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<p>Complex phase transitions occur in P2-type materials during charging and discharging. A high-entropy structure can effectively inhibit the structural phase transition of a P2-type layered material. In this study, a high-temperature solid-phase method is used to synthesize the P2-type high-entropy fluorine oxide (HEFO) Na<sub>0.7</sub>Li<sub>0.08</sub>Mn(IV)<sub>0.21</sub>Mn(III)<sub>0.43</sub>Mg<sub>0.11</sub>Ni<sub>0.11</sub>W<sub>0.04</sub>Nb<sub>0.02</sub>O<sub>1.9</sub>F<sub>0.1</sub> [♦-NLM(IV)<sub>0.21</sub>M(III)<sub>0.43</sub>F (♦ = NMNW-O)], with a superlattice structure and Na<sub>2</sub>WO<sub>4</sub> coating. Na<sub>2</sub>WO<sub>4</sub> can effectively inhibit the complex phase transition to improve the structural stability of the material and overcome the limitations of P2-type Na<sub><i>x</i></sub>TMO<sub>2</sub> (TM = transition metal) via additional charge compensation. Adjusting the Mn<sup>3+</sup>/Mn<sup>4+</sup> ratio to increase the average valence state of Mn and introducing F<sup>−</sup> and Li<sup>+</sup> to inhibit the Jahn–Teller effect suppress the complex phase transition during charging and discharging. The material exhibits a good multiplicative performance (discharge specific capacity of 88.4&#xa0;mAh&#xa0;g<sup>−1</sup> at a multiplicative rate of 10C) and capacity retention (99.22% after 200 cycles at 1C in the potential window of 1.5–4.3&#xa0;V). The structural stabilities of HEFO are effectively demonstrated using electrochemical in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy. Theoretical calculations reveal that the high-entropy structure effectively improves the electronic structure and charge distribution of the layered oxide material. This study provides new concepts for use in developing novel energy batteries.</p> Graphical abstract <p></p>

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High-voltage stabilized high-entropy oxyfluoride cathode for high-rate sodium-ion batteries

  • 期刊论文

  • 发表日期：

    2025年4月1日

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  • Li He,
  • Tao Feng,
  • Qingqing Wu,
  • Yang Cao,
  • Fangxiang Song

摘要

Complex phase transitions occur in P2-type materials during charging and discharging. A high-entropy structure can effectively inhibit the structural phase transition of a P2-type layered material. In this study, a high-temperature solid-phase method is used to synthesize the P2-type high-entropy fluorine oxide (HEFO) Na0.7Li0.08Mn(IV)0.21Mn(III)0.43Mg0.11Ni0.11W0.04Nb0.02O1.9F0.1 [♦-NLM(IV)0.21M(III)0.43F (♦ = NMNW-O)], with a superlattice structure and Na2WO4 coating. Na2WO4 can effectively inhibit the complex phase transition to improve the structural stability of the material and overcome the limitations of P2-type NaxTMO2 (TM = transition metal) via additional charge compensation. Adjusting the Mn3+/Mn4+ ratio to increase the average valence state of Mn and introducing F− and Li+ to inhibit the Jahn–Teller effect suppress the complex phase transition during charging and discharging. The material exhibits a good multiplicative performance (discharge specific capacity of 88.4 mAh g−1 at a multiplicative rate of 10C) and capacity retention (99.22% after 200 cycles at 1C in the potential window of 1.5–4.3 V). The structural stabilities of HEFO are effectively demonstrated using electrochemical in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy. Theoretical calculations reveal that the high-entropy structure effectively improves the electronic structure and charge distribution of the layered oxide material. This study provides new concepts for use in developing novel energy batteries.

Graphical abstract