Surface Wettability Effect on Energy Density and Power Density of Supercapacitors

Abstract

Many attempts have been made to improve the energy density of supercapacitors toward their large-scale applications in storing renewable energy. Herein, the surface wettability effect is unraveled with the combination of static and dynamic density functional theories through which the energy densities and power densities of electrochemical supercapacitors are analyzed with different sets of pore sizes, surface voltages, and bulk ion concentrations. We demonstrate that tuning the surface wettability of electrodes may improve the energy density but simultaneously reduce the power density, and an optimal energy density with a relatively small cost of power density can be achieved by adopting highly confined pores. In addition, increasing ion bulk concentration and/or surface voltage can enhance both the energy density and power density. This work provides a complementary dynamic insight into the surface wettability effect on the performance of supercapacitors.

Anion Intercalation into Graphite Drives Surface Wetting

“…Even their simple macroscopic observation can provide significant molecular insights into the properties of interfaces as well as those of the adjoining bulk phases. − A number of diverse technologies, from electrochemical energy conversion, storage , and capacitive deionization (CDI) , to variable optics, − displays, , and lab-on-a-chip systems, , are driven by wetting processes which occur under the application of an external electric field, a phenomenon referred to as electrowetting . Controlling wettability under these conditions is of paramount importance for product design, since any variations in wettability can have significant implications for the operation of the devices (such as lack of adhesion, , hysteresis, − and loss of electrochemical activity − ), resulting in performance decrease and/or failure.…”

Electrolyte-philicity of electrode materials

“…Thus, the effect of electrolyte-philicity on the energy storage properties of electrode materials is revealed by static and dynamic density functional theory. 69 Firstly, the model of pore in electrode materials is assumed, as shown in Fig. 4e.…”

“…The high density causes close spatial packing of the solvent molecule, hindering the electrolyte ions from moving to the pore wall. 69 Fortunately, the ion-philicity of electrolyte-philic electrode materials could compensate for the drawback. 3.2.2.…”

Electrolyte‐Wettability Issues and Challenges of Electrode Materials in Electrochemical Energy Storage, Energy Conversion, and Beyond

“…Therefore, the effect of electrolyte‐wettability on the supercapacitive performance of carbon electrode materials is revealed by static and dynamic density functional theory. [ 100 ] First, the model of pore in carbon electrode materials is assumed as shown in Figure a. To describe the charging process, the surface charge density, Q s could be obtained by applying the charge neutrality condition when [ 101 ] $$$$\begin{equation}{Q}_{\rm{s}}\left( t \right) = - \int_{0}^{{H/2}}{{\sum\nolimits_i {e{Z}_i{\rho }_i} }}\left( {z,t} \right){\rm{d}}z\end{equation}$$$$…”

“…c) Capacitance against the surface wetting parameter under H/𝜎 = 2 and H/𝜎 = 5. Reproduced with permission [100]. Copyright 2022, American Chemical Society.…”