Title: Electro-chemical cells
Patent Number: 4377623
Issue Date: 19830322

The invention relates to an electro-chemical cell having an electrolyte comprising water, a halogen other than fluorine, a halide other than fluoride, which is not oxidized by the halogen as a soluble salt, and a stable, saturated, organic nitrile or dinitrile containing from 2 to 5 carbon atoms or a mixture thereof, said electrolyte being composed such as to exist in two phases, a first phase being halogen and nitrile-rich and a second phase being water-rich and containing halide salt, the cell having an inert electrode in the halogen and nitrile-rich phase and an electrode, containing or contacting halogen oxidizable material, in the water-rich phase. The electro-chemical cell of the invention is particularly applicable to systems containing zinc as the halogen oxidizable material.

Application Date:     1981 07 15
Inventor Name     Inventor Country     Inventor State     Inventor City
Parker; Alan J.                         AU         South Perth
Singh; Pritam                           AU         Murdoch
Avraamides; James                  AU         Bull Creek
Assignee Name     Assignee Country     Assignee State     Assignee City
Anumin Pty. Ltd.                       AU         Murdoch

IPC Code:                          H01M 1204
Current US Classification:     429 15, 429105
Application Serial Number:   2836033
Application Type:                1 (Utility)
Field Of Search Nat:            429/101;105;15
Inventor Street:                  ---, ---,
Inventor Zip Code:              ---, ---,
Attorney or Agent:              Hinds; William R.
Primary Examiner:              Walton; Donald L.
Referenced By:                  3879221, 3887400, 4038459, 4105829, 4162351

surechem.org - Info was taken from this page. Useful if you thinking about how to make Zn(Br)2 battery.

google.com/patents - Patent
4377623 in PDF format. Containing tables with results.

premiumpower.com (PDF) - 'Zinc-Flow 45' unit
based on Zn(Br)2 technology (45 kW, 30 years operable life). Made by 'Premium Power Corporation' (North Reading, MA, USA). Company in business since 2002.

redflow.com.au (WEB) - 'RedFlow R510' unit
based on the same technology (5 kWh, 10 kW (total), 2000 charge/discharge cycles).
And a useful video on YT, that shows how
'RedFlow R510' system works (05.03.2012).

Detailed Description:    

This example illustrates an embodiment of the present invention with both solutions stationary in the horizontal mode. 0.1 mole of bromine and 0.2 mole each of zinc bromide and NaCl was dissolved in a mixture of 100 ml water and 100 ml cyanoethane (* IUPAC Name: propanenitrile). Two layers of approximately equal volume appeared. The upper layer was red, the lower pale yellow. A porous carbon felt electrode, larger than the zinc electrode, and partly in the organic phase and partly in the aqueous phase, and a zinc electrode separated by 1 cm were placed in the upper red and lower yellow solutions respectively and connected to current and voltage measuring devices. Both solutions were still and at 22° C. The cell had an open circuit voltage of 1.76 V and a short circuit current of 210 mA cm-2 of zinc. While charging for 6 hours at 20 mA cm-2 the voltage was 1.96 V and zinc was plated on the zinc electrode. Some dentrites were formed. A few gas bubbles were evolved, during charging at the zinc electrode. A little loose particulate zinc rested on the zinc electrode after 6 hours charging because of the horizontal configuration. The cell was discharged at 20 mA cm-2 at 1.50 V over 6 hours. The coulombic efficiency over the discharge-charge cycle was 77% (i.e. 90% on charge, 86% on discharge).

In an embodiment similar to that of Example I, the upper nitrile-rich layer flowed slowly past a glassy carbon electrode of the same size as the zinc, but the lower water-rich layer remained still. The voltage on charging at 10 mA cm-2 of zinc was 2.00 V and on discharging at 20 mA cm-2 was 1.55 V.

A zinc chlorine cell was discharged in which the electrolyte was saturated chlorine under a slight positive pressure, 1 M KCl and 1 M zinc chloride in equal volumes of water and cyanoethane. Electrodes were zinc in the lower phase and carbon in the upper and there was no separator. The open circuit voltage was 2.2 volt and the short circuit current was 200 mA cm-2 of zinc. In a separate experiment, the distribution coefficient for chlorine between cyanoethane and water containing 2 M NaCl, 1 M ZnCl2 and saturated chlorine at 1 atmosphere was found to be 50. The concentration of chlorine in the organic phase was 0.5 M.

A zinc-halogen battery was operated in which the electrolyte was 1 M iodine monochloride, 4 M NaCl, 4 M NH4 Cl and 1 M zinc chloride in equal volumes of water and cyanoethane. Electrodes were zinc and carbon at 0.75 cm separation. The open circuit voltage was 1.78 volt and the short circuit current on discharge was ca 230 mA cm-2 of zinc at 0.77 volt, rising to 250 mA cm-2 at 0.88 volt after 5 minutes.

A zinc-iodine cell was operated in a similar fashion to the Zn/Br2 battery with solutions containing cyanoethane, water, 0.5 M iodine, 1.0 M zinc iodide and saturated potassium iodide. The electrodes were zinc and platinum. The open circuit voltage was 1.13 volt and the battery delivered 48 mA cm-2 at 0.3 volt when short circuited. Coulombic charging efficiency was 71% at 25 mA cm-2 at a voltage of 1.64 V.

A battery was operated in which the two phase electrolyte was equilibrated 1 M bromine, 1 M zinc bromide, and 1 M NaCl in equal volumes of water and cyanoethane. A carbon felt electrode of geometrical area 10 cm2 was in the upper bromine and nitrile-rich layer and the other electrode was platinum gauze of about 15 cm2 effective area in a gently stirred suspension of zinc powder in the lower water-rich phase. The open circuit voltage was 1.70 V, the short circuit current was 1050 mA and when discharged at 356 mA the voltage was 1.16 volt. A stationary layer of zinc powder in the lower water-rich phase resting on a 10 cm2 dense carbon anode, with a "Daramic" separator between the two phases gave a comparable result.

The zinc-bromine batteries described in Example I, II and VI were operated in various configurations with a non-woven "Webril" polypropylene separator of thickness 0.005 inches, between the carbon electrode and the aqueous phase. The performance was little changed at current densities of 20 mA cm-2 from cells without separator. A "CELGARD" 511 micro porous wettable film polypropylene from Celanese Plactics Company behaved similarly to the Webril separator, as did a "Daramic" separator supplied by Exxon Corporation.
In separate experiments it was established that cyanoethane containing bromine and zinc tribromide did not pass through the "Webril" separator or "Celgard" 511 separators into an aqueous solution.

Zinc-bromine cells containing 4-5 M bromine, 3 M NaCl and 0.5 M ZnBr2 in equal volumes of water and cyanoethane were operated in the discharge mode with two 1 dm2 Celgard 511 microporous separators with a 10 cm×10 cm×2 mm dense carbon cathode in the nitrile-rich phase, and two 10 cm×10 cm×2 mm zinc anodes in the water-rich phases on either side of the carbon. Separator and electrodes were in the vertical mode. Power densities of 50 mW cm-2 were obtained at 1.0-1.2 volt and >80% efficiency. Short term charging for intermittent periods at 20 mA cm-2 at 2.1 volt proceeded satisfactorily with formation of zinc and bromine.

A three electrode system based on Example VIII, operating in the bipolar horizontal mode with carbon cathode and zinc powder on carbon anode had an open circuit voltage of 3.5 V and a maximum power density of 40 mW cm-2. The carbon was somewhat porous which detracted from the long term performance of this bipolar battery.

The types of cells described in Examples VI and VII above were operated with little change in performance, by continuously dripping bromine into the cyanoethane rich phase containing a carbon cathode. Zinc powder half filled the anodic compartment which contained aqueous 2 M NaCl and zinc bromide solution. The zinc powder contacted a carbon felt or a high conductivity compact carbon anode and was renewed intermittently as a zinc slurry in 2 M NaCl. Zinc bromide solution was drained off from time to time in an amount equivalent to the 2 M brine slurry. Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention.

Oct.26 201 SKootS

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