Aqueous Electrolyte, Use of the Electrolyte and Hybrid Supercapacitor Containing the Electrolyte

Abstract

An aqueous electrolyte for a capacitor contains at least one transition metal complex. An aqueous electrolyte containing at least one transition metal complex can be used in a supercapacitor, in a pseudocapacitor, or in a hybrid supercapacitor. A hybrid supercapacitor contains an aqueous electrolyte, which contains at least one transition metal complex.

Claims

1. An aqueous electrolyte for a capacitor, the aqueous electrolyte comprising: at least one transition metal complex.

2. The aqueous electrolyte according to claim 1, wherein the at least one transition metal complex contains at least one transition metal selected from the group consisting of cobalt, chromium, iron, copper and titanium.

3. The aqueous electrolyte according to claim 1, wherein the at least one transition metal complex contains at least one ligand selected from the group consisting of ammonia, cyanide, perchlorate, thiocyanate and ethylenediaminetetraacetate.

4. The aqueous electrolyte according to claim 3, wherein the at least one transition metal complex has the formula ML.sub.x, where M is the transition metal and L is a ligand selected from the group and x has a value of 2, 4 or 6.

5. The aqueous electrolyte according to claim 1, wherein the concentration of the at least one transition metal complex in the aqueous electrolyte is in a range from 0.01 mol/l to 0.5 mol/l.

6. The aqueous electrolyte according to claim 1, further comprising: sulfuric acid and/or at least one alkali metal salt and/or at least one alkaline earth metal salt.

7. Use of an aqueous electrolyte in a supercapacitor, in a pseudocapacitor, or in a hybrid supercapacitor, wherein the aqueous electrolyte contains at least one transition metal complex.

8. A hybrid supercapacitor, comprising: an aqueous electrolyte containing at least one transition metal complex.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A working example of the disclosure is shown in the FIGURE and is described in more detail in the following description.

[0013] The FIGURE schematically shows the structure of a symmetric hybrid supercapacitor as per a number of working examples of the disclosure.

DETAILED DESCRIPTION

[0014] A symmetric hybrid supercapacitor 1 according to various working examples of the disclosure has the structure shown in the FIGURE. A cathode 2 has been applied to a first collector 3. An anode 4 has been applied to a second collector 5. An electrolyte 6 has been introduced between the cathode 2 and the anode 4. A separator 7 separates the cathode 2 from the anode 4. Embedding of Li.sup.+ ions into the cathode 2 and into the anode 4 is shown schematically in the FIGURE. Here, the FIGURE shows activated carbon as capacitive electrode material on the surface of which, during charging, negative charge carriers of the electrolyte 6 accumulate at the cathode 2 and on the surface of which positive charge carriers of the electrolyte 6 accumulate at the anode 4. Furthermore, it is shown in four enlargements how the lithium ion cathode material of the cathode 2, in the present case LiMn.sub.2O.sub.4, deintercalates Li.sup.+ ions and the lithium ion anode material of the anode 4, in the present case Li.sub.4Ti.sub.5O.sub.12, intercalates Li.sup.+ ions.

[0015] The electrolyte 6 is a 1M solution of LiSO.sub.4 in water which additionally contains a transition metal complex in a concentration of 0.1M.

[0016] In a first working example of the disclosure, the transition metal complex is hexamminecobalt(III). During charging and discharging of the hybrid supercapacitor 1, redox reactions according to the formula 1 proceed in the electrolyte:

[Co(NH.sub.3).sub.6].sup.3+[Co(NH.sub.3).sub.6].sup.4++e.sup.−[Co(NH.sub.3).sub.6].sup.6++3e.sup.−   (formula 1)

[0017] In a second working example of the disclosure, the transition metal complex is a hexacyanocobaltate(III). During charging and discharging of the hybrid supercapacitor 1, redox reactions according to formula 2 proceed in the electrolyte:

[Co(CN).sub.6].sup.3−[Co(CN).sub.6].sup.2−+e.sup.−   (formula 2)

[0018] In a third working example of the disclosure, the transition metal complex is hexacyanochromate(III). During charging and discharging of the hybrid supercapacitor 1, redox reactions according to formula 3 proceed in the electrolyte:

[Cr(CN).sub.6].sup.3−[Cr(CN).sub.6]+3e.sup.−   (formula 3)

[0019] In a fourth working example of the disclosure, the transition metal complex is hexathiocyanatoferrate(III). During charging and discharging of the hybrid supercapacitor 1, redox reactions according to formula 4 proceed with ligand exchange in the alkaline electrolyte:

[Fe(SCN).sub.6].sup.3−+OH.sup.−+e.sup.−[Fe(SCN).sub.5OH].sup.4−+SCN.sup.−   (formula 4)

[0020] In a fifth working example of the disclosure, the transition metal complex is triperchloratoiron(III). During charging and discharging of the hybrid supercapacitor 1, redox reactions according to formula 5 proceed in the electrolyte:

[Fe(ClO.sub.4).sub.3]+e.sup.−[Fe(ClO.sub.4).sub.3].sup.−   (formula 5)

[0021] In a sixth working example of the disclosure, the transition metal complex is perchloratocopper(II). During charging and discharging of the hybrid supercapacitor 1, redox reactions according to formula 6 proceed in the electrolyte:

[Cu(ClO.sub.4)].sup.++e.sup.−[Cu(ClO.sub.4)]   (formula 6)

[0022] These redox reactions contribute, in addition to the faradaic and capacitive activity of the cathode 2 and of the anode 4, to electric charge storage in the hybrid supercapacitor 1.