Synergistic effect of embossed Cu current collector and potassium nitrate for achieving dense lithium deposition and improving cycle life in anode-free Li metal batteries

Abstract

Anode-free lithium metal batteries (AFLMB) operate solely with lithium (Li) in the lithiated cathode, eliminating the mass and volume of the anode to maximize energy density of the battery. However, uneven Li deposition can lead to the formation of Li dendrites, hindering practical applications due to issues like solid electrolyte interphase (SEI) breakage and low coulombic efficiency (CE). To address these challenges, we investigated the synergistic effect of applying a 3D-structured current collector (CC) and KNO3 for Li deposition control. We fabricated an embossed Cu CC with a 3D structure using a copper nanoparticle (Cu NP) slurry and intense pulsed light (IPL) sintering techniques. When KNO3 electrolyte additives were used in conjunction with the manufactured 3D embossed Cu, we observed a significant improvement in cycle life. The KNO3 additive prevented the top plating of Li through an electrostatic shielding effect, while the anion contributed to dense Li deposition by forming a stable SEI layer, such as Li3N. Consequently, the combination of embossed Cu and KNO3 enabled thick and compact Li deposition, reducing Li loss during the plating and stripping processes and thereby improving the lifespan of the cell. In AFLMB matched with NCM811, capacity retention after 50 cycles increased to 52%, compared to 0.8% in the absence of electrolyte additives, demonstrating stable operation even after more than 100 cycles. Therefore, combining a thin, 3D-structured CC with an electrolyte additive capable of controlling Li deposition presents a promising strategy for enhancing the practical use of carbonate electrolyte-based AFLMB through synergistic effects.