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

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.