From Solid-Solution MXene to Cr-Substituted Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>: Breaking the Symmetry of Sodium Ions for High-Voltage and Ultrahigh-Rate Cathode Performance.
basic_science · Level V
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- Record sourced from PubMed, PMID 36394456.
- Also identified by DOI 10.1021/acsnano.2c09122.
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Abstract
Stabilizing Na<sup>+</sup> accessibility at high voltage and accelerating Na<sup>+</sup> diffusivity are pressing issues to further enhance the energy density of the Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> (NVP) cathode for sodium-ion batteries (SIBs). Herein, by taking a V/Cr solid-solution MXene as a precursor, a facile <i>in-situ</i> reactive transformation strategy to embed Cr-substituted NVP (NVCP) nanocrystals in a dual-carbon network is proposed. Particularly, the substituted Cr atom triggers the accessibility of additional Na<sup>+</sup> in NVCP, which is demonstrated by an additional reversible redox plateau at 4.0 V even under extreme conditions. More importantly, the Cr atom alters the Na<sup>+</sup> ordering at the Na2 sites with an additional intermediate phase formation during charging/discharging, thus reducing the energy barriers for Na<sup>+</sup> migration. As a result, Na<sup>+</sup> diffusivity in NVCP accelerates to 2-3 orders of magnitude higher than that of NVP. Eventually, the NVCP cathode exhibits extraordinarily high-rate capability (78 mA g<sup>-1</sup> at 200 C and 68975 W kg<sup>-1</sup>), outstanding cycle stability (over 1500 cycles at 10 C), excellent low-temperature property, and full cell performance.