Modification Of Solid-state Electrolyte-Electrode Interface And Investigation On All-solid-state Lithium Battery Performance

The rapid development of consumer electronics,electric vehicles,and smart grids puts higher demands on current electrochemical energy storage systems.But conventional lithium ion batteries are hard to meet higher energy density and safety both,for being limited by electrode matching,liquid electrolyte components,and battery structure.Thanks to high chemical/electrochemical stability,high thermal stability,and high mechanical strength of solid-state electrolytes?SSEs?,all solid-state lithium batteries?ASSLiBs?are expected to use high-energy cathodes and metallic Li anodes,achieving both high energy density and high safety,which become a hotspot in new energy storage system research.However,studies show that interface issues between SSEs and electrodes are crucial restricting factors in the performance of ASSLiBs.Thus,it has great theoretical and practical value to modify the SSE-electrode interface,as well as achieve high energy density and high safety ASSLiBs.Oxide SSE represented by NASICON structure Li_1.5Al_0.5Ge_1.5?PO₄?₃?LAGP?has high environmental stability,high Li⁺conductivity(5×10^-4 S cm^-1 at room temperature),and easy sintering.However,intrinsic thermodynamic instability and poor contact with electrodes limit the application of LAGP.In this dissertation,the LAGP/Li interface behavior and modification methods were studied.Firstly,the LAGP surface amorphization?LAGP@glass?was adopted to improve the interface stability.With a².7?m amorphous LAGP layer,the LAGP@glass/Li interface exhibits better stability than the LAGP/Li interface,and Li⁺can stably deposit/strip for more than 200 h at the LAGP@glass/Li interface.However,due to the low ionic conductivity of the surface amorphous layer,polarization problem in ASSLiBs ought to be noted.To alleviate the cell polarization,a LAGP/solid polymer electrolyte?LAGP@SPE?double-layer composite electrolyte was designed.Results show that at 60?,Li⁺can stably deposit/strip for 1000 hours at the LAGP@SPE/Li interface under 0.1 mA cm^-2.The LiFePO₄/LAGP@SPE/Li ASSLiB achieves a thousand stable cycles?capacity retention of 96.6%?,a wide operating temperature range?40-100??,high specific capacity(0.1 C,153.4 mAh g^-1),and high safety.This cycle performance is of the top rank in the reported ASSLiBs based on inorganic oxide electrolytes.To further improve the energy density of the LAGP-based ASSLiBs,this dissertation used a cross-linked SPE of NPEG-TGIC to modify the issues of solid-solid contact and poor stability of the LAGP/nickel?Ni?-rich cathode interface.In addition,a three-dimensional?3D?LAGP structure was constructed to increase the loading amount of the cathode materials.The porous-dense bilayer LAGP electrolyte prepared by a template-co-sintering method has a specific surface area of 0.54±0.0757 m² g^-1.With a LiNi_0.8Co_0.1Mn_0.1O₂ cathode loading amount of 13.1 mg cm^-2,3D ASSLiB delivers an area specific capacity of 2.01 mAh cm^-2 at 0.1 C,and the retention of cycle50 cycles is about 70.0%.This interface modification strategy could be a technical guidance for realizing high areal specific capacity ASSLiBs.Sulfide SSE represented by the thio-LISICON structure Li₁₀GeP₂O₁₂?LGPS?has high Li⁺conductivity(>10^-2 S cm^-1 at the room temperature),easy deformation,and good contact with electrodes.However,the narrow electrochemical stability window?1.7 V-2.5 V vs.Li⁺/Li?and thermodynamic instability with metallic Li limit its development.In this dissertation,the stability of LGPS/Li interface was improved by an in-situ LiH₂PO₄ layer formed by the reaction between Li and H₃PO₄.By this LiH₂PO₄ layer,the direct contact between Li and LGPS is avoided,and the interphases penetration towards LGPS is prevented,which results in the fast interfacial Li⁺motion.The LiCoO₂@LiNbO₃/LGPS/LiH₂PO₄/Li ASSLiBs can stably cycle for 500 cycles?retention of 86.7%?with a high specific capacity of 131.1 mAh g^-1.This method may be a reference for the SSEs/electrodes interface behavior investigation and modification research.