类球形正交LiMnO_2的制备、微结构和电化学性能

Preparation,Microstructure and Electrochemical Properties of Spherical-like Orthorhombic LiMnO_2

以共沉淀法得到的类球形MnCO3为前驱物,制备了类球形正交LiMnO2(So-LiMnO2),采用XRD、SEM和N2吸附技术对样品进行表征;与非球形正交LiMnO2(No-LiMnO2)进行了对比研究。结果表明:o-LiMnO2的堆垛层错度、结晶状况、颗粒形貌和大小与前驱物的微结构密切相关;在80次电化学循环测试过程中,So-LiMnO2经15次循环可达最大的放电容量152mAh·g-1,其容量衰减平均每次循环0.58mAh·g-1;而No-LiMnO2要经过38次循环才能达到最大放电容量128mAh·g-1,容量衰减平均每次循环高达1.24mAh·g-1。TEM和EDS分析证明:由一次粒子团聚的类球形So-LiMnO2能有效地抑制电解液对材料的腐蚀、减少Mn的溶解,从而提高了电化学循环能力。

Spherical-like morphology orthorhombic LiMnO2 （So-LiMnO2） powders were prepared using spherical MnCO3 precursors obtained by a carbonate co-precipitation method. The materials were characterized using XRD, SEM and low temperature nitrogen adsorption desorption. Non-spherical orthorhombic LiMnO2 （No-LiMnO2） powders were also studied for comparison. The characteristics of o-LiMnO2 such as the stacking faults, crystallization, particles morphology and size were significantly dependent on the microstructure of precursors. The electrochemical performances of o-LiMnO2-based cathodes were tested during 80 cycles. The So-LiMnO2 cathode had a maximum capacity of 152 mAh·g^-1 on the 15th cycle, and exhibited an average capacity decay of approximately 0.58 mAh·g^-1 per cycle. By contrast, the No-LiMnO2 sample had a maximum capacity of 128 mAh·g^-1 on the 38th cycle, and experienced an average capacity decay of 1.24 mAh·g^-1 per cycle. TEM observation and EDS analysis confirmed that So-LiMnO2 particle, agglomerated by primary particles, could reduce the erosion of positive material by electrolytes and the dissolution of manganese, which results in the enhanced electrochemical cycleability.