Harbin Institute of Technology, School of Chemical Engineering and Technology, Xidazhi Street, 150001 Harbin, China.
Harbin Institute of Technology, School of Materials Science and Engineering, 150001 Harbin, China.
Nanoscale. 2019 Mar 7;11(9):3933-3944. doi: 10.1039/c8nr10224d. Epub 2019 Feb 14.
LiMnFePO (LMFP) has attracted extensive interest owing to its high safety and appropriate redox potential. Nevertheless, its poor electrochemical kinetics and structural instability, depending on its manganese content, are still limiting its further application. Herein, we realize a concentration-gradient LiMnFePO hollow sphere cathode material with a carbon coating (HCG-LMFP/C) by a facile and controllable two-step solvothermal approach. On the one hand, the porous hollow architecture can sustain excellent structural stabilization against the volume changes that occur during repeated Li intercalation/deintercalation. On the other hand, the unique concentration-gradient structure with its Fe-rich surface can not only relieve interface deterioration and improve the ionic/electric conductivity due to the active nature of LiFePO, but also guarantees the chemical stability of the LMFP against electrolyte attack and remarkably reduces Mn dissolution, even at elevated temperature. Therefore, the obtained concentration-gradient HCG-LMFP/C cathode shows improved high-rate performance (111 and 78 mA h g at 20 and 60C rates, respectively) and excellent capacity retention (96% after 1000 cycles at the 10C rate) as well as outstanding temperature tolerance (over a temperature range from 40 °C to -10 °C). More importantly, the present gradient strategy opens up a new window for designing high-performance and stable olivine cathodes, which could also be compatible with many other energy-storage materials for various applications.
LiMnFePO（LMFP）因其高安全性和适当的氧化还原电位而引起了广泛的关注。然而，其较差的电化学动力学和结构不稳定性（取决于其锰含量）仍然限制了其进一步的应用。在此，我们通过简便可控的两步溶剂热法实现了具有碳涂层的浓度梯度 LiMnFePO 空心球阴极材料（HCG-LMFP/C）。一方面，多孔空心结构能够在反复的 Li 嵌入/脱嵌过程中保持出色的结构稳定性，以应对体积变化。另一方面，具有富铁表面的独特浓度梯度结构不仅由于 LiFePO 的活性可以缓解界面恶化并提高离子/电子导电性，而且还可以保证 LMFP 对电解质侵蚀的化学稳定性，并显著减少 Mn 的溶解，即使在高温下也是如此。因此，所获得的浓度梯度 HCG-LMFP/C 阴极表现出改善的高倍率性能（在 20 和 60C 速率下分别为 111 和 78 mA h g）和出色的容量保持率（在 10C 速率下循环 1000 次后保持 96%）以及出色的温度耐受性（在 40°C 至-10°C 的温度范围内）。更重要的是，本研究中的梯度策略为设计高性能和稳定的橄榄石阴极开辟了新的窗口，这也可以与许多其他储能材料兼容，适用于各种应用。
