单晶LiNi0.6Co0.2Mn0.199Zr0.001O2材料的合成及性能改善研究

Research on synthesis and performance improvement of single crystal LiNi0.6Co0.2Mn0.199Zr0.001O2

利用共沉淀反应合成Ni0.6Co0.2Mn0.199Zr0.001(OH)2前驱体,配锂经900℃高温烧结12h制得平均粒径为3~5 μm的Li Ni0.6Co0.2M n0.199Zr0.001O2单晶材料.经喷雾干燥及450℃高温分解4h制得Al2O3包覆单晶LiN i0.6Co0.2Mn0.199Zr0.001O2复合材料.利用X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、透射电子显微镜法(TEM)、电感耦合等离子体光谱分析法(ICP)对材料进行分析,结果表明:Al2O3以非晶态包覆于颗粒表面且不改变材料的晶体结构与形貌特征;包覆0.25%(质量分数)Al2O3材料首次放电比容量为163.4 mAh/g,0.2 C下循环100次后容量保持率为98.69%,5 C/0.2 C容量保持率为78.6%;包覆Al2O3有效降低了电极阻抗,抑制了过渡金属离子溶解,包覆0.25% Al2O3的材料阻抗最小,电解液中过渡金属离子含量也最低.综合性能的提升证明Al2O3包覆层能抑制活性物质与电解液界面副反应,提高材料的结构稳定性.

Ni0.6Co0.2Mn0.199Zr0.001(OH)2 and single crystal LiNi0.6Co0.2Mn0.199Zr0.001O2 material with average diameter of 3-5μm were synthesized by co-precipitation reaction and high temperature sintering(900 ℃-12 h). The single crystal Li Ni0.6 Co0.2 Mn0.199 Zr0.001 O2 material was coated with Al2O3 by spray drying and following heat treatment(450 ℃-4 h).The prepared samples were characterized by XRD, SEM, TEM and ICP. The results show that amorphous Al2O3 is coated well on the surface of Li Ni0.6 Co0.2 Mn0.199 Zr0.001 O2 and makes no change for the local structure. The sample coated with 0.25% Al2O3 can deliver an initial specific capacity of 163.4 m Ah/g(2.8-4.25 V, 0.1 C), the capacity retention is 98.69% after 100 cycles at 0.2 C(2.8-4.5 V), and the capacity ratio of 5 C/0.2 C is 78.6%. Impedance and content of Ni, Co, and Mn in electrolyte of the sample coated with 0.25% Al2O3 are lower than other samples. It is confirmed that the Al2O3 layer can restrain side reactions at electrode/electrolyte interface, inhibit the dissolution of transition metal ions into the electrolyte, apparently suppress the increase of resistance and enhance structure stability.