<i>In Situ</i> Probing Potassium-Ion Intercalation-Induced Amorphization in Crystalline Iron Phosphate Cathode Materials

Na-ion and K-ion batteries are promising alternatives for large-scale energy storage due to their abundance low cost. Intercalation of these large ions could cause irreversible structural deformation partial complete amorphization in the crystalline electrodes. A lack understanding dynamic changes amorphous nanostructure during battery operation is bottleneck further developments. Here, we report utilization in-operando digital image correlation XRD techniques probe phase iron phosphate potassium ion intercalation. In-operando demonstrates electrode's first charge discharge cycle. Additionally, ex situ HR-TEM confirms after potassium-ion An strain analysis detects reversible deformations associated with redox reactions phases. Our approach offers new insights into mechanism intercalation which highly potent development next-generation batteries.