阅读说明：本技术 具有增加的氧化锌水平的碱性电化学电池 (Alkaline electrochemical cell with increased zinc oxide levels ) 是由 罗伯特·P·约翰逊 罗伯特·E·雷二世 W·W·黄 Z·F·刘 史蒂芬·J·李默 于 2020-01-23 设计创作，主要内容包括：本发明提供了一种碱性电化学电池,其中,至少在游离电解质溶液中含有溶解的氧化锌或氢氧化锌,和/或阳极中含有固体氧化锌或氢氧化锌,以减缓在锌电极上形成氧化锌钝化层。此外,本发明还提供了一种碱性电化学电池的制备方法。(The invention provides an alkaline electrochemical cell in which at least the dissolved zinc oxide or zinc hydroxide is contained in the free electrolyte solution and/or the solid zinc oxide or zinc hydroxide is contained in the anode to slow the formation of a zinc oxide passivation layer on the zinc electrode. In addition, the invention also provides a preparation method of the alkaline electrochemical cell.)

1. An alkaline electrochemical cell, comprising:

a) a container; and

b) an electrode assembly disposed within the container, the electrode assembly including a cathode, an anode, a separator between the cathode and the anode, and a free electrolyte solution;

wherein the anode comprises 1) solid zinc and 2) solid zinc oxide or solid zinc hydroxide; and

wherein the free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide.

2. An alkaline electrochemical cell as claimed in claim 1 wherein the anode comprises solid zinc oxide and the free electrolyte solution comprises dissolved zinc oxide.

3. An alkaline electrochemical cell as claimed in claim 2 wherein the free electrolyte solution comprises greater than 2.0 wt% dissolved zinc oxide.

4. An alkaline electrochemical cell as claimed in claim 3 wherein the free electrolyte solution comprises about 4.0 to 6.5 wt% dissolved zinc oxide.

5. The alkaline electrochemical cell of any one of claims 1-4 wherein the anode comprises a gel electrolyte prepared by combining a gelling agent with a first aqueous alkaline electrolyte solution comprising an alkali metal hydroxide electrolyte and dissolved zinc oxide.

6. The alkaline electrochemical cell of claim 5 wherein the first aqueous alkaline electrolyte solution comprises greater than or equal to 2.5, ≧ 2.6, ≧ 2.7, ≧ 2.8, ≧ 2.9, ≧ 3.0, ≧ 3.1, ≧ 3.2, ≧ 3.3, ≧ 3.4, ≧ 3.5, ≧ 3.6, ≧ 3.7, ≧ 3.8, ≧ 3.9, or ≧ 4.0 percent by weight of dissolved zinc oxide.

7. The alkaline electrochemical cell of claim 6 wherein the first aqueous alkaline electrolyte solution comprises about 2.7-3.3 wt% dissolved zinc oxide.

8. The alkaline electrochemical cell of any one of claims 1-7 wherein the cathode comprises a second aqueous alkaline electrolyte solution comprising an alkali metal hydroxide electrolyte and dissolved zinc oxide.

9. The alkaline electrochemical cell of claim 8 wherein the second aqueous alkaline electrolyte solution comprises greater than or equal to 2.5, ≧ 2.6, ≧ 2.7, ≧ 2.8, ≧ 2.9, ≧ 3.0, ≧ 3.1, ≧ 3.2, ≧ 3.3, ≧ 3.4, ≧ 3.5, ≧ 3.6, ≧ 3.7, ≧ 3.8, ≧ 3.9, or ≧ 4.0 percent by weight of dissolved zinc oxide.

10. An alkaline electrochemical cell as claimed in claim 9 wherein the second aqueous alkaline electrolyte solution comprises about 2.5 to 4.0 wt% or about 2.7 to 3.3 wt% dissolved zinc oxide.

11. The alkaline electrochemical cell of any one of claims 8-10 wherein the first aqueous alkaline electrolyte solution and the second aqueous alkaline electrolyte solution are the same.

12. The alkaline electrochemical cell of any one of claims 1-11, wherein the total weight percent of dissolved zinc oxide in the full cell electrolyte solution of the electrochemical cell is about 1.5-4.5 wt%.

13. The alkaline electrochemical cell of any of claims 1-12, wherein the full cell electrolyte of the electrochemical cell is greater than 40% saturated with dissolved zinc oxide.

14. The alkaline electrochemical cell of any one of claims 1-13 wherein the solid zinc oxide or solid zinc hydroxide is substituted and comprises a cationic substituent or an anionic substituent, the substituted solid zinc oxide or substituted solid zinc hydroxide having a lower solubility than the unsubstituted solid zinc oxide or unsubstituted solid zinc hydroxide.

15. The alkaline electrochemical cell of claim 14 wherein the substituted solid zinc oxide has the formula Zn_1-xY_xO, wherein Y is at least one cationic substituent, and x is more than 0 and less than or equal to 0.50.

16. The alkaline electrochemical cell of claim 14 wherein the substituted solid zinc hydroxide has the formula Zn_1-xY_x(OH)₂Wherein Y is at least one cationic substituent, and x is more than 0 and less than or equal to 0.50.

17. The alkaline electrochemical cell of claim 14 wherein the substituted solid zinc oxide has the formula ZnO_{1- w}A_(2w/z)Wherein A is at least one anionic substituent, 0 < w.ltoreq.0.50, and z is the charge of the anionic substituent.

18. An alkaline electrochemical cell as claimed in claim 14 wherein the substituted solid zinc hydroxide has the formula zn (oh)_2-wA_(w/z)Wherein A is at least one anionic substituent, 0 < w.ltoreq.0.50, and z is the charge of the anionic substituent.

19. An alkaline electrochemical cell as claimed in claim 14 wherein the substituted solid zinc oxide has the formula Zn_{1- x}Y_xO_1-w(OH)_2wWherein Y is at least one cationic substituent, x is more than 0 and less than or equal to 0.50, and w is more than 0 and less than or equal to 0.50.

20. An alkaline electrochemical cell as claimed in claim 14 wherein the substituted solid zinc oxide is a cationic and anionic substituted mixed oxide hydroxide having the formula Zn_1-xY_xO_1-w-t(OH)_2wA_(2t/z)Wherein Y is at least one cationic substituent, 0<x is less than or equal to 0.50, A is at least oneAnionic substituent, 0<w≤0.50，0<t is less than or equal to 0.50, and z is the charge of the anionic substituent.

21. The alkaline electrochemical cell of any one of claims 14-16, 19 and 20 wherein the cationic substituent is selected from Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, Sr, or any combination thereof.

22. An alkaline electrochemical cell as claimed in any one of claims 14, 17, 18 and 20 wherein the anionic substituent group is selected from CO₃ ^2-、PO₄ ^3-Or a combination thereof.

23. An alkaline electrochemical cell as claimed in claim 2 wherein the anode comprises about 0.2 to 5 volume percent solid zinc oxide based on the total volume of the anode.

24. An alkaline electrochemical cell as claimed in claim 23 wherein the anode comprises about 0.3 to 1.5 volume percent solid zinc oxide based on the total volume of the anode.

25. An alkaline electrochemical cell as claimed in claim 23 wherein the anode comprises about 0.66 volume percent solid zinc oxide based on the total volume of the anode.

26. An alkaline electrochemical cell as claimed in claim 2 wherein the alkaline electrochemical cell comprises about 3.0 to 8.8 wt% total zinc oxide.

27. An alkaline electrochemical cell as claimed in claim 26 wherein the alkaline electrochemical cell comprises greater than about 7.0 wt% total zinc oxide.

28. An alkaline electrochemical cell as claimed in claim 26 wherein the alkaline electrochemical cell comprises about 4.75 wt% total zinc oxide.

29. An alkaline electrochemical cell as claimed in claim 2 wherein the electrolyte concentration percentage of the anode is between about 16.0% and about 30.0%.

30. An alkaline electrochemical cell as claimed in claim 29 wherein the anode has an electrolyte concentration percentage of about 18.0 to about 22.0%.

31. An alkaline electrochemical cell as claimed in claim 2 wherein the percent electrolyte concentration of the anode is less than about 22.0%.

32. An alkaline electrochemical cell as claimed in claim 1, wherein the full cell electrolyte concentration is between about 26.0 and 30.0%.

33. An alkaline electrochemical cell as claimed in claim 32, wherein the full cell electrolyte concentration is less than 29.0%.

34. An alkaline electrochemical cell as claimed in any one of claims 1 to 33 wherein the total cell saturation of the zinc oxide or hydroxide is at least about 40%.

35. An alkaline electrochemical cell as claimed in claim 34 wherein the total cell saturation of the zinc oxide or hydroxide is at least about 40-125%.

36. An alkaline electrochemical cell as claimed in claim 34 wherein the total cell saturation of the zinc oxide or hydroxide is between about 40% and 125%.

37. The alkaline electrochemical cell of any one of claims 1-36 wherein the electrochemical cell is a primary cell.

38. The alkaline electrochemical cell of any one of claims 1-36 wherein the electrochemical cell is a secondary battery.

39. The alkaline electrochemical cell of any one of claims 1-38 wherein the free electrolyte solution comprises potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), magnesium hydroxide (mg (oh)₂) Calcium hydroxide (Ca (OH)₂) Magnesium perchlorate (Mg (ClO)₄)₂) Magnesium chloride (MgCl)₂) Or magnesium bromide (MgBr)₂)。

40. The alkaline electrochemical cell of any one of claims 1-39 wherein the specific capacity or run time of the alkaline electrochemical cell is greater than the specific capacity or run time of an alkaline electrochemical cell lacking dissolved zinc oxide in free electrolyte.

41. An alkaline electrochemical cell as claimed in claim 40 wherein the specific capacity or run time is from greater than 1% to greater than 100%, or from greater than 5% to greater than 90%, or from greater than 10% to greater than 80%, or from greater than 15% to greater than 70%, or from greater than 20% to greater than 60%, or from greater than 25% to greater than 50%, or from greater than 30% to greater than 40%.

42. The alkaline electrochemical cell of any one of claims 1-41 wherein the voltage of the cell is 0.1V-2.0V, 0.2V-1.9V, 0.3V-1.8V, 0.4V-1.7V, 0.5V-1.6V, 0.6V-1.5V, 0.7V-1.4V, 0.8V-1.3V, 0.9V-1.2V, 1.0V-1.1V, or 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, 1.5V, 1.6V, 1.7V, 1.8V, 1.9V, or 2V, 0V.

Technical Field

Alkaline electrochemical cells are commercially available, and cell sizes are typically LR6(AA), LR03(AAA), LR14(C), and LR20 (D). Alkaline electrochemistry is cylindrical in shape and must meet dimensional standards set by the organization of the international electrotechnical commission, etc. Consumers use electrochemical cells to power a variety of electronic devices, such as clocks, radios, toys, electronic games, motion picture cameras including flash light assemblies, and digital cameras. These electronic devices have a wide range of discharge conditions, such as from low discharge to high discharge. As the use of high discharge devices, such as digital cameras, increases, it is desirable for manufacturers to be able to produce batteries with high discharge characteristics.

Because the shape and size of the battery is generally fixed, battery manufacturers must change battery characteristics to provide improved performance. In order to solve the problem of how to improve the performance of a battery in a specific device (such as a digital camera), it is generally necessary to change the internal structure of the battery. For example, the battery structure is changed by increasing the amount of active material used within the battery.

Zinc (Zn) is a well-known substance commonly used as an anode active material in electrochemical cells such as dry cells. During discharge of the electrochemical cell, zinc is oxidized to form zinc oxide (ZnO). The oxidation reaction products of zinc form a passivation layer that inhibits the effective discharge of the remaining zinc, reducing battery performance.

Embodiments of the present invention aim to overcome the limitations of the related batteries described above.

Disclosure of Invention

One embodiment of the present invention provides an alkaline electrochemical cell comprising:

a) a container; and

b) an electrode assembly disposed within the container, the electrode assembly including a cathode, an anode, a separator between the cathode and the anode, and a free electrolyte solution;

wherein the anode comprises 1) solid zinc and 2) solid zinc oxide or solid zinc hydroxide; and

wherein the free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide.

Drawings

Fig. 1 is a schematic cross-sectional view of one embodiment of an alkaline electrochemical cell of the present invention.

Fig. 2A and 2B are photographs of a control anode and an anode described according to an embodiment of the present application, respectively.

Fig. 3A and 3B are close-ups of the photographs in fig. 2A and 2B, respectively.

Detailed Description

Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, various embodiments of the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided in the specification solely for the purpose of satisfying the applicable legal requirements of the application, wherein like reference numerals refer to like elements throughout.

In the following description, various elements may be identified as having particular values or parameters, however, these terms are merely exemplary. Indeed, the exemplary embodiments do not limit the various aspects and concepts of the embodiments, as many comparable parameters, sizes, ranges, and/or values may be implemented. The terms "first," "second," "primary," "exemplary," "secondary," and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Furthermore, the terms "a," "an," and "the" do not denote a limitation of quantity, but rather denote the presence of "at least one" of the referenced term.

Each embodiment disclosed in this specification is applicable to each of the other embodiments disclosed. All combinations and subcombinations of the various elements described in this specification are within the scope of the embodiments.

It is understood that where parameter ranges are provided, all integers and ranges within the ranges and tenths and hundredths thereof are also provided by the embodiments. For example, "5-10%" includes: 5%, 6%, 7%, 8%, 9% and 10%; 5.0%, 5.1%, 5.2%. 9.8%, 9.9%, and 10.0%; 5.00%, 5.01%, 5.02%. 9.98%, 9.99%, and 10.00%, and 6-9%, 5.1% -9.9%, and 5.01% -9.99%.

As used in this specification, "about" in the context of a numerical value or range means within ± 10% of the stated or claimed numerical value or range.

As used herein, "full cell electrolyte mass" refers to the total mass of electrolyte in the battery, and "full cell electrolyte concentration" refers to the total concentration of electrolyte in the battery. The full cell electrolyte concentration can be calculated as (full cell electrolyte mass)/(full cell electrolyte mass + total water mass in the cell) multiplied by 100 (if expressed in percentage). The total additive weight percentage in the full cell electrolyte solution can be determined by calculation as (total mass of additive in cell)/(total mass of additive in cell + full cell electrolyte mass + total water mass in cell) X100.

The "total weight percent" of the zinc compound or part thereof in the battery in the present specification means: the ratio of the total weight of the zinc compound to the total mass or weight of the zinc compound, electrolyte and water in the cell or a portion thereof. For example, the "total zinc oxide weight percentage" of the battery is calculated as (zinc oxide mass)/(zinc oxide mass + electrolyte mass + water mass) X100%.

The "total dissolved zinc oxide weight percent" in the full cell electrolyte was calculated as (mass of dissolved zinc oxide in the cell)/(mass of dissolved zinc oxide in the cell + mass of electrolyte in the cell + mass of water in the cell) X100%, this measurement did not take into account the mass of solid (i.e., undissolved) zinc oxide in the anode.

In this specification, "electrolyte concentration percentage" of an electrode means: the ratio of the total weight of electrolyte in the electrode to the total weight of electrolyte and water in the electrode. For example, "weight percentage of KOH" for an electrode is calculated as (mass of KOH in the electrode)/(mass of KOH in the electrode + mass of water in the electrode) X100%.

In the present specification, "improvement" in the specific capacity means an increase in the specific capacity. In general, an "improvement" in a performance or performance index of a material or electrochemical cell means that the performance or performance index is different than the performance or index of a different material or electrochemical cell, such that the user or manufacturer of the material or cell deems it desirable (e.g., lower cost, longer duration, more power provided, more durable, easier or faster manufacturing, etc.).

In the present specification, the "specific capacity" means: the total amount of charge in an electrochemical cell, when discharged at a particular rate, is typically measured in amp-hours.

In the present specification, "run time" means: the length of time that the electrochemical cell is capable of providing a level of charge.

In this specification, describing a solution as "X% saturated with solute" means: under the same conditions of temperature, pressure, etc., the solution contains a maximum amount of solute that can be dissolved in the solution of X%, taking into account all other components of the solution (e.g., dissolved electrolyte).

Describing an electrochemical cell as having "X% total cell saturation" of compounds takes into account compounds dissolved in the free electrolyte solution and compounds present in the anode. For example, in calculating the total cell saturation of zinc oxide for an electrochemical cell, the amount of zinc oxide dissolved in the free electrolyte solution, as well as the amount of solid and dissolved zinc oxide in the anode, may result in a total cell saturation percentage of over 100%.

In the present specification, "zinc ion source" means: produce zinc ions (Zn (OH) when placed in solution₄ ^2-) Non-limiting examples of any of the compounds of (1) include Zn, zinc oxide (ZnO), and zinc hydroxide (Zn (OH)₂). In one embodiment of the invention, the zinc ion source may refer to ZnO and Zn (OH) only₂。

One embodiment of the present invention provides an alkaline electrochemical cell comprising:

a) a container; and

b) an electrode assembly disposed within the container, the electrode assembly including a cathode, an anode, a separator between the cathode and the anode, and a free electrolyte solution;

wherein the anode comprises 1) solid zinc and 2) solid zinc oxide or solid zinc hydroxide; and

wherein the free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide.

According to one embodiment of the invention, the anode comprises solid zinc oxide and the free electrolyte solution comprises dissolved zinc oxide.

According to one embodiment of the invention, the free electrolyte solution comprises more than 2.0 wt% dissolved zinc oxide. According to another embodiment of the invention, the free electrolyte solution comprises about 4.0-6.5 wt% dissolved zinc oxide.

According to one embodiment of the invention, the anode comprises a gel electrolyte, wherein the gel electrolyte is prepared by combining a gelling agent with a first aqueous alkaline electrolyte solution, wherein the first aqueous alkaline electrolyte solution comprises an alkali metal hydroxide electrolyte and dissolved zinc oxide. According to one embodiment of the present invention, the first aqueous alkaline electrolyte solution includes greater than or equal to 2.5, ≧ 2.6, ≧ 2.7, ≧ 2.8, ≧ 2.9, ≧ 3.0, ≧ 3.1, ≧ 3.2, ≧ 3.3, ≧ 3.4, ≧ 3.5, ≧ 3.6, ≧ 3.7, ≧ 3.8, ≧ 3.9, or ≧ 4.0 by weight percentage. According to one embodiment of the invention, the first aqueous alkaline electrolyte solution comprises about 2.7-3.3 wt% dissolved zinc oxide.

According to one embodiment of the invention, the cathode comprises a second aqueous alkaline electrolyte solution, wherein the second aqueous alkaline electrolyte solution comprises an alkali metal hydroxide electrolyte and dissolved zinc oxide. According to one embodiment of the present invention, the second aqueous alkaline electrolyte solution includes greater than or equal to 2.5, ≧ 2.6, ≧ 2.7, ≧ 2.8, ≧ 2.9, ≧ 3.0, ≧ 3.1, ≧ 3.2, ≧ 3.3, ≧ 3.4, ≧ 3.5, ≧ 3.6, ≧ 3.7, ≧ 3.8, ≧ 3.9, or ≧ 4.0 by weight percentage. According to one embodiment of the invention, the second aqueous alkaline electrolyte solution comprises about 2.5-4.0 wt% or about 2.7-3.3 wt% dissolved zinc oxide.

According to one embodiment of the invention, the first aqueous alkaline electrolyte solution and the second aqueous alkaline electrolyte solution are identical.

According to one embodiment of the present invention, the total weight percent of dissolved zinc oxide in the full cell electrolyte solution of the electrochemical cell is between about 1.5 and 4.5 weight percent. According to one embodiment of the present invention, the total weight percent of zinc oxide in the full cell electrolyte solution of the electrochemical cell is between about 2.0 and 4.0 or between about 2.5 and 3.5 weight percent. According to one embodiment of the present invention, the total weight percent of zinc oxide in the full cell electrolyte solution of the electrochemical cell is greater than about 4.5 weight percent. According to one embodiment of the present invention, the total weight percent of zinc oxide in the full cell electrolyte solution of the electrochemical cell is between about 0.5 weight percent and about 4.5 weight percent, or between about 0.5 weight percent and about 3.0 weight percent, or between about 0.5 weight percent and about 2.0 weight percent.

According to one embodiment of the invention, the full cell electrolyte of the electrochemical cell is greater than 40% saturated with dissolved zinc oxide.

According to one embodiment of the invention, the solid zinc oxide or solid zinc hydroxide is a substituted solid zinc oxide which is substituted and comprises a cationic substituent or an anionic substituent, wherein the substituted solid zinc oxide or substituted solid zinc hydroxide is more difficult to dissolve than the unsubstituted solid zinc oxide or unsubstituted solid zinc hydroxide.

According to one embodiment of the invention, a substituted solid zinc oxide articleHaving the formula Zn_1-xY_xO, wherein Y is at least one cationic substituent, and 0<x≤0.50。

According to one embodiment of the invention, the substituted solid zinc hydroxide has the formula Zn_1-xY_x(OH)₂Wherein Y is at least one cationic substituent, and 0<x≤0.50。

According to one embodiment of the invention, the substituted solid zinc oxide has the formula ZnO_1-wA_(2w/z)Wherein A is at least one anionic substituent, 0 < w.ltoreq.0.50, and z is the charge of the anionic substituent.

According to one embodiment of the invention, the substituted solid zinc hydroxide has the formula Zn (OH)_2-wA_(w/z)Wherein A is at least one anionic substituent, 0<w.ltoreq.0.50, z is the charge of the anionic substituent.

According to one embodiment of the invention, the substituted solid zinc oxide has the formula Zn_1-xY_xO_1-w(OH)_2wWherein Y is at least one cationic substituent, 0<x≤0.50，0<w≤0.50。

According to one embodiment of the invention, the substituted solid zinc oxide is a cationic substituted and anionic substituted mixed oxide hydroxide. According to one embodiment of the invention, the cation-substituted and anion-substituted mixed oxide hydroxides have Zn_1-xY_xO_1-w-t(OH)_2wA_(2t/z)Wherein Y is at least one cationic substituent, 0<x is 0.50, wherein A is at least one anionic substituent, 0<w≤0.50，0<t.ltoreq.0.50 and z is the charge of the anionic substituent.

According to an embodiment of the invention, the cationic substituent is selected from Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, Sr or any combination thereof.

According to one embodiment of the invention, the anionic substituent is selected from CO₃ ^2-、PO₄ ^3-Or a combination thereof.

According to one embodiment of the invention, the anode comprises about 0.2 to 5 volume percent solid zinc oxide, based on the total volume of the anode. According to one embodiment of the invention, the anode comprises about 0.3 to 1.5 volume percent solid zinc oxide, based on the total volume of the anode. According to one embodiment of the invention, the anode comprises about 0.66 volume percent solid zinc oxide based on the total volume of the anode.

According to one embodiment of the invention, the alkaline electrochemical cell comprises a total zinc oxide weight percent of about 3.0-8.8%. According to one embodiment of the invention, an alkaline electrochemical cell comprises a total zinc oxide weight percent of about 3.0-4.0%, about 4.0-5.0%, about 5.0-6.0%, about 6.0-7.0%, about 7.0-8.0%, about 8.0-9.0%. According to one embodiment of the invention, the alkaline electrochemical cell comprises greater than about 3.0% total zinc oxide weight percent. According to one embodiment of the invention, the alkaline electrochemical cell comprises a total zinc oxide weight percentage of greater than or equal to about 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%. According to one embodiment of the invention, the alkaline electrochemical cell comprises about 4.75% total zinc oxide weight percent.

According to one embodiment of the invention, the electrolyte concentration percentage of the anode is about 16.0-30.0%. According to one embodiment of the invention, the electrolyte concentration percentage of the anode is about 18.0-22.0%. According to one embodiment of the invention, the percent electrolyte concentration of the anode is less than about 22.0%.

According to one embodiment of the invention, the full cell electrolyte concentration is about 26.0-30.0%. According to one embodiment of the invention, the full cell electrolyte concentration is less than 29.0%.

According to one embodiment of the invention, the total cell saturation of the zinc oxide or zinc hydroxide is at least about 40%. According to one embodiment of the invention, the total cell saturation of the zinc oxide or hydroxide is at least about 40-125%. According to one embodiment of the invention, the total cell saturation of the zinc oxide or hydroxide is about 40-125%. According to one embodiment of the invention, the total cell saturation of the zinc oxide or zinc hydroxide is at least about 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, or 125%.

According to one embodiment of the invention, the electrochemical cell is a galvanic cell. According to other embodiments of the invention, the electrochemical cell is a secondary battery.

According to one embodiment of the invention, the free electrolyte solution comprises potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), magnesium hydroxide (Mg (OH)₂) Calcium hydroxide (Ca (OH)₂) Magnesium perchlorate (Mg (ClO)₄)₂) Magnesium chloride (MgCl)₂) Or magnesium bromide (MgBr)₂)。

According to one embodiment of the invention, the specific capacity or run time of an alkaline electrochemical cell is greater than the specific capacity or run time of a similar alkaline electrochemical cell lacking dissolved zinc oxide in the free electrolyte. According to one embodiment of the invention, the specific capacity or run time is greater than 1% to greater than 100%, or greater than 5% to greater than 90%, or greater than 10% to greater than 80%, or greater than 15% to greater than 70%, or greater than 20% to greater than 60%, or greater than 25% to greater than 50%, or greater than 30% to greater than 40%.

According to one embodiment of the invention, the voltage of the battery is 0.1V-2.0V, 0.2V-1.9V, 0.3V-1.8V, 0.4V-1.7V, 0.5V-1.6V, 0.6V-1.5V, 0.7V-1.4V, 0.8V-1.3V, 0.9V-1.2V, 1.0V-1.1V, or 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, 1.5V, 1.6V, 1.7V, 1.8V, 1.9V or 2.0V.

Various embodiments of the present invention will be described in detail with reference to fig. 1, which is a schematic cross-sectional view of a cylindrical battery 1 having a nail or bobbin type structure having dimensions comparable to those of a conventional LR6(AA) alkaline battery, which is particularly suitable for the embodiment. However, it should be understood that the cell may have other sizes and shapes (e.g., prismatic or button shaped) and electrode configurations according to other embodiments of the present invention, as known to those skilled in the art. The materials and design of the electrochemical cell element shown in fig. 1 are for illustrative purposes only and other materials and designs may be substituted. Further, in some embodiments of the invention, the cathode and anode materials may be coated onto the surface of the separator and/or current collector and rolled to form a "rolled" structure.

The electrochemical cell 1 shown in fig. 1 includes a container 10, the container 10 having a closed bottom end 24, a top end 22, and a sidewall 26 therebetween. The closed bottom end 24 includes a terminal cover 20 having a protrusion. The container 10 has an inner wall 16. In the embodiment shown in fig. 1, the positive terminal cover 20 is welded or otherwise attached to the bottom end 24. In one embodiment of the present invention, the terminal cover 20 may be formed of plated steel, with a protrusion in a central region thereof. The container 10 may be formed of a metal, such as steel, preferably plated with nickel, cobalt and/or other metals or alloys, or other materials, having sufficient structural characteristics to be compatible with the various inputs of the electrochemical cell. The label 28 may be formed around the outer surface of the container 10 and may be formed on the peripheral edges of the positive terminal cover 20 and the negative terminal cover 46 as long as the negative terminal cover 46 is electrically insulated from the container 10 and the positive terminal 20.

A first electrode 18 and a second electrode 12 are disposed within the container 10 with a separator 14 between the first electrode 18 and the second electrode 12. The first electrode 18 is disposed within the space defined by the separator 14 secured to the open end 22 of the container 10 and the closure assembly 40. The closed end 24, the side wall 26 and the closure assembly 40 define a cavity for receiving the electrodes of the cell.

The closure assembly 40 includes a closure member 42 (e.g., a gasket), a current collector 44, and a conductive terminal 46 in electrical contact with the current collector 44. The closure 42 preferably contains a pressure relief vent that allows the closure 42 to rupture if the internal pressure of the cell becomes excessive. The closure member 42 may be formed of a polymeric or elastomeric material (e.g., nylon-6, 6 or nylon-6, 12), may be formed of an injection molded polymer blend (e.g., a polypropylene matrix combined with polyphenylene ether or polystyrene), or other material (e.g., metal) so long as the current collector 44 and conductive terminal 46 are electrically insulated from the container 10 which serves as the current collector for the second electrode 12. In the illustrated embodiment, current collector 44 is an elongated spike-type, spool-type element. Current collector 44 is made of a metal or metal alloy, such as copper or brass, a conductive plated metal or plastic current collector, or the like, but may be made of other suitable materials. The current collector 44 is inserted through a hole in the closure member 42, preferably located in the center of the closure member 42.

The first electrode 18 is preferably a negative electrode or an anode. The negative electrode includes a mixture of zinc (as an active material), a conductive material, solid zinc oxide, and a surfactant. The negative electrode may optionally include other additives, such as a binder or gelling agent. Preferably, the volume of active material used in the negative electrode is sufficient to maintain the desired particle-to-particle contact and the desired anode-to-cathode (A: C) ratio.

The particles should be kept in contact with the particles during the service life of the battery. If the volume of active material in the negative electrode is too low, the voltage of the battery may suddenly drop to an unacceptably low value when the battery is powering a device. The voltage drop is believed to be caused by a loss of continuity in the conductive matrix of the negative electrode. The conductive matrix may be formed from undischarged active material particles, conductive electrochemically formed oxides, or a combination thereof. After the oxide begins to form, but before a sufficient network is established to bridge all the active material particles present, a voltage drop may occur.

Zinc suitable for use in embodiments of the present invention may be obtained from a number of different commercial sources, such as BIA 100, BIA 115, under various names. Dimore s.a., Brussels, Belgium is an example of a zinc supplier. According to a preferred embodiment of the invention, the zinc powder typically has 25% to 40% fines less than 75 μm, preferably 28% to 38% fines less than 75 μm. Generally, a lower percentage of fines will not achieve the desired DSC service, and the use of a higher percentage of fines will result in increased outgassing. The correct zinc alloy is required to reduce the cathode gassing of the cell and maintain the test results.

The negative electrode contains a nonionic surfactant or an anionic surfactant or a combination thereof. According to one embodiment of the invention, the surfactant is a phosphate ester surfactant. It has been found that by adding solid zinc oxide alone, the anode resistance increases during discharge, but decreases by the addition of surfactant. As described above, the addition of the surfactant increases the surface charge density of the solid zinc oxide and lowers the anode resistance. The use of a surfactant is believed to contribute to the formation of a more porous discharge product when the surfactant is adsorbed on the solid zinc oxide. Anionic surfactants have a negative charge and in alkaline solutions, surfactants adsorbed on the surface of solid zinc oxide are believed to alter the surface charge density of the surface of the solid zinc oxide particles. It is believed that the adsorbed surfactant causes repulsive electrostatic interactions between the solid zinc oxide particles. It is believed that the surfactant reduces the increase in anode resistance caused by the addition of the solid zinc oxide because the adsorbed surfactant on the solid zinc oxide results in an increase in the surface charge density at the surface of the solid zinc oxide particles. The larger the BET surface area of the solid zinc oxide, the more surfactant can be adsorbed on the surface of the solid zinc oxide. According to one embodiment of the present invention, the concentration of the surfactant is about 5 to 50ppm with respect to the electrode active material. According to one embodiment of the invention, the concentration of the surfactant is about 10-20 ppm.

According to one embodiment of the invention, the negative electrode comprises about 0.2 to 5 wt% of solid zinc oxide, based on the total weight of the negative electrode. According to one embodiment of the invention, the negative electrode comprises about 1 to 4 wt% solid zinc oxide. According to a preferred embodiment of the invention, the negative electrode comprises about 0.3 to 1 wt% of solid zinc oxide. According to a more preferred embodiment of the invention, the negative electrode comprises about 0.66 wt% of solid zinc oxide.

According to one embodiment of the invention, the solid zinc oxide is substituted to reduce its solubility. According to one embodiment of the invention, a portion of the zinc in the solid zinc oxide is replaced by another cation. According to one embodiment of the invention, the substituted solid zinc oxide has the formula Zn_1-xY_xO, wherein Y is at least one cationic substituent, and x is more than 0 and less than or equal to 0.50. According to an embodiment of the invention, the cationic substituent is selected from Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, Sr or any combination thereof. According to one embodiment of the invention, x is 0.01 to 0.40, or 0.02 to 0.35, or 0.4 to 0.30, or 0.05 to 0.25, or 0.10 to 0.20. According to one embodiment of the present invention, x ≧ 0.01, ≧ 0.02, ≧ 0.04, ≧ 0.06, ≧ 0.08, ≧ 0.10, ≧ 0.12, ≧ 0.14, ≧ 0.16, ≧ 0.18, or ≧ 020, 0.25, 0.3, 0.35 or 0.40.

According to one embodiment of the invention, a portion of the oxygen in the solid zinc oxide is replaced by another anion. According to one embodiment of the invention, the substituted solid zinc oxide has the formula ZnO_1-wA_(2w/z)Wherein A is at least one anionic substituent, 0 < w.ltoreq.0.50, and z is the charge of the anionic substituent. According to one embodiment of the invention, the anionic substituent is selected from CO₃ ^2-、PO₄ ^3-Or a combination thereof. According to one embodiment of the invention w is 0.01-0.40, or 0.02-0.35, or 0.4-0.30, or 0.05-0.25, or 0.10-0.20. According to one embodiment of the present invention, w is ≧ 0.01, ≧ 0.02, ≧ 0.04, ≧ 0.06, ≧ 0.08, ≧ 0.10, ≧ 0.12, ≧ 0.14, ≧ 0.16, ≧ 0.18, ≧ 0.20, ≧ 0.25, ≧ 0.30, ≧ 0.35 or ≧ 0.40. According to one embodiment of the invention, the solid zinc oxide contains cationic and anionic substituents.

The aqueous alkaline electrolyte solution (or simply "aqueous electrolyte solution") comprises an alkali metal hydroxide, such as potassium hydroxide (KOH), sodium hydroxide (NaOH), or mixtures thereof, preferably potassium hydroxide. The alkaline electrolyte used to form the gel electrolyte of the negative electrode comprises about 16 to about 36 weight percent, such as about 16 to about 28 weight percent, specifically about 18 to about 22 weight percent, or about 20 weight percent of alkali metal hydroxide, based on the total weight of the alkaline electrolyte solution. According to one embodiment of the invention, the alkali metal hydroxide is present in an amount of 16 to 36 wt.%. According to one embodiment of the invention, the weight percentage of alkali metal hydroxide is greater than or equal to 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or 36. According to one embodiment of the invention, the weight percentage of alkali metal hydroxide is less than or equal to 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or 36. According to one embodiment of the invention, the weight percentage of alkali metal hydroxide is equal to about 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or 36.

The aqueous alkaline electrolyte solution also includes about 1.5 to 4 wt% of dissolved zinc oxide, based on the total weight of the aqueous alkaline electrolyte solution.

As is well known in the art, it is preferred to use a gelling agent, such as a crosslinked polyacrylic acid (e.g., available from Noveon, Inc., cleveland, ohio) in the negative electrode940). Carboxymethylcellulose, polyacrylamide and sodium polyacrylate are other gelling agents suitable for use in alkaline electrolyte solutions. The gelling agent is desirable to maintain a uniform dispersion of the zinc and solid zinc oxide particles in the negative electrode. The amount of gelling agent present is selected so that a lower electrolyte separation rate is obtained and the anode viscosity in yield stress is not too great, which can lead to anode dispensing problems.

Dissolved zinc oxide is present in the anode, preferably by dissolving in an aqueous electrolyte solution, to improve plating on a spool-type or nail-type current collector, reducing the negative electrode lay-aside gassing. The dissolved zinc oxide added is separate and distinct from the solid zinc oxide present in the anode composition. According to an embodiment of the present invention, the content of the dissolved zinc oxide is preferably 3 to 4 wt% based on the total weight of the negative electrode electrolyte solution. According to one embodiment of the invention, the dissolved zinc oxide in the negative electrode electrolyte solution is greater than 3 wt%. The BET surface area of the soluble or dissolved zinc oxide is typically about 4 square meters per gram or less, as measured using a Tristar 3000BET specific surface area analyzer with multipoint calibration from Micrometrics after degassing the zinc oxide at 150 ℃ for about one hour; its particle size D50 (mean diameter) was about 1 micron as measured using a CILAS particle size analyzer as indicated above.

Other components may optionally be included in the negative electrode, including but not limited to: gassing inhibitors, organic or inorganic preservatives, plating agents, adhesives or other surfactants. Examples of gassing inhibitors or corrosion inhibitors include: indium salts (e.g., indium hydroxide), perfluoroalkyl ammonium salts, alkali metal sulfides, and the like. According to a preferred embodiment of the present invention, the sodium silicate is included in an amount of about 0.3 wt% based on the total weight of the negative electrode electrolyte to substantially prevent the battery from being short-circuited through the separator during the discharge of the battery.

The negative electrode can be formed in a number of different ways, as is known in the art. For example, the negative electrode components may be dry mixed and added to the cell, the alkaline electrolyte added alone, or according to a preferred embodiment of the invention, a pre-gelled negative electrode process is utilized.

According to one embodiment of the invention, the zinc and solid zinc oxide powders and optionally other powders other than the gelling agent are combined and mixed. The surfactant is then introduced into the mixture containing zinc and solid zinc oxide. The pre-gel comprising the alkaline electrolyte solution, soluble zinc oxide and gelling agent and optionally other liquid components is introduced into a mixture of surfactant, zinc and solid zinc oxide, which is further mixed to obtain a substantially homogeneous mixture before being added to the cell. Alternatively, according to a preferred embodiment of the invention, the solid zinc oxide is pre-dispersed in a negative electrode pre-gel comprising an alkaline electrolyte, a gelling agent, soluble zinc oxide and other desired liquids and mixed for about 15 minutes. Then, solid zinc oxide and surfactant are added and the negative electrode is mixed for an additional period of time, such as about 20 minutes. The content of the gel electrolyte used in the anode is generally about 25 to about 35 wt%, such as about 32 wt%, based on the total weight of the anode. The volume percent of the gel electrolyte may be about 70% based on the total volume of the negative electrode.

In addition to the aqueous alkaline electrolyte absorbed by the gelling agent during the manufacture of the negative electrode, additional aqueous alkali metal hydroxide solution, i.e., "free electrolyte," is added to the cell during the manufacture. The free electrolyte may be incorporated into the cell by placing the free electrolyte in a cavity defined by the positive or negative electrode, or a combination thereof. The method used to incorporate the free electrolyte into the cell is not critical as long as it is in contact with the negative electrode, positive electrode and separator. According to one embodiment of the invention, the free electrolyte is added both before and after the addition of the negative electrode mixture. According to one embodiment of the invention, about 0.97 grams of a 34 wt% KOH solution was added as free electrolyte to an LR6 type cell and about 0.87 grams was added to the cavity provided with the separator prior to insertion of the negative electrode. After the negative electrode was inserted, the remaining portion of 34 wt% KOH solution was injected into the cavity provided with the separator. The free electrolyte solution contains about 0.01-6.0 wt% dissolved zinc oxide. According to an embodiment of the invention, the free electrolyte solution contains greater than, less than, or equal to about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.5, 5.5.5, 5.5.5.5, 5.5.5.5.5, 5, 5.5.5, 5.5.5.5, 5, 5.5.5, 5.5.5.5.5.5.5.6, 5.5.5.5.6, 5.5.7, or more by weight percent of zinc oxide. According to a preferred embodiment of the invention, the free electrolyte solution contains about 4.0-6.0 wt% dissolved zinc oxide. The saturation of the free electrolyte solution with dissolved zinc oxide may be greater than or equal to about 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%.

The second electrode 12, also referred to herein as the positive electrode or the cathode, includes an electrochemically active material. Electrolytic Manganese Dioxide (EMD) is a commonly used electrochemically active material, and is generally present in an amount of about 80 to 92 wt%, preferably about 86 to 92 wt%, based on the total weight of the cathode, i.e., EMD, conductive material, cathode electrolyte, and additives (including organic additives, if present). The positive electrode is formed by combining and mixing the desired components of the electrodes, dispensing a quantity of the mixture into the open end of the container, using a ram to mold the mixture into a solid tubular structure that forms a cavity within the container, and the separator 14 and first electrode 18 are then disposed in the cavity. As shown in fig. 1, the second electrode 12 has a flange 30 and an inner surface 32. Alternatively, the positive electrode may be formed by pre-forming a plurality of rings from a mixture comprising EMD and optional additives, and then inserting the rings into a container to form a tubular second electrode. The cell shown in fig. 1 typically comprises 3 or 4 rings.

The positive electrode can include other components, such as a conductive material (e.g., graphite) that provides a conductive matrix that substantially penetrates the positive electrode when mixed with the EMD. The conductive material may be natural (i.e., mined) or synthetic (i.e., manufactured). According to one embodiment of the invention, the ratio of active material or oxide to carbon (O: C ratio) in the positive electrode of the battery is from about 12 to about 14. Too high an oxide to carbon ratio reduces the resistance of the container to the cathode, affects overall cell resistance, and may potentially affect high speed testing (e.g., DSC testing) or higher cut-off voltages. Further, the graphite may be expanded or unexpanded. Graphite suppliers for alkaline batteries include: timca America corporation (Timcal America), westerlet, ohio, advanced Graphite corporation, chicago, illinois, and longsha limited, basel, switzerland (Lonza, Ltd.). The conductive material is typically present in an amount of about 5 to about 10 wt%, based on the total weight of the positive electrode. Too much graphite will reduce the EMD input, thereby reducing the battery capacity; too little graphite may increase the contact resistance of the container with the cathode and/or the cathode resistance. An example of an additional additive is barium sulfate (BaSO)₄) Commercially available from barrio E de rivatii s.p.a. of massa, italy. The barium sulfate is typically present in an amount of about 1 to about 2 wt%, based on the total weight of the positive electrode. Other additives may include barium acetate, titanium dioxide, binders such as diacetylene and calcium stearate.

According to one embodiment of the present invention, a positive electrode component (such as EMD), a conductive material, and barium sulfate and optionally one or more additives are mixed together to form a homogeneous mixture. During mixing, an alkaline electrolyte solution (e.g., about 37% to about 40% KOH solution) and optionally one or more organic additives are uniformly dispersed into the mixture to ensure uniform distribution of the solution throughout the positive electrode material. According to one embodiment of the invention, the alkaline electrolyte solution used to form the cathode contains dissolved zinc oxide in any amount up to saturation with dissolved zinc oxide. The mixture was then added to a container and molded using a plunger. Before and after molding, the moisture in the container and the positive electrode are mixed, and the composition of the mixture is preferably optimized to allow molding of a good quality positive electrode. Mixing moisture optimization allows the positive electrode to be formed, with minimal splashing due to wet mixing, minimal flaking and excessive tool wear due to dry mixing, and optimization helps achieve the desired high cathode weight. The moisture content in the positive electrode mixture affects the overall battery electrolyte balance and has an impact on high rate testing.

One of the parameters used by cell designers characterizes a cell design as the ratio of the electrochemical capacity of one electrode to the electrochemical capacity of the opposite electrode, such as the ratio of anode (a) to cathode (C), i.e., the a: C ratio. For using zinc in the negative or anode and MnO in the positive or cathode₂The LR6 type alkaline primary cell of (1), the a: C ratio can be greater than 1.32:1, such as greater than 1.34: 1. Specifically, for the impact molded positive electrode, the a: C ratio was 1.36: 1. The a: C ratio of the ring-mode anode can be lower, such as from about 1.3:1 to about 1.1: 1.

A separator 14 is provided to separate the first electrode 18 from the second electrode 12. Separator 14 maintains a physical dielectric separation of the electrochemically active material of the positive electrode from the electrochemically active material of the negative electrode and allows for the transport of ions between the electrode materials. In addition, the separator may act as a wicking medium for the electrolyte and a collar that prevents the fragmented portion of the negative electrode from contacting the top of the positive electrode. The separator 14 may be a layered, ion-permeable, non-woven fibrous web, with typical separators generally comprising two or more layers of paper. Conventional separators are typically manufactured by pre-forming the separator material into a cup-shaped basket, which is then inserted under the cavity defined by the second electrode 12 and closed end 24 and any positive electrode material thereon; alternatively, the basket is formed by inserting two rectangular sheets of material into the cavity, the materials being rotated 90 degrees relative to each other during cell assembly. Conventional preformed separators are typically made from a sheet of non-woven fabric rolled into a cylindrical shape, the non-woven fabric conforming to the inner wall of the second electrode and having a closed bottom end.

All references cited above, as well as all references cited in this specification, are hereby incorporated by reference in their entirety.

While embodiments of the present invention have been illustrated and described in detail above, such illustration and description are to be considered illustrative or exemplary and not restrictive. It should be understood that changes and modifications may be made by those skilled in the art within the scope of the appended claims. In particular, embodiments of the invention may comprise any combination of features from the different embodiments described above and below.

Embodiments of the invention are further described below by way of illustrative, non-limiting examples to better understand embodiments of the invention and its advantages. The following examples are intended to illustrate preferred embodiments of the present invention. It will be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques used in the examples which function well in the practice of the examples and can be considered to be preferred modes for their practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the embodiments.

Discussion and examples

As previously mentioned, the discharge of a zinc-based cell involves the oxidation of zinc in the anode, resulting in the formation of zinc oxide. The oxidation reaction products of zinc form a passivation layer that inhibits the effective discharge of the remaining zinc. Precipitation of the reaction product elsewhere may be promoted by the addition of dissolved ZnO (in the free electrolyte solution and the solution contained in the anode) and additional solid ZnO (in the anode). Preventing the passivation layer from coating the anode allows better utilization of zinc, resulting in significant improvement in run time for high speed testing, particularly digital camera (DSC) ANSI standard testing.

Furthermore, nickel metal hydride (NiMH) chargers are not intended to charge primary alkaline batteries. Charging can cause abusive conditions that result in battery leakage. In particular, constant current charging may result inThe water decomposes, resulting in gas generation and an increase in internal pressure until a safety mechanism vents the electrolyte. Adding zincate source (Zn (OH)₄ ^2-) The potential for leakage is delayed by the cell being subjected to a voltage that prevents water decomposition, by embodiments of the invention that saturate or nearly saturate the electrolyte with dissolved zinc oxide, and further by adding additional zinc oxide as a solid to the anode formulation. A large amount of zinc oxide will further delay the possibility of water splitting.

Although much of the discussion in this specification refers to the addition of zinc oxide to the electrode and electrolyte solutions, other compounds that act as a source of zincate ions may be used in place of zinc oxide. For example, in addition to zinc oxide, embodiments described herein may include Zn (OH) in the electrode and/or electrolyte solution₂。

Comparison of surface passivation in anodes with and without zinc oxide addition

Two anodes were prepared to compare passivation in zinc oxide anodes with and without solid zinc oxide addition, the composition of the control and target anodes being shown in table 1.

Table 1 anode and free electrolyte compositions for surface passivation comparison

	Reference anode	Target anode
			Wt% of ZnO dissolved in 28% anodic KOH%	1	3.44
Vol.% of solid ZnO	0	2.3
			Wt% of ZnO in the surrounding free electrolyte	0	5.6

After 56 and 76 minutes of digital camera (DSC) testing, both anodes were discharged, respectively, and the surfaces of the discharged anodes were visible in fig. 2A (control anode) and fig. 2B (zinc oxide-added anode). It is apparent that the discharge reactions and reaction products are preferentially located at the periphery of the anode near the separator.

Fig. 3A and 3B are higher magnification images of the reaction zones of the control anode and the anode with added zinc oxide, respectively. At more recent magnifications, the zinc particles in the control anode were covered with ZnO (i.e. passivated). For anodes with solid zinc oxide added, the ZnO reaction product precipitates at nucleation sites seeded by the added solid zinc oxide. Thus, the zinc surface remains clean and available for discharge reactions. Higher ZnO content and presaturation increase the likelihood that precipitates will occur away from the zinc surface.

Digital Camera (DSC) testing

To test the advantages of adding solid zinc oxide to the anode and dissolving zinc oxide into the electrolyte solution, digital camera (DSC) tests were performed on a number of electrochemical cells to determine the time required to reduce the cell voltage to 1.05V, with the results shown in table 2:

TABLE 1 DSC test results

The addition of zinc oxide to the electrolyte solution and anode, respectively (cells 2 and 3, respectively), has advantages over cell 1 (which contains 1 wt% ZnO in the electrolyte solution and no solid zinc oxide added). However, the combination of both (in cell 4) shows a dramatic increase in performance in the DSC test. The interaction of these two added zinc oxides resulted in a 59% increase in the time the cell was subjected to DSC testing compared to cell 1. The advantages shown in batteries 2 and 3 are not predictive of this result.

Relationship between zinc oxide and potassium hydroxide levels and cell swelling

Corrosion from zinc in the electrodes can lead to gassing, increase the internal pressure of the cell, can cause the cell to swell and rupture during storage or during use, and can also reduce the run time of the cell. Cells with high and low levels of zinc oxide, high and low levels of anodic potassium hydroxide were compared to see how the relative levels affected the swelling of the electrochemical cell. The total percent zinc oxide saturation in the table below includes both the zinc oxide actually dissolved in the electrolyte solution and the solid zinc oxide in the anode, explaining why the percent may exceed 100%. The cells were prepared and then stored at 80 ℃ for 8 weeks to simulate prolonged aging at room temperature. The swelling in each cell was observed in mils (1/1000 inches) as an alternative to directly measuring the cell internal pressure, and the results are shown in table 3.

TABLE 3 comparison of swelling in aged cells with varying levels of anolyte concentration and ZnO saturation of the cell

Total ZnO% saturation	Anode KOH%	Swelling removal at 80 ℃ (mils)
			65	28	0·9
110	28	3·8
			65	20	0·3
110	20	1·7

For higher and lower levels of ZnO, lower KOH levels result in reduced cell swelling. Thus, reducing the percentage of KOH in the anode allows for increased run time, allowing for increased levels of ZnO by mitigating gassing problems caused by the increase.

Many modifications and other embodiments will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiments of the invention are not to be limited to the embodiments disclosed herein and that modifications and embodiments are intended to be included within the scope of the appended claims and embodiments. Although specific terms are employed in the specification, they are used in a generic and descriptive sense only and not for purposes of limitation. For the embodiments described in the present application, each embodiment disclosed in the present specification is applicable to each of the other disclosed embodiments. For example, while the present application primarily describes embodiments comprising solid and dissolved zinc oxide, embodiments in which all or some of the solid and/or dissolved zinc oxide is replaced with zinc hydroxide should also be considered within the scope of the embodiments.