不同锂源对高温固相法制备NCM811正极材料储锂性能的影响

Influence of Lithium Sources on the Lithium ion Storage Performance of NCM811 Cathode Materials Prepared by High-Temperature Solid-State Reaction Method

摘要:

采用4种不同的锂盐(LiOH.H₂O、Li₂CO₃、LiNO₃、CH₃COOLi),以高温固相法制备了LiNi_0.8Co_0.1Mn_0.1O₂正极材料。利用X射线粉末衍射(XRD)和场发射电子显微镜(FESEM)对所制LiNi_0.8Co_0.1Mn_0.1O₂材料的微观结构进行了表征,发现所有合成的LiNi_0.8Co_0.1Mn_0.1O₂样品尺寸均为微米级大小,具有层状结构(R-3m空间群)。电化学测试结果表明采用不同锂源制备的LiNi_0.8Co_0.1Mn_0.1O₂样品的电化学性能差别很大。其中采用LiOH?H₂O为锂源,经500 °C预烧结6 h后,在800 °C下烧结16 h获得的样品锂镍混排程度最低,电化学性能最佳。例如,在0.1 C(1 C=180 mA/g)倍率下其可逆比容量高达206.2 mA.h/g,在10 C大倍率下,其可逆比容量仍保持有80.9 mA.h/g；在0.5 C倍率下100次充放电循环过程中,最高放电比容量为176.2 mA.h/g,平均放电比容量为140.1 mA.h/g。动力学及电极稳定性分析发现,LiOH?H₂O制备的样品的电化学可逆性最好,Li^₊扩散系数最大,充放电循环过程中结构稳定性最好。

Abstract:

LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials were prepared by a high-temperature solid-phase reaction method with Four different lithium salts (LiOH.H₂O, Li₂CO₃, LiNO₃, CH₃COOLi) as lithium sources. The microstructure of the LiNi_0.8Co_0.1Mn_0.1O₂ materials was characterized by X-ray powder diffraction (XRD) and field emission electron microscopy (FESEM). The results demonstrated that the size of all the four synthesized LiNi_0.8Co_0.1Mn0.1O₂ samples were micrometers size, with a layered structure (R-3m space group). The electrochemical test results showed that the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ samples prepared with different lithium sources is very different. Among them, the LiNi_0.8Co_0.1Mn_0.1O₂ sample prepared with LiOH?H₂O as lithium source (pre-sintering at 500 °C for 6 h and sintering at 800 °C for 16 h) exhibited the lowest degree of lithium-nickel mixing and the best electrochemical performance. For example, its reversible specific capacity is as high as 206.2 mA.h/g at a rate of 0.1 C (1 C=180 mA/g), and its reversible specific capacity remains 80.9 mA.h/g at a rate of 10 C; During 100 charge-discharge cycles at a rate of 0.5 C, the highest specific discharge capacity was 176.2 mA.h/g, and the average specific discharge capacity was 140.1 mA.h/g. The analysis of kinetics and electrode stability revealled that the LiNi_0.8Co_0.1Mn_0.1O₂ sample prepared with LiOH?H₂O as lithium source possessed the best electrochemical reversibility, highest Li^₊ diffusion coefficient, and superior structural stability during charge-discharge cycling.