Facile synthesis of ultrathin carbon nanosheets through NaCl-KCl templates coupled with ice-induced assembly strategy from carbon quantum dots as lithium-ion batteries anodes

Carbon nanosheets (CNSs) have drawn numerous attention as promising anodes in energy storage devices due to their large specific surface area and excellent electrical conductivity close to graphene materials. Restricted by the expensive raw materials, harsh conditions and cumbersome post-processing procedures, the large-scale production of CNSs is a major challenge. Herein, ultrathin CNSs were constructed through NaCl-KCl templates coupled with ice-induced assembly strategy from coal tar pitch-based carbon quantum dots (CQDs). The ice can manipulate the salt crystal growth direction and dominantly guide the distribution of CQDs on the surface of NaCl-KCl crystal templates, whereas the liquid salts not only act as the solvent to load and disperse CQDs but as molecular templates to facilitate the formation of ultrathin CNSs during the carbonization process. The prepared CNSs exhibit twisted and ultrathin lamellar structures with a thickness of ∼1.70 nm, abundant hierarchical nanopores, and a moderate specific surface area of 302.00 m2·g−1. Benefiting from these unique microstructure features, the optimized CNS-3 adopted as anode for lithium-ion batteries displays prominent electrochemical features with high reversible capacity (453 mAh·g−1 at 50 mA·g−1), outstanding rate capability (225 mAh·g−1 at 1000 mA·g−1), and superior cycle stability (94.3% capacitance retention after 500 cycles at 500 mA·g−1). Our work provides a novel and effective approach to fabricate ultrathin carbon nanosheets by employing low-cost carbon quantum dots derived from coal tar pitch as potential candidates applied for lithium-ion batteries and next-generation energy storage devices.