SiO –graphite as negative for high energy Li-ion batteries

Negative electrodes containing SiOx were investigated as alternative negative electrodes to carbon for Li-ion batteries. The results obtained on the effect of binders and carbon additives on the electrochemical performance (i.e., reversible capacity, coulombic efficiency, charge–discharge rate capability) of the SiOx–graphite electrode and SiOx electrode are presented. SEM analysis that utilizes facilities for in situ and ex situ studies were applied to better understand the performance and cycle life of the SiOx-based electrodes. The SEM analysis clearly showed that the SiOx particles expand and contract during charge–discharge cycling, and that some of the particles undergo mechanical degradation during this process. The SiOx–graphite electrode with polyimide binder exhibited a stable capacity of 600 mAh g−1 during high-rate charge–discharge from C/4 to 1C. These results suggest that the use of a flexible binder like polyimide and reasonably small SiOx particles (nano-particles) facilitates improved cycle life and higher rate capability.