We developed rational strategies for exploiting two common principles in organometallic chemistry for enhancing the robustness of pseudo-octahedral Co-polypyridyl complexes. Namely, the spin-crossover between low and high-spin states and the chelation effect emerging from replacing three bidentate ligands with two tridentate analogues. Quantum chemical models are used to conceptualize our approach and make predictions that are tested against experiments by preparing prototype Co-complexes and profiling them as catholytes and anolytes. In good agreement with the conceptual predictions, very stable cycling performance over 600 charge cycles is found.