In operando observation of temperature-dependent phase evolution in lithium-incorporation olivine cathode

Abstract

LiFePO4 is one of the most outstanding cathodes for the high performance lithium-ion battery, while it is restricted by its unsatisfactory low temperature performance. Here we detect the structural dynamics and reaction routes of LiFePO4 via operando condition with high rates, well reproducibility over cycles and low temperature in common laboratory X-ray without the synchrotron light source. The intermediate phases between LiFePO4 and FePO4, driven by the overpotential and limited ion transfer rate along the b direction at low temperature, are captured. Our results demonstrate that the existence of intermediate can greatly improve the diffusion kinetics of LiFePO4. The deep understanding of reaction routes of LiFePO4 at low temperature will guide the further material optimization design. Besides LiFePO4, such high time resolution in-situ X-ray diffraction testing method with laboratory source is available to understand the reaction mechanisms of other electrochemical reaction system.