Zhong Wentao, Huang Qianhui, Zheng Fenghua, Deng Qiang, Pan Qichang, Liu Yanzhen, Li Youpeng, Li Yijuan, Hu Junhua, Yang Chenghao, Liu Meilin
Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China.
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China.
ACS Appl Mater Interfaces. 2020 Oct 21;12(42):47548-47555. doi: 10.1021/acsami.0c13278. Epub 2020 Oct 8.
Tunnel-type (T-type) NaMnO (NMO) is a promising cathode material for sodium-ion batteries (SIBs) owing to its high rate performance and cycling stability compared to manganese-based layered oxides. However, the low specific capacity still restricts its practical applications. Herein, a Co-doped T-type NMO is synthesized through a facile solid-state reaction method and utilized as a cathode material for SIBs. A T-type NaMnCoO (NMO-3) electrode can deliver a high reversible capacity of 138 mAh g at 0.1C, a superior rate capability (133, 130, 121, 106, and 93 mAh g at 0.5, 1, 2, 5, and 10C, respectively), and excellent cycling stability (85.2% at 10C after 500 cycles). The substitution of Co by Mn leads to the enlargement of small and S-shaped tunnel spaces, which facilitates the insertion/deinsertion of Na into/from NMO-3 and greatly enhances its rate capability and cycling stability. Moreover, the reduced energy barriers for Na diffusion in small tunnels make the inactive Na easier to be deintercalated, which should be responsible for its high specific capacity that exceeds the theoretical capacity of T-type NMO.
隧道型（T型）NaMnO（NMO）由于与锰基层状氧化物相比具有高倍率性能和循环稳定性，是一种很有前景的钠离子电池（SIBs）正极材料。然而，低比容量仍然限制了其实际应用。在此，通过简便的固态反应方法合成了一种Co掺杂的T型NMO，并将其用作SIBs的正极材料。T型NaMnCoO（NMO-3）电极在0.1C时可提供138 mAh g的高可逆容量、优异的倍率性能（在0.5、1、2、5和10C时分别为133、130、121、106和93 mAh g）以及出色的循环稳定性（在10C下500次循环后为85.2%）。Co对Mn的取代导致小的和S形隧道空间的扩大，这有利于Na在NMO-3中的嵌入/脱出，并大大提高了其倍率性能和循环稳定性。此外，小隧道中Na扩散的能量势垒降低使得非活性Na更容易脱嵌，这应该是其高比容量超过T型NMO理论容量的原因。
