(Invited) Extend Calendar Life of Si Based Li-Ion Batteries

Abstract

Although significant progress has been made in increasing the specific energy and cycle life of silicon (Si) based Li-ion batteries (Si-LIBs), calendar life of these batteries is still less than two years, which is far less than the 10 year life-time required for electrical vehicle applications.1 Graphite anodes undergo only ~10% volume change during cycling, so SEI formed during the initial process does not experience significant mechanical stress during the subsequent cycles. However, the SEI layer formed on Si anodes experiences tremendous mechanical stress during repeated cycles. Most SEI layers formed on the Si surface in conventional electrolytes break down, exposing fresh, lithiated Si or SiO to electrolyte. Thus, significant Si corrosion and electrolyte consumption continuously occur during battery storage, especially in the fully lithiated conditions and elevated temperatures required for the accelerated calendar life test.2 As a result, the impedance of the Si anode will increase much faster than a graphite anode and shorten its calendar life, as observed in nearly all Si-LIBs. In this work, we will report the results of our recent investigation on the fundamental mechanism behind the limited calendar life of Si-LIBs. Several approaches that alleviated degradation of SEI layer and increasing cycle life of Si-LIBs will be discussed, including the nanostructured Si designs that can minimize the external size expansion, minimized particle surface area, and formation of stable SEI layers by localized high concentration electrolyte tailored for Si anode. The combination of these methods can largely extend the calendar life of Si-LIBs and accelerate the application of these batteries for large-scale electrical vehicles and consumer electronics applications.