A Double-Charged Organic Molecule Additive to Customize Electric Double Layer for Super-Stable and Deep-Rechargeable Zn Metal Pouch Batteries

The electrochemical performance of aqueous zinc metal batteries (AZMBs) is highly dependent on the electric double layer (EDL) properties at Zn electrode/electrolyte interface. Herein, a novel reconfigured EDL is constructed via a double-charged theanine (TN) additive for super-stable and deep-rechargeable AZMBs. Experiments and theoretical computations unravel that the positively charged TN not only serves as preferential anchor to form a water-poor Helmholtz plane onto the Zn anode, but also its anionic end could coordinate with Zn2+ to tailor the solvation structure in the diffusion layer and further reconstruct the inner H-bonds networks, thus effectively guiding uniform Zn deposition and suppressing the water-induced side reactions. Consequently, the Zn//Zn cells acquire outstanding cycling stabilities of nearly 800 h at a high depth of discharge of 80%. Moreover, the Zn//VOX full cells deliver substantial capacity retention (94.12% after 1400 cycles at 2 A g-1) under practical conditions. Importantly, the designed 2.7 Ah Zn//VOX pouch cell harvests a recorded energy density of 42.3 Wh Kgcell-1 and 79.5 Wh Lcell-1, with a remarkable capacity retention of 85.93% after 220 cycles at 50 mA g-1. This innovative design concept to reshape the EDL chemistry would inject fresh vitality into developing advanced AZMBs and beyond. A double-charged organic molecule additive of theanine fosters the customized electric double layer structure with a regulated Zn anode interface in the Helmoze plane, tailored Zn2+ solvation chemistry and reconstructed inner H-bonds networks in the diffusion layer, rendering the high-performance Zn metal anodes.image