Energy efficient lattice and surface chemical regeneration of graphite from failed Li-ion batteries and its use as ultra-long cycling Na-ion battery anodes

Graphite being the most used anode in commercial lithium ion batteries (LIBs), haven't receive much attraction in recycling research. Also, graphite has limited attraction for Na-ion battery (NIB) applications due to poor intercalation. Tackling both these issues together, we present energy efficient recycling strategies for spent graphite (SG) delivering high rate and ultra-long cycling in NIBs. Three regeneration processes without high temperature annealing is reported, (i) solvent treatment (ii) solvent+acid and (iii) microwave assisted hydrothermal processing. Comprehensive structural, chemical and morphological characterizations were carried out for correlating with the performance. The solvent+acid treated SG exhibited ultra-long cycling stability (>36,000 cycles) and subsequently failed, delivering capacity retention of 97%. Whereas, microwave processed SG delivered 50,000 cycles without fail and 89% retention. In comparison, as-recovered SG failed within few thousand cycles under-same conditions. These unprecedented results establish that SG regenerated with energy efficient process is a potential anode for long-life NIB applications.