Solid electrolyte diaphragm as well as preparation method and application thereof

Abstract

The embodiment of the invention relates to a solid electrolyte diaphragm as well as a preparation method and application thereof, and the solid electrolyte diaphragm comprises a base membrane and a coating, the coating is attached to one side or two sides of the base membrane or partially permeates into pores of the base membrane; the material composition of the coating comprises a solid electrolyte material, the chemical general formula of the solid electrolyte material is L x < y > A < 2 > O < 6 > F, A is at least one of Zr, Nb, Mo, Ru, Sn, Sb, Hf, Ta, W, Pb, B , Si, Mn and T , x is more than 0 and less than or equal to 2, and y meets valence balance; the ionic conductivity of the solid electrolyte material is greater than 3mS / cm, the reduction potential is less than or equal to 1.2 V, and the oxidation potential is greater than or equal to 5V; the ionic conductivity of the solid electrolyte diaphragm is larger than 6 mS / cm, the reduction potential is smaller than or equal to 1.2 V, the oxidation potential is larger than or equal to 4.5 V, the interface impedance is smaller than or equal to 5 omega.cm < 2 >, and the contact angle of the electrolyte on the solid electrolyte diaphragm is smaller than or equal to 12 degrees.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a solid-state electrolyte separator and a preparation method and application thereof. BACKGROUND

[0002] The current commercialized lithium ion battery has high energy density and good safety performance, but its development still faces many challenges. First, the interface impedance of the intermediate separator layer and the positive and negative electrode layer is large, which leads to large overall internal resistance of the battery and slow charging speed. Second, the existing solid-state electrolyte material and solid-state electrolyte coating separator have a narrow electrochemical window and low powder conductivity in the application of high-voltage system and lithium metal negative electrode. In addition, there is a direct relationship between the thickness of the intermediate electrolyte layer or separator layer and the ionic conductivity, so it is also a problem to be solved to improve the ionic conductivity while ensuring safety.

[0003] In order to overcome these problems, researchers have been exploring new solid-state electrolyte materials and structural designs to improve the energy density, safety and rate performance of the battery. However, the ceramic separator commonly used in the market still has problems such as poor ionic conductivity, poor battery cycle performance and poor heat resistance improvement; although the solid-state electrolyte coating separator has certain improvement on ionic conductivity, the poor stability of the positive electrode or negative electrode leads to some side reactions.

[0004] A Chinese patent with the authorization announcement number CN108063208B discloses a high-performance lithium battery porous separator and a preparation method thereof, wherein the preparation method is to coat a porous aluminum oxide coating on a common lithium battery base film. The coating aluminum oxide of the separator is prepared by aluminum-based metal organic framework sintering, has high thermal stability, high thermal conductivity and good safety, and can well play the role of timely heat conduction, solving the problem that the heat conductivity of the separator is poor and heat cannot be timely conducted. However, the aluminum oxide used in this method cannot conduct lithium ions, leading to increased battery impedance and poor rate performance.

[0005] A Chinese patent with the publication number CN114156602A discloses a solid-state electrolyte separator with multiple coatings, a preparation method and application thereof. Compared with the ceramic aluminum oxide separator, the solid-state electrolyte separator has good ion conductivity, can reduce the impedance of the interface between the separator and the electrode sheet and itself, but the solid-state electrolyte material used has the problems of being easily reduced at low voltage and being unstable to lithium metal, which can lead to reduced initial efficiency and energy density of the battery, and poor wettability of the separator.

[0006] Therefore, it is of great significance to develop a new type of solid-state electrolyte material with high ionic conductivity and wide electrochemical window and its coating separator for promoting the practical application of lithium ion batteries. SUMMARY

[0007] The present application aims at providing a solid-state electrolyte separator and a preparation method and application thereof to overcome the defects of the prior art.

[0008] To achieve the above-mentioned purpose, in a first aspect, the present application provides a solid-state electrolyte separator, comprising a base film and a coating layer.

[0009] The coating layer is attached to one side or both sides of the base film or partially penetrates into the pores of the base film; the material composition of the coating layer comprises a solid-state electrolyte material, and the chemical formula of the solid-state electrolyte material is: Li x La y A2O6F, wherein A is at least one of Zr, Nb, Mo, Ru, Sn, Sb, Hf, Ta, W, Pb, Bi, Si, Mn, Ti, and 0 2 x The ion conductivity of the solid-state electrolyte separator is > 6 mS / cm, the reduction potential is ≤ 1.2 V, the oxidation potential is ≥ 4.5 V, and the interface impedance is ≤ 5 Ω·cm y The contact angle of the electrolyte on the solid-state electrolyte separator is ≤ 12°.

[0011] Preferably, the material composition of the coating layer further comprises a binder and a dispersant.

[0012] The binder comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylonitrile, butadiene styrene rubber, polyvinyl alcohol, polyacrylamide, and acrylate-based binder.

[0013] The dispersant comprises one or more of sodium polyacrylate, sodium dodecylbenzenesulfonate, sodium stearate, cetyltrimethylammonium bromide, polyethylene glycol, polyacrylic acid, polymaleic anhydride, and polyvinylpyrrolidone; and the mass ratio of the solid-state electrolyte material, the binder, and the dispersant in the material composition of the coating layer is [90-98]: [0.5-5]: [0.2-5].

[0014] Preferably, the base film is prepared from a polar monomolecular polymer after polymerization; the high molecular polymer includes one or more of polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET); the base film has a pore size of 20-300 nm and a porosity of 40-85%.

[0015] Preferably, the thickness of the coating layer is 0.3-5 μm, and the thickness of the solid-state electrolyte diaphragm is 3-25 μm.

[0016] Further preferably, the thickness of the coating layer is 0.3-3 μm, and the thickness of the solid-state electrolyte diaphragm is 3-20 μm.

[0017] In a second aspect, the present application provides a preparation method of the solid-state electrolyte diaphragm according to any one of the above first aspect, the preparation method comprising:

[0018] sintering the mixture, and then crushing to obtain micron-sized solid-state electrolyte powder;

[0019] sand grinding or ball grinding the micron-sized solid-state electrolyte powder, a solvent, and a dispersant according to a first mass ratio to obtain nanoscale solid-state electrolyte slurry; the first mass ratio is [10-40]:[60-88]:[0.001-0.1]; the nanoscale solid-state electrolyte slurry has a particle size distribution of 10 nm≤Dv50≤800 nm and Dv100≤5 μm;

[0020] stirring and uniformly mixing the nanoscale solid-state electrolyte slurry and a binder according to a second mass ratio in a stirring device to obtain solid-state electrolyte coating slurry; the second mass ratio is [80-99]:[0.5-20];

[0021] coating the solid-state electrolyte coating slurry on the surface of the base film or infiltrating the solid-state electrolyte coating slurry into the pores of the base film, and then drying to obtain the solid-state electrolyte diaphragm.

[0022] Preferably, the first mass ratio is [20-40]:[68-78]:[0.001-0.05], and the nanoscale solid-state electrolyte slurry has a particle size distribution of 10 nm≤Dv50≤700 nm and Dv100≤4 μm.

[0023] Preferably, the second mass ratio is [85-99]:[0.5-10].

[0024] Preferably, the solvent is one or more of deionized water, N-methyl pyrrolidone, alcohol, dimethylformamide, ethyl acetate, isopropyl alcohol;

[0025] The dispersant is one or more of sodium polyacrylate, sodium dodecyl benzene sulfonate, sodium stearate, cetyl trimethyl ammonium bromide, polyethylene glycol, polyacrylic acid, polymaleic anhydride, polyvinylpyrrolidone.

[0026] The binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylonitrile, styrene butadiene rubber, polyvinyl alcohol, polyacrylamide, and acrylate-based binder.

[0027] In a third aspect, the present application provides an application of the solid-state electrolyte separator of any one of the above-mentioned first aspect or the solid-state electrolyte separator prepared by the preparation method of any one of the above-mentioned second aspect, which is applied in a liquid battery, a semi-solid battery, and a full-solid battery.

[0028] The solid-state electrolyte separator provided by the embodiments of the present application has a larger pore size of the base film, a higher ionic conductivity of the coating layer, and material particles of part of the coating layer can penetrate into the pores of the base film, so that the solid-state electrolyte separator has a higher ionic conductivity, and the material of the coating layer contains fluorine ions, which can participate in the formation of a solid electrolyte interphase (SEI) film in the process of charging and discharging of the battery. The SEI film has a good adhesion effect on the solid-state electrolyte separator and the electrode, so that the interface contact is more sufficient, the impedance of the battery is reduced, and the rate performance of the battery is also obviously improved. The fluorine element has similar polarity with the base film, so that the coating layer is more easily infiltrated with the base film, the wettability of the solid-state electrolyte separator is improved, the contact angle of the electrolyte on the solid-state electrolyte separator is very small, and thus the rate performance and the cycle life of the battery are improved.

[0029] In addition, the element A in the material composition of the coating layer is doped, the stability of the material lattice is improved, the material has a wider electrochemical window, the oxidation potential is higher, and the reduction potential is lower, so that the solid-state electrolyte separator has good stability to the positive and negative electrodes. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The preparation method flow chart of the solid-state electrolyte separator provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the present application clearer, the following will further describe the present application in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those ordinarily skilled in the art without creative effort belong to the scope of the present application.

[0032] The technical solutions of the present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] The embodiment of the present application provides a solid electrolyte separator, which comprises a base film and a coating layer.

[0034] The base film serves as a support structure of the solid electrolyte separator. The base film can be prepared from a high molecular polymer obtained after polymerization of a polar monomer. The high molecular polymer specifically comprises one or more of polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). The base film has pores. The pore size of the base film is 20-300 nm, and the porosity is 40-85%.

[0035] The coating layer is attached to one side or both sides of the base film or partially penetrates into the pores of the base film. The thickness of the coating layer is specifically 0.3-5 μm, preferably 0.3-3 μm.

[0036] The material composition of the coating layer mainly comprises a solid electrolyte material. The chemical formula of the solid electrolyte material is: Li x La y A2O6F, wherein A is at least one of Zr, Nb, Mo, Ru, Sn, Sb, Hf, Ta, W, Pb, Bi, Si, Mn, Ti, and 0

[0037] As an optional solution, the material composition of the coating layer further comprises a binder and a dispersant.

[0038] The binder specifically comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylonitrile, styrene-butadiene rubber, polyvinyl alcohol, polyacrylamide, and an acrylate-based binder.

[0039] The dispersant specifically includes one or more of sodium polyacrylate, sodium dodecyl benzene sulfonate, sodium stearate, cetyl trimethyl ammonium bromide, polyethylene glycol, polyacrylic acid, polymaleic anhydride, and polyvinylpyrrolidone.

[0040] The mass ratio of the material composition of the coating layer can be [90-98]: [0.5-5]: [0.2-5] for the solid electrolyte material, the binder, and the dispersant.

[0041] The solid electrolyte separator has an ionic conductivity of > 6 mS / cm, a reduction potential of ≤ 1.2 V, an oxidation potential of ≥ 4.5 V, and an interface impedance of ≤ 5 Ω·cm. 2 The contact angle of the electrolyte on the solid electrolyte separator is ≤ 12°, and the infiltration time is reduced by at least 20%. The thickness of the solid electrolyte separator can be 3 μm-25 μm, preferably 3 μm-20 μm.

[0042] The solid electrolyte separator provided by the embodiment of the present application has a larger pore size of the base film and a higher ionic conductivity of the coating layer. Part of the material particles of the coating layer can penetrate into the pores of the base film, so that the solid electrolyte separator has a higher ionic conductivity. The material of the coating layer contains fluorine ions, which can participate in the formation of a solid electrolyte interphase (SEI) film during the charging and discharging of the battery. The SEI film has a good adhesion effect on the solid electrolyte separator and the electrode, so that the interface contact is more sufficient, the impedance of the battery is reduced, and the rate performance of the battery is also obviously improved. The fluorine element has similar polarity with the base film, so that the coating layer is more easily infiltrated with the base film, the wettability of the solid electrolyte separator is improved, the contact angle of the electrolyte on the solid electrolyte separator is very small, and thus the rate performance and cycle life of the battery are improved.

[0043] In addition, the material composition of the coating layer is doped with elements at site A, which improves the stability of the material lattice, so that the material has a wider electrochemical window, a higher oxidation potential, and a lower reduction potential. Therefore, the solid electrolyte separator has good stability to the positive and negative electrodes.

[0044] The above-mentioned solid electrolyte separator of the present application can be prepared by the following method, and the steps of the preparation method are specifically shown as follows: Figure 1

[0045] In step 110, the raw materials are mixed and sintered, and then micron-sized solid electrolyte powder is obtained by crushing.

[0046] First, the raw materials are first ball-mixed according to the molar ratio of each element in the chemical formula of the solid electrolyte material in the pre-prepared solid electrolyte separator.

[0047] ​The chemical formula of the solid electrolyte material is: Li x La y A2O6F, wherein A is at least one of Zr, Nb, Mo, Ru, Sn, Sb, Hf, Ta, W, Pb, Bi, Si, Mn, Ti, and 0 < x < 2, y satisfies the valence balance; the raw materials include: the lithium source can include one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate. The lanthanum source can include one or more of lanthanum hydroxide, lanthanum trioxide, and lanthanum acetate. The A source can include at least one of niobium pentoxide, tantalum pentoxide, zirconium oxide, zirconium hydroxide, and silicon dioxide.

[0048] The rotation speed of the first ball milling mixing is 400 rpm-800 rpm, and the time is 3 hours-10 hours. The first ball milling mixing can be performed in a dry method or a wet method. The dry method is to ball mill the powder, and the wet method is to add a solvent, such as deionized water, ethanol, N-methyl pyrrolidone (NMP), methanol, cyclohexane, tetrahydrofuran, acetone, etc., during the ball milling mixing. After the wet method grinding is completed, drying is required. The present application preferably performs ball milling in a dry method.

[0049] Secondly, the first ball milling product is subjected to first sintering to obtain a first material.

[0050] The temperature of the first sintering is 900℃-1300℃, preferably 1100℃-1200℃, and the time is 4 hours-16 hours, preferably 6 hours-10 hours. This step is mainly to perform pre-sintering to make the material initially phase. The sintering can obtain a material with higher purity.

[0051] Then, the first material is subjected to second ball milling mixing with lithium fluoride.

[0052] The rotation speed of the second ball milling mixing is 400 rpm-800 rpm, and the time is 3 hours-10 hours.

[0053] After that, the product of the second ball milling mixing is subjected to second sintering in an inert atmosphere to obtain a second material.

[0054] The inert atmosphere includes nitrogen and / or argon. The temperature of the second sintering is 800℃-1150℃, preferably 900℃-1000℃, and the time is 2 hours-12 hours, preferably 2 hours-4 hours.

[0055] Finally, the second material is crushed to obtain micron-sized solid electrolyte powder.

[0056] The crushing can be performed in a crusher. The crushing gas pressure is 0.6 MPa-5.2 MPa.

[0057] Step 120, mill or ball mill micron-sized solid electrolyte powder, solvent and dispersant in a first mass ratio to obtain nanoscale solid electrolyte slurry;

[0058] Specifically, the solvent can be one or more of deionized water, N-methyl pyrrolidone (NMP), alcohol, dimethylformamide, ethyl acetate, and isopropyl alcohol. The mass fraction of alcohol is not less than 80%.

[0059] The dispersant can be one or more of sodium polyacrylate, sodium dodecylbenzenesulfonate, sodium stearate, cetyltrimethylammonium bromide, polyethylene glycol, polyacrylic acid, polymaleic anhydride, and polyvinylpyrrolidone.

[0060] The first mass ratio is [10-40]:[60-88]:[0.001-0.1], preferably [20-40]:[68-78]:[0.001-0.05].

[0061] The particle size distribution of the nanoscale solid electrolyte slurry is 10nm≤Dv50≤800nm, Dv100≤5μm, preferably 10nm≤Dv50≤700nm, Dv100≤4μm.

[0062] The sand milling can be achieved in a sand mill, and the sand milling speed can be 1000rpm-2500rpm, and the time can be 1-10 hours.

[0063] Step 130, mix the nanoscale solid electrolyte slurry and the binder in a second mass ratio in a stirring device to obtain a solid electrolyte coating slurry.

[0064] Specifically, the binder can be one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylonitrile, styrene butadiene rubber, polyvinyl alcohol, polyacrylamide, and acrylate binder.

[0065] The second mass ratio is [80-99]:[0.5-20], preferably [85-99]:[0.5-10].

[0066] Step 140, coat the solid electrolyte coating slurry on the surface of the base film or penetrate it into the pores of the base film, and then dry to obtain a solid electrolyte separator.

[0067] Specifically, the coating method can be transfer coating, dip coating or blade coating. The drying can be performed in a tunnel air oven of the coating device, and the temperature can be 40℃-80℃, and the time can be 1min-10min.

[0068] The preparation method of the solid electrolyte membrane provided by the embodiment of the present invention adopts a solid electrolyte with high ionic conductivity as the coating material, so that the ionic conductivity of the solid electrolyte membrane is equivalent to that of the liquid electrolyte, and the water-oxygen stability is good. The fluoride ions in the solid electrolyte can participate in the formation of the solid electrolyte interphase (SEI membrane) during the charge and discharge process of the battery cell. The SEI membrane has a good bonding effect on the solid electrolyte membrane and the electrode, making the interface contact more complete, and solving the problem of high membrane impedance in the prior art; by doping elements in the coating material, the electrochemical window is widened, the ionic conductivity is improved, and the stability of the solid electrolyte membrane to lithium metal is improved; the fluorine element has a similar polarity to the base film and can improve the wettability of the membrane.

[0069] The solid electrolyte membrane provided by the embodiment of the present invention can be applied to liquid batteries, semi-solid batteries and all-solid batteries.

[0070] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to illustrate the specific process of preparing a solid electrolyte membrane using the method provided by the above embodiment of the present invention, as well as the electrochemical properties of the prepared solid electrolyte membrane.

[0071] Example 1

[0072] In the first step, lithium carbonate, lanthanum hydroxide, and tantalum pentoxide are dry-milled at a molar ratio of 0.25:0.5:1 for 6 hours at a ball mill speed of 500 rpm, and then sintered at a temperature of 1100°C for 10 hours to obtain the first material; the first material is mixed with lithium fluoride by ball milling for 8 hours at a ball mill speed of 500 rpm, and sintered at 920°C for 2 hours under a nitrogen atmosphere to obtain the second material; the second material is crushed by a pulverizer to obtain micron-sized solid electrolyte powder. The chemical formula of the micron-sized solid electrolyte powder is Li 1.5 La 0.5 Ta2O6F, the crushing pressure is 1.8MPa.

[0073] In the second step, the micron-sized solid electrolyte powder, NMP, and polyethylene glycol were ground in a sand mill at a mass ratio of 19.95:80:0.05 for 3 hours at 1800 rpm to produce a nanoscale solid electrolyte slurry. The particle size distribution of the nanoscale solid electrolyte slurry was: Dv50 = 500 nm, Dv100 = 960 nm.

[0074] In the third step, the nano-scale solid electrolyte slurry and polyvinylidene fluoride are mixed uniformly in a mass ratio of 96:4 on a planetary mixer at a speed of 1800 r / min for 1 hour to obtain a solid electrolyte coating slurry.

[0075] The fourth step is to coat the solid electrolyte coating slurry to both sides of the base film by transfer coating, and dry at 60°C for 5 min to obtain a solid electrolyte separator. The base film is realized by PE material, the thickness is 9 μm, the coating thickness of each side is 1 μm, and the thickness of the solid electrolyte separator is 11 μm.

[0076] Example 2

[0077] The first step is to take lithium carbonate, lanthanum hydroxide, and zirconium oxide by dry ball milling at a molar ratio of 0.3:1.13:2 for 6 hours, and then sintering at a temperature of 1200°C for 10 hours. The rotation speed of ball milling is 400 rpm. Then, the first material is mixed with lithium fluoride by ball milling for 8 hours, and the rotation speed of ball milling is 400 rpm. Under the nitrogen atmosphere, the second material is sintered at 1000°C for 2 hours. The micron-level solid electrolyte powder is obtained by crushing the second material with a pulverizer. The chemical formula of the micron-level solid electrolyte powder is Li 1.6 La 1.13 Zr2O6F, and the crushing gas pressure is 3 MPa.

[0078] The second step is to grind the micron-level solid electrolyte powder, deionized water, and polymaleic anhydride in a sand mill at a rotation speed of 2000 rpm for 2 hours, and the mass ratio is 29.95:70:0.05, to obtain a nano-level solid electrolyte slurry. The particle size distribution of the nano-level solid electrolyte slurry is: Dv50=450 nm, Dv100=820 nm.

[0079] The third step is to mix the nano-level solid electrolyte slurry and polyvinylidene fluoride uniformly by stirring in a planetary mixer at a rotation speed of 1800 r / min for 0.5 hours, and the mass ratio is 96:4, to obtain a solid electrolyte coating slurry.

[0080] The fourth step is to coat the solid electrolyte coating slurry to both sides of the base film by transfer coating, and dry at 40°C for 10 min to obtain a solid electrolyte separator. The base film is realized by PE material, the thickness is 9 μm, the coating thickness of each side is 1 μm, and the thickness of the solid electrolyte separator is 11 μm.

[0081] Example 3

[0082] The first step is to take lithium hydroxide, lanthanum trioxide, and niobium pentoxide by dry ball milling at a molar ratio of 0.2:0.3:1 for 6 hours, and the ball milling speed is 800 rpm. Then, the first material is obtained by sintering at a temperature of 1100°C for 6 hours. The first material is mixed with lithium fluoride by ball milling for 8 hours, and the ball milling speed is 800 rpm. The second material is obtained by sintering at a temperature of 1000°C for 4 hours under an argon atmosphere. The micron-sized solid electrolyte powder is obtained by crushing the second material with a crusher. The chemical formula of the micron-sized solid electrolyte powder is Li 1.2 La 0.6 Nb2O6F, and the crushing gas pressure is 4 MPa.

[0083] The second step is to grind the micron-sized solid electrolyte powder, deionized water, and polyethylene glycol in a sand mill at a speed of 1500 rpm for 6 hours at a mass ratio of 29.95:70:0.05 to obtain a nanoscale solid electrolyte slurry. The particle size distribution of the nanoscale solid electrolyte slurry is Dv50=450 nm and Dv100=820 nm.

[0084] The third step is to mix the nanoscale solid electrolyte slurry and polyvinylidene fluoride uniformly in a planetary mixer at a speed of 1800 r / min for 0.5 hours at a mass ratio of 96:4 to obtain a solid electrolyte coating slurry.

[0085] The fourth step is to coat the solid electrolyte coating slurry onto one side of the base film using a transfer coating method, and then dry it at 70°C for 3 minutes to obtain a solid electrolyte separator. The base film is made of PP material with a thickness of 12 μm, and the coating thickness is 1 μm. The thickness of the solid electrolyte separator is 13 μm.

[0086] Example 4

[0087] The first step is to take lithium hydroxide, lanthanum trioxide, niobium pentoxide, and silicon dioxide by dry ball milling at a molar ratio of 0.2:0.335:0.9:0.2 for 6 hours, and the ball milling speed is 600 rpm. Then, the first material is obtained by sintering at a temperature of 1100°C for 6 hours. The first material is mixed with lithium fluoride by ball milling for 8 hours, and the ball milling speed is 600 rpm. The second material is obtained by sintering at a temperature of 1000°C for 4 hours under an argon atmosphere. The micron-sized solid electrolyte powder is obtained by crushing the second material with a crusher. The chemical formula of the micron-sized solid electrolyte powder is Li 1.2 La 0.67 Nb 1.8 Si 0.2 O6F, and the crushing gas pressure is 0.6 MPa.

[0088] Second step, micron solid electrolyte powder, deionized water, polyethylene glycol according to the mass ratio of 29.95:70:0.05, in the sand mill at the speed of 2500 rpm, grinding 1 hour, get nanoscale solid electrolyte slurry. Among them, the particle size distribution of nanoscale solid electrolyte slurry is: Dv50=450nm, Dv100=820nm.

[0089] Third step, nanoscale solid electrolyte slurry, carboxymethyl cellulose sodium according to the mass ratio of 96:4 in the planetary mixer at the speed of 1800r / min stirring 0.5 hours, get solid electrolyte coating slurry.

[0090] Fourth step, solid electrolyte coating slurry is coated to one side of the base film by transfer coating, and dried at 80℃ for 1min, get solid electrolyte separator. Among them, the base film is realized by PP material, the thickness is 12μm, the coating thickness is 1μm, the thickness of the solid electrolyte separator is 13μm.

[0091] Example 5

[0092] First step, according to the molar ratio of 0.5:0.33:0.75:0.5, lithium hydroxide, lanthanum trioxide, tantalum pentoxide, zirconium hydroxide are mixed by dry ball milling for 6 hours, the ball milling speed is 700 rpm, then sintered at 1100℃ for 6 hours, get the first material; the first material and lithium fluoride are ball milled for 8 hours, the ball milling speed is 700 rpm, sintered at 1000℃ for 4 hours under argon atmosphere, get the second material; the second material is crushed by a crusher to get micron solid electrolyte powder. Among them, the chemical formula of micron solid electrolyte powder is Li 1.5 La 0.67 Ta 1.5 Zr 0.5 O6F, the crushing pressure is 5.2MPa.

[0093] Second step, micron solid electrolyte powder, deionized water, polyethylene glycol according to the mass ratio of 29.95:70:0.05, in the sand mill at the speed of 2500 rpm, grinding 1 hour, get nanoscale solid electrolyte slurry. Among them, the particle size distribution of nanoscale solid electrolyte slurry is: Dv50=450nm, Dv100=820nm.

[0094] Third step, nanoscale solid electrolyte slurry, carboxymethyl cellulose sodium according to the mass ratio of 96:4 in the planetary mixer at the speed of 1800r / min stirring 0.5 hours, get solid electrolyte coating slurry.

[0095] Fourthly, the solid electrolyte coating slurry was coated on one side of the base film by transfer coating, and dried at 50°C for 6 min to obtain a solid electrolyte separator. The base film was made of PP material, with a thickness of 12 μm, a coating thickness of 1 μm, and a thickness of the solid electrolyte separator of 13 μm.

[0096] Comparative Example 1

[0097] Firstly, micron-sized solid electrolyte powder (aluminum oxide), NMP, and polyethylene glycol were ground in a sand mill at a rotational speed of 1800 rpm for 3 hours at a mass ratio of 19.95:80:0.05 to obtain a nanoscale solid electrolyte slurry. The particle size distribution of the nanoscale solid electrolyte slurry was Dv50=500 nm and Dv100=960 nm.

[0098] Secondly, the nanoscale solid electrolyte slurry and polyvinylidene fluoride were mixed uniformly on a planetary mixer at a rotational speed of 1800 r / min for 1 hour at a mass ratio of 96:4 to obtain a solid electrolyte coating slurry.

[0099] Thirdly, the solid electrolyte coating slurry was coated on both sides of the base film by transfer coating, and dried at 60°C for 5 min to obtain a solid electrolyte separator. The base film was made of PE material, with a thickness of 9 μm, a coating thickness of 1 μm on each side, and a thickness of the solid electrolyte separator of 11 μm.

[0100] Comparative Example 2

[0101] Firstly, micron-sized solid electrolyte powder (LATP), deionized water, and polyethylene glycol were ground in a sand mill at a rotational speed of 1500 rpm for 6 hours at a mass ratio of 29.95:70:0.05 to obtain a nanoscale solid electrolyte slurry. The particle size distribution of the nanoscale solid electrolyte slurry was Dv50=450 nm and Dv100=820 nm.

[0102] Thirdly, the nanoscale solid electrolyte slurry and polyvinylidene fluoride were mixed uniformly on a planetary mixer at a rotational speed of 1800 r / min for 0.5 hours at a mass ratio of 96:4 to obtain a solid electrolyte coating slurry.

[0103] Fourthly, the solid electrolyte coating slurry was coated on one side of the base film by transfer coating, and dried at 70°C for 3 min to obtain a solid electrolyte separator. The base film was made of PP material, with a thickness of 12 μm, a coating thickness of 1 μm, and a thickness of the solid electrolyte separator of 13 μm.

[0104] The test methods for the various parameters involved in the solid electrolyte separators prepared in the above Examples 1-5 and Comparative Examples 1-2 are as follows:

[0105] Test method 1: The test of ion conductivity, the test of reduction potential, the test of oxidation potential and the test of interface impedance can be carried out according to the test scheme recorded in national standard GB / T 36363-2018 “Polyolefin separator for lithium battery”, which will not be described in detail.

[0106] Test method 2: The test of contact angle can be carried out according to the test scheme recorded in national standard GB / T 30693-2014 “Measurement of contact angle of plastics film with water”, which will not be described in detail.

[0107] Test method 3: The particle size Dv50 of the material refers to the volume median particle size of the material, which is the median value according to the volume sorting. In each embodiment of the present application, the median particle size according to the volume sorting is specifically used, which represents the particle size of the nano-scale solid-state electrolyte slurry distributed at 50% according to the volume distribution. The particle size Dv100 refers to the volume maximum particle size of the material, which is the maximum value according to the volume sorting. In each embodiment of the present application, the maximum particle size according to the volume sorting is specifically used, which represents the particle size of the nano-scale solid-state electrolyte slurry with a cumulative value of 100% according to the volume distribution. The particle sizes Dv50 and Dv100 are meanings known in the art. The particle sizes Dv50 and Dv100 of the material provided in the embodiments of the present application can be determined by instruments known in the art and conventional methods. Specifically, in each embodiment of the present application, the particle sizes Dv50 and Dv100 are determined by a Mastersizer 3000 laser particle size analyzer of Malvern Instruments Ltd., UK.

[0108] Test method 4: The pore size in the present application refers to the diameter of the internal pores in the base film, which is a meaning known in the art. The pore size can be determined by instruments known in the art and conventional methods. In this example, the pore size of the base film can be directly measured by a scanning electron microscope (SEM). The porosity can be tested by the specific gravity method known in the art, and then calculated by the ratio of the true density to the apparent density of the solid-state electrolyte separator.

[0109] Test method 5: The thickness can be obtained by the micrometer test known in the art.

[0110] The test results of each parameter are recorded in Table 1 as follows.

[0111] Ionic conductivity Reduction potential Oxidation potential Interfacial impedance Contact angle Example 1 8.6 1.0V 5.3V 3.0 8 Example 2 8.2 1.1V 5.1V 3.2 8 Example 3 7.2 0.8V 5.0V 4.1 9 Example 4 6.5 0.8V 4.9V 4.4 7 Example 5 6.6 0.75V 4.9V 4.6 9 Comparative Example 1 3.4 1.1V 4.0V 9.6 14 Comparative Example 2 5.1 1.6V 4.2V 6.8 15

[0112] Table 1

[0113] As shown in Table 1, the ion conductivities of the solid electrolyte separators of Examples 1-5 are higher than those of Comparative Examples 1-2, and the interface impedances are lower than those of Comparative Examples 1-2. This is because the coating layer of the solid electrolyte separator of Examples 1-5 has a material composition with high ion conductivity, and the base film has a large pore size, so that the material of the coating layer can penetrate into the pores of the base film, thus making the solid electrolyte separator have high ion conductivity. In addition, the material composition of the coating layer contains fluoride ions, which can participate in the formation of the SEI film during charging and discharging, and form a good adhesive effect between the solid electrolyte separator and the electrode, thereby reducing the interface impedance.

[0114] The solid electrolyte separators of Examples 1-5 have lower reduction potentials and higher oxidation potentials than Comparative Examples 1-2. This is because the specific elements are doped to make the structure more stable, and can not be reduced at a lower potential and can not be oxidized at a higher potential. In addition, the material contains a strong polar fluoride ion, and the material of the base film is also a polar molecule, so that the solid electrolyte separator prepared by stacking the two has good wettability to the electrolyte, so that the contact angle of the electrolyte on the solid electrolyte separator of Examples 1-5 is very small, and is smaller than that of Comparative Examples 1-2.

[0115] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only a specific embodiment of the present application, and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A solid electrolyte membrane, characterized in that The solid electrolyte membrane comprises: a base membrane and a coating; The coating is attached to one side or both sides of the base membrane or partially penetrates into the pores of the base membrane; the material composition of the coating includes a solid electrolyte material, and the chemical formula of the solid electrolyte material is: Li x La y A2O6F, wherein A is at least one of Zr, Nb, Mo, Ru, Sn, Sb, Hf, Ta, W, Pb, Bi, Si, Mn, and Ti, and 0 < x ≤ 2, and y satisfies valence balance; the solid electrolyte material has an ionic conductivity greater than 3 mS / cm, a reduction potential ≤ 1.2 V, and an oxidation potential ≥ 5 V; The solid electrolyte membrane has an ionic conductivity of >6 mS / cm, a reduction potential of ≤1.2 V, an oxidation potential of ≥4.5 V, and an interface impedance of ≤5 Ω·cm. 2 , the contact angle of the electrolyte on the solid electrolyte membrane is ≤12°.

2. The solid electrolyte membrane according to claim 1, characterized in that The material composition of the coating also includes a binder and a dispersant; The binder includes: one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylonitrile, styrene-butadiene rubber, polyvinyl alcohol, polyacrylamide, and acrylic ester binders; The dispersant includes one or more of sodium polyacrylate, sodium dodecylbenzenesulfonate, sodium stearate, cetyltrimethylammonium bromide, polyethylene glycol, polyacrylic acid, polymaleic anhydride, and polyvinyl pyrrolidone; in the material composition of the coating, the mass ratio of the solid electrolyte material, the binder, and the dispersant is: [90-98]: [0.5-5]: [0.2-5].

3. The solid electrolyte membrane according to claim 1, characterized in that The base membrane is prepared from a high molecular polymer obtained after polar monomolecular polymerization; the high molecular polymer includes one or more of polypropylene PP, polyethylene PE, polyvinylidene fluoride PVDF, polyethylene oxide PEO, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, polyvinyl alcohol PVA, polymethyl methacrylate PMMA, and polyethylene terephthalate PET; the pore size of the base membrane is 20nm-300nm, and the porosity is 40%-85%.

4. The solid electrolyte membrane according to claim 1, characterized in that The coating layer has a thickness of 0.3 μm to 5 μm, and the solid electrolyte membrane has a thickness of 3 μm to 25 μm.

5. The solid electrolyte membrane according to claim 4, characterized in that The coating layer has a thickness of 0.3 μm to 3 μm, and the solid electrolyte membrane has a thickness of 3 μm to 20 μm.

6. A method for preparing a solid electrolyte membrane according to any one of claims 1 to 5, characterized in that: The preparation method comprises: The raw materials are mixed, sintered, and then crushed to obtain micron-sized solid electrolyte powder; Sand-milling or ball-milling the micron-sized solid electrolyte powder, solvent, and dispersant according to a first mass ratio into a nano-sized solid electrolyte slurry; wherein the first mass ratio is: [10-40]: [60-88]: [0.001-0.1]; and the particle size distribution of the nano-sized solid electrolyte slurry is: 10 nm ≤ Dv50 ≤ 800 nm, Dv100 ≤ 5 μm; The nano-scale solid electrolyte slurry and the binder are stirred and mixed uniformly in a stirring device according to a second mass ratio to obtain a solid electrolyte coating slurry; wherein the second mass ratio is: [80-99]: [0.5-20]; The solid electrolyte coating slurry is coated on the surface of the base membrane or penetrated into the pores of the base membrane, and then dried to obtain a solid electrolyte separator.

7. The preparation method according to claim 6, characterized in that The first mass ratio is: [20-40]: [68-78]: [0.001-0.05], and the particle size distribution of the nano-scale solid electrolyte slurry is: 10nm≤Dv50≤700nm, Dv100≤4μm.

8. The preparation method according to claim 6, characterized in that The second mass ratio is [85-99]:[0.5-10].

9. The preparation method according to claim 6, characterized in that The solvent is one or more of deionized water, N-methylpyrrolidone, alcohol, dimethylformamide, ethyl acetate, and isopropyl alcohol; The dispersant is one or more of sodium polyacrylate, sodium dodecylbenzenesulfonate, sodium stearate, cetyltrimethylammonium bromide, polyethylene glycol, polyacrylic acid, polymaleic anhydride, and polyvinyl pyrrolidone; The binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylonitrile, styrene-butadiene rubber, polyvinyl alcohol, polyacrylamide, and acrylic ester binders.

10. Use of the solid electrolyte membrane according to any one of claims 1 to 5 or the solid electrolyte membrane prepared by the preparation method according to any one of claims 6 to 9, characterized in that: The solid electrolyte membrane is used in liquid batteries, semi-solid batteries and all-solid batteries.

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