Membrane-less Aluminum Displacement Batteries Based on Transition Metal Chlorination in Molten Salts.

Meng, Jiashen; Wang, Yu; Xiao, Zhitong; Zhu, Lujun; Hong, Xufeng; Jia, Yongfeng; Liu, Fang; Xu, Linhan et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Stationary electrochemical energy storage calls for low-cost and high-safety next-generation chemistries, among which the Na-NiCl<sub>2</sub> battery based on the displacement reaction stands out but is threatened by the fragile β″-Al<sub>2</sub>O<sub>3</sub> membrane. Here we present a class of low-lost, medium-temperature (150 °C), membrane-less aluminum displacement batteries (ADBs) based on a reversible solid-to-solid displacement reaction between transition metals (TM; Fe, Co, Ni) and their chlorides (TMCs) in alkali chloroaluminate molten salts. Crucially, manipulation of the Lewis acidity of the chloroaluminate molten salt electrolyte enables membrane-less operation of the cell by restricting solubility of the TMC and its crosstalk with the Al negative electrode. The structured Ni cathode exhibits a high capacity of 380 mA h g<sup>-1</sup>, low overpotential of ∼50 mV at the rate of 0.2 A g<sup>-1</sup>, and high stability over 500 cycles. Furthermore, we demonstrate a membrane-less Al-Fe displacement battery that promises an ultralow-cost avenue for stationary energy storage.