On the interfacial properties of the garnet-type electrolyte ceramic pellets of cubic Li6.4La3Zr1.4Ta0.6O12: A comprehensive improvement of the sintering additive of Li-ion conducting LiCl

Abstract

The garnet-type Li fast ion conductor of cubic Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is one of the most promising solid-state electrolytes for safety-critical lithium-ion batteries, and the involved interfacial problems of LLZTO ceramic pellet must be alleviated prior to practical application. In this paper, the low-melting-point Li-ion conductor of LiCl is chosen as a sintering additive of LLZTO crystallites to address its positive effect on the structural properties of 1140°C-sintered LLZTO - x wt% LiCl (x = 0, 2, 4, 6 and/or 8). Through the physically filling into inter-particle gaps and chemically anchoring onto LLZTO particles' surface, an optimal mass fraction of LiCl (4 wt%) makes the resulting ceramic pellet to acquire a room-temperature ionic conductivity of 3.66 × 10−4 S cm−1, and the corresponding Li–C/LLZTO - 4 wt% LiCl/Li–C or Li–C/LLZTO - 4 wt% LiCl/LiCoO2 cell is endowed with a high critical current density (2.00 mA cm−2) or a good cycling stability at 20 mA g−1 within 2.5–4.2 V (e.g., discharge capacity - 124.4/91.1 mAh g−1, the 1st/100th cycle). Aside from these, a plausible mechanism of the agglutinant's actions suggests an effective approach to the further development of LLZTO-based all-solid-state lithium-ion batteries in future.