Practical implementation of Li doped SiO in high energy density 21700 cell

SiO is a promising negative electrode material to increase Li-ion batteries specific energy thanks to its high capacity and stability. However it needs to be blended in low amounts with graphite because of its poor first cycle efficiency. Here we implement new Li doped carbon coated SiO material that overcomes this limitation and enables higher energy density cells. Reference SiO grade is compared to pre-lithiated materials and SiO content up to 20% blend with graphite are evaluated in pouch and 21700 cells with more than 500 cycles obtained at 90% depth of discharge. Reaction mechanism is proposed for standard as well as pre-lithiated SiO, and generalized for SiOx. Finally we discuss behavior in hard casing full cell using this simple model to calculate volume expansion. We show with steric consideration that 40% SiO is likely the ultimate ratio practically useable in cylindrical cells. •Li doped carbon coated SiO is implemented in industry representative 21700 cell.•Influence of SiO content in negative electrode is evaluated up to 20%wt.•A reaction mechanism is proposed for SiOx to calculate volume expansion.•Maximum allowed SiO–C content in 21700 cell is discussed based on this calculation.