Thin (≤20 μm) and free-standing Li metal foils would enable precise prelithiation of anode materials and high-energy-density Li batteries. Existing Li metal foils are too thick (typically 50 to 750 μm) or too mechanically fragile for these applications. Here, we developed a facile and scalable process for the synthesis of an ultrathin (0.5 to 20 μm), free-standing and mechanically robust Li metal foil within a graphene oxide host. In addition to low areal capacities of ~0.1 to 3.7 mAh cm⁻², this Li foil also has a much-improved mechanical strength over conventional pure Li metal foil. Our Li foil can improve the initial Coulombic efficiency of graphite (93%) and silicon (79.4%) anodes to around 100% without generating excessive Li residue, and increases the capacity of Li-ion full cells by 8%. The cycle life of Li metal full cells is prolonged by nine times using this thin Li composite anode.

薄（≤20 μm）和独立的锂金属箔可以实现阳极材料和高能量密度锂电池的精确预锂化。现有的锂金属箔对于这些应用来说太厚（通常为 50 到 750 μm）或机械上太脆弱。在这里，我们开发了一种简便且可扩展的工艺，用于在氧化石墨烯主体内合成超薄（0.5 至 20 μm）、独立且机械坚固的锂金属箔。除了~0.1 至 3.7 mAh cm ^{-2的低面积容量}，与传统的纯锂金属箔相比，这种锂箔的机械强度也大大提高。我们的锂箔可以将石墨（93%）和硅（79.4%）负极的初始库仑效率提高到100%左右，而不会产生过多的锂残留物，并将锂离子全电池的容量提高8%。使用这种薄的锂复合负极，锂金属全电池的循环寿命延长了 9 倍。