Method for improving interface stability of lithium metal negative electrode and sulfur-based solid electrolyte film
By synthesizing a LiI protective layer in situ on the surface of a lithium metal anode, the interfacial reaction problem between the sulfide solid electrolyte and the lithium metal anode was solved, thereby improving the interfacial stability and electrochemical performance of lithium-sulfur batteries.
Patent Information
- Application Number
- CN202511721727.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-02-27
AI Technical Summary
The interfacial reaction between the sulfide solid electrolyte and the lithium metal anode results in a large interfacial impedance and poor air stability, which affects the stability and electrochemical performance of the battery.
A LiI protective layer was synthesized in situ on the surface of a lithium metal anode as a buffer layer. LiI was used as a Li ion transport bridge to suppress Li dendrites and improve interface stability.
It significantly improves the interfacial stability between the lithium metal anode and the sulfur-based solid electrolyte film, thereby enhancing the electrochemical performance and cycle life of the battery.
Smart Images
Figure FT_1
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of energy power battery material preparation, and particularly relates to a method for improving the interface stability of a lithium metal negative electrode and a sulfur-based solid electrolyte thin film of a lithium-sulfur battery. BACKGROUND
[0002] With the wide application of lithium ion batteries in portable electronic devices, electric vehicles, power storage systems, aerospace, etc., the safety problem of the battery is increasingly prominent. Lithium ion batteries using organic electrolyte will trigger the internal reaction of the battery when overcharged, overdischarged, short-circuited, or misused, leading to thermal runaway and causing fire, even explosion. The all-solid-state lithium ion battery prepared by replacing the liquid electrolyte with the all-solid-state electrolyte is completely free of organic solvents, and has great space for improvement in energy density and cycle life, etc., and is therefore one of the important development directions of the next generation of lithium ion batteries.
[0003] Solid electrolyte (SEs) is the core component of the all-solid-state lithium ion battery, which plays a dual role of conducting ions and isolating electrons. The current research solid-state electrolyte mainly has three types of solid-state inorganic electrolyte, solid-state polymer electrolyte and inorganic-organic composite solid-state electrolyte according to its composition. Sulfide solid electrolyte has a high room temperature ionic conductivity (10 -4 ~10 -2 S / cm), and good mechanical strength and flexibility, and can realize good interface contact through mechanical cold pressing. However, the electrochemical window of the sulfide solid electrolyte is relatively narrow, the air stability is poor, it is easy to react with lithium metal, and a space charge layer is formed with the oxide positive electrode material, resulting in a large interface impedance. Sulfide also has two types of crystal and glass. The room temperature conductivity of the crystal electrolyte such as Li l0 GeP2S 12 (LGPS) can reach 1.2 x 10 -2 S / cm. The glassy electrolyte mainly has Li2S, SiS2system, and the room temperature conductivity can reach 1 x 10 2 S / cm. Although the sulfide electrolyte has a high room temperature ionic conductivity, it has problems of large interface impedance, poor compatibility with the electrode, and instability in the air, etc.
[0004] Lithium iodide (LiI) is a good conductor of lithium ions, has good chemical stability and environmental friendliness, and is highly compatible with lithium metal and solid-state electrolytes (SEs). Based on the high compatibility characteristics of LiI material, the patent application discloses a method for simply preparing a uniform LiI layer as a protective layer on the surface of a lithium metal negative electrode in situ to inhibit the interfacial reaction between lithium metal and sulfide electrolyte film. The presence of the LiI in-situ protective layer can prevent the reaction between the sulfide solid electrolyte and the lithium metal, thereby improving the stability of the battery. Therefore, the all-solid-state battery with the LiI in-situ protective layer has high first-cycle discharge capacity and ultra-long cycle life, and the soft package battery obtained has excellent electrochemical performance. SUMMARY
[0005] To solve the problem that the sulfide solid electrolyte is prone to react with lithium metal to cause large interfacial impedance, the present application discloses a method for improving the interfacial stability of a lithium metal negative electrode and a sulfide solid electrolyte, which introduces a LiI in-situ protective layer as a buffer layer on the surface of the lithium metal negative electrode and the sulfide solid electrolyte, and uses the protective layer of LiI to inhibit Li dendrites, so as to achieve better electrochemical effect. This method only in-situ synthesizes LiI on the surface of the Li metal through a simple solid-gas reaction method. LiI is a good conductor of lithium ions, and the LiI protective layer acts as a bridge for Li ion transmission at the Li metal / sulfide electrolyte interface, thereby improving the Li ion transmission efficiency at the Li / sulfide electrolyte interface. This method can significantly improve the interfacial stability of the lithium metal negative electrode and the sulfide solid electrolyte film, and is crucial for the industrial application of sulfide solid-state batteries from the laboratory stage.
[0006] A method for improving the interfacial stability of a lithium metal negative electrode and a sulfide solid electrolyte film, which is implemented by the following technical solutions: A method for improving the interfacial stability of a lithium metal negative electrode and a sulfide solid electrolyte film, which is implemented by the following technical solutions: First, improve the preparation of LiI@Li negative electrode material: in-situ synthesize LiI on the surface of Li metal through a simple solid-gas reaction method. First, wipe and polish the surface of the commercial Li foil (surface roughening of more than 100 μm); after polishing, place the Li foil and iodine powder in a glass container and seal, heat at a certain temperature for 3 hours, and then naturally cool to room temperature after the reaction between the metal Li foil and iodine vapor is completed. It can be seen that the color of the surface of the lithium metal changes from silver to golden yellow, indicating the formation of the LiI protective layer on the surface of the Li foil.
[0007] Second step, preparation of sulfur-based positive electrode thin film: under a protective gas atmosphere, a commercial LNO@NCM 811 positive electrode material is weighed, and then mixed uniformly according to the mass ratio of LNO@NCM 811: Li6PS5Cl (sulfide lithium phosphorus sulfur chloride): VGCF (vapor grown carbon fiber): PTFE (polytetrafluoroethylene powder) = 6:4:0.3:0.05, and then placed in a ball mill jar for 4h at 200 rpm. Then the positive electrode material is transferred to a smooth stainless steel plate, and repeatedly rolled into shape by a stainless steel roller to form a sulfur-based positive electrode thin film with a thickness of 20-30 mu m.
[0008] Third step, preparation of sulfide Li6PS5Cl solid electrolyte thin film: 0.2 g of pre-fiberized polytetrafluoroethylene (PTFE) dry powder and 20 g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte are mixed according to a mass ratio of 1wt%, and then transferred to a smooth stainless steel plate and repeatedly rolled into shape by a stainless steel roller to form an electrolyte film with a thickness of 20 mu m, which is a sulfide Li6PS5Cl solid electrolyte thin film.
[0009] Fourth step, assembly of soft package battery: the obtained LNO@NCM 811 positive electrode thin film, Li6PS5Cl solid electrolyte thin film and modified LiI@Li negative electrode material are pressed together for the assembly of a soft package battery and the electrochemical performance test.
[0010] The temperature refers to a solid-gas reaction at a temperature controlled at 150-250 DEG C; The sulfur-based positive electrode thin film material specifically refers to a thin film material formed by mixing and pressing LNO@NCM 811, Li6PS5Cl, VGCF and PTFE.
[0011] The thin film prepared by the application is applied to the field of high-performance power lithium batteries.
[0012] The technical principle of the application is that, by using the above preparation process, LiI is introduced as a buffer layer on the surface of the lithium metal negative electrode and the sulfide solid electrolyte, the LiI layer acts as a bridge for Li ion transmission at the Li metal / sulfide electrolyte interface, and at the same time, the growth of Li negative electrode dendrites is inhibited, thereby improving the Li ion transmission efficiency at the Li / sulfide electrolyte interface to achieve better electrochemical effect. At the same time, in order to improve the interface stability, the positive electrode material of the solid-state battery is specifically selected as LNO@NCM 811, and due to the existence of the LiI interface buffer layer, the electrochemical rate performance of the sulfide solid-state battery is improved by more than 10% compared with the solid-state battery without the LiI buffer layer, which further illustrates that the method is an effective and promising method for improving the interface stability of the lithium metal negative electrode and the sulfur-based solid electrolyte thin film. Attached Figure Description
[0013] Figure 1 The images show the charge-discharge spectra of sulfur-based solid electrolyte thin-film batteries at different rates for Example 1, using a LiI buffer layer (Figure a) and without a LiI buffer layer (Figure b).
[0014] The spectra show that the electrochemical performance of the sulfur-based solid electrolyte thin film battery with the LiI buffer layer is significantly improved by 10% compared with that without the LiI buffer layer. This indicates that the use of the LiI buffer layer can improve the interfacial stability between the lithium metal anode and the sulfur-based solid electrolyte thin film in lithium-sulfur batteries, thus enabling the sulfur-based solid electrolyte thin film battery to exhibit good electrochemical performance. Detailed Implementation
[0015] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiment.
[0016] Example 1 A method for improving the interfacial stability between a lithium metal anode and a sulfur-based solid electrolyte film involves introducing an in-situ LiI protective layer as a buffer layer on the surface of the lithium metal anode and the sulfide solid electrolyte. The LiI protective layer suppresses Li dendrite formation, thereby achieving better electrochemical performance. The method comprises the following steps: The first step was to improve the preparation of LiI@Li anode material: LiI was constructed in situ on the surface of Li metal using a simple solid-gas reaction method. The surface of a commercially available Li foil was first wiped and polished to remove surface contaminants, with a rough grinding thickness of over 100 μm. After polishing, the Li foil and iodine powder were placed in a sealed glass container and heated at 200 °C for 3 hours. After the reaction between the Li metal foil and iodine vapor was complete, the container was allowed to cool naturally to room temperature. It was observed that the surface color of the lithium metal changed from silver to golden yellow, indicating the formation of a LiI protective layer on the Li foil surface. The second step is the preparation of the sulfur-based cathode film: Under the protective atmosphere of Ar, commercial LNO@NCM 811 cathode material was weighed and thoroughly mixed according to the feeding ratio of LNO@NCM 811:Li6PS5Cl (sulfide lithium phosphorus sulfur chloride):VGCF (vapor-grown carbon fiber):PTFE (polytetrafluoroethylene powder) = 6:4:0.3:0.05. The mixture was then placed in a ball mill jar and ball-milled at 200 rpm for 4 hours. Next, the cathode material was transferred to a smooth stainless steel plate and repeatedly rolled and formed by stainless steel rollers to form a sulfur-based cathode film with a thickness of 20 μm. Third step, preparation of sulfide Li6PS5Cl solid-state electrolyte film: take 0.2 g of pre-fiberized PTFE dry powder and 20 g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte, mix them according to a mass ratio of 1 wt% of PTFE dry powder to Li6PS5Cl electrolyte, fully stir and mix in a mortar, then transfer to a smooth stainless steel plate, repeatedly roll and form into an electrolyte film with a thickness of 20 μm, which is the sulfide Li6PS5Cl solid-state electrolyte film; Fourth step, assembly of soft-pack battery: press together the obtained LNO@NCM 811 positive electrode film, Li6PS5Cl solid-state electrolyte film and modified LiI@Li negative electrode material, assemble a soft-pack battery and test its electrochemical performance.
[0017] Similarly, a soft-pack battery is also assembled for comparison, but the surface of the Li negative electrode material used is not subjected to solid-gas reaction of LiI layer and has no LiI buffer layer. The same means is used to assemble a soft-pack battery, and the electrochemical performance of the obtained soft-pack battery is compared.
[0018] Figure 1 Figure is a comparison of the charge-discharge performance of the sulfide solid-state electrolyte film battery of Example 1 using LiI buffer layer (a) and not using LiI buffer layer (b) at different rates. It can be seen from Figure 1 It can be seen that the electrochemical performance of the sulfide solid-state electrolyte film battery using LiI buffer layer is significantly improved compared with that of the sulfide solid-state electrolyte film battery without LiI buffer layer, which shows that the battery with LiI buffer layer has good electrochemical performance.
[0019] Example 2 This example is a comparative example, and the preparation process is similar to that of Example 1, the main difference being that no LiI buffer layer is used, i.e. no modified LiI@Li negative electrode material is prepared, and the specific implementation steps are as follows: First step, preparation of Li negative electrode material: first wipe and polish the surface of commercial Li foil to remove surface stains, and coarsely grind the surface to more than 100 μm; after polishing, store it in a glove box for standby; the difference from the first step of Example 1 is that no solid-gas reaction method is used to construct a LiI buffer layer on the surface of the Li metal in situ; Second step, preparation of sulfur-based positive electrode film: under the protection of argon gas, take the commercial LNO@NCM 811 positive electrode material, mix it evenly according to the mass ratio of LNO@NCM 811: Li6PS5Cl (sulfide lithium phosphorus sulfur chloride): VGCF (vapor grown carbon fiber): PTFE (polytetrafluoroethylene powder) = 6:4:0.3:0.05, and then place it in a ball mill jar for 4 hours at 200 rpm; then transfer the positive electrode material to a smooth stainless steel plate, and repeatedly roll it into a film with a thickness of 20-30 μm by selecting a stainless steel roller; Third step, preparation of sulfide Li6PS5Cl solid electrolyte film: take 0.2 g of pre-fiberized polytetrafluoroethylene (PTFE) dry powder and 20 g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte, mix them according to a mass ratio of 1wt%, and then transfer them to a smooth stainless steel plate after thoroughly mixing them with a mortar. Roll them into a film with a thickness of 20 μm by repeatedly rolling them with a stainless steel roller, and the film is the sulfide Li6PS5Cl solid electrolyte film. Fourth step, assembly of soft package battery: press the LNO@NCM 811 positive electrode film, Li6PS5Cl solid electrolyte film, and unmodified Li negative electrode material obtained in the first step together to assemble a soft package battery and test its electrochemical performance. Figure 1 b.
[0020] This embodiment is a comparative example, and the preparation process is similar to that of Example 1, but the surface of the Li negative electrode material does not have a LiI buffer layer. The same method is used to assemble a soft package battery, and the electrochemical performance of the obtained soft package battery is compared with that of Example 1.
[0021] Example 3 A method for improving the interface stability between a lithium metal negative electrode and a sulfur-based solid electrolyte film, comprising the following steps: First step, preparation of improved LiI@Li negative electrode material: use a simple solid-gas reaction method to construct LiI in situ on the surface of Li metal. The difference from Example 1 is the heating temperature. First, wipe and polish the surface of the commercial Li foil to remove surface stains, and roughen the surface to more than 100 μm. After polishing, place the Li foil and iodine powder in a glass container and seal it, control the temperature to 150 ℃, and heat for 3 hours. After the reaction between the metal Li foil and the iodine vapor is completed, naturally cool to room temperature. It can be seen that the color of the lithium metal surface changes from silver to golden yellow, indicating the formation of a LiI protective layer on the surface of the Li foil. Second step, preparation of the sulfur-based positive electrode thin film: under the protection of argon gas, the commercial LNO@NCM 811 positive electrode material was weighed, and mixed with Li6PS5Cl (sulfide lithium phosphorus sulfur chloride) and VGCF (vapor grown carbon fiber) and PTFE (polytetrafluoroethylene powder) in a mass ratio of 6:4:0.3:0.05, and then placed in a ball mill jar for 4 hours at 200 rpm. Then the positive electrode material was transferred to a smooth stainless steel plate and repeatedly rolled to form a sulfur-based positive electrode thin film with a thickness of 20 microns. Third step, preparation of the sulfide Li6PS5Cl solid electrolyte thin film: 0.2 g of pre-fiberized polytetrafluoroethylene PTFE dry powder and 20 g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte were mixed in a mass ratio of 1 wt%, and then transferred to a smooth stainless steel plate and repeatedly rolled to form an electrolyte film with a thickness of 20 microns, which is the sulfide Li6PS5Cl solid electrolyte thin film.
[0022] Fourth step, assembly of the soft package battery: the obtained LNO@NCM 811 positive electrode thin film, Li6PS5Cl solid electrolyte thin film and modified LiI@Li negative electrode material were pressed together to assemble the soft package battery and perform electrochemical performance test.
[0023] The above description is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method for improving the interfacial stability between a lithium metal anode and a sulfur-based solid electrolyte film, characterized in that... By introducing an in-situ protective layer of LiI as a buffer layer on the surface of the lithium metal anode and the sulfide solid electrolyte, the LiI protective layer can suppress Li dendrites, thereby achieving better electrochemical performance. The specific implementation steps are as follows: The first step was to improve the preparation of LiI@Li anode material: LiI was synthesized in situ on the surface of Li metal using a simple solid-gas reaction method. The surface of a commercial Li foil was first wiped and polished (roughly ground to a thickness of more than 100 μm). After polishing, the Li foil and iodine powder were placed in a glass container and sealed. The container was heated at a certain temperature for 3 hours. After the reaction between the Li metal foil and iodine vapor was completed, the container was allowed to cool naturally to room temperature. It can be seen that the surface color of the lithium metal changed from silver to golden yellow, indicating the formation of a LiI protective layer on the surface of the Li foil. The second step is the preparation of the sulfur-based cathode film: Under a protective gas atmosphere, commercially available LNO@NCM 811 cathode material was weighed and thoroughly mixed according to the following mass ratio: LNO@NCM 811:Li6PS5Cl (sulfide lithium phosphorus sulfur chloride):VGCF (vapor-grown carbon fiber):PTFE (polytetrafluoroethylene powder) = 6:4:0.3:0.
05. The mixture was then placed in a ball mill jar and ball-milled at 200 rpm for 4 hours. Next, the cathode material was transferred to a smooth stainless steel plate and repeatedly rolled and formed by stainless steel rollers to form a sulfur-based cathode film with a thickness of 20~30μm. The third step is the preparation of the sulfide Li6PS5Cl solid electrolyte film: Weigh 0.2 g of pre-fiberized polytetrafluoroethylene (PTFE) dry powder and 20 g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte. Mix the PTFE dry powder and Li6PS5Cl electrolyte at a mass ratio of 1 wt%. After thorough mixing in a mortar, transfer the mixture to a smooth stainless steel plate and roll it repeatedly with a stainless steel roller to form an electrolyte film with a thickness of 20 μm, which is the sulfide Li6PS5Cl solid electrolyte film. The fourth step is the assembly of the pouch cell: the obtained LNO@NCM 811 positive electrode film, Li6PS5Cl solid electrolyte film and modified LiI@Li negative electrode material are pressed together to assemble the pouch cell and perform electrochemical performance testing.
2. The method for improving the interfacial stability between lithium metal anode and sulfur-based solid electrolyte film according to claim 1, characterized in that, In the first step, a solid-gas reaction is carried out at a temperature of 150~250 ℃.
3. The method for improving the interfacial stability between lithium metal anode and sulfur-based solid electrolyte film according to claim 1, characterized in that, In the second step, a sulfur-based cathode thin film material is formed by mixing and pressing LNO@NCM 811, Li6PS5Cl, VGCF and PTFE.
4. The method for improving the interfacial stability between a lithium metal anode and a sulfur-based solid electrolyte film according to any one of claims 1 to 3, characterized in that, Follow these steps: The first step was to improve the preparation of LiI@Li anode material: LiI was constructed in situ on the surface of Li metal using a simple solid-gas reaction method. The surface of a commercially available Li foil was first wiped and polished to remove surface contaminants, with a rough grinding thickness of over 100 μm. After polishing, the Li foil and iodine powder were placed in a sealed glass container and heated at 200 °C for 3 hours. After the reaction between the Li metal foil and iodine vapor was complete, the container was allowed to cool naturally to room temperature. It was observed that the surface color of the lithium metal changed from silver to golden yellow, indicating the formation of a LiI protective layer on the Li foil surface. The second step is the preparation of the sulfur-based cathode film: Under the protective atmosphere of Ar, commercial LNO@NCM 811 cathode material was weighed and thoroughly mixed according to the feeding ratio of LNO@NCM 811:Li6PS5Cl (sulfide lithium phosphorus sulfur chloride):VGCF (vapor-grown carbon fiber):PTFE (polytetrafluoroethylene powder) = 6:4:0.3:0.
05. The mixture was then placed in a ball mill jar and ball-milled at 200 rpm for 4 hours. Next, the cathode material was transferred to a smooth stainless steel plate and repeatedly rolled and formed by stainless steel rollers to form a sulfur-based cathode film with a thickness of 20 μm. The third step is the preparation of the sulfide Li6PS5Cl solid electrolyte film: Weigh 0.2g of pre-fiberized PTFE dry powder and 20g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte, mix them according to the mass ratio of 1 wt% of PTFE dry powder and Li6PS5Cl electrolyte, stir and mix them thoroughly in a mortar, transfer them to a smooth stainless steel plate, and roll them repeatedly with a stainless steel roller to form an electrolyte film with a thickness of 20 μm, which is the sulfide Li6PS5Cl solid electrolyte film. The fourth step is the assembly of the pouch cell: the obtained LNO@NCM 811 positive electrode film, Li6PS5Cl solid electrolyte film and modified LiI@Li negative electrode material are pressed together to assemble the pouch cell and perform electrochemical performance testing.
5. The method for improving the interfacial stability between a lithium metal anode and a sulfur-based solid electrolyte film according to any one of claims 1 to 3, characterized in that, Follow these steps: The first step was to improve the preparation of LiI@Li anode material: LiI was constructed in situ on the surface of Li metal using a simple solid-gas reaction method. The difference from Example 1 was the heating temperature. First, the surface of the commercial Li foil was wiped and polished to remove surface stains, and the surface was rough ground to a depth of more than 100 μm. After polishing, the Li foil and iodine powder were placed in a glass container and sealed. The temperature was controlled at 150 °C and heated for 3 hours. After the reaction between the Li metal foil and iodine vapor was completed, the temperature was allowed to drop naturally to room temperature. It can be seen that the surface color of the lithium metal changed from silver to golden yellow, indicating the formation of the LiI protective layer on the surface of the Li foil. The second step is the preparation of the sulfur-based cathode film: Under the protective atmosphere of Ar, commercial LNO@NCM 811 cathode material was weighed and thoroughly mixed according to the following mass ratio: LNO@NCM 811:Li6PS5Cl (sulfide lithium phosphorus sulfur chloride):VGCF (vapor-grown carbon fiber):PTFE (polytetrafluoroethylene powder) = 6:4:0.3:0.
05. The mixture was then placed in a ball mill jar and ball-milled at 200 rpm for 4 hours. Next, the cathode material was transferred to a smooth stainless steel plate and repeatedly rolled and formed by stainless steel rollers to form a sulfur-based cathode film with a thickness of 20 μm. The third step is the preparation of the sulfide Li6PS5Cl solid electrolyte film: Weigh 0.2 g of pre-fiberized polytetrafluoroethylene (PTFE) dry powder and 20 g of sulfide lithium phosphorus sulfur chloride (Li6PS5Cl) electrolyte. Mix the PTFE dry powder and Li6PS5Cl electrolyte at a mass ratio of 1 wt%. After thorough mixing in a mortar, transfer the mixture to a smooth stainless steel plate and roll it repeatedly with a stainless steel roller to form an electrolyte film with a thickness of 20 μm, which is the sulfide Li6PS5Cl solid electrolyte film. The fourth step is the assembly of the pouch cell: the obtained LNO@NCM 811 positive electrode film, Li6PS5Cl solid electrolyte film and modified LiI@Li negative electrode material are pressed together to assemble the pouch cell and perform electrochemical performance testing.
6. A method for improving the interfacial stability between the lithium metal anode and the sulfur-based solid electrolyte film, enabling the application of the obtained sulfur-based solid electrolyte film battery in the field of high-performance power lithium batteries.