Sn-Alloy Foil Electrode with Mechanical Prelithiation: Full-Cell Performance up to 200 Cycles

Self-supporting Sn foil is a promising high-volumetric-capacity anode for lithium ion batteries (LIBs), but it suffers from low initial Coulombic efficiency (ICE). Here, mechanical prelithiation is adopted to improve ICE, and it is found that Sn foils with coarser grains are prone to cause electrode damage. To mitigate damage and prepare thinner lithiated electrodes, 3Ag0.5Cu96.5Sn foil is used that has more refined grains (5-10 mu m) instead of Sn (50-100 mu m), where the abundant grain boundaries (GBs) offer more sliding systems to release stress and reduce deep fractures. Thus, the thickness of Li(x)3Ag0.5Cu96.5Sn can be reduced to 50 mu m, compared to 100 mu m LixSn. When the foils contact open air, the Sn-Li-O(H) products are more stable than Li-O(H), thus Li(x)3Ag0.5Cu96.5Sn shows outstanding air stability. The as-prepared 50 mu m foil anode achieves stable 200 cycles in LiFePO4//Li(x)3Ag0.5Cu96.5Sn full cell (approximate to 2.65 mAh cm(-2)) and the capacity retention is 95%. Even at 5C, the capacity of Li(x)3Ag0.5Cu96.5Sn is still up to approximate to 1.8 mAh cm(-2). The cycle life of NCM523//Li(x)3Ag0.5Cu96.5Sn full cell exceeds that of NCM523//Li. Furthermore, 70 mu m Li(x)3Ag0.5Cu96.5Sn is used as double-sided anode for a 3 cm x 2.8 cm pouch cell and its actual volumetric capacity density is 674 mAh cm(-3) after 50 cycles.