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采用悬浮液混合法在热处理温度为400℃的条件下制备了石墨烯改性Li Fe PO_4/C复合正极材料。利用X射线衍射分析、扫描电子显微镜、透射电子显微镜等对石墨烯改性Li Fe PO_4/C正极材料的组成、结构和形貌进行了表征,并组装扣式电池,在2.0~4.2 V电压范围下测试了其–10℃时的电化学性能。结果表明,5%(质量分数,下同)石墨烯改性的正极粉未样品G5颗粒分布均匀,石墨烯构成了三维导电网络;相比其它组分,样品G5在1C倍率下具有最高的放电容量(115.4 m A·h/g),循环200次后容量保持率为93.6%;同时,样品G5具有最低的电荷转移阻抗(106.9W)和最高的锂离子扩散系数(7.12×10~(–11) cm~2/s)。
The graphene modified LiFe PO 4 / C composite cathode material was prepared by the suspension mixing method at a heat treatment temperature of 400 ℃. The composition, structure and morphology of the graphene modified LiFePO 4 / C cathode material were characterized by X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. A button cell was assembled. The cell voltage was in the range of 2.0-4.2 V The electrochemical properties at -10 ° C were tested. The results show that 5% (mass fraction, same below) graphene modified positive electrode powder sample G5 particles are evenly distributed, graphene constitutes a three-dimensional conductive network; compared to other components, sample G5 has the highest discharge at 1C rate (115.4 m A · h / g). After 200 cycles, the capacity retention was 93.6%. Meanwhile, the lowest charge transfer resistance (106.9W) and the highest lithium ion diffusion coefficient (7.12 × 10 ~ 11) cm ~ 2 / s).