Lithium metal foil is a key component in lithium rechargeable batteries. It has an excellent conductive capability for cathodes and an inert mechanical support for anodes. However, it is not a solid-state material, which means that the reactivity and contact between electrodes can be an important limiting factor in battery performance. Therefore, several approaches have been developed to enhance the electrochemical performance of lithium metal foil, including surface modification.
Simple Surface Modification
One approach was to dip lithium foil in a DMSO solution containing a small quantity of polyphosphoric acid. This treatment produces a high-conductivity Li3PO4 layer on the Li metal surface and is able to suppress dendrite growth (Li et al., 2016).
GO-modified Li foil is also reported to exhibit superior cycling stability in standard carbonate-based electrolytes compared to bare lithium electrodes. This is attributed to the formation of a stable GO film on the Li surface, which reduces the tendency to form unstable Li/electrolyte interfaces and dendrites that lead to internal short circuit.
3D Nanocomposite Foil
Using a simplified calendaring and folding route, two Li foils were combined with a Sn foil and stacked together to form a Li-Sn-Li nanocomposite foil. The tin foil was then inserted into the Li-Sn-Li foil, and repeated calendaring and folding operations were performed. This produced periodically stacked metallic lithium and tin nanolayers with rich amount of Li/Sn interfaces.
The as-fabricated Li/Li22Sn5 nanocomposite foil exhibited excellent stability for a symmetric cell under 30 mA cm-2 at 5 mAh cm-2 for 200 cycles. It also maintained a capacity of 74% for a 1.0 mAh cm-2 NCM electrode cycled at 6 C (6.6 mA cm-2).