Cobalt Nanoparticles Chemically Bonded to Porous Carbon Nanosheets: A Stable High-Capacity Anode for Fast-Charging Lithium-Ion Batteries

A two-dimensional electrode architecture of ∼25 nm sized Co nanoparticles chemically bonded to ∼100 nm thick amorphous porous carbon nanosheets (Co@PCNS) through interfacial Co–C bonds is reported for the first time. This unique 2D hybrid architecture incorporating multiple Li-ion storage mechanisms exhibited outstanding specific capacity, rate performance, and cycling stabilities compared to nanostructured Co 3 O 4 electrodes and Co-based composites reported earlier. A high discharge capacity of 900 mAh/g is achieved at a charge–discharge rate of 0.1C (50 mA/g). Even at high rates of 8C (4 A/g) and 16C (8 A/g), Co@PCNS demonstrated specific capacities of 620 and 510 mAh/g, respectively. Integrity of interfacial Co–C bonds, Co nanoparticles, and 90% of the initial capacity are preserved after 1000 charge–discharge cycles. Implementation of Co nanoparticles instead of Co 3 O 4 restricted Li 2 O formation during the charge–discharge process. In situ formed Co–C bonds during the pyrolysis steps improve interfacial charge transfer, and eliminate particle agglomeration, identified as the key factors responsible for the exceptional electrochemical performance of Co@PCNS. Moreover, the nanoporous microstructure and 2D morphology of carbon nanosheets facilitate superior contact with the electrolyte solution and improved strain relaxation. This study summarizes design principles for fabricating high-performance transition-metal-based Li-ion battery hybrid anodes.