Lithium metal is an ideal anode material for high energy-density batteries owing to its high specific capacity and low redox potential. The carbonate-based electrolytes are attractive in developing high energy-density lithium metal batteries because of their wide electrochemical windows. However, the lithium deposition potential is often found dropping in the cells using the carbonate-based electrolytes, which may lead to overcharge as well as low energy conversion efficiency and low energy density of a full cell. Herein, the reason for the potential dropping in the commercial LiPF₆-EC/DMC electrolyte is studied by both electrochemical evaluation and physical characterization (EC for ethylene carbonate and DMC for dimethyl carbonate). It is clarified that the repeated formation and decomposition of the organic species such as ROCO₂Li and ROLi in the solid electrolyte interphase (SEI) layer during lithium plating/stripping cycling are responsible for the potential dropping. Our findings shed light on eliminating or suppressing the potential dropping to improve the energy density and the energy conversion efficiency of the secondary lithium metal batteries.

金属锂由于其高的比容量和低的氧化还原电位而成为高能量密度电池的理想阳极材料。基于碳酸盐的电解质因其宽的电化学窗口而在开发高能量密度的锂金属电池方面具有吸引力。然而，经常发现使用基于碳酸盐的电解质在电池中锂沉积电位下降，这可能导致过充电以及整个电池的低能量转换效率和低能量密度。此处，商用LiPF ₆潜在下降的原因-EC / DMC电解质通过电化学评估和物理特性（碳酸亚乙酯为EC，碳酸二甲酯为DMC）进行了研究。可以明确的是，在锂电镀/剥离循环过程中，固体电解质中间相（SEI）层中有机物（例如ROCO ₂ Li和ROLi）的反复形成和分解是造成电位下降的原因。我们的发现为消除或抑制电位下降以改善二次锂金属电池的能量密度和能量转换效率提供了启示。