A review on ionic conductivity optimization of lithium lanthanum zirconate by multi-element doping strategies for solid state/thin film battery

Abstract

Though effectively used in numerous devices, rechargeable batteries based on existing solution based electrolytes are not considered safe. Additionally, the large size of these devices limits their utilization for mobility devices. Thus, numerous efforts are undergoing to develop energy devices that fulfils the safety and size requirement. This approach involves replacing conventational liquid electrolytes with solid-state electrolytes (SSEs) and advancing their integration into thin film battery configurations. Although batteries utilizing SSE's offer enhanced safety, challenges remain in achieving adequate ionic conductivity, which is almost three to four orders of magnitude lower than that of conventional liquid electrolytes. This poses a great challenge for the development of such batteries. Thus, efforts to optimize the ionic conductivity of these SSE's are underway for numerous rechargeable batteries including Li ion rechargeable batteries (LIB). Development of strategies such as doping into SSE's, design of porous electrolytes and formation of composite with another material are the result of such efforts. In this work, the role of doping strategies is highlighted using lithium lanthanum zirconate (LLZO) as an example. This review also discusses challenges related to stoichiometry, and the site symmetry of dopant ions.