Roll-to-roll prelithiation of Sn foil anode suppresses gassing and enables stable full-cell cycling of lithium ion batteries

Tin foil should have outstanding volumetric capacity as Li-ion battery anode, but it suffers from unacceptable initial Coulombic efficiency (ICE) of 10~20%, that is even much poorer than Si or SnO2 nanoparticles. Here, we find that bare Sn catalyzes liquid electrolyte decomposition at intermediate voltages to generate gas bubbles and Leidenfrost gas film, which hinder lithium-ion transport and erode solid-electrolyte interphase (SEI) layer. By metallurgically pre-alloying Li to make LixSn foil, the lower initial anode potential paradoxically suppresses gassing and promotes formation of adherent passivating SEI. We developed a universally applicable roll-to-roll mechanical prelithiation method and successfully prelithiated Sn foil, Al foil and Si/C anode. The as-prepared LixSn foil increases ICE from 20 to 94% and achieves stable 200 cycles in LiFePO4//LixSn full cells at ~2.65 mAh cm-2. Surprisingly, the LixSn foil also has excellent air-stability, and the cycling performance sustains little loss after 12-hr exposure to moist air. In addition to LiFePO4, LixSn foil can cycle well against NCM cathode (4.3 V and ~4-5 mAh cm-2). The volumetric capacity of LixSn alloy in LFP//LixSn pouch cell is up to ~650 mAh cm-3, significantly better than that of graphite anode on copper collector, with rate capability as high as 3C.