Research On Materials Design And Their Performances In Sulfide-Based All-Solid-State Lithium Batteries

All-solid-state lithium batteries（ASSLBs）are considered one of the ideal energy storage devices for the next generation,as they are expected to fundamentally address the current issues of poor safety and low energy density in liquid lithium-ion batteries.Sulfide electrolytes still face many challenges,including poor air stability,incompatibility with electrode materials,thick electrolyte layers,and difficulty in suppressing lithium dendrite growth.In this study,we focus on sulfide electrolytes and propose modification strategies such as doping and composite design as well as interface optimization to address the above challenges:（1）Li₆PS₅Cl was selected as the research subject,and Sb₂S₅ was used as a dopant to prepare Sb-doped Li₆P_1-xSb_xS₅Cl electrolyte.The prepared Li₆P_0.925Sb_0.075S₅Cl exhibits an ultra-high ionic conductivity of 3.6 × 10^-3 S cm^-1.Due to the formation of thermodynamically stable SbS₄^3-tetrahedra within the electrolyte,Li₆P_0.925Sb_0.075S₅Cl shows excellent structural stability and resistance to hydrolysis when exposed to moist air or water.In addition,the electrolyte can form an in-situ Li-Sb alloy at the anode interface,which effectively reduces the Li⁺diffusion barrier at the interface and regulates the deposition/stripping behavior of Li⁺,thereby significantly improving the interface compatibility with metallic lithium and the ability to suppress lithium dendrites.The assembled Li/Li₆P_0.925Sb_0.075S₅Cl/Li symmetric cells exhibit a high critical current density(1.2 mA cm^-2)and excellent lithium symmetric cycling stability(stable cycling over 800 h at 0.1 mA cm^-2).The assembled LNO@NCM523/Li₆P_0.925Sb_0.075S₅Cl/Li ASSLBs display excellent cycling stability,providing an initial discharge capacity of 129.9 mAh g^-1 at 0.2C,and maintaining a capacity retention rate as high as 82.6%.The ASSLBs assembled on the basis of Li₆P_0.925Sb_0.076S₅Cl after air exposure also present excellent electrochemical performance.（2）A low-cost and non-toxic Bi₂O₃ was further used as a co-dopant for Li₆PS₅Cl to design Li_6+2xP_1-xBi_xS_5-1.5xO_1.5xCl electrolytes.Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl was prepared and demonstrated a high ionic conductivity(3.4 ×10^-3 S cm^-1)and excellent air stability.The mechanism of the Bi,O dual-doping on the air stability was systematically analyzed from the thermodynamic and kinetic perspectives based on theoretical calculations.The results show that O doping improves the resistance of the electrolyte to water adsorption and slows down the reaction rate with water,while Bi doping results in the formation of BiS₄^3-tetrahedra that are thermodynamically stable against water within the electrolyte.Both factors synergistically enhance the air stability of Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl electrolyte.By analyzing the interfacial components of the Li/Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl/Li symmetric cells after cycling,it was found that the Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl electrolyte induces the formation of a Li-Bi alloy at the anode interface,which plays a key role in reducing the Li⁺diffusion barrier and improving the interfacial compatibility,thus significantly enhancing the ability to resist lithium dendrites.The assembled Li/Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl/Li symmetric cell exhibits a high critical current density(1.1 mA cm^-2)and excellent cycling stability(stable cycling over 200 h at 1 mA cm^-2).The assembled LNO@NCM523/Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl/Li ASSLBs show an initial discharge capacity of up to 139.4 mAh g-1 at 0.1C and good stability（88.6%capacity retention after 60 cycles）.The ASSLBs assembled on the basis of Li_6.04P_0.98Bi_0.02S_4.97O_0.03Cl after air exposure also present excellent electrochemical performance.（3）Li₁₀GeP₂S₁₂（LGPS）was selected as the research object to prepare a 60μm thick 5PEO-100LGPS-5CTMS+NM sulfide-based composite electrolyte membrane by compounding it with a small amount of polyethylene oxide（PEO）and dispersant（3-chloropropyl）trimethoxysilane（CTMS）,and using nylon mesh（NM）as the supporting skeleton material.Such thin film exhibits a high room temperature ionic conductivity(2.4 ×10^-4S cm^-1),a wide electrochemical window（4.7 V vs Li⁺/Li）,outstanding thermal stability,and excellent mechanical strength（13.8 MPa）.Furthermore,a fluorine-rich gel protective layer（Gel-Li）was constructed on the lithium metal surface via an in-situ solidification process,which greatly enhances the interfacial stability between the sulfide-based composite electrolyte film and lithium metal and its ability to inhibit lithium dendrite.Lithium symmetric cells show long cycling stability(stable cycling over 400 h at 0.1 mA cm^-2).Both the assembled MWCNT@S/5PEO-100LGPS5CTMS+NM/Gel-Li and LNO@NCM622/5PEO-100LGPS-5CTMS+NM/Gel-Li cells exhibit excellent cycling performance and rate capability.