Durable Cation Replenishing to Activate Anion Releasing for Enhanced Electrochemical Performance of Dual-Ion Full Batteries

Dual-ion batteries, as one of the most promising alternatives to Li-ion batteries, face severe challenges in terms of side reactions, particularly at the anode. These side reactions result in the consumption of limited cations and the deactivation of anions in graphite during cycling. To date, most reports are focused on reducing these side reactions. Here, a new way is proposed to achieve the stable cycling of dual-ion batteries using Mg as an example. Mg can be oxidized to Mg2+ during the discharge process, thereby replenishing the cation loss due to the side reactions. Meanwhile, anions are released from graphite to maintain the charge balance in the electrolyte. Another advantage is that the formation of Li3Mg7 during cycles facilitates Li plating/stripping. Therefore, Mg||Graphite exhibits a high Coulombic efficiency (approximate to 96.5%) and a stable cycling performance (approximate to 94.6% after 1700 cycles at 2 C) even without prelithiation, much better than Cu||Graphite and Graphite||Graphite. The mechanism also works for other active metals, such as K, Ca, and Na. The results demonstrate the promising potential of this strategy. A novel working mechanism for rechargeable batteries is devised by directly using graphite as the cathode and magnesium foil as the anode and current collector, which achieves a high Coulombic efficiency (approximate to 96.5%) and long cycle life (94.6% after 1700 cycles at 2 C) of dual-ion batteries not by reducing the side reactions, but by building a by-pass on the anode.image