Graphite Cone/Disc Anodes as Alternative to Hard Carbons for Na/K-Ion Batteries

Abstract

As sodium-ion batteries compete for dominance in the energy storage market, the problem arises when using traditional graphitic anodes. Graphitic anodes used in Li-ion batteries do not work well due to the limitation of Na-ion diffusion and intercalation into graphite lattice. It is demonstrated that graphitic carbon cones and disks, manufactured via the scalable pyrolysis of hydrocarbons, are viable anode candidates for Na-ion and K-ion batteries. These distinctive pure graphitic carbon structures, without any heteroatoms present, show excellent Na-ion intercalation, exhibiting a reversible capacity of ≈230 mAh g⁻¹ at a current rate of 20 mA g⁻¹ and excellent rate performance. The electrode has also been shown to exhibit excellent performance in K-ion intercalation. Ex situ TEM analysis (at room and cryo temperatures) and solid-state NMR spectroscopy show intercalated sodium and potassium evidence, revealing the charge storage mechanism. These pure graphitic structures can be a potential anode candidates for the next generation of beyond-lithium batteries due to their morphologies that allow for reversible intercalation of larger ions without structural modifications.