Relation between Charging Times and Storage Properties of Nanoporous Supercapacitors.

Timur Aslyamov,Konstantin Sinkov,Iskander Akhatov

doi:10.3390/nano12040587

Timur Aslyamov, Konstantin Sinkov + Show 1 more

Open Access

https://doi.org/10.3390/nano12040587

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Abstract

An optimal combination of power and energy characteristics is beneficial for the further progress of supercapacitors-based technologies. We develop a nanoscale dynamic electrolyte model, which describes both static capacitance and the time-dependent charging process, including the initial square-root dependency and two subsequent exponential trends. The observed charging time corresponds to one of the relaxation times of the exponential regimes and significantly depends on the pore size. Additionally, we find analytical expressions providing relations of the time scales to the electrode’s parameters, applied potential, and the final state of the confined electrolyte. Our numerical results for the charging regimes agree with published computer simulations, and estimations of the charging times coincide with the experimental values.

Highlights

Among all modern energy sources, supercapacitors demonstrate an extraordinary power density and an extremely long cycling life [1]
Our numerical results for the charging regimes agree with published computer simulations, and estimations of the charging times coincide with the experimental values
The three consecutive dynamic regimes predicted in our work describe the results of molecular dynamics simulations published in refs. [25–27]

Summary

Introduction

Among all modern energy sources, supercapacitors demonstrate an extraordinary power density and an extremely long cycling life [1]. Since we use an accurate thermodynamic potential, our model accounts for the electric and packaging properties of finite-sized ions within the nanopores It is an advantage over recently published dynamic models [18,19], and allows us to relate charging times to the given characteristics of nanopore supercapacitors. It allows us to account for the realistic behavior of the electrolytes in confinement: alteration of over-screening/crowding interfaces [43]; the capacity oscillations in narrow nanopores [6] Such subnanoscale properties are beyond the scope of the PNP equations [24], linear TLM models [23] or their very recent modifications [17,19]. Since the derived transport equation correctly describes the ions-packing properties and the electrostatic fluctuations, we can extend the theoretical study to the ultra-narrow pores comparable to molecular size

Results

Ca L 2

Conclusions