Novel Surface Modification Route for Highly Stable Li Anodes of Li Metal Batteries

The Li metal is an ideal anode material owing to its high theoretical specific capacity and low electrode potential. However, its high reactivity and dendritic growth in carbonate-based electrolytes limit its application. To address these issues, we propose a novel surface modification technique using heptafluorobutyric acid. In-situ spontaneous reaction between Li and the organic acid generates a lithiophilic interface of lithium heptafluorobutyrate for dendrite-free uniform Li deposition, which significantly improves the cycle stability (Li/Li symmetric cells >1200 h at 1.0 mA cm-2) and coulombic efficiency (Li efficiency >99.3%) in conventional carbonate-based electrolytes. This lithiophilic interface also enables full batteries to achieve 83.2% capacity retention over 300 cycles under realistic testing condition. Lithium heptafluorobutyrate interface acts as an electrical bridge for uniform lithium-ion flux between Li anode and plating Li, which minimizes the occurrence of tortuous lithium dendrites and lowers interface impedance.金属锂（Li metal）因具有极高的理论比容量与极低的电极电势，是理想的负极材料。然而，其高反应活性以及在碳酸盐基电解液中出现的锂枝晶生长问题，限制了其实际应用。为解决上述问题，本研究提出一种采用七氟丁酸的新型表面改性技术。锂金属与该有机酸之间的原位自发反应，可生成七氟丁酸锂（lithium heptafluorobutyrate）亲锂界面，实现无枝晶的均匀锂沉积；该界面可显著提升传统碳酸盐基电解液中的循环稳定性（锂/锂对称电池在1.0 mA·cm⁻²电流密度下循环时长超1200 h）与库仑效率（锂利用率＞99.3%）。该亲锂界面还可使全电池在实际测试条件下，经过300次循环后仍保持83.2%的容量保持率。七氟丁酸锂界面可作为锂负极与沉积锂之间的均匀锂离子通量导电桥，最大限度抑制弯曲状锂枝晶的生成，并降低界面阻抗。