Bi Songshan, Wang Shuai, Yue Fang, Tie Zhiwei, Niu Zhiqiang
Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, Tianjin, 300071, P. R. China.
Nat Commun. 2021 Nov 30;12(1):6991. doi: 10.1038/s41467-021-27313-5.
Aqueous rechargeable metal batteries are intrinsically safe due to the utilization of low-cost and non-flammable water-based electrolyte solutions. However, the discharge voltages of these electrochemical energy storage systems are often limited, thus, resulting in unsatisfactory energy density. Therefore, it is of paramount importance to investigate alternative aqueous metal battery systems to improve the discharge voltage. Herein, we report reversible manganese-ion intercalation chemistry in an aqueous electrolyte solution, where inorganic and organic compounds act as positive electrode active materials for Mn storage when coupled with a Mn/carbon composite negative electrode. In one case, the layered MnVO·nHO inorganic cathode demonstrates fast and reversible Mn insertion/extraction due to the large lattice spacing, thus, enabling adequate power performances and stable cycling behavior. In the other case, the tetrachloro-1,4-benzoquinone organic cathode molecules undergo enolization during charge/discharge processes, thus, contributing to achieving a stable cell discharge plateau at about 1.37 V. Interestingly, the low redox potential of the Mn/Mn redox couple vs. standard hydrogen electrode (i.e., -1.19 V) enables the production of aqueous manganese metal cells with operational voltages higher than their zinc metal counterparts.
水系可充电金属电池由于使用低成本且不易燃的水基电解质溶液而本质安全。然而，这些电化学储能系统的放电电压往往受到限制，因此能量密度不尽人意。所以，研究替代的水系金属电池系统以提高放电电压至关重要。在此，我们报道了在水基电解质溶液中的可逆锰离子嵌入化学，其中无机和有机化合物与锰/碳复合负极耦合时作为储存锰的正极活性材料。在一种情况下，层状的MnVO·nH₂O无机正极由于晶格间距大而表现出快速且可逆的锰嵌入/脱出，从而实现了足够的功率性能和稳定的循环行为。在另一种情况下，四氯-1,4-苯醌有机正极分子在充放电过程中发生烯醇化，从而有助于在约1.37 V实现稳定的电池放电平台。有趣的是，锰/锰²⁺氧化还原对相对于标准氢电极的低氧化还原电位（即 -1.19 V）使得能够生产工作电压高于锌金属电池的水系锰金属电池。
