Highly stabilized and lowly polarized Li anodes using a hybrid surface film with inner Li-Zn nucleation sites and outer LiF-rich protection texture

Lithium (Li) metal is the most promising anode for improving the energy density of currently commercialized Li-ion batteries. However, its practical application is limited due to its high reactivity to electrolytes, which induces severe electrolyte decomposition and Li-dendrite growth. Interphases are usually constructed on Li anode to address the above issue. Meanwhile, it is a big challenge to balance the stability and plating/stripping overpotential of Li anode. In this work, we report a novel strategy for constructing a highly stable and lowly polarized surface film on Li anode. A chemically and structurally unique film is formed by simply dropping a zinc trifluoromethanesulfonate [Zn(OTF)(2)] and fluoroethylene carbonate (FEC)-containing solution onto Li anode. This unique film consists of inner nucleation sites and outer protection textures, mainly containing Li-Zn alloy and LiF/polymer, respectively. The former results from the preferential reduction of Zn(OTF)(2), providing nucleation sites with low polarization for Li plating/stripping. In contrast, the latter arises from the subsequent reduction of FEC, providing protection for the underneath Li-Zn alloy and Li metal and ensuring the stability of Li anode. The Li anode with such a unique surface film exhibits excellent cycling stability and low plating/stripping overpotentials, which have been demonstrated using Li//Li symmetric and Li//LiFePO4 full cells.

Automated summary

In this work, a novel strategy for constructing a highly stable and lowly polarized surface film on Li metal anode is reported. The unique film, formed by dropping a solution containing zinc trifluoromethanesulfonate [Zn(OTF)(2)] and fluoroethylene carbonate (FEC) onto Li anode, consists of Li-Zn alloy and LiF/polymer, providing protection and nucleation sites for Li plating/stripping. The Li anode with this unique surface film exhibits excellent cycling stability and low plating/stripping overpotentials.