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.