Synergetic effect of water-in-bisalt electrolyte and hydrogen-bond rich additive improving the performance of aqueous batteries

Abstract Aqueous zinc batteries are the frontiers in electrochemical energy–storing devices due to their environmental friendlies, excellent safety, and low-cost nature. However, dendrite growth, gas generation and, limited cycling life are the bottlenecks for aqueous zinc batteries’ practical use. Here, we engineered a water-in-bisalt electrolyte with a hydrogen-bond rich additive 1,2- dimethoxy ethane (DME), which synergistically reduces free water activity and improves the electrochemical performance of aqueous lithium – zinc hybrid batteries. As a result, the Zn||Cu half-cell exhibits 99.43% average coulombic efficiency (ACE) at 0.5 mA cm−2 after 200 cycles using DME additive. Molecular Dynamics (MD) simulation, FTIR, Raman, and NMR confirm the significant decrease of water activity via the synergetic effect of water-in-bisalt electrolyte and the hydrogen-bond rich additive (DME). Interestingly, the synergetic effect improves zinc nucleation and growth on the surface of the anode and forms homogeneous, dense and smooth zinc deposition. In contrast, the ACE of the non-DME-containing electrolyte is 99.25%., at the same condition, The Zn||LFP full cell with the DME additive gives a CE higher than 99.3% and the capacity retention of 99.49% after 100 cycles at 91 mAg−1 compared to almost no capacity in the absence of DME after 35 cycles.