PNNL

Abstract

Serious critical issues hamper the arrival on the market of sodium-ion batteries (SIBs) as a lower cost substitute to Li-ion batteries (LIBs). Among these, the negligible sodium uptake into graphite, which is the keystone of the present LIB technology, appears to be one of the toughest to tackle. Although hard carbon is known for years as one of the best substitutes, its performance remains below that of graphite in Li-ion batteries, while its mechanism of sodium storage is still under debate. Many other carbons are studied since a few years, some of which presenting capacities far beyond that of graphite. However, they tend to present larger voltage and high first cycle loss, leading to limited benefit in terms of specific energy at full cell level. Overcoming this preoccupying tradeoff requires a deep understanding of the charge storage mechanisms and the correlation between structure, microstructure and performance. The present Review aims at bringing light to this question by drawing a roadmap of the emerging routes for the optimization of carbon materials as SIB anode, on the basis of a critical survey of their reported electrochemical performance and charge storage mechanisms.