Waterbed inspired stress relaxation strategies of patterned silicon anodes for fast-charging and longevity of lithium microbatteries

Over the past 20 years, silicon (Si) has been an investigated anode material for lithium-ion batteries due to its high capability. However, the large strain evolution during lithiation/delithiation that leads to pulverization and delamination has hindered its industrial realization. Effectively suppressing the stress evolution that arises in Li-Si alloy reactions has been an endless debate. Recently, multiscale pattern technologies have been demonstrated on activated materials and current collectors to achieve better performance, especially in terms of lifetime. Our pattern strategy is inspired by the structure of "waterbeds", where individual Si islands were surrounded by buffer walls to accomplish stress relaxation. We developed an advanced pattern technique based on lithiated polyacrylate acid (LiPAA) for its bi-functionalization of adhesion and viscoelasticity with Si to better accommodate the mechanical stress, especially at high-rates. Ultimately, we demonstrate longevity performance with almost "zero-loss" over 200 cycles at 1C and an excellent rate retention of 26.7% at 20C. We systematically analyze the diffusivity of Li-ions in various patterned Si anodes to explain the fast-charging and the long-term cycling properties. This facile fabrication of a unique pattern structure can provide new strategies for the rational design of various thin-film materials that suffer from the volume change issue during battery operation. Our pattern strategy draws inspiration from the structure of "waterbeds", achieving stress relaxation, thereby enabling fast-charging capabilities and ensuring the longevity of lithium microbatteries.