Challenges for Na-ion Negative Electrodes

Na-ion batteries have been proposed as candidates for replacing Li-ion batteries. In this paper we examine the viability of Na-ion negative electrode materials based on Na alloys or hard carbons in terms of volumetric energy density. Due to the increased size of the Na atom compared to the Li atom, Na alloys would lead to negative electrode materials with roughly half the volumetric energy density of their Li analogs. Volumetric energy densities obtainable with sodiated hard carbons would also be significantly less than those obtainable with lithiated graphite. These findings highlight the need of novel ideas for Na-ion negative electrodes.