Ultralong cycling stability of carbon-nanotube/LiFePO4 nanocomposites as electrode materials for lithium-ion batteries

Abstract

We developed a method to make CNTs fully coated by polyvinylpyrrolidone (PVP), which acts as an agent to effectively combine CNTs and LiFePO4 to form a nanocomposite. In this nanocomposite, unbreaking and non-entangling CNTs forms a highly conductive 3D CNTs network that can significantly improve both the electrical conductivity of LiFePO4 and the diffusion coefficient of Li ions and electrons. As a result, our CNTs/LiFePO4 nanocomposite exhibited an excellent high-rate capacity and an ultralong cycling stability, i.e., a high discharge capacity of 123mAhg−1 and an extremely low loss in capacity of 1.6% could be achieved after 1000 cycles at 10C. A capacity of ∼100mAhg−1 (corresponding to a capacity retention of 80%) could still be achieved after 3400 cycles at 10C. The loss in capacity of our LiFePO4/CNTs is ∼four to eight times smaller than that of previously studied LiFePO4/CNTs and LiFePO4/graphene nanocomposites. Our simple but powerful synthetic techniques should be beneficial to the application of lithium-ion batteries based on LiFePO4 electrode materials in such electric vehicles as PHEVs, AEVs, and HEVs.