JP3516416B2 - Coated tin oxide fiber and electrode active material comprising the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode active material, more specifically to a lead storage battery electrode active material having a high utilization rate, and a coated tin oxide fiber used therefor.

[0002]

2. Description of the Related Art Lead acid batteries are widely used as mobile secondary batteries mounted in automobiles or the like, or backup secondary batteries for computers and the like. However, when the charge / discharge cycle is repeated, the conductivity decreases due to the generation of lead sulfate or lead monoxide on the surface of lead dioxide, which is the positive electrode active material, or lead, which is the negative electrode active material, and the softening of the electrode active material There remains a problem that the life is shortened due to the decrease in conductivity or the dropping of the electrode active material. Lead sulfate, which is the positive electrode active material, and lead sulfate, which are formed on the surface of the negative electrode active material, and lead monoxide are inherently insulative, so if they are formed on the surface of the electrode active material, the conductivity of the electrode active material is changed. It significantly lowers and makes it difficult to use the positive electrode active material and the negative electrode active material (hereinafter sometimes simply referred to as active material) inside, which should be able to contribute to the reaction. This reduces the utilization rate of the active material to 40% or less, which is the reason why the original performance of the lead storage battery cannot be sufficiently obtained. If the utilization rate of the active material can be increased, the energy density of the lead storage battery can be increased, and the application field of the lead storage battery can be further expanded. Recently, in order to suppress the decrease in the conductivity of the active material and improve the utilization rate of the active material to increase the energy density, it is necessary to add conductive graphite or tin oxide powder to the active material. Is being attempted.

[0003]

However, since graphite is easily oxidized and consumed, the effect of imparting conductivity cannot be maintained especially when it is added to the positive electrode active material. In addition, tin oxide, which has been tried to be added, has a small effect of imparting conductivity because it is a powder, and in order to impart sufficient conductivity, it is unavoidable to add a large amount, and the energy density of the battery decreases. There was a problem.

Therefore, another effective method for increasing the utilization rates of the negative electrode active material and the positive electrode active material has been strongly demanded.

[0005]

Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that lead oxide or a coated tin oxide fiber whose surface is coated with lead is used as a positive electrode active material or a negative electrode active material. It was found that when used as a substance, the utilization factor of the active material was improved and the durability in an aqueous sulfuric acid solution was also high, and the present invention was completed here.

[0006] That is, the present invention is a lead oxide obtained by coating the surface of a tin oxide fiber mainly composed of polycrystalline tin oxide and a metal oxide of Group V of the periodic table with lead oxide or lead.
A coated tin oxide fiber for an electrode active material for a storage battery .

[0007]

Another invention is an electrode active material comprising the coated tin oxide fiber.

Next, the present invention will be described more specifically.

In the present invention, the tin oxide fiber used as the lead oxide or the electrode active material substrate coated with lead is mainly composed of polycrystalline tin oxide and a metal oxide of Group V of the periodic table (hereinafter simply referred to as Group V metal oxide). It is a component.
The composition ratio of the Group V metal oxide has a great influence on the conductivity of the obtained tin oxide fiber. The composition ratio can be arbitrarily changed depending on the desired conductivity,
In order to make the active material substrate, the specific resistance of tin oxide fiber is usually 5 × 10 ² Ω · cm or less, preferably 2 × 1.
It is preferably 0 ² Ω · cm or less. The lower limit varies depending on the manufacturing method, but it is generally from ^{1x10 -2} Ωcm to 1x1.
It is set to 0 ^-3 Ω · cm. Therefore, the constituent ratio of the Group V metal oxide is usually 0.05 mol% to 25 mol%, preferably 0.1 mol to 20 mol%. Specific resistance is 5 × 10 ² Ω
- Beyond cm also charge and partial lower conductivity than the resistivity of the lead sulfate, but because it may becomes necessary to reduce the current density in the battery or electrolyte, the resistivity is 5x1
It is preferably 0 ² Ω · cm or less. Since the Group V metal oxide is generally present in solid solution in tin oxide, a peak peculiar to the Group V metal oxide is not observed by X-ray diffraction, but it may be contained even if it is not dissolved. is there.

The compound used for the electrode active material substrate in the present invention
The synthetic tin oxide fiber may be composed mainly of polycrystalline tin oxide, silica and a Group V metal oxide .
Yes. As described above, the Group V metal oxide is contained for the purpose of imparting conductivity, and the silica is contained for the purpose of increasing the mechanical strength of the obtained composite tin oxide fiber. In consideration of these physical properties, polycrystalline tin oxide is usually 20 to 98 mol%, silica is 2 to 80 mol%, and a Group V metal oxide 0.01
Mol% to 24.5 mol%, preferably 50 to 95 mol% of polycrystalline tin oxide, 5 to 50 mol% of silica, and 0.05 to 19 mol% of Group V metal oxide. Also in the composite tin oxide fiber, the Group V metal oxide is usually present as a solid solution in tin oxide. On the other hand, it is presumed that a part of silica is present as a solid solution in tin oxide, but most of the silica is not present in tin oxide as a solid solution and is present in a dispersed state in a mixture.

The composition ratio of the Group V metal oxide or silica in the (composite) tin oxide fiber can be confirmed by chemical analysis or fluorescent X-ray analysis, but is usually calculated by theoretical calculation from the raw material ratio. When the manufacturing raw material ratio is clear, it can be calculated from the raw material ratio.

Examples of the Group V metal oxides include oxides of vanadium, niobium, tantalum, antimony, bismuth, etc. Among them, antimony oxides are preferable in order to enhance conductivity.

The (composite) tin oxide fiber of the present invention is further provided with alumina, calcium oxide, barium oxide, in order to impart flexibility and control the crystallite size.
Strontium oxide, magnesium oxide, zinc oxide, neodymium oxide, lanthanum oxide, gallium oxide, samarium oxide, indium oxide, zirconium oxide, titanium oxide, germanium oxide, etc. are usually used based on all components.
It can be contained at a mol% or less.

When used as the electrode itself, a noble metal such as platinum, ruthenium, iridium, rhodium, palladium, gold, silver or osmium can be contained in the form of metal or oxide. The composition in that case may be appropriately determined according to the purpose, and usually 8 mol% or less based on all components can be contained.

Further, in order to improve compatibility with the grid containing lead as a main component and the active material, it is also preferable to further contain an oxide of lead in an amount of usually 8 mol% or less based on all components.

The tin oxide constituting the (composite) tin oxide fiber of the present invention is polycrystalline, but the crystallite size is usually 30 nm or less on average, and 15 n on average depending on the production method.
It is as small as m or less, and is highly uniform and dense. For this reason, it has been clarified that it exhibits sufficient chemical resistance even to a sulfuric acid aqueous solution used as an electrolyte of a lead storage battery.

The fiber diameter of the (composite) tin oxide fiber in the present invention can be controlled to about 5 μm to several mm, and the variation can be controlled to ± 20% or less, further 10% or less. Furthermore, the fiber length is
It is possible to obtain almost infinite lengths by continuous spinning, and to obtain arbitrary lengths by cutting. When used as an electrode active material substrate, the tin oxide fiber preferably has a diameter of 5 to 70 μm, more preferably 5 to 50 μm. 5
Even if it is smaller than μm, it can be used as an electrode active material substrate, but it is difficult to handle. Further, even if it is larger than 50 μm, it can be used as an electrode active material substrate, but it is preferably 50 μm or less in consideration of the flexibility of the fiber. The length of the fiber may be appropriately determined depending on the intended electrode active material substrate. For example, the (composite) tin oxide fiber may be processed into a woven fabric and used as an electrode active material substrate, and lead oxide or lead may be coated thereon to form an electrode active material. In this case, the (composite) tin oxide fiber serves as an electrode active material substrate and also serves as a current collector. Alternatively, after coating lead oxide or lead on (composite) tin oxide fiber, cutting to about 0.5 mm to 30 mm, crushing, adding water and sulfuric acid, mixing and kneading to form a paste, and made of a lead alloy or the like In some cases, the electrode plate is held by a grid-shaped electrode plate that also serves as a current collector, and then subjected to aging, drying, and chemical conversion steps to form an electrode plate.

Since tin oxide has the same rutile structure as β-PbO ₂ , it is particularly preferable when it is used as a substrate of a positive electrode active material because it is particularly familiar and has high adhesion strength. In addition, in the conventional tin oxide whiskers in which only specific crystal planes appear, dissolution / dissolution of the electrode active material due to charge / discharge cycles
While repeating the precipitation process, the morphology of the electrode active material in contact with the tin oxide whiskers loses reversibility and causes anisotropy,
As a result, there is also a problem that the discharge capacity tends to be small, so it is advantageous that the tin oxide constituting the (composite) tin oxide fiber is polycrystalline. It is also conceivable to use glass fiber or potassium titanate whiskers coated with conductive tin oxide as the electrode active material substrate, but uniform coating is difficult and the conductivity is low,
Moreover, since the adhesion strength is low, kneading during electrode production
Alternatively, it has been found that the coating is peeled off during the severe charge / discharge cycle of the battery in sulfuric acid to lower the conductivity, which is not preferable. It is also possible to coat the carbon fiber with tin oxide, but when it is used as a positive electrode active material, it is not preferable because it is oxidized and consumed to lower the conductivity and the adhesion strength is not high.

Next, a typical production method of the (composite) tin oxide fiber used as the electrode active material base material of the present invention will be illustrated. Oxidation from a solution (spinning solution) having spinnability obtained by mixing and dissolving a tin compound such as tin halide and a compound of Group V element of the periodic table or further silicon alkoxide in alcohol and concentrating the mixture. By spinning a gel fiber containing tin and heat-treating it, a (composite) tin oxide fiber having an arbitrary aspect ratio can be obtained easily and at low cost.

Specific examples of the alcohol include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, octyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, ethylene glycol, 1-methoxy-2-. Propyl alcohol, methoxyethoxy ethanol, 2-phenylethyl alcohol,
Benzyl alcohol, allyl alcohol, 2-methyl-2-propen-1-ol, 3-methyl-3-buten-1-ol and the like can be mentioned. In particular, methyl alcohol and ethyl alcohol are preferable because of high solubility of the tin halide compound. The above alcohols are usually used alone, but a mixture of two or more kinds of alcohols can be used in order to control the reactivity with the tin halide compound or the solubility of the tin halide compound.

The halogen of the tin halide compound is C
l, Br, I, F atoms. Among these tin halide compounds, tin chloride and tin bromide are preferable in terms of price and stability. Specifically, SnCl ₂ , SnCl ₂ ·
2H ₂ 0, SnBr ₂ , SnI ₂ , SnF _{2 and the} like,
In particular, SnBr ₂ , SnCl ₂ · 2H ₂ O and SnCl ₂ are preferably used. Further, the tin halide compound modified with an organic compound, for example, Sn (CH ₃ ) ₂ C
l ₂ etc. can also be used.

The mixing ratio of the tin halide compound and the alcohol is not particularly limited as long as the tin halide compound is uniformly dissolved in the alcohol. However,
If the proportion of the tin halide compound is too low, it does not show spinnability, so it is necessary to concentrate it considerably.
Is wasted. If the tin halide compound concentration is too high, precipitation will occur and a uniform spinning solution cannot be obtained. Therefore, the tin halide compound used and the alcohol
The mixing ratio varies depending on the kind of the alcohol, but generally, the molar ratio of the tin halide compound to the alcohol is preferably 0.02 to 0.5. After mixing in this ratio to form a transparent and uniform solution, the alcohol is further evaporated to concentrate the solution to obtain a spinning solution having a desired viscosity and spinnability.

Further, in the present invention, in order to enhance the mechanical strength of the finally obtained (composite) tin oxide fiber and further enhance the moisture resistance of the gel fiber after spinning,
Silicon alkoxide can also be added to the alcohol solution. As the silicon alkoxide, general formulas Si (OR _A ) ₄ , R _B Si (OR _A ) ₃ , R _B R _C Si (O
_A silicon alkoxide represented by R _A ) ₂ is used.
Here, R _A , R _B , and R _C are each a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group; an ethenyl group, a propenyl group, a butenyl group, and a pentenyl group. A linear or branched alkenyl group such as a group; an aryl group such as a phenyl group.

Specific examples of silicon alkoxides include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane and n-. Butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-
Octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, amyltriethoxysilane, phenyltriethoxysilane, n-octyltriethoxysilane, n-octadecyltriethoxysilane, n-dodecyltriethoxysilane, methyltributoxysilane , Ethyltributoxysilane, ethyltripropoxysilane, vinyltriethoxysilane, allyltriethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldiethoxysilane, diethyldimethoxysilane, ethylmethyldiethoxysilane and the like.

By adding these silicon alkoxides, it is possible to spin fibers having a large major axis stably even in a high humidity atmosphere.
In addition, since the phenomenon that the gel fiber immediately after spinning is softened and collapsed can be reduced, the handling becomes very easy. Furthermore, the mechanical strength of the finally obtained fiber is improved.

The amount of these silicon alkoxides added may be determined in advance so that the final form of silica produced by spinning and heat treatment has a composition ratio within the above range. Usually, the molar ratio of the raw materials used matches the molar ratio of silica in the (composite) tin oxide fiber.

In order to enhance the conductivity of the (composite) tin oxide fiber, it is necessary to add a compound of a Group V element of the periodic table (hereinafter referred to as a Group V compound) to the spinning solution. The V
The group compound is finally heated to the V group by the heat treatment described later.
It becomes a group metal oxide and forms a solid solution in tin oxide.

Examples of the Group V compound include compounds of Group V elements such as vanadium compounds, niobium compounds, tantalum compounds, antimony compounds, and bismuth compounds.

Specifically, as the vanadium compound, V
Br ₃ , VCl ₂ , VCl ₃ , VCl ₄ , VOBr ₂ , VO
Br ₃ , VOCl ₃ , VF ₃ , VF ₄ , VF ₅ , VI ₃ 6H ₂
Examples of the niobium compound include NbCl ₅ , NbBr ₅ , NbF ₅ , and NbOC.
l ₃ , alkoxides of niobium, tantalum compounds such as TaBr ₅ , TaCl ₅ and tantalum alkoxides, and antimony compounds such as SbCl ₃ and SbC.
Examples include l ₅ , SbBr ₃ , antimony oxychloride, or antimony alkoxide, and examples of the bismuth compound include BiCl ₃ , BiI ₃ , and bismuth alkoxide.

The mixing ratio of the group V compound is determined based on the calculated amount of the group V metal oxide in the (composite) tin oxide fiber in consideration of the desired conductivity.

The method for dissolving the tin halide compound, the Group V compound, the silicon alkoxide and the alcohol is not particularly limited. A method in which alcohol is added dropwise to a mixture of a tin halide compound, a Group V compound, and a silicon alkoxide under stirring, or a tin halide compound, a Group V compound, and a silicon alkoxide are simultaneously or sequentially dissolved in alcohol under stirring. The method etc. can be used.

When used as an electrode active material substrate,
In order to improve compatibility with the active material containing lead as the main component,
Lead oxide may be uniformly dispersed in tin oxide in advance. The lead oxide is preferably dispersed in the form of highly conductive lead dioxide. This (composite) tin oxide fiber in which lead oxide is dispersed is an alcohol soluble typified by basic lead acetate, lead chlorate and the like in a solution of the above tin halide compound, Group V compound, silicon alkoxide and the like and alcohol. It is obtained by spinning a solution prepared by adding and dissolving the lead compound of 1) and performing a heat treatment described later.

The spinning method is not particularly limited, and a conventional spinning method can be used. For example, a method of extruding a spinning solution from a spinning nozzle can be used. The major axis, the diameter, etc. of the obtained fiber can be arbitrarily controlled by adjusting the viscosity of the spinning solution, the nozzle diameter, the speed at which the spinning solution is extruded from the spinning nozzle, and the like.

The heat treatment of the gel fiber obtained by spinning is carried out by converting the gel fiber into an organic solvent such as alcohol,
Or remove water etc. to strengthen the skeleton of the fiber,
In some cases, it is carried out at a temperature for further crystallization. The gel fiber as spun from the spinning solution does not show sufficient mechanical strength as it is. The mechanical strength is developed by heating the gel fiber. The heat treatment temperature is not particularly limited as long as it is within a temperature range capable of imparting mechanical strength to the obtained fiber. When the heat treatment temperature is low, alcohol, water, etc. remain in the fiber, so that sufficient mechanical strength does not occur. On the other hand, if the heat treatment temperature is too high, the decomposition of tin oxide will proceed, or the crystal grains in the fiber will grow too much and the strength will decrease.

When the Group V compound is added to improve the conductivity of the obtained fiber, heat treatment is also required. The gel fiber as it is spun from the spinning solution is an insulator as it is, and conductivity is exhibited by heating the gel fiber. The heat treatment temperature is not particularly limited as long as it is within a temperature range capable of imparting electrical conductivity and mechanical strength to the obtained fiber. Generally, when the heat treatment temperature is low, organic substances such as alcohol, water, etc. remain in the fiber, and the Group V compound does not form an oxide form and does not form a solid solution with tin oxide, resulting in conductivity. Does not occur. If the heat treatment temperature is too high, the group V compound in the fiber is volatilized to lower the conductivity, the decomposition of tin oxide proceeds, the crystal grains in the fiber grow excessively, and the strength decreases. . For the above reason, the heat treatment temperature is preferably in the range of 250 to 1550 ° C. More preferably, heat treatment at a temperature of 300 to 1500 ° C. is preferable.

The heat treatment is usually carried out in air. However, when it is desired to obtain a fiber having particularly high conductivity, the heat treatment is carried out in a reducing atmosphere such as nitrogen, argon, hydrogen or a mixed gas of argon and hydrogen, or in vacuum. Processing can be performed.

Further, during the heat treatment, it is desirable to remove volatile components such as water and alcohol present in the gel fiber by drying in order to obtain a good (composite) tin oxide fiber. Such drying may be performed at the same time as the heat treatment, but it is preferable to perform the drying before the heat treatment in order to obtain a good fiber. In these cases, the drying temperature is preferably as low as possible in order to prevent the occurrence of cracks in the obtained fiber, but when an alcohol having a high boiling point is used as the solvent, it is too low. It takes a long time to dry and is not effective. Generally, the drying temperature is preferably in the range of room temperature to 300 ° C. In this method, the components of the (composite) tin oxide fiber are mixed uniformly in solution,
The resulting (composite) tin oxide fiber is highly homogeneous.
The fiber diameter can also be controlled arbitrarily by controlling the nozzle diameter used and the viscosity of the spinning solution.

Obtained by the method typified above (composite)
The surface of the tin oxide fiber is coated with lead or lead oxide to finally form a coated tin oxide fiber, which is used as an electrode active material. When used as a positive electrode active material, the lead oxide is preferably finally coated as lead dioxide. However, it is not necessarily required to be coated with lead dioxide from the beginning, and lead dioxide may be finally obtained by aging, drying and chemical conversion steps. Also, when used as a negative electrode active material, it is not always required to be coated with lead from the beginning, and lead may be finally obtained by aging, drying and chemical conversion steps. Finally, it is preferable that the coated layer is completely lead dioxide in the case of the positive electrode active material and lead in the case of the negative electrode active material. Some lead monoxide or lead sulfate exists in lead dioxide. In addition, lead monoxide, lead dioxide, or lead sulfate may be partially present in lead.

The lead oxide or lead coating thickness cannot be unconditionally determined because the utilization factor of the active material depends on its porosity, but it is generally preferably in the range of 0.1 μm to 1,000 μm. More preferably, it is 1 μm to 200 μm.
If the thickness is less than 0.1 μm, the amount of the active material decreases, and the energy density of the lead storage battery decreases, which is not practical. On the other hand, if the thickness is too large, the adhesion strength with the (composite) tin oxide fiber is reduced, or a portion that does not contribute to the electrode reaction is formed and the utilization rate of the active material is reduced, which is not preferable. Further, when the (composite) tin oxide fiber is processed into a woven fabric or the like and lead oxide or lead is coated thereon to form an electrode for a lead storage battery, the (composite) tin oxide fiber is in contact with sulfuric acid as an electrolytic solution. It is preferable that the entire surface is covered with lead oxide or lead. On the other hand, lead oxide or a lead-coated (composite) tin oxide fiber is 0.5 mm to 3 mm.
When cut into 0 mm, crushed and mixed to form a paste, which is then held on a grid-like electrode plate made of lead alloy such as lead-antimony alloy or lead-calcium alloy to be used as an electrode active material However, the entire surface of the (composite) tin oxide fiber does not necessarily have to be covered with lead oxide or lead. It may be preferable that a part of tin oxide is exposed in order to maintain the conductive path.

In the present invention, the method of coating the (composite) tin oxide fiber with lead or lead oxide is not particularly limited. For example, since the (composite) tin oxide fiber in the present invention is conductive, lead or lead oxide is deposited by electrodeposition from a plating bath of a solution in which a lead compound such as lead nitrate is dissolved and the pH is adjusted with nitric acid or the like. Or a coating solution represented by a solution prepared by adding an alcohol-soluble lead compound such as basic lead acetate, lead chlorate, or lead alkoxide to a solution of alcohol such as methanol, ethanol, isopropyl alcohol, or methoxyethanol. Examples include a method in which the (composite) tin oxide fiber is immersed in the inside (also referred to as a coating solution) and dried, and then heat treatment is performed to coat the lead oxide. When lead is electrodeposited, a lead tetrafluoroborate bath, a lead hexafluorosilicate bath, a lead carbonate bath or the like can be used in addition to the above plating bath. Alternatively, lead oxide may be deposited and electrolytic reduction may be performed later. On the contrary, it is also possible to deposit lead and subsequently perform electrolytic oxidation to obtain lead oxide. In the case of electrodeposition, the coating thickness can be arbitrarily controlled by controlling the amount of electricity supplied in consideration of the electrodeposition efficiency. The current density during electrodeposition varies depending on the concentration and type of the plating bath used, the temperature of the bath, etc., but may be appropriately determined in consideration of the electrodeposition efficiency of lead or lead dioxide, porosity, adhesion strength, etc. 0.1 mA / cm ² to 200
It may be set in the range of mA / cm ² . The plating bath temperature varies depending on the type of plating bath used, but in general it is 2
It may be set in the range of 0 ° C to 70 ° C. The electrodeposition time varies depending on the current density and the electrodeposition efficiency, but it may be appropriately determined so as to have the above-mentioned coating thickness.

When the (composite) tin oxide fiber is immersed in the coating solution and dried, and then heat-treated, the concentration of the lead compound in the coating solution, the viscosity of the coating solution, the (composite) tin oxide By varying the pull rate of the fiber from the coating solution, any coating thickness can be obtained. More preferably, in order to obtain a coating layer having high adhesion strength, it is preferable to keep the coating thickness of 0.1 μm or less once, and after drying and heat treatment, repeat this step to obtain a desired thickness. preferable. In order to efficiently carry out this repeating step, it is preferable that the drying / heat treatment temperature is as low as possible so that the coating layer will not be dissolved when it is immersed in the coating solution next time. Thirty
It may be set in the range of 0 ° C. The final heat treatment temperature may be set in the range of 300 ° C to 1000 ° C. Then, it can be converted into lead or lead dioxide by electrolytic reduction or electrolytic oxidation.

Since the (composite) tin oxide fiber which is the electrode active material substrate of the present invention can be supplied as a continuous fiber, the above-mentioned coating step can be performed extremely efficiently. In the case of electrodeposition, the (composite) tin oxide fiber cut into several centimeters to several tens of centimeters and bundled can be used for electrodeposition. Alternatively, a woven material may be used for electrodeposition.

The electrode material obtained by coating the surface of the (composite) tin oxide fiber with lead or lead oxide as described above is cut into a range of 0.5 mm to 30 mm and used as an electrode active material. . Alternatively, this fiber can be formed into a woven fabric and used as an electrode active material. Alternatively, the above-mentioned coating may be performed after processing into a woven fabric.

The lead oxide or the lead oxide coated by electrodeposition is active and can be used as it is as the positive electrode active material or the negative electrode active material, but the activity can be further enhanced by further aging, drying and chemical conversion steps. Also, after coating lead oxide or lead on (composite) tin oxide fiber, 0.5 mm to 3 mm
After cutting it to about 0 mm, it is crushed, mixed with water and sulfuric acid, and kneaded to form a paste, which is held on a grid-shaped electrode plate also serving as a current collector made of lead alloy or the like to be used as an electrode plate. In this case, as usual, after holding, aging and drying, electrolytic reduction treatment is performed in the case of a negative electrode active material, and electrolytic oxidation treatment is performed in the case of a positive electrode active material.

[0046]

EFFECT OF THE INVENTION The (composite) tin oxide fiber used in the present invention has high conductivity, and particularly has a crystal structure similar to that of the positive electrode active material, so that it has a strong adhesion strength with lead oxide and, in addition, a high strength in a sulfuric acid aqueous solution. Since it shows corrosion resistance and there is no change in conductivity over time, lead oxide or a coated tin oxide fiber coated with lead has a high utilization factor when used as an active material for a storage battery, and therefore has high durability. It is extremely useful as an electrode active material.

[0047]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 10 g (0.05 mol) of stannous chloride (SnCl ₂ ),
Antimony trichloride (SbCl ₃ ) 0.25 g (0.00
1 mol) and 0.06 g of polyethylene oxide having a weight average molecular weight of 200,000 are added to 100 ml of methanol (2.47).
Mol) to make a uniform and transparent solution, and then 2.75 g (0.013 mol) of tetraethoxysilane was added and dissolved to obtain a uniform solution. This solution was concentrated with a rotary evaporator to obtain a spinning solution composed of a sol having a viscosity of 200 poise. When this spinning solution was extruded from the nozzle by applying pressure and continuously wound on a drum, the spinning speed was 20%.
It was possible to carry out continuous spinning at a speed of m / min without dropping of liquid droplets or yarn breakage. It was also possible to spin from all 10 holes of the nozzle. After standing at room temperature for 1 day resulting off <br/> Aiba chromatography, 1 at a rate of 2 ° C. / min
The temperature was raised to 20 ° C. and the temperature was maintained for 30 minutes. Then, the temperature was raised to 600 ° C. at a rate of 10 ° C./min, and the temperature was maintained for 1 hour for heat treatment. The obtained fiber had a circular cross section with an average of 15 μm, a variation of ± 20%, and a smooth surface. In addition, by fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. In addition, as a result of X-ray diffraction, it was found that the tin oxide was polycrystalline because it had peaks corresponding to a plurality of crystal planes of tin oxide, and no peaks corresponding to antimony oxides were found in the tin oxide. It was confirmed to be a solid solution. Resistivity of the resultant fiber over averaged 20 [Omega · cm.

Next, the stability of this composite tin oxide fiber in a high temperature sulfuric acid aqueous solution was examined. The rate of dissolution of the components increases with stirring [(eg WD Ki
ngery, H.M. K. Bowen, D.M. R. Uhlma
nn, Introduction to Ceram
ics (Introduction to Ceramics), 2nd edition, page 410, John Wiley & Sons], a stability test was performed under well-stirred conditions. First, 0.2 mol of this composite tin oxide fiber was added to 3 mol /
It was placed in a glass sample bottle filled with 3 ml of a dm ³ sulfuric acid aqueous solution. This sample bottle was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) in which the water temperature was kept at 70 ° C. and translated at 1.3 Hz, and the mixture was shaken with stirring to examine the elution amount of tin oxide. Since the amount of elution was so small that it could not be measured by the weight change of the composite tin oxide fiber before and after the test, the sulfuric acid aqueous solution was analyzed by ICP (inductively coupled plasma emission spectrometry). As a result, 10 days after tin, 2
The amount of elution after 3 days is 0 ppm and 3 ppm respectively.
m, 4 ppm, and the specific resistance after 30 days is an average of 20 Ω.
It was found that the durability was high with no change in cm. This indicates that the conductivity is maintained for a long time even in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery.

[0050] Next, the resulting composite tin oxide fiber anodes, a platinum plate in the cathode, using the plating solution was 0.1 mol ^-3 concentration dissolved lead nitrate to an aqueous nitric acid solution of 1Moldm ^-3, 100mA / cm by constant current power supply
^When electrolytically synthesized for 15 minutes at a current density of ² , it was confirmed by X-ray diffraction and gravimetric analysis that 112 mg of lead dioxide was produced on the composite tin oxide fiber. Next, the coated tin oxide fiber coated with lead dioxide was charged in a 1 moldm ^-3 sulfuric acid aqueous solution with a platinum plate as a counter electrode at a current density of 0.25 mA / cm ² for 10 hours, and then a 1 moldm ^-3 sulfuric acid aqueous solution. The discharge capacity until the potential suddenly changed was 1.46 × 10 ^-2 A when discharged with a constant current density of 10 mA / cm ² with a platinum plate as the counter electrode.
It was h. The utilization factor of lead oxide coated on the composite tin oxide fiber was calculated by the following formula: utilization factor (%) = 4.463 × discharge capacity (Ah) × 100
/ Amount of coated lead oxide (g) As a result, the utilization rate was 58%, which proved to be effective as an active material for a lead storage battery.

Example 2 10 g (0.05 mol) of stannous chloride (SnCl ₂ ),
Antimony trichloride (SbCl ₃ ) 0.25 g (0.00
1 mol) and 0.06 g of polyethylene oxide having a weight average molecular weight of 200,000 are added to 100 ml of methanol (2.47).
Mol) to make a uniform and transparent solution, and then 2.75 g (0.013 mol) of tetraethoxysilane was added and dissolved to obtain a uniform solution. This solution was concentrated with a rotary evaporator to obtain a spinning solution composed of a sol having a viscosity of 200 poise. When this spinning solution was extruded from the nozzle by applying pressure and continuously wound on a drum, the spinning speed was 20%.
It was possible to carry out continuous spinning at a speed of m / min without dropping of liquid droplets or yarn breakage. It was also possible to spin from all 10 holes of the nozzle. After leaving the obtained fiber at room temperature for 1 day,
The temperature was raised to 20 ° C. and the temperature was maintained for 30 minutes. After that, the temperature was raised to 700 ° C. at a rate of 10 ° C./min, and the temperature was maintained for 2 hours for heat treatment. The obtained fiber had a circular cross section with an average of 15 μm, a variation of ± 20%, and a smooth surface. In addition, by fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. In addition, as a result of X-ray diffraction, it was found that the tin oxide was polycrystalline because it had peaks corresponding to a plurality of crystal planes of tin oxide, and no peaks corresponding to antimony oxides were found in the tin oxide. It was confirmed to be a solid solution. The specific resistance of the obtained fiber was 20 Ω · cm on average.

Next, 0.2 g of this composite tin oxide fiber
Was placed in a sample bottle filled with 3 ml of a 3 mol / dm ³ sulfuric acid aqueous solution. Water temperature of this sample bottle is 70 ℃
The mixture was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) which was kept at a temperature of 1.3 Hz and moved in translation at 1.3 Hz, and shaken, and the elution amount of tin oxide was analyzed by ICP. As a result, the elution amount of tin after 10 days, 20 days, and 30 days was 4 p, respectively.
It was pm, 4 ppm, and 4 ppm, and the specific resistance after 30 days was 20 Ω · cm on average, showing no change, and the durability was high. This indicates that the conductivity is maintained for a long time even in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery.

[0053] the next obtained composite tin oxide fiber on, by using a plating solution with 0.1 mol ^-3 concentration dissolved lead nitrate to an aqueous nitric acid solution of 1moldm ^-3, 1
When electrolytically synthesized for 15 minutes at a current density of 00 mA / cm ² , it was confirmed by X-ray diffraction that lead dioxide was produced. Next, this coated tin oxide fiber coated with lead dioxide was subjected to 0.25 in a 1 moldm ^-3 sulfuric acid aqueous solution.
10 m after charging for 10 hours at a current density of mA / cm ²
After discharging at a current density of A / cm ² , the utilization rate of lead dioxide coated on the composite tin oxide fiber was determined in the same manner as in Example 1. As a result, the utilization rate was 58%, which proved to be effective as an active material for a lead storage battery.

Example 3 10 g (0.05 mol) of stannous chloride (SnCl ₂ ),
Antimony trichloride (SbCl ₃ ) 0.63 g (0.00
28 mol), and 0.06 g of polyethylene oxide having a weight average molecular weight of 200,000 are added to 100 ml of methanol (2.4
7 mol) to make a uniform and transparent solution, and then 2.75 g (0.013 mol) of tetraethoxysilane was added and dissolved to obtain a uniform solution. This solution was concentrated with a rotary evaporator to obtain a spinning solution composed of a sol having a viscosity of 200 poise. When this spinning solution was extruded from the nozzle by applying pressure and continuously wound on a drum, the spinning speed was 20%.
It was possible to carry out continuous spinning at a speed of m / min without dropping of liquid droplets or yarn breakage. It was also possible to spin from all 10 holes of the nozzle. After leaving the obtained fiber at room temperature for 1 day,
The temperature was raised to 20 ° C. and the temperature was maintained for 30 minutes. After that, the temperature was raised to 600 ° C. at a rate of 10 ° C./min, and the temperature was maintained for 2 hours for heat treatment. The obtained fiber had a circular cross section with an average of 15 μm, a variation of ± 20%, and a smooth surface. In addition, by fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. In addition, as a result of X-ray diffraction, it was found that the tin oxide was polycrystalline because it had peaks corresponding to a plurality of crystal planes of tin oxide, and no peaks corresponding to antimony oxides were found in the tin oxide. It was confirmed to be a solid solution. The specific resistance of the obtained fiber was 5 Ω · cm on average.

Next, 0.2 g of this composite tin oxide fiber
Was placed in a sample bottle filled with 3 ml of a 3 mol / dm ³ sulfuric acid aqueous solution. Water temperature of this sample bottle is 70 ℃
The mixture was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) which was kept at a temperature of 1.3 Hz and moved in translation at 1.3 Hz, and shaken, and the elution amount of tin oxide was analyzed by ICP. As a result, the elution amount of tin after 10 days, 20 days, and 30 days was 3 p, respectively.
pm was 3 ppm, 4 ppm, and the specific resistance after 30 days was 5 Ω · cm on average, showing no change, and the durability was high. This indicates that the conductivity is maintained for a long time even in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery.

[0056] the next obtained composite tin oxide fiber on, by using a plating solution with 0.1 mol ^-3 concentration dissolved lead nitrate to an aqueous nitric acid solution of 1moldm ^-3, 1
When electrolytically synthesized for 15 minutes at a current density of 00 mA / cm ² , it was confirmed by X-ray diffraction that lead dioxide was produced. Next, this coated tin oxide fiber coated with lead dioxide was subjected to 0.25 in a 1 moldm ^-3 sulfuric acid aqueous solution.
10 m after charging for 10 hours at a current density of mA / cm ²
After discharging at a current density of A / cm ² , the utilization rate of lead dioxide coated on the composite tin oxide fiber was determined in the same manner as in Example 1. As a result, the utilization rate was 63%, which proved to be effective as an active material for a lead storage battery.

Example 4 10 g (0.05 mol) of stannous chloride (SnCl ₂ ),
Antimony trichloride (SbCl ₃ ) 0.63 g (0.00
28 mol), and 0.06 g of polyethylene oxide having a weight average molecular weight of 200,000 are added to 100 ml of methanol (2.4
7 mol) to make a uniform and transparent solution, and 4.71 g (0.023 mol) of tetraethoxysilane was added and dissolved to obtain a uniform solution. This solution was concentrated with a rotary evaporator to obtain a spinning solution composed of a sol having a viscosity of 200 poise. When this spinning solution was extruded from the nozzle by applying pressure and continuously wound on a drum, the spinning speed was 20%.
It was possible to carry out continuous spinning at a speed of m / min without dropping of liquid droplets or yarn breakage. It was also possible to spin from all 10 holes of the nozzle. After leaving the obtained fiber at room temperature for 1 day,
The temperature was raised to 20 ° C. and the temperature was maintained for 30 minutes. Then, the temperature was raised to 600 ° C. at a rate of 10 ° C./min, and the temperature was maintained for 1 hour for heat treatment. The obtained fiber had a circular cross section with an average of 15 μm, a variation of ± 20%, and a smooth surface. In addition, by fluorescent X-ray analysis, it was confirmed that antimony and silica were present in the fiber according to the charged composition. In addition, as a result of X-ray diffraction, it was found that the tin oxide was polycrystalline because it had peaks corresponding to a plurality of crystal planes of tin oxide, and no peaks corresponding to antimony oxides were found in the tin oxide. It was confirmed to be a solid solution. The specific resistance of the obtained fiber was 10 Ω · cm on average.

Next, 0.2 g of this composite tin oxide fiber
Was placed in a sample bottle filled with 3 ml of a 3 mol / dm ³ sulfuric acid aqueous solution. Water temperature of this sample bottle is 70 ℃
The mixture was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) which was kept at a temperature of 1.3 Hz and moved in translation at 1.3 Hz, and shaken, and the elution amount of tin oxide was analyzed by ICP. As a result, the elution amount of tin after 10 days, 20 days, and 30 days was 3 p, respectively.
pm, 4 ppm, 4 ppm, and the specific resistance after 30 days was 10 Ω · cm on average, showing no change, and the durability was high. This indicates that the conductivity is maintained for a long time even in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery.

[0059] the next obtained composite tin oxide fiber on, by using a plating solution with 0.1 mol ^-3 concentration dissolved lead nitrate to an aqueous nitric acid solution of 1moldm ^-3, 1
When electrolytically synthesized for 15 minutes at a current density of 00 mA / cm ² , it was confirmed by X-ray diffraction that lead dioxide was produced. Next, this coated tin oxide fiber coated with lead dioxide was subjected to 0.25 in a 1 moldm ^-3 sulfuric acid aqueous solution.
10 m after charging for 10 hours at a current density of mA / cm ²
The utilization factor of lead dioxide coated on the composite tin oxide fiber by discharging at a current density of A / cm ² was determined in the same manner as in Example 1. As a result, the utilization rate was 61%, which proved to be effective as an active material for a lead storage battery.

Example 5 10 g (0.05 mol) of stannous chloride (SnCl ₂ ),
Antimony trichloride (SbCl ₃ ) 0.25 g (0.00
1 mol) and 0.06 g of polyethylene oxide having a weight average molecular weight of 200,000 are added to 100 ml of methanol (2.47).
To obtain a uniform and transparent solution. This solution was concentrated with a rotary evaporator to obtain a spinning solution composed of a sol having a viscosity of 200 poise. When this spinning solution was extruded from a nozzle by applying pressure and continuously wound around a drum, it was possible to continuously spun at a spinning speed of 20 m / min without causing drop of droplets and breakage of the yarn. . It was also possible to spin from all 10 holes of the nozzle. After leaving the obtained fiber at room temperature for 1 day, 2 ° C /
The temperature was raised to 120 ° C. at a rate of min and the temperature was maintained for 30 minutes. Then, the temperature was raised to 600 ° C. at a rate of 10 ° C./min, and the temperature was maintained for 1 hour for heat treatment. The obtained fiber had a circular cross section with an average of 15 μm, a variation of ± 20%, and a smooth surface. Moreover, it was confirmed by fluorescent X-ray analysis that antimony was present in the fiber according to the charged composition. Also,
As a result of X-ray diffraction, it is polycrystalline tin oxide because it has peaks corresponding to a plurality of crystal planes of tin oxide,
No peaks corresponding to antimony oxides were found, and it was confirmed that they were in solid solution in tin oxide. The specific resistance of the obtained fiber was 8 × 10 ⁻¹ Ω · cm on average.

Next, 0.2 g of this tin oxide fiber was placed in a glass sample bottle filled with 3 ml of a ³ mol / dm ³ sulfuric acid aqueous solution. This sample bottle was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) in which the water temperature was kept at 70 ° C. and translated at 1.3 Hz, and shaken to measure the elution amount of tin oxide. Since the amount of elution was so small that it could not be measured by the weight change of the tin oxide fiber before and after the test, the sulfuric acid aqueous solution was analyzed by ICP (inductive coupling plasma emission spectrometry). As a result, 10 of tin
The amount of elution after 4 days, 20 days, and 30 days is 4 pp.
m was 4 ppm, 5 ppm, and the specific resistance after 30 days was 8 × 10 ⁻¹ Ω · cm on average, showing no change and high durability. This indicates that the conductivity is maintained for a long time even in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery.

Then, on the tin oxide fiber obtained, 1
100m by using a plating solution in which lead nitrate is dissolved in a nitric acid aqueous solution of moldm ^-3 to make the concentration 0.1 moldm ^-3.
When electrolytically synthesized at a current density of A / cm ² for 15 minutes,
It was confirmed by X-ray diffraction that lead dioxide was produced. Next, the tin oxide fiber coated with the lead dioxide was treated with 0.25 mA / cm in a 1 moldm ^-3 sulfuric acid aqueous solution.
After charging 10 hours ² of current density, obtained by the utilization of the discharged lead dioxide coated on a tin oxide fiber at a current density of 10 mA / cm ² in the same manner as in Example 1. As a result, the utilization rate was 63%, which proved to be effective as an active material for a lead storage battery.

Comparative Example 1 Otsuka Chemical Co., Ltd. tin oxide coated potassium titanate whiskers (trade name: WK-204, specific resistance: 10 to 100 Ω · c)
m) 0.2 g, 3 mol / dm ³ sulfuric acid aqueous solution 3 ml
In a filled sample bottle. This sample bottle
The mixture was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) in which the water temperature was kept at 70 ° C. and translated at 1.3 Hz and shaken, and the elution amount of the components was analyzed by ICP. As a result, a large amount of titanium was dissolved, and after 10 days, 20 days,
Elution amount after 30 days is 3,000 ppm, 3, 5 respectively
It was 00 ppm and 3,700 ppm. Also, the elution amount of tin is 25 ppm, 28 ppm, and 30 ppm, respectively.
Met. The specific resistance after 30 days was 400 Ω · cm on average, and the conductivity was low. This indicates that the conductivity cannot be maintained for a long period of time in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery. Further, potassium titanate whiskers are powdery by visual observation,
The electrodeposition failed to coat the actual lead dioxide.

Comparative Example 2 0.2 mol of tin oxide-coated titanium oxide powder (trade name W1, specific resistance 5 to 20 Ω · cm) manufactured by Mitsubishi Materials, 3 mol
It was put in a sample bottle filled with 15 ml of a sulfuric acid aqueous solution of / dm ³ . This sample bottle was placed in an incubator (M-100N manufactured by Taiyo Kagaku Kogyo Co., Ltd.) in which the water temperature was kept at 70 ° C. and translated at 1.3 Hz, and shaken, and the elution amount of the components was analyzed by ICP. As a result, 10 days after tin, 2
The amount of elution after 0 and 30 days is 5 ppm and 6 pp, respectively.
m, 6 ppm, and the specific resistance after 30 days is 50 Ω on average.
It was a little higher than cm. This indicates that the conductivity cannot be maintained for a long period of time in a high temperature sulfuric acid aqueous solution which is an electrolytic solution of a lead storage battery. Further, since it is powdery, it was not possible to actually coat lead dioxide by electrodeposition.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/62 H01M 4/56 H01M 4/14 H01M 10/06

Claims (2)

(57) [Claims] 1. An electrode for a lead storage battery in which lead oxide or lead is coated on the surface of a tin oxide fiber mainly composed of polycrystalline tin oxide and a metal oxide of Group V of the periodic table.
Coated tin oxide fiber for active materials . 2. An electrode active material comprising the coated tin oxide fiber according to claim 1 .