A LiPF6-LiFSI Blended-Salt Electrolyte System for Improved Electrochemical Performance of Anode-Free Batteries

Abstract

ANODE-free Li-metal batteries (AFLMBs) operating with Li of cathode material have attracted enormous attention due to their exceptional energy density originating from anode-free structure in the confined cell volume. However, uncontrolled dendritic growth of lithium on a copper current collector can limit its practical application as it causes fatal issues for stable cycling such as dead Li formation, unstable solid electrolyte interphase, electrolyte exhaustion, and internal short-circuit. To overcome this limitation, here, we report a novel dual-salt electrolyte comprising of 0.2 M LiPF 6 + 3.8 M lithium bis(fluorosulfonyl)imide in a carbonate/ester co-solvent with 5 wt% fluoroethylene carbonate, 2 wt% vinylene carbonate, and 0.2 wt% LiNO 3 additives. Because the dual-salt electrolyte facilitates uniform/dense Li deposition on the current collector and can form robust/ionic conductive LiF-based SEI layer on the deposited Li, a Li/Li symmetrical cell exhibits improved cycling performance and low polarization for over 200 h operation. Furthermore, the anode-free LiFePO 4 /Cu cells in the carbonate electrolyte shows significantly enhanced cycling stability compared to the counterparts consisting of different salt ratios. This study shows an importance of electrolyte design guiding uniform Li deposition and forming stable SEI layer for AFLMBs.

Non-fluorinated non-solvating cosolvent enabling superior performance of lithium metal negative electrode battery

“…However, the dendritic growth of lithium metal, which leads to battery failure, remains a problem 5 . A solid-electrolyte interphase (SEI) having high mechanical strength was reported to be effective in preventing dendrite formation 6,7 . Such an SEI layer stops unwanted reactions between the electrolytes and lithium metal and prevents dendrite growth to conserve the lithium metal source.…”

Behavior of NO3−-Based Electrolyte Additive in Lithium Metal Batteries

“…Figure 12d-f show that the LiNO 3 -VC dual additive exhibits improved performance in terms of coulombic efficiency and ion transfer resistance [114]. In addition, a study showing the synergy effect of LiFSI, LiPF 6 and LiNO 3 in a carbonate-based electrolyte has been reported [116].…”

Li-growth and SEI engineering for anode-free Li-metal rechargeable batteries: A review of current advances

“…The concentration ratios are also essential for highly concentrated dual-salt systems. Kim and coworkers examined the effectiveness of the LiPF 6 +LiFSI dual-salt carbonate-based electrolyte system with various concentrations [112]. The authors demonstrated that a mixed salt ratio of LiPF 6 /LiFSI > 1 resulted in limited capacity retention of the assembled AFLBs.…”