Structure and electrochemistry of FePO4·2H2O hydrate

We report the structural and electrochemical characteristics of FePO4 dihydrate exhibiting a monoclinic structure (P21/n space group). We have applied Raman and FTIR spectroscopy to study the local structure. Vibrational features analyzed using the molecular group model show the strong inductive effect in the [FePO4] framework. The electrode FePO4·2H2O material inserts 0.7 Li ions per mole leading to coulombic efficiency of 74% for the first cycle and specific capacity of 106 mAh g−1. Infrared spectrum of the lithiated product shows structural modifications due to the lithium insertion and the reduction of iron ions.