Operando monitoring of charging-induced defect formation in battery electrodes by positrons

The defect specific technique of positron-electron annihilation is utilized in an appropriate electrochemical cell for operando monitoring of vacancy-type defect formation which occurs in battery electrodes upon charging, using the cathode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a case study. The variation of the positron lifetime with charging-induced Li ion extraction indicates the formation of divacancies and vacancy agglomerates in a progressive amount as well as a reordering of vacancy agglomerates to one-dimensional vacancy chains at the end of charging. A remarkable correlation of the charging-induced variation of the positron lifetime with that of Li ion diffusion data in the literature has been found.