Probing Transition Metal Dissolution/Redeposition Dynamics of NMC 900505

Transition metal (TM) dissolution from cathode active material into the electrolyte is a well-documented phenomenon occurring across a variety of cathode active materials. These TM complexes deposit on the anode, damaging the solid electrolyte interphase and leading to irreversible capacity loss. Recent work has demonstrated that these TM species may also redeposit onto the cathode and form part of the cathode electrolyte interphase (CEI). However, the dynamics of this redeposition and its driving forces have not been well studied due to characterization challenges. The goal of our work is to better understand TM dissolution/redeposition (D/R) dynamics in NMC cathode materials spatially and as a function of voltage. Using x-ray fluorescence microscopy, we visualize operando TM D/R dynamics on the surface of an NMC 900505 cathode in an organic electrolyte. Our results show that TM redeposition is spatially anisotropic and varies throughout cycling conditions. This work represents the first operando imaging of TM D/R dynamics of an NMC cathode and provides valuable insights for future work on engineering the CEI of nickel-rich NMCs.