The key is that the SiO thin film behaves as a nanometer-scale material

For the developed negative electrode for lithium-ion secondary batteries, a nanometer-scale thin SiO film was formed on a conductive substrate using vapor deposition and a conductive additive was then layered on this thin film. The new electrode achieves 2000 mAh/g, approximately five times 372 mAh/g for a graphite negative electrode, corresponding almost exactly to the theoretical capacity of SiO (2007 mAh/g). In addition, the developed electrode maintained its capacity even after more than 500 charge-discharge cycles, clearly demonstrating that it displays long life at high capacity. This can be expected to increase the energy density of negative electrodes, and advance the realization of increased capacity and reduced size in lithium-ion secondary batteries.