A process for preparing lithium metal surface coating modification for sulfide solid electrolytes

Abstract

This invention relates to a process for preparing lithium metal surface coating modification for sulfide solid electrolytes, belonging to the field of solid-state lithium battery material preparation technology. Lithium metal foil is ultrasonically cleaned with anhydrous ethanol and dried. The dried lithium metal foil is placed on the sample stage of a magnetron sputtering device, using an Al target as the sputtering source, and a mixed gas is introduced for magnetron sputtering to form an Al2O3 underlayer. Lithium ethanol and phosphoric acid are used as lithium and phosphorus sources respectively, and argon gas is introduced as the carrier gas. A composite coating of Li3PO4-Al2O3 is obtained through plasma-assisted atomic layer deposition. The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, cooled, and then transferred to a plasma device, where a mixed gas is introduced for plasma treatment. After argon purging, the foil is removed, sealed, and stored in a glove box. The coated modified lithium metal prepared by this invention can effectively reduce interfacial impedance and significantly improve battery cycle stability.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium battery material preparation technology, and in particular to a lithium metal surface coating modification preparation process for sulfide solid electrolytes. Background Technology

[0002] Solid-state lithium batteries have become an important development direction for next-generation power batteries due to their advantages such as high energy density and good safety. Among them, sulfide solid electrolytes have been widely studied due to their high lithium-ion conductivity and excellent machinability. However, the interfacial compatibility problem between sulfide solid electrolytes and lithium metal anodes seriously restricts their industrial application.

[0003] Chinese Patent CN112958734A discloses a method for preparing two-dimensional lithium metal and its application in new energy batteries such as lithium-sulfur batteries and lithium-air batteries. The method for preparing two-dimensional lithium metal includes: preparing two-dimensional lithium metal by free compression in a protective atmosphere; preparing two-dimensional lithium metal by die compression; preparing two-dimensional lithium metal by rolling; preparing two-dimensional lithium metal by extrusion; and preparing two-dimensional lithium metal by shearing.

[0004] Chinese patent CN119208541A ​​discloses a high-energy-density battery using a surface-alloyed lithium anode and its preparation method. The method involves dissolving a metal element or metal compound that can react with lithium foil in an organic solvent to form a precursor solution. The precursor solution is then sprayed onto the surface of the lithium foil and allowed to stand and react for a period of time. After removing excess liquid and drying to remove the solvent, a metallic lithium anode with an alloyed modification layer on its surface is obtained.

[0005] In existing technologies, methods for modifying the surface of lithium metal mainly include the sol-gel method and the deposition method. The sol-gel method suffers from poor coating uniformity and reduced interface stability due to residual organic solvents; the deposition method results in low coating density and cannot effectively suppress lithium dendrite growth. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a process for preparing lithium metal surface coating modification for sulfide solid electrolytes, the operation steps of which are as follows: S1 Lithium metal pretreatment: After ultrasonic cleaning of lithium metal foil with anhydrous ethanol for 10-15 minutes, it is dried with argon gas. S2 Magnetron Sputtering Undercoat: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering, forming an Al2O3 undercoat with a thickness of 50-100nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid are used as lithium source and phosphorus source, respectively, and argon gas is introduced as carrier gas. The plasma power is set to 50-80W, the deposition temperature is controlled at 80-120℃, and the deposition is cycled 30-50 times to form a Li3PO4 coating layer with a thickness of 100-200nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, transferred to a plasma device, and evacuated to 1×10⁻⁶. -3 Pa; introduce mixed gas for plasma treatment; after purging with argon, remove and seal for storage in a glove box.

[0007] Optionally, the S2 mixed gas is argon and oxygen in a volume ratio of 8-9:1, and the flow rate of the mixed gas is 20-30 sccm.

[0008] Optionally, the stage rotation speed during the S2 magnetron sputtering process is 5-10 r / min.

[0009] Optionally, the S2 magnetron sputtering power is 80-120W, the deposition temperature is 25-40℃, and the deposition time is 5-10min.

[0010] Optionally, a single cycle of the S3 plasma-assisted atomic layer deposition includes: lithium ethanol pulse introduction for 1-4 s, argon purging for 10-15 s, phosphoric acid pulse introduction for 1-4 s, argon purging for 10-15 s, and plasma treatment for 5-8 s.

[0011] Optionally, the S4 vacuum annealing heating rate is 5-10℃ / min to prevent lithium metal from melting due to a sudden temperature rise.

[0012] Optionally, the S4 vacuum annealing temperature is 150-200℃ and the time is 2-5h.

[0013] Optionally, the S4 mixed gas is argon / trimethylammonium gallium vapor with a volume ratio of 1-1.2:0.05-0.3 and a mixed gas flow rate of 20-30 sccm.

[0014] Optionally, the S4 plasma treatment power is 50-80W and the time is 10-20min.

[0015] Optionally, the S4 argon purging time is 5-10 min.

[0016] I. Reaction Mechanism The lithium metal surface is first ultrasonically cleaned to remove the oxide layer and impurities. Then, during magnetron sputtering, aluminum ions generated by the ionization of the Al target in an argon-oxygen mixed gas atmosphere combine with oxygen ions to deposit a dense Al2O3 underlayer. In the plasma-assisted atomic layer deposition stage, lithium ions dissociated from lithium ethanol and phosphate ions provided by phosphoric acid gradually bond under the activation of plasma to form a Li3PO4 coating layer, thus constructing a Li3PO4-Al2O3 composite coating layer. Subsequent vacuum annealing promotes the crystallization of the composite coating layer and activates its surface active sites such as hydroxyl groups and oxygen vacancies. In the plasma environment, trimethylaminogallium decomposes to generate gallium ions, which coordinate and bond with the active sites on the surface of the composite coating layer, ultimately forming a multilayer protective structure of "Al2O3-Li3PO4-gallium ions".

[0017] II. Technical Effects The multi-layer protective structure has a synergistic effect. The dense properties of the Al2O3 bottom layer can reduce adverse interfacial reactions between the sulfide solid electrolyte and the lithium metal anode, while the ion conduction properties of the Li3PO4 coating layer can optimize the interfacial ion transport channels. The combination of the two can effectively reduce interfacial impedance and improve the interfacial compatibility between the electrode and the electrolyte.

[0018] Gallium ion grafting achieved through plasma treatment can further regulate the interface ion transport efficiency, while enhancing the chemical stability of the lithium metal surface, suppressing the growth of lithium dendrites during cycling, and avoiding internal short circuits or performance degradation caused by lithium dendrite punctures.

[0019] The stable protection system built by the entire coating and modification process provides a continuous and stable electrode interface environment for sulfide solid-state batteries from two core dimensions: interface impedance optimization and lithium dendrite suppression, which helps to improve the capacity stability of the battery during long-term cycling. Detailed Implementation

[0020] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples: Battery assembly: Using the coated modified lithium metal prepared in the examples and comparative examples as the negative electrode, the NCM811 / sulfide composite positive electrode (NCM811:sulfide electrolyte: conductive carbon black = 7:2:1, mass ratio) as the positive electrode, and the sulfide electrolyte as the separator, coin cells were assembled in a glove box.

[0021] 1. Interface impedance: Electrochemical impedance spectroscopy (EIS) was used to test the interface impedance on a CHI660E electrochemical workstation. 2. Cyclic performance test: Using the LAND battery testing system, the capacity retention rate was recorded after 100 cycles at 25℃ and 0.1C rate.

[0022] Example 1 A process for preparing lithium metal surface coating modification for sulfide solid electrolytes, comprising the following steps: S1 Lithium metal pretreatment: Lithium metal foil is ultrasonically cleaned with anhydrous ethanol for 10 minutes and then dried with argon gas. S2 Magnetron Sputtering Underlayer: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering and form an Al2O3 underlayer with a thickness of 50nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid were used as lithium source and phosphorus source, respectively, and argon gas was introduced as carrier gas. The plasma power was set to 50W, the deposition temperature was controlled at 80℃, and the deposition was cycled 30 times to form a Li3PO4 coating layer with a thickness of 100nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, transferred to a plasma device, and evacuated to 1×10⁻⁶. -3 Pa; introduce mixed gas for plasma treatment; after purging with argon, remove and seal for storage in a glove box.

[0023] The S2 mixed gas is argon and oxygen in a volume ratio of 8:1, and the flow rate of the mixed gas is 20 sccm.

[0024] The sample stage rotation speed is 5 r / min during the S2 magnetron sputtering process.

[0025] The S2 sputtering power is 80W, the deposition temperature is 25℃, and the deposition time is 5min.

[0026] The single cycle of assisted atomic layer deposition during S3 plasma treatment includes: lithium ethanol pulse introduction for 1s, argon purging for 10s, phosphoric acid pulse introduction for 1s, argon purging for 10s, and plasma treatment for 5s.

[0027] The S4 annealing heating rate is 5℃ / min to prevent lithium metal from melting due to a sudden temperature rise.

[0028] The S4 vacuum annealing temperature is 150℃ and the time is 2 hours.

[0029] The S4 mixed gas is argon / trimethylammonium gallium vapor with a volume ratio of 1:0.05 and a flow rate of 20 sccm.

[0030] The S4 plasma treatment power is 50W and the time is 10min.

[0031] The S4 argon purging time is 5 minutes.

[0032] Example 2 A process for preparing lithium metal surface coating modification for sulfide solid electrolytes, comprising the following steps: S1 Lithium metal pretreatment: The lithium metal foil was ultrasonically cleaned with anhydrous ethanol for 12 minutes and then dried with argon gas. S2 Magnetron Sputtering Underlayer: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering and form an Al2O3 underlayer with a thickness of 60nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid were used as lithium source and phosphorus source, respectively, and argon gas was introduced as carrier gas. The plasma power was set to 60W, the deposition temperature was controlled at 90℃, and the deposition was cycled 35 times to form a Li3PO4 coating layer with a thickness of 140nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, transferred to a plasma device, and evacuated to 1×10⁻⁶. -3 Pa; introduce mixed gas for plasma treatment; after purging with argon, remove and seal for storage in a glove box.

[0033] The S2 mixed gas is argon and oxygen in a volume ratio of 8:1, and the flow rate of the mixed gas is 25 sccm.

[0034] The sample stage rotation speed is 6 r / min during the S2 magnetron sputtering process.

[0035] The S2 sputtering power is 90W, the deposition temperature is 30℃, and the deposition time is 6min.

[0036] The single cycle of the S3 plasma-assisted atomic layer deposition includes: lithium ethanol pulse introduction for 2s, argon purging for 12s, phosphoric acid pulse introduction for 2s, argon purging for 12s, and plasma treatment for 6s.

[0037] The S4 annealing heating rate is 6℃ / min to prevent lithium metal from melting due to a sudden temperature rise.

[0038] The S4 vacuum annealing temperature is 160℃ and the time is 3h.

[0039] The S4 mixed gas is argon / trimethylammonium gallium vapor with a volume ratio of 1.1:0.1 and a flow rate of 25 sccm.

[0040] The S4 plasma treatment power is 60W and the time is 15min.

[0041] The S4 argon purging time is 6 minutes.

[0042] Example 3 A process for preparing lithium metal surface coating modification for sulfide solid electrolytes, comprising the following steps: S1 Lithium metal pretreatment: The lithium metal foil was ultrasonically cleaned with anhydrous ethanol for 14 minutes and then dried with argon gas. S2 Magnetron Sputtering Underlayer: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering and form an Al2O3 underlayer with a thickness of 80nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid were used as lithium source and phosphorus source, respectively, and argon gas was introduced as carrier gas. The plasma power was set to 70W, the deposition temperature was controlled at 110℃, and the deposition was cycled 45 times to form a Li3PO4 coating layer with a thickness of 180nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, transferred to a plasma device, and evacuated to 1×10⁻⁶. -3 Pa; introduce mixed gas for plasma treatment; after purging with argon, remove and seal for storage in a glove box.

[0043] The S2 mixed gas is argon and oxygen in a volume ratio of 9:1, and the flow rate of the mixed gas is 25 sccm.

[0044] The sample stage rotation speed is 8 r / min during the S2 magnetron sputtering process.

[0045] The S2 sputtering power is 110W, the deposition temperature is 35℃, and the deposition time is 8min.

[0046] The single cycle of the S3 plasma-assisted atomic layer deposition includes: lithium ethanol pulse introduction for 3s, argon purging for 14s, phosphoric acid pulse introduction for 3s, argon purging for 14s, and plasma treatment for 7s.

[0047] The S4 annealing heating rate is 8°C / min to prevent lithium metal from melting due to a sudden temperature rise.

[0048] The S4 vacuum annealing temperature is 180℃ and the time is 4 hours.

[0049] The S4 mixed gas is argon / trimethylammonium gallium vapor with a volume ratio of 1.1:0.2 and a flow rate of 25 sccm.

[0050] The S4 plasma treatment power is 70W and the time is 15min.

[0051] The S4 argon purging time is 8 minutes.

[0052] Example 4 A process for preparing lithium metal surface coating modification for sulfide solid electrolytes, comprising the following steps: S1 Lithium metal pretreatment: The lithium metal foil is ultrasonically cleaned with anhydrous ethanol for 15 minutes and then dried with argon gas. S2 Magnetron Sputtering Underlayer: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering and form an Al2O3 underlayer with a thickness of 100nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid were used as lithium source and phosphorus source, respectively, and argon gas was introduced as carrier gas. The plasma power was set to 80W, the deposition temperature was controlled at 120℃, and the deposition cycle was 50 times to form a Li3PO4 coating layer with a thickness of 200nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, transferred to a plasma device, and evacuated to 1×10⁻⁶. -3 Pa; introduce mixed gas for plasma treatment; after purging with argon, remove and seal for storage in a glove box.

[0053] The S2 mixed gas is argon and oxygen in a volume ratio of 9:1, and the flow rate of the mixed gas is 30 sccm.

[0054] The sample stage rotation speed is 10 r / min during the S2 magnetron sputtering process.

[0055] The S2 sputtering power is 120W, the deposition temperature is 40℃, and the deposition time is 10min.

[0056] The single cycle of the S3 plasma-assisted atomic layer deposition includes: lithium ethanol pulse introduction for 4s, argon purging for 15s, phosphoric acid pulse introduction for 4s, argon purging for 15s, and plasma treatment for 8s.

[0057] The S4 annealing heating rate is 10℃ / min to prevent lithium metal from melting due to a sudden temperature rise.

[0058] The S4 vacuum annealing temperature is 200℃ and the time is 5h.

[0059] The S4 mixed gas is argon / trimethylammonium gallium vapor with a volume ratio of 1.2:0.3 and a flow rate of 30 sccm.

[0060] The S4 plasma treatment power is 80W and the time is 20min.

[0061] The S4 argon purging time is 10 minutes.

[0062] Comparative Example 1 A process for preparing lithium metal surface coating modification for sulfide solid electrolytes, comprising the following steps: S1 Lithium metal pretreatment: Lithium metal foil is ultrasonically cleaned with anhydrous ethanol for 10 minutes and then dried with argon gas. S2 Magnetron Sputtering Underlayer: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering and form an Al2O3 underlayer with a thickness of 50nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid were used as lithium source and phosphorus source, respectively, and argon gas was introduced as carrier gas. The plasma power was set to 50W, the deposition temperature was controlled at 80℃, and the deposition was cycled 30 times to form a Li3PO4 coating layer with a thickness of 100nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, and then sealed and stored in a glove box.

[0063] The S2 mixed gas is argon and oxygen in a volume ratio of 8:1, and the flow rate of the mixed gas is 20 sccm.

[0064] The sample stage rotation speed is 5 r / min during the S2 magnetron sputtering process.

[0065] The S2 sputtering power is 80W, the deposition temperature is 25℃, and the deposition time is 5min.

[0066] The single cycle of the S3 plasma-assisted atomic layer deposition includes: lithium ethanol pulse introduction for 1 second, argon purging for 10 seconds, phosphoric acid pulse introduction for 1 second, argon purging for 10 seconds, and plasma treatment for 5 seconds.

[0067] The S4 annealing heating rate is 5℃ / min to prevent lithium metal from melting due to a sudden temperature rise.

[0068] The S4 vacuum annealing temperature is 150℃ and the time is 2 hours.

[0069] Table 1 shows the test results of interfacial impedance and capacity retention of the modified lithium metal in the examples and comparative examples.

[0070] As can be seen from the test results of the examples and comparative examples in Table 1, the sample of the example using the complete preparation process of this invention (including pretreatment, magnetron sputtering, plasma-assisted atomic layer deposition composite coating, vacuum annealing, and subsequent plasma treatment) has a significantly lower interface impedance level than the comparative example sample without plasma treatment, and its capacity retention rate is much higher than that of the comparative example sample. This difference indicates that this invention, by introducing a gallium ion-grafted multilayer coating structure, effectively solves the key problems of high interface impedance and poor cycle stability in traditional lithium metal surface modification processes, fully verifying the effectiveness and superiority of this lithium metal surface coating modification preparation process in optimizing the performance of sulfide solid-state batteries.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for preparing lithium metal surface coating modification for sulfide solid electrolytes, comprising the following steps: S1 Lithium metal pretreatment: After ultrasonic cleaning of lithium metal foil with anhydrous ethanol for 10-15 minutes, it is dried with argon gas. S2 Magnetron Sputtering Undercoat: The pretreated lithium metal foil is placed on the sample stage of the magnetron sputtering equipment. Using an Al target as the sputtering source, a mixed gas is introduced to perform magnetron sputtering, forming an Al2O3 undercoat with a thickness of 50-100nm. S3 Plasma-Assisted Atomic Layer Deposition Composite Coating: Lithium ethanol and phosphoric acid are used as lithium source and phosphorus source, respectively, and argon gas is introduced as carrier gas. The plasma power is set to 50-80W, the deposition temperature is controlled at 80-120℃, and the deposition is cycled 30-50 times to form a Li3PO4 coating layer with a thickness of 100-200nm on the surface of the Al2O3 base layer, thus obtaining the Li3PO4-Al2O3 composite coating layer. S4 Vacuum Annealing and Curing: The composite-coated lithium metal foil is transferred to a vacuum annealing furnace for vacuum annealing, naturally cooled to room temperature, transferred to a plasma device, and evacuated to 1×10⁻⁶. -3 Pa; introduce mixed gas for plasma treatment; after purging with argon, remove and seal for storage in a glove box.

2. The lithium metal surface coating modification preparation process for sulfide solid electrolytes according to claim 1, characterized in that: The S2 mixed gas is argon and oxygen in a volume ratio of 8-9:1, and the flow rate of the mixed gas is 20-30 sccm.

3. The lithium metal surface coating modification preparation process for sulfide solid electrolytes according to claim 1, characterized in that: The sample stage rotation speed is 5-10 r / min during the S2 magnetron sputtering process.

4. The lithium metal surface coating modification preparation process for sulfide solid electrolytes according to claim 1, characterized in that: The S2 magnetron sputtering power is 80-120W, the deposition temperature is 25-40℃, and the deposition time is 5-10min.

5. The lithium metal surface coating modification preparation process for sulfide solid electrolytes according to claim 1, characterized in that: The single cycle of the S3 plasma-assisted atomic layer deposition includes: lithium ethanol pulse introduction for 1-4s, argon purging for 10-15s, phosphoric acid pulse introduction for 1-4s, argon purging for 10-15s, and plasma treatment for 5-8s.

6. The process for preparing lithium metal surface coating modification for sulfide solid electrolytes according to claim 1, characterized in that: The S4 vacuum annealing heating rate is 5-10℃ / min to prevent lithium metal from melting due to a sudden temperature rise.

7. The lithium metal surface coating modification preparation process for sulfide solid electrolytes according to claim 1, characterized in that: The S4 vacuum annealing temperature is 150-200℃, and the time is 2-5h.

8. The lithium metal surface coating modification preparation process for sulfide solid electrolytes according to claim 1, characterized in that: The S4 mixed gas is argon / trimethylammonium gallium vapor with a volume ratio of 1-1.2:0.05-0.3 and a flow rate of 20-30 sccm.

9. The process for preparing lithium metal surface coating modification for sulfide solid electrolytes according to claim 1, characterized in that: The S4 plasma treatment power is 50-80W, and the time is 10-20min.

10. The process for preparing lithium metal surface coating modification for sulfide solid electrolytes according to claim 1, characterized in that: The S4 argon purging time is 5-10 minutes.

Images