Role of carbon nanotube film interlayer for Li-free all-solid-state battery

Abstract

Anode-free solid-state batteries (AFSSBs) are regarded as a next-generation battery technology due to their high gravimetric/volumetric energy densities and safety. Recent studies suggested that AFSSBs require an interlayer between the current collector and solid-state electrolyte to prevent non-uniform flux and side reactions with deposited Li. Carbon nanotubes (CNTs) are effective interlayers thanks to their high Li-ion diffusivity, good chemical stability, and great mechanical strength. Nevertheless, a detailed understanding of the influence of CNT interlayer is crucial for advancing AFSSB research. Herein, the role of the CNT film interlayer on Li deposition was explored through elemental mapping analyses at various states of charge and molecular dynamics (MD) simulations. According to the results, the nano-porous CNT interlayer promotes uniform Li distribution, which improves the battery performance. Moreover, MD simulations indicate that Li atoms attach to the CNT bundles without significant aggregation, meaning that Li moves toward the current collector. It is assumed that Li diffusion through the interlayer during cycling is likely driven by two mechanisms, which are concentration gradient and electric field. This study is anticipated to serve as a foundational reference for future research on lithium diffusion in the interlayer in all-solid-state batteries (AFSSBs).