Reichardt Martin, Sallard Sébastien, Novák Petr, Villevieille Claire
Electrochemical Energy Storage Section, Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2015 Dec 1;71(Pt 6):661-7. doi: 10.1107/S2052520615017539.
Lithium chromium pyrophosphate (LiCrP2O7) and carbon-coated LiCrP2O7 (LiCrP2O7/C) were synthesized by solid-state and sol-gel routes, respectively. The materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and conductivity measurements. LiCrP2O7 powder has a conductivity of ~ 10(-8) S cm(-1), ~ 10(4) times smaller than LiCrP2O7/C (~ 10(-4) S cm(-1)). LiCrP2O7/C is electrochemically active, mainly between 1.8 and 2.2 V versus Li(+)/Li (Cr(3+)/Cr(2+) redox couple), whereas LiCrP2O7 has limited electrochemical activity. LiCrP2O7/C delivers a reversible specific charge up to ~ 105 mAh g(-1) after 100 cycles, close to the theoretical limit of 115 mAh g(-1). Operando XRD experiments show slight peak shifts between 2.2 and 4.8 V versus Li(+)/Li, and a reversible amorphization between 1.8 and 2.2 V versus Li(+)/Li, suggesting an insertion reaction mechanism.
分别通过固态法和溶胶 - 凝胶法合成了焦磷酸锂铬（LiCrP₂O₇）和碳包覆的LiCrP₂O₇（LiCrP₂O₇/C）。通过X射线衍射（XRD）、热重分析（TGA）、扫描电子显微镜（SEM）和电导率测量对材料进行了表征。LiCrP₂O₇粉末的电导率约为10⁻⁸ S cm⁻¹，比LiCrP₂O₇/C（约10⁻⁴ S cm⁻¹）小约10⁴倍。LiCrP₂O₇/C具有电化学活性，主要在相对于Li⁺/Li（Cr³⁺/Cr²⁺氧化还原对）的1.8至2.2 V之间，而LiCrP₂O₇的电化学活性有限。LiCrP₂O₇/C在100次循环后可提供高达约105 mAh g⁻¹的可逆比电荷，接近115 mAh g⁻¹的理论极限。原位XRD实验表明，相对于Li⁺/Li，在2.2至4.8 V之间有轻微的峰位移，在相对于Li⁺/Li的1.8至2.2 V之间有可逆的非晶化，这表明存在嵌入反应机制。
