Facile synthesis of Si@void@C nanocomposites from low-cost microsized Si as anode materials for lithium-ion batteries

High-capacity anodes, such as Si, are much more attractive than graphite for next generation lithium-ion batteries (LIBs) due to their high theoretical storage capacity. However, successful practical applications of Si anodes in high energy density LIBs are hindered by the huge volume change during cycling, which causes the active material pulverization and unstable solid electrolyte interphase films. In this study, we successfully synthesized Si@void@C nanocomposites from commercial low-cost microsized Si via a combination of facile high-energy mechanical milling, resorcinol-formaldehyde resin coating and sodium hydroxide etching. The as-prepared Si@void@C consists of nanosized Si particles fully embedded into mesoporous carbon shells with abundant voids. The Si@void@C anodes exhibit a high reversible capacity of 1088 mAh g(-1) over 300 cycles at a rate of 500 mA g(-1). Even at a much higher current density of 8 A g(-1), the Si@void@C anodes can still deliver a high reversible capacity of 714 mAh g(-1). These outstanding performances are assigned to the nanosized Si that is able to alleviate mechanical strain, and the buffering effect of mesoporous carbon shells as well as abundant voids for Si volume expansion. The synthesis process is simple, scalable, and cost-effective, providing a promising alternative way to large-scale production of inexpensive high-performance silicon-based materials for next-generation LIBs.