Metal-fatigue-resistant thin lithium foil with high depth of discharge for high-performance lithium metal batteries

In Li metal batteries, due to the inadequate resistance to metal fatigue of existing Li foil to withstand the severe strain during charge-discharge cycles, the Li anode is prone to pulverization, which can lead to short circuits or rapid capacity decay of batteries. This issue is further exacerbated in practical high-energy-density batteries that require high discharge depth conditions. To overcome it, a metal-fatigue-resistant thin Li (RMFLi) foil with a stable skeleton has been fabricated by employing a cyclic extrusion compression technique. This RMFLi possesses better metal fatigue resistance than pure Li, maintaining its integrity under cyclic stress and strain without cracking or fracturing. Both finite element simulations (FES) and microscopic morphological characterization provide evidence that the excellent mechanical properties of RMFLi, specifically its resistance to metal fatigue, play a significant role in facilitating controlled dense deposition of Li ions and ensure electrochemical stability of the anode during cycling. Impressively, thanks to its high fatigue resistance and stable skeleton, the RMFLi foil achieves long-term stable cycling even at a discharge depth of up to 90.3%. When paired with high-load lithium iron phosphate (LFP) and S cathodes in full cells, it achieves stable cycling for 1000 and 600 cycles, respectively. It's worth noting that the Li-S pouch cell utilizing this RMFLi foil exhibits high energy density of 391.4 Wh kg⁻¹ and can cycle stably for 80 cycles. This study provides a scalable mechanical preparation method with tremendous expansion possibilities for manufacturing metal-fatigue-resistant thin Li foils.