Study On Lithium Ion Transport And Interface Stability Of CsPbX₃ Perovskite Reinforced PEO Polymer Electrolytes

All solid-state lithium metal batteries are expected to become the revolutionary system of the next generation of high safety and high energy density batteries.Polymer solid-state electrolytes have significantly better comprehensive performance than traditional liquid electrolytes,providing a broad development prospect for the final realization of all solid-state lithium metal batteries.However,the intrinsic low ion transport rates and poor interface stability are still the key bottlenecks of their commercialization.Aiming at the above problems,this paper proposes a strategy of CsPbX₃（X=Cl,Br,I）perovskite enhanced PEO polymer electrolytes,and studies the mechanism of improving lithium ion transport and interface stability.The main research contents are as follows:（1）A new strategy of modifying PEO polymer electrolytes with CsPbX₃ perovskite quantum dots as nanofillers is proposed.Perovskite quantum dots inhibit polymer crystallization and Lewis acid-base interactions,resulting in significantly improved ion transport performance of the modified PEO electrolytes.The room temperature ionic conductivity increased from 5×10^-6 S cm^-1 to 1×10^-4 S cm^-1 and the lithium ion transference number improved from 0.19 to 0.55.Combined with the synergistic effect of interface engineering,the cycle stability of Li symmetric batteries and LiFePO₄ all solid-state lithium metal batteries modified by perovskite quantum dots is greatly improved.（2）The mechanism of performance enhancement of PEO-CsPbI₃ polymer electrolytes system was thoroughly investigated by combining various characterization and testing methods.The results show that the introduction of CsPbI₃ perovskite quantum dots can improve the number and mobility of free lithium ions,so as to improve the key performance indicators such as ion conductivity and lithium ion transference number of electrolyte.In addition,fast ion transport can make the distribution and deposition of lithium ions more uniform,reduce the concentration gradient and inhibit the formation of lithium dendrites,so as to improve the interface compatibility between electrolyte and electrode.The modified Li symmetric battery can stably cycle for more than 1000 h at a current density of 0.3 m A cm^-2.（3）One dimensional CsPbI₃ perovskite nanowires were constructed and their modification effect on PEO electrolytes was studied to solve the problem that zero dimensional quantum dot particles are easy to agglomerate and form cross junctions to hinder ion conduction.The room temperature ionic conductivity and lithium ion transference number of PEO polymer electrolytes modified by CsPbI₃ perovskite nanowires were increased to1.66×10^-4 S cm^-1 and 0.61,respectively.In addition,the one dimensional structure of perovskite nanowires can realize the mechanical strengthening of polymer matrix and effectively prevent the growth of lithium dendrites.The Li symmetric battery can stably cycle for more than 400 h at a current density of 0.5 m A cm^-2.LiFePO₄ full batteries can maintain high coulomb efficiency and high specific capacity at the rate of 0.8C,and cycle stably for more than 200 cycles.