An efficient electrolyte additive of 1,3,6-hexanetricarbonitrile for high performance aqueous zinc-ion batteries

The growth of Zn dendrites and parasitic side reactions between electrode and electrolyte are major obstacles to the development of rechargeable aqueous zinc-ion batteries. To address these critical issues, the use of nitrile organic compounds as electrolyte additives holds great promise. Herein, for the first time, we prepared a small volume concentration (x) of 1,3,6-Hexanetricarbonitrile (HTCN-x) as additives into zinc trifluoromethanesulphonate (Zn(OTF)₂) electrolyte and studied their electrochemical properties in Zn||Zn_xV₂O₅·nH₂O (Zn||ZVO) cells. It was found that the strong interaction between H₂O and HTCN could significantly reduce the population of solvated H₂O outside the solvation sheath, leading to reduced side reactions in the aqueous Zn(OTF)₂ electrolyte. Moreover, the HTCN additive also facilitates the formation of strong and stable solid electrolyte interphase (SEI) film on the surface of the Zn anode, which effectively prevents the growth of Zn dendrites and the anode corrosion caused by the electrolyte. As a result, the HTCN-x (x = 0.3) electrolyte enabled the symmetrical Zn||Zn cell to cycle over 950 h at a current of 1 mA cm^-2 with a limited capacity of 1 mAh cm^-2. When the HTCN-0.3 electrolyte was used in Zn||ZVO cell, the cell delivered a high initial capacity of 355.6 mAh g^-1 at 0.1 A g^-1 and maintained a high capacity of 330.0 mAh g^-1 at 1 A g^-1 after 465 cycles.