Abstract:

Asymmetric supercapacitors(ASCs) have the merits of rapid charge and discharge,high power density,and long?term cyclic stability.The properties of electrode materials determine the performance of ASCs.Cation substitution is an effective method to tune the structure and properties of electrode materials and optimize energy storage performance accordingly.This paper prepared MCo₂S₄(M=Co,Ni,or Cu) nanosheet arrays on the surface of a nickel foam substrate.For this purpose,it controlled the cationic components of the spinel sulfide and employed a hydrothermal method.Due to the differences in the radius and electronegativity of metal irons,the lattice structure of Co₃S₄ underwent strain when Ni²⁺ or Cu²⁺ ions were introduced into Co₃S₄ to obtain NiCo₂S₄ or CuCo₂S₄.The result was reinforced reactivity of the metal sites.The charge transfer and ion diffusion resistances of NiCo₂S₄ are respectively 48.6% and 28.7% lower than those of Co₃S₄,indicating favorable electrochemical properties achieved.The specific capacity of NiCo₂S₄ is 1 128.8 F/g under a current density of 1 A/g.The capacity retention is 59.8% under a current density of 10 A/g.The retention of the initial specific capacity is 60.2% after 8 000 cycles.

Key words: Metal sulfide, Cation substitution, Charge transfer, Ion diffusion, Supercapacitor

摘要：

非对称超级电容器具有快速充放电、高功率密度和长期循环稳定等特点，电极材料的性质对其性能起到决定性作用，利用阳离子取代是调节电极材料结构、性质和优化储能性能的有效方法。通过控制尖晶石型硫化物中的阳离子组成，采用水热法在泡沫镍基底表面制备了MCo₂S₄（M代表Co、Ni或Cu）纳米片阵列。由于金属离子半径和电负性差异，向Co₃S₄中引入Ni²⁺或Cu²⁺形成NiCo₂S₄或CuCo₂S₄，会诱导其晶格结构发生应变，从而提升金属位点的反应活性。相比于Co₃S₄，NiCo₂S₄的电荷转移电阻和离子扩散电阻分别下降了48.6%和28.7%，获得了良好的电化学性能。当电流密度为1 A/g时，NiCo₂S₄的比容量为1 128.8 F/g；当电流密度为10 A/g时，比容量保持率为59.8%；经过8 000次循环后仍保持60.2%的初始比容量。

关键词: 金属硫化物, 阳离子取代, 电荷转移, 离子扩散, 超级电容器