Based on the advantages of fast charge-discharge, good cycle stability and wide operating voltage window, the electric double layer capacitor based on porous activated carbon material and ionic liquid electrolyte is a promising electrochemical energy storage device.Study on EDLC in ionic liquids The mechanism of energy storage, especially the mechanism of the influence of the intrinsic structure of anion and cation on the capacitance of porous activated carbon, reveals the mechanism of energy storage from the microscopic level, which has important guiding significance for the proper choice of ionic liquid and reasonable construction of high performance EDLC .
Recently, Yan Xingbin, a researcher at the Clean Energy Chemistry and Materials Laboratory of Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, made important progress in researching EDLC energy storage mechanism in ionic liquids. The researchers prepared four kinds of ionic liquids grafted with nano-silica, The purpose of analyzing the anions and cations is achieved by using only one ion of ionic liquid to freely enter and exit the pores of the activated carbon during charging and discharging.The results can provide a new strategy for studying the energy storage behavior of anion and cation in ionic liquids in EDLC .
Silica grafted ionic liquids are structurally characterized by an ion (cationic BMIM +, NBu 4+Or anion NTf 2-, PF 6-) Is free; while the counterbalanced charge with a countercharge ions: trifluoromethanesulfonimide anion (NTf -) And methylimidazolium cation (MIM +) Was covalently attached to the size of 7nm silica nanoparticles selected most of the pores of the selected activated carbon material pore size of less than 4nm, so that the ions connected to the silica is blocked outside the activated carbon channel , While the free ions to be tested (cationic BMIM + , NBu 4+Or anion NTf 2-, PF 6-) Pass through the wellbore.On this basis, a simple electrochemical test to achieve the quantitative analysis of free access to the ion channel, that is, the use of the size of the cyclic voltammetry current direct reaction ion contribution capacity.
Based on the above method, the research team found that the commercially available activated carbon YP-50F electrode can be characterized cationic BMIM +, NBu 4+And anion NTf 2-, PF 6-The respective contributed capacity, and the specific voltage window for each ion contribution capacity.The researchers further characterized the activity of activated carbon YP-50F in ionic liquids (BMIM-NTf 2) Energy storage mechanism, combined with BMIM +And NTf 2-Their electrochemical properties, a deeper explanation of the energy storage mechanism.
Relevant research results published in "Nature - Communications." This research has been funded by the National Natural Science Foundation of China and the Lanzhou Institute of Chemistry 's "Thirteen Five" key cultivation project.
Figure 1 Schematic diagram of a: Silica grafted ions and free ions structure diagram; b: Silica transmission electron microscopy; c: Activated carbon pore size distribution diagram; d: Activated carbon in three different electrolytes in the energy storage diagram , From top to bottom followed by anions free, fixed cations, free cations, fixed anions, free anions and cations
Figure 2. Cyclic voltammetric curves of activated carbon YP-50F electrode in four different electrolytes. A-d followed by SiO 2-IL-BMIM, SiO 2-IL-NTf 2, SiO 2-IL-NBu 4, SiO 2-IL-PF6
Figure 3. Combined characterization of the individual properties of the anion and cation as well as a detailed study of the energy storage mechanism by quartz crystal microbalance experiments
