Nano Hard Carbon Anodes for Sodium-Ion Batteries

Authors:Dae-Yeong Kim, Dong-Hyun Kim, Soo-Hyun Kim, Eun-Kyung Lee, Sang-Kyun Park, Ji-Woong Lee, Yong-Sup Yun, Si-Young Choi and Jun Kang

DOI: Nanomaterials 2019, 9(5), 793, doi.org/10.3390/nano9050793

Abstract

Graphite is the most widely used anode material in lithium-ion batteries (LIBs) owing to its rich reserves, good electrical conductivity, low charge/discharge potential, and excellent cycling stability. Unfortunately, the electrochemical performance of graphite as an anode material is poor in sodium-ion batteries (SIBs) using a conventional carbonate electrolyte. This is due to the passivation layer formed on the graphite surface being less effective than the protective layer formed in a LIB, and due to the continuous decomposition of electrolytes [1]. In addition, due to the thermodynamic instability of sodium, only a small amount of sodium can be stored in graphite. The sodium storage capacity of graphite in a SIB is approximately 1/10th of the lithium storage capacity in a LIB. The reason for this low reversible capacity is not simply the larger ionic radius of Na than that of Li (K is stored more in spite of its larger ionic radius than that of Na). It has been reported that sodium-graphite intercalation compounds (Na-GICs) are more thermodynamically unstable than other alkali-GICs.