Rampant side reactions such as hydrogen evolution reaction (HER), corrosion and uncontrollable dendrite growth at anodes greatly impede the application of AZIBs . Herein, caprolactam (CPL) is employed as a crucial electrolyte medium to achieve the aim of highly reversible zinc anodes . CPL molecules exhibit a lower adsorption energy (−1.94 eV) than H 2 O and preferential binding with Zn anodes, resulting in a H 2 O-poor anode/electrolyte interface and an enhanced steric effect at the anode surface. This effect effectively hinders the contact between zinc metal and water molecules, consequently facilitating the uniform and controlled deposition of Zn 2+ . Furthermore, the combination between CPL and Zn 2+ contributes to the optimization of solvation structures. Consequently, Zn/Zn batteries with CPL additives realized more than 2100 h stable cycling life under 1 mA cm −2 and 1 mAh cm −2 . Moreover, Zn/Cu batteries with CPL additives achieved a reversible plating/stripping process for over 3000 cycles with high average CE of 99.4%. Besides, the assembled Zn/NH 4 V 4 O 10 full batteries using electrolyte of ZnSO 4 /CPL also exhibited excellent cyclic performance. The batteries yielded 77.1 mAh g −1 under the current density of 5 A g −1 after 1000 cycles. CPL demonstrates significant potential as a cost-effective and multifunctional electrolyte additive for achieving stable and reliable AZIBs.
The natural reactivity of Zn metal in aqueous environments leads to surface deterioration and uncontrolled dendrite growth, posing challenges in the advancement of Zn-ion batteries. In this research, we introduce an environmentally friendly and cost-effective electrolyte additive, ammonium oxalate (AO), to significantly extend the cycle life of Zn-ion batteries with minimal usage. Oxalate ions within AO actively participate in the solvation of hydrated Zn ions and attach to the Zn anode surface prior to H 2 O molecules, creating a robust solid-electrolyte interface (SEI) layer. This SEI layer serves a dual purpose: it inhibits further reactions with H 2 O and restricts the two-dimensional movement of Zn ions, promoting the preferential growth of the (0 0 2) crystal plane. Consequently, Zn||Zn cells exhibit an impressive lifespan surpassing 1800 h (at 1 mA cm −2 , 1 mAh cm −2 ), and Zn||Cu cells experience a tenfold increase in cycling life. Moreover, Zn||MnO 2 full cells, incorporating this low-cost and highly efficient inorganic additive, maintain an outstanding 80.84 % capacity retention after 1200 cycles at 1 A g −1 . This breakthrough with AO offers a promising avenue for the practical implementation of Zn-ion batteries, emphasizing their cost-effectiveness and environmental sustainability.
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