The rapidly growing Li-ion battery market has generated considerable demand for Li-ion batteries with improved performance and stability. All-solid-state Li-ion batteries offer promising safety and manufacturing enhancements. Herein, we examine the effect of substitutional doping at three cation sites in garnet-type Li7La3Zr2O12 (LLZO) oxide ceramics produced by a sol-gel synthesis technique with the aim of enhancing the properties of solid-state electrolytes for use in all-solid-state Li-ion batteries. Building on the results of mono-doping experiments with different doping elements and sites-Al, Ga, and Ge at the Li+ site; Rb at the La3+ site; and Ta and Nb at the Zr4+ site-we designed co-doped (Ga, Al, or Rb with Nb) and tri-doped (Ga or Al with Rb and Nb) samples by compositional optimization, and achieved a LLZO ceramic with a pure cubic phase, almost no secondary phase, uniform grain structure, and excellent Li-ion conductivity. The findings extend the current literature on the doping of LLZO ceramics and highlight the potential of the sol-gel method for the production of solid-state electrolytes.
Keywords: all-solid-state battery; co-doping; doping; garnet oxide; lithium-ion battery; solid state electrolyte; sol–gel; tri-doping.