Quantitative Analysis and Evolution of Capacity Contribution Between Si and Graphite in Si/Graphite Composite Anodes

Promoting energy density while maintaining outstanding cycling stability and fast-charging ability is a key objective for the widespread utilization of lithium-ion batteries. Unfortunately, the most promising batteries with silicon/graphite (Si/Gr) composite anodes still face the issues of instability and high cost. The cognition of instinctive lithiation behavior between Si and Gr is incomplete. Here, the (de)intercalation and (de)alloying process is distinguished by increment capacity analysis, and the capacity degradation of each phase transform process is quantified with different current rates. The capacity contribution of graphite is easily inhibited by the alloying process of Si, which leads to an incomplete utilization of graphite. Besides, the Li+ accumulation in Si will deteriorate the cycling stability of the anode. The interplay between Si and graphite under different current rates is concluded, which will benefit the material engineering and help to improve the life span of Si-containing batteries.