High-rate performance aqueous-based supercapacitors at −30 °C driven by novel 1D Ni(OH)2 nanorods and a two-solute electrolyte†
Extreme application environments, such as the exploration of space and living in polar regions, require electrochemical energy storage devices to operate well at ultralow temperatures. Aqueous-based supercapacitors (ASCs) have attracted much attention because of their high safety, high-rate performance, and long cycle-life. However, their application in low-temperature environments is also severely limited by the high freezing point of the aqueous-based electrolyte. In this paper, based on the ability of the coordination between Ni2+ and Cl− to restrict the longitudinal growth of Ni(OH)2 along the (0 0 1) crystal plane and the inherent ultralow freezing point of NaCl aqueous solution, cost efficient NaCl was explored for its ability to both regulate the preparation of one-dimensional (1D) Ni(OH)2 nanorods and develop a two-solute electrolyte for ASCs with ultralow-temperature resistance. The 1D Ni(OH)2 nanorods comprised bundles of finer nanorods with a diameter of about 16 nm, which could authentically shorten the transport distance of OH− and electrons, providing enough deformation space for them to interact with each other. Both the three-electrode system and assembled ASCs using this electrode material of 1D Ni(OH)2 nanorods were used to test the specific capacitances, and it was found that this material could give 1.6 times higher values than those of 2D Ni(OH)2 nanosheets at the corresponding scan rates or current densities. Further, the capacitance retention was found to gradually increase from 84.04% for NO0//AC to 96.24% for NO16//AC after 10 000 cycles at 5 A g−1. With the assistance of the two-solute electrolyte, the capacitance retention of NO16//AC at −30 °C was up to 61.1% from 0.5 to 10 A g−1, and 90.21% after 10 000 cycles at 5 A g−1. These results demonstrate not only the potential application of low-cost NaCl in energy storage systems, but also the application of ASCs in ultralow-temperature environments.
- This article is part of the themed collection: Journal of Materials Chemistry A HOT Papers