Directed Transport as a Route to Improved Performance in Micropore-Modified Encapsulated Multilayer Silicon Electrodes

Energy storage is an increasingly critical component of modern technology, with applications that include energy infrastructure, transportation systems, and portable electronics. Improvements to Lithium-ion battery energy/power density through the adoption of silicon anodes-promising both gravimetric and volumetric capacities that far exceed traditional carbon-based anodes-has been limited by ~300% strains and poor coulombic efficiency during charge and discharge ((dis)charge) cycling which result in short operational lifetimes. We examine encapsulated micropore-modified silicon anodes that define lithium mass-transfer dynamics to constrain strain evolution and improve capacity retention during (dis)charge cycling. Fully integrated cells incorporating this silicon anode and a commercial grade LiCoO₂ cathode maintain their capacity for 110 cycles with >99% average coulombic efficiency from cycles 5 to 100. Anodes with thicknesses up to 50 μm resulted in area-normalized capacities of up to 12.7 mAhcm^-2. When the silicon anode microstructure pitch is varied, a direct relationship is found to exist between the rate capability and volumetric capacity of the anode. Helium-ion Microscopy, Secondary Ion Mass Spectrometry, and Scanning Electron Microscopy, used as ex-situ characterization methods for the evolution of the electrode's structure on cycling, reveal significant changes in nanoscale morphology that otherwise retain the essential laminate micropore motif of the initial Si anode.