Low water activity-induced storage mechanism change for long-life Te electrode

The rich valence states (−2 to +6) make elemental Te become a high-capacity electrode in aqueous batteries. The conversion process (Te to TeO 2 ) generates soluble Te 4+ species in aqueous electrolyte. The suppression of conversion process enables a long-term Te electrode at the cost of a partial storage capacity. Herein, a polyethylene glycol additive is introduced to regulate the electrolyte environment. The low H 2 O activity hinders Te 4+ species formation and therefore leads to the insertion-type Te electrode. The reshaped NH 4 + solvation structure facilitates the fast H 2 O removal and firm PEG adsorption on the electrode surface, also improving water-induced side reactions. This, coupled with the introduction of carbon host, contributes to a high-stability Te electrode. Theoretical and experiment studies reveal the reshaped NH 4 + solvation structure/hydrogen-bond network, the strong adsorption capability of B-doped carbon, and the inhibited Te dissolution. Additionally, a series of in/ex-situ characterizations prove the intercalation-type mechanism and the enhanced cycling stability. As a result, this elaborate electrode delivers a high reversible capacities of 376 mA h g −1 at 0.05 A g −1 and a long-term cycling stability with 73.8 % capacity retention at 5 A g −1 after 4500 cycles. This work provides a reference for the storage mechanism regulation in aqueous battery.