Fabrication of Nanoporous Aluminum Sheets and Their Application in Sulfide-Based All-Solid-State Battery Anodes

Abstract

Aluminum (Al) is a promising alloy-type anode material for all-solid-state rechargeable lithium (Li) batteries (SSBs) owing to its high theoretical specific capacity, abundance, low cost, and recyclability. However, mechanical degradation during lithiation/delithiation and limited Li diffusion kinetics remain critical challenges in the application of Li–Al alloy (LixAl: 0 < x < 1 at room temperature) in SSBs. This study explores the use of nanoporous aluminum (NPAl) sheets as a potential approach to mitigate these challenges. NPAl sheets were fabricated via a galvanic replacement reaction method, resulting in bundles of Al filaments with an interfilament spacing of ∼200 nm. Compressed NPAl sheets (∼13 μm in thickness and with 17% porosity) were used as anodes and assembled into SSBs utilizing a Li6PS5Cl (LPSCl) solid electrolyte and a Li–In alloy counter electrode. Scanning electron microscopy observations confirmed that the nanoporous structure accommodated volume expansion during initial lithiation and suppressed crack formation upon delithiation. Backscattered electron images suggested that fast surface diffusion promoted long-range Li diffusion within NPAl anodes. Also, the NPAl anode reduced part of the interfacial resistance compared with the dense Al foil anode. Notably, the NPAl anode exhibited a capacity of 618 mAh g–1 (1.97 mAh cm–2) at 0.1 C after 50 cycles at 25 °C. The results suggest that nanoporous architecture leads to distinct mechanical and Li transport behaviors, offering an alternative design strategy for Li–Al alloy anodes for SSBs.