Molecularly engineered multifunctional imide derivatives for practical Zn metal full cells

Abstract

Aqueous zinc metal batteries (ZMBs) are attractive owing to their intrinsic safety and low cost. However, their practical applications are limited by dendrite growth, hydrogen evolution reactions (HERs), and corrosion. Additionally, the N/P ratio is too high to achieve a large energy density and the current rate is often restricted to ≤4 mA cm⁻². Herein, we demonstrate multifunctional additives of imide derivatives for practical aqueous Zn metal full cells. By systematically comparing four imide derivatives to assess the role of relevant functional groups in the reversibility of Zn deposition, succinimide (H-SU) was chosen as a proof-of-concept additive among the molecularly engineered imide derivative additives. The H-SU additive reconstructs the solvation sheath of Zn²⁺ with imino groups, disrupts the hydrogen bond (HB) network of free water with carbonyl groups, and is adsorbed onto the Zn surface to adjust the inner Helmholtz plane. These combined modifications of solvated and interfacial structures by the multifunctional H-SU additive led to alleviation of the HER and enabled uniform Zn deposition. Consequently, the H-SU additive enabled Zn‖Zn symmetric cells to exhibit long term stability over 2700 h at 1 mA cm⁻² and 1 mA h cm⁻² and even to achieve a record of 21 000 cycles (or 700 h) at an extremely high current density of 60 mA cm⁻². Furthermore, the H-SU additive optimized the battery performance of full cells integrating Zn anodes with three types of cathodes, including polyaniline (PANI), manganese vanadate, and molybdenum oxide@titanium dioxide. Particularly, the Zn‖PANI full cells with a low N/P ratio of 2.2 and an ultrahigh loading of 60 mg cm⁻² delivered a high areal capacity of 4.2 mA h cm⁻² after 100 cycles. Therefore, this work provides insights into the molecular engineering design of multifunctional imide derivative additives and offers technical breakthroughs for practical Zn metal full cells.