MXPA00006486A - Battery cathode - Google Patents

Abstract

A cathode (12) that includes manganese dioxide and relatively small particles of nonsynthetic, nonexpanded graphite is disclosed. The graphite particles can have an average particle size of less than 20 microns. The cathode (12) can be used in an electrochemical cell, such as a battery (10).

Description

C BATTERY ALL DESCRIPTION OF THE INVENTION The present invention is concerned with batteries. Batteries, such as alkaline batteries, are commonly used as sources of energy. In general, alkaline batteries have a cathode, an anode, a separator and an electrolytic solution. The cathode is commonly formed of manganese dioxide, carbon particles and a binder. The anode can be formed from a gel that includes zinc particles. The separator is usually disposed between the cathode and the anode. The electrolyte solution, which is dispersed throughout the battery, may consist of a hydroxide solution. The invention is concerned with batteries, such as alkaline batteries, which have cathodes including manganese dioxide and relatively small, non-synthetic, non-expanded graphite particles. These batteries have good performance characteristics. For example, batteries may exhibit high energy output at a high discharge rate, such as a discharge speed equal to at least the capacity of the battery (in Ampere-hours units) discharged in one hour. The batteries can have various industrial standard sizes, such as AA, AAA, AAAA, C or D. REF.121098 The terms "Non-synthetic graphite particles" refer to graphite particles that are prepared without using a process of industrial or laboratory graphitization. "Non-expanded graphite particles" refer to graphite particles that have not undergone any process of industrial or laboratory expansion. In one aspect the invention features a cathode including manganese dioxide and non-synthetic, non-expanded graphite particles having an average particle size of less than about 20 microns. The particle size is measured using a HELIOS Sympatec analyzer. For a given sample of graphite particles, the average particle size is the particle size for which half the volume of the sample has a smaller particle size. In another aspect, the invention has as characteristics an electrochemical cell that includes a cathode and an anode and a separator disposed between cathode and anode. The cathode includes manganese dioxide and non-synthetic, non-expanded graphite particles having an average particle size of less than about 20 microns. In some embodiments, the separator includes a nonwoven material, without a membrane and a second nonwoven material without a membrane disposed along the surface of the first material. In these embodiments, the separator may be devoid of a membrane layer or an adhesive layer disposed between the nonwoven, membraneless materials. A membrane material refers to a material having an average pore size of less than about 0.5 microns, while a membraneless material refers to a material having an average pore size of at least about 5 microns. The cathode may have a porosity of about 21% to about 28%. The porosity of the cathode is the relative volume of the cathode that is not taken up by the solid material, such as for example manganese dioxide and graphite and binder particles. The anode can have a porosity of about 2 grams of zinc particles to about 2.45 grams of zinc particles per cubic centimeter of anode volume that is taken up by the liquid or solid material. The battery may have a relatively small amount of manganese dioxide and / or zinc particles compared to the amount of electrolyte solution. For example, the weight ratio of manganese dioxide to electrolyte solution can be from about 2.2 to about 2.9 and the weight ratio of zinc particles to electrolyte solution can be from about 0.9 to about 1.25. It is calculated based on the amount of electrolytic solution dispersed throughout the cathode, the anode and the separator. The batteries can be AA or AAA batteries that show good results when tested according to the photo test, the continuous 1 watt test, the continuous half-watt test, the pulsed test, the half-watt rm test and / or the one-quarter-watt rm test. These tests are described later in this. Other features and advantages of the invention will become apparent from the description of the preferred embodiments thereof and the claims. Figure 1 is a view in. cross section of a battery. Preferred batteries are alkaline batteries having a cathode formed of manganese dioxide, relatively small non-synthetic, non-expanded graphite particles and optionally a binder. With reference to Figure 1, a battery 10 having a cathode 12, an anode 14, a separator 16, an external wall 18 which comes into contact with the outer diameter of the cathode 12 and the insulating layer 26 is shown. The battery 10 further includes an anode manifold 20 which is passed through a metal element 22 and the anode 14. The upper end of the anode manifold 20 is connected to a negative end cap 24 which serves as the negative external terminal of the anode. the battery 10. The layer 26 can be formed of an electrically non-conductive material, such as a plastic that can be thermally shrunk. In addition, an electrolyte solution is dispersed throughout the battery 10. If the graphite particles disposed within the cathode 12 are too large, the conductivity of the cathode 12 may be not sufficiently low. However, if the graphite particles are too small, the cathode 12 can be comparatively dense, reducing the amount of electrolytic solution at the cathode 12 and decreasing the efficiency of the battery 10. Therefore, the graphite particles at the cathode 12 they preferably have an average particle size of at most 20 microns, more preferably from about 2 microns to about. 12 microns and more preferably from about 5 microns to about 9 microns, as measured using a HELIOS analyzer from Sympatec. In some embodiments, the graphite particles are unexpanded, non-synthetic graphite particles having an average particle size of about 7 microns, as measured by this method. Unexpanded, unexpanded graphite particles are available for example, Brazilian Nacional de Grafite (Itapecirica, MG Brasil). The amount of graphite particles disposed within the cathode 12 must be sufficient to improve the overall conductivity of the cathode 12 as it has minimal impact on the energy capacity of the battery 10. Preferably, the cathode 12 consists of about 4% by weight to about 10% by weight of graphite particles, more preferably from about 5% by weight to about 9% by weight of graphite particles and more preferably from about 6% by weight to about 8% by weight of graphite particles . These ranges of percentages by weight correspond to when the electrolytic solution is not dispersed within the cathode 12. The cathode 12 can be a single pellet or agglomerate of material. Alternatively, the cathode 12 can be formed from a variety of agglomerates or pellets of the cathode that are stacked one on top of the other. Either in one case or another, the cathode pellets can be made by first mixing the manganese dioxide, carbon particles and optionally the binder. For embodiments in which more than one pellet is used, the mixture can be pressed to form the pellets. The pellet (s) is filled into the battery 10 using standard processes. For example, in one process, a central rod is placed in the central cavity of the battery 10 and then a punch or die is used to pressurize the pellet above. When this process is used, the interior of the wall 18 may have one or more vertical projections that are circumferentially spaced around the wall 18. These projections may help retain the cathode 12 in place within the battery 10. In embodiments in which the cathode 12 It is formed from a single pellet or agglomerate, the powder can be placed directly inside the battery 10. A retaining ring is adjusted in place and an obstruction rod is passed through the ring, densifying the powder and forming the cathode 12. In certain embodiments, a layer of conductive material can be disposed between the wall 18 and the cathode 12. This layer can be disposed along the inner surface of the wall 18, along the external surface of the cathode 12. or both Normally, this conductive layer is formed of a carbonaceous material. Such materials include LBIOOO (Timcal), Ecocoat 257 (W.R. Grace &; Co.), Electrodag 109 (Acheson Industries, Inc.), Electrodag 112 (Acheson) and EB0005 (Acheson). Methods for applying the conductive layer are described, for example, in Canadian Patent No. 1,263,697, which is incorporated herein by reference.

The use of a conductive layer, especially Electrodag 109 or EB005, between the wall 18 and the cathode 12 can reduce the pressure used when the cathode 12 is formed inside the battery 10. Thus, the porosity of the cathode can be made relatively high without cause the agglomerate (s) to be crushed (s) or cracked (s) when the cathode 12 is formed within the battery 10. However, if the porosity of the cathode 12 is too low, an amount insufficient electrolytic solution can be dispersed behind the cathode 12, reducing the efficiency of the battery 10. Thus, in certain embodiments, the cathode 12 has a porosity of about 21% Co to about 28%, more preferably about 25% to about 27%, and more preferably of about 26%. Within cathocb 12, any of the conventional forms of manganese dioxide can be used. Distributors of such manganese dioxide include Kerr McGee, Co., Broken Hill Proprietary, Chem Metals, Co., Tosoh, Delta Manganese, Mitsui Chemicals and JMC. In certain embodiments, the cathode 12 can have from about 8.9 grams of manganese dioxide to about 9.8 grams of manganese dioxide. In these embodiments, the cathode 12 preferably includes about 9.3 grams to about 9.8 grams of manganese dioxide, more preferably from about 9.4 grams to about 9.65 grams of manganese dioxide and more preferably from about 9.45 grams to about 9.6 grams of manganese dioxide. manganese dioxide. In other embodiments, the cathode 12 preferably includes from about 4 grams to about 4.3 grams of manganese dioxide, more preferably from about 4.05 grams to about 4.25 grams of manganese dioxide and more preferably from about 4.1 grams to about 4.2 grams. of manganese dioxide. In some embodiments, the cathode 12 may further include a binder. Examples of binders for the cathode 12 include polyethylene powders, polyacrylamides, Portland cement and fluorocarbon resins, such as PVDF and PTFE. In certain embodiments, the cathode 12 includes a polyethylene binder sold under the tradename HA-1681 (Hoescht). When the cathode 12 includes a binder, the binder preferably consists of less than about 1% by weight of the cathode 12, more preferably from about 0.1% by weight to about 0.5% by weight of the cathode 12 and more preferably about 0.3% by weight of the cathode 12. These percentages by weight correspond to when the electrolytic solution is not dispersed within the cathode 12.

The cathode 12 may include other additives. Examples of these additives are described in U.S. Patent No. 5,342,712, which is incorporated herein by reference. In some embodiments, the cathode 12 preferably includes from about 0.2 wt% to about 2 wt% TiO2, more preferably about 0.8 wt% TiO2. The anode 14 can be formed from any of the standard zinc materials used in the battery anodes. Frequently, the anode 14 is formed of zinc gel which includes zinc metal particles, a gelling agent and minor amounts of additives, such as gasification inhibitors.

If the porosity of the anode 14 is too high, the amount of zinc within the anode 14 is reduced, which decreases the capacity of the battery 10. However, if the porosity of the anode 14 is too low, an insufficient amount of electrolyte can Accordingly, in certain embodiments, the anode 14 preferably includes from about 2 grams of zinc particles to about 2.45 grams of zinc particles per cubic centimeter of the anode, more preferably a porosity of about 2.1. grams of zinc particles to about 2.35 grams of zinc particles per cubic centimeter of the anode and more preferably a porosity of about 2.15 grams of zinc particles to about 2.3 grams of zinc particles per cubic centimeter of the anode. In certain modalities, the anode 14 preferably includes from about 3.7 grams to about 4.25 grams of zinc particles, more preferably from about 3.8 grams to about 4.15 grams of zinc particles and more preferably from about 3.9 grams to about 4.05 grams of particles of zinc. zinc. In other embodiments, the anode 14 preferably includes from about 1.5 grams to about 1.9 grams of zinc particles, more preferably from about 1.55 grams to about 1.85 grams of zinc particles and more preferably from about 1.35 grams to about 1.75 grams. of zinc particles. In some embodiments, the anode 14 preferably includes from about 64% by weight to about 76% by weight of zinc particles, more preferably from about 66% by weight to about 74% by weight of zinc particles and more preferably from about 68% by weight to about 72% by weight of zinc particles. These percentages by weight correspond to when the electrolyte solution is dispersed within the anode 14. Gelation agents which can be used at the anode 14 include polyacrylic acids, grafted starch materials, salts of polyacrylic acids, polyacrylates, carboxymethylcellulose or combinations thereof . Examples of such polyacrylic acids are Carbopol 940 (B.F. Goodrich) and Polygel 4P (3V) and an example of a grafted starch material is Waterlock A221 (Grain Proccesing Corporation, Muscatine, IA). An example of a salt of a polyacrylic acid CL15 (Allied Colloids). In some embodiments, the anode 14 preferably includes from about 0.2 wt% to about 1 wt% total gelling agent, more preferably from about 0.4 wt% to about 0.7 wt% total gelling agent and more preferably from about 0.5% by weight to about 0.6% by weight of total gelling agent. These percentages by weight correspond to when the electrolytic solution is dispersed within the anode 14. The gasification inhibitors can be inorganic materials such as bismuth, tin, lead and indium. Alternatively, the gasification inhibitors can be organic compounds, such as phosphate esters, ionic surfactants or nonionic surfactants.

Examples of ionic surfactants are described, for example, in US Pat. 4, 777, 100 which is incorporated herein by reference. The separator 16 can have any of the conventional designs for the battery separators. In some embodiments, the separator 16 is formed of two layers of unwoven material, without a membrane, one layer being disposed along one surface of the other. In these rirdalidaa = s, the - separator not in Gr-e of p-eferarria a layer, de rrateriaL ds rihrrbrsna or a layer of achs- SÍTO between the non-woven layers, without hammer. To erase the voJ-urm = L separator 16 that is intended to build an ef-ücia-rte battery, each layer of non-woven material, without mist, may have a base weight of apra > drrB a-n3-? i-e 54 grarrcs per petro square, a thickness of aprax_ü H3arra-rte 0.1372 rrrt (5.4 piles of an inch) when dry and a thickness of approximately 0.254 mm (10 mils) when wet. In a . modality, the unwoven material, without membrane, is a matrix of polyvinyl alcohol (PVA) fibers, cellulose fibers and PVA binder. In general, the unwoven material, without membrane, is devoid of fillers such as for example inorganic particles. In other embodiments, the separator 16 includes an outer layer of cellophane with a layer of non-woven material.

The separator also includes an additional layer of non-woven material. The cellophane layer may be adjacent to the cathode 12 or the anode 14. Preferably, the nonwoven material contains from about 78% by weight to about 82% by weight of PVA and from about 18% by weight to about 22% by weight of rayon with a trace of surfactant. Such non-woven materials are available from PDM under the tradename PA36. The electrolytic solution dispersed throughout the battery 10 can be any of the conventional electrolytic solutions used in the batteries. Normally, the electrolytic solution is an aqueous solution of hydroxide. Such aqueous solutions of hydroxide include, for example, solutions of potassium hydroxide and solutions of sodium hydroxide. In some embodiments, the electrolyte solution is an aqueous solution of potassium hydroxide that includes from about 33 wt% to about 38 wt% potassium hydroxide. In certain embodiments, the battery 10 preferably includes from about 3.4 grams to about 3.9 grams of electrolyte solution, more preferably from about 3.45 to about 3.65 grams of electrolyte solution, and more preferably from about 3.5 grams to about 3.6 grams of electrolyte solution . In other embodiments, the battery 10 preferably includes from about 1.6 grams to about 1.9 grams of electrolyte solution, more preferably from about 1.65 grams to about 1.85 grams of electrolyte solution and more preferably from about 1.7 grams to about 1.8 grams of electrolyte solution. electrolytic solution. The weight ratio of manganese dioxide to electrolyte solution can be from about 2.2 to about 2.9 and the weight ratio of zinc particles to the electrolyte solution can be from about 0.9 to about 1.25. In some embodiments, the weight ratio of manganese dioxide to electrolyte solution is from about 2.5 to about 2.9 and the weight ratio of zinc particles to the electrolyte solution is from about 1.1 to about 1.25. In other embodiments, the weight ratio of manganese dioxide to electrolyte solution is from about 2.5 to about 2.65 and the weight ratio of zinc particles to the electrolyte solution is from about 0.9 to about 1.2. These proportions are based on the amount of electrolytic solution dispersed throughout the anode, cathode and separator. The batteries can be AA or AAA batteries that show good results when tested according to the photo test, the continuous 1 Watt test, the continuous half Watt test, the pulsed test, the half Watt and / or the one-quarter Watt rm test. These tests are described later in this. The battery 10 can be an AA battery that exhibits excellent results when tested in accordance with the photo test (described later herein). For example, when it is discharged at 1 volt according to the photo test, the battery AA can give at least 150 pulses, at least about 175 pulses to at least about 185 pulses or at least about 200 pulses. When discharged at 0.8 volts according to the photo test, the battery AA can give at least 350 pulses, at least about 375 pulses, at least about 385 pulses or at least about 400 pulses. The battery 10 can be an AA battery that exhibits excellent results when tested in accordance with the continuous 1 Watt test (described later herein). For example, when it is discharged at 1 volt according to the continuous 1 Watt test, the AA battery can give at least about 0.6 hours, at least about 0.65 hours, at least about 0.7 hours or at least about 0.75 hours. hours. When discharged at -8 volts in accordance with the continuous 1 Watt test, the AA battery can give at least 0.95 hours, at least about 1 hour, at least about 1.05 hours or at least about 1.1 hours. The battery 10 can be an AA battery that offers excellent performance when tested in accordance with the pulsed test (described later herein). For example, when it is discharged at 1 volt according to the pulsed test, the AA battery can give at least about 1.6 hours, at least about 1.75 hours, at least about 2 hours or at least about 2.15 hours- When is downloaded to 0. 8 volts according to the pulsed test, AA battery can give at least 2.75 hours, at least about 3 hours, at least about 3.25 hours or at least about .3.3 hours. The battery 10 can be an AA battery that offers excellent performance in accordance with the half Watt rm test (described later herein). For example, when it is discharged at 1.1 volts according to the half Watt rm test, the AA battery can give at least about 1.5 hours, at least about 2 hours, at least about 2.5 hours or at least about 2.65 hours. When discharged at 0.9 volts in accordance with the half Watt rm test, the AA battery can give at least 2.9 hours, at least about 3 hours, at least about 3.25 hours or at least about 3.4 hours. The battery 10 can be an AAA battery that offers excellent performance in accordance with the continuous medium Watt test (described later herein). For example, when it is discharged at 1 volt in accordance with the continuous half Watt test, the AAA battery can give at least about 0.65 hours, at least about 0.7 hours, at least about 0.75 hours or at least about 0.8. hours. When discharged at 0.9 volts in accordance with the continuous half Watt test, the AAA battery can give at least 0.9 hours, at least about 0.95 hours, at least about 1 hour or at least about 1.05 hours. The battery can be an AAA battery that offers excellent performance according to the pulsed test (described later in this). For example, when it is discharged at 1 volt according to the pulsed test, the AAA battery can give at least about 0.35 hours, at least about 0.4 hours, at least about 0.45 hours or at least about 0.5 hours. When discharged at 0.9 volts according to the pulsed test, the AAA battery can give at least 0.65 hours, at least about 0.7 hours, at least about 0.75 hours or at least about 0.8 hours. The battery 10 can be an AAA battery that offers excellent performance in accordance with the half Watt rm test (described later herein). For example, when it is discharged at 1.1 volt according to the half Watt rm test, the AAA battery can give at least about 0.4 hours, at least about 0.45 hours, at least about 0.5 hours or at least about 0.55 hours. When discharged at 0.9 volts according to the half Watt rm test, the AAA battery can give at least 0.9 hours, at least about 0.95 hours, at least about 1 hour or at least about 1. 05 hours. The battery 10 can be an AAA battery which offers excellent performance in accordance with the one-quarter Watt rm test (described later herein). For example when it is discharged at 1.1 volts according to the one quarter Watt rm test, the AAA battery can give at least about 2 hours, at least about 2.1 hours, at least about 2.2 hours or at least approximately 2.3 hours. When discharged at 0.9 volts according to the quarter-watt rm test, the AAA battery can give at least 3.1 hours, at least about 3.25 hours, at least about 3.4 hours or at least about 3.5 hours .

Example I AA batteries were prepared with the following components. The cathode included approximately 9,487 grams of manganese dioxide (Kerr-McGee, Co.), approximately 0.806 grams of non-synthetic, unexpanded graphite, which has an average particle size of about 7 microns (Brazilian National De Grafite) and approximately 0.3 % by weight of coathylene HA-1681. The anode included approximately 3,976 grams of zinc particles, approximately 50 ppm of surfactant (RM 510, Rhone Poulenc) in relation to zinc and approximately 0.5% by weight of total gelling agent (Carbopol 940 and A221). The porosity of the cathode was approximately 26% and the porosity of the anode was approximately 2,173 grams of zinc per cubic centimeter of the anode. The separator consisted of a two-layer structure, each layer formed of a nonwoven material that included approximately 57% by weight of PVA fibers (approximately 0.5 denier to 6 millimeters), approximately 30% by weight of rayon fibers (about 1.5 denier to 6 millimeters) and about 13% by weight of PVA binder. Each layer was approximately 0.1372 mm (5.4 thousandths of an inch) thick when dry and approximately 0.254 mm (10 mils) thick when wet. Each layer had a basis weight of approximately 54 grams per square meter. The separator did not include an adhesive and the layers were substantially devoid of any filler. The battery also included approximately 3,598 grams of aqueous solution of potassium hydroxide (approximately 35.5% by weight of potassium hydroxide). A thin coating of EB005 (Acheson) was disposed between the outer layer of the battery and the outer periphery of the cathode. The AA batteries were stored at a temperature of about 20.1 ° C to about 22.1 ° C for 5 days. Then, the AA batteries were stored according to the following procedure. Each battery is examined visually for leaks or material damage and identified in such a way that the identification of the battery can be maintained throughout the test program. The batteries are oriented on their sides in trays or holding plates in such a way that the batteries are not in physical contact with each other. The plates or retention trays are manufactured in such a way that they are resistant to heat and electrolytes. The trays are stored for a day at ambient conditions, after which they are placed in a preheated chamber.

The trays are spaced such that there is at least about 5 cm (2 inches) of space between the wall of the chamber and the upper tray, the lower tray or the tray adjacent to each tray. The following 24-hour test sequence, shown in Table I, is repeated for 14 days. The trays are removed from the chamber and each battery is visually examined for leaks and material damage.

Table 1 The trays are removed from the chamber and each battery is visually examined for leaks or material damage.

The following tests were carried out subsequently on individual AA batteries. Each test was carried out at a temperature of about 20.1 ° C to about 22.1 ° C. An AA battery was discharged from an open circuit voltage of approximately 1.6 volts under constant current conditions of 10 seconds per minute for one hour per day ("the photo test"). The AA battery reached 1 volts after 203 pulses and the AA battery reached 0.8 volts after 443 pulses. An AA battery was continuously discharged from an open circuit voltage of approximately 1.6 volts to 1 Watt ("1 Watt continuous test"). The AA battery reached 1 volt after approximately 0.75 hours and the AA battery reached 0.8 volts after approximately 1.00 hours. An AA battery was continuously discharged from an open circuit voltage of approximately 1.6 volts at a rate that alternated between 1 Watt (3 seconds pulses) and 0.1 Watts (7 seconds pulses) ("pulsed test"). The AA battery reached 1 volt after approximately 2.16 hours and the AA battery reached 0.8 volts after approximately 3.72 hours. An AA battery was discharged from an open-circuit voltage of approximately 1.6 volts at 0.5 Watts for 15 minutes per hour ("the half-Watt rm test"). The AA battery reached 1.1 volts after approximately 1.87 hours and the AA battery reached 0.9 volts after approximately 3.34 hours.

Example II An AAA battery is prepared. Cathode 12 included approximately 4,155 grams of manganese dioxide (Kerr McGee, Co.) about 0.353 grams of non-synthetic, unexpanded graphite, having an average particle size of about 7 microns (Brazilian National Grafite) and about 0.3% by weight of coathylene HA-1681. The anode 14 included approximately 1666 grams of zinc particles, and aprracj-radar-rite 0.5% to the weight of the a sification agent. - total (Carbopol 940 and A221). The porosity of the cathode was -about 2,266 grams of zinc per cubic centimeter of the anode 14. The separator included layers of non-woven material. The separator consisted of a two-layer structure, each layer being formed of a nonwoven material that includes approximately 57% by weight of PVA fiber (approximately 0.5 denier to 6 millimeters), approximately 30% by weight of cellulose fibers (approximately 1.5 denier to 6-millimeters) and approximately 13% by weight of PVA binder. Each layer was approximately 0.1372 mm (5.4 mils) thick when dry and approximately 0.254 millimeters (10 mils) thick when wet. Each layer had a basis weight of approximately 54 grams per square meter. The separator did not include an adhesive and the layers were substantially devoid of a filler. The battery also included approximately 1.72 grams of an aqueous solution of potassium hydroxide (approximately 35.5% by weight). A thin coating of EB005 'was disposed between the outer wall of the battery and the outer periphery of the cathode. The AAA batteries were stored as described in Example 1. Each AAA battery was discharged from an open circuit voltage of approximately 1.6 volts and the tests were carried out within the temperature range described in Example I. One AAA battery was continuously discharged from an open circuit voltage of approximately 1.6 volts to half Watt ("the continuous test of half Watt"). The AAA battery reached 1 volt after approximately 0.76 hours and the AA battery reached 0.8 volts after approximately 0.96 hours. With the test pressed, the AAA battery took approximately 0.55 hours to reach 1 volt and approximately 0.84 hours to reach 0.8 volts. With the half Watt rm test, an AAA battery took approximately 0.57 hours to reach 1 volt and approximately 1.08 hours to reach 0.8 volts. An AAA battery was discharged from an open-circuit voltage of approximately 1.6 volts at 0.25 Watts for 15 minutes per hour ("the one-quarter-Watt rm test"). The AAA battery reached 1.1 volts after approximately 2.4 hours and the AAA battery reached 0.9 volts after approximately 3.65 hours.

Example III AA batteries were prepared with the following components. The cathode included approximately 9.11 grams of manganese dioxide (40:60 weight mixture of Delta: Tosoh), approximately 0.810 grams of non-synthetic, unexpanded graphite having an average particle size of approximately 7 microns (Brazilian National Grafite) and about 0.8% by weight of titanium dioxide (Kronos). The anode included approximately 3.89 grams of zinc particles, approximately 0.88% by weight of total gelling agent (3V and CL15) and approximately 50 ppm of surfactant (RM 510, Rhone Poulenc). The porosity of the cathode was approximately 23% and the porosity of the anode was approximately 2,173 grams of zinc per cubic centimeter of the anode. The separator included a layer of non-woven material (PA 36 A, PDM) a layer of PA36C and a layer of cellophane (0.254 mm (1 thousandth of an inch) thickness). The cellophane was adjacent to the cathode and the non-woven layer PA36A was adjacent to the anode. The battery also included approximately 3.62 grams of aqueous solution of potassium hydroxide (approximately 35.5% by weight of potassium hydroxide). A thin coating of EB005 (Acheson) was disposed between the outer wall of the battery and the outer periphery of the cathode. The AA batteries were stored at a temperature of about 20.1 ° C to about 22.1 ° C for about 5 days according to the protocol described in Example I. The following tests were subsequently carried out on individual AA batteries. Each test was carried out at a temperature of about 20.1 ° C to about 22.1 ° C. The AA battery was discharged according to the photo test. The AA battery reached 1 volt after 180 impulses and the AA battery reached 0.8 volts after 347 impulses. An AA battery was discharged according to the 1 Watt continuity test. The AA battery reached 1 volt after approximately 0.57 hours and the AA battery reached 0.8 volts after approximately 0.80 hours. An AA battery was continuously discharged from an open circuit voltage according to the pulsed test. The AA battery reached .1 volt after approximately 1.76 hours and the AA battery reached 0.8 volts after approximately 3.11 hours. An AA battery was discharged according to the half Watt rm test. The AA battery reached 1.1 volts after approximately 1.66 hours and the AA battery reached 0.9 volts after approximately 3.05 hours. Other embodiments are encompassed by the claims. It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention is the conventional one for the manufacture of the objects to which it relates.

Claims (16)

1. CLAIMS Having described the invention as above, property is claimed as contained in the following claims: 1. An electrochemical cell characterized in that it comprises: a cathode; an anode; a separator disposed between the cathode and the anode, wherein the cathode comprises: manganese dioxide; and non-synthetic, non-expanded graphite particles, having an average particle size of less than about 20 microns.
2. 2. The electrochemical cell according to claim 1, characterized in that the non-synthetic, non-expanded graphite particles have an average size of about 2 microns to about 12 microns.
3. 3. The electroguimic cell according to claim 1, characterized in that the non-synthetic, non-expanded graphite particles have an average size of about 5 microns to about 9 microns. . The electrochemical cell according to claim 1, characterized in that the cathode comprises at most about 10% non-synthetic, non-expanded graphite particles by weight. 5. The electrochemical cell according to claim 1, characterized in that the electrochemical cells is an alkaline battery. The electrochemical cell according to claim 1, characterized in that the electrochemical cell is selected from the group consisting of AA batteries, AAA batteries, AAA batteries, C batteries and batteries D. The electrochemical cell according to claim 1 , characterized in that the separator comprises a non-woven material, without a membrane and a second non-woven material, without a membrane, disposed along a surface of the first material. 8. The electrochemical cell according to claim 1, characterized in that the cathode has a porosity of about 21% to about 28%. The electrochemical cell according to claim 1, characterized in that the anode comprises zinc particles and wherein the anode has a porosity of about 2 grams of zinc particles to about 2.45 grams of zinc particles per cubic centimeter of the volume of the anode. 10. The electroguimic cell according to claim 1, characterized by further comprising an electrolytic solution, wherein a weight ratio of manganese dioxide to the electrolytic solution is from about 2.2 to about 2.9. The electrochemical cell according to claim 1, characterized in that it further comprises an electrolytic solution, wherein the anode comprises zinc particles and a weight ratio of the zinc particles to the electrolytic solution is from about 0.9 to about 1.25. 12. A cathode characterized in that it comprises: manganese dioxide; and non-synthetic, unexpanded graphite particles having an average particle size of less than about 20 microns. The cathode according to claim 12, characterized in that the non-synthetic, non-expanded graphite particles have an average size of about 2 microns to about 12 microns. 14. The cathode according to claim 12, characterized in that the non-synthetic, non-expanded graphite particles have an average size of about 5 microns to about 9 microns. 15. The cathode according to claim 12, characterized in that the cathode comprises at most 10% by weight of graphite particles, not synthetic, not expanded by weight. 16. The cathode according to claim 12, characterized in that the cathode has a porosity of about 21% to about 28%.