新型复合共沉淀法制备高能量/高功率型锂离子二次电池用5V正极材料LiNi_(0.5)Mn_(1.5)O_4及其电化学性能

在传统的固相法的基础上开发了新型复合共沉淀法制备LiNi0.5Mn1.5O4材料.新型复合共沉淀法采用(NH4)2CO3和(NH4)2C2O4共同作为沉淀剂,通过控制共沉淀反应条件,得到了具有均匀球形形貌的沉淀物颗粒.再通过与饱和氢氧化锂溶液的水热反应及高温反应,最终制备出具有球形次级形貌和纯相尖晶石结构的LiNi0.5Mn1.5O4材料.电化学测试表明,制备的LiNi0.5Mn1.5O4具有优异的电化学性能,其初始容量达到了141.4mAh·g-1.在0.3C、1C和3C倍率下经过200次循环后的容量分别为136.0 mAh·g-1(96.3%)、128.6 mAh·g-1(94.4%)和113.9 mAh·g-1(91.1%).通过高温反应及特殊的冷却处理,LiNi0.5Mn1.5O4在4.0 V低压区平台的容量损失得到了有效抑制.更重要的是,通过控制合成过程中的关键步骤,可实现半定量化控制材料结构中的原子有序排布程度,进而得到具有高能量密度和高功率密度的两种LiNi0.5Mn1.5O4材料,其能量密度和功率密度分别达到了648.6 mWh·g-1和7000 mW·g-1以上.

Preparation and Electrochemical Performance of 5 V LiNi0.5Mn1.5O4 Cathode Material by the Composite Co-Precipitation Method for High Energy/High Power Lithium Ion Secondary Batteries

This research developed a novel composite co-precipitation method to prepare high performance LiNi_0.5Mn_1.5O₄ based on a traditional solid-state method. Ammonium oxalate/ammonium carbonate was used as a composite precipitator to deposit Ni/Mn ions. Combined with a facile hydrothermal treatment, stoichiometric LiNi_0.5Mn_1.5O₄ was obtained with a pure spinel structure and spherical hierarchical morphology. Electrochemical measurements indicate that the as-prepared LiNi_0.5Mn_1.5O₄ delivers a high capacity of 141.4 mAh·g^-1 and after 200 cycles under 0.3C, 1C, and 3C, the materials retained their capacities up to 96.3%, 94.4%, and 91.1%, respectively. Additionally, the capacity upon exposure to a low voltage of 4.0 V was efficiently eliminated by heat treatment and by a particular cooling process. Furthermore, the LiNi_0.5Mn_1.5O₄ materials with high energy and high power performances of 648.6 mWh·g^-1 and 7000mW·g^-1 were obtained because of different cation ordering.