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

Abstract

Batteries with liquid metal electrodes are attractive candidates for sustainableenergy-storage applications due to low manufacturing cost and high recyclability.These batteries should be developed for lower operating temperature, higher cellvoltage, and membrane-free cell configuration. Herein, a new type of a mem-brane-free cell relying on liquid alkali metals and iodide is demonstrated. As aproof-of-concept study, membrane-free alkali metal-iodide (A-AI) batteries areconstructed by a facile cell assembly introducing current collectors, LiI–LiCl–KI–CsI salt mixture, and an insulator without relying on solid-state mediums forseparating electrolytes. For the initial assembly, no active electrode materials arerequired since they are naturally formed during battery operation. Despite theunoptimized cell construction, the membrane-free A-AI batteries show promisingelectrochemical performance such as a reliable stability for 250 cycles. The cellsare able to handle a high current density and show a relatively low self-dischargerate, which implies the possibility of an iodine-concentrated layer at the bottom ofthe cell. This is further supported by postmortem analyses using neutron radi-ography. X-ray photoemission spectroscopy is performed to identify the changesin the iodine concentration in the cell.