High-power Na-ion batteries have tremendous potential in various large-scale applications. However, conventional charge storage through ion intercalation or double-layer formation cannot satisfy the requirements of such applications owing to the slow kinetics of ion intercalation and the small capacitance of the double layer. The present work demonstrates that the pseudocapacitance of the nanosheet compound MXene Ti2C achieves a higher specific capacity relative to double-layer capacitor electrodes and a higher rate capability relative to ion intercalation electrodes. By utilizing the pseudocapacitance as a negative electrode, the prototype Na-ion full cell consisting of an alluaudite Na2Fe2(SO4)3 positive electrode and an MXene Ti2C negative electrode operates at a relatively high voltage of 2.4 V and delivers 90 and 40 mAh g−1 at 1.0 and 5.0 A g−1 (based on the weight of the negative electrode), respectively, which are not attainable by conventional electrochemical energy storage systems.
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机译：高功率钠离子电池在各种大规模应用中具有巨大的潜力。然而，由于离子嵌入的动力学慢和双层的小电容，通过离子嵌入或双层形成的常规电荷存储不能满足这种应用的要求。本工作表明，相对于双层电容器电极，纳米片化合物MXene Ti2C的拟电容实现了更高的比容量，并且相对于离子嵌入电极实现了更高的倍率能力。通过使用拟电容作为负极，由铝辉石Na2Fe2（SO4）3正极和MXene Ti2C负极组成的原型Na离子全电池在2.4 V的较高电压下工作，可提供90和40 mAh g <分别为1.0和5.0 A g -1 （基于负极的重量）的sup> -1 ，这是常规电化学储能系统无法达到的。
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