) The electrolyte membrane precursor obtained in step (2) is dried and cold pressed in sequence to obtain a multifunctional composite electrolyte membrane for a solid-state battery.

[0033] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art.

[0034] The present invention will Li 2 S.P. 2 S 5 After mixing with LiCl, it is cold pressed, heat treated and ground in sequence to obtain a sulfide electrolyte.

[0035] In the present invention, the Li 2 S.P. 2 S 5 The present invention has no particular limitation on the specific operation of the vacuum heating, as long as it can remove the moisture in the raw materials.

[0036] In the present invention, the Li 2 S.P. 2 S 5 The molar ratio of LiCl is preferably (4-5):1:(2-3), more preferably 4:1:3. 2 S.P.2 S 5 The relationship between the dosage of LiCl and LiCl can control the composition of the sulfide electrolyte. By optimizing its dosage, the sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 , namely LPSC1.5; LPSC1.5, as an effective inorganic filler, can further fine-tune the pore structure and crystallization properties of the multifunctional composite electrolyte membrane of solid-state batteries to achieve a porous CSE membrane with excellent mechanical properties and high ionic conductivity.

[0037] In the present invention, the Li 2 S.P. 2 S 5 The mixing method with LiCl is preferably grinding and ball milling in sequence; the speed of the ball mill is preferably 400-600 r / min, more preferably 450-550 r / min, and further preferably 500 r / min; the time of the ball milling is preferably 10-18 h, more preferably 12-15 h; the atmosphere of the ball milling is preferably a protective atmosphere, more preferably argon; the ball milling is preferably carried out in a high-energy ball mill. The present invention has no particular limitation on the speed and time of the grinding, and can make Li 2 S.P. 2 S 5 The present invention has no particular limitation on the specific model and source of the high-energy ball mill, and a commercially available high-energy ball mill known to those skilled in the art can be used. The present invention can fully mix and finely grind the raw materials through ball milling.

[0038] In the present invention, the pressure of the cold pressing is preferably 1.2-1.4T, more preferably 1.3T; the time of the cold pressing is preferably 5-10min, more preferably 6-9min, and further preferably 7-8min. In the present invention, the cold pressing is preferably carried out in a press. The present invention has no special limitation on the specific model and source of the press, and a commercially available press familiar to those skilled in the art can be used. The present invention can improve the close arrangement between particles and enhance the compaction density by cold pressing.

[0039] In the present invention, the temperature of the heat treatment is preferably 500-550°C, more preferably 510-540°C, and further preferably 520-530°C; the time of the heat treatment is preferably 10-12h, more preferably 11h; the heating rate to the heat treatment temperature is preferably 3-6°C / min, more preferably 4-5°C / min; the atmosphere of the heat treatment is preferably a protective atmosphere, more preferably nitrogen; the cooling method of the heat treatment is preferably natural cooling. The present invention can promote deep reaction between raw materials and optimize material structure through heat treatment.

[0040] The present invention has no particular limitation on the specific operation of the grinding, as long as the heat-treated product can be converted into a powder form with uniform size.

[0041] In the present invention, the particle size of the sulfide electrolyte is preferably 1 to 10 μm.

[0042] In the present invention, the sulfide electrolyte is preferably stored in a glove box. The present invention has no particular limitation on the specific model and source of the glove box, and a commercially available glove box well known to those skilled in the art can be used. The present invention stores the sulfide electrolyte in a glove box to avoid problems such as oxidation after contact with air.

[0043] After obtaining the sulfide electrolyte, the present invention mixes PVDF-HFP, a solvent and a lithium salt to obtain a mixture, and then adds the sulfide electrolyte to the mixture for mixing to obtain an electrolyte membrane precursor (LPSC1.5 / PVDF-HFP / LiTFSI).

[0044] In the present invention, the solvent is preferably an organic solvent, more preferably any one or more of toluene, xylene, NN dimethylformamide (DMF), carbon tetrachloride, chloroform and ethyl acetate.

[0045] In the present invention, the lithium salt is preferably lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0046] In the present invention, the PVDF-HFP and the lithium salt are preferably subjected to vacuum heating before mixing. The present invention has no particular limitation on the specific operation of the vacuum heating, as long as it can remove the moisture in the raw materials.

[0047] In the present invention, the PVDF-HFP, solvent and lithium salt are preferably mixed by heating and stirring after mixing the PVDF-HFP and the solvent until the solution is converted into a clear and transparent viscous liquid, and then adding the lithium salt and continuing to stir for 6 to 12 hours to ensure complete dissolution. In the present invention, the speed of the heating and stirring is preferably 600 to 800 r / min; the temperature of the heating and stirring is preferably 50 to 60°C; the time of the heating and stirring is preferably 2 to 4 hours, more preferably 3 hours; the heating and stirring method is preferably magnetic stirring. As an embodiment of the present invention, the speed of the heating and stirring can be 650 to 750 r / min, and can also be 700 r / min; the temperature of the heating and stirring can be 50°C, 52°C, 54°C, 55°C, 56°C, 58°C or 60°C. The present invention can make PVDF-HFP, solvent and lithium salt mixed evenly by adopting the above method.

[0048] In the present invention, the method of adding the sulfide electrolyte to the mixture for mixing is preferably ultrasonic stirring; the rotation speed of the ultrasonic stirring is preferably 600-800 r / min; the ultrasonic power of the ultrasonic stirring is preferably 100-180 W; the ultrasonic stirring time is preferably 1-2 h. As an embodiment of the present invention, the rotation speed of the ultrasonic stirring can be 650-750 r / min, or 700 r / min; the ultrasonic power of the ultrasonic stirring can be 120-160 W, or 140-150 W. The present invention can make the sulfide electrolyte uniformly dispersed by ultrasonic stirring.

[0049] In the present invention, the mass ratio of the PVDF-HFP and the lithium salt is preferably (1-3):1, more preferably 2:1; taking the total mass percentage of PVDF-HFP, lithium salt and sulfide electrolyte as 100%, the mass percentage of the sulfide electrolyte is preferably ≤4%, more preferably 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%; the total mass ratio of the PVDF-HFP, lithium salt and sulfide electrolyte to the volume of the solvent is preferably (1-2) g:10 mL, more preferably 1.5 g:10 mL.

[0050] In the present invention, the mixed product is preferably allowed to stand after the mixing is completed; the standing time is preferably 5 to 10 minutes. As an embodiment of the present invention, the standing time can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes. The present invention can eliminate any possible bubbles or unevenly dispersed particles by standing.

[0051] After obtaining the electrolyte membrane precursor, the present invention sequentially dries and cold-presses the electrolyte membrane precursor to obtain a multifunctional composite electrolyte membrane for a solid-state battery.

[0052] In the present invention, the drying method is preferably natural volatilization and vacuum drying performed in sequence.

[0053] In the present invention, the natural volatilization is preferably carried out by paving the electrolyte membrane precursor in a mold and then volatilizing it naturally. The present invention has no special limitation on the material of the mold, and a commercially available mold familiar to those skilled in the art can be used. As an embodiment of the present invention, the mold can be a polytetrafluoroethylene mold. The present invention has no special limitation on the specific operation of paving, and it can be used as long as the electrolyte membrane precursor can be evenly paved. As an embodiment of the present invention, the paving can be to use a scraper to evenly pave the electrolyte membrane precursor in a polytetrafluoroethylene mold.

[0054] In the present invention, the temperature of the natural volatilization is preferably room temperature; the time of the natural volatilization is preferably 10 to 12 hours, more preferably 11 hours; the natural volatilization is preferably carried out in a glove box filled with argon atmosphere. The present invention can preliminarily remove the solvent in the electrolyte membrane precursor through natural volatilization.

[0055] In the present invention, the vacuum drying temperature is preferably 80 to 150°C; the vacuum drying time is 12 to 24 hours. As an embodiment of the present invention, the vacuum drying temperature may be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C; the vacuum drying time may be 12 hours, 15 hours, 18 hours, 21 hours or 24 hours. The present invention can completely remove the residual solvent and solidify the composite electrolyte membrane through vacuum drying.

[0056] In the present invention, the cold pressing pressure is preferably 0.2-0.5T, more preferably 0.3-0.4T; the cold pressing time is preferably 5-10min, more preferably 6-9min, and further preferably 7-8min. In the present invention, the cold pressing is preferably carried out in a press. The present invention does not specifically limit the specific model and source of the press, and a commercially available press familiar to those skilled in the art can be used. By cold pressing, the present invention can improve the close arrangement between particles and enhance the compaction density, so that the multifunctional composite electrolyte membrane of the solid-state battery can construct an in-situ LiF / LiCl-rich artificial SEI interface layer on the surface of the lithium anode.

[0057] The sulfide electrolyte prepared by the present invention, as an effective inorganic regulator, can finely control the pore structure and crystallization characteristics of CSE to achieve a porous CSE membrane with excellent mechanical properties and high ionic conductivity, so that in the subsequent lithium battery, a layer of SEI interface layer rich in LiF / LiCl is in situ constructed between the interface of Li anode and CSE, which not only effectively isolates the direct contact between the sulfide electrolyte and the lithium anode, but also significantly inhibits the formation and expansion of lithium dendrites; at the same time, the continuous and uniform SEI layer greatly promotes the uniform deposition behavior of lithium in the electroplating / stripping process by virtue of its high interfacial energy and excellent adhesion performance, and further enhances the interfacial compatibility between the electrolyte membrane and the lithium anode, thereby ensuring the high reversibility of the battery cycle process. The composite electrolyte membrane exhibits excellent physical properties and ideal electrochemical properties, and is a potential all-solid-state lithium battery material.

[0058] The present invention utilizes a solution method to prepare an electrolyte membrane, which has the advantages of low cost, good economic benefits, simple process, and industrialization, and is conducive to large-scale industrial promotion.

[0059] The present invention also provides a solid-state battery multifunctional composite electrolyte membrane prepared by the preparation method described in the above technical solution.

[0060] In the present invention, the multifunctional composite electrolyte membrane of the solid-state battery is preferably a LPSC1.5 / PVDF-HFP / LiTFSI membrane.

[0061] In the present invention, the mass percentage of the sulfide electrolyte in the solid-state battery multifunctional composite electrolyte membrane is preferably ≤4%, and more preferably 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%.

[0062] In the present invention, the thickness of the solid-state battery multifunctional composite electrolyte membrane is preferably ≤100 μm, more preferably 1 to 100 μm. The solid-state battery multifunctional composite electrolyte membrane provided by the present invention preferably has a uniform pore-rich structure. As an embodiment of the present invention, the thickness of the solid-state battery multifunctional composite electrolyte membrane can be 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0063] The present invention also provides the application of the solid-state battery multifunctional composite electrolyte membrane described in the above technical solution in a lithium battery.

[0064] In the present invention, the lithium battery is preferably a lithium symmetrical battery; the preparation method of the lithium symmetrical battery is preferably: using hot pressing technology, sandwiching the solid-state battery multifunctional composite electrolyte membrane between two lithium anodes at 50-80°C, and continuously treating it under a pressure of 0.1-0.3T for 5-15min to obtain a lithium symmetrical battery, more preferably: using hot pressing technology, sandwiching the solid-state battery multifunctional composite electrolyte membrane between two lithium anodes at 60°C, and continuously treating it under a pressure of 0.2T for 10min to obtain a lithium symmetrical battery.

[0065] In the lithium battery prepared by using the solid-state battery multifunctional composite electrolyte membrane provided by the present invention, an SEI layer rich in LiF and LiCl is generated in situ at the interface between the Li anode and the solid-state battery multifunctional composite electrolyte membrane, which avoids direct physical contact between the sulfide electrolyte and the lithium anode and significantly curbs the initiation and spread of lithium dendrites; at the same time, this continuous and uniform LiF / LiCl-enriched SEI layer, with its high interfacial energy and excellent adhesion, acts like a solid "rivet", tightly and firmly anchoring the lithium anode and the electrolyte membrane together, greatly promoting the uniform distribution and deposition of lithium during electroplating and stripping, and further strengthening the interface compatibility between the electrolyte membrane and the lithium anode, thereby ensuring that the lithium battery exhibits high reversibility and stability during the cycle process.

[0066] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] The preparation process of the multifunctional composite electrolyte membrane for solid-state batteries provided by the embodiment of the present invention is as follows: Figure 1 As shown. Figure 1 It can be seen that in the present invention, after mixing PVDF-HFP, an organic solvent and a lithium salt LiTFSI, a sulfide electrolyte LPSC1.5 is added for ultrasonic stirring to obtain a LPSC1.5 / PVDF-HFP / LiTFSI precursor, and then the LPSC1.5 / PVDF-HFP / LiTFSI precursor is dried and cast to obtain a LPSC1.5 / PVDF-HFP / LiTFSI membrane.

[0068] Example 1

[0069] A method for preparing a multifunctional composite electrolyte membrane for a solid-state battery comprises the following steps:

[0070] (1) Li 2 S.P. 2 S 5 and LiCl were heated in a vacuum in an agate mortar to remove moisture, and then Li 2 S.P. 2 S 5 The mixture is ground and preliminarily mixed with LiCl, and then ball-milled in a high-energy ball mill. After ball milling, it is cold-pressed in a press, and then placed in a heat treatment furnace and heated to 550°C at a heating rate of 5°C for 10 hours. After naturally cooling to room temperature, it is ground to convert the sintered block obtained by the heat treatment into a fine and uniform powder form to obtain a sulfide electrolyte with a particle size of 1 to 10 μm, which is denoted as LPSC1.5 and stored in a glove box. The Li 2 S.P. 2 S 5 The molar ratio of the ...

[0071] (2) PVDF-HFP and LiTFSI were respectively subjected to vacuum heating to remove moisture, PVDF-HFP and the solvent were mixed and heated to 55°C and magnetically stirred at a speed of 600 r / min for 2 h until the solution became a clear and transparent viscous liquid, and then LiTFSI was added and stirred overnight to ensure complete dissolution to obtain a mixture, and then LPSC1.5 obtained in step (1) was added to the mixture and ultrasonically stirred for 1 h, and finally allowed to stand for 10 min to obtain an electrolyte membrane precursor, which was recorded as 2% LPSC1.5 / PVDF-HFP / LiTFSI precursor The mass ratio of PVDF-HFP and LiTFSI is 2:1; the mass percentage of LPSC1.5 is 2% based on the total mass percentage of PVDF-HFP, LiTFSI and LPSC1.5 as 100%; the solvent is a mixed solvent of DMF and toluene, and the volume ratio of DMF and toluene is 2:1; the total mass of PVDF-HFP, LiTFSI and LPSC1.5 and the volume ratio of the solvent are 1.5g:10mL; the speed of the ultrasonic stirring is 600r / min, and the ultrasonic power of the ultrasonic stirring is 100W;

[0072] (3) Using a scraper, the 2% LPSC1.5 / PVDF-HFP / LiTFSI precursor obtained in step (2) was evenly spread on a polytetrafluoroethylene mold, and naturally evaporated in a glove box filled with argon atmosphere at room temperature for 10 hours, and then vacuum dried in a vacuum drying oven at 120° C. for 12 hours, and finally cold pressed on a press at a pressure of 0.2 T for 5 minutes to obtain a solid-state battery multifunctional composite electrolyte membrane with a thickness of 50 μm, recorded as a 2% LPSC1.5 / PVDF-HFP / LiTFSI membrane.

[0073] Application Example 1

[0074] The preparation method of 2% LPSC1.5 / PVDF-HFP / LiTFSI / / Li lithium symmetric battery is as follows: using hot pressing technology, the 2% LPSC1.5 / PVDF-HFP / LiTFSI membrane provided in Example 1 is sandwiched between two lithium anodes at 60°C, and continuously treated under a pressure of 0.2T for 10 minutes to finally prepare a 2% LPSC1.5 / PVDF-HFP / LiTFSI / / Li lithium symmetric battery.

[0075] Example 2

[0076] A method for preparing a multifunctional composite electrolyte membrane for a solid-state battery comprises the following steps:

[0077] (1) Li 2 S.P. 2 S 5and LiCl were heated in a vacuum in an agate mortar to remove moisture, and then Li 2 S.P. 2 S 5 The mixture is ground and preliminarily mixed with LiCl, and then ball-milled in a high-energy ball mill. After ball milling, it is cold-pressed in a press, and then placed in a heat treatment furnace and heated to 550°C at a heating rate of 5°C for 10 hours. After naturally cooling to room temperature, it is ground to convert the sintered block obtained by the heat treatment into a fine and uniform powder form to obtain a sulfide electrolyte with a particle size of 1 to 10 μm, which is denoted as LPSC1.5 and stored in a glove box. The Li 2 S.P. 2 S 5 The molar ratio of the ...

[0078] (2) PVDF-HFP and LiTFSI were respectively subjected to vacuum heating to remove moisture, PVDF-HFP and the solvent were mixed and heated to 55°C and magnetically stirred at a speed of 600 r / min for 2 h until the solution became a clear and transparent viscous liquid, and then LiTFSI was added and stirred overnight to ensure complete dissolution to obtain a mixture, and then LPSC1.5 obtained in step (1) was added to the mixture and ultrasonically stirred for 1 h, and finally allowed to stand for 10 min to obtain an electrolyte membrane precursor, which was recorded as 3% LPSC1.5 / PVDF-HFP / LiTFSI precursor The mass ratio of PVDF-HFP and LiTFSI is 2:1; the mass percentage of LPSC1.5 is 3% based on the total mass percentage of PVDF-HFP, LiTFSI and LPSC1.5 as 100%; the solvent is a mixed solvent of DMF and toluene, and the volume ratio of DMF and toluene is 2:1; the total mass of PVDF-HFP, LiTFSI and LPSC1.5 and the volume ratio of the solvent are 1.5g:10mL; the speed of the ultrasonic stirring is 600r / min, and the ultrasonic power of the ultrasonic stirring is 100W;

[0079] (3) Using a scraper, the 3% LPSC1.5 / PVDF-HFP / LiTFSI precursor obtained in step (2) was evenly spread on a polytetrafluoroethylene mold, and naturally evaporated in a glove box filled with argon atmosphere at room temperature for 10 hours, and then vacuum dried in a vacuum drying oven at 120° C. for 12 hours, and finally cold pressed on a press at a pressure of 0.2 T for 5 minutes to obtain a solid-state battery multifunctional composite electrolyte membrane with a thickness of 50 μm, recorded as a 3% LPSC1.5 / PVDF-HFP / LiTFSI membrane.

[0080] The actual picture of the solid-state battery multifunctional composite electrolyte membrane prepared in Example 2 is as follows Figure 2 As shown. Figure 2 It can be seen that the solid-state battery multifunctional composite electrolyte membrane prepared by the present invention has a smooth surface and good toughness and will not break after bending.

[0081] The scanning electron microscope and corresponding mapping image of the solid-state battery multifunctional composite electrolyte membrane prepared in Example 2 are as follows: Figure 3 As shown. Figure 3 It can be seen that the composite electrolyte membrane prepared by the present invention has a rich pore structure inside, and each element is evenly dispersed in the composite electrolyte membrane.

[0082] Application Example 2

[0083] The preparation method of the 3% LPSC1.5 / PVDF-HFP / LiTFSI / / Li lithium symmetric battery is as follows: using hot pressing technology, the 3% LPSC1.5 / PVDF-HFP / LiTFSI membrane provided in Example 2 is sandwiched between two lithium anodes at 60°C, and continuously treated under a pressure of 0.2T for 10 minutes to finally prepare a 3% LPSC1.5 / PVDF-HFP / LiTFSI / / Li lithium symmetric battery.

[0084] Example 3

[0085] A method for preparing a multifunctional composite electrolyte membrane for a solid-state battery comprises the following steps:

[0086] (1) Li 2 S.P. 2 S 5 and LiCl were heated in a vacuum in an agate mortar to remove moisture, and then Li 2 S.P. 2 S 5 The mixture is ground and preliminarily mixed with LiCl, and then ball-milled in a high-energy ball mill. After ball milling, it is cold-pressed in a press, and then placed in a heat treatment furnace and heated to 550°C at a heating rate of 5°C for 10 hours. After naturally cooling to room temperature, it is ground to convert the sintered block obtained by the heat treatment into a fine and uniform powder form to obtain a sulfide electrolyte with a particle size of 1 to 10 μm, which is denoted as LPSC1.5 and stored in a glove box. The Li 2 S.P. 2 S 5The molar ratio of the ...

[0087] (2) PVDF-HFP and LiTFSI were respectively subjected to vacuum heating to remove moisture, PVDF-HFP and the solvent were mixed and heated to 55°C and magnetically stirred at a speed of 600 r / min for 2 h until the solution became a clear and transparent viscous liquid, and then LiTFSI was added and stirred overnight to ensure complete dissolution to obtain a mixture, and then LPSC1.5 obtained in step (1) was added to the mixture and ultrasonically stirred for 1 h, and finally allowed to stand for 10 min to obtain an electrolyte membrane precursor, which was recorded as 4% LPSC1.5 / PVDF-HFP / LiTFSI precursor The mass ratio of PVDF-HFP and LiTFSI is 2:1; the mass percentage of LPSC1.5 is 4% based on the total mass percentage of PVDF-HFP, LiTFSI and LPSC1.5 as 100%; the solvent is a mixed solvent of DMF and toluene, and the volume ratio of DMF and toluene is 2:1; the total mass of PVDF-HFP, LiTFSI and LPSC1.5 and the volume ratio of the solvent are 1.5g:10mL; the speed of the ultrasonic stirring is 600r / min, and the ultrasonic power of the ultrasonic stirring is 100W;

[0088] (3) Using a scraper, the 4% LPSC1.5 / PVDF-HFP / LiTFSI precursor obtained in step (2) was evenly spread on a polytetrafluoroethylene mold, and naturally evaporated in a glove box filled with argon atmosphere at room temperature for 10 hours, and then vacuum dried in a vacuum drying oven at 120° C. for 12 hours, and finally cold pressed on a press at a pressure of 0.2 T for 5 minutes to obtain a solid-state battery multifunctional composite electrolyte membrane with a thickness of 50 μm, recorded as a 4% LPSC1.5 / PVDF-HFP / LiTFSI membrane.

[0089] Application Example 3

[0090] The preparation method of the 4% LPSC1.5 / PVDF-HFP / LiTFSI / / Li lithium symmetric battery is as follows: using hot pressing technology, the 4% LPSC1.5 / PVDF-HFP / LiTFSI membrane provided in Example 3 is sandwiched between two lithium anodes at 60°C, and is continuously treated under a pressure of 0.2T for 10 minutes to finally prepare a 4% LPSC1.5 / PVDF-HFP / LiTFSI / / Li lithium symmetric battery.

[0091] Comparative Example 1

[0092] A method for preparing a PVDF-HFP / LiTFSI composite electrolyte membrane comprises the following steps:

[0093] (1) PVDF-HFP and LiTFSI are respectively vacuum heated to remove moisture, PVDF-HFP and solvent are mixed and heated to 55°C and magnetically stirred at a speed of 600 r / min for 2 h until the solution turns into a clear and transparent viscous liquid, and then LiTFSI is added and stirred overnight to ensure complete dissolution to obtain a mixture, thereby obtaining an electrolyte membrane precursor, which is recorded as PVDF-HFP / LiTFSI precursor; the mass ratio of PVDF-HFP and LiTFSI is 2:1; the solvent is a mixed solvent of DMF and toluene, and the volume ratio of DMF and toluene is 2:1; the ratio of the total mass of PVDF-HFP and LiTFSI to the volume of the solvent is 1.5 g:10 mL;

[0094] (2) Using a scraper, the PVDF-HFP / LiTFSI precursor obtained in step (1) was evenly spread on a polytetrafluoroethylene mold, and naturally evaporated in a glove box filled with argon atmosphere at room temperature for 10 hours, and then vacuum dried in a vacuum drying oven at 120° C. for 12 hours, and finally cold pressed on a press at a pressure of 0.2 T for 5 minutes to obtain a composite electrolyte membrane with a thickness of 50 μm, which was recorded as a PVDF-HFP / LiTFSI membrane.

[0095] Comparative application example 1

[0096] The preparation method of the PVDF-HFP / LiTFSI / / Li lithium symmetric battery is as follows: using hot pressing technology, the PVDF-HFP / LiTFSI membrane provided in Comparative Example 1 is sandwiched between two lithium anodes at 60°C, and continuously treated under a pressure of 0.2T for 10 minutes, and finally a PVDF-HFP / LiTFSI / / Li lithium symmetric battery is prepared.

[0097] The X-ray diffraction patterns of the composite electrolyte membranes prepared in Examples 1 to 3 and Comparative Example 1 are as follows: Figure 4 As shown. Figure 4 It can be seen that after introducing a certain amount of sulfide electrolyte LPSC1.5, the peak intensity of the composite electrolyte membrane tends to weaken. This is mainly because the inorganic filler LPSC1.5 significantly reduces the crystallinity of PVDF-HFP, thereby enhancing the interaction between ions and polymer chains, thereby hindering the recrystallization of PVDF-HFP and promoting the formation of more amorphous regions, thereby increasing the ion transfer rate in the composite electrolyte membrane.

[0098] The electrochemical performance of the lithium symmetrical battery prepared according to Examples 1 to 3 and Comparative Application Example 1 was tested, and the results obtained are as follows: Figures 5 to 7 And as shown in Table 1.

[0099] The EIS impedance spectra of the composite electrolyte membranes prepared in Examples 1 to 3 and Comparative Example 1 are as follows: Figure 5 As shown. Figure 5 It can be seen that the present invention can significantly reduce the EIS impedance by introducing a certain amount of sulfide electrolyte LPSC1.5 into the composite electrolyte membrane. Among them, when the dosage of LPSC1.5 in the composite electrolyte membrane is 3%, the EIS impedance value is the lowest, indicating that the solution provided by the present invention can improve the ionic conductivity of the composite electrolyte membrane.

[0100] The LSV curves of the lithium symmetric batteries prepared in Application Example 2 and Comparative Application Example 1 are as follows: Figure 6 As shown. Figure 6 It can be seen that after introducing a certain amount of sulfide electrolyte LPSC1.5 into the composite electrolyte membrane, the obtained lithium symmetric battery has a higher electrochemical window. Among them, when the dosage of LPSC1.5 in the composite electrolyte membrane is 3%, the electrochemical window of the lithium symmetric battery is the highest, reaching 5.24V.

[0101] At 0.1 mA cm -2 At the current density, the constant current cycle curves of the lithium symmetric batteries prepared in Application Example 2 and Comparative Application Example 1 are as follows: Figure 7 As shown. Figure 7 It can be seen that after introducing a certain amount of sulfide electrolyte LPSC1.5 into the composite electrolyte membrane, the cycle performance of the lithium symmetrical battery obtained in the present invention is significantly improved. Among them, when the dosage of LPSC1.5 in the composite electrolyte membrane is 3%, the cycle performance of the lithium symmetrical battery exceeds 2000h.

[0102] Table 1 Electrochemical performance of lithium symmetric batteries prepared in Application Examples 1 to 3 and Comparative Example Application Example 1

[0103]

[0104] It can be seen from Table 1 that the lithium symmetric battery prepared by using the solid-state battery multifunctional composite electrolyte membrane provided in Examples 1 to 3 is much better than the comparative example in terms of ionic conductivity, lithium ion migration number, electrochemical window and cycle performance. In particular, the lithium symmetric battery prepared by the 3% LPSC1.5 / PVDF-HFP / LiTFSI membrane provided in Example 3 exhibits an ultra-high ionic conductivity value (0.752 mS cm -1), which is 5.2 times that of the lithium symmetrical battery prepared by the PVDF-HFP / LiTFSI membrane provided in Comparative Example 1. In addition, the lithium symmetrical battery prepared in Application Example 3 can achieve stable lithium plating / stripping behavior for more than 2000h, which is much better than the lithium symmetrical battery assembled in Comparative Application Example 1. It shows that the 3% LPSC1.5 / PVDF-HFP / LiTFSI membrane provided by the present invention has enhanced ionic conductivity, broadened electrochemical window, excellent lithium dendrite inhibition ability and ideal interface compatibility, which enhances the advantages of the solid-state battery multifunctional composite electrolyte membrane in the preparation of all-solid-state lithium batteries. Combined with the characteristics of simple preparation process and low cost of raw materials used, it is shown that the solid-state battery multifunctional composite electrolyte membrane provided by the present invention has a good application prospect for all-solid-state lithium batteries.

[0105] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional composite electrolyte membrane for a solid-state battery, comprising the following steps: (1) Li2S, P2S5 and LiCl are mixed and then cold pressed, heat treated and ground in sequence to obtain a sulfide electrolyte; (2) mixing PVDF-HFP, a solvent and a lithium salt to obtain a mixture, and then adding the sulfide electrolyte obtained in step (1) to the mixture to mix and obtain an electrolyte membrane precursor; (3) The electrolyte membrane precursor obtained in step (2) is dried and cold pressed in sequence to obtain a multifunctional composite electrolyte membrane for a solid-state battery.

2. The preparation method according to claim 1, characterized in that: In the step (1), the molar ratio of Li2S, P2S5 and LiCl is (4-5):1:(2-3).

3. The preparation method according to claim 1, characterized in that: The cold pressing pressure in step (1) is 1.2 to 1.4 T, and the cold pressing time is 5 to 10 min.

4. The preparation method according to claim 1, characterized in that: The heat treatment temperature in step (1) is 500-550° C., and the heat treatment time is 10-12 hours.

5. The preparation method according to claim 1, characterized in that: In the step (2), the solvent is an organic solvent, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

6. The preparation method according to claim 1, characterized in that: The mass ratio of PVDF-HFP to lithium salt in the step (2) is (1-3):

1.

7. The preparation method according to claim 1, characterized in that: In the step (2), based on the total mass percentage of PVDF-HFP, lithium salt and sulfide electrolyte being 100%, the mass percentage of the sulfide electrolyte is ≤4%.

8. The preparation method according to claim 1, characterized in that: The cold pressing pressure in step (3) is 0.2 to 0.5T, and the cold pressing time is 5 to 10 minutes.

9. A solid-state battery multifunctional composite electrolyte membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the solid-state battery multifunctional composite electrolyte membrane according to claim 9 in lithium batteries.

Images