Preparation of LiFePO₄ for lithium ion battery using Fe₂P₂O₇ as precursor

Abstract

In order to obtain a new precursor for LiFePO₄, Fe₂P₂O₇ with high purity was prepared through solid phase reaction at 650 °C using starting materials of FeC₂O₄ and NH₄H₂PO₄ in an argon atmosphere. Using the as-prepared Fe₂P₂O₇, Li₂CO₃ and glucose as raw materials, pure LiFePO₄ and LiFePO₄/C composite materials were respectively synthesized by solid state reaction at 700 °C in an argon atmosphere. X-ray diffractometry and scanning electron microscopy(SEM) were employed to characterize the as-prepared Fe₂P₂O₇, LiFePO₄ and LiFePO₄/C. The as-prepared Fe₂P₂O₇ crystallizes in the C

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space group and belongs to β-Fe₂P₂O₇ for crystal phase. The particle size distribution of Fe₂P₂O₇ observed by SEM is 0.4–3.0 μm. During the Li⁺ ion chemical intercalation, radical P₂O₇⁴⁻ disrupted into two PO₄³⁻ ions in the presence of O²⁻, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO₄/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.

Keywords

lithium ion battery / cathode material / preparation / precursor / LiFePO₄ / Fe₂P₂O₇