Zang Xining, Wang Shuo, Zhang Ruopeng
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Tsinghua University, Beijing 100084, China.
J Phys Chem Lett. 2021 May 13;12(18):4434-4439. doi: 10.1021/acs.jpclett.1c00908. Epub 2021 May 5.
Dual-electron transfer with Mg-ion intercalation outperforms typical alkali metal-ion (Li, Na, K) systems with superior charge storage efficiency while the neutral electrolytes can achieve a working voltage beyond the hydrolysis window of 1.23 V. Hence, aqueous Mg-ion electrolytes are promising for electrochemical energy storage devices to boost the energy density and solve the safety challenges synchronously. However, the Mg-based electrochemical energy storage (EES) devices are generally confined by poor rate performance due to the slow Mg diffusion in the electrode materials. In this paper, we demonstrate that carbon-deficient carbide could function as a promising electrode material in Mg-ion-based EES. An electrode made of such carbide can operate over an extended window up to 2.4 V in 1 M magnesium acetate, showing superior performance of high capacitance (125.2 F/g), high energy density (25.1 Wh/kg), and high power density (3934.8 W/kg). simulation reveals migration energy of Mg being lower than that of Li diffusing from one carbon defect to another in the α-MoC lattice, supporting the experimental results that a symmetric supercapacitor made of α-MoC in an electrolyte based on Mg outperforms electrolytes based on Li.
双电子转移与镁离子嵌入优于典型的碱金属离子（锂、钠、钾）体系，具有更高的电荷存储效率，同时中性电解质可实现超过1.23V水解窗口的工作电压。因此，水性镁离子电解质有望用于电化学储能装置，以同步提高能量密度并解决安全挑战。然而，基于镁的电化学储能（EES）装置通常受限于较差的倍率性能，这是由于镁在电极材料中的扩散缓慢。在本文中，我们证明了缺碳碳化物可作为基于镁离子的EES中有前景的电极材料。由这种碳化物制成的电极在1M醋酸镁中可在高达2.4V的扩展窗口下工作，表现出高电容（125.2F/g）、高能量密度（25.1Wh/kg）和高功率密度（3934.8W/kg）的优异性能。模拟显示，在α-MoC晶格中，镁从一个碳缺陷迁移到另一个碳缺陷的迁移能低于锂，这支持了基于镁的电解质中由α-MoC制成的对称超级电容器优于基于锂的电解质的实验结果。
