The electrochemical mechanism and performance of FeSi₄P₄, vs. Na and Li were studied using a combination of operando X-ray diffraction, ⁵⁷Fe Mössbauer spectroscopy, and SQUID magnetometry. This silicon- and phosphorous-rich material exhibits a high capacity of 1750 mAh/g, retaining 1120 mAh/g after 40 cycles, and reacts through an original reversible mechanism surprisingly involving only slight changes in the chemical environment of the iron. Magnetic measurements and ⁵⁷Fe Mössbauer spectroscopy at low temperature reveal the reversible but incomplete change of the magnetic moment upon charge and discharge. Such a mild reversible process without drastic phase transition (with the exception of the crystalline to amorphous transition during the first lithiation) can explain the satisfying capacity retention. The electrochemical mechanism appears thus to be significantly different from the classical conversion or alloying/dealloying mechanisms usually observed in Lithium ion batteries for p-group element based materials. The same iron silicon phosphide electrode shows also interesting but significantly lower performance vs. Na, with a limited capacity retention 350 mAh/g.

利用操作X射线衍射，⁵⁷ FeMössbauer光谱和SQUID磁力分析技术研究了FeSi ₄ P ₄相对于Na和Li的电化学机理和性能。这种富含硅和磷的材料表现出1750 mAh / g的高容量，在40次循环后保持1120 mAh / g，并通过原始的可逆机制发生反应，令人惊奇地仅涉及铁的化学环境的微小变化。磁测量和⁵⁷FeMössbauer光谱在低温下揭示了充放电时磁矩的可逆但不完全变化。这种温和的可逆过程而没有剧烈的相变（在第一次锂化过程中从晶体到非晶态的转变除外）可以解释令人满意的容量保持率。因此，电化学机理似乎与通常在锂离子电池中对基于p-族元素的材料中观察到的经典转化或合金化/脱合金机理显着不同。相同的磷化硅铁电极也表现出有趣的性能，但相对于Na却表现出明显较低的性能，有限的容量保持力为350 mAh / g。