Zhang Luomeng, Xia Hui, Liu Shaobo, Zhou Yishan, Zhao Yuefeng, Xie Wenke
School of Physics and Electronics, Central South University, Changsha, 410083, China.
Collaborative Innovation Center of Light Manipulations and Applications, Shangdong Normal University, Jinan, 250358, China.
Nanoscale Res Lett. 2021 May 12;16(1):83. doi: 10.1186/s11671-021-03543-w.
Layered double hydroxides as typical supercapacitor electrode materials can exhibit superior energy storage performance if their structures are well regulated. In this work, a simple one-step hydrothermal method is used to prepare diverse nickel-cobalt layered double hydroxides (NiCo-LDHs), in which the different contents of urea are used to regulate the different nanostructures of NiCo-LDHs. The results show that the decrease in urea content can effectively improve the dispersibility, adjust the thickness and optimize the internal pore structures of NiCo-LDHs, thereby enhancing their capacitance performance. When the content of urea is reduced from 0.03 to 0.0075 g under a fixed precursor materials mass ratio of nickel (0.06 g) to cobalt (0.02 g) of 3:1, the prepared sample NiCo-LDH-1 exhibits the thickness of 1.62 nm, and the clear thin-layer nanosheet structures and a large number of surface pores are formed, which is beneficial to the transmission of ions into the electrode material. After being prepared as a supercapacitor electrode, the NiCo-LDH-1 displays an ultra-high specific capacitance of 3982.5 F g under the current density of 1 A g and high capacitance retention above 93.6% after 1000 cycles of charging and discharging at a high current density of 10 A g. The excellent electrochemical performance of NiCo-LDH-1 is proved by assembling two-electrode asymmetric supercapacitor with carbon spheres, displaying the specific capacitance of 95 F g at 1 A g with the capacitance retention of 78% over 1000 cycles. The current work offers a facile way to control the nanostructure of NiCo-LDHs, confirms the important affection of urea on enhancing capacitive performance for supercapacitor electrode and provides the high possibility for the development of high-performance supercapacitors.
层状双氢氧化物作为典型的超级电容器电极材料，如果其结构得到良好调控，就能展现出优异的储能性能。在这项工作中，采用一种简单的一步水热法制备了多种镍钴层状双氢氧化物（NiCo-LDHs），其中使用不同含量的尿素来调控NiCo-LDHs的不同纳米结构。结果表明，尿素含量的降低能有效提高NiCo-LDHs的分散性，调整其厚度并优化内部孔隙结构，从而增强其电容性能。当在镍（0.06 g）与钴（0.02 g）的固定前驱体材料质量比为3:1的情况下，尿素含量从0.03 g降至0.0075 g时，制备的样品NiCo-LDH-1的厚度为1.62 nm，形成了清晰的薄层纳米片结构和大量表面孔隙，这有利于离子传输进入电极材料。制备成超级电容器电极后，NiCo-LDH-1在1 A g的电流密度下显示出3982.5 F g的超高比电容，在10 A g的高电流密度下经过1000次充放电循环后，电容保持率高于93.6%。通过将NiCo-LDH-1与碳球组装成两电极不对称超级电容器，证明了其优异的电化学性能，在1 A g时比电容为95 F g，在1000次循环后电容保持率为78%。当前的工作提供了一种简便的方法来控制NiCo-LDHs的纳米结构，证实了尿素对增强超级电容器电极电容性能的重要影响，并为高性能超级电容器的开发提供了很大可能性。
