β‑FeOOH: An Earth-Abundant High-Capacity
Negative Electrode Material for Sodium-Ion Batteries
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Abstract
Thanks to the great earth abundance
and excellent energy density
of sodium, sodium-ion batteries are promising alternative energy storage
devices for large-scale applications. Developing cheap, safe, and
high-capacity sodium-ion battery anode materials is one of the critical
challenges in this field. Here, we show that β-FeOOH is a very
promising low-cost anode material, with a high reversible capacity
(>500 mAh g<sup>–1</sup> during initial cycles). The fundamental
characteristics associated with the discharge/charge processes, in
terms of the redox reactions, formation/deformation of the solid electrolyte
interface (SEI) layers, and structural and morphological changes,
are comprehensively investigated. In addition, a comparison study
shows that the smaller-sized FeOOH has more serious kinetic restrictions,
and thus lower capacities, while it shows better cyclability than
the bigger one. Origins of the large overpotential are discussed,
and it is suggested that the overpotential should be mainly due to
the features of the surface-concentration-dependent potential and
the slow diffusion of Na<sup>+</sup>; in addition, the presence of
the SEI layers may also contribute to the overpotential