Alkaline electrochemical batteries containing increased zinc oxide levels

Abstract

To provide an alkaline electrochemical battery.SOLUTION: Alkaline electrochemical cells are provided, wherein dissolved zinc oxide or zinc hydroxide is included at least in the free electrolyte solution, and / or solid zinc oxide or zinc hydroxide is included in the anode, so as to slow formation of a zinc oxide passivation layer on a zinc electrode. Methods for preparing such cells are also provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefits of U.S. Provisional Patent Application No. 62 / 795,750 filed January 23, 2019, and U.S. Patent Application No. 16 / 674,828 filed November 5, 2019, whose contents are thus incorporated in their entirety by reference. [Background technology]

[0002] Alkaline electrochemical batteries are commercially available in known battery sizes such as LR6(AA), LR03(AAA), LR14(C), and LR20(D). The batteries have a cylindrical shape that must conform to dimensional standards set by organizations such as the International Electrochemical Commission. Electrochemical batteries are used by consumers to power a wide range of electrical devices, such as clocks, radios, toys, electronic games, film cameras (commonly including flashlight units), and digital cameras. Such electrical devices have a wide range of discharge conditions, for example, from low drain to relatively high drain. Due to the increasing use of high-drain devices such as digital cameras, it is desirable for manufacturers to produce batteries with desirable high-drain discharge characteristics.

[0003] Since battery shape and size are often fixed, battery manufacturers must modify battery characteristics to improve performance. Attempts to address the problem of how to improve battery performance in specific devices, such as digital cameras, have typically involved changes to the battery's internal configuration. For example, the battery configuration is modified by increasing the amount of active material used within the battery.

[0004] Zinc (Zn) is a well-known substance commonly used as the active anode material in electrochemical batteries, such as dry cell batteries. During discharge in an electrochemical battery, zinc is oxidized to form zinc oxide (ZnO). This zinc oxide reaction product forms a passivation layer, which can reduce battery performance by inhibiting the efficient discharge of the remaining zinc. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Embodiments of the present invention were designed with the aim of overcoming the limitations of the aforementioned batteries and other such batteries. [Means for solving the problem]

[0006] The embodiment is an alkaline electrochemical battery comprising a) a container and b) an electrode assembly disposed within the container and comprising a cathode, an anode, a separator positioned 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 the free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional elevation view of an alkaline electrochemical cell according to an embodiment. [Figure 2A] This is a photograph of a control anode according to the embodiments described herein. [Figure 2B] This is a photograph of an anode according to the embodiment described herein. [Figure 3A] This is a magnified photograph of the image in Figure 2A. [Figure 3B] This is a magnified photograph of the image in Figure 2B. [Modes for carrying out the invention]

[0008] Herein, various embodiments are described more fully with reference to the accompanying drawings, which show some, but not all, embodiments. In fact, various embodiments can be embodied in many different forms and should not be construed as being limited to the embodiments shown herein, but rather these embodiments are provided so that this disclosure will satisfy the applicable legal requirements. Similar numbers refer to similar elements throughout. In the following description, various components may be shown as having specific values ​​or parameters, but these items are provided as exemplary embodiments. In fact, many equivalent parameters, sizes, ranges, and / or values ​​can be implemented, so these exemplary embodiments do not limit their various aspects and concepts. Terms such as “first” and “second,” “primary,” “exemplary,” and “secondary,” etc., do not indicate any order, quantity, or importance, but are used to distinguish one element from another. Furthermore, the terms “a,” “an,” and “the” do not indicate a limiting quantity, but indicate the presence of “at least one” of the items referred to.

[0009] It is intended that each embodiment disclosed herein is applicable to each of the other disclosed embodiments. All combinations and partial combinations of the various elements described herein are within the scope of the embodiments.

[0010] When a parameter range is provided, it is understood that all integers and ranges within that range, as well as one-tenth and one-hundredth thereof, are also provided by embodiments of the disclosure of the present invention. For example, "5-10%" includes 5%, 6%, 7%, 8%, 9%, and 10%, and 5.0%, 5.1%, 5.2%...9.8%, 9.9%, and 10.0%, and 5.00%, 5.01%, 5.02%...9.98%, 9.99%, and 10.00%, and for example, 6-9%, 5.1%-9.9%, and 5.01%-9.99%.

[0011] When used herein, "approximately" in relation to a number or range means a range of ±10% of the number or range listed or claimed.

[0012] As used herein, "total battery electrolyte mass" means the total mass of the electrolyte in the battery, and "total battery electrolyte concentration" means the total concentration of the electrolyte in the battery. The total battery electrolyte concentration can be determined according to the calculation of (total battery electrolyte mass) / (total battery electrolyte mass + total water mass in the battery), and is multiplied by 100 if it is to be expressed as a percentage. The total additive weight percentage in the total battery electrolyte solution can be determined by the calculation of (total mass of additives in the battery) / (total mass of additives in the battery + total battery electrolyte mass + total water mass in the battery)×100.

[0013] As used herein, the "total weight percentage" of a zinc compound in a battery or a portion thereof is the ratio of the total weight of the zinc compound in the battery or the portion thereof to the total mass or total weight of the zinc compound, electrolyte, and water. For example, the "total zinc oxide weight percentage" of a battery is calculated as (zinc oxide mass) / (zinc oxide mass + electrolyte mass + water mass)×100%.

[0014] The "total dissolved zinc oxide weight percentage" in the total battery electrolyte is calculated as (dissolved zinc oxide mass in the battery) / (dissolved zinc oxide mass in the battery + electrolyte mass in the battery + water mass in the battery)×100%. This measurement does not take into account the mass of solid (i.e., undissolved) zinc oxide in the anode.

[0015] As used herein, the "electrolyte concentration percentage" of an electrode means the ratio of the total weight of the electrolyte in the electrode to the total weight of the electrolyte and water in the electrode. For example, the "KOH weight percentage" of an electrode is calculated as (KOH mass in the electrode) / (KOH mass in the electrode + water mass in the electrode)×100%.

[0016] As used herein, “improvement” with respect to specific capacity means an increase in specific capacity. Generally, “improvement” of a performance characteristic or metric of a material or electrochemical battery means that the performance characteristic or metric differs in a way that the user or manufacturer of the material or battery would find desirable (i.e., lower cost, longer lifespan, more power output, greater durability, easier or faster to manufacture, etc.) compared to a different material or electrochemical battery.

[0017] As used herein, "specific capacity" refers to the total charge in an electrochemical cell when discharged at a specific rate. Specific capacity is generally measured in ampere-hours.

[0018] As used herein, "operating time" means the length of time during which an electrochemical battery can supply a certain level of charge.

[0019] When used herein, describing a solution as "X% saturated" with solute means that it contains X% of the maximum amount of solute that can be dissolved in the solution at the same temperature, pressure, etc., taking into account all other components of the solution (e.g., dissolved electrolytes).

[0020] When describing an electrochemical cell as having a compound with "X% total cell saturation," both the presence of the compound dissolved in the free electrolyte solution and the presence of the compound in the anode should be considered. For example, to calculate the total cell saturation of zinc oxide in an electrochemical cell, it is considered necessary to determine the amount of zinc oxide dissolved in the free electrolyte solution, along with the solid and dissolved zinc oxide in the anode. This may result in a total cell saturation percentage exceeding 100%.

[0021] When used in this specification, "zincate ion source" refers to zincate ions ((Zn(OH)4) when added to a solution. 2-This refers to any compound that produces Zn. Non-limiting examples include Zn, zinc oxide (ZnO), and zinc hydroxide (Zn(OH)2). In embodiments, this term may refer only to ZnO and Zn(OH)2.

[0022] The embodiment is an alkaline electrochemical battery comprising a) a container and b) an electrode assembly disposed within the container and comprising a cathode, an anode, a separator positioned 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 the free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide.

[0023] In the embodiment, the anode comprises solid zinc oxide, and the free electrolyte solution comprises dissolved zinc oxide.

[0024] In one embodiment, the free electrolyte solution contains more than 2.0 weight percent of dissolved zinc oxide. In yet another embodiment, the free electrolyte solution contains about 4.0 to 6.5 weight percent of dissolved zinc oxide.

[0025] In one embodiment, the anode comprises a gelling electrolyte prepared by combining a gelling agent with a first aqueous alkaline electrolyte solution comprising an alkali metal hydroxide electrolyte and dissolved zinc oxide. In yet another embodiment, the first aqueous alkaline electrolyte solution comprises dissolved zinc oxide in an amount of ≥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 weight percent. In another embodiment, the first aqueous alkaline electrolyte solution comprises dissolved zinc oxide in an amount of about 2.7 to 3.3 weight percent.

[0026] In an embodiment, the cathode includes a second aqueous alkaline electrolyte solution containing an alkali metal hydroxide electrolyte and dissolved zinc oxide. In yet another embodiment, the second aqueous alkaline electrolyte solution contains dissolved zinc oxide in an amount of ≧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 weight percent. In yet another embodiment, the second aqueous alkaline electrolyte solution contains dissolved zinc oxide in an amount of about 2.5 to 4.0 weight percent or about 2.7 to 3.3 weight percent.

[0027] In an embodiment, the first aqueous alkaline electrolyte solution and the second aqueous alkaline electrolyte solution are the same.

[0028] In an embodiment, the total dissolved zinc oxide weight percent in the total battery electrolyte solution of the electrochemical cell is about 1.5 to 4.5 weight percent. In an embodiment, the total zinc oxide weight percent in the total battery electrolyte solution of the electrochemical cell is about 2.0 to 4.0 or about 2.5 to 3.5 weight percent. In an embodiment, the total zinc oxide weight percent in the total battery electrolyte solution of the electrochemical cell is higher than about 4.5 weight percent. In an embodiment, the total zinc oxide weight percent in the total battery electrolyte solution of the electrochemical cell is about 0.5 to 4.5 weight percent, about 0.5 to 3.0 weight percent, or about 0.5 to 2.0 weight percent.

[0029] In an embodiment, the total battery electrolyte of the electrochemical cell is saturated with more than 40% dissolved zinc oxide.

[0030] In an embodiment, solid zinc oxide or solid zinc hydroxide is replaced and contains a cationic substituent or an anionic substituent, and the substituted solid zinc oxide or the substituted solid zinc hydroxide is less soluble than the unsubstituted solid zinc oxide or the substituted solid zinc hydroxide.

[0031] In an embodiment, the substituted solid zinc oxide is such that when Y is at least one cationic substituent and 0 < x ≦ 0.50, Zn 1-x Y xIt has the chemical formula O.

[0032] In an embodiment, the substituted solid zinc hydroxide has the chemical formula Zn 1-x Y x (OH)2 when Y is at least one cationic substituent and 0 < x ≦ 0.50.

[0033] In an embodiment, the substituted solid zinc oxide has the chemical formula ZnO 1-w A (2w / z) when A is at least one anionic substituent, 0 < w ≦ 0.50, and z is the charge of the anionic substituent.

[0034] In an embodiment, the substituted solid zinc hydroxide has the chemical formula Zn(OH) 2-w A (w / z) when A is at least one anionic substituent, 0 < w ≦ 0.50, and z is the charge of the anionic substituent.

[0035] In an embodiment, the substituted solid zinc oxide has the chemical formula Zn 1-x Y x O 1-w (OH) 2w when Y is at least one cationic substituent, 0 < x ≦ 0.50, and 0 < w ≦ 0.50.

[0036] In an embodiment, the substituted solid zinc oxide is a mixed oxide hydroxide that is cation - substituted and anion - substituted. In yet another embodiment, the mixed oxide hydroxide that is cation - substituted and anion - substituted has the chemical formula Zn 1-x Y x O 1-w-t (OH) 2w A (2t / z) when Y is at least one cationic substituent, 0 < x ≦ 0.50, A is at least one anionic substituent, 0 < w ≦ 0.50, 0 < t ≦ 0.50, and z is the charge of the anionic substituent.

[0037] In the embodiment, the cationic substituent is selected from the group consisting of Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, and Sr, and any combination thereof.

[0038] In this embodiment, the anionic substituent is CO3 2- and PO4 3- The group is selected from those consisting of , and any combination thereof.

[0039] In the embodiment, the anode contains solid zinc oxide in an amount of about 0.2 to 5 volume percent based on its total volume. In the embodiment, the anode contains solid zinc oxide in an amount of about 0.3 to 1.5 volume percent based on its total volume. In the embodiment, the anode contains solid zinc oxide in an amount of about 0.66 volume percent based on its total volume.

[0040] In the embodiment, the alkaline electrochemical battery contains about 3.0–8.8% total zinc oxide by weight. In the embodiment, the alkaline electrochemical battery contains 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%, and about 8.0–9.0% total zinc oxide by weight. In the embodiment, the alkaline electrochemical battery contains a total zinc oxide by weight higher than about 3.0%. In the embodiment, the alkaline electrochemical battery contains a total zinc oxide by weight higher 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%, and 8.5%. The alkaline electrochemical battery contains about 4.75% total zinc oxide by weight.

[0041] In the embodiment, the anode contains an electrolyte concentration percentage of approximately 16.0–30.0%. In the embodiment, the anode contains an electrolyte concentration percentage of approximately 18.0–22.0%. In the embodiment, the anode contains an electrolyte concentration percentage lower than approximately 22.0%.

[0042] In the embodiment, the total battery electrolyte concentration is approximately 26.0-30.0%. In the embodiment, the total battery electrolyte concentration is lower than 29.0%.

[0043] In the embodiment, the overall battery saturation of zinc oxide or zinc hydroxide is at least about 40%. In the embodiment, the overall battery saturation of zinc oxide or zinc hydroxide is at least about 40-125%. In the embodiment, the overall battery saturation of zinc oxide or zinc hydroxide is about 40-125%. In the embodiment, the overall battery saturation of 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%.

[0044] In this embodiment, the electrochemical battery is a primary battery. In this alternative embodiment, the electrochemical battery is a secondary battery.

[0045] In the embodiment, the free electrolyte solution includes potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), magnesium perchlorate (Mg(ClO4)2), magnesium chloride (MgCl2), or magnesium bromide (MgBr2).

[0046] In some embodiments, the alkaline electrochemical battery has a higher specific capacity or operating time than similar alkaline electrochemical batteries lacking dissolved zinc oxide in the free electrolyte. In yet another embodiment, the specific capacity or operating time is over 1% to over 100%, over 5% to over 90%, over 10% to over 80%, over 15% to over 70%, over 20% to over 60%, over 25% to over 50%, or over 30% to over 40%.

[0047] In this embodiment, the battery has a voltage of 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.

[0048] The embodiments will be better understood by referring to Figure 1, which shows a cylindrical battery 1 in an elevation section view, having a nail-shaped or bobbin-shaped configuration and dimensions equivalent to a conventional LR6(AA) size alkaline battery, and being particularly well suited to the embodiments. However, it will be understood that batteries according to these embodiments may have other sizes and shapes, such as prism or button shapes, and electrode configurations known in the art. The materials and designs for the components of the electrochemical battery shown in Figure 1 are for illustrative purposes only, and other materials and designs may be substituted. Furthermore, in certain embodiments, the materials for the cathode and anode may be covered onto the surfaces of the separator and / or current collector and wound to form a "jelly roll" configuration.

[0049] Figure 1 shows an electrochemical cell 1 comprising a container or can 10 having a closed bottom end 24, a top end 22, and a side wall 26 between them. The closed bottom end 24 includes a terminal cover 20 with a projection. The can 10 has an inner wall 16. In this embodiment, the positive terminal cover 20 is welded or otherwise attached to the bottom end 24. In one embodiment, the terminal cover 20 may be formed of plated steel having a protruding bump in its central region, for example. The container 10 may preferably be formed of a metal such as steel plated internally with nickel, cobalt, and / or other metals or alloys, or other material having sufficient structural properties to accommodate various packing materials in the electrochemical cell. Labels 28 may be formed around the outer surface of the container 10 and on the periphery of the positive terminal cover 20 and the negative terminal cover 46, insofar as the negative terminal cover 46 is electrically insulated from the container 10 and the positive terminal 20.

[0050] Inside the container 10, a first electrode 18 and a second electrode 12 are arranged with a separator 14 in between. The first electrode 18 is positioned in a space defined by the separator 14 and a closing assembly 40 fixed to the open end 22 of the container 10. The closing end 24, the side wall 26, and the closing assembly 40 define the cavity in which the battery electrodes are housed.

[0051] The closure assembly 40 includes a closure member 42, such as a gasket, a current collector 44, and a conductive terminal 46 that is in electrical contact with the current collector 44. The closure member 42 preferably includes a pressure relief vent that will cause the closure member to rupture if the internal pressure of the battery becomes excessive. The closure member 42 can be formed from a polymer or elastomer material, such as an injection-molded polymer compound such as a polypropylene matrix combined with nylon-6,6 or nylon-6,12, poly(phenylene oxide), or polystyrene, or from another material such as metal, as long as the current collector 44 and the conductive terminal 46 are electrically insulated from the container 10 that functions as a current collector for the second electrode 12. In the illustrated embodiment, the current collector 44 is an elongated nail-shaped or bobbin-shaped component. The current collector 44 is made from a metal or metal alloy such as copper or brass, a metal or plastic collector with conductive plating, etc. Other suitable materials may be used. The current collector 44 is inserted through a hole preferably located in the center of the closing member 42.

[0052] The first electrode 18 is preferably a negative electrode or an anode. The negative electrode comprises a mixture of zinc (as an active material), a conductive material, solid zinc oxide, and a surfactant. The negative electrode may optionally contain other additives, such as binders or gelling agents. Preferably, the volume of the active material used in the negative electrode is sufficient to maintain desirable interparticle contact and a desirable anode-to-cathode (A:C) ratio.

[0053] Interparticle contact must be maintained throughout the battery's effective lifespan. If the volume of active material in the negative electrode is too small, the battery voltage may suddenly drop to an unacceptably low value when the battery powers a device. This voltage drop is thought to be caused by a loss of continuity in the conductive matrix of the negative electrode. The conductive matrix can be formed from non-discharging active material particles, electrochemically formed conductive oxides, or a combination thereof. The voltage drop may occur after oxide formation has begun but before a sufficient network structure is formed to bridge all the active material particles present.

[0054] Zinc suitable for use in the embodiments described above can be purchased from several different commercial sources under various names such as BIA100 and BIA115. Umicore SA in Brussels, Belgium is an example of a zinc supplier. In preferred embodiments, the zinc powder has approximately 25 to 40 percent, preferably 28 to 38 percent, of fine particles smaller than 75 μm. Generally, lower percentages of fine particles do not enable the desired DSC operation, while higher percentages may lead to increased gas generation. A suitable zinc alloy is required to reduce negative electrode gas generation in the battery and maintain the test operation results.

[0055] A surfactant, either nonionic or anionic, or a combination thereof, is present within the negative electrode. In this embodiment, the surfactant is a phosphate ester surfactant. Adding solid zinc oxide alone increases the anode resistance during discharge, but this is mitigated by the addition of a surfactant. The addition of a surfactant increases the surface charge density of solid zinc oxide, thereby reducing the anode resistance as described above. The use of a surfactant is thought to help form a more porous discharge product as the surfactant accumulates on the outer surface of the solid zinc oxide. When the surfactant is anionic, it carries a negative charge, and in an alkaline solution, the surfactant adsorbed on the surface of solid zinc oxide is thought to change the surface charge density of the solid zinc oxide particle surface. The adsorbed surfactant is thought to result in repulsive electrostatic interactions between the solid zinc oxide particles. The surfactant adsorbed on solid zinc oxide results in a high surface charge density on the solid zinc oxide particle surface, thus reducing the increase in anode resistance caused by the addition of solid zinc oxide. The larger the BET area of ​​solid zinc oxide, the more surfactant can be adsorbed on the solid zinc oxide surface. In the embodiment, the surfactant concentration is approximately 5 to 50 ppm by weight compared to the electrode active material. In the embodiment, the surfactant concentration is 10 to 20 ppm.

[0056] In an embodiment, the negative electrode contains solid zinc oxide in an amount from about 0.2 weight percent to 5 weight percent based on the total weight of the negative electrode. In an embodiment, the negative electrode contains solid zinc oxide in an amount from about 1 weight percent to 4 weight percent. In a preferred embodiment, the negative electrode contains solid zinc oxide in an amount from about 0.3 weight percent to 1 weight percent. Further, in a preferred embodiment, the negative electrode contains solid zinc oxide in an amount of about 0.66 weight percent.

[0057] In an embodiment, the solid zinc oxide is substituted to reduce its solubility. In an embodiment, a portion of the zinc in the solid zinc oxide is substituted with another cation. In an embodiment, the substituted solid zinc oxide has the chemical formula Zn 1-x Y x O when Y is at least one cation substituent and 0 < x ≦ 0.50. In an embodiment, the cation substituent is selected from the group consisting of Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, and Sr, and any combination thereof. In an embodiment, x is 0.01 - 0.40, 0.02 - 0.35, 0.4 - 0.30, 0.05 - 0.25, or 0.10 - 0.20. In an embodiment, x 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.

[0058] In an embodiment, a portion of the oxygen in the solid zinc oxide is substituted with another anion. In an embodiment, the substituted solid zinc oxide has the chemical formula ZnO 1-w A (2w / z) when A is at least one anion substituent, 0 < w ≦ 0.50, and z is the charge of the anion substituent. In an embodiment, the anion substituent is CO3 2- and PO4 3-Selected from the group consisting of and any combination thereof. In the embodiment, w is 0.01-0.40, 0.02-0.35, 0.4-0.30, 0.05-0.25, or 0.10-0.20. In the embodiment, 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. In the embodiment, the solid zinc oxide includes cationic substituents and anionic substituents.

[0059] The aqueous alkaline electrolyte solution (or simply “aqueous electrolyte solution”) contains an alkali metal hydroxide such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) or a mixture thereof. Potassium hydroxide is preferred. The alkaline electrolyte used to form the gel-like electrolyte of the negative electrode contains alkali metal hydroxide in an amount of about 16 to about 36 weight percent, for example, about 16 to about 28 weight percent, particularly about 18 to about 22 weight percent, or about 20 weight percent, based on the total weight of the alkaline electrolyte solution. In embodiments, this alkali metal hydroxide is present in an amount of 16 to 36 weight percent. In embodiments, this alkali metal hydroxide is present in an amount higher 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 weight percent. In embodiments, the alkali metal hydroxide is present in amounts 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 weight percent. In embodiments, the alkali metal hydroxide is present in amounts 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 weight percent.

[0060] The aqueous alkaline electrolyte solution also contains dissolved zinc oxide in an amount ranging from approximately 1.5 to 4 weight percent based on its total weight.

[0061] As is well known in our art, a gelling agent, such as a cross-linked polyacrylic acid like Carbopol® 940, available from Noveon, Inc. in Cleveland, Ohio, USA, is preferably used in the negative electrode. Carboxymethylcellulose, polyacrylamide, and sodium polyacrylate are examples of other gelling agents suitable for use in alkaline electrolyte solutions. The gelling agent is desirable to maintain a substantially uniform dispersion of zinc particles and zinc oxide particles in the negative electrode. The amount of gelling agent present is selected so as not to be excessively large, resulting in a low percentage of electrolyte separation and so as not to lead to problems associated with anode distribution due to anodic viscosity at the yield stress.

[0062] Dissolved zinc oxide is preferably present in the anode by dissolution in an aqueous electrolyte solution to improve plating on bobbins or nail current collectors and reduce gas generation when the negative electrode is not in use. The added dissolved zinc oxide is distinct from the zinc oxide present in the anode composition. In one embodiment, a level of dissolved zinc oxide of 3-4 weight percent based on the total weight of the negative electrode electrolyte solution is preferred. In embodiments, dissolved zinc oxide is present in amounts higher than 3 weight percent in the negative electrode electrolyte solution. As shown above, generally, soluble zinc oxide or dissolved zinc oxide is approximately 4 m³ when measured using a Tristar 3000 BET specific area analyzer with multipoint calibration from Micrometrics after degassing zinc oxide at 150°C for 1 hour. 2 It has a BET area of ​​1 / g and a particle size D50 (average diameter) of approximately 1 micron when measured using a CILAS size analyzer.

[0063] Other components that may optionally be present in the negative electrode include, but are not limited to, gas generation inhibitors, organic or inorganic corrosion inhibitors, plating agents, binders, or other surfactants. Examples of gas generation inhibitors or corrosion inhibitors may include indium hydroxide, perfluoroalkylammonium salts, and indium salts such as alkali metal sulfides. In yet another embodiment, it is preferable that the negative electrode contains sodium silicate in an amount of about 0.3 weight percent based on the total weight of the negative electrode electrolyte to substantially prevent a battery short circuit through the separator during battery discharge.

[0064] The negative electrode can be formed by several different methods known in the art. For example, the negative electrode components can be dry-mixed and added to the battery, the alkaline electrolyte can be added separately, or, in a preferred embodiment, a pre-gelled negative electrode treatment is used.

[0065] In one embodiment, zinc powder and solid zinc oxide powder, along with other optional powders other than a gelling agent, are combined and mixed. A surfactant is then introduced into the mixture containing zinc and solid zinc oxide. A pregel containing an alkaline electrolyte solution, soluble zinc oxide, and a gelling agent, optionally containing other liquid components, is introduced into the mixture of surfactant, zinc, and solid zinc oxide and further mixed to obtain a substantially homogeneous mixture before addition to the battery. Alternatively, in yet another preferred embodiment, solid zinc oxide is pre-dispersed in a negative electrode pregel containing an alkaline electrolyte, gelling agent, soluble zinc oxide, and other desired liquids, and mixed for, for example, about 15 minutes. Then, the solid zinc oxide and surfactant are added, and the negative electrode is mixed for an additional period, such as about 20 minutes. The amount of gel-like electrolyte utilized in the negative electrode is generally about 25% to about 35% by weight, for example, about 32% by weight, based on the total weight of the negative electrode. The volume percentage of the gel-like electrolyte can be about 70% based on the total volume of the negative electrode.

[0066] In addition to the aqueous alkaline electrolyte absorbed by the gelling agent during the negative electrode manufacturing process, an additional amount of aqueous alkali metal hydroxide solution, i.e., a “free electrolyte,” is added to the battery during the manufacturing process. The free electrolyte can be incorporated into the battery by placing it in a cavity determined by the positive electrode, the negative electrode, or a combination thereof. The method used to incorporate the free electrolyte into the battery is not important as long as the free electrolyte is in contact with the negative electrode, the positive electrode, and the separator. In one embodiment, the free electrolyte is added both before and after the addition of the negative electrode mixture. In one embodiment, about 0.97 grams of a 34 wt percent KOH solution is added as the free electrolyte to an LR6 type battery, and about 0.87 grams is added to the cavity separated by the separator before the negative electrode is inserted. The remainder of the 34 wt percent KOH solution is injected into the cavity separated by the separator after the negative electrode is inserted. This free electrolyte solution contains dissolved zinc oxide in the range of about 0.01 to 6.0 wt percent. In the embodiment, the free electrolyte solution is approximately 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, 3.4, 3.5, 3 The solution contains dissolved zinc oxide in amounts higher than, lower than, equal to, or between two of these values, 0.6, 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, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, and 6.0 weight percent. In a preferred embodiment, the free electrolyte solution contains dissolved zinc oxide in amounts between about 4.0 and 6.0 weight percent.The free electrolyte solution may be saturated with dissolved zinc oxide at a concentration higher than or equal to approximately 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%.

[0067] The second electrode, also referred to herein as the positive electrode or cathode, comprises an electrochemical active material. Manganese dioxide (EMD) is a commonly used electrochemical active material and is present in the positive electrode, i.e., in an amount generally from about 80 to about 92 weight percent, preferably from about 86 to 92 weight percent, based on the total weight of the additives, including the EMD, conductive material, positive electrode electrolyte, and, if present, organic additives. The positive electrode is formed by combining and mixing the desired electrode components, then distributing a certain amount of this mixture into the open end of a container, and subsequently shaping this mixture using a ram into a solid tubular structure that defines a cavity in the container into which the separator 14 and the first electrode 18 are subsequently placed. The second electrode 12 has a ledge 30 and an inner surface 32, as shown in Figure 1. Alternatively, the positive electrode can be formed by pre-forming a plurality of rings from a mixture containing EMD and optionally additives, and then inserting these rings into a container to form a tubular second electrode. The battery shown in Figure 1 is thought to typically contain three or four rings.

[0068] The positive electrode may include other components, such as graphite, which, when mixed with EMD, provide a conductive matrix substantially throughout the positive electrode. The conductive material can be natural, i.e., mineral, or synthetic, i.e., manufactured. In one embodiment, the battery includes a positive electrode having an active material or oxide-to-carbon ratio (O:C ratio) in the range of about 12 to about 14. An excessively high oxide-to-carbon ratio reduces the resistance from the container to the cathode, and this reduction may affect the overall battery resistance, potentially impacting high-rate tests such as DSC testing or having a higher cutoff voltage. Furthermore, the graphite may be swollen or non-swollen. Suppliers of graphite for use in alkaline batteries include Timcal America in Westlake, Ohio, USA; Superior Graphite Company in Chicago, Illinois, USA; and Lonza, Ltd. in Basel, Switzerland. The conductive material is generally present in amounts ranging from about 5 to about 10 weight percent based on the total weight of the positive electrode. Excessive graphite may reduce the EMD input and therefore the battery capacity, while excessive graphite may increase the contact resistance from the container to the cathode and / or the bulk cathode resistance. An example of an additional additive is commercially available barium sulfate (BaSO4) from Bario E. Derivati ​​SpA in Massa, Italy. Barium sulfate is generally present in amounts ranging from about 1% to about 2% by weight based on the total weight of the positive electrode. Other additives may include, for example, barium acetate, titanium dioxide, binders such as corethylene, and calcium stearate.

[0069] In one embodiment, the positive electrode components (such as EMD), conductive material, and barium sulfate, and optionally additives, are mixed together to form a homogeneous mixture. During the mixing process, an alkaline electrolyte solution, optionally containing organic additives, e.g., a KOH solution ranging from about 37% to about 40%, is evenly dispersed in this mixture, thereby ensuring uniform dispersion of the solution throughout the positive electrode material. In the embodiment, the alkaline electrolyte solution used to form the cathode contains any of the preceding amounts of dissolved zinc oxide, including an amount saturated with dissolved zinc oxide. This mixture is then added to a container and molded using a ram. The moisture content in the container and the positive electrode mixture before and after molding, and the components of this mixture, are preferably optimized to enable the molding of a high-quality positive electrode. Optimization of the mixture moisture content allows for the molding of the positive electrode while minimizing splashes and burrs caused by a wet mixture, as well as peeling and excessive tool wear caused by a dry mixture, and this optimization helps to achieve a desired high cathode weight. The moisture content in the positive electrode mixture may affect the overall battery electrolyte balance and have an impact on high-rate testing.

[0070] One of the parameters used by battery designers to characterize a battery design is the ratio of the electrochemical capacity of one electrode to the electrochemical capacity of the opposite electrode, for example, the anode (A) to cathode (C) ratio, i.e., the A:C ratio. In an LR6 type alkaline primary battery that uses zinc for the negative electrode or anode and MnO2 for the positive electrode or cathode, the A:C ratio is greater than 1.32:1, for example greater than 1.34:1, and can be as high as 1.36:1, especially for impact-molded positive electrodes. The A:C ratio for ring-molded positive electrodes can be lower, such as from about 1.3:1 to about 1.1:1.

[0071] The separator 14 is provided to separate the first electrode 18 from the second electrode 12. The separator 14 maintains the physical dielectric separation of the electrochemical active material of the positive electrode from the electrochemical active material of the negative electrode and allows for the transport of ions between the electrode materials. Furthermore, the separator acts as a wicking medium for the electrolyte and also functions as a collar to prevent fragmented portions of the negative electrode from contacting the top of the positive electrode. The separator 14 can be a layered ion-permeable nonwoven fabric. Typically, a typical separator includes two or three or more layers of paper. Conventional separators are usually formed either by pre-forming the separator material in a cup-shaped basket that is subsequently inserted below a cavity defined by the second electrode 12, the closed end 24, and either of the positive electrode materials thereon, or by inserting two rectangular separator sheets into the cavity during battery assembly with the materials rotated 90° relative to each other. Conventional pre-formed separators typically consist of a nonwoven fabric sheet wound into a cylindrical shape with a closed bottom end that fits the inner wall of the second electrode.

[0072] All of the cited documents mentioned above, as well as all other documents cited herein, are incorporated herein by reference in their entirety.

[0073] Although embodiments have been illustrated and described in detail above, such illustrations and descriptions should be considered illustrative or exemplary, and not limiting. Those skilled in the art will understand that modifications and alterations can be made within the scope and spirit of the following claims. In particular, the embodiments include any combination of features from the various embodiments described above and below.

[0074] The embodiments will be further described using the following exemplary, non-limiting embodiments, which will provide a clearer understanding of the embodiments and their many advantages. The following embodiments are included to specify preferred embodiments. It should be acknowledged by those skilled in the art that the techniques disclosed in the following embodiments represent techniques used in the embodiments so as to function well in carrying out the embodiments, and can therefore be considered to constitute a preferred mode for carrying out the embodiments. However, it should be acknowledged that, based on the disclosure of the present invention, many modifications can be made to the specific embodiments disclosed without departing from the spirit and scope of the embodiments described above, and similar or comparable results can still be obtained.

[0075] Discussion and Examples

[0076] Discharging of zinc-based batteries involves oxidation of zinc at the anode, leading to the formation of zinc oxide as described above. The zinc oxide reaction product forms a passivation layer that inhibits the efficient discharge of the remaining zinc. The addition of dissolved ZnO (both in the free electrolyte solution and in the solution contained in the anode) and auxiliary solid ZnO (in the anode) promotes the precipitation of this reaction product elsewhere. By preventing the passivation layer from coating the anode, better utilization of zinc is enabled. This results in a substantial improvement in uptime in high-rate testing, particularly in ANSI standard testing of digital still cameras (DSCs).

[0077] Furthermore, nickel metal hydride (NiMH) chargers are not intended for charging primary alkaline batteries. Charging can create adverse conditions that can lead to battery leakage. In particular, constant current charging can lead to hydrolysis until the safety mechanism releases the electrolyte, resulting in gas generation and high internal pressure. 2-By adding a source of zinc oxide, the battery can be made to apply a current at a voltage that prevents water decomposition, thereby delaying the potential for leakage. This delay is achieved by embodiments of the present invention, namely by saturating or nearly saturating the electrolyte with dissolved zinc oxide and further adding auxiliary zinc oxide as a solid to the anode formulation. A larger amount of zinc oxide will further delay the potential for water decomposition.

[0078] Most of the discussion herein refers to the addition of zinc oxide to the electrode and electrolyte solution, but other compounds that function as sources of zincate ions can be used instead of or in addition to zinc oxide. For example, the embodiments described herein may contain Zn(OH)2 in the electrode and / or electrolyte solution instead of or in addition to zinc oxide.

[0079] Comparison of surface passivation in anodes with and without zinc oxide.

[0080] Two anodes were prepared to compare passivation with and without solid zinc oxide anodes. The control anode and its composition are shown in Table 1 below.

[0081] (Table 1) Table 1: Anode and free electrolyte composition for comparison of surface passivation TIFF0007887542000001.tif28155

[0082] Both anodes were discharged, and the discharged anode surfaces at 56 and 76 minutes after the digital still camera (DSC) test can be seen in Figure 2A (control anode) and Figure 2B (zinc oxide-doped anode). It is clear that the discharge reaction and reaction products are selectively located around the anode near the separator.

[0083] Figures 3A and 3B are more magnified images of the reaction zones for the control anode and the zinc oxide-doped anode. Under closer magnification, the zinc particles in the control are covered with ZnO (i.e., passivated). With respect to the solid zinc oxide-doped anode, the ZnO reaction product precipitates at nucleation sites seeded by the added solid zinc oxide. Thus, the zinc surface remains clean and available for the discharge reaction. Higher ZnO levels and pre-saturation increase the probability that precipitation occurs away from the zinc surface.

[0084] Digital Still Camera (DSC) Exam

[0085] To test the benefits of adding solid zinc oxide to the anode versus dissolving zinc oxide in the electrolyte solution, digital still camera (DSC) tests were performed on various electrochemical batteries. Each battery was tested, and the time required to reduce the battery voltage to 1.05V was determined. The results are shown in Table 2 below.

[0086] (Table 2) Table 2: DSC test results TIFF0007887542000002.tif60155

[0087] The addition of zinc oxide to the electrolyte solution and anode individually (to batteries 2 and 3, respectively) has been shown to have beneficial effects compared to battery 1 (containing 1 wt% ZnO in the electrolyte solution but without added solid ZnO). However, both combinations (in battery 4) show a dramatic increase in performance in DSC testing. The combined interaction of these added zinc oxides resulted in a 59% increase compared to battery 1 within the time it was possible to perform DSC testing on the batteries. This result is considered unexpected given the moderate benefits shown in batteries 2 and 3.

[0088] Relationship between zinc oxide and potassium hydroxide levels and battery expansion

[0089] Corrosion from zinc present in the electrodes can cause gas generation, increasing the internal pressure of the battery. This can cause the battery to swell during storage or while in use, and subsequently rupture. This corrosion may also shorten the battery's operating time. Comparisons of batteries with relatively high and low levels of zinc oxide and high and low levels of potassium hydroxide in the anode were made to observe how these relative levels affect the swelling of the electrochemical battery. The overall zinc oxide saturation percentages in the table below take into account both the zinc oxide actually dissolved in the electrolyte solution and the solid zinc oxide in the anode, and consequently the percentage may be greater than 100%. These batteries were prepared and then stored at 80°C for 8 weeks to simulate long-term degradation at room temperature. Instead of directly measuring the internal pressure of the batteries, the swelling in each battery was observed in units of mills (1 / 1000 of an inch). The results are shown in Table 3.

[0090] (Table 3) Table 3: Comparison of expansion in aged batteries with varying levels of anode electrolyte concentration and battery ZnO saturation. TIFF0007887542000003.tif34155

[0091] Lower KOH levels resulted in reduced battery expansion for both higher and lower levels of ZnO. Specifically, reducing the KOH percentage in the anode was found to enable increased uptime by allowing increased levels of ZnO through mitigating the gas generation problems caused by this increase.

[0092] Those skilled in the art who benefit from the teachings of the present invention presented in the above description and the related drawings, and who are familiar with the embodiments described above, will likely recall many modifications and other embodiments. It will be understood that these embodiments are not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the claims and the list of embodiments disclosed herein. While specific terms are used herein, these terms are used only in a general and descriptive sense, not for limiting purposes. With respect to the embodiments described in this application, each embodiment disclosed herein is intended to be applicable to each of the other embodiments disclosed. For example, while this application primarily describes embodiments involving solid zinc oxide and soluble zinc oxide, similar embodiments in which all or part of the solid zinc oxide and / or soluble zinc oxide are replaced by zinc hydroxide are also considered to be within the scope of these embodiments. [Explanation of symbols]

[0093] 1. Electrochemical cell 10 Container or can 14 Separator 24 Closed bottom end 40 Closure Assembly

Claims

1. A primary alkaline electrochemical cell, a) Container, and b) An electrode assembly disposed within the container and comprising a cathode, an anode, a separator positioned between the cathode and the anode, and a free electrolyte solution, Equipped with, The anode comprises: 1) solid zinc, 2) about 0.2 to 5 weight percent of solid particulate zinc oxide or solid particulate zinc hydroxide, 3) a gelling agent, and 4) an aqueous metal hydroxide electrolyte solution. The primary alkaline electrochemical cell contains dissolved zinc oxide or dissolved zinc hydroxide. Primary alkaline electrochemical cell.

2. The primary alkaline electrochemical cell contains a weight percentage of more than approximately 0.5% of total dissolved zinc oxide or total zinc hydroxide. The primary alkaline electrochemical battery according to claim 1.

3. The primary alkaline electrochemical cell contains more than approximately 4.5% by weight percent of total dissolved zinc oxide or total zinc hydroxide. The primary alkaline electrochemical battery according to claim 1.

4. The total weight percentage of dissolved zinc oxide or the total weight percentage of zinc hydroxide in the total electrolyte solution of the electrochemical cell is greater than or equal to 1.5 weight percent. The primary alkaline electrochemical battery according to claim 1.

5. The free electrolyte solution contains 0.1 to 6 weight percent of dissolved zinc oxide or dissolved zinc hydroxide. The primary alkaline electrochemical battery according to claim 1.

6. The primary alkaline electrochemical cell contains more than 2.0 weight percent of dissolved zinc oxide and more than 2.1 weight percent of whole zinc oxide. The primary alkaline electrochemical battery according to claim 1.

7. The anode contains more than 1.4% by volume of zinc oxide. The primary alkaline electrochemical cell contains more than 4.0% by weight of zinc oxide. The primary alkaline electrochemical battery according to claim 1.

8. The total electrolyte solution of the electrochemical cell is saturated with dissolved zinc oxide at a level higher than 40%. The primary alkaline electrochemical battery according to claim 1.

9. The free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide. The primary alkaline electrochemical battery according to claim 1.

10. The primary alkaline electrochemical cell contains a total weight percentage of zinc oxide higher than approximately 3.0%. The primary alkaline electrochemical battery according to claim 1.

11. The aforementioned primary alkaline electrochemical cell contains a total weight percentage of zinc oxide higher than approximately 4.0%. The primary alkaline electrochemical battery according to claim 1.

12. A primary alkaline electrochemical cell, a) Container, and b) An electrode assembly disposed within the container and comprising a cathode, an anode, a separator positioned between the cathode and the anode, and a free electrolyte solution, Equipped with, The anode comprises 1) solid zinc, 2) solid particulate zinc oxide or solid particulate zinc hydroxide, 3) a gelling agent, and 4) an aqueous metal hydroxide electrolyte solution. The primary alkaline electrochemical cell free electrolyte solution comprises dissolved zinc oxide or dissolved zinc hydroxide. The total weight percentage of dissolved zinc oxide or the total weight percentage of zinc hydroxide in the total electrolyte solution of the electrochemical cell is greater than or equal to 1.5 weight percent. Primary alkaline electrochemical cell.

13. The primary alkaline electrochemical cell contains a weight percentage of more than approximately 0.5% of total dissolved zinc oxide or total zinc hydroxide. The primary alkaline electrochemical battery according to claim 12.

14. The primary alkaline electrochemical cell contains more than approximately 4.5% by weight percent of total dissolved zinc oxide or total zinc hydroxide. The primary alkaline electrochemical battery according to claim 12.

15. The primary alkaline electrochemical cell contains more than 2.0 weight percent of dissolved zinc oxide and more than 2.1 weight percent of whole zinc oxide. The primary alkaline electrochemical battery according to claim 12.

16. The anode contains more than 1.4% by volume of zinc oxide. The primary alkaline electrochemical cell contains more than 4.0% by weight of zinc oxide. The primary alkaline electrochemical battery according to claim 12.

17. The free electrolyte solution contains 0.1 to 6 weight percent of dissolved zinc oxide or dissolved zinc hydroxide. The primary alkaline electrochemical battery according to claim 12.

18. The total electrolyte solution of the electrochemical cell is saturated with dissolved zinc oxide at a level higher than 40%. The primary alkaline electrochemical battery according to claim 12.

19. The anode contains about 0.2 to 5 weight percent of solid particulate zinc oxide or solid particulate zinc hydroxide. The primary alkaline electrochemical battery according to claim 12.

20. The primary alkaline electrochemical cell contains a total weight percentage of zinc oxide higher than approximately 3.0%. The primary alkaline electrochemical battery according to claim 12.

21. The aforementioned primary alkaline electrochemical cell contains a total weight percentage of zinc oxide higher than approximately 4.0%. The primary alkaline electrochemical battery according to claim 12.

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