3D Nanocomposite Thin Film Cathodes for Micro-Batteries with Enhanced High-Rate Electrochemical Performance over Planar Films

High energy and high power density rechargeable micro-batteries are a necessity for powering the next generation of flexible electronics, internet of things, and medical technology devices. In theory, significant improvements in the capacity, current and power densities of micro-batteries would result if 3D architectures with enhanced interdigitated component interface areas and shortened ion diffusion path-lengths were used. Further gains are achievable if the materials utilized have high crystalline quality and are preferentially oriented for fast lithium intercalation. In this work, this is achieved by creating epitaxial thin film cathodes comprised of nanopillars of LiMn2O4 (LMO) embedded in a supporting matrix of electronically conducting SrRuO3 (SRO). The first electrochemical study of such a 3D vertically aligned nanocomposite (VAN) that displays clear cathode redox signatures is provided, and demonstrates remarkable capacity retention under high-rate regimes. The electrochemical performance is shown to be dependent on the nanopillar topography, namely the crystallographic orientation, nanopillar dimensions, and electrode/electrolyte interfacial surface area. This work offers a pathway to realizing 3D architectured micro-batteries with high-capacity retention under high-rate conditions enabling fast charge capabilities.