Preparation Of Li₆PS₅Cl Solid Electrolyte Film And Properties Of All Solid-state Batteries

Lithium-ion batteries play an irreplaceable role in the field of portable electronic equipment and electric vehicles because of their high energy density,high power density and long cycle life.However,the high volatility and potential fire hazard of liquid electrolyte badly limit its practical application.All-solid-state lithium batteries（ASSLBs）use non-flammable solid electrolytes,which can provide better energy density while avoiding the safety issues of lithium metal batteries using organic electrolytes.Li₆PS₅Cl（LPSCl）is considered as one of the most promising sulfide solid-state electrolytes（SEs）due to its excellent mechanical ductility and high ionic conductivity.Aiming at the low energy density of LPSCl solid-state electrolyte,the poor contact and stability between SEs and cathode/anode,this paper improved the electrochemical performance of ASSLBs by thinning electrolyte thickness and interface regulation.The main research contents are as follows:（1）Inspired by the reinforced concrete structure,using cellulose film as supporting frame and Li₆PS₅Cl as SEs,the SEs film with thickness of 90μm was prepared by slurry casting process.The introduced cellulose membrane ionic conductive frame had good water absorption and chemical compatibility,which greatly reduced the thickness of SEs.At room temperature,it had a high ionic conductivity(1.09 m S cm^-1).In addition,Li Nb O₃@NCM622 cathode material was prepared by atomic deposition.Li Nb O₃@NCM622/LPSCl thin film/Li-In ASSLBs had high specific capacity and excellent cycle stability performance.At the current density of 0.1C,the specific discharge capacity of the first circle reached 160m Ah g^-1 and 150cycles,the capacity retention rate was 87%.（2）Based on the shortcomings of the above studies,an ultra-thin flexible and self-supporting sulfide electrolyte film with a thickness of 50 microns was prepared by mechanical processing technology with PTFE as the binder.The introduction of PTFE improved the transport capacity of lithium ions in the SEs film,resulting in an ultra-high ionic conductivity of 4.9 m S cm^-1.In addition,Li₂Zr O₃@NCM622 cathode material was prepared by wet chemical method and meanwhile a solvent-free self-supported composite cathode was prepared,which alleviated the problem of poor electrochemical stability caused by solid-solid contact.At 0.1C high current density,the capacity retention rate was 85.5%after 320 cycles.Under the high current density of 1 C,the first charging capacity of 120 m Ah g^-1 was shown.After 100 cycles,the capacity retention rate was up to 89%.（3）In the above study,Li-In alloy was use as the anode,which limited the voltage window of the whole cell.However,when using lithium metal as the anode,lithium dendrites will be generated in the pores and grain boundaries of SEs film,which is not conducive to the transmission between LPSCl film and lithium ions.More seriously,lithium dendrites will grow inside the electrolyte and penetrate the electrolyte,resulting in short circuit of the battery.By forcibly contacting P₂S₅ powder with Li metal,the spontaneous reduction reaction between Li metal and P₂S₅ powder was induced and then uniform Solid electrolyte interface（SEI）solid coating was loaded on the surface of Li metal,which effectively impeded the contact between electrolyte and Li metal and improved the interface stability.LPS can effectively inhibit the growth of lithium dendrites during the battery cycle because of its high interfacial energy.The stable cycle time of the P₂S₅@Li/LPSCl film/P₂S₅@Li symmetric cells at 0.1 m A cm^-2 current density was more than 500 hours.The whole battery was matched with a high voltage cathode of Li Ni_0.8Co_0.1Mn_0.1O₂.At 0.5C,the specific discharge capacity of the first circle was 155 m Ah g^-1.After 400 cycles,the capacity retention rate is 70%.In this paper,two electrolyte modification methods and cathode modification strategies were used to improve the energy density of SEs,also a solvent-free solid interlayer with high interfacial energy was developed to improve the dendrite problem caused by the contact between LPSCl and lithium metal and the soft pack battery was assembled,which has important applications for the practical application of ASSLBs.