A solid electrolyte membrane and its preparation method

Abstract

The present invention discloses a solid electrolyte membrane and a preparation method thereof, which is made of solid electrolyte powder, a first binder, a second binder, a lithium salt and a lithium salt complexing agent. In the present invention, the first binder and the second binder mutually construct a bonding network with different orientations, uniformly dispersing the solid electrolyte powder and the lithium salt therein. By adding the lithium salt complexing agent, during grinding and stirring, the lithium salt and the lithium salt complexing agent are complexed to form a low-melting deep eutectic compound, which swells the second binder to form an ion-conducting binder in situ. The low-melting deep eutectic compound is usually composed of a Lewis acid and a Lewis base. The low-melting deep eutectic compound has the advantages of low price, safety, a wide electrochemical window and good thermal / chemical stability. In the presence of a binder, the solid electrolyte membrane prepared by the present invention has high ion conductivity, good chemical properties, safety, strong film-forming properties and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a solid electrolyte membrane and a preparation method thereof. Background Art

[0002] Solid electrolytes are mainly divided into inorganic solid electrolytes, solid polymer electrolytes and organic-inorganic composite electrolytes.

[0003] Inorganic solid electrolytes have high ion conductivity, but they are hard and brittle, and have harsh preparation process conditions. They require synthesis at high temperature and compaction at GPa level, and the preparation conditions are harsh.

[0004] The preparation of polymer electrolytes is usually achieved by solvent evaporation of "polymer-lithium salt solution", which needs to be carried out under oxygen and moisture-proof conditions. It is time-consuming, energy-consuming and pollutes the environment. The mechanical strength is difficult to meet the requirements of large-scale roll-to-roll preparation and is not suitable for existing lithium battery production lines.

[0005] The organic-inorganic composite electrolyte has large differences in the properties of its two phases, which leads to new interface problems. Particle agglomeration often occurs, resulting in low ion conductivity and poor yield. In addition, the interface of the lithium negative electrode / electrolyte still has the difference between hard contact and soft contact, and uneven ion conduction causes the disordered growth of lithium dendrites.

[0006] Solid electrolyte powders are typically treated with binders such as polytetrafluoroethylene and polyvinylidene fluoride, which are then rolled and hot-pressed into films. This bonding, even at very low binder levels, significantly reduces the electrolyte's ionic conductivity, thus limiting its application. Furthermore, existing solid electrolytes suffer from issues such as poor ion transport and interfacial stability, as well as demanding preparation conditions. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a solid electrolyte membrane and a preparation method in response to the above-mentioned deficiencies in the prior art. The solid electrolyte membrane designed by the present invention can solve the above-mentioned problems and has a high ion conductivity in the presence of a binder. In addition, the solid electrolyte membrane of the present invention is easy to prepare and can be easily prepared into rolls, which is conducive to large-scale production in the industry.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A solid electrolyte membrane is made of solid electrolyte powder, a first binder, a second binder, a lithium salt, and a lithium salt complexing agent, wherein the weight percentages are as follows:

[0010] Solid powder electrolyte 70~99%,

[0011] The first binder 0.01-10%,

[0012] The second binder 0.01-10%,

[0013] Lithium salt 0.01-10%,

[0014] Lithium salt complexing agent 0.05-10%.

[0015] Preferably, in the above-mentioned solid electrolyte membrane, the solid electrolyte powder includes an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte or a polymer solid electrolyte. The function of the solid electrolyte powder is to improve ion conductivity.

[0016] Preferably, in the above-mentioned solid electrolyte membrane, the oxide-based solid electrolyte is lithium lanthanum zirconium oxide (LLZO), lithium aluminum titanium phosphate (LATP) or lithium lanthanum titanium oxide (LLTO).

[0017] The sulfide solid electrolyte is Li 10 MP2S 12 、70Li2S-30P2S5、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , lithium phosphorus sulfur (LPS), lithium germanium phosphorus sulfur (LGPS) or Li2S-P2S5, etc.;

[0018] The halide solid electrolyte is Li3InCl6, Li3YCl6 or Li2ZrCl6;

[0019] The polymer solid electrolyte is modified cellulose or the like.

[0020] Preferably, in the above-mentioned solid electrolyte membrane, the first binder is one or more of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). The first binder provides primary bonding force and a bonding network, thereby enabling the solid electrolyte powder to form a film.

[0021] Preferably, in the above-mentioned solid electrolyte membrane, the second binder is one or more of polyether polyamide block copolymer (PEBAX), polyether (PEO), and polycarbonate. The function of the second binder is to be swollen by the lithium salt and the lithium salt complexing agent to form a deep eutectic compound, forming an ion-conducting binder in situ and forming a bonding network with the first binder.

[0022] Preferably, in the above-mentioned solid electrolyte membrane, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl imide), lithium bis(difluorosulfonyl imide), lithium bis(oxalatoborate), lithium perchlorate, lithium tetrafluoroborate, and lithium hexafluorophosphate. The lithium salt provides ionic conductivity and forms a low-melting-depth eutectic compound with a lithium salt complexing agent.

[0023] Preferably, in the above-mentioned solid electrolyte membrane, the lithium salt complexing agent is an amide, nitrile, carbonate, sulfonic acid, or sulfonamide compound. The lithium salt complexing agent can form a eutectic compound with the lithium salt, has properties such as a low melting point and low volatility, and can swell the second binder to form an in-situ functional binder having ion-conducting channels and adhesive properties.

[0024] A method for preparing a solid electrolyte membrane comprises the following steps:

[0025] S1: Grinding and blending the solid electrolyte powder and the first binder for 1-9 hours at a temperature of 20-120° C. to obtain a uniform mixture a;

[0026] S2: Add the second binder to the mixed material a and grind and blend for 1-5 hours at a temperature of 20-60°C to obtain a uniform material b;

[0027] S3: Add lithium salt to the uniform material b and grind and blend for 1-5 hours at a temperature of 20-60°C to obtain a uniform material e;

[0028] S4: adding a lithium salt complexing agent to the uniform material e and grinding and blending the mixture for 1-5 hours at a temperature of 20-60° C. to obtain a uniform material f;

[0029] S5: The uniform material f is allowed to stand for aging for 1-24 hours at a temperature of 20-80°C. After the material f is allowed to stand, it is crushed and ground into material g;

[0030] S6: Roll-pressing the material g at a roller spacing of 0.1-5000 μm and a roller pressing temperature of 20-60° C., and hot-pressing the rolled material at a pressure of 1-100 MPa and a temperature of 20-80° C. to obtain a solid electrolyte membrane. The obtained solid electrolyte membrane has a thickness of 10-100 μm.

[0031] A battery is prepared from the above-mentioned solid electrolyte membrane.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] In the solid electrolyte membrane of the present invention, the first binder and the second binder mutually construct a bonding network of different orientations, uniformly dispersing the solid electrolyte powder and lithium salt therein. By adding a lithium salt complexing agent, during grinding and stirring, the lithium salt and the lithium salt complexing agent complex to form a low-melting deep eutectic compound, which swells the second binder to form an ion-conducting binder in situ. Low-melting deep eutectic compounds are usually composed of Lewis acids and Lewis bases. In the present invention, the Lewis acid is played by lithium salt and the Lewis base is played by lithium salt complexing agent. Low-melting deep eutectic compounds have the advantages of low price, safety, wide electrochemical window and good thermal / chemical stability. Combined with the advantages of solid electrolyte powder, the solid electrolyte membrane prepared by the present invention has high ion conductivity, good chemical properties, safety, strong film forming properties and low cost in the presence of a binder. DETAILED DESCRIPTION

[0034] The present invention relates to a solid electrolyte membrane, a method for preparing the membrane, and its application in lithium-ion batteries. The technical solutions of the present invention are described in detail below with reference to examples. The examples described are only part of the present invention and are intended only to illustrate the present invention and are not intended to limit the present invention.

[0035] Example 1: A method for preparing a solid electrolyte membrane, comprising the following steps:

[0036] ① Weigh the solid powder electrolyte (electrolyte powder lithium aluminum titanium phosphate (LATP) and oxidized cellulose electrolyte) with the first binder polytetrafluoroethylene (PTFE), the second binder polyether polyamide block copolymer (PEBAX), the lithium salt lithium bistrifluoromethylsulfonyl imide (LITFSI), and N-methylacetamide (NMA) in a mass ratio of 95:2:0.6:1.2:1.2.

[0037] ② The electrolyte powder LATP, oxidized cellulose electrolyte and the first binder PTFE were mixed and ground for 4 hours at a temperature of 100°C. After fiberization, the second binder PEBAX was added and ground for 3 hours at a temperature of 80°C.

[0038] ③ Add lithium salt lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) to the material obtained in step ② and grind for 2 hours at 40°C.

[0039] ④ Add lithium salt complexing agent NMA to the material obtained in step ③ and grind for 2 hours at 40°C.

[0040] ⑤ The material obtained in step ④ was allowed to stand for 24 hours at a temperature of 80°C, and then crushed and ground into powder;

[0041] ⑥ The material obtained in step ⑤ was roller pressed with a roller spacing of 200 μm and a roller pressing temperature of 60°C.

[0042] ⑦ The material obtained in step ⑥ was hot pressed at a pressure of 80 MPa and a temperature of 60° C. to obtain a solid electrolyte membrane with a thickness of 40 μm.

[0043] Example 2: A method for preparing a solid electrolyte membrane, comprising the following steps:

[0044] ① Weigh the electrolyte powder LLZO, the first binder polytetrafluoroethylene (PTFE), the second binder polyether polyamide block copolymer (PEBAX), the lithium salt lithium bistrifluoromethylsulfonyl imide LITFSI, and the lithium salt complexing agent succinonitrile in a mass ratio of 95:2:0.6:1.2:1.2.

[0045] ② The electrolyte powder LLZO and the first binder polytetrafluoroethylene (PTFE) were ground for 4 hours at 100°C. After fiberization, the second binder PEBAX was added and ground for 3 hours at 80°C.

[0046] ③ Add lithium salt lithium bis(trifluoromethylsulfonyl)imide (LITFSI) to the material obtained in step ② and grind for 2 hours at 40°C.

[0047] ④ Add lithium salt complexing agent succinonitrile to the material obtained in step ③ and grind for 2 hours at 40°C.

[0048] ⑤ The material obtained in step ④ is allowed to stand for aging for 24 hours at a temperature of 60° C. After standing, it is crushed and ground into powder.

[0049] ⑥ The material obtained in step ⑤ was roller pressed with a roller spacing of 200 μm and a roller pressing temperature of 60°C.

[0050] ⑦ The material obtained in step ⑥ was hot pressed at a pressure of 80 MPa and a temperature of 60° C. to obtain a solid electrolyte membrane with a thickness of 50 μm.

[0051] Example 3: A method for preparing a solid electrolyte membrane, comprising the following steps:

[0052] ① Weigh the electrolyte powder Li3InCl6, the first binder polytetrafluoroethylene (PTFE), the second binder polyether polyamide block copolymer (PEBAX), the lithium salt lithium bistrifluoromethylsulfonyl imide LITFSI, and the lithium salt complexing agent N-methylurea (MU) in a mass ratio of 95:2:0.6:1.2:1.2.

[0053] ② Electrolyte powder Li3InCl6 was ground with the first binder PTFE for 4 hours at 100°C. After fiberization, the second binder PEBAX was added and ground for 3 hours at 80°C.

[0054] ③ Add lithium salt lithium bis(trifluoromethylsulfonyl)imide (LITFSI) to the material obtained in step ② and grind for 2 hours at 40°C.

[0055] ④ Add lithium salt complexing agent MU to the material obtained in step ③ and grind for 2 hours at 40°C.

[0056] ⑤ The material obtained in step ④ is allowed to stand for aging for 24 hours at a temperature of 70°C, and then crushed and ground into powder.

[0057] ⑥ The material obtained in step ⑤ was roller pressed with a roller spacing of 200 μm and a roller pressing temperature of 60°C.

[0058] ⑦ The material obtained in step ⑥ was hot pressed at a pressure of 80 MPa and a temperature of 60° C. to obtain a solid electrolyte membrane with a thickness of 40 μm.

[0059] Example 4: A method for preparing a solid electrolyte membrane, comprising the following steps:

[0060] ① Weigh the electrolyte powder Li3InCl6, the first binder polyvinylidene fluoride (PVDF), the second binder polycarbonate (PPC), the lithium salt lithium bistrifluoromethylsulfonyl imide LITFSI, and the lithium salt complexing agent N-methylacetamide (NMA) in a mass ratio of 95:2:0.6:1.2:1.2.

[0061] ② Electrolyte powder Li3InCl6 and the first binder PVDF were ground for 4 hours at 100°C. After fiberization, the second binder PPC was added and ground for 3 hours at 80°C.

[0062] ③ Add lithium salt lithium bis(trifluoromethylsulfonyl)imide (LITFSI) to the material obtained in step ② and grind for 2 hours at 40°C.

[0063] ④ Add lithium salt complexing agent NMA to the material obtained in step ③ and grind for 2 hours at 40°C.

[0064] ⑤ The material obtained in step ④ is allowed to stand for aging for 24 hours at a temperature of 70°C, and then crushed and ground into powder.

[0065] ⑥ The material obtained in step ⑤ was roller pressed with a roller spacing of 200 μm and a roller pressing temperature of 60°C.

[0066] ⑦ The material obtained in step ⑥ was hot pressed at a pressure of 80 MPa and a temperature of 60° C. to obtain a solid electrolyte membrane with a thickness of 40 μm.

[0067] Comparative Example 1:

[0068] A method for preparing a solid electrolyte membrane comprises the following steps:

[0069] ① Weigh the electrolyte powder Li3InCl6, the first binder polyvinylidene fluoride (PVDF), the lithium salt lithium bis(trifluoromethylsulfonyl)imide LITFSI, and the lithium salt complexing agent N-methylurea (MU) in a mass ratio of 95:2.6:1.2:1.2.

[0070] ② Grind the electrolyte powder Li3InCl6 and the first binder PVDF for 4 hours at a temperature of 100°C.

[0071] ③ Add lithium salt lithium bis(trifluoromethylsulfonyl)imide (LITFSI) to the material obtained in step ② and grind for 2 hours at 40°C.

[0072] ④ Add lithium salt complexing agent MU to the material obtained in step ③ and grind for 2 hours at 40°C.

[0073] ⑤ The material obtained in step ④ is allowed to stand for aging for 24 hours at a temperature of 70°C, and then crushed and ground into powder.

[0074] ⑥ The material obtained in step ⑤ was roller pressed with a roller spacing of 200 μm and a roller pressing temperature of 60°C.

[0075] ⑦ The material obtained in step ⑥ was hot pressed at a pressure of 80 MPa and a temperature of 60° C. to obtain a solid electrolyte membrane with a thickness of 100 μm.

[0076] Table 1: Solid electrolyte membrane performance parameters

[0077]

[0078] It can be seen from Table 1 that the introduction of the second binder effectively improves the ionic conductivity and film-forming properties of the electrolyte.

Claims

1. A solid electrolyte membrane, characterized in that It is made of solid electrolyte powder, a first binder, a second binder, a lithium salt and a lithium salt complexing agent, and the weight percentages are as follows: Solid powder electrolyte 70~99%, The first binder 0.01-10%, The second binder 0.01-10%, Lithium salt 0.01-10%, Lithium salt complexing agent 0.05-10%; The solid electrolyte powder includes an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte or a polymer solid electrolyte; The oxide solid electrolyte is lithium lanthanum zirconium oxide, lithium aluminum titanium phosphate or lithium lanthanum titanium oxide; The sulfide solid electrolyte is Li 10 MP2S 12 、70Li2S-30P2S5、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , lithium phosphorus sulfur, lithium germanium phosphorus sulfur or Li2S-P2S5; The halide solid electrolyte is Li3InCl6, Li3YCl6 or Li2ZrCl6; The polymer solid electrolyte is a cellulose-based solid electrolyte; The first binder is one or more of polytetrafluoroethylene and polyvinylidene fluoride; The second binder is one or more of polyether polyamide block copolymer, polyether, and polycarbonate.

2. The solid electrolyte membrane according to claim 1, characterized in that The lithium salt is one or more of lithium bis(trifluoromethylsulfonyl imide), lithium bis(difluorosulfonyl imide), lithium bis(oxalatoborate), lithium perchlorate, lithium tetrafluoroborate, and lithium hexafluorophosphate.

3. The solid electrolyte membrane according to claim 1, characterized in that The lithium salt complexing agent is an amide, nitrile, carbonate, sulfonic acid or sulfonamide compound.

4. A method for preparing a solid electrolyte membrane according to claim 1, characterized in that The following steps are involved: S1: Grinding and blending the solid electrolyte powder and the first binder for 1-9 hours at a temperature of 20-120° C. to obtain a uniform mixture a; S2: Add the second binder to the mixed material a and grind and blend for 1-5 hours at a temperature of 20-60°C to obtain a uniform material b; S3: Add lithium salt to the uniform material b and grind and blend for 1-5 hours at a temperature of 20-60°C to obtain a uniform material e; S4: adding a lithium salt complexing agent to the uniform material e and grinding and blending the mixture for 1-5 hours at a temperature of 20-60° C. to obtain a uniform material f; S5: The uniform material f is allowed to stand for aging for 1-24 hours at a temperature of 20-80°C. After the material f is allowed to stand, it is crushed and ground into material g; S6: Rolling the material g with a rolling spacing of 0.1-5000 μm and a rolling temperature of 20-60° C., hot pressing the rolled material with a hot pressing pressure of 1-100 MPa and a hot pressing temperature of 20-80° C. to obtain a solid electrolyte membrane.

5. A battery characterized by The solid electrolyte membrane is prepared from the solid electrolyte membrane according to any one of claims 1 to 3.

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