Regenerated spent graphite with enhanced pre-storage abilities of near-surface layers towards high-rate properties

Abstract

Attracted by the potential value of spent lithium-ion batteries, their high effective-recycling has been devoted to numerous attentions. Unfortunately, spent graphite is always used as fossil fuel, accompanying with the serious resources wasting and carbon emission. Owing to low-cost and energy-consumption, their direct regeneration has been regarded as the next-generation key technology. Although high-temperature sintering can induce the recovering of internal structure, they still suffer from strong surface anisotropy. Herein, through the introduction of coating-layer, their infiltration abilities and isotropy are effectively improved. And, their physical-chemical properties can be recovered to that of commercial materials, containing compact-density, impurities-content and conductivities. The as-regenerated sample delivers a Li-storage capacity of 324 mA h g−1 at 1.0 C after 250 cycles. Even at high rates, their specific capacity can be still kept at about 286 mA h g−1 after 300 loops. Assisted by detailed electrochemical analysis, the pre-storage role of surface/near-surface layer is successfully confirmed, accompanied by stable charge balance. Moreover, its diffusion energy barrier of layers is further decreasing, accompanying with the considerable ion-diffusion behaviors. Therefore, the work is anticipated to provide significant surface-tailoring strategy for spent graphite, meanwhile illustrating the in-depth understanding of carbon-layers effect.