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<p>Nickel-rich nickel phosphide (Ni<sub>2</sub>P) has emerged as a promising sodium-ion battery anode owing to its high theoretical capacity and intrinsic electronic conductivity, yet its charge storage chemistry remains controversial and is often oversimplified as a conversion reaction. Herein, we design a freestanding Ni<sub>2</sub>P composite electrode composed of ultrasmall Ni<sub>2</sub>P nanocrystals embedded within a phosphorus-doped, graphene-like porous carbon matrix. Comprehensive in-situ and <i>ex-situ</i> analyses unequivocally demonstrate an interstitial solid-solution mechanism, wherein Na<sup>+</sup> ions reversibly occupy lattice interstitials via (111)-oriented interplanar channels, inducing reversible lattice breathing without phase transformation. This bulk intercalation process is synergistically coupled with a substantial pseudocapacitive contribution, establishing a cooperative dual-mode storage mechanism. Benefiting from this solid-solution–capacitive chemistry, the electrode delivers a high reversible capacity (≈560 mAh g<sup>−1</sup>), outstanding rate capability (135 mAh g<sup>−1</sup> at 10 A g<sup>−1</sup>), and exceptional long-term stability (263 mAh g<sup>−1</sup> after 2000 cycles). When paired with a Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>@C cathode, the full cell achieves a high-energy density of 245 Wh kg<sup>−1</sup>. This work establishes solid-solution–capacitive coupling as a general paradigm for designing high-rate and durable sodium-ion battery anodes.</p><p></p>

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Beyond Conversion Chemistry: Unlocking a Cooperative Solid-Solution–Capacitive Sodium-Storage Mechanism in Nickel Phosphide

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月13日

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  • Jiaqin Liu,
  • Tongzhen Wang,
  • Jie Yang,
  • Yulei Li,
  • Zhaoqian Li,
  • Jiewu Cui,
  • Yan Yu,
  • Yucheng Wu

摘要

Nickel-rich nickel phosphide (Ni2P) has emerged as a promising sodium-ion battery anode owing to its high theoretical capacity and intrinsic electronic conductivity, yet its charge storage chemistry remains controversial and is often oversimplified as a conversion reaction. Herein, we design a freestanding Ni2P composite electrode composed of ultrasmall Ni2P nanocrystals embedded within a phosphorus-doped, graphene-like porous carbon matrix. Comprehensive in-situ and ex-situ analyses unequivocally demonstrate an interstitial solid-solution mechanism, wherein Na+ ions reversibly occupy lattice interstitials via (111)-oriented interplanar channels, inducing reversible lattice breathing without phase transformation. This bulk intercalation process is synergistically coupled with a substantial pseudocapacitive contribution, establishing a cooperative dual-mode storage mechanism. Benefiting from this solid-solution–capacitive chemistry, the electrode delivers a high reversible capacity (≈560 mAh g−1), outstanding rate capability (135 mAh g−1 at 10 A g−1), and exceptional long-term stability (263 mAh g−1 after 2000 cycles). When paired with a Na3V2(PO4)3@C cathode, the full cell achieves a high-energy density of 245 Wh kg−1. This work establishes solid-solution–capacitive coupling as a general paradigm for designing high-rate and durable sodium-ion battery anodes.