Safety is important to lithium ion battery materials. The thermal stability of LiFePO_4/C-LiMn_2O_4 blended cathode materials is characterized by using TG, XRD, and SEM etc. The results show that LiFePO_4/C-LiMn_2O_4 possesses a worse thermal stability than pure spinel LiMn_2O_4 and pure olivine LiFePO_4/C. When LiFePO_4/C-LiMn_2O_4 blended cathode materials are sintered at 500°C under Ar atmosphere, the sintered cathode materials emit O_2, and appear impurity phases(Li_3PO_4, Fe_2O_3, Mn_3O_4). It is deduced that some chemical reactions take place between different materials, which leads to a worse discharge specific capacity. LiFePO_4/C-LiMn_2O_4 blended cathode materials, therefore, need to be managed and controlled strictly for the sake of thermal stability and safety.
DU YuanChaoHUANG XiaoPengZHANG KeYuLIANG FengLI QiuXiaYAO YaoChunDAI YongNian
以工业级Li_2CO_3为原料,氢化分解法提纯制备电池级Li_2CO_3,初步探索了Li3PO4除Ca的可行性,研究了Li_3PO_4加入量、反应温度、反应时间对除Ca效果及产品产率的影响。研究表明,10 g量级Li_2CO_3原料反应得到的300 m L LiHCO_3溶液,加入1g Li_3PO_4,在50℃下反应2 h,Ca脱除率最高,所得Li_2CO_3产品中Ca含量接近电池级Li_2CO_3行业标准。
液相合成法具有传热、传质快,材料粒径、形貌可控等优点,被广泛应用于各类材料制备领域。本文综述了共沉淀法、溶剂热法、sol-gel法合成磷酸铁锂正极材料的过程、原理和研究进展,并进行了对比和总结:纳米化、高比表面积、碳包覆,可以解决电子电导率低和锂离子扩散速率慢所导致的倍率性能差的问题,是液相法合成的基本要求。共沉淀法有利于合成密堆积的球形形貌,获得高振实密度的材料,可以提高材料的能量密度。溶剂热法有利于合成大(010)面的材料,缩短锂离子扩散的距离,提高材料的倍率性能。Solgel法可以达到分子级别的混合,有利于制备成分均匀、原位碳包覆的材料。使用高电子电导率和离子电导率的材料,可以提高Li Fe PO4的倍率性能。相对固相法,寻找合成时间短、流程短、成本低的产业化方法,推动液相法在原理、工艺上的发展和进步是研究的方向。
