在水系锌电池中通过孔相双调控实现碳纳米管@硒化镍的快速动力学活化

Enabling kinetically fast activation of carbon nanotube@nickel selenide through pore-phase dual regulation in aqueous zinc battery

金属硫系化合物作为水相锌电池的高性能阴极具有很大的潜力.然而,低可达表面和剧烈的体积膨胀限制了其整体性能和实际应用.为此,采用相工程策略结合空心结构设计,调控OH−在电极表面的吸附/脱附,能显著提高电极的整体电化学性能.本研究首次利用Se@C纳米棒模板,通过原位硒化过程可控合成了一系列碳纳米管(CNT)负载的镍硒化物,包括立方型NiSe_(2)NiSe_(2)/Ni_(0.85)Se复合材料、六方型Ni_(0.85)Se.优化后的NiSe_(2)/Ni_(0.85)Se/CNT复合材料具有比表面积大、孔隙率高、碳骨架空心等优点,具有616Cg^(−1)的高比容量、优良的倍率性能和稳定的循环寿命.通过一系列的非原位表征和DFT计算,深入研究了其内部的法拉第机制.结果表明,所制备的Ni//Zn电池在3485 W kg^(−1)时具有311.4 W h kg^(−1)的高能量密度和较长的循环寿命.本研究为硒化镍基电极材料的设计提供了一种巧妙的策略,且深入研究了其在碱性锌电池中的法拉第机理.

Metal chalcogenide compounds can be used as high-performance cathodes for aqueous Zn batteries.However,the low accessible surfaces and violent volumetric expansion limit their properties and applications.To address these,phase-engineering strategies coupled with a hollow structure were applied to regulate the adsorption/desorption of OH−on the electrode surface and enhance the electrochemical performance.In this study,using a Se@C nanorod template,a series of carbon nanotube(CNT)-supported nickel selenides,including cubic NiSe_(2),NiSe_(2)/Ni_(0.85)Se composites,and hexagonal Ni_(0.85)Se,were synthesized through an in situ selenylation process for the first time.Due to the large specific surface,high porosity,and hollow carbon skeleton,the optimized NiSe_(2)/Ni_(0.85)Se/CNT has a high specific capacity of 616 Cg^(−1),excellent rate capability,and stable cycling performance.In addition,its inside Faradic mechanism was investigated using a series of ex situ characterizations and density functional theory calculations.Thus,the fabricated Ni//Zn battery presents a high energy density of 311.4 W h kg^(−1) at 3485 W kg^(−1) and long cycling life.This study offers an ingenious strategy for designing nickel selenide electrodes and deeper perception for its Faradic mechanism in alkaline Zn battery.