Xie Yin, Jin Yongcheng, Xiang Lan
Department of Chemical Engineering , Tsinghua University , Beijing 100084 , China.
Qingdao Institute of Bioenergy and Bioprocess Technology , Chinese Academy of Sciences , Qingdao 266101 , China.
ACS Appl Mater Interfaces. 2019 Apr 24;11(16):14796-14802. doi: 10.1021/acsami.9b01651. Epub 2019 Apr 10.
The nontoxicity and low cost make LiMnO a competitive cathode material for lithium-ion batteries. LiMnO has a high theoretical capacity (296 mAh g) when cycled in the 3 and 4 V regions. However, it displays a low practical capacity (∼120 mAh g) because of the unavailability of the 3 V region caused by severe Jahn-Teller distortion. The present work investigated the full utilization of LiMnO in both 3 and 4 V by tuning the nanoscale interfacial properties. Li-rich structures at the surface and interface of the spinel material and nanograin strain were introduced to improve the performances and were achieved by grinding LiMnO and LiO at 700 rpm for 10 h under an argon atmosphere. The product shows a high initial discharge capacity of 287.9 mAh g at 0.05 C between 1.2 and 4.6 V and retains 83.2% of the capacity after 50 cycles. The nanoscale interfacial structure was clarified by spherical aberration-corrected microscopy and XRD refinement, and complex occupancies of Li and Mn were found at the interface. A correlation between the interfacial properties and electrochemical performance was established, and the improved performance could be attributed to the polycrystalline nature of the material, the unique Li-rich interfacial structure, and the slightly elevated valence state of Mn. The present results may provide insight for further evaluating the complex mechanism of controlling the electrochemical performance of LiMnO.
无毒且低成本使得LiMnO成为锂离子电池极具竞争力的正极材料。当在3V和4V区域循环时，LiMnO具有较高的理论容量（296 mAh g）。然而，由于严重的 Jahn-Teller 畸变导致3V区域不可用，它表现出较低的实际容量（约120 mAh g）。本工作通过调整纳米级界面性质研究了LiMnO在3V和4V区域的充分利用。通过在氩气气氛下以700 rpm研磨LiMnO和LiO 10小时，在尖晶石材料的表面和界面引入富锂结构和纳米晶粒应变以改善性能。该产品在1.2至4.6V之间以0.05 C的电流密度显示出287.9 mAh g的高初始放电容量，并且在50次循环后保留了83.2%的容量。通过球差校正显微镜和XRD精修阐明了纳米级界面结构，并且在界面处发现了Li和Mn的复杂占位。建立了界面性质与电化学性能之间的相关性，性能的改善可归因于材料的多晶性质、独特的富锂界面结构以及Mn价态的略微升高。目前的结果可能为进一步评估控制LiMnO电化学性能的复杂机制提供见解。
