Excess Li compensation powder for production of Li-garnet solid electrolytes

Abstract

Powder covering is a typical Li compensation strategy in Li-garnet solid electrolyte pressureless sintering. The covering powders (CPs) usually have the same composition as the mother powders (MPs), thereby increasing the cost and complexity of electrolyte manufacturing. Herein, a covering powder is proposed; specifically, an excess Li compensation powder (ECP; Li6.4La3Zr1.4Ta0.6O12) replenished with 25 wt% excess Li2CO3. ECP is suitable for electrolytes doped with multiple elements and those with sintering additives; further, it can optimise the microstructure of electrolytes, significantly increasing the relative density and ionic conductivity. The advantageous properties of the ECP can be attributed to the Li2O(g) concentration gradient from the CPs to the electrolyte green body that is produced, which assists electrolyte sintering. Furthermore, the preferential allocation of the sintering system energy to the electrolyte green body originates from the lower surface energy of the ECP, which favours the sintering densification of the green body. The application of ECP has important implications for the low-cost synthesis and performance improvement of Li-garnet solid electrolytes.