Not All Lithium–Indium Counter Electrodes Are Made Equal: Probing the Inhomogeneities and Kinetics of Uniaxially Pressed Li–In Counter Electrodes in All Solid-State Batteries

Lithium indium alloys are commonly used as counter electrodes in all-solid-state batteries. However, the method of preparation varies from research groups, including ball milling, roll pressing, and uniaxial pressing of the two metals. While the latter is a common approach used in the literature, it is not entirely clear how homogeneous uniaxially pressed counter electrodes are and whether the differences can be observed electrochemically. In this work, in the first section, two distinct Li sources, one from the chemical Li–In alloy and the other from the electrochemical Li–In alloy formed during cycling, are electrochemically probed and investigated as a function of the temperature, indium foil thickness, and Li area. In the second section, the kinetics of electrochemically alloyed Li–In (e-LixIn) are investigated using Butler-Volmer kinetics to extrapolate exchange current densities in combination with time and temperature-dependent distribution of relaxation time (DRT) analyses to better understand the alloying and dealloying process. These findings underscore the considerable influence that counter electrode preparation has on the kinetics and electrochemical performance of two electrode half-cells.