Chen Mojing, Li Xiaoqiang, Yan Yujiao, Yang Yanting, Xu Qunjie, Liu Haimei, Xia Yongyao
Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, China.
Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Institute of New Energy, Fudan University, Shanghai 200433, China.
ACS Appl Mater Interfaces. 2022 Jan 12;14(1):1092-1101. doi: 10.1021/acsami.1c20649. Epub 2021 Dec 30.
Prussian blue analogues (PBAs) have been considered as promising cathodes for aqueous zinc-ion batteries because of their open framework for accommodating large ions, tunable valence state, and facile synthesis. Among PBAs, potassium manganese hexacyanoferrate (KMHCF) is favored due to its high working voltage, high specific capacity, and low cost. However, it suffers from severe capacity decay and poor rate capability, which are mainly a result of poor intrinsic conductivity, irreversible phase transition, transition metal dissolution, and structural collapse during charge/discharge cycling. These issues extremely limit its practical application. In order to solve these problems, conductive polypyrrole (PPy) was used to coat KMHCF microcubes to form KMHCF@PPy composites to achieve superior rate capability and prolonged cycle life. With the PPy coating, the KMHCF@PPy composite delivers a discharge capacity of 107.6 mA h g after 100 cycles at 100 mA g, and even at 500 mA g after 500 cycles, 64.2 mA h g still remained. The excellent electrochemical performance can be attributed to the effects from PPy. On the one hand, PPy supplies an effective electronic transmission network for KMHCF to enhance the electronic conductivity. On the other hand, it plays the role of a protective layer to effectively inhibit the dissolution of Mn and the phase transition during the cycling.
普鲁士蓝类似物（PBAs）因其具有容纳大离子的开放框架、可调节的价态以及易于合成的特点，被认为是水系锌离子电池很有前景的正极材料。在PBAs中，六氰合铁酸锰钾（KMHCF）因其高工作电压、高比容量和低成本而受到青睐。然而，它存在严重的容量衰减和倍率性能差的问题，这主要是由于本征电导率差、不可逆相变、过渡金属溶解以及充放电循环过程中的结构坍塌所致。这些问题极大地限制了其实际应用。为了解决这些问题，采用导电聚吡咯（PPy）包覆KMHCF微立方体以形成KMHCF@PPy复合材料，从而实现优异的倍率性能和延长循环寿命。通过PPy包覆，KMHCF@PPy复合材料在100 mA g下循环100次后放电容量为107.6 mA h g，甚至在500 mA g下循环500次后，仍保留64.2 mA h g。优异的电化学性能可归因于PPy的作用。一方面，PPy为KMHCF提供了有效的电子传输网络，以提高电子导电性。另一方面，它起到了保护层的作用，有效地抑制了循环过程中Mn的溶解和相变。
