A double-layer solid-state electrolyte and a solid-state battery

Abstract

The application provides a double-layer solid-state electrolyte and a solid-state battery, and belongs to the technical field of solid-state batteries.The double-layer solid-state electrolyte is composed of a first layer of solid-state electrolyte and a second layer of solid-state electrolyte; the first layer of solid-state electrolyte is composed of a halide solid-state electrolyte and a first polymer electrolyte; the halide solid-state electrolyte is composed of a large-particle halide solid-state electrolyte and a small-particle halide solid-state electrolyte; the second layer of solid-state electrolyte is composed of a sulfide solid-state electrolyte and a second polymer electrolyte; and the sulfide solid-state electrolyte is composed of a large-particle sulfide solid-state electrolyte and a small-particle sulfide solid-state electrolyte. The double-layer solid-state electrolyte is assembled into a solid-state battery together with a positive electrode sheet and a negative electrode sheet. The application sets the double-layer electrolyte with different components and different particle sizes, optimizes the contact between the electrolyte material and the interface between the electrolyte and the electrode, and improves the ionic conductivity, cycle performance and rate performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state batteries, in particular to a double-layer solid-state electrolyte and a solid-state battery. BACKGROUND

[0002] With the rapid development of new energy vehicles and portable electronic devices, the demand for high safety batteries is increasing, and solid-state batteries have been widely concerned as an important technical route to solve the safety problem.

[0003] Solid-state batteries can solve the safety problem because solid-state electrolytes replace traditional electrolytes and separators. At present, solid-state electrolytes are mainly divided into inorganic solid-state electrolytes, polymer electrolytes and inorganic-organic composite composite electrolytes. One of the composite electrolytes is to fill inorganic solid-state electrolytes into polymer electrolytes, but due to the physical property difference between inorganic electrolytes and polymer electrolytes, the composite electrolyte has low conductivity and high impedance, thereby affecting the electrochemical performance of the solid-state battery. SUMMARY

[0004] Therefore, the present application aims to provide a double-layer solid-state electrolyte and a solid-state battery.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] One of the technical schemes of the present application is a double-layer solid-state electrolyte composed of a first layer of solid-state electrolyte and a second layer of solid-state electrolyte; the first layer of solid-state electrolyte is composed of a halide solid-state electrolyte and a first polymer electrolyte; the halide solid-state electrolyte is composed of a large-particle halide solid-state electrolyte and a small-particle halide solid-state electrolyte, wherein the average particle size of the large-particle halide solid-state electrolyte is 1.0 pm≤D 50 ≤3.0 pm, and the average particle size of the small-particle halide solid-state electrolyte is 0.1 pm≤D 50 ≤0.5 pm;

[0007] The second layer of solid-state electrolyte is composed of a sulfide solid-state electrolyte and a second polymer electrolyte; the sulfide solid-state electrolyte is composed of a large-particle sulfide solid-state electrolyte and a small-particle sulfide solid-state electrolyte, wherein the average particle size of the large-particle sulfide solid-state electrolyte is 1.0 pm≤D 50 ≤30 pm, and the average particle size of the small-particle sulfide solid-state electrolyte is 0.1 pm≤D 50 ≤0.5 pm.

[0008] In the present application, by mass percentage, in the first layer of solid-state electrolyte, the first polymer electrolyte is 10-30%, the small-particle halide solid-state electrolyte is 10%-60%, and the balance is the large-particle halide solid-state electrolyte;

[0009] The second polymer electrolyte is 10-30%, the large-particle sulfide solid electrolyte is 10-60%, and the balance is the small-particle sulfide solid electrolyte in the second layer solid electrolyte by mass percentage.

[0010] In the application, the halide solid electrolyte is at least one selected from Li3YCl6, Li3InCl6, Li3ScCl6, Li3YBr6, Li2ZrCl6 and Li3ErCl6.

[0011] In the application, the first polymer electrolyte is PVDF-HFP and / or PAN; the molecular weight of the PAN is 150-250 thousand.

[0012] In the application, the sulfide solid electrolyte is at least one selected from Li6PS5Cl, Li6PS5Br, Li7P3S 11 , Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75 S4.

[0013] In the application, the second polymer electrolyte is at least one selected from PEO, PVA, PAA and PMMA; the molecular weight of the PEO is 200-300 thousand; the molecular weight of the PVA is 200-300 thousand.

[0014] In the application, the thickness of the first layer solid electrolyte is 10-100 mu m; the thickness of the second layer solid electrolyte is 10-100 mu m.

[0015] The second technical scheme of the application is a solid-state battery, comprising a positive electrode sheet, a negative electrode sheet and the above-mentioned double-layer solid electrolyte; wherein the positive electrode sheet is arranged in contact with the first layer solid electrolyte; and the negative electrode sheet is arranged in contact with the second layer solid electrolyte.

[0016] The application discloses the following technical effects:

[0017] The application can realize uniform dispersion and low energy barrier at the same time by filling a certain amount of large-particle and small-particle inorganic electrolyte in the polymer electrolyte, so as to improve the conductivity of the electrolyte layer.

[0018] The double-layer solid electrolyte is assembled into a solid-state battery together with the positive electrode sheet and the negative electrode sheet, different components and different particle sizes of the double-layer electrolyte are arranged, the contact between the electrolyte material and the interface between the electrolyte and the electrode is optimized at the same time, and the ion conductivity, the cycle performance and the rate performance are improved. DETAILED DESCRIPTION

[0019] The following detailed description of various exemplary embodiments of the application will not be considered limiting of the application, but rather a description of certain aspects, features, and embodiments of the application.

[0020] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, for a range of values of a parameter, unless otherwise stated, each intervening value of the parameter, as well as any other stated or intervening value of the parameter, is encompassed. The intervening values of the parameter are obtained by simply "slicing" or interpolating the range of values of the parameter. These intervening values are also encompassed within the application.

[0021] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the present specification will control.

[0022] Various modifications and changes can be made to the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0023] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0024] A first aspect of the present application provides a double-layer solid-state electrolyte composed of a first layer solid-state electrolyte and a second layer solid-state electrolyte; the first layer solid-state electrolyte is composed of a halide solid-state electrolyte and a first polymer electrolyte; the halide solid-state electrolyte is composed of a large-particle halide solid-state electrolyte and a small-particle halide solid-state electrolyte, wherein the average particle diameter of the large-particle halide solid-state electrolyte is 1.0 μm ≤ D 50 ≤ 3.0 μm, and the average particle diameter of the small-particle halide solid-state electrolyte is 0.1 μm ≤ D 50 ≤ 0.5 μm;

[0025] The second layer solid-state electrolyte is composed of a sulfide solid-state electrolyte and a second polymer electrolyte; the sulfide solid-state electrolyte is composed of a large-particle sulfide solid-state electrolyte and a small-particle sulfide solid-state electrolyte, wherein the average particle size of the large-particle sulfide solid-state electrolyte is 1.0 μm≤D 50 ≤3.0 μm, and the average particle size of the small-particle sulfide solid-state electrolyte is 0.1 μm≤D 50 ≤0.5 μm.

[0026] Compared with a single polymer electrolyte or a single inorganic electrolyte (halide electrolyte, sulfide electrolyte, oxide electrolyte, etc.), the composite electrolyte combines the advantages of polymer electrolytes and inorganic electrolytes, so that the ionic conductivity of the composite electrolyte is higher than that of the polymer electrolyte, and the flexibility and the interface impedance between the electrolyte and the electrode are better than those of the inorganic electrolyte.

[0027] The present application can further improve the ionic conductivity of the electrolyte layer by simultaneously filling large-particle inorganic solid-state electrolyte and small-particle inorganic solid-state electrolyte in the polymer electrolyte. The inorganic solid-state electrolyte is a halide solid-state electrolyte or a sulfide solid-state electrolyte.

[0028] It can be understood here that filling all small-size inorganic electrolyte particles in the polymer electrolyte is prone to prepare a composite electrolyte with uneven composition, because the small-size inorganic electrolyte particles are difficult to uniformly disperse when mixed with the polymer solution, and the inorganic electrolyte particles are prone to agglomeration; filling all large-size inorganic electrolyte particles in the polymer electrolyte can solve the dispersion difficulty, but the large particle size increases the energy barrier (activation energy) to be crossed at the organic / inorganic interface, reducing the ionic conductivity of the composite electrolyte; therefore, simultaneously filling a certain amount of large-particle and small-particle inorganic electrolyte in the polymer electrolyte can achieve uniform dispersion and low energy barrier crossing, thereby improving the conductivity of the electrolyte layer.

[0029] In the present application, the D 50 may be 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.5 μm, 3.0 μm, or any value between any two of the foregoing values, and the D 50 may be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or any value between any two of the foregoing values.

[0030] The D 50The D50 of the small particle sulfide solid electrolyte can be 1.0 pm, 1.1 pm, 1.2 pm, 1.3 pm, 1.4 pm, 1.5 pm, 1.6 pm, 1.7 pm, 1.8 pm, 1.9 pm, 2.0 pm, 2.5 pm, 3.0 pm, or any value between any two of the foregoing values. 50 The D50 of the small particle halide solid electrolyte can be 0.1 pm, 0.2 pm, 0.3 pm, 0.4 pm, 0.5 pm, or any value between any two of the foregoing values.

[0031] In some embodiments, the D50 of the large particle halide solid electrolyte and the D50 of the large particle sulfide solid electrolyte in each double-layer electrolyte can be the same. 50 The D50 of the small particle halide solid electrolyte and the D50 of the small particle sulfide solid electrolyte in each double-layer electrolyte can be the same or different. 50 The D50 of the small particle halide solid electrolyte and the D50 of the small particle sulfide solid electrolyte in each double-layer electrolyte can be the same or different.

[0032] Notably, the D50 of the large particle electrolyte 50 The D50 of the small particle electrolyte is too large to affect ion transport at the organic / inorganic interface. 50 The D50 of the small particle electrolyte is too small to affect dispersion of the inorganic electrolyte, and thus, the D50 of only the large particle electrolyte and the small particle electrolyte 50 Only within the parameter range of the present application is it beneficial to improve ionic conductivity.

[0033] In preferred embodiments of the present application, the first polymer electrolyte is 10-30% by mass, the small particle halide solid electrolyte is 10-60% by mass, and the remainder is the large particle halide solid electrolyte in the first layer solid electrolyte.

[0034] Alternatively, the first polymer electrolyte is 30% by mass, the small particle halide solid electrolyte is 10% by mass, and the remainder is the large particle halide solid electrolyte; or the first polymer electrolyte is 30% by mass, the small particle halide solid electrolyte is 20% by mass, and the remainder is the large particle halide solid electrolyte; or the first polymer electrolyte is 30% by mass, the small particle halide solid electrolyte is 30% by mass, and the remainder is the large particle halide solid electrolyte; or the first polymer electrolyte is 30% by mass, the small particle halide solid electrolyte is 40% by mass, and the remainder is the large particle halide solid electrolyte; or the first polymer electrolyte is 30% by mass, the small particle halide solid electrolyte is 50% by mass, and the remainder is the large particle halide solid electrolyte; or the first polymer electrolyte is 30% by mass, the small particle halide solid electrolyte is 60% by mass, and the remainder is the large particle halide solid electrolyte in the first layer solid electrolyte.

[0035] In a preferred embodiment of the present application, in the second layer of solid-state electrolyte, the second polymer electrolyte is 10-30% by mass, the large-particle sulfide solid-state electrolyte is 10-60% by mass, and the balance is the small-particle sulfide solid-state electrolyte.

[0036] Optionally, in the second layer of solid-state electrolyte, the second polymer electrolyte is 30% by mass, the large-particle sulfide solid-state electrolyte is 10% by mass, and the balance is the small-particle sulfide solid-state electrolyte; or the second polymer electrolyte is 30% by mass, the large-particle sulfide solid-state electrolyte is 20% by mass, and the balance is the small-particle sulfide solid-state electrolyte; or the second polymer electrolyte is 30% by mass, the large-particle sulfide solid-state electrolyte is 30% by mass, and the balance is the small-particle sulfide solid-state electrolyte; or the second polymer electrolyte is 30% by mass, the large-particle sulfide solid-state electrolyte is 40% by mass, and the balance is the small-particle sulfide solid-state electrolyte; or the second polymer electrolyte is 30% by mass, the large-particle sulfide solid-state electrolyte is 50% by mass, and the balance is the small-particle sulfide solid-state electrolyte; or the second polymer electrolyte is 30% by mass, the large-particle sulfide solid-state electrolyte is 60% by mass, and the balance is the small-particle sulfide solid-state electrolyte.

[0037] The ratio of the large-particle inorganic electrolyte and the small-particle inorganic electrolyte in the present application affects the ionic conductivity and the rate performance. Too much large-particle inorganic electrolyte or too little small-particle inorganic electrolyte will reduce the ionic conductivity and the rate performance.

[0038] In a preferred embodiment of the present application, the halide solid-state electrolyte is selected from at least one of Li3YCl6, Li3InCl6, Li3ScCl6, Li3YBr6, Li2ZrCl6, and Li3ErCl6. Understandably, the large-particle halide solid-state electrolyte and the small-particle halide solid-state electrolyte are of the same or different categories.

[0039] In a preferred embodiment of the present application, the first polymer electrolyte is PVDF-HFP (Polyvinylidene fluoride-hexafluoropropylene copolymer) and / or PAN (Polyacrylonitrile); the molecular weight of the PAN is 150-250 thousand (preferably 150 thousand). Notably, the high-potential resistance of PAN and PVDF-HFP in the polymer, the contact with the positive electrode is not easy to decompose, no side reactions occur, and the electrochemical window is large.

[0040] In a preferred embodiment of the present application, the sulfide solid-state electrolyte is selected from Li6PS5Cl, Li6PS5Br, Li7P3S 11 , Li 10 GeP2S12 and Li 3.25 Ge 0.25 P 0.75 at least one of S4. Understandably, the large-particle sulfide solid electrolyte is the same or different from the small-particle sulfide solid electrolyte.

[0041] In the preferred embodiment of the present application, the second polymer electrolyte is selected from at least one of PEO (Polyethylene oxide / Polyethylene glycol), PVA (Polyvinyl Alcohol), PAA (Polyacrylic acid) and PMMA (Poly(methyl methacrylate); the molecular weight of the PEO is 200-300 thousand; the molecular weight of the PVA is 200-300 thousand. It is worth noting that PEO, PVA and PAA, PMMA in the polymer do not easily decompose and do not have side reactions when in contact with the negative electrode. Among them, PVA has high lithium metal affinity, can promote uniform lithium deposition through the C=O group, and improve the cycle performance.

[0042] The molecular weight of the PVA is 200-300 thousand, the molecular weight of the PVA is high, the water solubility is reduced, and it is more effective to block water, gas and the like, effectively isolating the sulfide electrolyte from water and air, and improving the ionic conductivity and electrochemical performance.

[0043] In the preferred embodiment of the present application, the thickness of the first layer of solid electrolyte is 10-100 μm; the thickness of the second layer of solid electrolyte is 10-100 μm.

[0044] Alternatively, the thickness of the first layer of solid electrolyte is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any value between the two. The thickness of the second layer of solid electrolyte is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any value between the two.

[0045] In the preferred embodiment of the present application, the first layer of solid electrolyte and / or the second layer of solid electrolyte further comprises a lithium salt. The mass ratio of the lithium salt to the first polymer electrolyte is 0.01-0.3:1; the mass ratio of the lithium salt to the second polymer electrolyte is 0.01-0.3:1.

[0046] In a preferred embodiment of the present application, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrachloroaluminate, lithium iodide, lithium bromide, lithium thiocyanate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium tetraphenylborate, lithium bis(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium nitrate, lithium hexafluoroarsenate, lithium triflate and lithium bisfluorosulfonylimide.

[0047] The lithium salt in the application cooperates with the polymer solid electrolyte, which can effectively prevent the problem of ion conductivity reduction caused by adding the polymer solid electrolyte in the halide solid electrolyte or sulfide solid electrolyte.

[0048] The preparation method of the solid electrolyte in the present application is not particularly limited, and conventional technical means of those skilled in the art can be selected, for example:

[0049] S1. The large-particle halide solid electrolyte, small-particle halide solid electrolyte and first polymer electrolyte are weighed according to the proportion, respectively, the first polymer electrolyte is dissolved in an organic solvent to prepare a first polymer electrolyte solution, the large-particle halide solid electrolyte and small-particle halide solid electrolyte are added to the organic solvent to prepare a halide solid electrolyte slurry, then the halide solid electrolyte slurry and the first polymer electrolyte solution are mixed, stirred and ultrasonically dispersed, and then cast into a polytetrafluoroethylene mold, followed by drying at a temperature of 60℃ for 5h to obtain a first layer of solid electrolyte.

[0050] S2. The large-particle sulfide solid electrolyte, small-particle sulfide solid electrolyte and second polymer electrolyte are weighed according to the proportion, respectively, the second polymer electrolyte is dissolved in an organic solvent to prepare a second polymer electrolyte solution, the large-particle sulfide solid electrolyte and small-particle sulfide solid electrolyte are added to the organic solvent to prepare a sulfide solid electrolyte slurry, then the sulfide solid electrolyte slurry and the second polymer electrolyte solution are mixed, stirred and ultrasonically dispersed, and then cast into a polytetrafluoroethylene mold, followed by drying at a temperature of 60℃ for 5h to obtain a second layer of solid electrolyte.

[0051] S3. The first layer of solid electrolyte and the second layer of solid electrolyte are taken out of the mold and laminated at 60℃ and 3MPa to obtain a double-layer solid electrolyte.

[0052] The second aspect of the present application provides a solid-state battery, comprising a positive electrode sheet, a negative electrode sheet and the double-layer solid electrolyte described above; wherein the positive electrode sheet is arranged in contact with the first layer of solid electrolyte; and the negative electrode sheet is arranged in contact with the second layer of solid electrolyte.

[0053] The affinity and stability between the inorganic electrolyte filler used in the composite electrolyte and the electrode are different. Compared with halide electrolyte and sulfide electrolyte, the oxide electrolyte is rigid, brittle, has large impedance at the interface between the electrode and the electrolyte, and has the lowest ionic conductivity. The halide electrolyte has good affinity with the oxide positive electrode material, has an electrochemical window of about 5V, does not have a side reaction with the positive electrode material at the interface, and is suitable for contact with the positive electrode; the sulfide electrolyte is stable to lithium, has good flexibility, and has good compatibility with the negative electrode, and is suitable for contact with the negative electrode; therefore, the positive electrode side is in contact with the composite electrolyte layer filled with halide electrolyte, and the negative electrode side is in contact with the composite electrolyte layer filled with sulfide electrolyte.

[0054] By setting different components and different particle sizes of the double-layer electrolyte, the contact between the electrolyte material and the electrode interface is optimized, and the ionic conductivity, cycle performance and rate performance are improved.

[0055] In some embodiments of the present application, the positive electrode sheet comprises a positive electrode active material, a large particle halide solid-state electrolyte, a small particle halide solid-state electrolyte, a first polymer electrolyte and a conductive agent; the negative electrode sheet comprises a negative electrode active material, a large particle sulfide solid-state electrolyte, a small particle sulfide solid-state electrolyte, a second polymer electrolyte and a conductive agent.

[0056] In some embodiments of the present application, the positive electrode active material comprises a ternary positive electrode material, a polyanion positive electrode material, a sodium battery layered oxide, a lithium-rich manganese-based material, prussian blue and its derivatives, or sulfur and its derivatives. The present application does not make specific limitations on this.

[0057] In the present application, the ternary positive electrode material has a chemical formula of Li a M b O2, 0.8≤a≤1.2, 0.9≤b≤1.1, M is selected from one or more of Ni, Mn, Co, Fe, Ti, Cu, Zn, Sn, Mg, Ca, Sr, V, Y, La, Ba, W, Bi, Al, Ce, Si.

[0058] The chemical formula of the polyanion positive electrode material is A x B y C z O n , 0.9≤x≤1.1, 0.9≤y≤1.1, 0≤z≤3, 3≤n≤8, A is selected from one or more of Li, Na, K, B is selected from one or more of Fe, Mn, Ti, V, Ni, Co, Cu, Zn, Mg, Ca, Al, and C is selected from one or more of Si, P, S.

[0059] The chemical formula of the sodium battery layered oxide is Na x D yO2, 0.6≤x≤1.1, 0.9≤y≤1.1, D is selected from one or more of Ni, Mn, Fe, Ti, Cu, Zn, Co, Sn, Mg, Ca, Sr, V, Y, La, Ba, W, Bi, Al, Ce, Si.

[0060] The chemical formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiNO2, wherein 0

[0061] The conductive agent includes super-p, carbon black, graphene, carbon nanotubes, acetylene black, ketjen black, and activated carbon, without specific limitation.

[0062] In some embodiments of the present application, the negative active material includes lithium sheet, graphite, silicon, silicon oxide, tin-based alloy, lithium titanate, hard carbon, or soft carbon, without specific limitation.

[0063] Unless otherwise specified, the technical solutions of the present application are conventional solutions in the art, and the reagents or raw materials used are purchased from commercial channels or are already disclosed.

[0064] In order to better understand the present application, the content of the present application will be further illustrated below in combination with examples, but the content of the present application is not limited to the following examples only. The raw materials and reagents involved in the following examples and comparative examples are all purchased from the market.

[0065] Example 1

[0066] The present embodiment provides a double-layer solid-state electrolyte, and the preparation steps are as follows:

[0067] S1, according to the mass ratio of 30%, 40% and 30% respectively, PAN (molecular weight is 150,000), large particle Li3ScCl6 (D 50 is 1.5 μm) and small particle Li3ScCl6 (D 50 is 0.5 μm) are weighed, PAN is dissolved in N,N-dimethylformamide to prepare a PAN solution, large particle Li3ScCl6 and small particle Li3ScCl6 are added to N,N-dimethylformamide to prepare a Li3ScCl6 slurry, the solid content of the slurry is controlled at 60 wt%, then the Li3ScCl6 slurry is mixed with the PAN solution, after stirring and ultrasonic dispersion, it is cast into a polytetrafluoroethylene mold, then dried at a temperature of 60°C in a vacuum device for 5 h, to obtain a first layer of solid-state electrolyte, the thickness of the first layer of solid-state electrolyte is 100 μm.

[0068] S2, according to the mass ratio of 30%, 40% and 30% respectively, PVA (molecular weight is 300,000), large particle Li6PS5Cl (D 501.5 pm) and small particle Li6PS5Cl (D 50 0.5 pm), the PVA was dissolved in acetonitrile to prepare a PVA solution, the large particle Li6PS5Cl and the small particle Li6PS5Cl were added to acetonitrile to prepare a Li6PS5Cl slurry, the solid content of the slurry was controlled at 60 wt%, then the Li6PS5Cl slurry was mixed with the PVA solution, after stirring and ultrasonic dispersion, it was cast into a polytetrafluoroethylene mold, then dried at a temperature of 60 °C for 5 h to obtain a second layer of solid-state electrolyte, the thickness of the second layer of solid-state electrolyte was 100 pm.

[0069] S3, the first layer of solid-state electrolyte and the second layer of solid-state electrolyte were taken out of the mold and laminated at 60 °C and 3 MPa to obtain a double-layer solid-state electrolyte.

[0070] Example 2

[0071] The difference from Example 1 is only that the D 50 1.2 pm of the large particle Li3ScCl6, the D 50 0.3 pm of the small particle Li3ScCl6, the D 50 1.2 pm of the large particle Li6PS5Cl, the D 50 0.3 pm of the small particle Li6PS5Cl, and the other steps and parameters are the same as those of Example 1.

[0072] Example 3

[0073] The difference from Example 1 is only that the D 50 1.0 pm of the large particle Li3ScCl6, the D 50 1.0 pm of the large particle Li6PS5Cl, and the other steps and parameters are the same as those of Example 1.

[0074] Example 4

[0075] The difference from Example 1 is only that the D 50 1.6 pm of the large particle Li3ScCl6, the D 50 0.2 pm of the small particle Li3ScCl6, the D 50 1.6 pm of the large particle Li6PS5Cl, the D 50 0.2 pm of the small particle Li6PS5Cl, and the other steps and parameters are the same as those of Example 1.

[0076] Example 5

[0077] The difference from Example 1 is only that the D 50 1.9 pm of the large particle Li3ScCl6, the D 501.9 μm, and other steps and parameters are the same as in Example 1.

[0078] Example 6

[0079] The difference from Example 1 is only that the D50 of the large particle Li3ScCl6 is 5 μm, and other steps and parameters are the same as in Example 1. 50 3.0 μm, and other steps and parameters are the same as in Example 1. 50 3.0 μm, and other steps and parameters are the same as in Example 1.

[0080] Comparative Example 1

[0081] The difference from Example 1 is only that the D50 of the large particle Li3ScCl6 is 5 μm, and other steps and parameters are the same as in Example 1. 50 5 μm, and other steps and parameters are the same as in Example 1. 50 5 μm, and other steps and parameters are the same as in Example 1.

[0082] Comparative Example 2

[0083] The difference from Example 1 is only that the D50 of the small particle Li3ScCl6 is 0.05 μm, and other steps and parameters are the same as in Example 1. 50 0.05 μm, and other steps and parameters are the same as in Example 1. 50 0.05 μm, and other steps and parameters are the same as in Example 1.

[0084] Example 7

[0085] The difference from Example 1 is only that in S1, PAN, large particle Li3ScCl6 and small particle Li3ScCl6 are weighed according to the mass ratio of 30%, 60% and 10% respectively, and in S2, PVA, large particle Li6PS5Cl and small particle Li6PS5Cl are weighed according to the mass ratio of 30%, 60% and 10% respectively, and other steps and parameters are the same as in Example 1.

[0086] Example 8

[0087] The difference from Example 1 is only that in S1, PAN, large particle Li3ScCl6 and small particle Li3ScCl6 are weighed according to the mass ratio of 30%, 10% and 60% respectively, and in S2, PVA, large particle Li6PS5Cl and small particle Li6PS5Cl are weighed according to the mass ratio of 30%, 10% and 60% respectively, and other steps and parameters are the same as in Example 1.

[0088] Example 9

[0089] The difference from Example 1 is that in S1, PAN, large particle Li3ScCl6 and small particle Li3ScCl6 are weighed according to the mass ratio of 30%, 20% and 50% respectively, and in S2, PVA, large particle Li6PS5Cl and small particle Li6PS5Cl are weighed according to the mass ratio of 30%, 20% and 50% respectively, and other steps and parameters are the same as those in Example 1.

[0090] Example 10

[0091] The difference from Example 1 is that in S2, PVA is replaced by PEO (molecular weight is 300,000), and other steps and parameters are the same as those in Example 1.

[0092] Example 11

[0093] The difference from Example 1 is that in S2, the molecular weight of PVA is 170,000, and other steps and parameters are the same as those in Example 1.

[0094] Example 12

[0095] The difference from Example 1 is that in S2, the molecular weight of PVA is 90,000, and other steps and parameters are the same as those in Example 1.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that in S1, PAN and large particle Li3ScCl6 (D 50 is 1.5 μm) are weighed according to the mass ratio of 30% and 70% respectively, and in S2, PVA and large particle Li6PS5Cl (D 50 is 1.5 μm) are weighed according to the mass ratio of 30% and 70% respectively, and other steps and parameters are the same as those in Example 1.

[0098] Comparative Example 4

[0099] The difference from Example 1 is that in S1, PAN and small particle Li3ScCl6 (D 50 is 0.5 μm) are weighed according to the mass ratio of 30% and 70% respectively, and in S2, PVA and small particle Li6PS5Cl (D 50 is 0.5 μm) are weighed according to the mass ratio of 30% and 70% respectively, and other steps and parameters are the same as those in Example 1.

[0100] Comparative Example 5

[0101] PAN (molecular weight is 150,000), large particle Li3ScCl6 (D 50 is 1.5 μm) and small particle Li3ScCl6 (D 50The PAN was dissolved in N,N-dimethylformamide to prepare a PAN solution, the large particle Li3ScCl6 and the small particle Li3ScCl6 were added to N,N-dimethylformamide to prepare a Li3ScCl6 slurry, the solid content of the slurry was controlled to be 30wt%, then the Li3ScCl6 slurry was mixed with the PAN solution, after stirring and ultrasonic dispersion, it was cast into a polytetrafluoroethylene mold, then dried at a temperature of 60°C for 5h to obtain a solid electrolyte, the thickness of the solid electrolyte was 200μm (i.e., the difference from Example 1 is that the second layer of solid electrolyte is omitted).

[0102] Comparative Example 6

[0103] PVA (molecular weight 300,000), large particle Li6PS5Cl (D 50 = 1.5μm) and small particle Li6PS5Cl (D 50 = 0.5μm) were weighed according to the mass ratio of 30%, 40% and 30% respectively, the PVA was dissolved in acetonitrile to prepare a PVA solution, the large particle Li6PS5Cl and the small particle Li6PS5Cl were added to acetonitrile to prepare a Li6PS5Cl slurry, the solid content of the slurry was controlled to be 30wt%, then the Li6PS5Cl slurry was mixed with the PVA solution, after stirring and ultrasonic dispersion, it was cast into a polytetrafluoroethylene mold, then dried at a temperature of 60°C for 5h to obtain a solid electrolyte, the thickness of the solid electrolyte was 200μm (i.e., the difference from Example 1 is that the first layer of solid electrolyte is omitted).

[0104] Comparative Example 7

[0105] The difference from Example 1 is that in S1, PAN, large particle Li3ScCl6 and small particle Li3ScCl6 were weighed according to the mass ratio of 50%, 25% and 25% respectively, and in S2, PVA, large particle Li6PS5Cl and small particle Li6PS5Cl were weighed according to the mass ratio of 50%, 25% and 25% respectively, and other steps and parameters were the same as those of Example 1.

[0106] Comparative Example 8

[0107] The difference from Example 1 is that in S1, PAN, large particle Li3ScCl6 and small particle Li3ScCl6 were weighed according to the mass ratio of 3%, 50% and 47% respectively, and in S2, PVA, large particle Li6PS5Cl and small particle Li6PS5Cl were weighed according to the mass ratio of 3%, 50% and 47% respectively, and other steps and parameters were the same as those of Example 1.

[0108] Example 13

[0109] The difference from Example 1 is that in S1, PAN, large particle Li3ScCl6 and small particle Li3ScCl6 are weighed according to the mass ratio of 30%, 40% and 30% respectively, and in S2, PVA, large particle Li6PS5Cl and small particle Li6PS5Cl are weighed according to the mass ratio of 30%, 30% and 40% respectively, and other steps and parameters are the same as those in Example 1.

[0110] Effect verification:

[0111] 1. Ionic conductivity:

[0112] The thickness h and area S of the solid-state electrolyte prepared in the above examples and comparative examples are measured. The solid-state electrolyte is sandwiched between two clean and flat stainless steel sheets, and then assembled into a symmetrical battery with a positive electrode cell shell, a negative electrode cell shell and a gasket, wherein the stainless steel sheet is used as a blocking electrode. In order to ensure the contact between the electrolyte and the stainless steel sheet, the solid-state electrolyte and the two stainless steel sheets are laminated at 60°C and 3MPa. The amplitude is set to 10mV, the scanning frequency range is set to 0.1Hz-7MHz, and the AC impedance spectrum at 25°C is tested by using the LAND battery test system. The AC impedance R is read. According to the formula ionic conductivity σ = h / (S*R), the ionic conductivity of the electrolyte film is calculated, and the results are shown in Table 1.

[0113] 2. Cycle performance:

[0114] LiNi 0.8 Co 0.1 Mn 0.1 O2 (commercially available) is mixed with conductive carbon black and binder PVDF (polyvinylidene fluoride) at a ratio of 8:1:1 to form a slurry, which is coated on an aluminum foil to form a positive electrode sheet. A metal lithium sheet is used as a negative electrode sheet. The battery shell, positive and negative electrode sheets, spring, gasket and solid-state electrolyte prepared in the above examples and comparative examples are assembled into a button cell in a vacuum glove box, wherein the positive electrode sheet is in contact with the first layer of solid-state electrolyte containing Li3ScCl6, and the negative electrode sheet is in contact with the second layer of solid-state electrolyte containing Li6PS5Cl.

[0115] The LAND test system is used to perform 1C (specific capacity used for calculating current is 200mAhg -1 ) charge and discharge test at a voltage of 2.75-4.3V, and the capacity retention rate is calculated after 300 cycles. The capacity retention rate after 300 cycles is shown in Table 1.

[0116] 3. Rate performance:

[0117] The battery was assembled by the method in the above cycle performance test, and then placed on a blue electric test system device, and subjected to 0.1C, 0.2C, 0.5C and 1C (the specific capacity for calculating the current was 200 mAh g -1 ) charge-discharge tests at a voltage of 2.75-4.3V in turn, 3 times of charge-discharge cycles were performed at each current density, i.e. 3 times of 0.1C cycle, 3 times of 0.2C cycle, 3 times of 0.5C cycle, 3 times of 1C cycle, and finally the ratio of 1C capacity to 0.1C capacity was calculated, and the results of 1C / 0.1C were shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] It can be seen from Table 1 that:

[0122] It can be seen from the data of the examples and comparative examples that the double-layer solid-state electrolyte prepared in the application is composed of a first layer of solid-state electrolyte and a second layer of solid-state electrolyte; the first layer of solid-state electrolyte is composed of a halide solid-state electrolyte and a first polymer electrolyte; the halide solid-state electrolyte is composed of a large-particle halide solid-state electrolyte and a small-particle halide solid-state electrolyte; the second layer of solid-state electrolyte is composed of a sulfide solid-state electrolyte and a second polymer electrolyte; and the sulfide solid-state electrolyte is composed of a large-particle sulfide solid-state electrolyte and a small-particle sulfide solid-state electrolyte. By setting the double-layer electrolyte with different components and different particle sizes, and simultaneously optimizing the contact between the electrolyte material and the interface between the electrolyte and the electrode, the ionic conductivity, cycle performance and rate performance are improved.

[0123] The above only describes the preferred embodiments of the application, and it should be noted that for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A double-layer solid-state electrolyte, characterized by, consisting of a halide solid-state electrolyte and a first polymer electrolyte; the halide solid-state electrolyte consisting of a large-particle halide solid-state electrolyte and a small-particle halide solid-state electrolyte, wherein the large-particle halide solid-state electrolyte has an average particle diameter of 1.0 μm ≤ D 50 ≤ 3.0 μm, and the small-particle halide solid-state electrolyte has an average particle diameter of 0.1 μm ≤ D 50 ≤ 0.5 μm; The second layer solid-state electrolyte consists of a sulfide solid-state electrolyte and a second polymer electrolyte; the sulfide solid-state electrolyte consists of a large-particle sulfide solid-state electrolyte and a small-particle sulfide solid-state electrolyte, wherein the average particle size of the large-particle sulfide solid-state electrolyte is 1.0 μm≤D 50 ≤3.0 μm, and the average particle size of the small-particle sulfide solid-state electrolyte is 0.1 μm≤D 50 ≤0.5 μm.

2. The dual-layer solid-state electrolyte of claim 1, wherein, The first polymer electrolyte is 10-30% by mass, the small particle halide solid electrolyte is 10-60% by mass, and the balance is the large particle halide solid electrolyte in the first layer solid electrolyte; The second polymer electrolyte is 10-30% by mass, the large particle sulfide solid electrolyte is 10-60% by mass, and the balance is the small particle sulfide solid electrolyte in the second layer solid electrolyte.

3. The dual-layer solid-state electrolyte of claim 1, wherein, The halide solid electrolyte is selected from at least one of Li3YCl6, Li3InCl6, Li3ScCl6, Li3YBr6, Li2ZrCl6 and Li3ErCl6.

4. The dual-layer solid-state electrolyte of claim 1, wherein, The first polymer electrolyte is PVDF-HFP and / or PAN; the molecular weight of the PAN is 150-250 thousand.

5. The dual-layer solid-state electrolyte of claim 1, wherein, The sulfide solid-state electrolyte is selected from at least one of Li6PS5CI, Li6PS5Br, Li7P3S 11 10 GeP2S 12 and Li 3.25 Ge 0.25 P 0.75 S4.​ 6. The dual-layer solid-state electrolyte of claim 1, wherein, The second polymer electrolyte is selected from at least one of PEO, PVA, PAA and PMMA; the molecular weight of the PEO is 200-300 thousand; the molecular weight of the PVA is 200-300 thousand.

7. The dual-layer solid-state electrolyte of claim 1, wherein, The thickness of the first layer solid electrolyte is 10-100 μm; the thickness of the second layer solid electrolyte is 10-100 μm.

8. A solid state battery, characterized by The double-layer solid electrolyte according to any one of claims 1-7 is provided, and the positive electrode sheet is in contact with the first layer solid electrolyte, and the negative electrode sheet is in contact with the second layer solid electrolyte.

Images