(23c) Foamed Mesoporous Carbon/Silicon Composite Nanofiber Anode for Lithium Ion Batteries

Lithium-ion battery is considered as one of the most promising energy storage and renewable power sources of the next generation. Si-based anode faces adverse issues on electrode pulverization and capacity loss because of the dramatic volume change and stress induction during frequent charging/discharging cycles. Such issues have been successfully mitigated when adopting silicon or carbon in the format of nanowires, or nanotubes, or mesoporous nanoparticles. However, the required synthesis processes are not suitable for scalable manufacturing. We here present a new mesoporous nanofiber Si/C composites synthesis process, in which mesoporous polymer nanofibers were first produced by electrospinning and foaming processes. Silicon nanoparticles are intercalated into carbon nanofibers during the spinning/foaming process. The mesopores and macrovoids inside carbon matrix provides the necessary free space at different scales to accommodate the volume expansion and the consequent stress within the electrode materials to minimize electrode pulverization during alloying process. The hybrid structure of macropores and mesopores also offers high surface-to-volume ratios and facilitate lithium transport between electrolytes and the active materials to achieve high charging/discharging rates. Our electrochemical tests demonstrated higher reversible capacity and better capacity retention with this porous carbon/silicon composite nanofiber anode when compared with that made of nonporous composite nanofibers and carbon nanofibers alone with similar treatment.