混合工艺对氧化物/硫化物复合固态电解质电化学性能的影响

With the widespread development of new energy vehicles, all-solid-state batteries have attracted wide attention because of their high safety and high energy density. The oxide/sulfide solid electrolyte is expected to combine the low grain boundary resistance, room temperature workability and low interfacial resistance of sulfide with the excellent electrochemical stability and low cost of oxides. However, the lack of reliable preparation techniques for composite solid electrolytes with higher oxide content limits the further reduction of cost and the further improvement of stability. In this work, Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP)/Li₈P₂S₉ (LPS) electrolyte was employed as an example system for the synthesis of sulfide-based solid electrolyte with high oxide content via grinding and subsequent hot compressing. The LATP and LPS was mixed through normal grinding (Gr), low speed ball grinding (LB) and variable speed ball grinding (VB). The results showed that grain refinement of oxide and the decrease of pore content were achieved by VB. In addition, the distribution of S and Ti elements proved that LATP was uniformly dispersed in the VB-LATP/LPS (LATP/LPS prepared by VB). According to the Х-ray diffraction (ХRD) pattern, the distortion of LATP and LPS lattice in VB-LATP/LPS was attributed to the mutual diffusion of oxygen and sulfur atoms at the interface. As a result, VB-LATP/LPS exhibited high lithium ion conductivity (3.35 mS•cm^－1), low electron conductivity (1.53×10^－8 S•cm^－1) and relatively low lithium ion migration activation energy (11.75 kJ•mol^－1) at room temperature. Besides, the good interfacial bonding state and addition of hard oxides contributed to the high stability of the electrolyte/lithium interface. Furthermore, the all-solid-state battery assembled by VB-LATP/LPS showed a high capacity retention rate of 99% after 100 cycles, demonstrating excellent electrochemical stability. Such synthesis idea of combination with soft sulfide electrolyte and hard oxide electrolyte provides a feasible strategy for the synthesis of cost effective composite solid electrolytes.