Abstract
Metal fluorides are potential candidates as electrode materials for rechargeable batteries. During the electrode fabrication, however, thermal treatments can cause decomposition of thermally instable compounds. Here, we showed that during the electrode processing of CoF3, the carbon and PVDF additives act as a protective layer that prevents CoF3 to readily decompose into CoF2 (rutile). We found that instead, it decomposes into an intermediate phase with a corundum like structure featuring Co vacancies, i.e., Co1.26IICo0.16III□0.58F3 where □ represents the vacancies. The structural analysis was possible owing to the use of the pair distribution function.