Spent graphite regeneration: Exploring diverse repairing manners with impurities-catalyzing effect towards high performance and low energy consumption

Abstract

Spent battery recycling has received considerable attention because of its economic and environmental potential. A large amount of retired graphite has been produced as the main electrode material, accompanied by a detailed exploration of the repair mechanism. However, they still suffer from unclear repair mechanisms and physicochemical evolution. In this study, spent graphite was repaired employing three methodologies: pickling-sintering, pyrogenic-recovery, and high-temperature sintering. Owing to the catalytic effect of the metal-based impurities and temperature control, the as-obtained samples displayed an ordered transformation, including the interlayer distance, crystalline degree, and grain size. As anodes of lithium ions batteries, the capacity of repaired samples reached up to 310 mA h g−1 above after 300 loops at 1.0 C, similar to that of commercial graphite. Meanwhile, benefitting from the effective assembly of carbon atoms in internal structure of graphite at >1400 °C, their initial coulombic efficiency were >87%. Even at 2.0 C, the capacity of samples remained approximately 244 mA h g−1 after 500 cycles. Detailed electrochemical and kinetic analyses revealed that a low temperature enhanced the isotropy, thereby enhancing the rate properties. Further, economic and environmental analyses revealed that the revenue obtained through suitable pyrogenic-recovering manners was approximately the largest value (5500 $ t−1). Thus, this study is expected to clarify the in-depth effect of different repair methods on the traits of graphite, while offering all-round evaluations of repaired graphite.