Free-standing ultrathin lithium metal-graphene oxide host foils with controllable thickness for lithium batteries

Thin (<= 20 mu m) 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 mu m) 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 mu m), free-standing and mechanically robust Li metal foil within a graphene oxide host. In addition to low areal capacities of similar to 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.