Bifunctional role of carbon nanofibrils within Li powder composite anode: More Li nucleation but less Li isolation

Abstract

Enlarging the surface area in the Li metal electrode is practically attractive for increasing long-term cycle life. In this regard, Li metal powders (LMPs) have a larger surface area, which is very beneficial for controlling dendrites and fast charging compared to planar Li metal foil. However, there is the need to increase nucleation sites in LMP electrodes for faster charging and suppress unavoidable dead Li formation caused by an electrical disconnection between individual LMPs and current collector for their commercial application. Herein, we present a 40 μm-thick, carbon nanotube-embedded LMP (CNT-LMP) electrode. The CNTs improve the LMP inter-particle contact and the contact with the Cu current collector and provide additional Li nucleation sites. As a result, the Li/Li symmetric cell with the CNT-LMP electrode exhibited a stable cycling and a longer cycle life (over 1000 h) than the bare LMP electrode (680 h). Furthermore, a full cell of LiNi0.6Mn0.2Co0.2O2/CNT-LMP could achieve a longer and more stable cycle performance of up to 600 cycles under practical current conditions (0.5 C/2 C, Charge/Discharge). In comparison, the bare cell without CNT decayed suddenly after 300 cycles.