All Solid State Li-Ion Batteries Based on Cubic Garnets: From Material Optimization to Thin Film Battery Design

The next generation of energy storage devices relies on a broad and adaptable range of volumetric and gravimetric energies to compete with the challenges in stationary, mobility and portable electronic electricity supply. Here, all solid state batteries based on Li-garnet-based structures are interesting model systems as these allow for complete solid state battery types that: i.) can partially use industrial waste heat to increase charging times (increased Li⁺ diffusion) for stationary, ii.) with new high capacity electrode materials which show conventionally a low stability in standard liquid/polymer based Li-batteries, iii.) are easy transferrable to model thin film battery structures for powering of portable electronics on chip.

Firstly, we report on Al:Li_7-2xLa₃Zr₂O₁₂ bulk pellet and thin film processing, their crystallization and ionic transport characteristics. Secondly, from a materials processing perspective we report on a new modified sol-gel synthesis-combustion method to lower the nano-particle production of the solids to ~ 600°C. Here, we exemplify stable electrolyte compounds based on Li_7-3x(Ga_x)La₃Zr₂O₁₂. Thirdly, for N-site doping Li_7-xLa₃Zr_2-xTe_xO₁₂ with x = 0.25 to 0.35 were prepared by synthesis in solid state, and Te is studied as alternative to Ga and Al stabilizers as battery electrolyte without grain boundary stabilization.

Finally, we concluded on the suitability of these new materials for scaling down to thin film microstructures, as potential Li-garnet electrolytes in all solid state batteries for portable electronic applications. First strategies on how to design optimum thin film-microbatteries adaptable to chemo-mechanical variations during operation will be shown. Here, two different model designs are described: (i.) the fabrication of microbattery dot arrays and (ii.) wrapped anode/electrolyte/cathode microstructures with tunable strain.