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

Highlights: • A highly effective 3D conductive network was fabricated in LiFePO₄ electrode materials. • The electrode displays extremely low loss in capacity of 1.6% at 1000 cycles. • The electrode exhibits an ultralong cycling stability of 80% after 3400 cycles. - 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 123 mAh g⁻¹ and an extremely low loss in capacity of 1.6% could be achieved after 1000 cycles at 10C. A capacity of ∼100 mAh g⁻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.