Superior Multielectron‐Transferring Energy Storage by π‐d Conjugated Frameworks

Abstract Reversible multielectron‐transfer materials are of considerable interest because of the potential impact to advance present electrochemical energy storage technology by boosting energy density. To date, a few oxide‐based materials can reach an electron‐transfer number per metal‐cation (e_M) larger than 2 upon a (de)intercalation mechanism. However, these materials suffer from degradation due to irreversible rearrangements of the cation–oxygen bonds, and are based on precious metals, for example, Ir and Ru. Hence, a design of the non‐oxide‐based reversible multielectron‐transfer materials with abundant elements can provide a promising alternative. Herein, it is demonstrated that the bis(diimino)copper framework can show e_M = 3.5 with cation/anion co‐redox mechanism together with a dual‐ion mechanism. In this study, the role of the cation–anion interactions is unveiled by using an experiment/theory collaboration applied to a series of the model non‐oxide abundant electrode systems based on different metal–nitrogen bonds. These models provide designer multielectron‐transfer due to the tunable π‐d conjugated electronic structures. It is found that the Cu–nitrogen bonds show a unique reversible rearrangement upon Li‐intercalation, and this process responds to acquire a significant reversible multielectron‐transfer. This work provides new insights into the affordable multielectron‐transfer electrodes and uncovers an alternative strategy to advance the electrochemical energy storage reactions.