Dilatometric study of thickness change of lithium-metal electrode during cycling

Abstract

The Li-metal electrode, which has the lowest electrode potential and largest reversible capacity among negative electrodes, is a key material for high-energy-density rechargeable batteries. However, a problem that must be solved is the capacity fading during cycling caused by Li dendrite growth and/or solid electrolyte interphase formation on the surface. This study examines the dimensional change of the Li-metal electrode during cycling using dilatometry, which allows the measurement of the change in electrode thickness in operando. Because the electrode expands continuously with each cycle, the dimensional change is irreversible during Li-metal plating and stripping. Furthermore, when the electrode thickness increases to 50 μm, the capacity suddenly deteriorates. The cycle efficiency Q(n+1)/Q(n) is correlated with the irreversibility of the dimensional change. The dilatometric study clarifies that the abnormal expansion of the Li-metal electrode causes its degradation. Thus, the improvement of the dimensional stability of the Li-metal electrode is the key to enabling long-term cycling.