Tin foil should have outstanding volumetric capacity as a Li-ion battery anode; however, it suffers from an unacceptable initial coulombic efficiency (ICE) of 10–20%, which is much poorer than that of Si or SnO2 nanoparticles. Herein, we demonstrate that bare Sn catalyzes liquid electrolyte decomposition at intermediate voltages to generate gas bubbles and Leidenfrost gas films, which hinder lithium-ion transport and erode the solid–electrolyte interphase (SEI) layer. By metallurgically pre-alloying Li to make LixSn foil, the lower initial anode potential simultaneously suppresses gassing and promotes the formation of an adherent passivating SEI. We developed a universally applicable roll-to-roll mechanical prelithiation method and successfully prelithiated Sn foil, Al foil and Si/C anodes. The as-prepared LixSn foil exhibited an increased ICE from 20% to 94% and achieved 200 stable cycles in LiFePO4//LixSn full cells at ∼2.65 mA h cm−2. Surprisingly, the LixSn foil also exhibited excellent air-stability, and its cycling performance sustained slight loss after 12 h exposure to moist air. In addition to LiFePO4, the LixSn foil cycled well against a lithium nickel cobalt manganese oxide (NMC) cathode (4.3 V and ∼4–5 mA h cm−2). The volumetric capacity of the LixSn alloy in the LFP//LixSn pouch cell was up to ∼650 mA h cm−3, which is significantly better than that of the graphite anode on a copper collector, with a rate capability as high as 3C.
