Abstract
Lithium metal is considered as one of the most promising anode materials for high-energy-density rechargeable batteries. However, uncontrolled dendrite growth, the unstable interface between lithium metal anode and electrolyte, and infinite volume change are major obstacles in their practical applications. Constructing a solid electrolyte interphase (SEI) with high strength, good stability and desirable flexibility is one of the most promising approaches to mitigate the volume expansion of lithium anode and induce the uniform deposition of lithium for dendrite-free anode. Herein, we summarize the advances of SEI modification from the aspects of in-situ (adding electrolyte additives) and ex-situ (constructing artificial SEI) methods. The ideal SEI on lithium anode can effectively suppress the lithium dendrite growth and volume change of lithium metal anode. In the future study, the modification of SEI should focus on the suppression of side reactions between active lithium metal and electrolyte and the formation of dead lithium, which is quite significant to reduce the consumption of active lithium anode and electrolyte for safe and long-life high energy lithium metal batteries. Constructing an excellent SEI is a robust strategy to achieve the highly stable lithium metal anode for practical application of lithium metal batteries.
Highlights
Lithium metal has become an ideal anode material for next-generation high-energy-density lithium-ion batteries due to its high specific capacity (3,860 mAh g−1), low reduction potential (−3.040 V vs. standard hydrogen electrode) and low density (0.534 g cm−3) (Jung et al, 2015)
Researchers have proposed some methods to solve these problems such as designing a three-dimensional (3D) current collector to induce uniform lithium deposition and mitigate the volume change of the lithium anode (Yun et al, 2016), constructing coating layer on separator to control lithium dendrite growth (Liu Y. et al, 2017), improving the stability and mechanical strength of the solid electrolyte interphase (SEI) on the surface of lithium anode to inhibit the growth of dendrites (Gao et al, 2019), and employing non-flammable solid electrolyte to block Li dendrites and mitigating the safety hazards (Lu et al, 2019; Zhu et al, 2019; Pang et al, 2020)
The SEI formed naturally is relatively brittle and unstable, which is damaged due to the mechanical stress caused by the rapid volume change during lithium deposition and dissolution, resulting in the uneven lithium ion flux and formation of lithium dendrites
Summary
Lithium metal has become an ideal anode material for next-generation high-energy-density lithium-ion batteries due to its high specific capacity (3,860 mAh g−1), low reduction potential (−3.040 V vs. standard hydrogen electrode) and low density (0.534 g cm−3) (Jung et al, 2015). Among them, constructing an SEI with high strength, good stability, and sufficient flexibility on the surface of lithium anode can fundamentally suppress lithium dendrite growth, and effectively reduce the sacrifice in energy density of the battery.
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