Low-expansion Si anode with an ultrathin structure for long life lithium-ion batteries

While silicon (Si) has garnered extensive research attention in lithium-ion batteries (LIBs) owing to its high specific capacity (∼4200 mAh g−1), its application is hindered by its large volume expansion during cycling. Here, we present the fabrication of a low- expansion Si anode with an ultrathin structure on a Cu foil using a physical vapor deposition method. The uneven structure of the Cu foil effectively provided a suitable volume expansion space and further buffered the interface stress during the lithiation process. Moreover, the nanosized structure of Si can withstand its own volume-change stress during cycles. The high-strength Si thin film ensures the stability of a solid electrolyte interphase (SEI) and provides a short ion transport distance, which further improves the electrochemical performance. The obtained Si anode exhibited an initial specific capacity of 2499 mAh g−1, an ultralong cycling stability (99.77% of capacity retention after 300 cycles at 0.5 C), and a rate capability of 1598 mAh g−1 at 5 C. These results suggest that the design of the ultrathin structure can provide an efficient strategy to address the stress rupture and continuous growth of the SEI in Si-based anode materials during the lithiation and delithiation processes.