Li Diffusivity and Phase Change in LiFe0.5Mn0.5PO4: AComparative Study using Galvanostatic Intermittent Titrationand Cyclic Voltammetry

Lithium transport and phase evolution in the LiFe0.5Mn0.5PO4 system was examined using both cyclic voltammetry and galvanostatic intermittent titration. Hydrothermal or sol–gel processing was used to synthesize LiFe0.5Mn0.5PO4, LiFePO4, and LiMnPO4, and electrodes made with LiFe0.5Mn0.5PO4 or a 1:1 mass ratio of LiFePO4 and LiMnPO4 were produced and studied. Cyclic voltammetry was used to distinguish single- and dual-phase redox reaction regimes and also accurately measure ionic diffusivity in the dual redox couple LiFe0.5Mn0.5PO4 system. Ionic diffusivity values extracted from galvanostatic intermittent titration data were compared to those determined via cyclic voltammetry.These results are discussed in the context of theories that explain phase transitions and diffusion in this class of materials.