Strategies, perspectives, and challenges of improving the initial coulombic efficiency and tap density of Sn-based anode materials for lithium-ion batteries

Currently, the energy density and cycle life of commercial lithium-ion batteries (LIBs) are still unable to meet the ever-growing demand, and further development still faces various challenges. Sn-based anode materials have attracted much attention due to their high specific capacity (993 mAg⁻¹ for Li_4.4Sn), wide availability, high safety, and low cost. However, the low initial coulombic efficiency (ICE) of Sn-based anode materials severely limits their practical applications, and ICE plays an essential role in improving the energy density of LIBs. In addition, the tap density of Sn-based anode materials directly affects the volumetric energy density of LIBs. However, a comprehensive review needs to summarize the methods to enhance ICE and tap density of Sn-based anode materials for LIBs. Therefore, this review first describes the effects of ICE and tap density on the performance of Sn-based LIBs, analyses the reasons for low ICE, and summarizes strategies to solve the problem. Methods to improve the tap density of Sn-based anode materials are outlined in detail. Finally, the challenges, perspectives, and future directions of the research on ICE and tap density of Sn-based anode materials are put forward, which may contribute to further improving the ICE and tap density of LIBs.