Volume expansion restriction effects of thick TiO2/C hybrid coatings on micro-sized SiOx anode materials

In this work, novel SiOx anode materials with low volume expansion and high ionic/electrical conductivity are designed by combining internal buffer space and external super thick TiO2/C hybrid shell of 200-400 nm. An electrochemical reaction visualizing confocal system is originally developed for characterizing electrode thickness changes, and the real-time quantitative change of electrode thickness during charging and discharging is realized. Surprisingly, the maximum thickness expansion of designed anodes with the specific capacity of 1006.2 mA h g(-1) is only 37% in the first lithiation process. Subsequently, the designed anodes present stable cycle life of the capacity attenuation of 7.83% after 100 cycles compared with the capacity of 5th cycle. It demonstrates that the designed thick TiO2/C hybrid coatings effectively swing the expansion stress of micro-sized SiOx to internal space. This work proves that the huge volume expansion of micro-sized SiOx particles can be controlled by reasonable design of surface hybrid coatings and bulk structure, and the long lifespan can be maintained. This strategy paves a way for the development of micro-sized SiOx anode materials with long cycle life and good process ability for high energy density lithium-ion batteries.