Understanding Thickness-Dependent Transport Kinetics in Nanosheet-Based Battery Electrodes

There is a growing need for thicker electrode designs to achieve high energy/power for ever-increasing power needs by electronic devices and electric automobiles. Though great efforts, such as structure optimization, have been devoted on fabricating thick electrodes, understanding of performance-limiting factors essential to electrode architecture design, has not been well established. In this study, the dependence of electrochemical behavior on electrode mass loading is comprehensively investigated in nanosheet-based electrodes. In particular, the effects of electrical conductivity and porosity are illustrated. In drop-casted electrodes, where nanosheets are highly stacked, ionic diffusion in the electrolyte has been determined to be the controlling step in electrodes with high thickness. To overcome the limitation of such sluggish ionic transport, a facile ice-templating strategy was employed to create vertically aligned channels, offering fast-diffusion pathways for the Li ion in the electrolyte. Impressively, the ice-templated electrodes exhibit a specific capacity of 144 mA h g–1 at 0.2 C and retain 83 mA h g–1 at 10 C with high mass loading ∼10 mg cm–2. The enhanced ion transport kinetics was verified by various electrochemical and structural characterizations. This work demonstrates the thickness scaling effect of nanosheet-based electrodes and highlights the importance of promoting ionic transport and electrolyte access for designing thick electrodes.