JPS6211459B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to improvements in silver peroxide batteries using silver peroxide as the main anode material. Conventional alkaline batteries have been known to use an active material based on silver peroxide for the anode and zinc, etc. for the cathode, but silver peroxide has a lower oxygen content than other oxides such as silver oxide. Since the content is large, the discharge performance of batteries using this material is significantly improved. However, silver peroxide has low stability within the battery and gradually decomposes into silver oxide and oxygen, so the oxygen generated during storage of the battery increases the internal pressure of the battery, causing expansion or deformation of the battery. In severe cases, it may even be destroyed. Such decomposition of silver peroxide (also called self-discharge) causes a decrease in the amount of effective silver peroxide, making it impossible to obtain the designed capacitance. This problem of self-discharge rate is particularly important for batteries with long lifespans. The reason for these drawbacks of silver peroxide batteries is thought to be due to the high activity of silver peroxide, which reacts with the alkaline electrolyte in contact with it. In order to eliminate this drawback, US Pat. No. 3,017,448 describes coating the surface of silver peroxide particles with silver lead acid, thereby improving the storage performance of the battery. As a result of various studies on stabilizing silver peroxide batteries, the inventors conducted a test in which various additives were added to the produced silver peroxide in order to stabilize the silver peroxide used as an anode active material. It was discovered that good stability was exhibited when a lead source and an aluminum source were simultaneously added to either the silver peroxide electrode or the alkaline electrolyte of a silver peroxide battery. Disclosed as No. 1984-84428. Subsequently, he discovered that stability could be dramatically improved by simultaneously adding a cadmium component to silver peroxide and a tellurium component to either silver peroxide or the alkaline electrolyte of a silver peroxide battery. No. 55-99418. The present invention is a further improvement of the invention relating to a silver peroxide battery to which a cadmium component and a tellurium component are added. The present invention was achieved by discovering that even better stability could be obtained. Accordingly, an object of the present invention is to provide a silver peroxide battery whose anode is formed using silver peroxide as a main ingredient, and whose stability is significantly improved. According to this invention, in the silver peroxide battery, in addition to containing 0.03% by weight or more of a cadmium component as a metal in silver peroxide as an essential component, and a tellurium component in at least one of the silver peroxide or the alkaline electrolyte, Furthermore, a silver peroxide battery is provided which contains at least one component selected from thallium, mercury, lead, and germanium as a selective component. Among these selected components, thallium and mercury are insoluble in alkali, so they are added to silver peroxide, and lead and germanium are soluble in alkali, so they are added to at least one of silver peroxide or the alkaline electrolyte. Just let it happen. The most preferable silver peroxide to be used is one produced by reacting an aqueous silver nitrate solution with an oxidizing agent such as potassium persulfate in an alkaline solution, but this invention is also applicable to silver peroxide produced by other production methods, such as electrolytic oxidation. However, silver peroxide manufactured by the former method has better results. To make silver peroxide contain cadmium components and other components such as thallium, alkali hydroxide and silver nitrate are reacted in the presence of an oxidizing agent, and the resulting silver peroxide is added to the slurry before overdrying. Although it is convenient to add and mix the cadmium component and other components and then over-dry it, it is also possible to re-disperse the dried silver peroxide in a dispersion medium and add cadmium and other components. Cadmium and other components may be mechanically mixed into the dry silver. Alternatively, the cadmium component and other components may be mixed into the silver nitrate solution, alkaline solution, oxidizing agent, and water used in the silver peroxide manufacturing process, and then the silver peroxide production reaction may occur. . Cadmium component to be included in silver peroxide is 0.03% by weight or more as a metal, if tellurium component is included in silver peroxide, 0.01% by weight or more as metal, thallium, mercury component is to be included in silver peroxide, or lead, When the germanium component is contained in silver peroxide without being contained in the electrolyte, the total amount of components other than cadmium and tellurium must be 0.01% by weight or more. Even when using a combination of the lower limit addition amounts of cadmium (0.03% by weight), tellurium (0.01%), and other components such as thallium (0.01% by weight), the stability of the battery is improved compared to conventional technology that uses cadmium alone. significantly improve. For equivalent stability, use cadmium.
Since it is necessary to use 0.3% by weight or more, it is considered that the addition of these components clearly shows a synergistic effect. Of course, when other elements such as cadmium, tellurium, and thallium are used together, the effect of reducing the amount of oxygen generated is sufficiently effective compared to samples without additives, but if the content of each element is below the above lower limit addition amount, the effect is less effective. The saliency of is insufficient. The upper limit of the amount of cadmium and other elemental components added to silver peroxide is preferably about 10% by weight in total; using an excessive amount will reduce the purity of silver peroxide and reduce the amount of electricity generated. will be invited. However, when used as an extender for forming a battery anode, it is possible to add 10% by weight or more, and even in this case, the stability will not decrease. Furthermore, no significant effect is observed even when the addition of thallium and mercury components exceeds 3% by weight. Examples of cadmium components used include cadmium oxide, cadmium hydroxide, metallic cadmium powder,
Examples include cadmium sulfide, cadmium sulfate, cadmium nitrate, cadmium stearate, cadmium formate, and cadmium selenide, which may be used alone or in combination. Examples of the tellurium component to be used include tellurium dioxide, tellurium trioxide, metallic tellurium powder, telluric acid, tellurite acid, or alkali salts thereof, and these can be used alone or in combination. Also compounds and alloys containing both cadmium and tellurium, e.g.
CdTeO ₃ , CdTeO ₄ , and Cd—Te alloy powders can also be added. The thallium, lead, germanium, and mercury components used may be in any form, similar to the above-mentioned cadmium and tellurium, and may be oxides, metals, salts, or intermetallic compounds. When adding a tellurium component to an alkaline electrolyte, an effect can be seen with addition of 0.01 g/, but in order to obtain a full-scale effect, it is recommended to add 0.02 g/or more, preferably 0.04 g/ or more. In addition, when the concentration of tellurium component is increased, it is observed that the effect decreases, but the effect is recognized when the concentration is 5 g/or less, and 3 g/or less is preferable, and the cadmium component in silver peroxide is 0.3% by weight or less. Time is 1.0
g/or less is desirable. The effect of the lead component and germanium component added to the electrolytic solution is recognized when the total amount thereof is 0.01 g/, and if it is 5 g/or more, no further effect can be expected. These components to be added to the electrolytic solution can be freely selected as long as they are soluble in alkali. As mentioned above, tellurium, lead, and germanium components that are soluble in alkaline electrolyte should not be added to silver peroxide because they become soluble in alkaline electrolyte in the battery even if they are added to silver peroxide. However, when added to an alkaline electrolyte, it exhibits almost the same stabilizing effect.
Therefore, these alkali-soluble tellurium,
The lead and germanium components can also be added separately to both the silver peroxide and the alkaline electrolyte. This invention will be described below with reference to embodiments. Example 1 100 g of dried silver peroxide synthesized using silver nitrate and potassium persulfate in an alkaline solution was poured into 1000 ml of pure water, stirred and dispersed, and CdO was added as a cadmium source and CdO was added as a tellurium source. TeO ₂ and PbO, Tl ₂ O ₃ , GeO ₂ , and HgO were used as lead, thallium, germanium, and mercury sources, respectively, and predetermined amounts were added as an aqueous dispersion, stirred for 10 minutes, and then overdried. In the stability test, the gas generation rate per 240 hours and the content of added components in silver peroxide were measured at 40°C in a 40% by weight aqueous potassium hydroxide solution. The results are shown in Table 1.

【table】

[Table] Among the comparative examples of Test Nos. 1 to 11, No. 1 to No. 7 contain no additive components at all, but only one kind, and Test Nos. 8 to 11 contain cadmium and tellurium. There is no product that contains only one type and has a gas generation rate of 250 μ/g/240 hours or less. Test No. 12 and below show examples of the present invention, and Test No. 12 to 15 are at the lower limit of addition of the present invention, but compared to Test No. 11, which only added cadmium and tellurium. It shows a significantly improved value, and even the addition of extremely small amounts of lead, thallium, germanium, and mercury shows a synergistic effect. Test Nos. 16 and 17 added 0.05% of lead, thallium, and other additives to Test No. 9, and Tests No. 18 to 22 added about 0.10% to Test No. 8 to remove only cadmium and tellurium. The gas generation rate is significantly lower than in the case of addition. Test Nos. 23 to 26 involve large amounts of lead and thallium in addition to cadmium and tellurium, but the results show that no further improvement can be expected even if more than these are contained. Example 2 In a reaction to synthesize silver peroxide using silver nitrate and potassium persulfate in an alkaline solution, the raw material silver nitrate solution was made weakly acidic with nitric acid, and the additives cadmium and tellurium were added to the oxide. and other additive components such as thallium,
Silver peroxide was produced by adding and dissolving lead, germanium, or mercury in the form of oxides. Example 1
The gas generation rate was measured in the same manner. The results are shown in Table 2.

[Table] From the results in the above table, whether the additive is added after silver peroxide is formed or added in advance during the manufacturing process, the results are almost the same compared to Test Nos. 18 to 21 in Table 1. It turned out that it was possible to make progress. In this test, a 40% aqueous sodium hydroxide solution was used as the alkaline solution for gas generation rate measurement, and values were obtained at 40°C for 240 hours, and results almost similar to those in the table above were obtained. Example 3 100 g of dried silver peroxide synthesized using silver nitrate and potassium persulfate in an alkaline solution was poured into 1000 ml of pure water and stirred to disperse it well. CdO was used as a cadmium source, and Tl ₂ O ₃ was used as a thallium source if necessary, and predetermined amounts of each were added as an aqueous dispersion, stirred for 10 minutes, and then overdried. On the other hand, tellurium dioxide was added to a 40% by weight aqueous potassium hydroxide solution, which corresponds to the battery electrolyte, to give a predetermined tellurium concentration, and if necessary, lead was added.
A germanium source is added in the form of an oxide, and the concentration of silver peroxide containing each additive component in this solution at 40°C is 240°C.
The gas generation rate per hour was measured. The results are shown in Table 3.

【table】

[Table] From the results in the table above, the alkali-soluble tellurium, lead,
Similar effects on stability have been shown when germanium is added to an alkaline solution without being included in silver peroxide. In Test Nos. 31 to 38, sufficient synergistic effects were exhibited even with the addition of a small amount of tellurium when thallium was used in combination. However, regarding this combination, test No. 36
When the cadmium in the silver peroxide is as low as 0.3%, the performance seems to deteriorate slightly even if the tellurium in the electrolyte is 1.0g/. For No. 37 and 38, if cadmium is 1% or more, tellurium is 3.0 g/min without any problem, and for No. 39 and 40, tellurium is 5.0 g//
Although it is possible, 6.0g/ is shown to be too much. Test Nos. 42 to 45 showed good stability when lead or germanium was added to the alkaline electrolyte.

Claims (1)

[Scope of Claims] 1. In a silver peroxide battery in which the anode is formed using silver peroxide as a main ingredient, silver peroxide contains a cadmium component of 0.03% by weight or more as a metal, and a tellurium component is added to silver peroxide or an alkaline electrolyte. It consists of containing at least one component and further containing at least one component selected from thallium, mercury, lead and germanium, in which case thallium and mercury components are individually or in total amount as metals.
A silver peroxide battery, characterized in that lead and germanium components are added to silver peroxide in an amount of 0.01% by weight or more, and lead and germanium components are added to at least one of silver peroxide or an alkaline electrolyte. 2 Claim 1, wherein the tellurium component contained in silver peroxide is 0.01% by weight or more as a metal.
The silver peroxide battery described in section. 3. Lead and/or contained in silver peroxide
The silver peroxide battery according to claim 1, wherein each germanium component is contained individually or in total in an amount of 0.01% by weight or more as a metal.