MXPA01003995A - Titanium additives for manganese dioxide cathode electrochemical cell - Google Patents

Abstract

A cathode (12) that includes manganese dioxide and a titanium oxy salt, preferably titanium oxy sulfate, is disclosed. Batteries (10) having cathode (12) have good performance characteristics. For example, the batteries (10) perform well in applications involving intermittent drains such as toys. Also disclosed is an electrochemical cell including a cathode (12) an anode (14) and a separator (16) disposed between the cathode and the anode. The cathode includes manganese dioxide and a titanium oxy salt.

Description

TITANIUM ADDITIVES FOR CELL ELECTROCHEMISTRY OF MANGANESO DIOXIDE CÁTODO DESCRIPTION. OF THE INVENTION The present invention relates to 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 alkaline electrolytic solution. The cathode is typically formed of manganese dioxide, carbon particles, alkaline electrolyte solution and a binder. The anode can be formed from a gel that includes alkaline electrolyte solution and zinc particles. The separator is placed between the cathode and the anode. The electrolyte solution, which is dispersed throughout the length of the battery, can be a hydroxide solution such as potassium hydroxide. The invention relates to batteries, such as alkaline batteries, which have cathodes including manganese dioxide and a titanium oxy salt, preferably titanium oxysulfate (TiOS04). These batteries have good operating characteristics. For example, batteries work well in applications involving intermittent draining such as in Ref: 128987 toys (IEC test at 3.9 ohms, 1 hour / day), flashing lights (flash) IEC and ANSI tests at 3.9 Ohms, 1 hour / day). The batteries may have various industrial standard sizes, such as AA, AAA, AAAA, C or D. In one aspect, the invention features a cathode that includes manganese dioxide and an oxy oxy salt. In still another aspect, the invention features an electrochemical cell that includes a cathode, an anode and a separator positioned between the cathode and the anode. The cathode includes manganese dioxide and a titanium oxy salt. Preferred embodiments include one or more of the following characteristics. The titanium oxi salt is titanium oxysulfate (TiOS0). The cathode includes from 0.1% to 5% of the titanium oxy salt based on the total weight of the active cathode material. The cathode also includes conductive particles. Other features and advantages of the invention will be apparent from the description of the preferred embodiments thereof and the claims. Figure 1 is a cross-sectional view of a battery. Preferred batteries are alkaline batteries having a cathode formed of manganese dioxide, conductive particles selected from the group consisting of carbon, graphite, and mixtures thereof, titanium oxy salt, for example, (TiOS04), and optionally an amount of alkaline electrolyte and a binder. With reference to the figure, a battery 10 having the cathode 12, an anode 14, a separator 16, an outer wall 18 which makes contact with the outer diameter of the cathode 12, and an insulating layer 26 is shown. The battery 10 includes further an anode manifold 20 which passes through a seal member 22 and towards 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 battery 10. The layer 26 can be formed of an electrically non-conductive material, such as a heat-shrinkable plastic. In addition, an electrolyte solution is dispersed throughout the length of the battery 10. The cathode 12 can be a single pellet of material. Alternatively, the cathode 12 can be formed from a number of cathode pellets that are stacked on top of one another. In any case, the cathode pellets can be processed first by mixing the manganese dioxide, the conductive particles, the titanium oxy salt, and optionally the electrolytic solution and the binder. For embodiments in which more than one pellet is used, the mixture can be pressed to form the pellets. The pellet (s) are adjusted within the battery 10 using standard processes. For example, in one process, a core rod is placed in the central cavity of the battery 10, and then a punch is used to pressurize the pellet from the highest part. When this process is used, the interior of the wall 18 can have one or more vertical flanges that are circumferentially spaced around the wall 18. These ridges can help retain the cathode 12 in place within the battery 10. In the embodiments in which the cathode 12 is formed of a single pellet, the powder can be placed directly inside the battery 10. A retaining ring is put in place, and an extrusion rod passes through the ring, densifying the powder and forming the cathode 12. The cathode 12 includes manganese dioxide, graphite and / or carbon particles, and a titanium oxy salt. Suitable titanium oxy salts are those that prolong battery life by modifying the discharge process and the products at the cathode when they are included in a battery cathode. A preferred titanium oxy salt is TiOS04 commercially available from Aldrich Chemical as Product No. 33,398-0. Other suitable titanium oxy salts include La2Ti404 (S04) 7, dTi20? .3 (P04)? 6, (Ti0) 2P207, Cd2TiNb06F, PbBi2TiNb08F, a-SrTi0F, Na (1-x) Zn? Ti206F? .8, TIOC12, CaTi204 (OH) 2, VTi03 (OH), CeTi2 (O, OH) 6. The titanium salt is preferably included in an amount of about 0.1 to 5% by weight, based on the total weight of the active material in the cathode. If more than one titanium salt is used the low drain operation is reduced due to the dilution of the Mn02, while if less use of the titanium salt is used there is little effect on the performance or performance of the battery. Any of the conventional forms of manganese dioxide for batteries can be used, such as EMD or CMD. Distributors of such manganese dioxide include Kerr McGee, Co., Broken Hill Proprietary, Chem. Metals, Co., Tosoh, Delta Manganese, Mitsui Chemicals, -JMC, Sedema and Chuo Denki. The conductive particles are selected from the group consisting of carbon powder, graphite, and mixtures thereof. Suitable conductive particles are those that impart conductivity to the cathode material without adversely affecting the other properties of the battery. The cathode preferably contains about 4 to 15 percent of the conductive particles, based on the total weight of the active cathode material. Higher levels can undesirably reduce the amount of active material in the battery, while lower levels may not impart sufficient conductivity. In some embodiments, the cathode 12 may further include an addition of electrolyte solution and / or a binder. The electrolytic solutions are discussed later. Examples of binders for the cathode 12 include polyethylene powders, polyacrylamides, Portland cement and fluorocarbon resin, such as PVDF and PTFE. In certain embodiments, the cathode 12 includes a polyethylene binder sold under the tradename Coathylene HA-1681 (Hoechst). When the cathode 12 includes a binder, the binder preferably constitutes less than about 1 weight percent of the cathode 12, more preferably from about 0.1 weight percent to about 0.5 weight percent of the cathode 12, and most preferably about 0.3 percent by weight of the cathode 12. The cathode 12 can include other additives. Examples of these additives are described in U.S. Patent No. 5,342,712, which is incorporated by reference herein. In certain embodiments, a layer of conductive material can be placed between the wall 18 of the can and the cathode 12. This wall can be placed along the inner surface of the wall 18, along the outer circumference of the cathode 12 or both.

Typically, this conductive layer is formed of a carbonaceous material and, optionally, a binder.

Such materials include LB1000 (Timcal), Eccocoat 257 (W.R. Grace &Co.), Electrodag 109 (Acheson Industries, Inc.), Electrodag 112 (Acheson) and EB005 (Acheson). Methods for applying the conductive layer are described, for example, in Canadian Patent No. 1,263,697, which is incorporated by reference herein. The use of a conductive layer, especially Electrodag 109 or EB005, between the wall 18 and the cathode 12 can reduce the pressure required when the cathode 12 is formed within the battery 10. In this way, the density of the cathode 12 can be made relatively high without causing the pellet (s) to be crushed or cracked when the cathode 12 is formed within the battery 10. However, if the cathode density 12 is too high, an insufficient amount of electrolyte solution can be dispersed within the cathode 12, reducing the efficiency of the battery 10. For example, for a typical size C battery, the cathode 12 has a porosity of about 18% to about 28%, more preferably from about 22% to about 27%, and most preferably of approximately 25%. Here, porosity means the space available for the electrolyte, expressed as a percentage volume of the total geometric cathode volume. In this way, the porosity can be partially or totally filled with the electrolyte. The anode 14 can be formed from any of the standard zinc materials used in battery anodes. Frequently, the anode 14 is formed of a zinc suspension that includes zinc metal particles, alkaline electrolyte, a gelling agent and minor amounts of additives, such as metal plating, inorganic and organic gasification inhibitors. The gelling agents which can be used at the anode 14 include polyacrylic acids, grafted starch materials, polyacrylates, salts of polyacrylic acids, carboxymethylcellulose or sodium 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 Processing Corporation, Muscatine, IA). An example of a polyacrylic acid salt is Alcosorb Gl (Allied Colloids). In some embodiments, the anode 14 preferably includes from about 0.2 percent by weight to about 1 percent by weight of the total gelling agent, more preferably from about 0.4 percent by weight to about 0.8 percent by weight of the total gelling agent , and most preferably from about 0.55 weight percent to about 0.75 weight percent of the 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 U.S. Patent No. 4,777,100, which is incorporated by reference herein. The separator 16 can have any of the conventional designs for battery separators. The electrolytic solution dispersed throughout the battery 10 may be any of the conventional electrolytic solutions used in batteries. Typically, the electrolyte solution is an aqueous hydroxide solution. 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 30 weight percent to about 45 weight percent potassium hydroxide. The aqueous hydroxide solution may optionally contain a small amount of dissolved zinc oxide, typically in the range of about 1 to 4 weight percent.

Example 1 Primary, conventional, Zn / Mn02 alkaline C cells were constructed with the conventional cathode and anode active materials, the electrolyte and the separating membrane. The anode material was in the form of a gelled mixture containing zinc alloy powder, aqueous potassium hydroxide solution, gelling agent (acrylic acid copolymer, Carbopol C940 from B.F. Goodrich), superabsorber (Waterlock A221 from Grain) Processing. Corp.), and surfactant (organic phosphate ester, RM510 from Rhone Poulenc). The separator was a non-woven material of polyvinyl alcohol / rayon, permeable to electrolyte, conventional, laminated to cellophane. The electrolyte was an aqueous solution of potassium hydroxide containing 35% by weight of potassium hydroxide and 2% by weight of zinc oxide. The cathode active material had the following composition: electrolytic manganese dioxide (84.8% by weight), graphite (8.5% by weight), polyethylene binder (0.16% by weight) and 9 N potassium hydroxide solution (6.54% by weight). weight) . The experimental size C cells were also constructed identical to the standard cells except that they contained 1.5% by weight of TiOS04, and the amount of electrolyte manganese dioxide was correspondingly reduced by 1.5% by weight. The total weight of the cathodes in the experimental standard cells was the same. The experimental cells showed a remarkable advantage over standard cells during discharge. The main advantage (4.5-6.5%) was observed in the intermittent ANSI and IEC tests such as the toy test (3.9 Ohms, 1 hour / day), scintillation light test (flash) (3.9 Ohms, 4 minutes / hour , 8 hours / day) and the tape recorder test (6.8 Ohms, 1 hour / day). Other embodiments are within 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 (12)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. An electrochemical cell, characterized in that it comprises: a cathode comprising manganese dioxide and a titanium oxy salt; an anode; and a separator placed between the cathode and the anode.

2. The electrochemical cell according to claim 1, characterized in that the titanium oxy salt is titanium oxysulfate. The electrochemical cell according to claim 1, characterized in that the cathode comprises from about 0.1 to 5.0 weight percent of the titanium oxy salt, based on the total weight of the active material at the cathode. 4. The electrochemical cell according to claim 1, characterized in that the electrochemical cell is an alkaline battery. The electrochemical cell according to claim 1, characterized in that the electrochemical cell is selected from the group consisting of batteries C and batteries D. 6. The electrochemical cell according to claim 1, characterized in that the cathode has a porosity of about 18% to about 28%. 7. The electrochemical cell according to claim 1, characterized in that the anode comprises zinc particles. 8. The electrochemical cell according to claim 1, characterized in that it also comprises an electrolytic solution. 9. A cathode, characterized in that it comprises: manganese dioxide; and a titanium oxy salt. 10. The cathode according to claim 9, characterized in that the titanium oxy salt is titanium oxysulfate. The cathode according to claim 9, characterized in that the cathode comprises from 0.1 to 5.0 by weight of the titanium oxy salt, based on the total active material in the cathode. The cathode according to claim 9, characterized in that the cathode has a porosity of about 18% to about 28%.