Explor­ing How Elec­trolyte Com­po­si­tion Affects The Elec­tric Dou­ble-Lay­er Capacitance 

Dou­ble-lay­er capac­i­tance allows stor­age of elec­tri­cal ener­gy using the elec­tri­cal dou­ble lay­er effect. The phe­nom­e­non occurs between the inter­face of the elec­trode and elec­trolyte as seen, for instance, in super­ca­pac­i­tors. The elec­tric charge stored through dou­ble lay­er capac­i­tance is direct­ly pro­por­tion­al to volt­age. In super­ca­pac­i­tors, the capac­i­tance main­ly depends on elec­trode sur­face and DL dis­tance. How­ev­er, elec­trolyte mix­ture, elec­trode mate­r­i­al and struc­ture, and amount of pseudo­ca­pac­i­tance also affect their capac­i­tance to some extent. Research has time and again indi­cat­ed effects of elec­trolyte com­po­si­tion on EDL and the poten­tial of super­ca­pac­i­tors. Here are a few high­lights to help deter­mine the impor­tance of composition. 

Elec­trolyte Com­po­si­tion for EDL capac­i­tance at Car­bon Electrodes

Mori­ta et al. (2006) inves­ti­gat­ed car­bon elec­trodes of dif­fer­ent sur­face mor­pholo­gies with both organ­ic and poly­mer­ic gel elec­trolytes¹. The group found that both sur­face struc­ture and elec­trolyte com­po­si­tion affect­ed capac­i­tance. For acti­vat­ed car­bon fiber which had a pore struc­ture, high­er capac­i­tance was achieved with poly­mer­ic gel com­pared to capac­i­tance in the solu­tion. In con­trast, capac­i­tance at smooth sur­faced glassy car­bon was high­er in the solu­tion com­pared to the poly­mer­ic gel. Also, the poly­mer­ic com­po­nent offered dif­fer­ent capac­i­tance at the car­bon elec­trode, vary­ing with the sur­face mor­phol­o­gy.

EDL capac­i­tance with TEABF₄ and LiBF₄

Aka­gi et al. demon­strat­ed high­er cur­rent response with Tetraethy­lam­mo­ni­um tetra­flu­o­rob­o­rate (TEABF₄) solu­tion com­pared to Lithi­um tetra­flu­o­rob­o­rate (LiBF₄) solu­tion for glassy car­bon elec­trodes². More­over, the research also indi­cates high­er spe­cif­ic capac­i­tance with ace­toni­trile (AN) elec­trolyte solu­tion com­pared to propy­lene car­bon­ate (PC) sol­vent.

Elec­trolyte Com­po­si­tion for acti­va­tion of alka­­li-treat­ed soft carbon 

Ohta et al. demon­strat­ed the acti­va­tion of alka­­li-treat­ed soft car­bon (ASC) with vary­ing com­po­si­tions of organ­ic elec­trolyte solu­tions³. Anod­ic polar­iza­tion of TEABF₄ solu­tion result­ed in high­er capac­i­tive cur­rents in pos­i­tive poten­tial region. Cathod­ic polar­iza­tion of TEABF₄ solu­tion result­ed in increased cur­rents in cation adsorption/​desorption. Last­ly, sizes of sol­vent mol­e­cules and ions affect­ed acti­va­tion espe­cial­ly at the cath­ode. Larg­er ions and mol­e­cules were more effec­tive while small­er were prefer­able for high­er capac­i­tance.

EDL elec­trolytes at Wat­son International

Renew­able ener­gy is the future. Super­ca­pac­i­tors are pri­mar­i­ly adopt­ed by auto­mo­tive indus­tries for hybrid elec­tric vehi­cles, increas­ing inter­est in elec­trolytes that promise high­er capac­i­tance. We offer a num­ber of super­ca­pac­i­tor elec­trolytes, includ­ing Tetraethy­lam­mo­ni­um tetra­flu­o­rob­o­rate, TEABF₄. Here are select­ed elec­trolytes that you can order right away ! 

• Tetraethyl ammo­ni­um tetra­flu­o­rob­o­rate : http://​wat​son​-int​.com/​t​e​a​b​f​4​-​a​c​n​-​c​a​s​-​4​2​9​-​0​6​-1/
• Tri­ethyl­methy­lam­mo­ni­um tetra­flu­o­rob­o­rate : http://​wat​son​-int​.com/​t​e​m​a​b​f​4​a​c​n​-​c​a​s​-​6​9​4​4​4​-​4​7​-9/
• Succinimidyl-[4-(psoralen-8-yloxy)]-butyrate : http://​wat​son​-int​.com/​s​b​p​b​f​4​-​a​c​n​-​c​a​s​-​1​2​9​2​1​1​-​4​7​-8/

Ref­er­ences

1. Mori­ta, Masayu­ki, et al. ​“Effects of the elec­trolyte com­po­si­tion on the elec­tric dou­ble-lay­er capac­i­tance at car­bon elec­trodes.” Elec­tro­chem­i­cal and sol­id-state let­ters8 (2006): A386-A389.
2. Aka­gi, Shogo, et al. ​“Effects of Elec­trolyte Com­po­si­tion on the Dou­ble Lay­er Capac­i­tance at a Smooth Sur­face Car­bon Elec­trode.” Meet­ing Abstracts. No. 5. The Elec­tro­chem­i­cal Soci­ety, 2008.
3. Ohta, Tomo­ki, et al. ​“Effects of elec­trolyte com­po­si­tion on the elec­tro­chem­i­cal acti­va­tion of alka­­li-treat­ed soft car­bon as an elec­tric dou­ble-lay­er capac­i­tor elec­trode.” Jour­nal of Pow­er Sources198 (2012): 408-415.