Study On Construction And Interfacial Modification Of All-solid-state Lithium Batteries Based On Solid-state Electrolyte Li₆PS₅Cl

All-solid-state batteries have been widely studied for their potential of high safety,high energy density and long cycle life,among which sulfide solid state batteries have received widespread attention because of their good overall performance.However,sulfide all-solid-state batteries still have problems such as high cathode interface impedance,instability to lithium metal cathodes and poor electrolyte stability that need to be solved and have failed to be commercialized.In this paper,Li₆PS₅Cl was prepared as a solid electrolyte to construct the layered oxide/lithium battery and the sulfur/lithium battery,and a systematic study on the cathode and anode electrode interfaces and electrolyte modification was conducted.The paper reveals the influence of the composite anode interface,garnet-Ag anode interface and electrolyte oxygen doping on the performance of the all-solid-state battery,and combines first principle calculations to elucidate the multi-interface reaction mechanism of the sulfide all-solid-state battery and optimize the electrochemical performance of the all-solid-state battery.The main research results are as follows.（1）A single pure phase Li₆PS₅Cl solid electrolyte was prepared by solid phase sintering method.To address the instability of Li₆PS₅Cl solid electrolyte and Li Co O₂ cathode,the Li₂WO₄ interfacial layer was found to effectively inhibit the side reaction between Li₆PS₅Cl and conventional cathode Li Co O₂ by first principle calculation.The uniform coating of 50nm Li₂WO₄ on the surface of Li Co O₂ particles was achieved by the aqueous phase coating method,and the interfacial resistance between Li₆PS₅Cl and Li Co O₂ was reduced from 1061Ωcm² to about 68Ωcm²after Li₂WO₄ coating.The discharge specific capacity at 0.1 C was 142.0m Ah g^-1,and the capacity retention was 93.0%after 100 cycles.X-ray photoelectron spectroscopy and molecular dynamics simulations showed that Li₂WO₄ could effectively prevent the formation of Co-S by-products from the diffusion of Co from Li Co O₂ to the inside of Li₆PS₅Cl solid electrolyte and improve the cycling performance.（2）In order to solve the nature problem of ion-electron insulation and large volume expansion for high specific capacity S cathode,The sulfur composite macroporous carbon（S@Ma PC）and sulfated polyacrylonitrile composite macroporous carbon（SPAN@Ma PC）cathode materials with high electronic conductivity were prepared.The physicochemical properties of S@Ma PC and SPAN@Ma PC materials were characterized and compared,and it was found that uniformly dispersed S_x（x=2-3）in the SPAN@Ma PC cathode enhanced the electrochemical reactivity of the electrode.The all-solid state battery constructed with SPAN@Ma PC cathode and Li-In anode had a higher discharge specific capacity of 1923.5m Ah g^-1 at 0.1 C and 857.8 m Ah g^-1 after 200 cycles compared to the liquid state battery.The impedance,morphology and elemental bind energy results of the SAPN@Ma PC cathode under different charge and discharge states indicated that the C-Li bond contributed to the super-theoretical capacity of the first-cycle S cathode.（3）To solve the difficulty that Li₆PS₅Cl solid-state electrolyte is unstable to lithium metal,a garnet oxide solid-state electrolyte（LLZTO）with Ag composite interface layer was proposed to improve the lithium anode interface of Li₆PS₅Cl all-solid-state battery.The high lithium conductivity of Ag and the stability of LLZTO to lithium were confirmed by reducing the interfacial impedance of LLZTO to lithium from 1900Ωcm² to 13Ωcm² through a WSe₂-Ag composite layer.On this basis,the improvement effect of LLZTO-Ag composite interfacial layer with different compositions on the anode interface for Li₆PS₅Cl based all-solid-state lithium metal batteries was investigated.The results showed that the LLZTO-Ag composite interfacial layer could prevent lithium dendrite growth and cell short circuit.Under the optimal process,the all-solid-state lithium metal battery had a 0.1 C first cycle efficiency of 77.5%,a discharge specific capacity of 187.3 m Ah g^-1 with a capacity retention of81.7%after 100 cycle at 0.3 C.（4）Li₆PS₅Cl solid electrolytes with different O doping amount(Li₆PS_5-xCl O_x,x=0～1)were prepared by O doping to improve the interfacial stability of Li₆PS₅Cl solid electrolyte.The results showed that the Li₆PS_4.75Cl O_0.25 solid electrolyte with a single F-43 m phase had the highest Li⁺conductivity of 4.7 m S cm^-1.The transition state calculations showed that the appropriate amount of O doping could reduce the Li⁺migration barrier between the"Li₆S cages"and thus improved the Li⁺conductivity.The uncoated-Li Co O₂/Li₆PS_4.75Cl O_0.25/Li-In all-solid-state battery had a discharge specific capacity of 129.7 m Ah g^-1 in the first cycle at 0.1 C and a capacity retention rate of 86.0%after 250 cycles at 0.3 C.In addition,the uncoated Li Ni_0.83Co_0.06Mn_0.11O₂/Li₆PS_4.75Cl O_0.25/Li-In all-solid-state battery had a capacity retention rate of 180.9 m Ah g^-1 at 0.1 C and a capacity retention rate of 89.5%after 100 cycles at 0.3 C.The Li-metal symmetric cell and band structure study showed that Li₆PS_4.75Cl O_0.25had better stability to lithium compared to Li₆PS₅Cl.