BR112017015083B1 - ALKALINE CELL WITH IMPROVED RELIABILITY AND DISCHARGE PERFORMANCE - Google Patents

Abstract

ALKALINE CELL WITH IMPROVED RELIABILITY AND DISCHARGE PERFORMANCE. A negative electrode for an alkaline battery cell that includes zinc-based particles, wherein less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size larger than about 150 micrometers. An alkaline electrochemical cell including the negative electrode and a method for reducing outgassing of the electrochemical cell are also provided.

Description

[0001] This application claims the benefit of Interim Order No. 62/104,265, filed January 16, 2015, the entire contents of which are incorporated herein, by reference, in its entirety.

FIELD

[0002] The present technology generally refers to the field of zinc anodes for electrochemical cells. In particular, the technology refers to zinc anodes with improved reliability and discharge performance.

BACKGROUND

[0003] Battery gassing is a normal occurrence during battery charging and storage. Additionally, hydrogen gas generated during corrosion reactions can build up internal cell pressure, causing electrolyte leakage and disruption of cell integrity. This process is known as "gassing". Gas generation in alkaline batteries during storage is a result of hydrogen formation in the anode compartment driven by reduction reactions in metallic impurities present in the anode. It is improved after partial discharge due to the fact that the discharge removes the protective surface oxide film. Metallic impurities are inherent in the anode material as contaminants and can also originate from other battery materials such as the cathode, graphite, electrolyte, current collector or other additives used in the production of alkaline batteries. These impurities can be localized or randomly distributed.

[0004] The formation of gases can lead to several problems in a battery. For example, outgassing raises safety concerns due to the accumulation of explosive hydrogen gas produced. Gas formation also causes the consumption of active zinc material, thus permanently reducing battery capacity. Additionally, gas formation also consumes the water in the battery, which is needed for cathode reduction reactions, thus decreasing battery capacity. Proposed solutions to problems related to misaligned off-gassing include designing battery cells with safety vents that will release gas in the event of a pressure build-up, employing corrosion-resistant materials, adding gassing inhibitors or corrosion inhibitors, and minimize the presence of metallic impurities in the battery cell. Hydrogen gas generated during corrosion reactions leads to internal cell pressure buildup and ultimately to cell electrolyte leakage. Organic and inorganic inhibitors commonly used to suppress hydrogen gas generation during storage can drastically suppress discharge performance, making their benefit impractical.

SUMMARY

[0005] In one aspect, an electrode for an electrochemical cell is provided which includes zinc-based particles, wherein less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, having a particle size greater than about 150 micrometers.

[0006] In another aspect, an electrode for an electrochemical cell is provided which includes zinc-based particles of which about 10% to about 20% by weight of the total zinc in the electrode have a particle size greater than about 150 micrometers.

[0007] In one aspect, a gelled anode mixture is provided which includes zinc-based particles, wherein less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers; a gelling agent; an alkaline electrolyte; and a surfactant.

[0008] In one aspect, a method for reducing outgassing of an electrochemical cell subject to outgassing is provided, wherein the method includes using, as the active anode of said cell, a gelled anode that includes particles based on of zinc, wherein less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 illustrates the outgassing characteristics of an LR6 electrochemical cell caused by the content of coarse and fine zinc-based particles that have an apparent density of between about 2.73 and about 2.79 g/ ml.

[0010] Figure 2 represents the digital still camera (DSC) performance of the cell described in Figure 1.

[0011] Figure 3 illustrates the outgassing characteristics of a partial discharge cell of an LR6 electrochemical cell caused by the content of coarse and fine zinc-based particles that have an apparent density of about 2.55 g/ml.

[0012] Figure 4 represents the formation of undischarged cell gases from LR6 cells, as described in Figure 3.

[0013] Figure 5 represents the DSC performance of the cells described in Figures 3 and 4.

[0014] Figure 6 illustrates a contour plot showing the dependence of LR6 partial discharge (PD) cell gas formation on the dust content (particles smaller than 45 µm) and the apparent density (g/ml) of the dust of zinc.

[0015] Figure 7 illustrates a contour plot to show the dependence of DSC LR6 performance on the dust content (particles smaller than 45 µm) and the apparent density of the zinc dust after storing the cells for one week at 71.11 °C (160 °F).

[0016] Figure 8 illustrates the dependence of PD LR6 cell outgassing on surfactant content and gel KOH concentration.

[0017] Figure 9 illustrates the dependence of DSC performance on surfactant content and gel KOH concentration, as described in Figure 8.

[0018] Figure 10 is a graph illustrating the amperage of LR20 cells as affected by coarse and fine particle content.

[0019] Figure 11 is a graph illustrating the formation of partial discharge cell gases from LR20 cells, as described in Figure 10.

[0020] Figure 12 illustrates the aspect ratio concept.

[0021] Figure 13 illustrates the elongated nature and high aspect ratio of coarse particles of sizes greater than 150 micrometers.

[0022] Figure 14 is a schematic cross-sectional view illustrating an electrochemical cell of an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0023] Several modalities are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. An aspect described in conjunction with a particular modality is not necessarily limited to that modality and can be practiced with any other modality (or modality).

[0024] As used herein, the term "about" will be understood by people of ordinary skill in the art, and will vary to some extent depending on the context in which it is used. If there are uses of the term that are not clear to people of ordinary skill in the art, given the context in which it is used, "about" will mean up to plus or minus 10% of the particular term.

[0025] The use of the terms "a" and "a" and "a/o" and similar referents in the context of describing the elements (especially in the context of the following claims) shall be interpreted as covering both the singular and the plural, unless otherwise indicated herein or clearly contradicted by the context. The recitation of the ranges of values herein is intended merely to serve as a shorthand method for referring individually to each separate value that is in the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein may be performed in any proper order, unless otherwise indicated herein document or clearly contraindicated otherwise by the context. The use of any and all examples, or exemplary language (e.g., "how") provided in this document is merely intended to further explain the modalities and does not imply a limitation on the scope of the claims, unless otherwise indicated. No language in the specification should be construed as indicating any element not claimed to be essential.

[0026] Ratios, concentrations, amounts and other numerical data may be presented in this document in a strip format. It should be understood that such a range format is used merely for convenience and brevity, and should be interpreted flexibly to include not only numerical values explicitly reported as range boundaries, but also to include all individual numerical values or subranges. covered within that range as if each numerical value and subrange were explicitly reported. For example, 5 to 40 mol% should be interpreted to include not only the explicitly stated limits of 5 to 40 mol%, but also to include subranges such as 10 mol% to 30 mol%, 7 mol% to 25 mol%, and so on, as well as individual amounts, which include fractional amounts, within specified ranges, such as 15.5 mol%, 29.1 mol%, and 12.9 mol%, for example.

[0027] As used herein, the term "zinc anode" refers to an anode that includes zinc as an active anode material.

[0028] As used herein, "fines" are particles that pass through a standard 200 mesh sieve in a normal sieving operation (ie, with the sieve shaken by hand). The term "Dust" consists of particles that pass through a standard 325 mesh sieve in a normal sieving operation. The term "Coarse Particle" means particles that do not pass through a standard 100 mesh sieve in a normal sieving operation. The mesh sizes and corresponding particle sizes as described here apply to a standard test method for sieving analysis of metal powders that is described in ASTM B214.

[0029] As used herein, the term "aspect ratio" refers to the dimension determined by the ratio of the length of the longest dimension of the particle to the relative width of the particle.

[0030] Alkaline batteries have been improved over the years to improve their discharge capacity as well as improve their reliability. For example, a practice known in the art to improve high rate discharge performance in alkaline batteries is to increase the content of fine zinc anode particles, particles that exceed a sieve size of 200 mesh (75 µm). This approach generally results in cell-enhanced gas formation due to the correspondingly enlarged anode surface area of the added fraction of fine particles. To control cell reliability, a common practice in the art is to use organic and/or inorganic gas formation inhibitors. Additionally, the anode zinc dust can be conveniently alloyed with well known inhibiting alloying elements.

[0031] Zinc anode gels of alkaline electrochemical cells are prone to electrochemical corrosion reactions when battery cells are stored in the undischarged or partially discharged condition due to zinc anode corrosion, an oxidation reaction that leads to dissolution of zinc and formation of zincate, as shown in (1). This reaction is balanced by a cathode reaction that leads to the generation of hydrogen, as shown in (2), which results in the build-up of internal cell gas pressure during storage. The rate of the gas generation reaction is determined by a number of factors such as available active zinc surface area, the presence of metallic impurities, the gel KOH concentration and the nature of the native oxide film on the zinc surface. The surface area affected by zinc particle size distribution, particle shape and particle surface morphology. Metallic impurities are inherent in the anode material as contaminants and can also originate from other battery materials such as the cathode, graphite, electrolyte, anode current collector, metal battery housing and other additives. used in the production of alkaline batteries. The native oxide film on zinc protects its surface from oxidation if battery cells are stored in the undischarged condition. However, partial discharge removes the compact protective surface oxide film and exposes metallic impurities to the corroding electrolyte. Zn + 4OH- → Zn(OH)42- + 2e- (1) 2H2O + 2e-→ H2+ 2OH- (2)

[0032] Two effective methods to improve high rate cell discharge performance are anode surface enlargement and the use of low KOH concentrations in the anode gel. The performance benefits of adjusting the KOH concentration were demonstrated in Document 1 (Document No. US7226696 B2). Document 1 acknowledges that cell performance is improved using gel KOH concentrations below 34%, such as below 30% or below 28%, generally at the expense of increased cell gassing. Similarly, high rate discharge performance can be improved by increasing the content of fine zinc particles, i.e., particles beyond a 200 mesh sieve size, as reported in Document 2 (Document No. US 8343658 B2 ). Simultaneous adjustments to zinc particle size and zinc fine particle content, as well as anode gel KOH concentration to optimize discharge performance, can be expected to also result in excessive cell gas generation, which compromises cell reliability. Therefore, it is desirable to find means to suppress cell gas generation in battery cells that have increased percentage of fine particles and optimized levels of gel KOH concentrations. It is an object of the present invention to provide a means to prevent the adverse gassing effects of using high percentage of fine zinc particles and optimized anode gel KOH concentrations.

[0033] Zinc powders for alkaline batteries typically contain particles that have a broad particle size distribution and that is in the range of a few micrometers to over 1,000 micrometers (µm). The particle size distribution contains different weight percentages of particles smaller than 45 µm (dust), particles smaller than 75 µm (fine particles), particles larger than 150 µm (coarse particles) and particles in sizes between 75 µm and 150 µm . In some embodiments, coarse particles include particles having a size from about 150 µm to about 1000 µm, 150 µm to about 177 µm, about 177 µm to about 354 µm, about 354 µm to about 707 µm µm, about 707 µm to about 2500 µm, about 2500 µm to about 6730 µm, and ranges between any two of these values or less than any of these values. Zinc-based particles can be of various shapes including, but not limited to, spherical, bone, acicular and elongated type. Particle shape can also be defined by the corresponding aspect ratio, a dimension determined by the ratio of the length of the longest particle dimension to the relative width of the particle. Conventional zinc powders contain particles that have a broad particle size distribution that ranges from a few microns to over 1,000 microns, with the weight distribution being heaviest with particles larger than 150 microns. Cells having such conventional zinc powders have sufficient amounts of electrolyte and KOH concentration to supply OH ions and water which is consumed in corrosion reactions during storage, as described above. Additions of relatively large amounts of organic and/or inorganic inhibitors are generally used to suppress undesirable reactions that can lead to gas generation during shelf storage.

[0034] It was found here that by controlling the particle size distribution, particularly by minimizing the coarse particle content of zinc-based particles used as anode material in batteries, improvements in reliability and performance are provided discharging such batteries. This effect is believed to be provided by reducing battery outgassing during storage.

[0035] Accordingly, in one aspect, a negative electrode for an alkaline battery cell is provided, wherein the coarse particle content is less than 20% of zinc-based particles by weight relative to the total zinc in the electrode , that is, less than 20% of the zinc-based particles, by weight of the total zinc in the electrode, have a particle size greater than about 150 micrometers. This includes embodiments where less than 18%, less than 15%, less than 12%, less than 10%, less than 8%, or less than 5% of the zinc-based particles, by weight, relative to the zinc total on the electrode, have a particle size greater than about 150 micrometers.

[0036] In some embodiments, the negative electrode includes zinc-based particles, wherein about 1% to about 30% of the zinc-based particles, by weight, relative to the total zinc in the electrode, are coarse particles that have a particle size greater than about 150 micrometers. This includes embodiments where about 5% to about 25%, about 8% to about 22%, about 10% to about 20%, or about 12% to about 18% and ranges in between any two of these values, or less than any one of these values, of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers. In some embodiments, about 0.1% to about 2%, about 2% to about 6%, about 4% to about 9%, or about 5% to about 10%, of the particles based on of zinc, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers. In some embodiments, less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers. In some embodiments, about 10% or more of the 20% zinc-based particles have a particle size between about 150 micrometers to 177 micrometers. In some embodiments, about 10% of the 20% zinc-based particles have a particle size between about 150 micrometers to 177 micrometers.

[0037] In some embodiments, the zinc-based particles are zinc alloy particles. The zinc alloy may include alloying elements intended to raise the overall potential for evolution of hydrogen to minimize its formation at cathode sites. In some embodiments, the zinc can be alloyed with one or more metals selected from indium, bismuth, calcium, aluminum, lead and phosphorus. In some embodiments, the alloying metal is bismuth. Concentrations of zinc-alloyed metals can range from about 20 ppm to about 750 ppm. In some embodiments, the alloying metals are present at a concentration of about 50 ppm to 550 ppm. Typically, alloying powders can include from about 0.01% to about 0.5% by weight of alloying agent independently of, or in combination with, from about 0.005% to about 0.2% by weight. of a second alloying agent such as lithium, calcium, aluminum and the like.

[0038] Zinc-based particles can have an average particle size of about 70 micrometers to about 175 micrometers. This includes an average particle size of about 75 micrometers, about 80 micrometers, about 85 micrometers, about 90 micrometers, about 100 micrometers, about 110 micrometers or about 120 micrometers. In some embodiments, the zinc-based particles are zinc alloy particles that have an average particle size of about 90 micrometers.

[0039] In addition to controlling the coarse particle content, the amount of particles and dust can also be optimized to achieve the desired reduction in gas formation and improvement in discharge properties. Thus, in one embodiment, about 10% to about 90% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size of less than about 75 micrometers. This includes embodiments where about 15% to about 80%, about 20% to about 70%, about 30% to about 60%, or about 40% to about 50% and ranges in between any two of these values, or less than any one of these values, of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size of less than about 75 micrometers. In some embodiments, from about 20% to about 70% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size of less than about 75 micrometers. In other embodiments, about 20% to 45% by weight of the total zinc in the electrode has a particle size of less than about 75 micrometers. In some embodiments, about 20% to about 40% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size of less than about 75 micrometers. In some embodiments, from about 1% to about 15% by weight, based on the total zinc in the electrode, has a particle size of less than 45 micrometers. In other embodiments, about 1% to about 10% by weight, based on the total zinc in the electrode, has a particle size of less than about 45 micrometers. In other embodiments, about 1% to about 7% by weight, based on the total zinc in the electrode, has a particle size of less than about 45 micrometers.

[0040] In some embodiments, less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers, about 20% to about 70% of the zinc-based particles, by weight relative to the total zinc in the electrode, have a particle size of less than about 75 micrometers. In some embodiments, about 1% to 15% by weight of total zinc in the electrode has a particle size less than about 45 micrometers, about 20% to 50% by weight of total zinc in the electrode, have a particle size of less than about 75 micrometers, and about 10% to 20% by weight of the total zinc in the electrode have a particle size of greater than about 150 micrometers. In other embodiments, less than 10% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers, about 20% to about 70% of the particles at Base zinc, by weight relative to the total zinc in the electrode, have a particle size of less than about 75 micrometers. In some embodiments, about 4% to about 9% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers, about 20% to about 70% of the zinc-based particles, by weight of the total zinc in the electrode, have a particle size of less than about 75 micrometers. In some embodiments, between 10% and 20% by weight of the particles have a particle size greater than 150 micrometers and greater than 20% by weight of the particles have a particle size smaller than 75 micrometers. In other embodiments, between 10% and 20% by weight of the particles have a particle size greater than 150 micrometers and between 20% and 50% by weight of the particles have a particle size smaller than 75 micrometers. In some embodiments, between 4% and 9% by weight of the particles have a particle size greater than 150 micrometers and greater than 20% by weight of the particles have a particle size smaller than 75 micrometers.

[0041] The level of elongation of different particle size fractions affects the interlocking of zinc anode particles and can be measured optically. Images of several hundred zinc-based particles from each individual sieve fraction can be imported into software that has the ability to optically measure large numbers of these particles. Mathematical functions can be applied to optical images of zinc fractions to quantify the level of particle elongation. The aspect ratio, as defined as a function of the ratio of the major axis to the minor axis of the ellipse equivalent for the object (Figure 12), can be determined for each particle in a given fraction and the average of the aspect ratio. aspect ratio for each zinc sieve fraction can be calculated. An average aspect ratio of 1 implies that, on average, the particles are spherical. Any value greater than 1 implies some level of stretching. In addition to aspect ratio, zinc particle sphericity, as defined as a function of perimeter squared divided by four times the pi value multiplied by particle area (sphericity = P2 * 4pA). An average sphericity of 1 implies that, on average, the particles are spherical. Coarse particles with a high aspect ratio or sphericity function provide an improved level of particle-to-particle contact. Figure 13 demonstrates the elongated nature of coarse particles larger than 150 microns.

[0042] The zinc-based particles of the present technology have a high aspect ratio. In some embodiments, the zinc-based particles have an aspect ratio of about 5 or less, about 4.5 or less, about 4 or less, about 3 or less, about 2.5 or less, about 2 or less or about 1.5 or less. In some embodiments, zinc-based particles of the present technology have an aspect ratio of from about 1 to about 5. This includes an aspect ratio of about 1 to about 5, from about 1.5 to about 5. from about 4.5, from about 1.8 to about 4.2, from about 2 to about 4.0, from about 2.5 to about 3.5, or about 2.8 to about of 3.8, and ranges between any of these values or less than any of these values. In some embodiments, the zinc-based particles have an aspect ratio of from about 1.85 to about 4.15.

[0043] The zinc-based particles of the present technology have a sphericity of at least about 0.8. This includes a sphericity of at least about 0.9, at least about 1.0, at least about 1.2, at least about 1.5, at least about 1.8, or at least about 2 ,0. In some embodiments, the zinc-based particles have a sphericity of at least about 1.5.

[0044] In some embodiments, the zinc-based particles have a bulk density of about 1.5 g/cm 3 to about 4.5 g/cm 3 . This includes a bulk density of about 1.8 g/cm3 to about 4.0 g/cm3, about 2.0 g/cm3 to about 3.8 g/cm3, about 2.5 g/cm3 to about 3.5 g/cm 3 , or about 2.8 g/cm 3 to about 3.0 g/cm 3 , and ranges between any two of these values or less than any of these values. In some embodiments, the zinc-based particles have a bulk density of from about 2.40 g/cm3 to about 3.15 g/cm3.

[0045] In some embodiments, the negative electrode or anode is a gelled anode. A suitable gelled anode according to the technology may include a metal alloy powder such as a zinc alloy optionally with other components such as a gelling agent, surfactants, superabsorbents, inhibitory additives and an alkaline electrolyte. In one aspect, there is provided a gelled anode mixture which includes zinc-based particles wherein less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a size of particle larger than about 150 micrometers; a gelling agent; an alkaline electrolyte that includes a hydroxide material; and a surfactant.

[0046] Any suitable gelling agent can be used as long as it does not depart from the scope of the present disclosure. Suitable gelling agents include, but are not limited to, polyacrylic acids, grafted starch materials, salts of polyacrylic acids, crosslink-typed branched polyacrylates, carboxymethyl cellulose, natural gum and the like or combinations thereof. Examples of suitable polyacrylic acids include Carbopol 940 and 934 (available from B.F. Goodrich) and Polygen 4P (available from 3V). An example of a polyacrylic acid salt is Alcosorb Gl (available from Ciba Specialties). An example of a grafted starch material is Waterlock A221 (available from Grain Processing Corporation). In one embodiment, a suitable gelling agent is a polyacrylic acid polymer. In one embodiment, the polyacrylic acid is a cross-linked polyacrylic acid polymer. In some embodiments, the gelling agent is an agent other than the sodium polyacrylate gelling agent. In some embodiments, the gelling agent does not include sodium polyacrylate gelling agent. A gelled anode mixture, a gelled anode, and an electrochemical cell containing the gelled anode may have the structures and may be prepared as described in U.S. Patent 8,728,659 B2, incorporated by reference herein in its entirety.

[0047] The amount of gelling agent may range from about 0.05% to about 5% of the total mass of the anode. In some embodiments, the gelling agent is present in an amount of from about 0.1% to about 1% of the total mass of the anode. In one embodiment, the gelling agent can be present in an amount of from about 0.1% to about 0.8%, about 0.2% to about 0.7, or about 0.3% to about of 0.6%, based on the total weight of the anode gel.

[0048] Along with the anode active, the anode may include an electrolyte therein to supply water for the galvanic corrosion reaction. The electrolyte desirably has a high ionic conductivity. Generally, the electrolyte is an alkaline electrolyte, such as an aqueous solution of an alkali metal hydroxide, but may also include other electrolytes known to those of ordinary skill in the art, for example, quaternary ammonium electrolytes. Examples of alkali metal hydroxide include potassium hydroxide, lithium hydroxide or sodium hydroxide solution. In some embodiments, the alkali metal hydroxide is potassium hydroxide.

[0049] The anode that includes zinc-based particles of the present technology provides optimal performance even with an electrolyte that has low hydroxide concentration. For example, the hydroxide concentration or content in the electrolyte can be from about 1% by weight to about 60% by weight. This includes from about 5% by weight to about 50% by weight, from about 10% by weight to about 45% by weight, from about 15% by weight to about 40% by weight, from about 20% by weight to about 35% by weight, and from about 25% by weight to about 30% by weight and ranges between any two of these values or less than any of these values. In some embodiments, the gelled anode has a hydroxide content of 20% by weight to 34% by weight. In some embodiments, the gelled anode has a hydroxide content of less than about 60% by weight. This includes a hydroxide content of less than about 50% by weight, less than about 40% by weight, less than about 30% by weight, less than about 20% by weight and less than about 10% by weight. .

[0050] In some cases, the electrolyte may contain dissolved salts, oxides or hydroxides of bismuth, tin, indium, mercury, lead, cadmium or thallium. Additionally, the electrolyte may include a dissolved cation or anode metal anion (for example, an aluminum oxide, sodium aluminate, potassium aluminate, a zinc oxide, a zinc hydroxide, or calcium salts). In some embodiments, the electrolyte may additionally contain a corrosion inhibitor such as a quaternary ammonium salt, or a nonionic, anionic, or cationic surfactant. In some embodiments, when zinc is the anode active agent, the electrolyte may include a small amount of zinc oxide to prevent open circuit oxidation and stabilize the zinc surface and reduce gassing. Zinc oxide can be present in an amount from about 1% to about 10% by weight of the anode. This can include from about 1% to about 8% or 1% to about 5% by weight of the anode. In one embodiment, zinc oxide can be present in an amount of about 1%, about 1.5%, about 2%, about 2.5%, about 3%, about 3.5% , or about 4%, by weight of the anode, and ranges between any two of these values or less than either of these values. In some embodiments, the amount of zinc oxide can be from about 0.1% by weight of the anode to about 2% by weight of the anode. In one embodiment, the zinc oxide can be present in an amount of about 2% by weight of the anode.

[0051] In addition to the electrolyte, organic surfactants and inorganic corrosion inhibiting agents can also be added to the anode. It is believed that surfactants act on the anode-electrolyte interface, forming a hydrophobic film that protects the active surface of the anode during storage. The inhibition effectiveness of surfactants to increase the corrosion resistance of the active anode depends on their chemical structure, concentration, and their stability in the electrolyte. Exemplary surfactants include organic phosphate esters, such as the ethylene oxide adduct type disclosed by Rossler et al. in U.S. Patent 4,195,120, or surface active heteropolar ethylene oxide additive which includes organic phosphate esters disclosed by Chalilpoyil et al. in U.S. Patent 4,777,100, both incorporated herein by reference, an amphoteric surfactant, sulfonated or sulfated organic acid surfactant, diethylenetriamine, hexyl diphenyl oxide sulfonic acid, and commercially available surfactants such as Rhodafac RM-510, Rhodafac RA-600, Rhodafac RS-610, Witconate 1840X, and Mafo 13 MODI, or a combination of any two or more thereof. In some embodiments, the surfactant may include an amphoteric fluorosurfactant such as, for example, CHEMGUARD® S-111, CHEMGUARD® S-500, CAPSTONE® FS-50, CAPSTONE® FS-51, APFS-14, DYNAX DX3001, ZONYL® FSK , ZONYL® FS-500, or a combination of any two or more thereof. In some embodiments, the combination of components in the anode provides an improved improvement in cell voltage and cell performance. In some embodiments, the surfactant is an organic phosphate ester surfactant, a polyethylene glycol ether, an ethoxylated alkylphenol, tallow amines, diethylenetriamine, an amphoteric surfactant, a sulfonated organic acid surfactant, a sulfated organic acid surfactant, sulfonic acid of hexyl diphenyl oxide, or a combination of any two or more thereof.

[0052] The surfactant may be present in an amount from about 1 ppm to about 400 ppm. This includes from about 5 ppm to about 300 ppm, from about 10 ppm to about 150 ppm, from about 20 ppm to about 100 ppm, or from about 25 ppm to about 50 ppm and ranges between any two of these values or less than any of these values. The total amount of surfactant is typically in the range of about 0.0001% to about 10% by weight of the anode. This includes from about 0.005% to about 5% by weight, about 0.001% to about 1% by weight, about 0.005% to about 0.1% by weight, or about 0.01% to about 0.5% by weight of the anode weight and ranges between any two of these values or less than any of these values. In some embodiments, the total amount of surfactant can range from about 0.001% to about 0.04% by weight of the anode.

[0053] Dilute solutions of potassium hydroxide are generally added to the anode gel, the cathode, and the paper separator. The KOH solution added to the paper separator is done in advance to pour the anode gel into the anode compartment to allow imbibition of this electrolyte, also called pre-wetting, by the separator and the cathode material in contact with the housing. of battery. The concentration of KOH present in the anode gel, the prewet, and the cathode material can have an impact on the discharge rate capability of the battery cell.

[0054] Other inhibiting additives such as, for example, indium hydroxide or silicates such as sodium silicates may also be present in the electrolyte solution. The amount of inhibitor added to the cell can be expressed as a function of the weight of metal (eg zinc) in the anode or the weight of the anode gel, as done in the examples discussed below. RM-510 is preferably added in the range of 0.0004% to 0.015% relative to the weight of the gelled anode, and more preferably between 0.0001% and 0.0075%. Indium hydroxide is preferably added at concentrations that are in the range of 0.003% to 0.03%. Such additives or inhibitors can be added to the gelled anode mixture independently or in combination according to any of the embodiments described in this disclosure, unless otherwise specified.

[0055] The technology provides a gelled anode that has yield strength greater than about 500 N/m2. This includes yield stress from about 500 N/m2 to about 4000 N/m2, from about 600 N/m2 to about 3500 N/m2, from about 1000 N/m2 to about 2500 N/m2 , or from about 1500 N/m2 to about 2000 N/m2 and in the range of any two of these values or less than any of these values. In some embodiments, the gelled anode has an elastic limit value of from about 600 N/m 2 to about 3500 N/m 2 .

[0056] Gelled anode materials have a suitable viscosity required to provide the improved cell discharge performance. For example, the viscosity can be from about 10 Pa.s (10,000 cps) to about 200 Pa.s (200,000 cps), from about 25 Pa.s (25,000 cps) to about 150 Pa.s (150,000 cps). cps), or from about 50 Pa.s (50,000 cps) to about 100 Pa.s (100,000 cps) and ranges between any two of these values or less than any of these values at about 25°C. In some embodiments, the gelled anode material has a viscosity of about 25 to 150 Pa.s (25,000 to 150,000 cps) at 25°C.

[0057] The gelled anode of the disclosed embodiments can be included as a component in a conventional electrochemical cell such as batteries. These include, for example, galvanic cells, as in metal-air cells, eg zinc-air cell, as well as alkaline cylindrical cells, eg zinc oxide-metal cell. The metal-air cells comprising the anode described herein can usefully be constructed as button-type cells for various applications, such as listening aid batteries and in wristwatches, clocks, timers, calculators, laser, toys and other innovations. However, it should be understood that the present technology has application for electrochemical cells other than button cells. For example, the anode can find application in any metal-air cell with the use of flat, flexed or cylindrical electrodes. In addition to cylindrical metal-metal oxide cells and metal-air cells, the anode material is applicable to those shaped for AA, AAA, AAAA, C or D cells. The use of anode material as components in other forms of electrochemical cells also is contemplated.

[0058] Accordingly, in one aspect, there is provided an alkaline cylindrical electrochemical cell that includes a positive current collector; a cathode in contact with the positive current collector; a negative current collector; an anode in contact with the negative current collector, the anode including a gelled mixture including zinc-based particles; and a separator between the cathode and anode. In some embodiments of the electrochemical cell, less than 20% of the zinc-based particles, by weight, relative to the total zinc in the gelled anode mixture, are coarse particles and have a particle size greater than about 150 micrometers. In other embodiments, the electrochemical cell includes a zinc anode in which about 10% to about 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers. In some embodiments, the electrochemical cell includes a zinc anode in which about 4% to about 9% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers.

[0059] An exemplary embodiment of a metal-metal oxide battery cell of the present disclosure may be as illustrated in Figure 14, although other designs should not be so limited. Referring initially to Figure 14, an axially extending cylindrical cell 18 has a positive terminal 21, a negative terminal 23, and a positive current collector in the form of an unlined cylindrical steel container 20. The container 20 is initially closed at its positive end 25 proximal to the positive terminal 21 and is open at its end proximal to the negative terminal 23 so that the negative end of the container is crimped to close the cell 18, as is generally understood by a person skilled in the art.

[0060] At least one or more cylindrical annular cathode rings 24, formed so that their outside diameters at their peripheral side walls are slightly larger than the inside diameter of the positive current collector 20, are forced into the positive current collector. A coating 22, desirably carbon, may be applied to the radially inner surface of the vessel 20 to improve electrical contact between the cathode rings 24 and the vessel. The installation of the cathode rings 24 forms pressure contact with the coating 22. The cathode 24 additionally has an inner surface 27 which defines a centrally shaped void 28 in a cylindrical cell, within which the anode 26 is disposed.

[0061] A spacer 32 is arranged between the anode 26 and the cathode 24. The anode 26, which is placed inside the cathode rings 24, is generally cylindrical in shape and has an outer peripheral surface that engages with the inner surfaces of a separator 32 and comprises gelled zinc according to at least one aspect of the present invention. The separator is disposed adjacent the inner wall 27 between the cathode 24 and the anode 26. An alkaline aqueous electrolyte, typically comprising potassium hydroxide and water, wets at least the anode 26, the cathode rings 24 and the separator 32.

[0062] A microsphere 30 is rolled into the container next to the negative end 41 to support a sealing disc 34. The sealing disc 34, which has a negative current collector 36 extending therethrough, is placed at the open end of the container 20 and in contact with the microsphere 30. The open negative end 41 of the container 20 is sealed over the sealing disk 34 thereby compressing it between the seal and the microsphere 30 to close and seal the cell. An insulating washer 38 with a central opening is placed over the sealed end of the cell so that the negative current collector end 36 projects through the opening. A contact spring 40 is attached to the end of the negative current collector 36. The negative terminal cap 42 and the positive terminal cap 44 are placed in contact with the contact spring 40 and the positive current collector 20, respectively, and an insulating tube 46 and steel housing 48 may be placed around the cell 18 and sealed at its ends to hold the terminal covers in place. It should be noted that the steel housing 48 and insulating tube 46 can be eliminated to increase the internal volume for the cell which can be occupied by active ingredients. Such an arrangement is described in U.S. Patent 5,814,419 assigned to Rayovac Corporation, the disclosure of which is incorporated herein by reference.

[0063] The cathode of the electrochemical cell may include any active cathode material generally recognized in the art for use in alkaline electrochemical cells. The cathode active material can be amorphous or crystalline, or a mixture of amorphous and crystalline. For example, the cathode active material may include or be selected from a copper oxide, a manganese oxide, such as electrolytic, chemical, or natural type (e.g., EMD, CMD, NMD, or a mixture of any two or more thereof), a silver oxide and/or a nickel oxide or hydroxide, as well as a mixture of two or more of these oxides or hydroxide. Suitable examples of positive electrode materials include, but are not limited to, MnO2 (EMD, CMD, NMD, and mixtures thereof), NiO, NiOOH, Cu(OH)2, cobalt oxide, PbO2, AgO, Ag2O, Ag2Cu2O3, CuAgO2, CuMnO2, CuMn2O4, Cu2MnO4, Cu3-xMnxO3, Cui-xMnxO2, Cu2-xMnxO2(where x < 2), Cu3-xMnxO4(where x < 3), Cu2Ag2O4, or a combination of any two or more thereof .

[0064] The electrochemical cell may include a separator between the cathode and zinc anode, which is designed to prevent short circuit between the two electrodes. Generally, any separator material and/or configuration suitable for use in an alkaline electrochemical cell, and with the cathode and/or anode materials set forth herein above, may be used in accordance with the present disclosure. In one embodiment, the electrochemical cell includes a sealed separator system that is disposed between a gelled anode of the type described herein and a cathode. The separator can be made of any alkali resistant material, including, but not limited to, polyvinyl alcohol, Tencel, mercerized wood pulp, polypropylene, polyethylene, cellophane, and combinations thereof. In some embodiments, the separator includes polypropylene.

[0065] In another embodiment, the electrochemical product can be prepared by any means known in the art, provided that the resulting cell does not conflict with the disclosures presented herein. Accordingly, the present disclosure includes a method for preparing an electrochemical cell that includes the components and their respective concentrations as discussed throughout this disclosure.

[0066] By adjusting the zinc anode particle size distribution to control the dust content, fine and coarse particle size, as described in this document, improved reliability in terms of suppressed cell outgassing and leakage cell size, along with improved high discharge rate capability, can be achieved. The advantages of the present technology include, for example, maintaining or suppressing cell reliability and cell gassing while simultaneously improving capabilities for high rate discharge performance, reduction of drop test failures, improvement in battery, closed circuit voltage and decrease in cell impedance. Using optimized percentage amounts of coarse particles minimizes early hydrogen gas formation with increased anode zinc surface area. Another advantage is that, with the zinc-based particles of the present technology, the electrolyte included in the anode mixture can have a reduced hydroxide concentration. The present technology therefore provides improved high rate cell discharge performance through enlarging the anode surface and using low KOH concentrations in the anode gel. The foreign metallic impurities inherent in anode gels can be used as cathode sites to promote the reduction reactions that lead to gas generation balanced by oxidation (corrosion) of the active zinc material. As described above, particle-to-particle contact between zinc anode particles is improved in the presence of coarse particles that have a relatively high aspect ratio. Reducing the percentage of coarse particles in the anode gel suppresses contact with contaminated particles, thereby minimizing the impact of adverse gas formation from impurities present in the anode gel.

[0067] In one aspect, a method for reducing outgassing of an electrochemical cell subjected to outgassing is provided, wherein the method includes providing as the active anode of said cell a gelled anode that includes the particles based on zinc, in which less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers while simultaneously limiting the dust particle content to less than 10 % of zinc-based particles. In some embodiments, the method includes a zinc anode provided as the active anode of said cell, a gelled anode including zinc-based particles, wherein about 10% to about 20% of the zinc-based particles, in weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers. In some embodiments, the method includes providing, as the active anode of said cell, a gelled anode that includes zinc-based particles, wherein about 4% to about 9% of the zinc-based particles, by weight, by relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers. In some embodiments, gassing is reduced by about 10% to about 50%. This includes a reduction in gas formation from about 10% to about 45%, from about 15% to about 40%, from about 20% to about 40%, or from about 30% to about 40%, and is in the range of any two of these values or less than any of these values. In some embodiments, off-gassing is reduced from about 10% to about 50% in battery cells that have zinc powders that contain less than 20% coarse particles relative to conventional battery cells that have an active anode which include zinc-based particles with apparent densities between 2.50 and 3.0 g/ml and content of coarse particles that have sizes greater than 150 micrometers with amounts between 20% and 60% by weight in relation to the total zinc electrode . In some embodiments, less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than about 150 micrometers, and less than 10% of the zinc-based particles, by weight, relative to the total zinc in the electrode, they have a particle size of less than about 45 micrometers.

[0068] The present technology recognizes that factors that control cell performance include parameters such as anode surface area, gel KOH concentration, and inhibitor content, among others. Specifically, increasing the active anode electrode surface area provides sufficient active reaction sites needed to accompany the cathode reaction at high discharge rates. Consequently, the cells are supplied as having a predetermined amount of zinc metal or alloy particles added to the anode gel. The present technology refers to the use of zinc-based particles that have a consistent particle size distribution to provide maximum performance without adverse effects on cell reliability. Thus, in one embodiment, the zinc-based particles can include dust contents of less than about 15%, such as less than 7% by weight of total zinc in the anode, for example, between the range of 2% and 6%, or between 4% and 6%. It can be noted that the smaller particles further increase the effective surface area of the anode. In other embodiments, the zinc-based particles can include the amount of fine zinc particles greater than 20%, while the zinc-based particles having a size above 150 microns can be present at about less than 20% in weight, for example, between about 1% and 9%, between about 10% and 20%, and between about 12% and 18%, by weight, of total zinc present in the anode; and zinc-based particles having a size between 75 microns and 150 microns may be present in the remaining percentage fraction of the zinc dust distribution.

[0069] The present technology recognizes that alkaline anode gels, whose zinc particle size distribution includes coarse particles in percentages described in this document, minimize the generation of cell gas caused by undesirable corrosion reactions induced by the presence of impurities metallic; and the use of zinc dust and fine zinc particles is intended to improve surface area and increase high rate discharge performance. Cell performance advantages can also be enhanced under conditions where the anode gel has an electrolyte (KOH) concentration of less than 30%, for example between 25% and 30%.

[0070] Although improved cell performance has been correlated to preferred size ranges of zinc dust, fine particles, and coarse particles in combination with defined KOH concentrations, a person skilled in the art would recognize the benefits of adding fine zinc particles and an optimal KOH concentration, or individually. Accordingly, the present technology includes, within its scope, the addition of optimum percentages of dust, fine and coarse particles to an anode gel having zinc particle sizes within any one of the ranges stated above individually or in combination with any of the KOH concentrations stated above. Similarly, the present technology includes within its scope an anode gel having a KOH concentration within any of the ranges stated above individually or in combination with dust, fine and coarse particles having a size within any one of the ranges stated above. Additionally, the zinc dust content, fine particles, coarse particles and KOH concentrations stated above can be implanted into a cell independently or in combination with the inhibitors described herein, e.g. a phosphate surfactant and/or inorganic additives. .

[0071] The present technology thus described, in general, will be understood more readily by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present technology.

EXAMPLES

[0072] In the Examples presented below, the electrochemical cells of the present disclosure were tested for DSC performance, drop test amperage (both before and after the drop), partial discharge cell outgassing, non-drop cell outgassing, discharged and conditions after storage. Gelled anodes were prepared in accordance with the improvements of the present disclosure.

[0073] The gel viscosity is measured using a digital Brookfield viscometer and Teflon-coated spindle No. 06 at 4 rpm. During measurement, the reading is allowed to stabilize for 5 minutes before recording the viscosity value.

[0074] For measuring the elastic limit value, measure the gel viscosity values at 1.0 rpm (R1) and 0.5 rpm (R2), respectively, the elastic limit value is calculated using the formula: elastic limit value = (R2-R1)/100.

MEASUREMENT OF CELL GAS FORMATION

[0075] Figure 1 shows a graph of cell gassing from alkaline (AA) LR6 cells after partial discharge and storage at 71.11 °C (160 °F) for one week. Partial discharge for this cell size was performed at a constant current of 250 mA for 1.80 hours, after which the cells were stored in a dry oven at 71.11 °C (160 °F). The LR6 cell anode gels had a gel KOH concentration of 26.5% and the corresponding zinc loading was 70%, relative to the weight of the gel. The zinc powder had bismuth and indium as major alloying elements at a concentration of about 200 ppm and the corresponding bulk densities were in the range between 2.73 and 2.79 g/ml. Along with RM510 at a concentration of 35 ppm, an additional inorganic inhibitor was also tested to determine its impact on performance and reliability. The data in Figure 1 compare cell outgassing of cells made with zinc powders that have a coarse particle content of 15% and 18% (and fines of 28% and 34%, respectively), versus formation of cell gases from control cells made with a zinc powder that has a coarse particulate content at 41% (and fine particulate content at 17%). At least about 10% in cell gas suppression is observed relative to the control cell which has 41% coarse particles as seen with cells containing organic inhibitor RM510.

DSC PERFORMANCE MEASUREMENT

[0076] Electrochemical cells can be tested according to various methods under American National Standards Institute (ANSI). These tests include determining that cell performance/longevity under cell pulse discharge (i.e., repeated application of 1500 mW over a 2 second period and 650 mW over a 28 second period over a five minute period every hour until the cell voltage reaches the endpoint voltage of 1.05 V). The test described is known as a digital still camera (DSC). The DSC test data corresponding to the cells described in Figure 1 are shown in Figure 2. As seen from Figure 2, the DSC performance of cells having coarse particle content of zinc at 15% and 18% increased by about 8% and 14% compared to that of control cells that have 41% coarse-grained zinc. The increased performance is attributed to the higher particulate content (28% and 34%) over that of the control (17%). Regardless of the higher fine particle content at 28% and 34%, the respective cell outgassing was lower than that for controlling cells having 17% fine particles (41% coarse particle content). The data in Figures 1 and 2 indicate that the presence of an additional inorganic inhibitor (identified as an additive) tends to suppress cell gas formation at the expense of suppressing discharge performance.

[0077] Figure 3 and Figure 4 summarize the partial discharge and undischarged cell gassing measured from LR6 cells stored at 71.11 °C (160 °F) for one week. The respective gel KOH concentration was 26% and zinc loading was 70%. The alloy powder contained 200 ppm bismuth and 200 ppm indium and the bulk density of the powders was about 2.55 g/ml. The concentration of inhibitor in the anode gel was 46 ppm of RM510. In agreement with the outgassing results seen in Figure 1, the cell outgassing data shown in Figures 3 and 4 indicate suppressed cell outgassing with powder that has a low coarse particle content such as 16 %, relative to the control powder with the highest coarse particle content level, such as 25%, regardless of whether it is under undischarged (Figure 4) or partially discharged (Figure 3) conditions. The gassing suppression is as great as 33% after partial discharge and as great as 50% when cells are stored in an undischarged mode. Figure 5 shows the corresponding performance data for cells whose outgassing results are shown in Figures 3 and 4. Equal or improved performance is seen from cells with powders that have 16% coarse particles, particularly in the low gel KOH concentration of 26%.

[0078] Figure 6 displays a contour plot of partial discharge cell outgassing of LR6 cells as determined by dust content and bulk density of zinc powders. The anode gel composition included a KOH concentration of 26.5%, zinc loading 70%, RM510 content at 35 ppm and the zinc alloy contained bismuth and indium at 200 ppm. The data in Figure 6 suggest that partial discharge cell outgassing can be minimized to below 0.70 ml at dust contents below 6% and bulk densities as low as 2.66 g/ml. In Figure 6, the significance of each plotted factor, % dust and bulk density, is given by their respective p-values that reflect a concept of probability. Any p-value of 0.017, corresponding to the % dust factor, can be interpreted as having a 98.3% probability that the PD cell outgassing plot will allow the contour lines defined by the % dust levels to dust, as shown in Figure 6.

[0079] Figure 7 illustrates DSC performance in percentage of LR6 cells after storage for one week at 71.11 °C (160 °F) as determined by dust content and zinc bulk density. A control cell with 0% dust and 52% coarse particle content was used as a reference and was assumed to have 100% performance. The best DSC results are seen at the highest dust content and lowest bulk density, such as 9% and 2.66 g/ml, respectively.

[0080] Figure 8 illustrates the results of partial discharge (PD) cell outgassing of LR6 cells that have a zinc powder of apparent density at 2.72 g/ml that contains the alloying elements of bismuth and indium at about 200 ppm. Cell gassing was measured under various conditions of KOH concentration and under various amounts of RM-510 added to the anode. It is observed that PD cell gassing is increased while the RM510 concentration is decreased from 120 to 20 ppm. PD cell gassing is evident at the lower RM510 content. The corresponding DSC performance is shown in Figure 9. The present technology therefore recognizes that performance advantages can be achieved at optimal concentrations of RM510 and KOH.

[0081] The present technology recognizes that the use of zinc anode powders with coarse particle content below 20% and fine particle content greater than that of conventional zinc anode powders improves cell amperage and circuit voltage closed as well as reduces cell impedance, thereby promoting improved resistance to physical tests such as the drop test. LR20 cells were prepared, in which the anode included a zinc alloy that included bismuth and indium at about 150 to 200 ppm, RM510 surfactant at a concentration of about 60 ppm, and KOH gel at a concentration of about 32 %. Figure 10 illustrates the cell amperage of LR20 cells for conventional control cells that are 49% coarse-14% fine compared to the amperage of LR20 cells that contain 16% coarse-37% coarse. fine particles and 12% coarse particles-42% fine particles. It is observed that, irrespective of the relative high content of fine particles (37% and 42%), cells having low (12%) and 16% coarse particles exhibited cell outgassing approximately equal to or lower than that of control cells with low fines (14%) as shown in Figure 11. Partial discharge with LR20 cells was done at 600 mA for 11.0 hours.

[0082] While certain embodiments have been illustrated and described, it is to be understood that changes and modifications may be made to this document in accordance with a person of ordinary skill in the art without departing from the technology in its broader aspects as defined in following claims.

[0083] The modalities, illustratively described in this document, can be properly practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed in this document. Thus, for example, the terms "which comprises", "which includes", "which contains" etc. must be read expansively and without limitation. Additionally, the terms and expressions used herein are used as terms of description and not limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the features shown and described or portions thereof, but it is acknowledged that various modifications are possible within the scope of the claimed technology. Additionally, the expression "consisting essentially of" will be understood to include those specifically cited elements and those additional elements that do not materially affect the basic and innovative characteristics of the claimed technology. The phrase "consisting of" excludes any unspecified element.

[0084] The present disclosure is not to be limited in terms of the particular embodiments described in this application. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of the disclosure, other than those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to be within the scope of the appended claims. The present disclosure is to be limited only to the terms of the appended claims together with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, composite compositions or biological systems, which may, of course, vary. It should also be understood that the terminology used herein is intended to describe particular embodiments only and is not intended to be limiting.

[0085] Furthermore, when features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thus described in terms of any individual member or subgroup of members of the Markush group .

[0086] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and subrange combinations thereof . Any range listed can be easily recognized as describing and sufficiently enabling the same range to be broken down into at least halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each band discussed in the present document can be readily decomposed into a lower third, middle third and upper third, etc. As will also be understood by a person skilled in the art, all language such as "up to", "at least", "greater than", "less than" and the like includes the quoted number and refers to ranges that may subsequently be decomposed into subbands, as discussed above. Finally, as will be understood by a person skilled in the art, a strip includes each individual member.

[0087] All publications, patent applications, issued patents and other documents referred to in this descriptive report are incorporated into this document by way of reference as if each publication, patent application, issued patent or other individual document was specifically or individually indicated for be incorporated by way of reference, in its entirety. Definitions that are contained in the text incorporated by reference are excluded to the extent that they contradict the definitions in this disclosure.

[0088] Other embodiments are set out in the following claims.

Claims (8)

1. Gelled anode for an alkaline battery cell comprising: a gelling agent; an alkaline electrolyte comprising a hydroxide material; a surfactant; and zinc-based particles, wherein less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than 150 micrometers; wherein the zinc-based particles have an aspect ratio of 1.85 to 4.15 and an apparent density of 2.40 g/cm3 to 3.15 g/cm3. 2. Gelled anode, according to claim 1, characterized in that the zinc-based particles have a roundness of at least 1.5. 3. Gelled anode, according to claim 1, characterized in that the zinc-based particles are zinc alloy particles having an average particle size of 100 micrometers to 130 micrometers. 4. Gelled anode, according to claim 1, characterized in that 20% to 45% by weight of the total zinc in the electrode have a particle size of less than 75 micrometers, 1% to 10% by weight with respect to the total zinc in the electrode have a particle size of less than 45 micrometers, and 10% to 20% by weight of the total zinc in the electrode have a particle size of greater than 150 micrometers. 5. Gelled anode, according to any one of claims 1 to 4, characterized in that it has a hydroxide content of less than 40%. 6. Alkaline electrochemical cell characterized by comprising: a positive current collector; a cathode in contact with the positive current collector; a negative current collector; a gelled anode, as defined in claim 1, in contact with the negative current collector; and a separator between the cathode and anode. 7. Method for reducing outgassing of an electrochemical cell which is subject to outgassing, the method being characterized by comprising: providing, as the active anode of said cell, a gelled anode comprising a gelling agent; an alkaline electrolyte comprising a hydroxide material; a surfactant; and zinc-based particles; wherein: less than 20% of the zinc-based particles, by weight, relative to the total zinc in the electrode, have a particle size greater than 150 micrometers, and less than 10% of the zinc-based particles, by weight, in relation to the total zinc in the electrode, they have a particle size of less than 45 micrometers; and the zinc-based particles have an aspect ratio of 1.85 to 4.15 and an apparent density of 2.40 g/cm3 to 3.15 g/cm3. 8. Method, according to claim 7, characterized by the fact that the formation of gases is reduced by 10% to 50% in battery cells having zinc powders containing less than 20% of coarse particles in relation to cells that have an active anode comprising zinc-based particles in apparent densities between 2.50 and 3.0 g/ml and large content (> 150 micrometers) between 20% to 60%, by weight, in relation to the zinc electrode total.