Superior Rate Capability of Small Regenerated Graphite Particles Induced by Homogeneously Distributed Current Density Derived from Cracks and Intrinsic Defects.

ABSTRACT

As spent batteries can be considered as alternative raw sources of electrode materials; the development of regeneration techniques for spent graphite becomes key to realizing economic and environmental sustainability. Herein, the reutilization of small spent graphite particles is domonstrated due to their special structural characteristics, which may directly contribute to the improvement of lithiation kinetics and high-rate charging during long-term cycling. Such intrinsic defects and external cracked channels may be introduced by the aging of intrinsic bulk structure and exfoliation of surface structure. On account of these potential advantages, a carbonized polypyrrole layer on sieved small graphite particles is developed to obtain superior rate performance. The coated amorphous/graphitic layer could repair the exposed edge and basal plane, and significantly facilitate Li ion diffusion during fast charging. Moreover, the enhanced performance may favor the improved homogeneity of current density distribution during fast charging, which is confirmed by a porous electrode model. The regenerated graphite with a disorder/order coating layer could effectively regulate the Li+ transport channel, exhibiting a high specific capacity at high-rate charging (102.7 mAh g-1 at 4 C after 500 cycles) without severe Li plating. This work provides an opportunity to utilize spent graphite in fast-charging batteries.