Study of Microstructure Change of Carbon Nanofibers as Binder-Free Anode for High-Performance Lithium-Ion Batteries

Flexible and binder-free film of N, O-doped carbon nanofibers (CNFs) is the ideal anode for high-energy-density batteries. Here, CNFs flexible films which the N, O dopant give defect in graphite structure results in high specific surface area more than 500 m2 g–1. A flexible film of CNF800 carbonized at 800 °C delivers initial capacities of 2000 and 755 mAh g–1 at the current densities of 5 and 10 A g–1, respectively. After 500 cycles, CNF800 remains the capacities of 1251, 865, 702, and 305 mAh g–1 at 0.5, 1, 5, and 10 A g–1, respectively. The microstructures of CNFs under various state of charge are studied by HRTEM, XPS, 13C NMR, and so forth. The lithiation/delithiation mainly happens to the interlayer of graphite domain of CNFs. The dopants of nitrogen and oxygen involve in lithiation, but much of Li—N is irreversible. The excellent performances of CNFs film can be attributed to the N, O doped structure of graphite domain that has increased the conductivity and lithium storage ability. Further development of N, O doped CNFs may enable practical applications as flexible anode in high-performance lithium-ion batteries.