A writable lithium metal ink

The recent revival of Li metal anodes (LMA) leads to a renewed interest in LMA as the ultimate choice for rechargeable lithium batteries towards high energy density. However, multiple challenges stand in the way of using LMA, of which high reactivity, dendrite growth, the difficulty of fabricating Li thin foils, and the flammability of organic liquid electrolytes are typical. Here, a writable Li metal ink (LMI) prepared by introducing biomass-derived carbon particles into molten Li is presented. Due to the significantly decreased surface tension, LMI is able to directly write on copper foils or other substrates that ultrathin Li foils with a remarkably small thickness (<10 µm) can be achieved. The versatility of LMI is further demonstrated in addressing the interface issue between LMA and garnet-type solid-state electrolytes, where directly writing LMI on the garnet offers a perfect contact and enables an extremely low interfacial resistance of 6 Ω cm2, in sharp contrast to 939 Ω cm2 between the pure Li and the garnet. Due to the successful partnership with non-flammable solid-state electrolytes, ink-based technology may have a chance to bring us very close to the use of solid-state lithium metal batteries (SSLMBs) with high safety and high energy density.