Thin Film Solid State Li-Ion Batteries as Model Systems for Understanding Interface Effects

Rechargeable, thin film solid-state Li and Li ion batteries (TFSSLBs) with high specific power and energy density are highly desirable to energize an emerging class of miniature, autonomous microsystems that operate without a hardwire for power or communications. TFSSLBs are also attractive for fundamental studies aimed at understanding how battery geometry, dimensions, composition and the resulting interfaces affect performance. For example, thin film fabrication methods enable precise control over electrode and electrolyte thickness, morphology, geometry and interface area. Furthermore, TFSSLBs are vacuum compatible, meaning that techniques that generally require vacuum or controlled ambient such as SEM, TEM, auger electron spectroscopy, secondary ion mass spectroscopy, neutron depth profiling and Kelvin probe force microscopy can be readily applied to characterize TFSSLB, often in operando mode. In my presentation, I will discuss recent experiments aimed at precisely measuring the Li concentration and electric potential profiles across TFSSLBs. When coupled with first principles informed models, the results provide new insights into the factors that determine electrode/electrolyte interface resistance and to materials selection strategies for achieving stable, high performance solid state batteries.