Preparation method of double-layer ultra-thin electrolyte film of all-solid-state battery based on transfer printing technology

Abstract

The present application relates to a kind of preparation method of full solid battery double-layer ultrathin electrolyte film based on transfer printing technology.The present application utilizes the high voltage stability of halide layer and the high ionic conductivity of sulfide layer to synergistically improve the cycle life and high rate performance of battery and other performances through halide / sulfide double-layer electrolyte design.Further, the transfer printing process of multi-layer electrolyte film is designed specifically, and the gradient drying process can avoid substrate deformation, effectively prevent halide / sulfide interlayer cracking, and enhance the interlayer adhesion, achieving electrode thinning, high mechanical strength and interface stability.The present application solves the technical bottleneck of the application difficulty of double-layer electrolyte structure in full solid battery through material system optimization and transfer printing process innovation, and is suitable for the industrial production of high energy density solid state battery.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology and relates to a method for preparing a double-layer ultrathin electrolyte membrane for all-solid-state batteries based on transfer technology. Background Technology

[0002] All-solid-state batteries replace traditional liquid electrolytes and separators with solid electrolyte membranes, and their core lies in the ion transport and interfacial stability of the electrolyte membrane. However, current all-solid-state battery electrolyte membrane fabrication technologies face the following problems: 1. Difficulty in balancing material cost and performance: While halide electrolytes are low-cost and have good affinity with the positive electrode, their interfacial stability with the negative electrode is insufficient when used alone; sulfide electrolytes exhibit excellent performance at the negative electrode interface, but they are more expensive and prone to side reactions with the positive electrode material. 2. Poor process compatibility: Existing transfer technologies are mostly designed for single-layer materials and cannot achieve precise composite and transfer of multi-layer electrolytes, failing to meet the requirements of all-solid-state batteries for two types of electrolyte membranes.

[0003] For the composite of multilayer electrolytes, most methods still employ traditional coating techniques (such as slurry casting and lamination). However, traditional coating techniques involve directly coating the surface of the negative or positive electrode. Multilayer coating is prone to electrode peeling or cracking due to immersion, and it is also difficult to achieve a smooth coating and control the thickness. Therefore, there is an urgent need to develop a novel transfer method for the composite and transfer of multilayer electrolyte membranes, while simultaneously preparing all-solid-state battery electrolyte membranes that balance material cost and performance with good process compatibility. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of existing technologies and provide a method for preparing a double-layer ultrathin electrolyte membrane for all-solid-state batteries based on transfer technology. Firstly, this invention designs a halide / sulfide double-layer electrolyte, allowing it to contact the positive and negative electrodes separately, synergistically improving battery cycle life and high-rate performance. Secondly, a novel transfer process is developed for the multilayer electrolyte membrane. Utilizing a gradient drying process avoids substrate deformation, effectively prevents cracking between halide / sulfide layers, and enhances interlayer bonding, achieving ultrathin electrode sheets, high mechanical strength, and interface stability, thereby contributing to improved battery cycle life, high-rate performance, and high-temperature performance.

[0005] The objective of this invention can be achieved through the following methods:

[0006] In a first aspect, the present invention provides a method for preparing a double-layer ultrathin electrolyte membrane for an all-solid-state battery based on transfer technology, comprising the following steps:

[0007] S1. Dissolve the halide electrolyte and sulfide electrolyte with the binder in an organic solvent to obtain halide electrolyte slurry and sulfide electrolyte slurry, respectively;

[0008] S2. Apply a halide electrolyte slurry to the surface of the substrate and dry it to form a halide electrolyte layer;

[0009] S3. Apply sulfide electrolyte slurry to the surface of the halide electrolyte layer and dry it to form a sulfide electrolyte layer, thus obtaining a substrate / electrolyte laminate.

[0010] S4. Align the negative electrode sheet with the substrate / electrolyte stack, and roll-press to obtain the negative electrode sheet of the composite double-layer ultrathin electrolyte membrane.

[0011] In one embodiment of the present invention, in step S1, the halide electrolyte includes one or more of Li3InCl6, Li3YCl6, Li4YI7, Li-Sc-Cl, and Li-Ho-Cl; the sulfide electrolyte includes Li6PS5X, Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li7P3S 11 One or more of the following; where X = Cl, Br, I.

[0012] In one embodiment of the present invention, in step S1, the D50 of the halide electrolyte is 3-20 μm; and the D50 of the sulfide electrolyte is 2-20 μm.

[0013] As one embodiment of the present invention, in step S1, the organic solvent includes one or more of toluene, xylene, and dibutyl ether; the binder includes one or more of polyisobutylene (PIB) and styrene-butadiene rubber (BR).

[0014] In one embodiment of the present invention, in step S1, the amount of organic solvent added is 30%-50% of the weight of the electrolyte; the amount of binder added is 1%-5% of the weight of the electrolyte.

[0015] As one embodiment of the present invention, in step S1, the halide electrolyte slurry or sulfide electrolyte slurry is formed by ball milling or high-speed shear dispersion.

[0016] In one embodiment of the present invention, in step S2, the substrate includes PET.

[0017] In one embodiment of the present invention, in step S2, the coating thickness is controlled to be 30-50 μm. The coating method of the present invention is a slot coating method.

[0018] In one embodiment of the present invention, in step S2, the drying temperature is 80±5℃, the time is 3-4 hours, and the drying is carried out until the halide electrolyte layer is 8-15μm.

[0019] In one embodiment of the present invention, in step S3, the coating thickness is controlled to be 30-60 μm.

[0020] In one embodiment of the present invention, in step S3, the drying temperature is 120±5℃, the time is 1-2 hours, and the drying is carried out until the sulfide electrolyte layer is 10-20μm thick. High-temperature drying allows the solvent to evaporate quickly, preventing electrode delamination or microcracks.

[0021] The gradient drying in this invention includes drying in steps S2 and S3. If the drying temperature is too low or too high, problems such as incomplete drying and microcracks in the electrode sheet may occur.

[0022] In one embodiment of the present invention, in step S4, the pressure of the roller pressing is 10-50 MPa, and the temperature is 20-80°C. During this process, the sulfide layer forms a close contact with the negative electrode surface, ultimately achieving a complete transfer of the electrolyte double-layer structure from the PET substrate to the negative electrode, with a transfer rate ≥98%.

[0023] Secondly, the present invention provides a double-layer ultrathin electrolyte membrane for all-solid-state batteries obtained by the preparation method described above.

[0024] Thirdly, the present invention provides an application of the aforementioned all-solid-state battery double-layer ultrathin electrolyte membrane in the preparation of all-solid-state battery cells.

[0025] As one embodiment of the present invention, the preparation process of the all-solid-state battery cell includes: stacking, welding and encapsulating the negative electrode sheet of the composite all-solid-state battery double-layer ultrathin electrolyte membrane and the (NCM) positive electrode sheet to obtain the cell.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention utilizes a halide / sulfide bilayer electrolyte design, taking advantage of the high voltage stability of the halide layer and the high ionic conductivity (>1×10⁻⁶) of the sulfide layer. -3 The S / cm ratio synergistically improves battery cycle life and high-rate performance; among them, the halide electrolyte membrane has a more stable interface with the positive electrode, which can improve battery cycle life and other performance while reducing battery cost; the sulfide electrolyte membrane has excellent interface performance with the negative electrode, which can reduce interface resistance (initial interface resistance < 8Ω·cm). 2 This improves the battery's high-rate performance and other properties.

[0028] 2. This invention reveals that traditional transfer printing technology is only suitable for the preparation and transfer of single-layer electrolyte membranes. When dealing with the composite and transfer of multi-layer electrolyte membranes, traditional coating technology is still mostly used, but this technology suffers from defects such as electrode peeling or cracking. This invention specifically designs a transfer printing process for multi-layer electrolyte membranes. Utilizing a gradient drying process, it can avoid substrate deformation, effectively prevent halide / sulfide interlayer cracking, and enhance interlayer adhesion. Specifically, the low-temperature long-time treatment in the initial drying stage avoids solvent retention, and the secondary high-temperature treatment ensures rapid solvent evaporation, preventing electrode delamination or microcracks. This achieves ultra-thin electrodes, high mechanical strength, and interface stability, thereby improving battery cycle life, high-rate performance, and high-temperature performance.

[0029] 3. This invention solves the technical bottleneck of the difficulty in applying the double-layer electrolyte structure in all-solid-state batteries through material system optimization and transfer process innovation, and is suitable for the industrial production of high-energy-density solid-state batteries. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 This is a flowchart illustrating the preparation process of the double-layer ultrathin electrolyte membrane for the all-solid-state battery of this invention.

[0032] Figure 2 SEM image of the electrode prepared in Example 1;

[0033] Figure 3 The results show the cycle performance of the battery cell prepared in Example 2;

[0034] Figure 4 The results show the cycle performance of the battery cell prepared in Comparative Example 1;

[0035] Figure 5 SEM image of the electrode prepared in Comparative Example 3;

[0036] Figure 6 The image shows a SEM image of the electrode prepared in Comparative Example 4. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0038] This invention provides a method for preparing a double-layer ultrathin electrolyte membrane for an all-solid-state battery based on transfer technology and for assembling the battery cell. The process is as follows: Figure 1 .

[0039] Example 1: Electrode Preparation

[0040] 1. Slurry preparation:

[0041] Halide slurry: Li3InCl6 powder (D50 = 5 μm) is ball-milled with xylene solvent (40% by weight of powder) and PIB binder (3% by weight of powder);

[0042] Sulfide slurry: Li6PS5Cl powder (D50 = 3μm) is ball-milled with toluene solvent (35% by weight of powder) and BR binder (2% by weight of powder).

[0043] 2. Coating and drying:

[0044] A halide layer (wet film thickness 30 μm) was coated on a 12 μm PET substrate and dried at 80 °C for 3 h to form a dense halide electrolyte layer (thickness 8 μm, porosity <5%).

[0045] A sulfide layer (wet film thickness 40 μm) was coated and dried at 120 °C for 1.5 h to form a sulfide electrolyte layer (thickness 12 μm, ionic conductivity 1.2 × 10⁻⁶). -3 S / cm).

[0046] 3. Roller transfer printing:

[0047] The lithium metal anode is aligned with the PET / electrolyte stack and rolled at 20MPa and 60℃, so that the electrolyte layer is completely transferred to the surface of the anode. The total thickness of the electrode is ≤45μm (traditional wet electrode is >60μm).

[0048] In this embodiment, the electrode thickness is reduced by 25%, the tensile strength reaches 18 MPa (traditional electrodes < 10 MPa), and no cracks are observed during a 180° bending test. Figure 2 As can be seen, this embodiment utilizes a gradient drying process to ensure that the interface of the prepared halide / sulfide bilayer electrolyte membrane is free of microcracks, and the contact area between the sulfide layer and the lithium anode is >95%.

[0049] Example 2: Cell Fabrication

[0050] 1. Electrolyte design:

[0051] The halide layer (Li3InCl6) serves as a buffer layer on the positive electrode side, suppressing interfacial side reactions;

[0052] The sulfide layer (Li6PS5Cl) provides a high ion conduction path (conductivity > 3 × 10⁻⁶). -3S / cm).

[0053] 2. Cell assembly:

[0054] The lithium metal anode transferred in Example 1, the positive electrode material composed of NCM811 and halide (loading 20 mg / cm³) 2 It is laminated with the electrolyte layer, cold-pressed at 50MPa, and packaged as a soft-pack battery cell.

[0055] 2. Performance Testing:

[0056] Cyclic stability: The cycle stability is significantly improved compared to using a sulfide electrolyte composite cathode, such as... Figure 3 It can be seen that after 600 cycles of 1C charge-discharge (2.5-4.3V), the capacity retention rate is 83% (traditional single-layer sulfide cells have a capacity retention rate of <70% after 500 cycles due to unstable positive electrode high voltage).

[0057] Rate performance: 5C discharge capacity reaches 88% of 0.2C discharge capacity (traditional cells <70%);

[0058] High temperature performance: No lithium dendrite growth after 500 cycles at 60℃, and interface impedance increase of <5%;

[0059] 3. Mechanism Analysis:

[0060] The synergistic effect of the two layers: the halide layer blocks the oxidation of the sulfide layer by the positive electrode active material, and the sulfide layer reduces the interfacial impedance (initial interfacial impedance < 8 Ω·cm). 2 This embodiment achieves long cycle life and high rate performance of all-solid-state cells based on dual-layer electrolyte interface optimization and pressure transfer technology.

[0061] 4. Conclusion: Example 1 significantly improved the mechanical properties of the electrode through the ultra-thin multilayer structure design, and Example 2 verified the optimization effect of the bilayer electrolyte on the overall performance of the all-solid-state battery. Both have clear industrial application value.

[0062] Comparative Example 1

[0063] The preparation method of the comparative electrolyte is basically the same as that in Example 1, except that the halide electrolyte layer is omitted, and only the sulfide electrolyte layer is retained. The negative electrode sheet with the obtained composite sulfide electrolyte layer is used to prepare a pouch cell according to Example 2. Figure 4 It can be seen that after 300 cycles of 1C charge-discharge (2.5-4.3V), the capacity retention rate is 82%, indicating that the lack of a halide electrolyte layer will lead to decomposition and instability at the positive electrode interface.

[0064] Comparative Example 2

[0065] The preparation method of the comparative electrolyte is basically the same as that in Example 1, except that the sulfide electrolyte layer is omitted and only the halide electrolyte layer is retained. The negative electrode sheet with the obtained composite halide electrolyte layer was used to prepare a pouch cell according to Example 2. The results show that when the halide electrolyte layer directly contacts the lithium metal negative electrode, the battery will short-circuit and cannot participate in normal cycling.

[0066] Comparative Example 3

[0067] The preparation method of this comparative electrolyte is basically the same as that of Example 1, except that the drying in step 2 is carried out at 120°C for 3 hours. Figure 5 As shown, Comparative Example 3 did not employ a gradient drying process, resulting in noticeable microcracks at the interface of the prepared halide / sulfide bilayer electrolyte membrane, which affected the subsequent battery's cycle life, high-rate performance, and high-temperature performance.

[0068] Comparative Example 4

[0069] The preparation method of the comparative electrolyte is basically the same as that of Example 1, except that the drying in step 3 is carried out at 80°C for 1.5 hours. Figure 6 As shown, Comparative Example 4 did not employ a gradient drying process, resulting in noticeable microcracks at the interface of the prepared halide / sulfide bilayer electrolyte membrane, which affected the subsequent battery's cycle life, high-rate performance, and high-temperature performance.

[0070] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a double-layer ultrathin electrolyte membrane for an all-solid-state battery based on transfer technology, characterized in that, Includes the following steps: S1. Dissolve the halide electrolyte and sulfide electrolyte with the binder in an organic solvent to obtain halide electrolyte slurry and sulfide electrolyte slurry, respectively; The sulfide electrolyte includes Li6PS5X and Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li7P3S 11 One or more of the following; where X = Cl, Br, I; S2. Apply a halide electrolyte slurry to the surface of the substrate and dry it to form a halide electrolyte layer; The drying temperature is 80±5℃, the time is 3-4 hours, and the drying is carried out until the halide electrolyte layer is 8-15μm thick; S3. Apply sulfide electrolyte slurry to the surface of the halide electrolyte layer and dry it to form a sulfide electrolyte layer, thus obtaining a substrate / electrolyte laminate. The drying temperature is 120±5℃, the time is 1-2 hours, and the drying is carried out until the sulfide electrolyte layer is 10-20μm. S4. Align the negative electrode sheet with the substrate / electrolyte stack, and roll-press to obtain the negative electrode sheet of the composite double-layer ultrathin electrolyte membrane.

2. The preparation method according to claim 1, characterized in that, In step S1, the halide electrolyte includes one or more of Li3InCl6, Li3YCl6, Li4YI7, Li-Sc-Cl, and Li-Ho-Cl; The halide electrolyte has a D50 of 3-20 μm; the sulfide electrolyte has a D50 of 2-20 μm.

3. The preparation method according to claim 1, characterized in that, In step S1, the organic solvent includes one or more of toluene, xylene, and dibutyl ether; the binder includes one or more of polyisobutylene and styrene-butadiene rubber. The amount of organic solvent added is 30%-50% of the weight of the electrolyte; the amount of binder added is 1%-5% of the weight of the electrolyte.

4. The preparation method according to claim 1, characterized in that, In step S1, the amount of organic solvent added is 30%-50% of the weight of the electrolyte; the amount of binder added is 1%-5% of the weight of the electrolyte.

5. The preparation method according to claim 1, characterized in that, In step S2, the substrate includes PET.

6. The preparation method according to claim 1, characterized in that, In step S4, the pressure of the roller pressing is 10-50 MPa and the temperature is 20-80℃.

7. A double-layer ultrathin electrolyte membrane for an all-solid-state battery obtained by the preparation method according to any one of claims 1-6.

8. The application of the all-solid-state battery double-layer ultrathin electrolyte membrane as described in claim 7 in the preparation of all-solid-state battery cells, characterized in that, The preparation process of the all-solid-state battery cell includes: stacking, welding, and encapsulating the negative electrode sheet and positive electrode sheet of the composite all-solid-state battery double-layer ultra-thin electrolyte membrane.

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