Electrical Double Layer - Electrical Double Layer Capacitor: Principle And Operation

Elec­tri­cal Dou­ble Lay­er Capac­i­tors, or super­ca­pac­i­tors as they are often called, are high capac­i­ty devices that offer much high­er capac­i­tance than oth­er capac­i­tors. These are in high demand, because of the recent boom in elec­tric vehi­cles. Their struc­ture as well as prin­ci­ple of func­tion is much dif­fer­ent, result­ing in improved per­for­mance. Fur­ther­more, sev­er­al organ­ic and ion­ic elec­trolytes are being inves­ti­gat­ed to increase capac­i­tance. Let’s exam­ine the struc­ture and prin­ci­ple of func­tion of supercapacitors. 

Prin­ci­ple of EDL Capacitor

Alu­minum elec­trolyt­ic capac­i­tors and ceram­ic capac­i­tors have a con­ven­tion­al dielec­tric. Super­ca­pac­i­tors, in con­trast, lack the dielec­tric con­stant as a sol­id or liq­uid elec­trolyte is filled between its two elec­trodes. An elec­tric dou­ble lay­er is formed in these capac­i­tors between the elec­trodes and the elec­trolyte. This works as the dielec­tric. The capac­i­tance is thus pro­por­tion­al to the layer’s sur­face area. Acti­vat­ed car­bon helps achieve high­er capac­i­tance due to the large sur­face area avail­able for elec­trodes.

Mech­a­nism

Charge and dis­charge of the capac­i­tor depends on ion absorp­tion and des­orp­tion mech­a­nism of elec­tri­cal dou­ble lay­er. The capac­i­tor is charged when ions are drawn over the elec­tri­cal dou­ble lay­er by apply­ing volt­age to the elec­trodes. In con­trast, they move away from the lay­er when dis­charg­ing the capac­i­tor. This is how the process of charg­ing and dis­charg­ing takes place in super­ca­pac­i­tors.

Struc­ture of supercapacitors

The capac­i­tor con­sists of fol­low­ing three components : 
  1. Elec­trodes
  2. Elec­trolyte (plus the elec­trolyte salt)
  3. Sep­a­ra­tor
The sep­a­ra­tor pre­vents the two fac­ing elec­trodes from bridg­ing a con­tact with each oth­er. Appli­ca­tion of acti­vat­ed car­bon pow­der to the elec­trodes’ elec­tric­i­ty col­lec­tor helps gen­er­ate an elec­tri­cal dou­ble lay­er on the sur­face, where pow­der con­nects with the elec­trolyte. The acti­vat­ed elec­trodes have a vari­ety of pow­ders with holes on the sur­face. Hence, the lay­er is gen­er­at­ed at points where these pow­ders come in con­tact with the elec­trolyte. As a result, the equiv­a­lent cir­cuit elec­trode resis­tance (Re) as well as the resis­tance caused by ion mov­ing (Rs) rep­re­sents a com­pli­cat­ed equiv­a­lent cir­cuit with var­i­ous resis­tances con­nect­ed in series to capac­i­tors. Of course, the spe­cif­ic details of EDC vary from man­u­fac­tur­er to man­u­fac­tur­er, but its capac­i­tance large­ly depends on the elec­trolyte and elec­trolyte salt being used. As such, sev­er­al car man­u­fac­tur­ers and oth­er com­pa­nies are look­ing to find the most effi­cient com­bi­na­tions. Research indi­cates Tetraethy­lam­mo­ni­um tetra­flu­o­rob­o­rate TEABF4 and oth­er sim­i­lar solu­tions per­form bet­ter than Lithi­um solu­tions. This may pave a way for bat­tery-free cars, using super­ca­pac­i­tors with high­ly effi­cient elec­trolyte com­po­si­tion. If you’re inter­est­ed in research­ing organ­ic and ion­ic elec­trolytes for super­ca­pac­i­tors, you’ve come to the right place. We have a list of solu­tions that you can order today. As fine chem­i­cal dis­trib­u­tors, we main­ly deal with the fol­low­ing elec­trolyte solutions :  Vis­it the asso­ci­at­ed links to find infor­ma­tion about their indi­vid­ual chem­i­cal and phys­i­cal prop­er­ties. Feel free to con­tact us for orders or queries.