(Invited) Interfacial Engineering Strategies for Stabilizing Lithium Metal Anodes

The inherent instability of the solid electrolyte interphase (SEI) in lithium (Li) metal batteries faces persistent challenges for achieving stable cycling. To address this, we recently reported a novel fluorinated cyclic ether diluent (3,3,4,4,5,5-hexafluorotetrahydropyran, HFTHP) that features minimized Li-ion coordination. This electrolyte innovation facilitates the formation of a distinctive bilayer SEI, featuring a Li2O-rich inner layer and a LiF-rich outer layer, which significantly enhances electrochemical stability of Li metal batteries. Employing the developed HFTHP-based dual-salt electrolyte, the Li||NMC811 pouch cell with a projected energy density of 410 Wh/kg, demonstrates exceptional cycling performance, retaining 80% capacity after 568 cycles at room temperature and 218 cycles at 60 oC. Additionally, we introduced an interfacial desolvation coating strategy leveraging 12-crown-4 ether-modified silica materials to actively regulate the Li-ion solvation structure. This approach selectively reduces strongly coordinating solvents ethylene carbonate (EC) and diethyl carbonate (DEC), while enriching weakly coordinating fluorinated solvent fluoroethylene carbonate (FEC) at the Li/electrolyte interface. The resulting LiF-dominant SEI reduces organic components, enhancing rate performance and cycling life, as evidenced by 80% capacity retention after 333 cycles in Li||LiCoO2 pouch cell. Most recently, we designed and developed a novel reactive passivation polymer coating for protecting Li metal anodes, which facilitated the formation of a robust, inorganic-dominant bilayer SEI. This advancement enabled high-energy-density Li||NMC811 pouch cells to achieve 80% capacity retention over 611 cycles in a conventional carbonate electrolyte. Collectively, our research demonstrates the transformative potential of interfacial engineering in creating stable SEI, significantly enhancing the longevity of Li metal batteries, and paving the way for their practical application in next-generation energy storage technologies.