Issues impeding the commercialization of laboratory innovations for energy-dense Si-containing lithium-ion batteries

Silicon is a promising alternative to the conventional graphite anode in high-energy lithium-ion batteries owing to its high gravimetric capacity. However, intrinsic issues, such as severe volume expansion during cycling, have plagued the development of batteries that use Si anodes. While tremendous progress has been made in laboratories to tackle these issues, most Si-containing batteries in industry, in which Si anodes are made of Si suboxides or Si-C composites, can use only a very limited amount of Si. Here we review important factors that affect the practical energy density of Si-containing batteries, including electrode swelling and cut-off voltage in cell operation. We also discuss calendar life, safety and cost issues, which also have a strong influence on practical cell design. Furthermore, we propose testing protocols to evaluate the practical viability of newly developed Si anodes. Substantial gaps exist between laboratory innovations and practical applications of Si-based batteries. Here the authors survey critical factors that hinder the development of practical Si-based anodes and propose testing protocols to evaluate laboratory innovations.