Membrane‐Free Alkali Metal‐Iodide Battery with a Molten Salt

Abstract

Batteries with liquid metal electrodes are attractive candidates for sustainable energy‐storage applications due to low manufacturing cost and high recyclability. These batteries should be developed for lower operating temperature, higher cell voltage, and membrane‐free cell configuration. Herein, a new type of a membrane‐free cell relying on liquid alkali metals and iodide is demonstrated. As a proof‐of‐concept study, membrane‐free alkali metal‐iodide (A‐AI) batteries are constructed by a facile cell assembly introducing current collectors, LiI–LiCl–KI–CsI salt mixture, and an insulator without relying on solid‐state mediums for separating electrolytes. For the initial assembly, no active electrode materials are required since they are naturally formed during battery operation. Despite the unoptimized cell construction, the membrane‐free A‐AI batteries show promising electrochemical performance such as a reliable stability for 250 cycles. The cells are able to handle a high current density and show a relatively low self‐discharge rate, which implies the possibility of an iodine‐concentrated layer at the bottom of the cell. This is further supported by postmortem analyses using neutron radiography. X‐ray photoemission spectroscopy is performed to identify the changes in the iodine concentration in the cell.