Elucidating the Chemical Pre-Lithiation Mechanism of Hard Carbon Anodes for Ultra-high Stability Lithium-Ion Batteries.

The hard carbon (HC) anode materials demonstrate high capacity and excellent rate performance in lithium-ion batteries. However, HC anodes suffer from excessive loss of Li ions during the formation of the solid electrolyte interphase (SEI) film, leading to poor cycling stability, which hinders their large-scale applications. Herein, a facile pre-lithiation strategy is proposed to achieve multi-functional precompensation of carbon nanofibers (CNFs) anodes. Both experimental and density functional theory (DFT) calculation results revealed that the strategy compensated for the loss of Li ions and reacted with four structures of CNFs during pre-lithiation, including tiny graphite domains, CO-containing functional groups, defects, and micropores. Furthermore, the lithium in pre-lithiated carbon nanofibers (pCNFs) existed in various forms, consisting of LiC and LiC, Li─O─C, quasi-metallic lithium, and Li ions. Moreover, the uniformly distributed lithium on the surface of pCNFs induced the formation of denser and more robust LiF/LiCO-rich SEI film, which promoted Li ions transport. As a result, pCNFs showed more stable cycling performance (369.8 mAh g, almost no decay for 1500 cycles). This work provides deeper insight into chemical pre-lithiation and offers a simple and mild strategy for highly stable batteries.