Study On Ion Transport In Nanochannels Of Electric Double Layer Capacitors

Due to the over-reliance on traditional fossil fuels,the global climate has deteriorated,and the development of sustainable renewable clean energy has become an inevitable trend in global energy security.Building a low-carbon smart city in harmony between man and nature has become a national goal.With the advent of the5G era,the demand for fixed or mobile high-power devices in the development of Industry 4.0 has increased.These all urgently require the rapid development of electric double layer capacitors.At present,due to low energy density,electric double layer capacitors cannot be widely used.The quantitative description of the ion transport behavior in the solid-state nanopore can further provide theoretical support for the research on reducing the conductance,increasing the working voltage and increasing the specific capacitance in the parameter design of electric double layer capacitors.This helps promote the extensive industrialization of high-performance double-layer capacitors.The study of ion transport behavior in nanopores can not only promote the rapid development of the energy storage mechanism of electric double layer capacitors,but also provide references for various applications of nanopores（such as seawater desalination,biomolecule detection,pollutant purification,etc.）.Therefore,this paper proposes"study of ion transport in nanochannels of electric double layer capacitors".The mechanism of ion storage and transport in nanopores included in the principle of energy storage has been studied.The transport of ions driven by the electric field force is focused on.Relying on theoretical predictions,numerical simulations,molecular dynamics simulations and experiments,the migration characteristics of ions in nanopores with overlapping electric double layers have been investigated.Establish a theoretical model suitable for ion mobility characteristics.A quantitative description model suitable for ion mobility characteristics is proposed.A quantitative description model suitable for ion mobility characteristics is proposed.Ion transport characteristics are discussed in single-digit nanopores.It is hoped to provide a basis for parameter modulation in the design of electric double layer capacitors.Research on the theoretical model of ion conductance.Based on the interface electrostatic and dynamic effects of ion transport,ion conductance can be subdivided into access conductance,surface charge conductance,nanopore conductance,surface potential leakage conductance and electroosmotic conductance.The conductance can be unified into a model by using the dimensionless factor and the leakage coefficient.The power law relationship between conductance and concentration is described by a model,G∝n₀^α,to quantitatively describe the transport behavior of ions in the nanopore.The model shows that the ion conductance is dominated by the surface charge in the low-concentration area,while the high-concentration area exhibits bulk behavior.At the same time,the greater the concentration and the surface charge value,the stronger the electroosmotic conductance effect.At the same time,simulation and experimental results are used to verify the theoretical model of ion conductance,and the limitations of the model in terms of concentration and ion mobility are discussed.The effect of ion conductance in sub-nanopore on ion transport.Using experimental and molecular dynamics methods,it is discussed that the concentration of nanopores that maintain neutrality is not suitable for conducting research on sub-nanopores.Relying on the Donnan equilibrium relationship and Poisson-Boltzmann to estimate the average concentration of nanopores,it is used to study the conductance of nanopores.The results show that under the action of surface charge,the average ion concentration inside the nanopore is much higher than the bulk value.In the sub-nanopore,100m M is the transition concentration between surface charge and bulk behavior control.In addition,through the investigation of the conductance,it is found that the entrance conductance does not hinder the transport of ions.The nanopore conductance is still the largest contributor to the conductance in the hole,and the surface potential leakage conductance is far greater than the surface conductance.But when the bulk concentration is higher than 10 m M,the electroosmotic conductance starts to affect the ion conductance.When the bulk concentration is higher than 100m M,the ion conductance has a linear relationship with the bulk concentration.At the same time,sub-nanopores also show strong selectivity to Na⁺and strong repellency to Cl^-.Ion migration properties of nanopores in solid membranes.The detected current is used to study the conductivity below 10nm.The evolution process of ion conductivity with the change of the pore size was investigated.The results show that,on the one hand,the pore size increases,the leakage coefficientαvalue increases,the larger theαvalue,the greater the surface potential leakage value,and the ion conductance is close to the bulk value;on the other hand,the surface potential leakage increases with the increase of bulk concentration.However,after exceeding 100m M,it drops rapidly,and its value may show a negative value.The smaller the pore diameter of the nanopore,the higher the ion concentration,and the better the charge storage efficiency of the electric double layer capacitor.In the low concentration area,due to the Wien effect,the ion mobility is much higher than the bulk value.As the bulk concentration increases,the ion mobility drops rapidly,even lower than the bulk value.Based on factors such as surface charge and concentration,the paper establishes a model for estimation Ion mobility of 1:1 electrolyte solution.The coupling of water and ions in nanopore.Due to the polarity of water molecules,electrostatic effect makes ion migration coupled with water molecules.Ion hydration radius affect the axial distribution of ions in nanopore,and it also affects the flux of water.In the investigation of Na⁺,Ca²⁺and La³⁺,it is found that the coupling effect of ions and water promotes each other.In the experiment,after conducting conductance research on salts,it was found that the difference in ion hydration radius will lead to different relaxation times,which leads to different conductance.In the investigation of the effect of temperature on ion migration,it is found that temperature is a related term of ion conductance,and as the concentration increases,the influence of temperature on ion conductance is greater.