Solid electrolyte membrane, preparation method, use thereof, and solid-state battery

Abstract

The present invention relates to the field of battery material technology, and specifically to a solid electrolyte membrane, a preparation method thereof, a use thereof, and a solid-state battery. The solid electrolyte membrane comprises a lithium metal stabilization layer, a lithium dendrite suppression layer, and a high conductivity layer, which are stacked in sequence; wherein the lithium metal stabilization layer contains a first sulfide solid electrolyte, the surface of which is coated with a lithium sulfide protective layer; the lithium dendrite suppression layer contains a second sulfide solid electrolyte, the porosity of which is less than 8%; and the high conductivity layer contains a third sulfide solid electrolyte, the Hinkley crystallinity index of which is greater than 1.1 and the particle size is greater than 20 μm. The present invention uses a single-component sulfide as an electrolyte without introducing a third component, significantly improving the stability of the sulfide solid electrolyte membrane to the lithium metal negative electrode, improving the ability of the electrolyte membrane to suppress lithium dendrites, and maintaining the high conductivity of the sulfide itself.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a solid electrolyte membrane, a preparation method thereof, uses thereof, and a solid-state battery. Background Art

[0002] Compared to liquid batteries, solid-state batteries offer significantly improved safety due to their use of non-flammable solid electrolytes instead of flammable organic liquid electrolytes. Furthermore, solid-state batteries are better suited to high-energy positive and negative electrodes, reduce system weight, and possess higher energy density. Consequently, solid-state batteries have garnered widespread attention within the industry.

[0003] Among various solid-state electrolyte systems, sulfide solid electrolytes have broad application prospects due to their advantages such as high processability and high ionic conductivity. When used as the negative electrode of solid-state batteries, lithium metal has the advantages of high specific capacity, abundant resources, low density, and low cost. However, sulfide solid electrolytes are unstable to lithium metal, and the electrolyte membrane prepared from sulfide solid electrolyte particles has interparticle gaps. Lithium dendrites can easily penetrate these gaps and cause battery short circuits. Therefore, the compatibility of sulfide solid electrolytes with lithium metal negative electrodes is extremely low.

[0004] At present, in order to improve the compatibility of sulfide solid electrolytes and lithium metal negative electrodes, the commonly used method is to introduce a third component into the sulfide solid electrolyte and the lithium metal negative electrode, for example: ① Use polymer electrolytes to isolate the lithium metal negative electrode and the sulfide solid electrolyte to avoid direct contact between the lithium metal negative electrode and the sulfide solid electrolyte, thereby inhibiting the reaction between the lithium metal negative electrode and the sulfide solid electrolyte, and the relatively dense polymer electrolyte layer can also play a role in inhibiting the growth of lithium dendrites; ② Use inorganic substances to modify the surface of the lithium metal negative electrode.

[0005] However, when the compatibility of sulfide solid electrolyte and lithium metal negative electrode is improved by introducing a third component, the following problems will exist to varying degrees: ① The conductivity of the third component is usually low, which leads to a decrease in the overall conductivity of the system; ② After the introduction of the third component, due to the difference in material strength and mechanical properties, the interface contact between the third component and the sulfide solid electrolyte membrane is poor; ③ The stability between the third component and the sulfide solid electrolyte is difficult to ensure. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art of improving the compatibility of the sulfide solid electrolyte with the lithium metal negative electrode by introducing a third component, namely, the third component has low electrical conductivity, poor interfacial contact between the third component and the sulfide solid electrolyte membrane, and the stability between the third component and the sulfide solid electrolyte is difficult to ensure, thereby providing a solid electrolyte membrane, a preparation method thereof, a use thereof, and a solid-state battery.

[0007] When sulfide solid electrolytes are used to prepare lithium metal negative electrode solid-state batteries, the potential of the contact surface between the sulfide solid electrolyte and the lithium metal is 0V. The high-valent elements in the sulfide solid electrolyte will be reduced at this potential, causing the structure of the electrolyte itself to collapse, thereby forming a mixed product with ionic and electronic conductivity functions, which will cause the ionic conductivity of the electrolyte to be significantly reduced, and the macroscopic manifestation is increased battery polarization and a significant decrease in charge and discharge capacity; in addition, the sulfide solid electrolyte membrane is composed of sulfide solid electrolyte particles, and there are gaps between the particles. Lithium dendrites can easily grow in the gaps. When the lithium dendrites grow to penetrate the entire electrolyte membrane, it will cause a short circuit between the positive and negative electrodes, and then cause an internal short circuit in the battery, which is manifested macroscopically as a sudden drop in battery voltage and loss of charge and discharge capacity.

[0008] In order to solve the above problems, the present invention provides a solid electrolyte membrane, comprising a lithium metal stabilization layer, a lithium dendrite suppression layer and a high conductivity layer stacked in sequence; wherein,

[0009] The lithium metal stabilization layer contains a first sulfide solid electrolyte, and the surface of the first sulfide solid electrolyte is coated with a lithium sulfide protective layer;

[0010] The lithium dendrite suppression layer contains a second sulfide solid electrolyte, and the porosity of the lithium dendrite suppression layer is less than 8%;

[0011] The high conductivity layer contains a third sulfide solid electrolyte, the third sulfide solid electrolyte has a Hinckley crystallinity index greater than 1.1, and a particle size greater than 20 μm.

[0012] Optionally, the molar ratio of the first sulfide solid electrolyte to lithium sulfide is 1:(0.01-0.05);

[0013] Optionally, the particle size of the first sulfide solid electrolyte is less than 5 μm;

[0014] Optionally, the lithium metal stabilization layer further contains a first binder, and the weight of the first binder is 1% to 5% of the weight of the first sulfide solid electrolyte;

[0015] Optionally, the first binder does not contain a fluorinated group;

[0016] Optionally, the first binder includes at least one of styrene-butadiene rubber, nitrile-butadiene rubber, polyethylene and polypropylene.

[0017] Optionally, the second sulfide solid electrolyte has a Hinckley crystallinity index of 0.8 to 1 and a particle size of less than 0.5 μm;

[0018] Optionally, the lithium dendrite suppression layer further contains a second binder, and the weight of the second binder is 2% to 6% of the weight of the second sulfide solid electrolyte;

[0019] Optionally, the second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyisoprene, nitrile rubber and styrene-butadiene rubber.

[0020] Optionally, the electrical conductivity of the third sulfide solid electrolyte is greater than 7 mS / cm;

[0021] Optionally, the high conductivity layer further contains a third binder, and the weight of the third binder is 0.5 to 1.5% of the weight of the third sulfide solid electrolyte;

[0022] Optionally, the third binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polybutylene and polyethylene oxide.

[0023] Optionally, the thicknesses of the lithium metal stabilization layer, the lithium dendrite suppression layer and the high conductivity layer may vary within a certain range. For example, the thickness of the lithium metal stabilization layer may be 10 to 20 μm, the thickness of the lithium dendrite suppression layer may be 10 to 20 μm, and the thickness of the high conductivity layer may be 10 to 20 μm.

[0024] Optionally, the first sulfide solid electrolyte, the second sulfide solid electrolyte and the third sulfide solid electrolyte can be selected within a certain range. For example, the chemical formula of the first sulfide solid electrolyte, the second sulfide solid electrolyte and the third sulfide solid electrolyte can be Li 3.15 P 0.5 S 2.5 Cl 0.65 .

[0025] The present invention also provides a method for preparing the above-mentioned solid electrolyte membrane, comprising the following steps:

[0026] contacting the first sulfide solid electrolyte with lithium powder and reacting them, and forming a film of the obtained product by a dry process to obtain a lithium metal stabilization layer;

[0027] The second sulfide solid electrolyte is prepared into an electrolyte slurry having a solid content greater than 70%, coated on a support, and dried to obtain a lithium dendrite suppression layer adhered to the support;

[0028] forming a third sulfide solid electrolyte by a dry process to obtain a high conductivity layer, wherein the third sulfide solid electrolyte has a Hinckley crystallinity index greater than 1.1 and a particle size greater than 20 μm;

[0029] The lithium metal stabilization layer, the lithium dendrite suppression layer and the high conductivity layer are pressed together to obtain the solid electrolyte membrane.

[0030] Optionally, the preparation process of the first sulfide solid electrolyte includes:

[0031] The raw materials for forming the sulfide solid electrolyte are sintered at 400-500° C. for 10-15 hours, and the obtained sintered material is ground to a particle size of less than 5 μm to obtain the first sulfide solid electrolyte.

[0032] Optionally, the step of contacting and reacting the first sulfide solid electrolyte with lithium powder, and forming a film of the resulting product by a dry process to obtain a lithium metal stabilization layer comprises:

[0033] The first sulfide solid electrolyte and the lithium powder are mixed in a molar ratio of 1: (0.01-0.05), and ball milled at a speed of 150-200 rpm for 4-8 hours to obtain a first sulfide solid electrolyte having a lithium sulfide protective layer coated on the surface;

[0034] The first sulfide solid electrolyte with a lithium sulfide protective layer on its surface is mixed with a first binder and subjected to a fiberization treatment. The obtained powder is pressed into a film to obtain the lithium metal stabilization layer.

[0035] During the preparation of the lithium metal stabilization layer, after the first sulfide solid electrolyte is mixed with lithium powder, the soft lithium powder can be evenly coated on the surface of the sulfide solid electrolyte. The surface of the sulfide solid electrolyte in contact with the lithium powder will undergo a uniform reduction reaction, forming a lithium sulfide protective layer. By using ball milling and controlling the contact amount between the sulfide solid electrolyte and the lithium metal, the lithium metal can be uniformly contacted with the sulfide solid electrolyte, thereby controllably and evenly coating the surface of the sulfide solid electrolyte with the lithium sulfide protective layer, thereby preventing further deterioration of the interface between the sulfide solid electrolyte and the lithium metal.

[0036] In addition, the film-forming process adopts a dry film-forming process, which can prevent the protected sulfide solid electrolyte from contacting with organic solvents and causing a decrease in electrolyte stability; the use of a first binder that does not contain fluorinated groups can avoid deterioration and failure of the binder caused by direct contact with lithium metal; and the fiberization treatment can effectively improve the adhesion of the first binder.

[0037] Optionally, the preparation process of the second sulfide solid electrolyte includes:

[0038] The raw materials for forming the sulfide solid electrolyte are sintered at 260-350° C. for 5-8 hours, and the obtained sintered material is ground to a particle size of less than 5 μm to obtain the second sulfide solid electrolyte.

[0039] Optionally, the second sulfide solid electrolyte is prepared into an electrolyte slurry having a solid content greater than 70%, coated on a carrier, and dried to obtain a lithium dendrite suppression layer, comprising:

[0040] mixing the second sulfide solid electrolyte with a solvent, and wet-grinding the mixture until the particle size of the second sulfide solid electrolyte is less than 0.5 μm to obtain a second sulfide solid electrolyte dispersion;

[0041] dispersing a second binder in the second sulfide solid electrolyte dispersion to prepare an electrolyte slurry having a solid content greater than 70%;

[0042] The electrolyte slurry is coated on the carrier and dried to obtain the lithium dendrite suppression layer adhered to the carrier.

[0043] During the preparation of the second sulfide solid electrolyte, a low-temperature, short-time sintering process is adopted. On the one hand, it can avoid the growth of crystal particles, and on the other hand, it can reduce the crystallinity of the second sulfide solid electrolyte, making the particle powder of the second sulfide solid electrolyte softer, which is conducive to the formation of a densified lithium dendrite inhibition layer and increasing the flatness of the lithium dendrite inhibition layer.

[0044] During the preparation of the dendrite suppression layer, the second sulfide solid electrolyte is first wet-grinded, effectively reducing the particle size of the electrolyte powder while maintaining its uniformity, thereby significantly reducing the gaps between particles in the dendrite suppression layer. Controlling the solid content of the electrolyte slurry to greater than 70% significantly improves the density of the resulting dendrite suppression layer. Optionally, the carrier can be a release film, which can improve the flatness of the dendrite suppression layer.

[0045] Optionally, the preparation process of the third sulfide solid electrolyte includes:

[0046] The raw materials for forming the sulfide solid electrolyte are sintered at 550-630° C. for 15-20 hours, and the obtained sintered material is ground to a particle size greater than 20 μm to obtain the third sulfide solid electrolyte.

[0047] Optionally, the step of forming a film of the third sulfide solid electrolyte by a dry process to obtain a high conductivity layer comprises:

[0048] performing a fiberization treatment on the third binder to obtain a fiberized third binder;

[0049] The fiberized third binder is mixed with the third sulfide solid electrolyte, and the obtained powder is pressed into a film to obtain the high conductivity layer.

[0050] In the process of preparing the third sulfide solid electrolyte, a high-temperature, long-term sintering process is used, which can significantly improve the crystallinity and crystal particle size of the electrolyte particles, thereby improving the electrical conductivity of the electrolyte; during grinding, the particle size is controlled to be greater than 20μm to avoid damaging the crystals during the grinding process, resulting in a smaller crystal size and affecting the electrical conductivity of the electrolyte.

[0051] In the process of preparing the high conductivity layer, a dry film-forming process is adopted. On the one hand, it can avoid the external mechanical crushing of the electrolyte particles by a ball mill, etc., and on the other hand, it can avoid the contact of the sulfide solid electrolyte with the organic solvent, which leads to a decrease in conductivity. In the traditional dry film-forming process, the binder is mixed with the electrolyte particles and then subjected to a fiberization treatment to make the binder have bonding force. In the above method, the third binder is first subjected to a fiberization treatment and then mixed with the third sulfide solid electrolyte. This can effectively avoid the fiberization process from crushing the third sulfide solid electrolyte particles and resulting in a reduction in particle size, thereby ensuring that a high conductivity layer containing large-sized electrolyte particles can be prepared, ensuring that the high conductivity layer has high conductivity.

[0052] Optionally, before preparing the first sulfide solid electrolyte, the second sulfide solid electrolyte and the third sulfide solid electrolyte, the raw materials for forming the sulfide solid electrolyte may be ball milled, wherein the ball milling may be a planetary ball mill, the ball milling speed may be 500 to 700 rpm, and the ball milling time may be 10 to 30 h.

[0053] Optionally, the raw materials for forming the sulfide solid electrolyte can be selected within a certain range. For example, the raw materials for forming the sulfide solid electrolyte may include LiCl, Li2S, and P2S5, wherein the molar ratio of LiCl, Li2S, and P2S5 may be 2.6:5:1.

[0054] Optionally, the lithium metal stabilization layer, the lithium dendrite suppression layer, and the high conductivity layer are pressed together to obtain the solid electrolyte membrane, comprising:

[0055] Laminating the high conductivity layer to the non-support contact surface of the lithium dendrite suppression layer, and pressing them at a pressure of 300 to 500 MPa for 10 to 30 minutes to obtain an intermediate product adhered to the support;

[0056] The carrier is removed, and the carrier contact surface of the intermediate product is bonded to the lithium metal stabilization layer and pressed to obtain the solid electrolyte membrane.

[0057] In the above-mentioned process of preparing the solid electrolyte membrane, the high conductivity layer and the lithium dendrite suppression layer are pressed together at a pressure of 300-500 MPa for 10-30 minutes, which can further densify the lithium dendrite suppression layer and ensure that the porosity of the lithium dendrite suppression layer is less than 8%.

[0058] The present invention also provides use of the above-mentioned solid electrolyte membrane in preparing a solid-state battery, wherein the solid-state battery uses lithium metal as the negative electrode.

[0059] The present invention also provides a solid-state battery, which includes the solid-state electrolyte membrane described above and a lithium metal negative electrode.

[0060] The technical solution of the present invention has the following advantages:

[0061] The solid electrolyte membrane provided by the present invention includes a lithium metal stabilization layer, a lithium dendrite suppression layer and a high conductivity layer stacked in sequence, and the above three functional layers are all made of a single sulfide solid electrolyte component, which effectively overcomes the problems existing when the third component is introduced, such as low conductivity of the third component, poor interface contact between the third component and the sulfide solid electrolyte membrane, and difficulty in ensuring stability between the third component and the sulfide solid electrolyte.

[0062] Specifically, the lithium metal stabilization layer contains a first sulfide solid electrolyte, the surface of which is coated with a lithium sulfide protective layer. The lithium sulfide protective layer can effectively prevent the sulfide solid electrolyte from continuing to react with the lithium metal negative electrode, thereby improving the stability of the sulfide solid electrolyte membrane to the lithium metal negative electrode;

[0063] The lithium dendrite suppression layer contains a second sulfide solid electrolyte, and the porosity of the lithium dendrite suppression layer is less than 8%. Therefore, the lithium dendrite suppression layer has a high density, which can effectively prevent lithium dendrites from growing between electrolyte particles, thereby improving the ability of the electrolyte membrane to suppress lithium dendrites, thereby achieving the effect of effectively suppressing the growth of lithium dendrites;

[0064] The high-conductivity layer contains a third sulfide solid electrolyte with a Hinckley crystallinity index greater than 1.1 and a particle size greater than 20 μm. By controlling the third sulfide solid electrolyte to have high crystallinity and particle size, the conductivity of the high-conductivity layer is significantly improved, allowing the solid electrolyte membrane of the present invention to maintain the high conductivity of the sulfide itself.

[0065] Therefore, the solid electrolyte membrane of the present invention adopts a single-component sulfide as the electrolyte without introducing a third component, which significantly improves the stability of the sulfide solid electrolyte membrane to the lithium metal negative electrode, improves the ability of the electrolyte membrane to inhibit lithium dendrites, and maintains the high electrical conductivity of the sulfide itself, ultimately effectively improving the cycle performance and rate performance of the sulfide solid electrolyte-lithium metal negative electrode solid-state battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 This is the electron microscope scanning result of the lithium metal stabilization layer prepared in step (1) of Example 1 of the present invention;

[0068] Figure 2 This is the electron microscope scanning result of the intermediate product obtained in step (4) of Example 1 of the present invention;

[0069] Figure 3 Schematic diagram of the structure of the solid electrolyte membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0070] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0071] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0072] Example 1

[0073] The solid electrolyte membrane was prepared as follows:

[0074] (1) Preparation of lithium metal stabilization layer:

[0075] ① LiCl, Li2S, and P2S5 were mixed in a molar ratio of 2.6:5:1 and ball-milled at 550 rpm for 20 h using a planetary ball mill to obtain a raw material for forming a sulfide solid electrolyte;

[0076] ② The raw materials for forming the sulfide solid electrolyte are sintered at 460° C. for 12 hours, and the sintered materials are ground to a powder particle size of <5 μm to obtain a first sulfide solid electrolyte;

[0077] ③ Take the first sulfide solid electrolyte and mix it with lithium powder in a molar ratio of 1:0.02, and use a planetary ball mill to mix at a speed of 160 rpm for 6 hours to obtain a first sulfide solid electrolyte with a lithium sulfide protective layer on the surface;

[0078] ④ Take 10g of the first sulfide solid electrolyte with a lithium sulfide protective layer and 0.2g of styrene-butadiene rubber, mix them, apply external shear force using a grinder to perform fiberization treatment, and then use a roller press to press the fiberized powder to form an independent film-forming lithium metal stabilization layer;

[0079] After testing, the chemical formula of the sulfide solid electrolyte in the lithium metal stabilization layer prepared in this step is Li 3.15 P 0.5 S 2.5 Cl 0.65 , scanned using a scanning electron microscope, and the results were as follows Figure 1 As shown by Figure 1 It can be seen that the surface of the electrolyte particles in the lithium metal stabilization layer is uniformly covered with a lithium sulfide protective layer. After calculation, the molar ratio of the first sulfide solid electrolyte to lithium sulfide is 1:0.02.

[0080] (2) Preparation of lithium dendrite suppression layer:

[0081] ① LiCl, Li2S, and P2S5 were mixed in a molar ratio of 2.6:5:1 and ball-milled at 550 rpm for 20 h using a planetary ball mill to obtain a raw material for forming a sulfide solid electrolyte;

[0082] ② The raw materials for forming the sulfide solid electrolyte were sintered at 280°C for 6 hours, and the sintered materials were ground to a powder particle size of <5 μm to obtain a second sulfide solid electrolyte;

[0083] ③ Taking the above-mentioned second sulfide solid electrolyte, mixing it with the solvent toluene, and wet-grinding it using a pot mill until the particle size of the second sulfide solid electrolyte is less than 0.5 μm, thereby obtaining a second sulfide solid electrolyte dispersion;

[0084] ④ Dissolve polyvinylidene fluoride in the second sulfide solid electrolyte dispersion obtained in step ③ so that the amount of polyvinylidene fluoride is 2% of the amount of the second sulfide solid electrolyte, and disperse it in a jar mill to prepare an electrolyte slurry with a solid content of 73%;

[0085] ⑤ Coating the electrolyte slurry on the release film to a thickness of 15 μm, and after drying, obtaining a lithium dendrite suppression layer adhered to the release film;

[0086] After testing, the chemical formula of the sulfide solid electrolyte in the lithium dendrite suppression layer prepared in this step is Li 3.15 P 0.5 S 2.5 Cl 0.65 , where the Hinckley crystallinity index of the sulfide solid electrolyte is 0.86.

[0087] (3) Preparation of high conductivity layer:

[0088] ① LiCl, Li2S, and P2S5 were mixed in a molar ratio of 2.6:5:1 and ball-milled at 550 rpm for 20 h using a planetary ball mill to obtain a raw material for forming a sulfide solid electrolyte;

[0089] ② The raw materials for forming the sulfide solid electrolyte were sintered at 570°C for 18 hours, and the sintered materials were ground to control the particle size of the ground powder to be greater than 20 μm, thereby obtaining a third sulfide solid electrolyte. The Hinckley crystallinity index of the third sulfide solid electrolyte was measured to be 1.21 and the conductivity was 7.6 mS / cm.

[0090] ③ Take polytetrafluoroethylene and perform fiberization treatment using an air flow grinder to make it have adhesive strength, thereby obtaining fiberized polytetrafluoroethylene;

[0091] ④ Take 10g of the third sulfide solid electrolyte and 0.05g of fiberized polytetrafluoroethylene, use a blender to mechanically mix them, and then use a roller press to press the mixed powder to form an independent film-forming high conductivity layer.

[0092] After testing, the chemical formula of the sulfide solid electrolyte in the high conductivity layer prepared in this step is Li 3.15 P 0.5 S 2.5 Cl 0.65 .

[0093] (4) Preparation of solid electrolyte membrane:

[0094] ① Laminating the high conductivity layer prepared in step (3) to the non-release film contact surface of the lithium dendrite suppression layer prepared in step (2), and pressing them for 20 minutes under an external pressure of 420 MPa to obtain an intermediate product adhered to the release film;

[0095] The intermediate product obtained in this step was scanned using a scanning electron microscope. Figure 2 As shown by Figure 2 It can be seen that the size of the electrolyte particles in the upper lithium dendrite suppression layer is significantly smaller, and the particles are in close contact with each other, with a porosity of 6%, which can inhibit the growth of lithium dendrites; while the particle size of the electrolyte particles in the lower high conductivity layer is larger, which is conducive to the transmission of lithium ions and the improvement of crystallinity, thereby having a high conductivity effect;

[0096] ② Peel off the release film attached to the intermediate product, and laminate the release film contact surface of the intermediate product after peeling off the release film with the lithium metal stabilization layer prepared in step (1), and press them using a roller press to obtain a solid electrolyte membrane.

[0097] The solid electrolyte membrane prepared in this embodiment is as follows Figure 3 As shown, it consists of a lithium metal stabilization layer, a lithium dendrite suppression layer and a high conductivity layer stacked in sequence, with a total thickness of 50 μm, of which the thickness of the high conductivity layer is 20 μm, the thickness of the lithium dendrite suppression layer is 10 μm, and the thickness of the lithium metal stabilization layer is 20 μm.

[0098] Example 2

[0099] A solid electrolyte membrane was prepared according to the method of Example 1, except that, when preparing the lithium metal stabilization layer in step (1) of this embodiment, the sintering temperature in operation ② was 400° C. and the sintering time was 15 h; in operation ③, the molar ratio of the first sulfide solid electrolyte to the lithium powder was 1:0.01; and in operation ④, the amount of the first sulfide solid electrolyte used was 10 g, and the amount of styrene-butadiene rubber used was 0.5 g.

[0100] In the solid electrolyte membrane prepared in this embodiment, the molar ratio of the first sulfide solid electrolyte to lithium sulfide in the lithium metal stabilization layer is 1:0.01.

[0101] Example 3

[0102] A solid electrolyte membrane was prepared according to the method of Example 1, except that, when preparing the lithium metal stabilization layer in step (1) of this embodiment, the sintering temperature in operation ② was 500° C. and the sintering time was 10 h; in operation ③, the molar ratio of the first sulfide solid electrolyte to the lithium powder was 1:0.05; and in operation ④, the amount of the first sulfide solid electrolyte used was 10 g, and the amount of styrene-butadiene rubber used was 0.1 g.

[0103] In the solid electrolyte membrane prepared in this embodiment, the molar ratio of the first sulfide solid electrolyte to lithium sulfide in the lithium metal stabilization layer is 1:0.05.

[0104] Example 4

[0105] A solid electrolyte membrane was prepared according to the method of Example 1, except that, when preparing the lithium dendrite suppression layer in step (2) of this embodiment, the sintering temperature in operation ② was 260°C and the sintering time was 8 hours; in operation ④, the amount of polyvinylidene fluoride was 3% of the amount of the second sulfide solid electrolyte, and the solid content of the electrolyte slurry after dispersion was 71%.

[0106] In the solid electrolyte membrane prepared in this embodiment, the porosity of the lithium dendrite suppression layer is 5%, and the crystallinity of the sulfide solid electrolyte is 0.81.

[0107] Example 5

[0108] A solid electrolyte membrane was prepared according to the method of Example 1, except that, when preparing the lithium dendrite suppression layer in step (2) of this embodiment, the sintering temperature in operation ② was 350°C and the sintering time was 5 h; in operation ④, the amount of polyvinylidene fluoride used was 6% of the amount of the second sulfide solid electrolyte used, and the solid content of the electrolyte slurry after dispersion was 70%.

[0109] In the solid electrolyte membrane prepared in this embodiment, the porosity of the lithium dendrite suppression layer is 6%, and the crystallinity of the sulfide solid electrolyte is 0.86.

[0110] Example 6

[0111] A solid electrolyte membrane was prepared according to the method of Example 1, except that, when preparing the high conductivity layer in step (3) of this embodiment, the sintering temperature in operation ② was 550° C. and the sintering time was 20 h; in operation ④, the amount of the third sulfide solid electrolyte used was 10 g, and the amount of the fiberized polytetrafluoroethylene used was 0.1 g.

[0112] In the solid electrolyte membrane prepared in this example, the sulfide solid electrolyte in the high conductivity layer has a Hinckley crystallinity index of 1.15 and a conductivity of 7.2 mS / cm.

[0113] Example 7

[0114] A solid electrolyte membrane was prepared according to the method of Example 1, except that, when preparing the high conductivity layer in step (3) of this embodiment, the sintering temperature in operation ② was 630° C. and the sintering time was 15 h; in operation ④, the amount of the third sulfide solid electrolyte used was 10 g, and the amount of the fiberized polytetrafluoroethylene used was 0.06 g.

[0115] In the solid electrolyte membrane prepared in this example, the crystallinity of the sulfide solid electrolyte in the high conductivity layer is 1.32, and the conductivity is 7.9 mS / cm.

[0116] Comparative Example 1

[0117] The solid electrolyte membrane was prepared as follows:

[0118] (1) LiCl, Li2S, and P2S5 were mixed in a molar ratio of 2.6:5:1 and ball-milled at 550 rpm for 20 h using a planetary ball mill to obtain a raw material for forming a sulfide solid electrolyte;

[0119] (2) taking the raw materials for forming the sulfide solid electrolyte, sintering them at 460° C. for 12 h, and grinding the sintered materials until the powder particle size is less than 5 μm to obtain a sulfide solid electrolyte;

[0120] (3) taking the above-mentioned sulfide solid electrolyte, mixing it with lithium powder in a molar ratio of 1:0.02, and using a planetary ball mill at a speed of 160 rpm for 6 hours to obtain a sulfide solid electrolyte with a lithium sulfide protective layer on the surface;

[0121] (4) 10 g of the sulfide solid electrolyte with a lithium sulfide protective layer on the surface and 0.2 g of styrene-butadiene rubber were mixed, and an external shear force was applied using a grinder to perform fiberization treatment. The fiberized powder was then pressed using a roller press to form a solid electrolyte membrane with a thickness of 50 μm.

[0122] Comparative Example 2

[0123] The solid electrolyte membrane was prepared as follows:

[0124] (1) LiCl, Li2S, and P2S5 were mixed in a molar ratio of 2.6:5:1 and ball-milled at 550 rpm for 20 h using a planetary ball mill to obtain a raw material for forming a sulfide solid electrolyte;

[0125] (2) taking the raw materials for forming the sulfide solid electrolyte, sintering them at 280° C. for 6 h, and grinding the sintered materials until the powder particle size is less than 5 μm to obtain a sulfide solid electrolyte;

[0126] ③ Taking the above-mentioned sulfide solid electrolyte, mixing it with the solvent toluene, and wet grinding it using a pot mill until the particle size of the sulfide solid electrolyte is less than 0.5 μm to obtain a sulfide solid electrolyte dispersion;

[0127] ④ Dissolve polyvinylidene fluoride in the sulfide solid electrolyte dispersion obtained in step ③ so that the amount of polyvinylidene fluoride is 2% of the amount of the second sulfide solid electrolyte, and disperse it in a jar mill to prepare an electrolyte slurry with a solid content of 73%;

[0128] ⑤ The above electrolyte slurry was coated on the release film with a coating thickness of 90 μm, and after drying, a solid electrolyte membrane with a thickness of 50 μm was obtained.

[0129] Comparative Example 3

[0130] The solid electrolyte membrane was prepared as follows:

[0131] (1) LiCl, Li2S, and P2S5 were mixed in a molar ratio of 2.6:5:1 and ball-milled at 550 rpm for 20 h using a planetary ball mill to obtain a raw material for forming a sulfide solid electrolyte;

[0132] (2) The raw materials for forming the sulfide solid electrolyte were taken and sintered at 570°C for 18 hours. The sintered materials were ground to control the particle size of the ground powder to be greater than 20 μm, thereby obtaining a sulfide solid electrolyte. The Hinckley crystallinity index of the sulfide solid electrolyte was measured to be 1.21 and the conductivity was 7.6 mS / cm.

[0133] (3) taking polytetrafluoroethylene and performing a fiberization treatment using an air flow grinder to give it adhesive strength, thereby obtaining fiberized polytetrafluoroethylene;

[0134] (4) 10 g of the above-mentioned sulfide solid electrolyte and 0.05 g of fiberized polytetrafluoroethylene were mechanically mixed using a stirrer, and then the mixed powder was pressed using a roller press to form a solid electrolyte membrane with a thickness of 50 μm.

[0135] Comparative Example 4

[0136] The solid electrolyte membrane was prepared as follows:

[0137] (1) A lithium metal stabilization layer with a thickness of 25 μm was prepared according to the method of step (1) in Example 1, and a lithium dendrite suppression layer with a thickness of 25 μm was prepared according to the method of step (2) in Example 1;

[0138] (2) The release film attached to the above-mentioned lithium dendrite suppression layer is peeled off, and the contact surface of the release film of the lithium dendrite suppression layer after peeling off the release film is laminated with the above-mentioned lithium metal stabilization layer, and a roller press is used to press to obtain a solid electrolyte membrane with a thickness of 50 μm.

[0139] Comparative Example 5

[0140] The solid electrolyte membrane was prepared as follows:

[0141] (1) A lithium metal stabilization layer with a thickness of 25 μm was prepared according to the method of step (1) in Example 1, and a high conductivity layer with a thickness of 25 μm was prepared according to the method of step (3) in Example 1;

[0142] (2) The lithium metal stabilizing layer and the high conductivity layer were laminated together and pressed using a roller press to obtain a solid electrolyte membrane with a thickness of 50 μm.

[0143] Comparative Example 6

[0144] The solid electrolyte membrane was prepared as follows:

[0145] (1) preparing a lithium dendrite suppression layer with a thickness of 25 μm according to the method of step (2) in Example 1, and preparing a high conductivity layer with a thickness of 25 μm according to the method of step (3) in Example 1;

[0146] (2) The high conductivity layer was laminated to the non-release film contact surface of the lithium dendrite suppression layer, pressed for 20 minutes under an external pressure of 420 MPa, and the release film was peeled off to obtain a solid electrolyte membrane with a thickness of 50 μm.

[0147] Experimental example

[0148] All-solid-state batteries were prepared using the solid electrolyte membranes prepared in Examples 1 to 7 and Comparative Examples 1 to 6, respectively, and the preparation methods were as follows:

[0149] The positive electrode active material NCM811, the solid electrolyte Li6PS5Cl, the binder polyvinylidene fluoride and the conductive carbon SP were mixed in a mass ratio of 60:30:5:5 to obtain a positive electrode slurry, which was then coated on the surface of an aluminum foil to obtain a positive electrode; a lithium metal sheet was used as the negative electrode; and the positive electrode, solid electrolyte membrane and negative electrode were assembled into an all-solid-state battery according to conventional methods.

[0150] The charge and discharge test system was used to test the rate performance of each all-solid-state battery at 0.33C, 1C, and 4C rates. The test method is as follows:

[0151] (1) 0.33C discharge specific capacity: Using a blue electric test equipment, charge at a constant current of 0.33C, the charge cut-off voltage is 4.2V, and discharge at a constant current at the same current, the discharge cut-off voltage is 3V;

[0152] (2) 1C discharge specific capacity: Using a blue electric test device, charge at a constant current of 1C, with a charge cut-off voltage of 4.2V, and discharge at a constant current of the same current, with a discharge cut-off voltage of 3V;

[0153] (3) 4C discharge specific capacity: Using a blue electric test equipment, charge at 4C constant current with a charge cut-off voltage of 4.2V, and discharge at the same current with a constant current and a discharge cut-off voltage of 3V;

[0154] (4) 4C / 0.33C retention rate: 4C discharge specific capacity / 0.33C discharge specific capacity;

[0155] (5) 50-cycle cycle retention rate: Using a blue electric test device, charge at a constant current of 1C with a charge cut-off voltage of 4.2V, and discharge at a constant current of 3V at the same current for 50 cycles.

[0156] The test results are shown in Table 1.

[0157] Table 1 Rate performance test results of various all-solid-state batteries

[0158]

[0159]

[0160] The solid electrolyte membrane of Comparative Example 1 was prepared into an all-solid-state battery. After 23 cycles, lithium dendrites inside the battery pierced the solid electrolyte membrane, causing a short circuit. This was because the solid electrolyte membrane only contained a lithium metal stabilization layer but no lithium dendrite suppression layer.

[0161] The solid electrolyte membrane of Comparative Example 2 was prepared into an all-solid-state battery, and the retention rate was 62.3% after 50 cycles, which was much lower than 93.5% of Example 1. This was because the sulfide solid electrolyte in the solid electrolyte layer of Comparative Example 2 reacted with the lithium metal negative electrode, causing the structure of the electrolyte itself to collapse, forming a mixed product of ionic and electronic conductivity, resulting in a significant decrease in the ionic conductivity of the electrolyte, which ultimately manifested as increased battery polarization, a significant decrease in charge and discharge capacity, and rapid decay of the battery capacity.

[0162] The solid electrolyte membrane of Comparative Example 3 was prepared into an all-solid-state battery. In the first cycle, lithium dendrites pierced the solid electrolyte membrane, causing a battery short circuit. This was because the solid electrolyte layer only contained a high conductivity layer. The electrolyte particles in the high conductivity layer were larger, and the gaps between the particles were larger, which made it easy for lithium dendrites to grow in the gaps, causing a battery short circuit.

[0163] The solid electrolyte membrane of Comparative Example 4 was prepared into an all-solid-state battery, and the 4C / 0.33C capacity retention rate was 73.6%, which was significantly lower than 84.5% of Example 1. This was because the solid electrolyte membrane prepared in Comparative Example 4 did not have a high conductivity layer, resulting in its conductivity being lower than that of the solid electrolyte membrane prepared in Example 1, resulting in poor rate performance.

[0164] The solid electrolyte membrane of Comparative Example 5 was made into an all-solid-state battery. When it was cycled for 11 weeks, lithium dendrites inside the battery pierced the solid electrolyte membrane, causing a short circuit. This was caused by the lack of a lithium dendrite suppression layer in the solid electrolyte membrane.

[0165] The solid electrolyte membrane of Comparative Example 6 was prepared into an all-solid-state battery, and the retention rate was 42.6% after 50 cycles, which was much lower than 93.5% of Example 1. This was because there was no lithium metal stabilization layer in the solid electrolyte layer of Comparative Example 6, and the sulfide solid electrolyte reacted with the lithium metal negative electrode, causing the structure of the electrolyte itself to collapse, forming a mixed product of ionic and electronic conductivity, resulting in a significant decrease in the ionic conductivity of the electrolyte, which ultimately manifested as increased battery polarization, a significant decrease in charge and discharge capacity, and rapid decay of the battery capacity.

[0166] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A solid electrolyte membrane, characterized in that It includes a lithium metal stabilization layer, a lithium dendrite suppression layer and a high conductivity layer stacked in sequence; wherein, The lithium metal stabilization layer is composed of a first sulfide solid electrolyte and a first binder, and the surface of the first sulfide solid electrolyte is coated with a lithium sulfide protective layer; The lithium dendrite suppression layer is composed of a second sulfide solid electrolyte and a second binder, and the porosity of the lithium dendrite suppression layer is less than 8%; The high conductivity layer is composed of a third sulfide solid electrolyte and a third binder. The third sulfide solid electrolyte has a Hinkley crystallinity index greater than 1.1 and a particle size greater than 20 μm.

2. The solid electrolyte membrane according to claim 1, characterized in that The molar ratio of the first sulfide solid electrolyte to lithium sulfide is 1:(0.01-0.05).

3. The solid electrolyte membrane according to claim 2, characterized in that The particle size of the first sulfide solid electrolyte is less than 5 μm.

4. The solid electrolyte membrane according to claim 3, characterized in that The weight of the first binder is 1% to 5% of the weight of the first sulfide solid electrolyte.

5. The solid electrolyte membrane according to claim 4, characterized in that The first binder does not contain a fluorinated group.

6. The solid electrolyte membrane according to claim 5, characterized in that The first binder includes at least one of styrene-butadiene rubber, nitrile-butadiene rubber, polyethylene and polypropylene.

7. The solid electrolyte membrane according to claim 1, characterized in that The second sulfide solid electrolyte has a Hinkley crystallinity index of 0.8 to 1 and a particle size of less than 0.5 μm.

8. The solid electrolyte membrane according to claim 7, characterized in that The weight of the second binder is 2% to 6% of the weight of the second sulfide solid electrolyte.

9. The solid electrolyte membrane according to claim 8, characterized in that The second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyisoprene, nitrile rubber and styrene-butadiene rubber.

10. The solid electrolyte membrane according to claim 1, characterized in that The electrical conductivity of the third sulfide solid electrolyte is greater than 7 mS / cm.

11. The solid electrolyte membrane according to claim 10, characterized in that The weight of the third binder is 0.5-1.5% of the weight of the third sulfide solid electrolyte.

12. The solid electrolyte membrane according to claim 11, characterized in that The third binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polybutylene and polyethylene oxide.

13. A method for preparing a solid electrolyte membrane according to any one of claims 1 to 12, characterized in that: The steps include: contacting the first sulfide solid electrolyte with lithium powder and reacting them, and forming a film of the obtained product by a dry process to obtain a lithium metal stabilization layer; The second sulfide solid electrolyte is prepared into an electrolyte slurry having a solid content greater than 70%, coated on a support, and dried to obtain a lithium dendrite suppression layer adhered to the support; forming a third sulfide solid electrolyte by a dry process to obtain a high conductivity layer, wherein the third sulfide solid electrolyte has a Hinkley crystallinity index greater than 1.1 and a particle size greater than 20 μm; The lithium metal stabilization layer, the lithium dendrite suppression layer and the high conductivity layer are pressed together to obtain the solid electrolyte membrane.

14. The preparation method according to claim 13, characterized in that The preparation process of the first sulfide solid electrolyte includes: The raw materials for forming the sulfide solid electrolyte are sintered at 400-500° C. for 10-15 hours, and the obtained sintered material is ground to a particle size of less than 5 μm to obtain the first sulfide solid electrolyte.

15. The preparation method according to claim 14, characterized in that The method of contacting and reacting the first sulfide solid electrolyte with lithium powder and forming a film of the obtained product by a dry process to obtain a lithium metal stabilization layer comprises: The first sulfide solid electrolyte and the lithium powder are mixed in a molar ratio of 1: (0.01-0.05), and ball milled at a speed of 150-200 rpm for 4-8 hours to obtain a first sulfide solid electrolyte having a lithium sulfide protective layer coated on the surface; The first sulfide solid electrolyte with a lithium sulfide protective layer on its surface is mixed with a first binder and subjected to a fiberization treatment. The obtained powder is pressed into a film to obtain the lithium metal stabilization layer.

16. The preparation method according to claim 13, characterized in that The preparation process of the second sulfide solid electrolyte includes: The raw materials for forming the sulfide solid electrolyte are sintered at 260-350° C. for 5-8 hours, and the obtained sintered material is ground to a particle size of less than 5 μm to obtain the second sulfide solid electrolyte.

17. The preparation method according to claim 16, characterized in that The second sulfide solid electrolyte is prepared into an electrolyte slurry with a solid content greater than 70%, coated on a carrier, and dried to obtain a lithium dendrite suppression layer, comprising: mixing the second sulfide solid electrolyte with a solvent, and wet-grinding the mixture until the particle size of the second sulfide solid electrolyte is less than 0.5 μm to obtain a second sulfide solid electrolyte dispersion; dispersing a second binder in the second sulfide solid electrolyte dispersion to prepare an electrolyte slurry having a solid content greater than 70%; The electrolyte slurry is coated on the carrier and dried to obtain the lithium dendrite suppression layer adhered to the carrier.

18. The preparation method according to claim 13, characterized in that The preparation process of the third sulfide solid electrolyte includes: The raw materials for forming the sulfide solid electrolyte are sintered at 550-630° C. for 15-20 hours, and the obtained sintered material is ground to a particle size greater than 20 μm to obtain the third sulfide solid electrolyte.

19. The preparation method according to claim 18, characterized in that The method of forming a high conductivity layer by dry-forming the third sulfide solid electrolyte comprises: performing a fiberization treatment on the third binder to obtain a fiberized third binder; The fiberized third binder is mixed with the third sulfide solid electrolyte, and the obtained powder is pressed into a film to obtain the high conductivity layer.

20. Use of the solid electrolyte membrane according to any one of claims 1 to 12 in the preparation of a solid-state battery, wherein the solid-state battery uses lithium metal as the negative electrode.

21. A solid-state battery, characterized in that: The solid-state battery comprises the solid electrolyte membrane according to any one of claims 1 to 12 and a lithium metal negative electrode.

Images