Wang Xiaoke, Zhang Xixi, Zhao Gang, Hong Hu, Tang Zijie, Xu Xijin, Li Hongfei, Zhi Chunyi, Han Cuiping
School of Physics and Technology, University of Jinan, Shandong 250022, China.
Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.
ACS Nano. 2022 Apr 26;16(4):6093-6102. doi: 10.1021/acsnano.1c11590. Epub 2022 Mar 21.
Magnesium ion batteries have potential for large-scale energy storage. However, the high charge density of Mg ions establishes a strong intercalation energy barrier in host materials, causing sluggish diffusion kinetics and structural degradation. Here, we report that the kinetic and dissolution issues connected to cathode materials can be resolved simultaneously using a tetraethylene glycol dimethyl ether (TEGDME)-water hybrid electrolyte. The lubricating and shielding effect of water solvent could boost the swift transport of Mg, contributing to a high diffusion coefficient within the sodium vanadate (NaVO·HO) cathode. Meanwhile, the organic TEGDME component can coordinate with water to diminish its activity, thus providing the hybrid electrolyte with a broad electrochemical window of 3.9 V. More importantly, the TEGDME preferentially amassed at the interface, leading to a robust cathode electrolyte interface layer that suppresses the dissolution of vanadium species. Consequently, the NaVO·HO cathode achieved a specific capacity of 351 mAh g at 0.3 A g and a long cycle life of 1000 cycles in this hybrid electrolyte. A mechanism study revealed the reversible interaction of Mg during cycles. This organic water hybrid electrolyte is effective for overcoming the difficulty of multivalent ion storage.
镁离子电池具有大规模储能的潜力。然而，镁离子的高电荷密度在主体材料中建立了强大的嵌入能垒，导致扩散动力学缓慢和结构降解。在此，我们报告使用四甘醇二甲醚（TEGDME）-水混合电解质可以同时解决与阴极材料相关的动力学和溶解问题。水溶剂的润滑和屏蔽作用可以促进镁的快速传输，有助于在钒酸钠（NaVO·HO）阴极内具有高扩散系数。同时，有机TEGDME成分可以与水配位以降低其活性，从而为混合电解质提供3.9 V的宽电化学窗口。更重要的是，TEGDME优先在界面处聚集，形成坚固的阴极电解质界面层，抑制钒物种的溶解。因此，在这种混合电解质中，NaVO·HO阴极在0.3 A g下实现了351 mAh g的比容量和1000次循环的长循环寿命。机理研究揭示了循环过程中镁的可逆相互作用。这种有机水混合电解质对于克服多价离子存储的困难是有效的。
