Solid-state battery and preparation method thereof

Abstract

In order to overcome the problems of insufficient ion conduction efficiency and interface side reaction between the existing sulfide solid electrolyte and a positive electrode, the invention provides a solid-state battery and a preparation method thereof, and the solid-state battery comprises a positive electrode plate and a negative electrode assembly which are stacked in sequence, the positive plate comprises a positive current collector and a positive material layer arranged on the surface of the positive current collector, the negative assembly comprises a negative plate, a sulfide electrolyte layer and a polymer electrolyte layer, the sulfide electrolyte layer is located on the surface of the negative plate, and the polymer electrolyte layer is located on the surface of the sulfide electrolyte layer. A corrugated groove is formed in the surface, deviating from the negative plate, of the sulfide electrolyte layer, the polymer electrolyte layer is located in the corrugated groove, and the polymer electrolyte layer abuts against the positive electrode material layer and partially permeates into the positive electrode material layer.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a solid-state battery and its preparation method. Background Technology

[0002] With the increasing demand for high-safety, high-energy-density batteries from the new energy industry, solid-state batteries, by eliminating the inherent advantages of flammable liquid electrolytes, have become the core development direction for next-generation power batteries. As the core component of solid-state batteries, the performance of the solid electrolyte directly determines the battery's ion transport efficiency, cycle stability, and safety performance. Currently, the mainstream technical routes include three types of electrolyte systems: sulfide, oxide, and polymer.

[0003] Among the three types of solid electrolytes, sulfide solid electrolytes stand out due to their outstanding performance advantages.

[0004] However, the commercialization of sulfide solid-state batteries is still limited by key technological bottlenecks. The low interfacial ion conduction efficiency between the sulfide solid electrolyte and the cathode material results in generally high internal resistance, severely restricting their application in power batteries and other scenarios requiring high-rate charge-discharge. The causes of this core problem mainly lie in the following two aspects: On the one hand, there are physical contact defects at the solid-solid interface. Both sulfide solid electrolytes and positive electrode active materials (such as NCM, LFP, etc.) are solid particles. Even when compounded through pressing processes, they are still prone to forming micron-level interface gaps, resulting in a limited actual effective contact area. Compared to the wetting effect of liquid electrolytes on the electrodes, solid-phase contacts lack an effective interface filling medium, leading to broken lithium-ion transport paths, significantly increased interface impedance, and directly affecting the high-rate charge-discharge performance of the battery.

[0005] On the other hand, to address the aforementioned physical contact issues, existing technologies employ a method of blending sulfide solid electrolytes with cathode materials to prepare composite cathodes, aiming to improve ion conduction efficiency by increasing the contact area between the two phases. However, the actual application results have not met expectations. The fundamental reason is that the electrochemical environment during battery charging and discharging induces interfacial chemical reactions between the sulfide electrolyte and the cathode material. For example, when typical sulfide electrolytes such as Li6PS5Cl come into contact with an NCM cathode, a redox reaction occurs, generating low-ionic-conductivity products such as NiS and Li3PO4. These products form a continuous passivation layer at the interface; and this reaction is persistent. Furthermore, under high-voltage conditions, gaseous byproducts such as SO2 and H2S are generated at the cathode and sulfide interface, further exacerbating the damage to the interfacial structure. These interfacial reactions mean that the blending scheme cannot meet the practical application requirements of power batteries. Summary of the Invention

[0006] To address the problems of insufficient ion conduction efficiency and interfacial side reactions between existing sulfide solid electrolytes and cathodes, this invention provides a solid-state battery and its preparation method.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a solid-state battery, comprising a positive electrode and a negative electrode assembly stacked sequentially. The positive electrode includes a positive current collector and a positive electrode material layer disposed on the surface of the positive current collector. The negative electrode assembly includes a negative electrode, a sulfide electrolyte layer and a polymer electrolyte layer. The sulfide electrolyte layer is located on the surface of the negative electrode and has a corrugated groove disposed away from the surface of the negative electrode. The polymer electrolyte layer is located in the corrugated groove and abuts against and partially penetrates into the positive electrode material layer.

[0008] Optionally, the depth of the corrugated groove is 5μm to 500μm, and the width of the corrugated groove is 10μm to 800μm.

[0009] Optionally, the sulfide electrolyte layer comprises the following components by weight: 92-98 parts of sulfide and 2-8 parts of binder.

[0010] Optionally, the sulfide is selected from Li6PS5Cl, and the sulfide electrolyte layer forms a LiI lithium-rich interface film at the interface of the corrugated groove.

[0011] Optionally, the thickness of the LiI lithium-rich interface film is 1~10μm.

[0012] Optionally, the polymer electrolyte layer includes one or more of polyether polymer electrolytes, polyester polymer electrolytes, and polycarbonate polymer electrolytes.

[0013] Furthermore, the present invention provides a method for preparing a solid-state battery as described above, comprising the following steps: A sulfide solid electrolyte slurry is coated on both sides of the negative electrode sheet, and a corrugated groove is obtained by surface processing. The sulfide electrolyte layer is then dried. A mixture of polymer monomers and lithium salts is coated onto the corrugated groove surface of a sulfide electrolyte layer and pre-cured to form a polymer electrolyte layer, thus obtaining a negative electrode component. The positive electrode slurry is coated onto both sides of the positive electrode current collector and dried to form a positive electrode material layer on both sides of the positive electrode current collector, thus obtaining a positive electrode sheet; The positive electrode and negative electrode components are alternately stacked, and hot pressing is used to allow the polymer electrolyte layer to partially penetrate into the interface of the positive electrode material layer and solidify and form the shape, followed by drying.

[0014] Optionally, the corrugated groove is processed by rolling the sulfide electrolyte layer on both sides of a pressure roller with a corrugated surface to form a corrugated groove on the surface of the sulfide electrolyte layer.

[0015] Optionally, after forming the corrugated groove, a LiI solution is sprayed onto the surface of the corrugated groove of the sulfide electrolyte layer and dried to form a LiI-rich interface film on the surface of the corrugated groove.

[0016] Optionally, the mixed slurry comprises the following components by weight: 42-60 parts of polymer precursor, 16-32 parts of lithium salt, 9-14 parts of curing agent, and 10-20 parts of solvent.

[0017] The solid-state battery provided by this invention utilizes the permeability of a polymer electrolyte layer between the positive electrode material layer and the sulfide electrolyte layer to effectively fill the interfacial gaps between the positive electrode material layer and the sulfide electrolyte layer, thus avoiding lithium-ion conduction problems at the solid-solid interface and effectively improving lithium-ion conduction efficiency. Furthermore, the surface of the sulfide electrolyte layer is designed as a corrugated groove, increasing the ion conduction area between the sulfide electrolyte layer and the polymer electrolyte layer. More importantly, the polymer electrolyte layer prevents direct contact between the sulfide electrolyte layer and the positive electrode material layer, thereby suppressing interfacial side reactions between the sulfide electrolyte layer and the positive electrode material layer and improving the performance of the solid-state battery. While maintaining capacity retention during long-term cycling is important, the relatively thin polymer electrolyte layer inevitably leads to interfacial contact between the cathode material layer and the sulfide electrolyte layer during battery fabrication and lamination. To address this issue, the surface of the sulfide electrolyte layer is designed as a corrugated groove. This corrugated groove structure minimizes the contact area between the cathode material layer and the sulfide electrolyte layer during cell lamination, while retaining sufficient polymer electrolyte layer within the corrugated groove to facilitate interfacial ion conduction. This ultimately suppresses interfacial side reactions, reduces the impedance of the solid-state battery and the impedance growth rate during long-term cycling, and improves its rate discharge performance and lifespan. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the solid-state battery provided by the present invention; Figure 2 This is a schematic diagram of the stacking and lamination of the solid-state battery provided by the present invention.

[0019] The reference numerals in the accompanying drawings are as follows: 1. Negative electrode assembly; 11. Negative electrode sheet; 12. Sulfide electrolyte layer; 121. Corrugated groove; 13. Polymer electrolyte layer; 14. LiI lithium-rich interface film; 2. Positive electrode sheet; 21. Positive electrode current collector; 22. Positive electrode material layer. Detailed Implementation

[0020] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0021] See Figure 1 As shown, an embodiment of the present invention provides a solid-state battery, including a positive electrode 2 and a negative electrode assembly 1 stacked sequentially. The positive electrode 2 includes a positive current collector 21 and a positive electrode material layer 22 disposed on the surface of the positive current collector 21. The negative electrode assembly 1 includes a negative electrode 11, a sulfide electrolyte layer 12 and a polymer electrolyte layer 13. The sulfide electrolyte layer 12 is located on the surface of the negative electrode 11. The sulfide electrolyte layer 12 is provided with a corrugated groove 121 away from the surface of the negative electrode 11. The polymer electrolyte layer 13 is located in the corrugated groove 121, and the polymer electrolyte layer 13 abuts against and partially penetrates into the positive electrode material layer 22.

[0022] According to the solid-state battery provided by the present invention, a polymer electrolyte layer 13 is disposed between the positive electrode material layer 22 and the sulfide electrolyte layer 12. Taking advantage of the permeability of the polymer electrolyte layer 13, it can effectively fill the interfacial gaps between the positive electrode material layer 22 and the sulfide electrolyte layer 12, avoiding lithium-ion conduction problems at the solid-solid interface and effectively improving lithium-ion conduction efficiency. The surface of the sulfide electrolyte layer 12 is configured as a corrugated groove 121, increasing the ion conduction area between the sulfide electrolyte layer 12 and the polymer electrolyte layer 13. More importantly, the polymer electrolyte layer 13 prevents direct contact between the sulfide electrolyte layer 12 and the positive electrode material layer 22, thereby suppressing interfacial side reactions between the sulfide electrolyte layer 12 and the positive electrode material layer 22 and improving the solid-state battery performance. The battery maintains its capacity during long-term cycling. However, although a polymer electrolyte layer 13 is provided, its thickness is relatively low during battery fabrication and lamination. Inevitably, some of the positive electrode material layer 22 will form an interface with the sulfide electrolyte layer 12. To solve this problem, the surface of the sulfide electrolyte layer 12 is designed as a corrugated groove 121. This corrugated groove 121 structure can minimize the contact area between the positive electrode material layer 22 and the sulfide electrolyte layer 12 during cell lamination. At the same time, sufficient polymer electrolyte layer 13 is retained in the corrugated groove 121 to play a role in interfacial ion conduction, thereby ultimately suppressing interfacial side reactions, reducing the impedance of the solid-state battery and the impedance growth rate during long-term cycling, and improving its rate discharge performance and service life.

[0023] It should be noted that in this solid-state battery, the corrugated groove 121 and the polymer electrolyte layer 13 are only disposed on the side of the sulfide electrolyte layer 12 facing the positive electrode. The side of the sulfide electrolyte layer 12 facing the negative electrode still adopts planar contact. This is because during battery cycling, compared with the positive electrode, the negative electrode is more prone to lithium dendrite problems caused by uneven lithium deposition, which leads to problems such as internal short circuit and capacity reduction. The sulfide electrolyte layer 12 has higher mechanical strength than the polymer electrolyte. By making the sulfide electrolyte layer 12 in direct contact with the negative electrode, the formation and growth of lithium dendrites can be effectively suppressed.

[0024] In some embodiments, the depth of the corrugated groove 121 is 5μm to 500μm, and the width of the corrugated groove 121 is 10μm to 800μm.

[0025] If the depth of the corrugated groove 121 is too low, the filling amount of the polymer electrolyte layer 13 will be insufficient, and it will not be able to effectively penetrate the positive electrode material layer 22. Furthermore, the barrier effect on the sulfide electrolyte layer 12 and the positive electrode material layer 22 will be insignificant, leading to interfacial side reactions and resulting in an increase in impedance after long-term cycling. If the depth of the corrugated groove 121 is too high, the mechanical strength of the sulfide electrolyte layer 12 will easily decrease due to the excessive depth of the groove, making it prone to cracking during charge-discharge cycles. It will also increase the total proportion of the polymer electrolyte layer 13, which is not conducive to the full utilization of the high intrinsic ionic conductivity of the sulfide electrolyte layer 12.

[0026] In some embodiments, the cross-sectional shape of the corrugated groove 121 is selected from one of a sine wave, a trapezoidal wave, and a triangular wave. The corrugated grooves 121 are arranged in parallel or staggered arrangements on the surface of the sulfide electrolyte layer 12.

[0027] In some embodiments, the bottom of the corrugated groove 121 is an arc-shaped transition structure to avoid stress concentration at the bottom of the groove causing cracking of the sulfide electrolyte layer 12.

[0028] In some embodiments, the thickness of the polymer electrolyte layer 13 is 10 μm to 500 μm.

[0029] In some embodiments, the sulfide electrolyte layer 12 comprises the following components by weight: 92-98 parts of sulfide and 2-8 parts of binder.

[0030] A 2% to 8% binder can significantly improve the dispersibility and binding force of sulfide particles. If the content of the binder is too low, it will affect the material strength of the sulfide electrolyte layer 12 and the forming ability of the roll-pressed corrugated groove 121. If the content of the binder is too high, it will lead to a relative decrease in the content of sulfide, affecting the ionic conductivity of the sulfide electrolyte layer 12.

[0031] In some embodiments, the adhesive is selected from one or more of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVP), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC).

[0032] In some embodiments, the sulfide is selected from Li6PS5Cl and Li7P3S. 11 Li 6.5 P3S 11.5 Cl 0.5 One or more of Li6PS5Br and Li6PS5I.

[0033] In a preferred embodiment, the sulfide is selected from Li6PS5Cl.

[0034] Compared to other sulfide electrolytes, Li6PS5Cl exhibits superior electrochemical stability. It remains relatively stable even at a high voltage of 4.2V (when adapted to NCM cathodes), reducing the generation of gaseous byproducts such as SO2 and H2S and preventing interfacial structural damage.

[0035] In some embodiments, the sulfide electrolyte layer 12 has a LiI-rich interface film 14 formed at the interface of the corrugated groove 121.

[0036] A lithium-rich LiI interface film 14 is formed at the interface of the corrugated groove 121. On the one hand, the lithium-rich LiI interface film 14 is located between the sulfide electrolyte layer 12 and the polymer electrolyte layer 13, which can increase the lithium ion concentration at the interface, form a lithium ion transport channel, promote the migration of ions at the interface, and reduce the ion transport resistance between the polymer electrolyte layer 13 and the sulfide electrolyte layer 12. On the other hand, the lithium-rich interface film can further block the direct contact between the sulfide electrolyte layer 12 and the positive electrode material layer 22, inhibit the redox reaction, and reduce the generation of low ionic conductivity by-products at the interface of the sulfide electrolyte layer 12.

[0037] In some embodiments, the thickness of the LiI lithium-rich interface film 14 is 1~10 μm.

[0038] If the thickness of the LiI lithium-rich interface film 14 is too low, it will be difficult to improve the interfacial ion conduction efficiency and suppress side reactions; if the thickness of the LiI lithium-rich interface film 14 is too high, it will also be detrimental to the improvement of ion conductivity.

[0039] In some embodiments, the polymer electrolyte layer 13 includes one or more of polyether polymer electrolytes, polyester polymer electrolytes, and polycarbonate polymer electrolytes.

[0040] The polyether polymer electrolyte includes one or more of polyethylene glycol and its derivatives, polyethylene oxide, polypropylene oxide, and polyethylene oxide-polypropylene oxide copolymers.

[0041] The polyester polymer electrolyte includes one or more of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polylactic acid (PLA).

[0042] The polycarbonate polymer electrolyte includes one or more of polypropylene carbonate, polyethylene carbonate (PEC), and polydiphenyl carbonate (BPC).

[0043] In a preferred embodiment, the polymer electrolyte layer 13 is selected from polyether polymer electrolytes, which contain lithium salts.

[0044] In some embodiments, the positive electrode material layer 22 comprises 94% to 98% by mass of positive electrode active material, wherein the positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide (NCM, such as NCM622, NCM711, NCM811), lithium iron phosphate (LFP), and lithium nickel cobalt aluminum oxide (NCA).

[0045] In some embodiments, the positive electrode material layer 22 further includes 1% to 3% by mass of a positive electrode conductive agent and 1% to 3% by mass of a positive electrode binder. The positive electrode conductive agent is selected from one or more of carbon black (CB), Ketjen black (KB), and carbon nanotubes (CNTs), and the positive electrode binder is selected from one or more of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVP), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC).

[0046] In some embodiments, the negative electrode 11 is an integrally formed lithium foil.

[0047] In some embodiments, the negative electrode 11 includes a negative electrode current collector and a negative electrode material layer located on the negative electrode current collector. The negative electrode material layer includes a negative electrode active material with a mass fraction of 94% to 98%, and the negative electrode active material is selected from one or more of graphite, hard carbon, and soft carbon.

[0048] In some embodiments, the negative electrode material layer further includes 1% to 3% by mass of a negative electrode conductive agent and 1% to 3% by mass of a negative electrode binder. The negative electrode conductive agent is selected from one or more of carbon black (CB), Ketjen black (KB), and carbon nanotubes (CNTs), and the negative electrode binder is selected from one or more of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVP), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC).

[0049] Another embodiment of the present invention provides a method for preparing a solid-state battery as described above, comprising the following steps: A sulfide solid electrolyte slurry is coated on both sides of the negative electrode 11, and a corrugated groove 121 is obtained by surface processing. The sulfide electrolyte layer 12 is obtained by drying. A mixture of polymer monomers and lithium salts is coated onto the surface of the corrugated groove 121 of the sulfide electrolyte layer 12 and pre-cured to form the polymer electrolyte layer 13, thus obtaining the negative electrode component 1. The positive electrode slurry is coated onto both sides of the positive electrode current collector 21 and dried to form a positive electrode material layer 22 on both sides of the positive electrode current collector 21, thus obtaining the positive electrode sheet 2. like Figure 2 As shown, the positive electrode 2 and the negative electrode assembly 1 are alternately stacked, and hot pressing is used to allow the polymer electrolyte layer 13 to partially penetrate into the interface of the positive electrode material layer 22 and solidify and form a solid shape, followed by drying.

[0050] By processing the corrugated groove 121 of the sulfide layer → coating the polymer for pre-curing → hot-pressing penetration, a three-layer gradient contact structure of sulfide-polymer-cathode can be precisely realized: the processing of the corrugated groove 121 ensures that the polymer fills the space, the pre-curing prevents the polymer from flowing out, and the hot pressing can promote the polymer to penetrate into the cathode material layer 22, effectively solving the problem of insufficient solid-solid contact area and reducing interfacial resistance. At the same time, the heating effect of hot pressing promotes the further curing and shaping of the polymer electrolyte layer 13, completing the connection between the layers and forming an integrated solid-state battery cell structure.

[0051] In some embodiments, the pre-curing temperature is 50℃~80℃, the pre-curing time is 5min~15min, and the pre-curing atmosphere is an inert gas.

[0052] In some embodiments, the temperature of the hot pressing operation is 80~120°C and the pressure is 5~10MPa.

[0053] In some embodiments, the sulfide solid electrolyte slurry comprises the following components by weight: 95-98 parts of sulfide, 2-5 parts of binder and 10-100 parts of ethylene glycol dimethyl ether.

[0054] In some embodiments, the corrugated groove 121 is processed by rolling the sulfide electrolyte layer 12 on both sides of a pressure roller with a corrugated surface to form a corrugated groove 121 on the surface of the sulfide electrolyte layer 12.

[0055] The rolling process is a continuous process that can be linked with the coating process of the sulfide electrolyte layer 12 (rolling directly after coating). Compared with intermittent processes such as etching and laser processing, it can effectively improve the production speed and is suitable for the roll-to-roll production mode of power battery rolls.

[0056] In some embodiments, the LiI lithium-rich interface film 14 is formed by one or more of spraying, vacuum evaporation, and chemical vapor deposition.

[0057] In a preferred embodiment, after the corrugated groove 121 is formed, a LiI solution is sprayed onto the surface of the corrugated groove 121 of the sulfide electrolyte layer 12 in a protective atmosphere and then dried to form a LiI lithium-rich interface film 14 on the surface of the corrugated groove 121.

[0058] The spraying process can cover the surface of the corrugated groove 121 of the sulfide electrolyte layer 12 (i.e. the contact interface with the polymer electrolyte) with a relatively thin layer of LiI solution, with a film coverage of 100% and the film layer completely adhering to the uneven structure of the corrugated groove 121 without bubbles or voids.

[0059] In some embodiments, the solvent of the LiI solution is selected from ethylene glycol dimethyl ether, and the mass ratio of the solvent to LiI is 6:1 to 9:1.

[0060] In some embodiments, the mixed slurry comprises the following components by weight: 42-60 parts of polymer precursor, 16-32 parts of lithium salt, 9-14 parts of curing agent, and 10-20 parts of solvent.

[0061] In a preferred embodiment, the polymer precursor is selected from polyethylene glycol diglycidyl ether, the lithium salt is selected from lithium bis(trifluorosulfonyl)imide, the curing agent is selected from triethanolamine, and the solvent is selected from ethylene glycol dimethyl ether.

[0062] The present invention will be further illustrated by the following examples.

[0063] Example 1 This embodiment illustrates the solid-state battery and its preparation method disclosed in this invention, and includes the following steps: Step 1: Using a slot coater, the prepared Li6PS5Cl sulfide electrolyte slurry is coated onto the surface of the lithium metal foil, with the coating speed controlled at 3m / min and the thickness at 200μm. Immediately transfer the coated composite structure to a heated roller press, set the roller pressing temperature to 50℃ and the roller pressing pressure to 8MPa, and process the corrugated grooves on the surface of the sulfide electrolyte layer through the corrugated pattern on the surface of the roller: the corrugated grooves are 20μm deep and 100μm wide, and the adjacent corrugated grooves are arranged in parallel with a spacing of 200μm. The structure with the processed corrugated grooves is placed in a vacuum drying oven at a vacuum degree of 5×10⁻⁶. -2 Dry at 80°C for 30 minutes to remove solvent.

[0064] Step 2: Formation of LiI-rich interfacial film A 20% LiI ethanol solution was sprayed onto the corrugated groove surface of the sulfide electrolyte layer using a pneumatic spraying device. The nozzle diameter was set to 0.2 mm, the spraying distance to 8 cm, the spraying speed to 80 mm / s, the thickness of a single spraying was 2 μm, and a total of 2 sprayings were applied (total target film thickness 4 μm). After spraying, the coating is dried in stages: first, it is dried at 60℃ and normal pressure for 8 minutes, and then the temperature is raised to 75℃ and normal pressure for 5 minutes. After drying, a continuous LiI lithium-rich interface film is formed on the surface of the corrugated groove. Step 3: Pre-curing of the polymer electrolyte layer A micro-coating machine is used to uniformly coat the polymer mixture slurry onto the surface of a corrugated groove with a LiI interface film. The mixture slurry comprises the following components by weight: 50 parts polyethylene glycol diglycidyl ether, 22 parts lithium bis(trifluorosulfonyl)imide, 10 parts triethanolamine, and 18 parts ethylene glycol dimethyl ether. Transfer to an inert gas drying oven (introduce high-purity N2, oxygen content ≤10ppm), set the pre-curing temperature to 60℃ and the pre-curing time to 10min, so that the polymer is partially cross-linked to obtain a complete negative electrode component. Step 4: Preparation of the positive electrode sheet A slot coater was used to coat the positive electrode slurry onto both sides of the aluminum foil current collector, with the coating speed controlled at 2 m / min and the wet film thickness on each side being 120 μm. Placed in a hot air drying oven, dried for 30 minutes at 120°C and normal pressure, and then compacted with a flat plate press at 15MPa and 60°C to obtain the positive electrode sheet. Step 5: Assembly and final curing of solid-state batteries The electrodes are stacked alternately in the order of "positive electrode plate - negative electrode assembly - positive electrode plate - negative electrode assembly"; The laminated structure is transferred to a hot press molding machine, and the hot pressing temperature is set to 100℃, the hot pressing pressure to 8MPa, and the hot pressing time to 15min, so that the polymer electrolyte layer partially penetrates into the interface of the positive electrode material layer and is fully cross-linked and cured. After hot pressing, the product is placed in a vacuum drying oven at a vacuum degree of 1×10⁻⁶. -2 Drying at 80°C for 20 minutes under Pa conditions removes residual solvent, resulting in a solid-state cell. The solid-state cell is then subjected to tab lead-out, encapsulation, and formation to finally obtain a solid-state battery.

[0065] Example 2 This embodiment illustrates the solid-state battery and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences: The corrugated grooves are 50μm deep and 150μm wide, with adjacent corrugated grooves arranged in parallel and spaced 200μm apart.

[0066] Example 3 This embodiment illustrates the solid-state battery and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences: The corrugated grooves are 100μm deep and 200μm wide, with adjacent corrugated grooves arranged in parallel and spaced 200μm apart.

[0067] Example 4 This embodiment illustrates the solid-state battery and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences: Step 2 is skipped, and in step 3, the polymer mixture slurry is directly coated on the surface of the corrugated groove.

[0068] Comparative Example 1 This comparative example illustrates the solid-state battery and its preparation method disclosed in this invention, including the following steps: Step 1: Using a slot coater, the prepared Li6PS5Cl sulfide electrolyte slurry is coated onto the surface of the lithium metal foil, with the coating speed controlled at 3m / min and the thickness at 200μm. Immediately transfer the coated composite structure to a heated roller press, set the roller pressing temperature to 50℃ and the roller pressing pressure to 8MPa, and use a smooth-surfaced roller; The rolled structure was placed in a vacuum drying oven at a vacuum degree of 5×10⁻⁶. -2 Dry at 80°C for 30 minutes to remove solvent.

[0069] Step 2: Formation of LiI-rich interfacial film A 20% LiI ethanol solution was sprayed onto the surface of the sulfide electrolyte layer using a pneumatic spraying device. The nozzle diameter was set to 0.2 mm, the spraying distance to 8 cm, the spraying speed to 80 mm / s, the thickness of a single spray was 2 μm, and a total of 2 sprays were applied (total target film thickness 4 μm). After spraying, the coating is dried in stages: first, it is dried at 60℃ and normal pressure for 8 minutes, and then the temperature is raised to 75℃ and normal pressure for 5 minutes. After drying, a continuous LiI lithium-rich interface film is formed on the surface of the sulfide electrolyte layer.

[0070] Step 3: Pre-curing of the polymer electrolyte layer A micro-coating machine was used to uniformly coat the polymer mixture slurry onto the surface of the lithium-rich LiI interface film. The mixture slurry included the following components by weight: 50 parts polyethylene glycol diglycidyl ether, 22 parts lithium bis(trifluorosulfonyl)imide, 10 parts triethanolamine, and 18 parts ethylene glycol dimethyl ether. Transfer to an inert gas drying oven (introduce high-purity N2, oxygen content ≤10ppm), set the pre-curing temperature to 60℃ and the pre-curing time to 10min, so that the polymer is partially cross-linked to obtain a complete negative electrode component. Step 4: Preparation of the positive electrode sheet A slot coater was used to coat the positive electrode slurry onto both sides of the aluminum foil current collector, with the coating speed controlled at 2 m / min and the wet film thickness on each side being 120 μm. Placed in a hot air drying oven, dried for 30 minutes at 120°C and normal pressure, and then compacted with a flat plate press at 15MPa and 60°C to obtain the positive electrode sheet. Step 5: Assembly and final curing of solid-state batteries The electrodes are stacked alternately in the order of "positive electrode plate - negative electrode assembly - positive electrode plate - negative electrode assembly"; The laminated structure is transferred to a hot press molding machine, and the hot pressing temperature is set to 100℃, the hot pressing pressure to 8MPa, and the hot pressing time to 15min, so that the polymer electrolyte layer partially penetrates into the interface of the positive electrode material layer and is fully cross-linked and cured. After hot pressing, the product is placed in a vacuum drying oven at a vacuum degree of 1×10⁻⁶. -2 Drying at 80°C for 20 minutes under Pa conditions removes residual solvent, resulting in a solid-state cell. The solid-state cell is then subjected to tab lead-out, encapsulation, and formation to finally obtain a solid-state battery.

[0071] Comparative Example 2 This comparative example is used to illustrate the solid-state battery and its preparation method disclosed in this invention, including most of the operation steps in Example 1, the difference being: Without performing step 3, the negative electrode component that forms the LiI lithium-rich interface film is directly subjected to subsequent hot pressing treatment with the positive electrode.

[0072] Performance testing The solid-state batteries prepared above were subjected to the following performance tests: Rate performance test: Three 0.2C rate charge-discharge activation cycles were performed: 0.2C constant current charging, cutoff voltage 4.3V, then constant voltage charging, and charging was stopped when the current dropped to 0.05C; 0.2C constant current discharging, cutoff voltage 3.0V, and the third discharge capacity C1 was recorded; the battery was charged to 4.3V at 0.2C current, then constant voltage charging was switched, and charging was stopped when the current dropped to 0.05C; 2C constant current discharging, cutoff voltage 3.0V, and the 2C discharge capacity C2 was recorded; 2C discharge capacity retention rate (%) = (C2 / C1) × 100%.

[0073] Cyclic performance test: 500 charge-discharge cycles were performed using the following method: 1C constant current charging, cutoff voltage 4.3V, switching to constant voltage charging, and stopping charging when the current dropped to 0.05C; 1C constant current discharging, cutoff voltage 3.0V; the initial discharge capacity C3 and the discharge capacity C4 of the 500th cycle were recorded, and the discharge capacity retention rate (%) after 500 cycles = (C4 / C3) × 100%.

[0074] The test results are entered into Table 1.

[0075] Table 1 Comparing the test results of Examples 1-3 and Comparative Example 1, it can be seen that the structural design of setting corrugated grooves on the surface of the sulfide electrolyte layer can significantly improve the high-rate discharge capacity retention rate and long-term cycle capacity retention rate of solid-state batteries. This indicates that the corrugated grooves effectively improve the interfacial ion transport efficiency and suppress interfacial side reactions by expanding the ion conduction area and reducing the direct contact area between the sulfide electrolyte layer and the cathode material layer, thus solving the problems of interfacial impedance and interfacial side reactions.

[0076] Comparing the test results of Examples 1-3 and Comparative Example 2, it can be seen that the setting of the polymer electrolyte layer is a key factor in improving battery performance. Without the polymer electrolyte layer, the battery's rate discharge capability and cycle stability drop significantly. In particular, when only the corrugated groove is set without the polymer electrolyte layer, the interfacial impedance problem is aggravated. This indicates that the filling effect of the polymer electrolyte layer on the interfacial gap and the isolation effect on the sulfide electrolyte and the positive electrode material can effectively prevent the breakage of the lithium-ion transport path at the solid-solid interface, thus ensuring the long-term stable operation of the battery.

[0077] Comparing the test results of Examples 1-3 and Example 4, it can be seen that the introduction of the LiI lithium-rich interface film can further optimize the battery performance. Without this interface film, the battery's rate discharge capacity retention rate and cycle capacity retention rate both decreased to a certain extent. This indicates that the LiI lithium-rich interface film can not only strengthen the lithium-ion transport channel and reduce the interface impedance, but also further block the direct contact between the sulfide electrolyte layer and the cathode material layer, thereby enhancing the interface stability and improving the overall electrochemical performance of the battery.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid-state battery, characterized in that, The device includes a positive electrode and a negative electrode assembly stacked sequentially. The positive electrode includes a positive current collector and a positive electrode material layer disposed on the surface of the positive current collector. The negative electrode assembly includes a negative electrode, a sulfide electrolyte layer, and a polymer electrolyte layer. The sulfide electrolyte layer is located on the surface of the negative electrode and has a corrugated groove disposed on the surface of the negative electrode away from the surface of the negative electrode. The polymer electrolyte layer is located in the corrugated groove and abuts against and partially penetrates into the positive electrode material layer.

2. The solid-state battery according to claim 1, characterized in that, The depth of the corrugated groove is 5μm to 500μm, and the width of the corrugated groove is 10μm to 800μm.

3. The solid-state battery according to claim 1, characterized in that, The sulfide electrolyte layer comprises the following components by weight: 92-98 parts of sulfide and 2-8 parts of binder.

4. The solid-state battery according to claim 3, characterized in that, The sulfide electrolyte layer has a LiI-rich interface film formed at the interface of the corrugated groove.

5. The solid-state battery according to claim 4, characterized in that, The thickness of the LiI lithium-rich interface film is 1~10μm.

6. The solid-state battery according to claim 1, characterized in that, The polymer electrolyte layer includes one or more of polyether polymer electrolytes, polyester polymer electrolytes, and polycarbonate polymer electrolytes.

7. The method for preparing a solid-state battery according to any one of claims 1 to 6, characterized in that, The following steps are included: A sulfide solid electrolyte slurry is coated on both sides of the negative electrode sheet, and a corrugated groove is obtained by surface processing. The sulfide electrolyte layer is then dried. A mixture of polymer monomers and lithium salts is coated onto the corrugated groove surface of a sulfide electrolyte layer and pre-cured to form a polymer electrolyte layer, thus obtaining a negative electrode component. The positive electrode slurry is coated onto both sides of the positive electrode current collector and dried to form a positive electrode material layer on both sides of the positive electrode current collector, thus obtaining a positive electrode sheet; The positive electrode and negative electrode components are alternately stacked, and hot pressing is used to allow the polymer electrolyte layer to partially penetrate into the interface of the positive electrode material layer and solidify and form the shape, followed by drying.

8. The method for preparing a solid-state battery according to claim 7, characterized in that, The corrugated groove is processed by using a pressure roller with a corrugated surface to roll the sulfide electrolyte layer on both sides to form a corrugated groove on the surface of the sulfide electrolyte layer.

9. The method for preparing a solid-state battery according to claim 7, characterized in that, After the corrugated groove is formed, LiI solution is sprayed onto the surface of the corrugated groove of the sulfide electrolyte layer and dried to form a LiI lithium-rich interface film on the surface of the corrugated groove.

10. The method for preparing a solid-state battery according to claim 7, characterized in that, The mixed slurry comprises the following components by weight: 42-60 parts of polymer precursor, 16-32 parts of lithium salt, 9-14 parts of curing agent, and 10-20 parts of solvent.

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