High entropy oxides (HEOs) with chemically disordered multi-cation structure attract intensive interest as negative electrode materials for battery applications. The outstanding electrochemical performance is attributed to the high-entropy stabilization and so-called ‘cocktail effect’. However, the configurational entropy is insufficient to drive the structural reversibility of the room-temperature thermodynamically metastable HEO during conversion-type battery reaction, and the ‘cocktail effect’ has not been explained thus far. This work unveils the multi-cations synergy of the HEO Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O at atomic and nanoscale during electrochemical reaction and explains the ‘cocktail effect’. The more electronegative elements form an electrochemically inert 3-dimensional metallic nano-network enabling electron transport. The electrochemical inactive cation stabilizes an oxide nanophase, which is semi-coherent with the metallic phase and accommodates Li+ ions. This self-assembled nanostructure enables stable cycling of micron-sized particles, which bypasses the need for nanoscale pre-modification required for conventional metal oxides in battery applications. This demonstrates elemental diversity is the key for optimizing multi-cation electrode materials.

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