Hierarchical electrode design of high-capacity alloy nanomaterials for lithium-ion batteries

Summary Nanomaterials and engineering approaches to assemble these nanomaterials play critical roles in the success of next-generation of high-energy-density electrochemical energy storage devices. As an on-going effort to increase the cycle life and energy densities of lithium-ion batteries, high-capacity alloy anodes, such as silicon, tin, and their alloys have attracted considerable attention due to their high specific capacities (4200 mAh/g for Si, 994 mAh/g for Sn) compared to state-of-the-art graphite materials (372 mAh/g). These alloy materials are made into nano-size materials to achieve their full potential in capacity and life. The high-capacity material is assembled into a polymer laminate composite for a functional lithium-ion cell. However, these alloys experience a large volume change during lithiation and delithiation, which disturbs the electrode integrity, causing its mechanical failure, including delamination from the current collector and cracking of the electrode. Unlike the traditional approach to electrode architecture, new materials and approaches have been developed to assemble nanoparticles into hierarchical structures to achieve high capacity and performance. In this hierarchical approach, polymer electrode binders are a critical component to address the large volume change induced by the high specific capacity during lithiation and delithiation. We summarize the recent explosive development of polymer electrode binders for alloy nanomaterials assembly, along with the remaining challenges in this field.