CA1171815A

CA1171815A - Activating carbonaceous electrodes

Info

Publication number: CA1171815A
Application number: CA000357298A
Authority: CA
Inventors: Peter Carr; Alfred F. Laethem
Original assignee: Energy Development Associates Inc
Current assignee: Energy Development Associates Inc
Priority date: 1979-07-30
Filing date: 1980-07-30
Publication date: 1984-07-31
Also published as: US4273839A

Abstract

Abstract Described is a method of activating a carbonaceous electrode comprising the steps; 1. Providing a negative electrode and a carbonaceous positive electrode spaced apart from each other; 2. Providing an aqueous electrolyte with a current carrying water soluble material therein; and 3. Closing the circuit and passing a current between the positive and negative electrodes through the electrolyte thereby generating oxygen for a period of time sufficient to activate the positive electrode. The electrodes are useful in a metal halogen electrical energy storage device.

Description

- 1~71815 Description ACTIVATING CARBONACEOUS ELECTRODES

Background of the Invention In electrochemical processes, it is highly desirable that the reactions occur as near as possible to the theoretical open circuit voltage. Any means of activating an electrode to improve the operation of the electrode is highly desirable in any and all electrochemical processes, particularly as they relate to electrical energy storage devices ( EESD). One process for improving electrode activity is described in U.S.
Patent 4,120,774 entitled REDUCTICN OF ELECTRODE OVERVOLTAGE.
This patent employs a thermal treatment of electrodes with nitric acid for a long period of time to achieve satisfactory activation. Thermal treatment with nitric acid of electrodes may require that the electrodes be handled in a separate process from electrical energy stoarage devices. m ese difficulties have been overcome by the techniques described below.

Summary of the Invention Described i8 an electrochemical technique for activating carbonaceous electrodes. "Actlvating" i8 a procese of decreas-ing the overvoltage of electrodes in an electrochemical reaction. By "overvoltage" is meant the difference between t~e voltage neceseary to sustain an electrochemical reaction and the open circuit voltage. me invention is further described as a method of activating carbonaceous electrodes comprising the steps:
1. Providing a negative electrode and a carbonaceous po~itive electrode spaced apart from each other;

2. Providing an aqueous electrolyte with a current carrying water eoluble material therein; and

3. Closing the circuit and pa~sing a current between the positive and negative electrodes through the electrolyte thereby generating oxygen for a period of time sufficient to activate the positive electrode, i.e., an effective activating period of time.
~, - 1~7i815 Brief Description of the Drawings Fig. 1 is a diagrammatic view of the process of the present invention;
Fig. 2 is a sectional view of a submodule of assembled electrolytic cells;
Fig. 3 is a case for supporting a submoaule stack of electrolytic cells useful in the process of the present invention;
Fig. 4 is a sectional view along lines 4-4 of Fig. 2;
Fig. 5 is a sectional view taken along lines 5~5 of Fig.

4:
Fig. 6 is an exploded view of the electrodes useful in the process of the present invention;
Fig. 7 is a sectional view of the cell distribution manifold useful in the process of the present invention.
Fig. 8 is a graph plotting cell voltage against the degree o activation plotted on a charge and discharge phase;
Fig. 9 is a graph plotting cell voltage against current density on a charge and discharge phase comparing electrodes that have been unactivated versus activated for various current densities.

Detailed Description of Invention The present invention is concerned with a method for activating carbonaceous electrodes that are useful in electro-chemcial operations. By "carbonaceous electrodes" is meant electrodes that are comprised of carbon, such as carbon, activated carbon, graphite, activated graphite and mixtures thereof with other fillers that may be present in a carbona-ceous electrode.
The electrodes resulting from the activating process of the present invention are useful in a variety of electro-chemical processes wherein an activated electrode would be desirable. Such processes would be electrochemical generation or use of hydrogen, oxygen, halogen, such as chlorine, bromine, fluorine, iodine, oxides of halogen, as chlorates, bromates, iodates, primary or secondary fuel cells, such as the metal - ,.

1171~315 hydride type, or other electrical energy storage devices, such as the metal halogen rechargeable EESD. Most preferred is the EESD of the metal halogen hydrate type, such as the zinc halogen device descrihed in U.S.
3,713,388 or U.S. 4,049,880. Operations of zinc chloride battery systems are described in Electric Power Research Institute (EPRI) EM-249 Report for Project 226-1, Interim ~eport, September 1976; EM-1051, Parts 1-4, Project 226-3, Interim Report, April 1979; Cost Analysis of 50 KWH
Zinc-Chlorine Batteries for ~lobile Applications, U.S. Depart-ment of Energy Report C00-2966-1, January 1978 and Safety and Environmental Aspects of Zinc-Chlorine Hydrate satteries for Electric Applications, U.S. Department of Energy Report C00-2966-2, March 1978.
It has been found highly desirable that the carbonaceous electrode can be activated by subjecting it to an electroly-sis reaction wherein the carbonaceous electrode is the positive electrode in an electrical circuit and there is also present a negative electrode with an aqueous electrolyte therebetween.
The aqueous electrolyte contains a current carrying water soluble material. While any ionizable water soluble material may be employed, such as organic or inorganic materials, the most preferred are inorganic materials. Suitable examples of inorganic materials are salts of oxides of nitrogen, such as nitric acid, alkali and alkaline earth metal nitrates, such as sodium or potassium nitrate and the like, halogen salts, such as chloride, bromide, iodide, fluoride salts of alkali or alka-line earth metals, such as sodium chloride, potassium chloride, magnesium bromide, barium chloride, as well as the oxygenated form of said halide salts, such as the chlorates, bromates, iodates, and the like, halide acids, such as hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid and the like, oxides o sulfur, such as the sulfates, sulfites, sulfo-nates and the alkali metal or alkaline earth metal salts thereof, phosphates such as phosporic acid, sodium phosphate, borates such as boric acid, sodium borate, potassium meta-borate; carboxylic acid salts, as sodium acetate, potassium ;
~,~

117~81S

oxalate, sodium succinate and the like and non-reactive mix-tures thereof. Most preferred of the above enumerated salts are the metal halides, such as zinc chloride, hydrochloric acid and sodium sulfate, with the most preferred being hydrochloric acid optionally including zinc chloride.
It has been found highly desirable to achieve the desired activation that the electrolysis reaction be performed for a period of time such that the electrode is subjected to elec-trolysis corresponding to at least 5 milliamp hours (mAh) per square centimeter (cm2) of electrode surface area. This is called a minimum degree of activation. While the maximum degree of activation is quite high, it is desirable that the degree of actiVation not qxceed about 1000 mAh!cm2 of electrode surface, more preferably n~t abou~ 715 mAh/cm2. Most preferred activation is from about 30 to about 350 mAh/cm2.
During the electrolysis reaction, i.e., the imposition of a current density, oxygen and hydrogen are generated at the appropriate electrodes as well as oxides of carbon, such as carbon dioxide and carbon monoxide. Generation of the oxides of carbon is indicative of corrosion or degradation of the internal electrode surfaces, which increases the surface area and modifié~ the pore size of the electrodes.
An indication as to the amount of activation that has been obtained is the amount of oxides of carbon that are generated during the electrolysis reaction. To obtain the most desirable activation, the electrolysis reaction is to be conducted for a period of time sufficient to generate the gaseous oxides of carbon, preferably, between O.l and 30% by volume of oxides o carbon, most preferably, about lO to 25% of oxides of carbon, in a gaseous sample taken after 5 mAh/cm2 of electrolysis at the electrode surface.
When a zinc halide is employed as the current carrying salt in the aqueous electrolyte, it is preferred that the initial (prior to imposition of a current) pH range from about 1 to about 3, and p~eferably be about 2. With HCl the initial pH is about 1. With NaCl or KCl, optionally including .C~ ` ' 1~L7~L815 Na2SO4~ the p~ is about 7. In addition, when a halide is used, such as zinc chloride, the initial (prior to imposition of a current) concentration of the electrolyte is about 0.1 to about

5% by weight of the zinc chloride in water. A preferred range is 1% by weight zinc chloride in water (0.075 molar ZnC12 or 0.15 molar chloride) to 5% by weight zinc chloride in water (0.38 molar ZnC12 or 0.76 molar chloride).
Turning now to a discussion of the drawings, Fig. 1 is a schematic diagram of the operation of the device for activating the electrodes. In a container 10 sealed or unsealed, is placed an electrolyte reservoir 12 within a plastic reservoir 14. me electrolyte reservoir 12 functions as a sump from which electrolyte is pumped via line 16 by means of pu~p P into each of the stacks or submodules 18 via independent conduits 20. A valve V is placed in the line 16 so that the electrolyte may be changed or dumped as desired. m e processing apparatus 10 is shown as containing a hood 220from which the vapors are vented or treated in an environmental and economical manner.
If desired, the hood could be sealed at 240 in order to operate a closed system to increase pressure or decrease pressure in the apparatus 10 as desired. It is to be appreciated that the electrolyte that i5 flowing from the sump 12 via line 16 irto the submodules 18 can be heated or cooled aS desired by auxiliary apparatus (not shown~ ~
Fig. 2 is a cross-section of the electrochemical appara-tus of the present invention showing the electrolyte sump 12 being retained in a tray 22 and a series of electrical cells arranged in bipolar fashion having current terminals 19 and 21.
The current is passed through the current terminals to conven-tional bus bars which in turn are connected to connector studs (not shown), thereby passing the current to each of the indi-vidual cells in each submodule. Each stack of electrodes i9 retained in a submodule tray 22, a sectional view of which is shown in Fig. 3. The submodule tray has an electrolyte drain cup 24 to which is attached a conduit 26 which in turn is connected to a passageway for movement of electrolyte away from the submodule to the sump via exit line 28. If one ~esires to pre-vent parasitic losses during the charging of the stack, and to .~

1171~315 decrease the short circuiting that could possible occur, the electrolyte passes down the conduit 26 through a pair of opposed serpentine like channels, best shown in Fig. 3 as channel 30 and 32 respectively with flow in the direc-tion of the arrows. With respect to the parasitic losses, it is noted that the electrolyte flows through the patterns described, namely, channels 30 and 32, as a means of preventing electrical losses. This method of circulating the electrolyte is desirable and the electricity that is used during the charging operation goes primarily into the electro-chemical processes as opposed to dissipation through some other mechanism. The circulating electrolyte with the reactive materials therein is a source of self discharge.
The circulating electrolyte really acts like a wire to and from the electrode compartment. The object is to make the circulating electrolyte as resistive as possible.
Therefore, a way of performing that function is to lengthen the travel of the circulating electrolyte, as is done with the serpentine channels.
The most preferred embodiment involves electro-lyte flowing past the electrodes during the electrolytic activating reaction. To provide the flowing electrolyte, an electrolyte distribution manifold 34 is providéd for each submodule. The electrolyte flows from the sump 12 out exit port 36 and is pumped back to the submodule.
A sectional view showing a portion of a stack of electrodes with the porous carbonaceous electrode, which, ,i~
! in the most preferred embodiment, is the chlorine electrode ; o a zinc chlorine electrical energy storage device, is ., ~ 6 -' mAh / ~b , :

. .

7~L815 shown in Fig. 4. The submodule, which is a stack 18 of ten cells, is inserted into the interior 35 of the sub-module tray 22 wherein the electrolyte distribution mani-fold 34 would be joined with the submodule tray by posi-tioning the manifold into channels 38.
It is to be appreciated that the electrodes or submodules could be combined in series or parallel relation-ship as is well known in the art.
The porous chlorine electrode 40 is arranged such that a pair of porous carbon plates 40a and 40b are joined together forming a cavity 41 to allow passage of electro-lyte therethrough as shown by arrows 42. Gas ~enting holes (not shown) may be provided at the top of the porous chlorine electrode. To prevent distortion of the porous chlorine electrodes, stub 44 is present in the middle of the chlorine electrode to give strength thereto. The porous chlorine electrodes are manufactured to have an indented portion 46, in which the electrolyte feed tube 48 may be inserted. The electrolyte feed tube in turn is connected to the internal electrolyte distribution manifold at point 50. The electrolyte distribution manifold is com-prised of a pair of complementary members 52 and 54 which are fastened together by nuts 56 and bolts 58.

' , - 6a -mab/ ~V
~ .
.' -- ~17~8~5 A bipolar intermediate bus 60 is machined to receive the chlorine electrodes at points 62 and 64, while adjacent thereto is the metal or zinc electrode 68 which fits into the intermedi-ate bipolar bus at point 70. To prevent short circuiting, to - insure tight fit, to control discharge rates of chlorine elec-trode, and to control the edge effects thereof, spacers 72 and 74 join together the chlorine and zinc electro~es which are arranged in bipolar fashion.
In operation the electrolyte is flowed from the sump 12 through external manifold 80 into interior manifold 82 which is a conduit which i9 connected to the electrolyte distribution manifold at point 84. From the electrolyte distribution mani-fold, the electrolyte is passed through tubes 48 whereby the electrolyte exits from the tube at the bottom of the halogen electrode at point 83 and the electrolyte flows through the ' porous electrodes up the intercell spacing 84 into drain cup 24 down the exit conduit 26, into channels 30 and 32 as described above and out the exit 28 back to the sump.
The separation between the porous positive electrode and the negative electrode ranges from about 40 mils (1 mm) to ~ about 250 mils (6mm), preferably 80 mils (2 mm).
,~, It is to be appreciated that the operation of the method o the present invention as it relates to activating carbona-~ ceous electrode~ may be performed in a manner such that one or ;, more electrodes may be activated simultaneously. For conven-ience, the drawing~ are directed towards the most preferred technique, which is the activation of a stack of electrodes i that are interdigitated, such as that described in U.S. Patent 4,100,332. It i9 to be apprecizted that the activation of carbonaceous electrodes may be performed in any individual electrolytic cell containing positive and negative electrodes or a stacX of same. The most preferred techni~ue is to utilize the electrochemical activat-ing process of the present invention on the final form of electrodes as they are going to be employed in an electrical ;~ energy storage device such as the metal halogen hydrate battery described in U.S. 3,718,888, described above. When following .. .
',~ ~
. ~

, , 11718~5 that procedure, the electrodes are assembled into the stack or submodule as is shown in the drawings. Thereafter, the halogen hydrate formation apparatus (25) necessary for forming and storing the halogen hydrate during the charging and discharging of the electrical energy storage device is assembled to the apparatus useful in this invention via line 23. Any conven-tional halogen hydrate formation and storage equipment may be used such as that described in U.S. 3,713,888; 3~823,036, or Electric Power Research Institute reports and U.S. Department of Energy reports discussed supra.
Therefore, prior to the charging of said metal halogen electrical energy storage device, the electrode stack would be subjected to an activating procedure using the electrolyte as described above. Thereafter, the electrolyte may or may not be removed from the sump depending upon the desired end use of the electrical energy storage device. Most preferably, however, the electrolyte utilized in the activation step would be removed such as through drain 17 and then the new electrolyte introduced, which would be the electrolyte used during the charging and discharging operation of the electrical energy storage device. The steps most preferred are as follows:
l. Activating the positive electrodes of an electrical energy storage device;
2. Assembling the activated electrodes into a metal halogen electrical energy storage device;
3. Then charging the electrical energy storage device:
and 4. Discharging the electrical energy storage device.
Currently contemplated is that after the activation process of Step 1, one then holds the electrode stack until needed, i.e., building up an inventory of the stacks. During the activation process when zinc chloride is the electrolyte, ~inc may be deposited on the negative electrode. It is desirable to remove that zinc prior to assembling the stack into the desired EESD. It is also to be appreciated that during Ste~ 3 w~uld take ~lace the de~osition of metal on the neqative electrode and the formation of a halogen hydrate or other means of storing the halogen generated during the charging operation.

,~ ~

g Having described the invention in general, listed below are preferred embodLments wherein all temperatures are in degrees Centigrade and all parts are parts by weight unless otherwise indicated.

Example 1 A submodule containing ten stacks of electrodes in series as shown in Fig. 2 was electrolytically activated using dilute (~1% by weight) zinc chloride in water whose pH had been adjusted to ~J2. The initial chloride ion concentration was determined to be 0.18M; an electrolyte volume of ~60 litre was employed. Electrolytic processing was performed at a current density of 30 mA/cm2 for a period of 5 hours, the extent of processing therefore being 150 mAh/cm2. m e electrolyte flow rate during processing was maintained at 2 ml/cm2/min. Over the processing period it was observed that the temperature rose from 16C (initial) to 40C (after 4 hours). During the last hour, a temperature C40c was maintained. The voltage dropped ~teadily from its initial value of 31.62V to as low as 29.20V.
An analysis (by gas chromatography) of the gases produced verified that anode corrosion was taking place:
Hydrogen 69% by volume oxygen 12% by volume Carbon Monoxide 3% by volume Carbon Dioxide 16% by volume During the 5 hour processing period gas phase composition did vary; however, the above analytical values are cited as typical of that found during the last three hours.
After electrolytic processing, the bath was discarded.
The battery was rinsed with distilled water (circulated with system pump).
The voltaic performance of the activated battery unit is shown in Table I A and B. For comparison purposes, the per-formance of a (similar) battery which had not been processed, i.e, in the unactivated state, is also presented. Test conditions employed were:

il7~315 lectrolyte: 26% by weight ZnC12 (SpG 1.275), pH adjusted to 0.05 with HCl Electrolyte flow rate (charge and discharge~ 2 ml/cm2/min Chlorine concentration ~dissolved in electrolyte) while discharging: approximately saturated Temperature: Charge: 22-30C
Discharge: 24-28C

TABLE l-A
Performance of Battery In Vnactivated State Charge Discharge Current Density Current Density (mA/cm2 (mA/cm2 electrode surface) V* electrode surface) V*
2.286 10 1.901 2.368 20 1.789 2.435 30 1.705 2.487 40 1.630 2.528 50 1.560 2.562 60 1.494 TABLE l-B
Performance of Battery After Electrolytic Activation Charge Discharge Current Density Current Density (mA/cm2 (mA/cm2 electrode surface) _ electrode surface) V*
2.185 10 2.096 2.232 20 2.057 2.272 30 2.016 2.308 40 1.970 2.342 50 1.919 2.374 60 1.868 *Values are in volts/cell; submodule battery voltage is ten times this value.

Example 2 A single cell test stand was ~abricated having a porous positive (chlorine) electrode (10 cm x 10 cm) and a graphite negative (zinc) electrode (10 cm x 10 cm). Electrolyte was supplied by a manifolding arrangement such that it passed through the porous electrode, between the inter cell spacing and out the top of the negative electrode. The cell assembly was held together by a clamping arrangement and then placed in a glass jar which served as the electrolyte sump.
To demonstrate the relationship between the activation of the chlorine (po~itive) electrode and its increa~ed efficiency when following the process of the present invention, the test cell was subjected to a series of activation tests. m e activation electrolyte was the same as Example 1. No attempt was made to control temperature. Two liters of electrolyte was employed.
To determine the voltaic performance of the cell (charge and discharge), an aqueous electrolyte was formulated of 2M
ZnC12 1 5M KCl having a pH of 0.2 (adjusted with HCl). During the charge the chlorine generated was vented. It i8 to be appreciated that any conventional technique for forming chlorine hydrate could have been employed. During discharge, chlorine from a cylinder was passed into the electrolyte to maintain a ~aturated dissolved chlorine level. The temperature was about 50-C with an electrolyte flow rate during charge of 2 ml/cm2/min and on discharge of 3.5 ml/cm2/min. The test cell was rinsed with water after electrolytic activation and prior to charging. The test results are graphically shown in Figs. 8 and 9.

Example 3 Following the procedure and apparatus of Example 2, electrolytic activation baths other than zinc chloride were tested. Selected electrolytes are shown in Table II.

TABLE II

Exper- Bath Initial Current Hours Extent iment Composition pH Densitx Electro- Processe2d (mA/cm~) lvzed (mAh/cm__ A HCl, O.lM 0.7 30.0 5 lS0 B NaCl, 0.2M 2 06.5 11 71.5 C ~a2S04, 0.2M 2 06.5 11 71.5 Voltaic performance and polarization characteristics are shown in Table~ III A-C.

TABLE III-A
Performance After HCl Activation*
Charge Discharge Current Density (mA/cm,) Volts (V) Volts (V) ~2.153 2.088 2.172 2.064 2.191 2.028 2.209 1.993 2.217 2.226 1.958 2.241 1.924 2.256 1.887 2.270 1.810 2.283 1.768 100 2.296 ~Electrolytic conditions for charge and discharge:
Electrolyte: 2M ZnC12, 5M KCl Temperature was about 50C
Electrolyte Flow Rate of 2 ml/cm2 o electrode surface/min ' - .:
- -7~315 TABLE III-B
Performance After NaCl Activation*
Charge Discharge Current Density (mA/cm_) Volts (V) Volts (V) 2.133 2.074 2.161 2.043 2.176 2.026 2.190 2.009 2.215 1.972 2.227 1.952 2.239 1.930 2.261 1.880 *Electrolytic conditions for charge and discharge:
Same as Table III-A except flow rate was 2/3 ml/cm2 of electrode surface/min.

TABLE III-C
Performance After N~ ~_Activation*
Charge Discharge Current Density (mA/cm_) Volts (V) Volts (V) 2.127 2.071 2.161 2.043 2.176 2.027 2.189 2.010 2.212 1.976 2.223 1.95 2.234 1.940 2.255 1.899 *Electrolytic conditions for charge and discharge:
Same as Table III-A.

.

1~1815 In the working examples described above, a porous (PG-60 type) graphite electrode was employed as the chlorine electrode while the metal or zinc electrode was ATJ or EBP graphite which is of a nonporous type. The porous electrode is available from the trade as a PG~60 type. The electrodes had a surface area of 62.5 square centime~ters and the plastic materials are substantially made of KYNAR (trademark of Pennwalt Corp. for a homopolymer of the vinylidene fluoride type). It is to be appreciated that the activation time employing the electrolytic process as described herein is substantially shorter than the thermal process employing nitric acid as described above in U.S. Patent 4,120,774.
It is to be appreciated therefore that for desirable activation that the amount of oxides of carbon that should be produced can range from as low as 0.1 to about 30~ by volume of the gases produced during the activation process, preferably 10~ to 25~. While substantially higher percentages of gases may be produced resulting in activation of electrodes, weakening of the electrodes can easily result since oxides of carbon are an indiction of degradation of electrodes.
While Applicants do not wish to be held to any theory, it appears that there is an activated surface that is due to the electrochemical operation. It is believed that the electrode surfacé area (square meter per gram of electrode surface) is increased by virtue of the electrolytic reaction from 0.6 ~nonactivated) to 9, preferably about 2 to about 5, and even more preferably, about 2-3 (square meters per gram).
While it is believed that the electrolytic activation described herein results in permanent improvements to the electrode, the activation process may be conveniently performed any number of times after initial use to increase activity (decrease electrode overvoltage) of the electrode.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for activating a carbonaceous elec-trode comprising the steps:

1. Providing a negative electrode and a car-bonaceous positive electrode spaced apart from each other;
2. Providing an aqueous electrolyte with a current carrying water soluble material therein; and 3. Closing the circuit and passing a current between the positive and negative electrodes through the elec-trolyte thereby generating oxygen for a period of time suffi-cient to activate the positive electrode, wherein the current is passed from about 5 mAh/cm2 to about 1000 mAh/cm2 of elec-trode surface of the positive electrode for a period of time such that a sample of gas generated after said period of time contains gaseous oxides of carbon in amount of 0.5% to 30%
by volume.

2. The method of claim 1 wherein the electrolyte is a metal halide aqueous electrolyte.

3. The method of claim 2 wherein the metal halide has a concentration of at least 0.1% by weight.

4. The method of claim 3 wherein the metal halide is zinc chloride.

5. The carbon electrode produced by the process of claim 4.

6. The method of claim 1 wherein the electrolyte is comprised of hydrochloric acid.

7. The carbon electrode produced by the process of claim 6.

8. The carbon electrode produced by the process of claim 1.

9. The process of claim 1 wherein the amount of oxides of carbon ranges from about 10 to about 25%.

10. In a method of operating an electrical energy storage device employing carbonaceous positive elec-trodes wherein the device is electrically charged and dis-charged, the improvement comprising the steps of:
1. Prior to charging the device, activating the positive electrode by providing an aqueous electrolyte with a current carrying water soluble material therein; and 2. Closing the circuit and passing a current between the positive and negative electrodes through the electrolyte thereby generating oxygen for a period of time sufficient to activate the positive electrode, wherein the current is passed from about 5 mAh/cm2 to about 1000 mAh/cm2 of electrode surface of the positive electrode for a period of time such that a sample of gas generated after said period of time contains gaseous oxides of carbon in amount of 0.5%
to 30% by volume.

11. The method of claim 10 wherein the electro-lyte is a metal halide aqueous electrolyte.

12. The method of claim 11 wherein the metal halide has a concentration of at least 0.1% by weight.

13. The method of claim 12 wherein the metal halide is zinc chloride.

14. The method of claim 10 wherein the electro-lyte is comprised of hydrochloric acid,

15. The method of claim 14 wherein the electrical energy storage device is rechargeable metal halogen device.

16. The method of claim 15 wherein the metal halogen device is a metal halogen hydrate device.

17. The method of claim 16 wherein the device is a zinc chlorine chlorine hydrate device.

18. The process of claim 10 wherein the amount of oxides of carbon ranges from about 10 to about 25%.

19. The method of claim 10 comprising performing in sequence the activation process, removing the electrolyte and inserting new electrolyte prior to using the electrodes in the electric energy storage device.