Defect-Enhanced Lithium Storage Performance of Nanostructured Mesoporous LiFePO4 for a High-Power Lithium-Ion Battery

Abstract

Mesoporous materials have received growing interest, particularly as electrode materials for lithium-ion battery applications since they provide short transportation length for Li ion and electrons, and favour electrolyte wettability. Such unique features are highly beneficial for improving the electrochemical performance of olivine LiFePO4 as this material has intrinsically low electronic and ionic conductivities, which otherwise would affect the storage performance. In addition, this sluggish kinetic brings about huge polarisation specifically at high current rates, resulting in poor energy efficiency. In order to overcome such kinetic issues, we present here a facile soft template-solvothemal method to synthesise mesoporous LiFePO4. Such mesoporous LiFePO4 is made of well interconnected nanograins (20–30 nm) which exhibits excellent storage performance and long-term cycling stability. In particular, the material shows improved storage performance at high rates with significantly less polarisation and clear signature of voltage plateaus for both Li ion insertion-extraction processes. In comparison with the LiFePO4 synthesized by the soft template method, the mesoporous LiFePO4 demonstrates excellent storage performance. This is attributed to the 2-D diffusion of both Li ions and electrons along b- and c-axes consistent with the 2-D Li ions transport reported previously for LiFePO4 single crystal.