A 3.8-V earth-abundant sodium battery electrode

TLDR

Rechargeable lithium batteries have enabled the wireless revolution, but lithium scarcity and the low voltage and sluggish kinetics of sodium‑ion batteries drive the search for earth‑abundant alternatives. The study aims to demonstrate a rare‑metal‑free Na‑ion battery system compatible with existing Li‑ion technology that maintains high energy density and power, enabling the discovery of new earth‑abundant cathodes for large‑scale batteries. The authors synthesize an alluaudite‑type sulfates Na₂Fe₂(SO₄)₃ cathode that delivers a 3.8‑V Fe³⁺/Fe²⁺ redox potential and rapid kinetics. The Na₂Fe₂(SO₄)₃ cathode achieves a record 3.8‑V Fe³⁺/Fe²⁺ redox potential versus Na (4.1 V vs Li) and exhibits fast rate kinetics.

Abstract

Abstract Rechargeable lithium batteries have ushered the wireless revolution over last two decades and are now matured to enable green automobiles. However, the growing concern on scarcity and large-scale applications of lithium resources have steered effort to realize sustainable sodium-ion batteries, Na and Fe being abundant and low-cost charge carrier and redox centre, respectively. However, their performance is limited owing to low operating voltage and sluggish kinetics. Here we report a hitherto-unknown material with entirely new composition and structure with the first alluaudite-type sulphate framework, Na 2 Fe 2 (SO 4 ) 3 , registering the highest-ever Fe 3+ /Fe 2+ redox potential at 3.8 V (versus Na, and hence 4.1 V versus Li) along with fast rate kinetics. Rare-metal-free Na-ion rechargeable battery system compatible with the present Li-ion battery is now in realistic scope without sacrificing high energy density and high power, and paves way for discovery of new earth-abundant sustainable cathodes for large-scale batteries.