高密度球形LiCoO_2的制备及性能研究

Preparation and characterization of high-density spherical LiCoO_2

球形化是LiCoO2正极材料的重要发展方向。采用控制结晶法合成球形b -Co(OH)2为前驱体,与Li2CO3混合,在750 ℃热处理16 h合成球形LiCoO2粉末。用X射线衍射和扫描电镜分析对b -Co(OH)2和LiCoO2粉末的结构进行了表征。充放电测试表明该球形LiCoO2正极材料具有优良的电化学性能:当充放电电流分别为0.2 C、1.0 C时,材料首次放电比容量分别为148.4 mAh·g-1和141.7 mAh·g-1,40次充放电循环后分别保持初始放电比容量的97.6%和91.7%。该球形LiCoO2粉末的松装密度高达1.9 g·cm-3,振实密度高达2.8 g·cm-3,远高于一般非球形LiCoO2正极材料。高密度球形LiCoO2正极材料用于锂离子蓄电池可以显著提高电池的比能量。

The spherical LiCoO2 is expected as an important direction for LiCoO2 cathode material. Spherical b -Co(OH)2 powders were prepared via a 'controlled crystallization' method. The spherical LiCoO2 powders were synthesized by sintering the b -Co(OH)2 precursor mixed with Li2CO3 at 750 ℃ for 16 h. The structures of b -Co(OH)2 and LiCoO2 were characterized by XRD and SEM. Electrochemical test of charge-discharge proved the spherical LiCoO2 cathode material had excellent electrochemical performance. At the current of 0.2 C and 1.0 C, the cathode material shows initial discharge capacity of 148.4 mAh·g-1 and 141.7 mAh·g-1, and retention of 97.6 % and 91.7% after 40 cycles respectively. The lax pile-density and tap-density of the powders are as high as 1.9 g·cm-3 and 2.8 g·cm-3 respectively, which are remarkably higher than the non-spherical LiCoO2 cathode materials. The high-density spherical LiCoO2 cathode material can be used in the lithium ion batteries to greatly increase the batteries' energy density.