All-solid-state lithium batteries featuring hybrid electrolytes based on Li+ ion-conductive Li7La3Zr2O12 framework and full-concentration gradient Ni-rich NCM cathode

Abstract

Solid hybrid electrolytes (SHE) composed of Li+-conductive oxides and polymer electrolytes combine the beneficial properties of ceramic and polymeric materials. In this study, we designed and synthesized a three-dimensional Li6.4La3Zr2Al0.2O12 (LLZO) framework with a continuous ion-conduction pathway. This 3D framework was hybridized with a poly(Ɛ-caprolactone)-based solid polymer electrolyte to obtain a free-standing and flexible film for an all-solid-state lithium battery. The hybrid electrolyte exhibited high ionic conductivity, good mechanical strength, a high transference number, and excellent electrochemical stability compared with those of solid polymer electrolytes. Symmetric Li/SHE/Li cells exhibited good cycling stability without short-circuiting, indicating a uniform plating/stripping of lithium and good interfacial properties toward lithium metal. LiNi0.78Co0.10Mn0.12O2 with a full-concentration gradient (FCG78) was synthesized and investigated for applications in all-solid-state batteries. Coupled with the unique compositional and morphological properties of FCG78, the all-solid-state Li/FCG78 cell featuring SHE delivered a high initial discharge capacity of 172.4 mAh/g and exhibited good cycling stability with a capacity retention of 84.3 % after 200 cycles at 0.5 C. Our results demonstrate that the solid hybrid electrolyte based on the Li+-conductive LLZO framework combined with a full-concentration gradient Ni-rich layered NCM cathode are promising materials for designing all-solid-state lithium batteries.