Rate dependent multi-mechanism discharge of _Ag0.50VOPO₄· 1.8H₂O: Insights from In Situ Energy Dispersive X-ray Diffraction

_Ag0.50VOPO₄· 1.8H₂O (silver vanadium phosphate, SVOP) demonstrates a counterintuitive higher initial loaded voltage under higher discharge current. Energy dispersive X-ray diffraction (EDXRD) from synchrotron radiation was used to create tomographic profiles of cathodes at various depths of discharge for two discharge rates. SVOP displays two reduction mechanisms, reduction of a vanadium center accompanied by lithiation of the structure, or reduction-displacement of a silver cation to form silver metal. In-situ EDXRD provides the opportunity to observe spatially resolved changes to the parent SVOP crystal and formation of Ag⁰ during reduction. At a C/170 discharge rate V⁵⁺ reduction is the preferred initial reaction resulting in higher initial loaded voltage. At a discharge rate of C/400 reduction of Ag+ with formation of conductive Ag⁰ occurs earlier during discharge. Discharge rate also affects the spatial location of reduction products. The faster discharge rate initiates reduction close to the current collector with non-uniform distribution of silver metal resulting in isolated cathode areas. The slower rate develops a more homogenous distribution of reduced SVOP and silver metal. This study illuminates the roles of electronic and ionic conductivity limitations within a cathode at the mesoscale and how they impact the course of reduction processes and loaded voltage.