Regulating Na content and Mn defects in birnessite for high-voltage aqueous sodium-ion batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 40268928.
- Also identified by DOI 10.1038/s41467-025-59223-1 and PMC identifier 12019187.
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Abstract
Na-birnessite is a promising low-cost positive electrode material for aqueous sodium-ion batteries. However, its sodium storage capability is limited by narrow potential window and low redox activity in aqueous electrolytes. Herein, a Na-rich birnessite (NaMnO<sub>2</sub>•0.1H<sub>2</sub>O) with a highly ordered layered structure is reported as an advanced positive electrode for aqueous sodium-ion batteries, greatly suppressing Mn migration and its accompanying domino degradation effect, which enables a promoted upper charging cut-off potential up to 1.4 V (vs. Ag/AgCl), an enhanced specific capacity of 199.9 mAh g<sup>-1</sup> at a specific current of 0.2 A g<sup>-</sup><sup>1</sup> based on the mass of active material for positive electrode, and greatly improved structural stability. In particular, a 3.0 V Na<sub>x</sub>H<sub>2-x</sub>Ti<sub>2</sub>O<sub>5</sub>||NaMnO<sub>2</sub>•0.1H<sub>2</sub>O aqueous full cell prototype is validated, exhibiting a large specific energy of 117.1 Wh kg<sup>-</sup><sup>1</sup> based on the total mass of active materials in both positive and negative electrodes as well as a long cycle life. This work elucidates how interlayer chemistry and structural defects influence sodium ion storage in layered structures and provides opportunities for developing high-voltage aqueous batteries with large specific energy.