FLUOROSURFACTANT AS A ZINC CORROSION INHIBITOR

Abstract

An alkaline electrochemical cell, preferably a zinc/air cell which includes a container; a negative electrode, a positive electrode, wherein said negative electrode and said positive electrode are disposed within the container, a separator located between the negative electrode and the positive electrode, and an alkaline electrolyte, wherein the negative electrode comprises zinc, and a branched chain fluorosurfactant. The fluorosurfactant is preferably a sulfotricarballylate surfactant with multiple fluorinated end groups.

Claims

1. An alkaline electrochemical cell, comprising: a container; a negative electrode, a positive electrode, wherein said negative electrode and said positive electrode are disposed within the container, a separator located between the negative electrode and the positive electrode, and an alkaline electrolyte, wherein the negative electrode comprises zinc, and a sulfotricarballylate surfactant.

2. The cell according to claim 1, wherein the sulfotricarballylate is characterized by the formula ##STR00006## and where Z.sub.1=Z.sub.2=Z.sub.3=F.sub.3C(CF.sub.2).sub.ai(CH.sub.2).sub.bi(O(CH.sub.2).sub.ci).sub.di—, where ai=1-2, bi=1-2, ci=2, di=1-3.

3. The cell according to claim 1, wherein the sulfotricarballylate is characterized by the formula ##STR00007## and where Z.sub.1=Z.sub.2=Z.sub.3 =F.sub.3C(CF.sub.2)(CH.sub.2)(O(CH.sub.2CHCH.sub.2CH.sub.3)).

4. The cell according to claim 1, wherein the sulfotricarballylates contains three fluorinated end groups.

5. The cell according to claim 1, wherein the sulfotricarballylates is in the form of a mixture.

6. The cell according to claim 1, wherein the sulfotricarballylates is present in an amount from 10 to 200 ppm based on the total weight of the zinc.

7. The cell according to claim 1, wherein the sulfotricarballylates is present in an amount from 10 to 100 ppm based on the total weight of the zinc.

8. The cell according to claim 1, wherein the sulfotricarballylates is present in an amount from 10 to 40 ppm based on the total weight of the zinc.

9. The cell according to claim 1, wherein the positive electrode comprises manganese dioxide.

10. The cell according to claim 1, wherein the positive electrode is an air electrode.

11. The cell according to claim 4, wherein each said fluorinated end groups comprises F.sub.3C(CF.sub.2).sub.2.

12. The cell according to claim 4, wherein each said fluorinated end groups comprises F.sub.3C(CF.sub.2).

13. An alkaline electrochemical cell, comprising: a container; an electrode assembly disposed within the container and comprising a negative electrode, a positive electrode, a separator located between the negative electrode and the positive electrode, and an alkaline electrolyte, wherein the negative electrode comprises zinc, and a fluorosurfactant, wherein said fluorosurfactant has more than one fluorinated end group.

14. The cell according to claim 13, wherein said surfactant has three fluorinated end groups.

15. The cell according to claim 13, wherein said surfactant further has an anionic polar group.

16. The cell according to claim 13, wherein said fluorinated end group is identical.

17. The cell according to claim 13, wherein said fluorosurfactant is of the formula ##STR00008## where the groups Z.sub.i(Z.sub.1,Z.sub.2, and Z.sub.3) are, independently of one another, branched or unbranched alkyl groups or groups of the structure R.sub.i(A(CR.sub.1R.sub.2).sub.ci—(CR.sub.3R.sub.4).sub.c′i).sub.di—, where the respective indices ci and c′i are, independently of one another, 0-10, and di=0-5, where R, is a branched or unbranched, fluorine-containing alkyl radical, R.sub.1 to R.sub.4 are, independently of one another, hydrogen or a branched or unbranched alkyl group, ci and c′i are not simultaneously 0, and A=O, S and/or N, Y.sub.1 is an anionic polar group and Y.sub.2 is a hydrogen atom, or vice versa, X is a cation, and at least one of the groups Z, is a group of the structure R.sub.i(A(CR.sub.1R.sub.2).sub.ci—(CR.sub.3R.sub.4).sub.c′i).sub.di—.

18. The cell according to claim 15, wherein said anionic polar group is a sulfonate group.

19. The cell according to claim 10, wherein the concentration of the surfactant is 10-1000 parts per million based on the total weight of the zinc, and forms at least on monolayer on the surface of said zinc.

20. The cell according to claim 13, wherein said surfactant has a molecular weight of between 800 and 1320.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the drawings:

[0020] FIG. 1 is an elevational view, in cross-section, of a metal-air cell with a catalytic electrode;

[0021] FIG. 2 is an illustration of the results of Example 1 showing the gas generation of various samples.

[0022] FIG. 3 is scanning electron microscope pictures of zinc with and without the surfactant of the present invention as described in Example 2.

[0023] FIG. 4 is an illustration of the results of Example 3 showing true internal resistance at 50 KHz of various samples.

[0024] FIG. 5 is an illustration of the results of Example 3 showing polarization at 40 Hz minus 50 KHz of various samples.

[0025] FIG. 6 is an illustration of the results of Example 4 showing service of various samples to various functional end points.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] As shown in an example of an electrochemical cell according to the invention is shown in FIG. 1. The cell 110 can include a cathode casing 112 and an anode casing 126. At least one aperture 118 is present in the cathode casing 112 to act as an air or oxygen entry port. A catalytic positive electrode (such as an air electrode) 120 is disposed near the aperture 118 in the cathode casing 112. The catalytic electrode 120 can include a catalytic layer containing a mixture of carbon, a catalyst, and a binder. Catalytic electrode 120 preferably has a barrier layer 122 laminated thereon. The barrier layer 122 can be laminated on the side of the catalytic electrode closest to the aperture 118 cell. Catalytic electrode 120 can contain an electrically conductive current collector 123 embedded therein, preferably on the side of the electrode opposite the barrier layer 122. The cell 110 may optionally contain a second barrier layer 137 between the first barrier layer 122 and central region 114 of the surface of the cathode casing 112 containing the aperture 118. The barrier layers 122, 137 have a low enough surface tension to be resistant to wetting by electrolyte, yet porous enough to allow oxygen to enter the electrode at a rate sufficient to support the desired maximum cell reaction rate. At least one layer of separator 124 is positioned on the side of the catalytic electrode 120 facing the anode 128. The separator 124 is ionically conductive and electrically nonconductive. The total thickness of the separator 124 is preferably thin to minimize its volume, hut must be thick and strong enough to prevent short circuits between the anode 128 and catalytic electrode 120. The separator 124 can be adhered to the surface of the catalytic electrode 120 to provide good ion transport between the electrodes and to prevent the formation of gas pockets between the catalytic electrode 120 and the separator 124. Similarly, adjacent layers of the separator 124 can be adhered to each other, A layer of porous material 138 can be positioned between catalytic electrode 120 and the surface of casing 112 to evenly distribute oxygen to electrode 120. A sealant 129 can be used to bond portions of the catalytic electrode 120 to the cathode casing 112. The anode casing 126 can have a rim 135 that is flared outward at its open end. Alternatively, a cell can essentially straight side walls with little or no outward flare or a rim that is folded outward and back along the side wall to form a substantially U-shaped side wall with a rounded edge at the open end of the casing. The anode casing 126 can have an inner surface 136 in contact with the anode mixture 128 and electrolyte. Cell 110 can includes a gasket 130, made from an elastomeric material for example, to provide a seal between the cathode casing 112 and anode casing 126. The bottom edge of the gasket 130 can be formed to create an inwardly facing lip 132, which abuts the rim of anode casing 126. Optionally, a sealant may be applied to the sealing surfaces of the gasket 130, cathode casing 112 and/or anode casing 126. A suitable tab (not shown) can be placed over the openings 118 until the cell 110 is ready for use, to keep air from entering the cell 110 before use.

[0027] A catalytic layer 121 contains a catalytic composition that includes composite particles comprising nano-catalyst particles adhered to (e.g., adsorbed onto) the external and internal surfaces (including surfaces of open pores) of highly porous carbon substrate particles.

[0028] Examples of zinc air cell cathode construction that can be used in conjunction with the present invention are disclosed in U.S. Patent Application Publication No. 2008/0155813 A1.

[0029] The anode casing 126 forms the top of the cell and has a rim 135 which is flared outward at its open end. Alternatively, a cell can have a refold anode casing in which the rim is folded outward and back along the side wail to form a substantially U-shaped side wall with a rounded edge at the open end of the casing, or the anode casing can have essentially straight side walls and that has a rim with little or no outward flare.

[0030] The anode casing 126 can be formed from a substrate including a material having a sufficient mechanical strength for the intended use such as stainless steel, mild steel, cold rolled steel, aluminum, titanium or copper. Preferably the anode casing includes one or more additional layers of material to provide good electrical contact to the exterior surface of the anode casing 126, resistance of the external surface to corrosion, and resistance to internal cell gassing where the internal surface of the anode casing 126 comes in contact with the anode 128 or electrolyte. Each additional layer can he a metal such as nickel, tin, copper, or indium, or a combination or alloy thereof, and layers can be of the same or different metals or alloys. Examples of plated substrates include nickel plated steel, nickel plated mild steel and nickel plated stainless steel. Examples of clad materials (i.e., laminar materials with at least one layer of metal bonded to another layer of metal) include, as listed in order from an outer layer to an inner layer, two-layered (biclad) materials such as stainless steel/copper, three-layered (triclad) materials such as nickel/stainless steel/copper and nickel/mild steel/nickel, and materials with more than three clad layers.

[0031] The anode casing 126 can include a layer that is post-plated (i.e., plated after forming the anode casing into its desired shape). The post-plated layer is preferably a layer of metal with a high hydrogen overvoltage to minimize hydrogen gassing within the cell 110. Examples of such metals are copper, tin, zinc, indium and alloys thereof. A preferred metal is tin, and a preferred alloy is one comprising copper, tin and zinc.

[0032] Cell 110 also includes a gasket 130 made from an elastomeric material which serves as the seal. The bottom edge of the gasket 130 has been formed to create an inwardly facing lip 132, which abuts the rim of anode casing 126. Optionally, a sealant may be applied to the scaling surface of the gasket, cathode casing and/or anode casing. Suitable sealant materials will be recognized by one skilled in the art. Examples include asphalt, either alone or with elastomeric materials or ethylene vinyl acetate, aliphatic or fatty polyamides, and thermoplastic elastomers such as polyolefins, polyamine, polyethylene, polypropylene and polyisobutene.

[0033] During manufacture of the cell, anode casing 126 can be inverted, and then a negative electrode composition or anode mixture 128 and electrolyte put into anode casing 126. The anode mixture insertion can be a two-step process wherein dry anode mixture materials are dispensed first into the anode casing 126 followed by KOH solution dispensing. Alternatively, the wet and dry components of the anode mixture are preferably blended beforehand and then dispensed in one step into the anode casing 126. Electrolyte can creep or wick along the inner surface 136 of the anode casing 126, carrying with it materials contained in anode mixture 128 and/or the electrolyte.

[0034] An example of an anode mixture 128, for a button cell comprises a mixture of zinc, electrolyte, and organic compounds. The anode mixture 128 preferably includes zinc powder, a binder such as CARBOPOL® 940 or CARBOPOL® 934, and a gassing inhibitor such as indium hydroxide (In(OH).sub.3) in amounts of about 99.7 weight percent zinc, about 0.25 weight percent binder, and about 0.045 weight percent indium hydroxide. CARBOPOL® 934 and CARBOPOL® 940 are acrylic acid polymers in the 100% acid form and are available from Noveon Inc. of Cleveland, Ohio.

[0035] The electrolyte composition for a button cell can be a mixture of about 97 weight percent potassium hydroxide (KOH) solution where the potassium hydroxide solution is 28-40 weight percent, preferably 30-35 weight percent, and more preferably about 33 weight percent aqueous KOH solution, and about 3.00 weight percent zinc oxide (ZnO).

[0036] The electrolyte composition for a prismatic cell can be a mixture of about 97 weight percent potassium hydroxide (KOH) solution where the potassium hydroxide solution is about 28 to about 40 weight percent, preferably about 30 to about 35 weight percent, and more preferably about 33 weight percent aqueous KOH solution, and about 1.00 to 3.00 weight percent zinc oxide (ZnO).

[0037] Preferred zinc powders are low-gassing zinc compositions suitable for use in alkaline cells with no added mercury. Examples are disclosed in U.S. Pat. No. 6,602,629 (Guo et al.), U.S. Pat. No. 5,464,709 (Getz et al.) and U.S. Pat. No. 5,312,476 (Uemura et al.), which are hereby incorporated by reference.

[0038] One example of a low-gassing zinc is ZCA grade 1230 zinc powder from Zinc Corporation of America, Monaca, Pennsylvania, which is a zinc alloy containing about 400 to about 550 parts per million (ppm) of lead. The zinc powder preferably contains a maximum of 1.5 (more preferably a maximum of 0.5) weight percent zinc oxide (ZnO). Furthermore, the zinc powder may have certain impurities. The impurities of chromium, iron, molybdenum, arsenic, antimony, and vanadium preferably total 25 ppm maximum based on the weight of zinc. Also, the impurities of chromium, iron, molybdenum, arsenic, antimony, vanadium, cadmium, copper, nickel, tin, and germanium preferably total no more than 68 ppm of the zinc powder composition by weight. More preferably, the zinc powder contains no more than the following amounts of iron, cadmium, copper, tin, chromium, nickel, molybdenum, arsenic, vanadium, antimony, and germanium, based on/the weight of zinc: Fe—3.0 ppm, Cd—8 ppm, Cu—8 ppm, Sn—1 ppm, Cr—1 ppm, Ni—1 ppm, Mo—0.25 ppm, As—0.1 ppm, Sb—0.2 ppm, V—1 ppm, and Ge—0.06 ppm.

[0039] In another embodiment, the zinc powder preferably is a zinc alloy composition containing bismuth, indium and aluminum. The zinc alloy preferably contains about 100 ppm of bismuth, 200 ppm of indium, and 100 ppm of aluminum. The zinc alloy preferably contains a low level of lead, such as about 35 ppm or less. In a preferred embodiment, the average particle size (D.sub.50) is about 90 to about 120 microns. Examples of suitable zinc alloys include product grades NGBIA 100, NGBIA 115, and DIA available from N.V. Umicore, S.A., Brussels, Belgium.

[0040] The selection of zinc additives, for corrosion control, can be very challenging. Since these additives are often surfactants which have interactions with other components, they can influence viscosity and rheology properties. Surfactants form films on the zinc surface which impact cell impedance and rate capability, and can influence the solubility of ZnO. They are often extremely concentration dependent which further complicates their evaluation. Surfactants used in zinc air cell anode formulations such as Disperbyk 102 and Carbowax 550 are extremely concentration sensitive and have significant impact on front end rate capability and cell impedance. It is desired to use a zinc additive which forms a thin but dense film on the zinc surface and is robust to concentration effects above the monolayer requirement.

[0041] In order to find a zinc additive that provides a thin but dense film on the surface of zinc which effectively reduces corrosion without having a negative impact on cell impedance and high rate performance, a sulfotricarballylate which is a fluorosurfactant with short chain, branched fluorocarbon end groups and carboxylate acid anchor groups was used as a zinc additive in an alkaline zinc air cell. The sulfotricarballylate is available as Tivida L2300 from EMD Millipore, also known as Merck Millipore outside the United States and Canada.

[0042] A first embodiment relates to alkaline cells with zinc additive compounds of the formula (I).

##STR00003##

where the groups Z.sub.i(Z.sub.1,Z.sub.2, and Z.sub.3) are, independently of one another, branched or unbranched alkyl groups or groups of the structure R.sub.i(A(CR.sub.1R.sub.2).sub.ci—(CR.sub.3R.sub.4).sub.c′i).sub.di—, where the respective indices ci and c′i are, independently of one another, 0-10, and di=0-5, where R.sub.i is a branched or unbranched, fluorine-containing alkyl radical, R.sub.1 to R.sub.4 are, independently of one another, hydrogen or a branched or unbranched alkyl group, ci and c′i are not simultaneously 0, and A=O, S and/or N, Y.sub.1 is an anionic polar group and Y.sub.2 is a hydrogen atom, or vice versa, X is a cation, and at least one of the groups Z, is a group of the structure R.sub.i(A(CR.sub.1R.sub.2).sub.ci—(CR.sub.3R.sub.4).sub.c′i).sub.di—. It is preferred for formula (I) that di>0 if Z.sub.1,Z.sub.2, and Z.sub.3 are all a group of the structure R, (O(CH.sub.2)).sub.c′i).sub.di and all R, are selected from CF.sub.3CF.sub.2CH.sub.2—, CF.sub.3CF.sub.2CH.sub.2CH.sub.2—, CF.sub.3CF.sub.2CF.sub.2CH.sub.2— or H(CF.sub.2).sub.4CH.sub.2—.

[0043] The radicals R, are branched or unbranched, fluorine-containing alkyl groups. The radicals R, may be partly or perfluorinated and preferably contain terminal perfluorinated groups. Preference is given to branched or unbranched, fluorine-containing alkyl groups having 1 to 10 C atoms. Unbranched fluorine-containing alkyl groups preferably contain 1 to 6 C atoms, in particular 1-4 C atoms. Branched fluorine-containing alkyl groups preferably contain 3 to 6 C atoms, in particular 3-4 C atoms. The branched fluorine-containing alkyl groups used are preferably (CF.sub.3).sub.2—CH— or (CF.sub.3).sub.3—C— groups.

[0044] Another embodiment relates to alkaline cells with zinc additive compounds of the formula (Ia)

##STR00004##

[0045] are, in particular, compounds in which all variables have the preferred meanings. Preference is explicitly given to compounds in which Z.sub.1=Z.sub.2=Z.sub.3=F.sub.3C(CF.sub.2).sub.ai(CH.sub.2).sub.bi(O(CH.sub.2).sub.ci).sub.di—, where ai=1-2, bi=1-2, ci=2, di=1-3, and the anionic polar grout is a sulfonate group —SO.sub.3.sup.−, and associated with a sodium ion.

[0046] Still another embodiment relates to alkaline cells with zinc additive compounds of the formula (Ib).

##STR00005##

[0047] Preferred compounds of the formula (Ib) where Z.sub.1=Z.sub.2=Z.sub.3 and all Z, are selected from R.sub.i(O(CH.sub.2).sub.ci).sub.di—, where ci=2, di=1-3, and R.sub.i=CF.sub.3CF.sub.2CH.sub.2— or CF.sub.3CF.sub.2CF.sub.2CH.sub.2—.

[0048] The compounds of the formulas I, Ia and formula lb are referred to in the present invention as sulfotricarballylates and are based on esters of aconitic acid, onto the double bond of which a sulfonate group has been added. In particular, sulfotricarballylates containing three fluorinated end groups according to the invention are preferred. The compounds of the formula (I) according to the invention can also be in the form of mixtures, particularly also in the form of isomer mixtures (constitutional and/or configurational isomer mixtures). In particular, diastereomer and/or enantiomer mixtures are possible. Examples of sulfotricarballylates and their synthesis are disclosed in U.S. Patent Application Publication No. 2012/0111233 A1.

[0049] The sulfotricarballylate compounds of the formulas I, Ia and formula Ib containing more than one fluorinated end groups are preferred. The sulfotricarballylate compounds can have a molecular weight preferably between 800 and 1320, most preferably between 850 and 1000. The sulfotricarballylate compounds when added to an alkaline zinc electrode form a monolayer on the surface of the zinc the width of which can be estimated. It is preferred that this monolayer be as thin as possible so as to minimize polarization. Long chain surfactants because of their structure will have much thicker monolayers. Preferred monolayer thickness is less than 50 Angstroms, and it is most preferred to have a monolayer thickness less than 25 angstroms.

[0050] A number of approaches have been proposed to screen zinc corrosion reduction additives. These include: a gel expansion test, a zinc gas generation test, measurement of anode impedance at both low and high frequency which provides information on the thickness and ion mobility associated with film formation on the surface of zinc, SEM images of zinc morphology, and whole cell performance and shelf characterization.

EXAMPLES

[0051] The following non-limiting examples are provided to further illustrate the present disclosure. Example 1

[0052] Zinc additives of interest were assembled and associated hydrogen generation was measured per a ten gram gassing test. Average gas generation was measured for ten grams of zinc over three days at 45C and reported as ul/g/day. The ten gram gassing test consists of measuring the gas generation of zinc (with or without a zinc additive) in an electrolyte solution. The electrolyte solution is prepared by first taking 500 ml of 45% KOH solution and then adding 160 mls of water and 75 grams of ZnO. Ten grams of the zinc along with any zinc additive are added to a reaction vessel along with 5 ml of the electrolyte solution and a small amount of light mineral oil. The reaction vessel is adapted so that evolved hydrogen gas can be measured. The reaction vessel is added to a 45C water bath and allowed to come up to temperature. After three days the hydrogen gas is measured and recorded and ul/g/day is calculated. The additives studied are shown in Table 1.

TABLE-US-00001 TABLE 1 Material Chemical information Tivida L2300 sulfotricarballylate Epikure 8538Y68 Polyethylene polyamine Tomamine E14-2 Ethoxylated Amine Disperbyk 102 Poly(oxy ethanediyl) isotridecyl hydroxy phosphate Alkaterge T Oxazoline MPEG 550 Methoxypolyethylene Glycol SHMP Sodium Hexametaphosphate

[0053] The above zinc additives evaluated at different concentrations. In all experiments the surfactant concentration is relative the weight of the zinc powder. Two zincs were used: Mitsui 81207-21 zinc, with full particle size distribution, and Grillo BIA zinc which is pre-screened to be greater than 300 microns in particle size.

[0054] FIG. 2 includes a graph showing the average gas generation rates for the listed additives. Each zinc additive was evaluated at 100 ppm concentration relative a control that had no zinc additive added. This initial screen shows significant gassing reduction relative the control for all the additives and suggested that these zinc additives should be further evaluated in actual cells to better understand their impact on impedance and high rate pulse requirements.

[0055] In Table 2, results from a continued gas generation experiment are shown as a percent of control. In general the Grillo zinc demonstrated much lower gassing rates, about 35% of Mitsui, and thus the additives had less impact when evaluated with the Grillo zinc.

TABLE-US-00002 TABLE 2 Additive % Gassing Rate of Ref. Zinc Tivida 10 ppm 100%  Grillo Epikure 20 ppm 59% Grillo Tomamine 20 ppm 59% Grillo Alkaterge T 100 ppm 55% Grillo Tivida 50 ppm 27% Mitsui Alkaterge T 20 ppm 22% Mitsui D-102 100 ppm 11% Mitsui Tomamine 100 ppm  5% Mitsui Epikure 100 ppm  0% Mitsui

[0056] This gas generation test was interpreted strictly as a screen with results sensitive to the zinc and with considerable test to test variation. The reported values represent the average of three tests per additive. While it is the goal to minimize zinc corrosion it should be understood that the most effective additives will most likely have a negative impact on cell impedance and high rate performance. Thus the goal is to find a zinc additive that meets the objective of reducing zinc corrosion while enabling cell performance.

Example 2

[0057] Referring to FIG. 3, SEM Images of Zinc Morphology are show. The surface morphology of the zinc is can be influenced by how the sample is prepared, handled, particle(s) chosen for magnification at 10 Kx, and storage time between preparation and characterization. Samples were prepared by first discharging 0.5 g of zinc at 100 mA for 3500 seconds followed by charging at 200 mA for 1750 seconds. The zinc was then washed three times in methanol and air dried. The images below suggest that sulfotricarballylates may well influence the surface morphology as the zinc with the sulfotricarballylates appears different than the control without surfactant.

Example 3

[0058] Since all of the additives demonstrated a reduction in zinc corrosion, they were all evaluated in AZ13 size air cells at a concentration of 40 ppm. This level was chosen at twice the typical level to magnify the impact on cell characteristics. It may be noted that the level of sulfotricarballylates in the following summaries may be shown at either 100 ppm or 50 ppm and 40 ppm or 20 ppm. The sulfotricarballylates supplied under the Tivida trade name was supplied in a carrier solvent at about 50% concentration.

[0059] Impedance results were summarized at two weeks of product age for true IR at 50 KHz impedance measured on a Quadtech instrument (See FIG. 4) as well as for polarization based on 40 Hz minus 50 KHz (See FIG. 5).

[0060] The 50 KHz impedance was overlapping for all surfactants except the controls, D102 and Carbowax 550, at the 40 ppm concentration level. The 50 KHz impedance also shows that a small change in concentration can have a significant impact on cell properties. The ideal surfactant would be one in which after the critical concentration required to protect the zinc surface was achieved the system would be robust to excess quantities. One reason that this is a difficult balance is that excess surfactant can alter the viscosity of the electrolyte and the rheology properties of the anode binder.

[0061] Perhaps more important than the cell resistance, is the polarization which is associated with film formation on the surface of the zinc and ion mobility. The difference between low frequency impedance linked to charge transfer and true resistance can be illustrated in a 40 Hz minus 50 KHz test.

[0062] In FIG. 5, the SHMP, Tivida, and Tomamine additives result in much lower charge transfer problems than either control D102 or mpeg 550 at the 40 ppm addition levels. If these films are not transient, one would expect the above trends to be observed in the close circuit voltage during product discharge.

Example 4

[0063] AZ13 size air cells were characterized on three application tests: 3 mA continuous, 3 mA background with a 12 mA pulse for 100 msec-IEC, and a 3 mA background with a 5 mA extended pulse for 15 minutes-wireless. Results are shown below in Table 3 in mAh, in order of worst to best performance. The Control is again an identical sample with no surfactant added. In FIG. 6, service to various functional end points are shown, with Tivida showing the best service, and always performing well above the control construction.

[0064] From this performance testing, some observations were made. The controls were never the best performing product. Tivida is statistically always one of the best performing additives. Based on the results of this screening process Tivida was selected for additional characterization and concentration optimization studies.

Example 5

[0065] AZ13 size air cells were prepared using conventional anode dry powder processing. In the cell builds, the Tivida concentration was varied from 10, 20, 50, and 100 ppm. A control cell using the D102 zinc additive was also prepared. The prepared air cells were characterized on two application tests: 3 mA background with a 12 mA pulse for 100 msec-IEC, and a 3 mA background with a 5 mA extended pulse for 15 minutes -wireless. Results are shown below in Table 4 in minutes service to various functional end points. The service data once again shows an advantage for Tivida over D102 by about 15% for wireless and about 10% for IEC. It also supports the conclusion that the cell is robust to excess surfactant which provides a wide window for formulations. Tivida can be added well above the monolayer concentration without having a negative impact on electrolyte viscosity or low frequency impedance. Higher concentrations may actually be beneficial perhaps increasing ZnO solubility, hydroxyl ion distribution in combination with the binder, and improving high rate performance.

TABLE-US-00003 TABLE 4 Wireless 1.1 v FEP IEC 1.0 V FEP 5 6 7 8 9 5 6 8 9 7 Control Tivida Tivida Tivida Tivida Control Tivida Tivida Tivida Tivida D102 10 ppm 20 ppm 50 ppm 100 ppm D102 10 ppm 50 ppm 100 ppm 20 ppm Lot Sol 2 Sol 2 Sol 2 Sol 2 Sol 2 Sol 2 Sol 2 Sol 2 Sol 2 Sol 2 130 144 136 125 166 189 200 214 208 231 141 152 177 155 158 222 230 222 228 224 111 130 142 180 158 214 206 229 222 232 133 152 153 158 150 223 204 204 222 229 141 161 164 147 164 187 228 232 226 213 150 152 166 142 169 168 222 227 222 227 Average 134.3 148.5 156.3 151.2 160.8 200.5 215.0 221.3 221.3 226.0 Stdev 13.4 10.5 15.6 18.3 6.9 22.5 13.2 10.6 7.0 7.0

[0066] While the invention has been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be affected by those skilled in the art without departing from the spirit of the invention. Accordingly, it is our intent to be limited only by the scope of the appending claims and not by way of the details and instrumentalities describing the embodiments shown herein.