Three-layer solid electrolyte structure

Abstract

The invention discloses a three-layer solid electrolyte structure which comprises two solid electrolyte PPC layers, a lithium salt (Li TFS I) layer and a PEO + Li TFS I + LLZTO layer, and the three coatings are sequentially and uniformly coated on the upper part of an NCM positive electrode. The invention belongs to the technical field of solid-state batteries, and particularly relates to a three-layer solid-state electrolyte structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and in particular relates to a three-layer solid-state electrolyte structure. Background Art

[0002] As the most critical component of solid-state batteries, SSEs can generally be divided into two categories: inorganic solid electrolytes and solid polymer electrolytes. Inorganic electrolytes include ceramic Li 10 GeP2S 12 、Na3Zr2Si2PO 12 、Li3InC l6 and Li7La3Zr2O 12 , with high ionic conductivity, mechanical strength, and thermal stability. However, ceramic electrolytes have poor interfacial contact due to their brittleness and rigidity, which limits their application in solid-state batteries. In contrast, solid polymer electrolytes composed of a polymer matrix and lithium salts have the advantages of flexibility, light weight, and ease of large-scale production, making them feasible for practical applications. However, solid polymer electrolytes suffer from low ionic conductivity and poor mechanical strength. Therefore, a strategy to develop an attractive approach is proposed, namely, adding ceramic fillers to the polymer matrix to provide the following synergistic effects: (i) increased ionic conductivity, (ii) electrochemical working platform, and (iii) enhanced mechanical strength of the resulting composite solid electrolyte.

[0003] Pioneering research is devoted to the manufacture of composite solid electrolytes to improve the cycling stability of solid-state batteries, such as poly(ethylene oxide) (PEO) + LLZTO, poly(vinylidene fluoride-co-hexafluoropropylene) + Li 1.5 Al 0.5 Ti 1.5 (PO4)3(LATP), and poly(propylene carbonate) (Polypropylenecarbonate, PPC) + mesoporous silica nanoparticles, although great progress has been made in ionic conductivity, the lithium dendrite problem and the easy penetration of this "ceramic polymer" electrolyte will cause solid-state batteries to short-circuit, seriously limiting their practical applications. Summary of the invention

[0004] The technical problem to be solved by the present invention is the existing equipment.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a three-layer solid electrolyte structure, including two solid electrolyte PPC layers, a lithium salt (LiTFSI) layer and a PEO+LiTFSI+LLZTO layer.

[0006] Furthermore, the above three coating layers are uniformly coated on the upper part of the NCM positive electrode in sequence.

[0007] Furthermore, the two solid electrolyte PPC layers are a layer of PPC (50wt%) and LITFSI (50wt%) polymer electrolyte.

[0008] Furthermore, the lithium salt (LiTFSI) layer is prepared by uniformly mixing PEO (40 wt%) and LITFSI (40 wt%) and then adding LATP (20 wt%).

[0009] Furthermore, the PEO+LiTFSI+LLZTO layer is a layer of PEO (50 wt %) and LITFSI (50 wt %) polymer electrolyte.

[0010] Furthermore, the above three coating combinations are as follows:

[0011] 1) (PPC + LiTFSI): 0.5 g PPC and 0.5 g LiTFSI were dissolved in 10 mL ACN and stirred vigorously at 30 °C for 6 h. The prepared PPC + LiTFSI slurry was used as slurry;

[0012] 2) (PEO+LiTFSI+LATP): PEO (40 wt%) and LITFSI (40 wt%) were mixed and then LATP (20 wt%) was added. Then it was added to ACN and stirred at 50 °C for 6 hours to obtain a uniform electrolyte slurry;

[0013] 3) (PEO+LiTFSI): 0.5 g PEO and 0.5 g LiTFSI were dissolved in 10 mL ACN and stirred vigorously at 30° C. for 6 h. The prepared PEO+LiTFSI slurry was used as slurry.

[0014] Furthermore, each coating process was heated to 140° C. and placed in a vacuum oven overnight.

[0015] Furthermore, the thickness of each composite layer is precisely controlled by a scraper.

[0016] After adopting the above structure, the beneficial effects of the present invention are as follows: the applicability of the composite solid electrolyte on the NCM positive electrode and lithium negative electrode side is conducive to the design of high-performance solid-state batteries, and the composite solid electrolyte with cathode and anode and its effectiveness in inhibiting the growth of lithium dendrites confirm the robust battery structure, which can achieve high energy density and stable cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0018] Figure 1 Schematic diagram of Sample C and D proposed by the present invention maintaining 94.6% and 96.9% of charge and discharge after 200 cycles, compared with the control group A and B samples;

[0019] Figure 2 The three-layer design proposed by the present invention

[0020] Schematic diagram of composite solid electrolytes that can inhibit the growth of lithium gold dendrites;

[0021] Figure 3 A schematic diagram showing that the three-layer composite solid electrolyte proposed in the present invention can improve ion conductivity;

[0022] Figure 4 This is a schematic diagram of the ceramic / polymer electrolyte interface and electrode contact proposed by the present invention, which can reduce the contact impedance due to the implantation of A and C layers. DETAILED DESCRIPTION

[0023] like Figure 1 As shown, a three-layer solid electrolyte structure includes two solid electrolyte PPC layers, a lithium salt (LiTFSI) layer and a PEO+LiTFSI+LLZTO layer.

[0024] like Figure 2-3 -4, wherein the above three layers of coating are uniformly coated on the upper part of the NCM positive electrode in sequence, the two solid electrolyte PPC layers are a layer of PPC (50wt%) and LITFSI (50wt%) polymer electrolytes, the lithium salt (LiTFSI) layer is a layer of PEO (40wt%) and LITFSI (40wt%) mixed evenly and then LATP (20wt%) is added, and the PEO+LiTFSI+LLZTO layer is a layer of PEO (50wt%) and LITFSI (50wt%) polymer electrolytes.

[0025] The above three coating combinations are as follows:

[0026] 1) (PPC + LiTFSI): 0.5 g PPC and 0.5 g LiTFSI were dissolved in 10 mL ACN and stirred vigorously at 30 °C for 6 h. The prepared PPC + LiTFSI slurry was used as slurry;

[0027] 2) (PEO+LiTFSI+LATP): PEO (40 wt%) and LITFSI (40 wt%) were mixed and then LATP (20 wt%) was added. Then it was added to ACN and stirred at 50 °C for 6 hours to obtain a uniform electrolyte slurry;

[0028] 3) (PEO+LiTFSI): 0.5 g PEO and 0.5 g LiTFSI were dissolved in 10 mL ACN and stirred vigorously at 30° C. for 6 h. The prepared PEO+LiTFSI slurry was used as slurry.

[0029] Each coating process is heated to 140°C and placed in a vacuum oven overnight, and the thickness of each composite layer is precisely controlled by a scraper.

[0030] In addition, the leakage flammability and safety issues with traditional liquid electrolytes can be solved by using SSEs, which have been shown to be non-flammable and mechanically strong enough to block lithium dendrites generated by charge and discharge cycles. Despite these excellent intrinsic properties, SSEs still need to meet the requirements of solid-state battery electrochemical performance: (i) ionic conductivity greater than 10 at room temperature; -4 S

[0031] cm -2 , (ii) Stable and robust interface between SSEs and electrodes to achieve smooth Li + transport properties, and (iii) high mechanical strength and flexibility to inhibit lithium dendrite growth and easy to handle. In this context, solid electrolytes are driven to have high electrochemical and mechanical stability, as well as interfaces compatible with high-voltage cathodes and lithium anodes.

[0032] It can be seen that the selection of SSEs type and the formulation of appropriate content become key factors affecting the performance of solid-state batteries.

[0033] Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents. In short, if those skilled in the art are inspired by them and design structural modes and embodiments similar to the technical solution without creativity without departing from the purpose of the present invention, they shall all fall within the scope of protection of the present invention.

Claims

1. Three-layer solid electrolyte structure, characterized by: It includes a three-layer setup of two solid electrolyte PPC layers, a lithium salt (LiTFSI) layer and a PEO+LiTFSI+LLZTO layer.

2. The three-layer solid electrolyte structure according to claim 1, characterized in that: The above three coating layers are uniformly coated on the upper part of the NCM positive electrode in sequence.

3. The three-layer solid electrolyte structure according to claim 2, characterized in that: The two solid electrolyte PPC layers are a layer of PPC (50 wt %) and LITFSI (50 wt %) polymer electrolyte.

4. The three-layer solid electrolyte structure according to claim 3, characterized in that: The lithium salt (LiTFSI) layer is prepared by uniformly mixing PEO (40 wt%) and LITFSI (40 wt%) and then adding LATP (20 wt%).

5. The three-layer solid electrolyte structure according to claim 4, characterized in that: The PEO+LiTFSI+LLZTO layer is a layer of PEO (50 wt %) and LITFSI (50 wt %) polymer electrolyte.

6. The three-layer solid electrolyte structure according to claim 5, characterized in that: The above three coating combinations are as follows: 1) (PPC + LiTFSI): 0.5 g PPC and 0.5 g LiTFSI were dissolved in 10 mL ACN and stirred vigorously at 30 °C for 6 h. The prepared PPC + LiTFSI slurry was used as slurry; 2) (PEO+LiTFSI+LATP): PEO (40 wt%) and LITFSI (40 wt%) were mixed and then LATP (20 wt%) was added. Then it was added to ACN and stirred at 50 °C for 6 hours to obtain a uniform electrolyte slurry; 3) (PEO+LiTFSI): 0.5 g PEO and 0.5 g LiTFSI were dissolved in 10 mL ACN and stirred vigorously at 30° C. for 6 h. The prepared PEO+LiTFSI slurry was used as slurry.

7. The three-layer solid electrolyte structure according to claim 6, characterized in that: Each coating process was heated to 140°C and placed in a vacuum oven overnight.

8. The three-layer solid electrolyte structure according to claim 7, characterized in that: The thickness of each composite layer is precisely controlled by a scraper.

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