| Electrical Energy Storage (EES) hold the key in harvesting intermittent renewable energy sources and powering long-range electrical vehicles. Compared with other EES devices (e.g. batteries), electrochemical capacitors (ECs), also called supercapacitors, gain growing attentions mainly due to their high power density and extraordinary-long service life. ECs store electrical energy via ion electrosorption on electrolyte-electrode interface forming electrical double layers (EDLs). The current surge in interests in ECs is driven by the recent breakthroughs in novel electrode materials (e.g. nanoporous carbon) and electrolyte materials (e.g. room temperature ionic liquids (RTILs)).
In this lecture, our recent theoretical and modeling works are presented on equilibrium and dynamics of charge storage in nanopores filled with RTILs. Recent experiments have shown capacitance of subnanometer pores increase anomalously as pore size decreases. Molecular dynamics (MD) simulations not only revealed anomalous capacitance increase but also predicted a reduction of capacitance at large pore sizes. Apart from pore size, the effect of operation parameter, applied voltage, is also examined. MD simulations show charge storage in nanopores follows a distinct voltage-dependent behavior. In lower voltage, charge storage is achieved by ion swapping; as voltage increases, further charge storage is achieved by expelling co-ions, along with a capacitance increase; at even higher voltages, charge storage is achieved by cation-ions insertion, accompanied by a reduction of capacitance. The molecular origins of these phenomena are elucidated by a new theoretical framework specifically developed for charge storage in nanopores using RTILs.
The use of narrow pores and high viscosity RTILs tends to lower power density of ECs. To help address this issue through material optimization, herein, we unravel mechanism of charging subnanometer pores with RTILs using MD simulations, navigated by a phenomenological model. We show that charging of ionophilic pores is a diffusive process, often accompanied by overfilling followed by de-filling. In sharp contrast to conventional expectation, charging is fast because ion diffusion during charging is one order magnitude larger than in bulk, and charging itself is accelerated by the onset of collective modes. Overall, the fundamental insights gained in our studies help rationalize design and optimizations of electrode and electrolytes materials to realize their full potentials.
吴鹏，于2009年获华中科技大学学士学位；2014年获克莱姆森大学博士学位。随后加入节能材料生产商美国CentralPlas公司任生产顾问，从事生产改进工作。近年来在有关新能源新型储能装置方面进行了深入研究，取得了一系列成果。其中，纳米多孔电极储能机理的研究，被英国帝国理工大学的Prof. Kornyshev所著的Chem. Rev.中用专节进行了总结；纳米多孔电极充电过程的研究发表在Nature Mater.上，目前已被他人引用37次，被SCI评为高引论文。
近年来，已发表SCI期刊论文4篇（一作3篇，平均影响因子过14），被Chem. Rev.、Nature Mater.、Energ. Environ. Sci., JACS、ACS Nano等40多种SCI期刊引用180次；单篇一作论文，目前已被他人引用79次；担任10多种国际期刊（J. Phys. Chem. C，Appl. Phys. Lett.，J. Phys. D: Appl. Phys.，J. Mol. Liq.，Colloids Surface A，Fluid Phase Equilibr.，Ionics）审稿人。
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