Carbonate‐ Versus Hydroxide‐Based Precursor for the Synthesis of Li/Mn Rich Cathodes: Exploring Differences in Discharge Capacities and Cycle Life
Pranti Sutar, Johannes Helmut Thienenkamp, Laurin Profanter, Tim Messink, Annalena Krude, Uta Rodehorst, Hyuck Hur, Gunther Brunklaus, Dominik Voigt, Martin Winter, Johannes KasnatscheewLithium/manganese‐rich (LMR)‐based cathodes can enhance the specific energy of Li ion batteries and are conventionally synthesized via a carbonate‐based precursor (LMR‐CO 3 ). The CO 2 evolution‐related voids and enhanced surface area can be avoided by calcination of a hydroxide‐based precursor [LMR‐(OH) 2 ]. This way, the LMR releases less oxygen during charge, as seen by a decreased Mn 3+/4+ redox activity and decreased voltage fade. However, the lower specific discharge capacity is attributed to a decreased lithiation amount in the initial cycles for LMR‐(OH) 2 and is related to a higher Li + extraction degree, that is, a higher redox oxidation number at the discharged state. Interestingly, this decreases the accompanying amount of detrimental Mn 3+ and is concluded to improve cycle life, due to, for example, minimized Jahn–Teller distortions and disproportionation reactions. The differences in lithiation (e − + Li + ) degrees of the two LMRs emerge at end‐of‐discharge and can stem from differences in either redox resistance and/or resistance of Li + intercalation, for example, due to slight crystal stacking faults in the course of different synthesis conditions and/or simply from bigger particle sizes.