3. Conclusion
The dual-additives of LiAsF6 and FEC in commercial carbonate electrolytes (1 M LiF6 in EC/DMC/DEC) for anode-free lithium-ion batteries (AFLBs) are introduced to enhance the CE and capacity stability. Benefiting from the synergistic effect of the dual additives, the assembled AFLBs (NCM||Cu geometry) could deliver a high average CE of up to 98.3% when cycled at 0.5 mA·cm-2. It shows a reasonably high discharge capacity retention of 75% after 50 cycles. In contrast, the pristine commercial electrolyte exhibited a lower CE of 97% and low-capacity retention of 35% after 50 cycles. In situ optical observation indicates that the introduction of dual additives induces the plating of Li metal into a more compact and conformal morphology, resulting in a reduced battery residence. Furthermore, in situ Raman measurements revealed the synergistic effect of LiAsF6 and FEC additives in controlling the Li nucleation and growth to form Li columns with self-alignment in the plane. That results in more compact, uniform, and less-dendritic Li metal anodes. It also was observed that LiAsF6 and FEC could be reduced to form the LixAs alloy phase and LiF. That facilitates forming of solid and rigid LiF-rich interphase layers on negative and positive electrode surfaces. A deep understanding of the positive impact of additives on controlling Li growth and stable SEI layers opens up the potential for developing low-cost and efficient functional electrolytes for long-life AFLBs.