Chaotropic Electrolyte Enabling Wide-Temperature Metal-Free Battery

Metal-free aqueous batteries are promising candidates for grid-scale energy storage owing to their inherent safety, low cost, and cost effectiveness. The battery chemistry based on fast NH4+ diffusion kinetics avoids unfavorable generation of inactive metallic byproducts. However, their practical applications have been impeded by electrolyte instability and the intrinsic drawbacks of current electrodes. Herein, we propose an aqueous ammonium-iodine battery by using a chaotropic electrolyte, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) anode, and iodine composite (I2@CC) cathode. Experimental investigations and theoretical calculations reveal that the chaotropic electrolyte not only enhances electrolyte stability through modulating the H-bond structure but also facilitates the formation of a hydrophobic cationic sieve (HCS) on the anode, which ensures the electrolyte/electrode stability and high reversibility of the anode. Additionally, the Cl--containing electrolyte can support the consecutive I+/I0 reaction on the cathode by forming [IClx]1-x interhalogen. The as-assembled aqueous ammonium-iodine batteries (AIBs) based on NH4+ accommodation at the anode and I+/I0 redox reaction at the cathode can deliver superior electrochemical performance at room temperature and low temperature (-20 °C). This study provides a strategic insight into developing metal-free aqueous batteries with electrolyte modulation.