JP5142254B2 - Positive electrode plate of lithium ion battery, method for producing the same, and lithium ion battery using the same - Google Patents

Description

  The present invention relates to a positive electrode plate of a lithium ion battery excellent in alkali resistance and a manufacturing method thereof, and a lithium ion battery using the positive electrode plate and a manufacturing method thereof.

  Lithium-ion batteries have a higher energy density per weight and volume than lead batteries and nickel metal hydride batteries, and so can be used as a power source to reduce the weight and size of installed devices. For this reason, recently, there is a trend to use it as a power source not only for portable electronic devices but also for electric vehicles such as EVs and HEVs, and its importance is expected to increase in the future.

  A lithium ion battery is a battery that charges and discharges by a reaction in which lithium ions move between a positive electrode and a negative electrode, and has a three-layer structure of a positive electrode, a separator, and a negative electrode. A lithium / transition metal composite oxide is mainly used for the positive electrode active material, and a carbon-based material is mainly used for the negative electrode active material. Moreover, a polymer porous membrane is used for the separator that separates the positive electrode and the negative electrode, and a non-aqueous solvent is used for the electrolyte.

  A method for producing a positive electrode plate of a lithium ion battery is to prepare a paste in which a positive electrode active material, a binder, and a conductive additive are dispersed and kneaded in a solvent, and the paste is applied to an aluminum foil as a current collector. Is dried to form a positive electrode mixture layer on the aluminum foil.

  Conventionally, an organic solvent such as N-methylpyrrolidone (NMP) has been used as a solvent for the paste. However, water has been used for the purpose of reducing raw material costs and environmental loads. When water is used as the solvent, a part of the lithium ions in the positive electrode active material is eluted and exchanged with protons of water, so that the paste becomes alkaline. Therefore, corrosion of the aluminum foil and generation of hydrogen gas occur when an alkaline paste is applied to the aluminum foil and dried. As shown in FIG. 3, in the positive electrode plate 1, the positive electrode mixture layer 3 expands due to the generation of hydrogen gas 4, resulting in a decrease in electrode density. In addition, there is a problem that the degree of adhesion between the positive electrode mixture layer 3 and the aluminum foil 2 as a current collector is reduced, and battery performance such as battery capacity and internal resistance is lowered.

Patent Document 1 discloses lithium ion intended to prevent corrosion of an aluminum current collector foil by a positive electrode active material paste and to improve the adhesion between the positive electrode mixture layer and the positive electrode current collector foil after drying. A method for manufacturing a positive electrode plate for a battery is disclosed. In this manufacturing method, a boehmite film or a chromium oxide film is formed in advance on the surface of a current collector foil such as aluminum or copper, and then a positive electrode active material paste is applied and dried.
: JP 2000-48822 A

In Patent Document 2, for the purpose of preventing corrosion of the current collector aluminum foil by the positive electrode active material paste, a boehmite film is formed in advance on the surface of the current collector foil made of aluminum, and then the positive electrode active material paste is added. A method for producing a positive electrode plate for a lithium ion battery to be applied and dried is disclosed.
: JP 2003-157852 A

In Patent Document 3, an oxide film having a withstand voltage of 2.1 to 3.0 V is formed in advance on the surface of a current collector foil made of aluminum for the purpose of preventing corrosion of the current collector aluminum foil by the positive electrode active material paste. Then, a method for producing a positive electrode plate for a lithium ion battery in which a positive electrode active material paste is applied and dried is disclosed.
: JP 2005-259682 A

Patent Document 4 describes that, although the purpose is not to improve the alkali resistance with respect to the positive electrode active material paste, the current collector aluminum foil is highly purified in order to impart corrosion resistance to the organic electrolyte. Patent Document 5 also describes that the current collector aluminum foil is highly purified to provide corrosion resistance to the organic electrolyte.
: JP-A-11-97032 : JP-A-6-267542

  The methods of Patent Documents 1 to 3 are effective as methods for imparting alkali resistance to an aluminum foil. However, since it is necessary to add a surface treatment consisting of a plurality of steps to the conventional aluminum current collector foil manufacturing process, an increase in manufacturing cost cannot be denied. Moreover, although the method of patent document 4, 5 is effective as a method of improving the corrosion resistance with respect to organic electrolyte solution, it is effective as a method of suppressing chemical reactivity with an alkaline positive electrode active material paste and bubble generation | occurrence | production. There is no description or suggestion regarding.

  The present invention provides a positive electrode plate for a lithium battery in which a positive electrode mixture layer formed of a positive electrode active material paste is provided on the surface of a current collector made of high-purity aluminum foil, and a method for manufacturing the same. The positive electrode plate according to the present invention has a special effect of being excellent in the adhesion between the aluminum foil and the positive electrode mixture layer while maintaining the alkali resistance of the aluminum foil even if the applied positive electrode active material paste is alkaline. . Moreover, the lithium ion battery using the positive electrode plate according to the present invention has excellent battery performance in battery capacity, internal resistance, and charge / discharge cycle characteristics.

The present invention according to claim 1, wherein the Al purity is 99.9% by weight or more, and at least one of the group consisting of Si, Fe, Cu, Mn, Mg, Zn, Ti, Cr, Zr and V is contained as an impurity And a current collector made of an aluminum foil in which the content of each element in the impurities is less than 0.03% by weight and the total amount of each of the elements is less than 0.1% by weight; And a positive electrode mixture layer formed from an aqueous active material paste having a pH of 10 or more , wherein crystal precipitates present in the aluminum foil have an average of 0.08 to 0.13 μm. Alkali corrosion resistance characterized by having an oxide film having a particle size and an area ratio of 0.5 to 0.7%, and wherein the aluminum foil is formed by a surface treatment including an alkaline degreasing treatment and an acid treatment Li with a Ion was a positive electrode plate of the battery.

According to the second aspect of the present invention, the acid treatment is performed using an acid solution of a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution .

The present invention provides a method for producing a positive electrode plate of a lithium ion battery having alkali corrosion resistance according to claim 1 or claim 2, wherein at least one surface of the aluminum foil is used with an alkaline degreasing solution. The aluminum foil subjected to the alkaline degreasing treatment and washed with water, and subjected to the acid treatment using an acid solution and washed with water, and drying the washed aluminum foil, the at least the aluminum foil forming an oxide film on one surface; the front surface of the aluminum foil oxide film has been formed, forming a positive-electrode mixture layer by drying by applying a pH10 or more aqueous active material paste; the It was set as the manufacturing method of the positive electrode plate of the lithium ion battery provided with the alkali corrosion resistance characterized by including.

According to the present invention, in claim 4, the acid solution is a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution. Furthermore, in the present invention, the alkaline degreasing solution has a pH of 12 to 14, a temperature of 50 to 60 ° C., and an alkaline degreasing time of 3 to 30 seconds. Furthermore, the concentration of the acid solution was 10 to 40% by weight, the temperature was 10 to 35 ° C., and the acid treatment time was 10 seconds to 1 minute.

According to a sixth aspect of the present invention, there is provided a lithium ion battery including the positive electrode plate according to the first or second aspect.

  Content of each element of impurities (Si, Fe, Cu, Mn, Mg, Zn, Ti, Cr, Zr, V, etc.) impairing alkali resistance on the surface of the aluminum foil as a current collector, and the total of impurity elements By regulating the content within a predetermined range, alkaline corrosion of the aluminum foil in the positive electrode active material paste coating step can be suppressed. Furthermore, a new natural oxide film can be formed on the surface of the aluminum foil by once cleaning and drying the surface of the aluminum foil by alkali degreasing treatment and acid treatment. Such a novel natural oxide film increases the alkali resistance of the surface of the aluminum foil and suppresses the generation of bubbles such as hydrogen. As a result, since the density of the positive electrode mixture layer is improved, a lithium ion battery excellent in battery capacity, internal resistance, and charge / discharge cycle characteristics can be provided.

  Hereinafter, the present invention will be described in detail. As shown in FIG. 1, a positive electrode plate 1 according to the present invention has a structure in which a positive electrode mixture layer 3 is provided on at least one surface of a current collector 2 made of aluminum foil (in FIG. 1, the current collector is shown in FIG. 1). 2 is provided with a positive electrode mixture layer 3 on one surface).

A. Aluminum foil The current collector used in the present invention comprises a high-purity aluminum foil. That is, the Al purity is 99.9% by weight or more, and at least one of the group consisting of Si, Fe, Cu, Mn, Mg, Zn, Ti, Cr, Zr and V is contained as an impurity. Here, as an impurity element, if it contains at least one of Si, Fe, Cu, Mn, Mg, Zn, Ti, Cr, Zr, and V, it contains other elements other than these. Also good. The content of each element in the impurities is less than 0.03% by weight, and the total amount of each element is required to be less than 0.1% by weight.

  When the content of each element in the impurity is 0.03% by weight or more, or when the total content of the impurity elements is 0.1% by weight or more and the Al purity is less than 99.9% by weight, the pH is 10 or more. In the aqueous positive electrode active material paste coating step, corrosion easily occurs in the aluminum foil, and as a result, hydrogen gas is generated and the positive electrode mixture layer swells. This causes a decrease in the electrode density of the positive electrode mixture layer and a decrease in the degree of adhesion between the positive electrode mixture layer and the aluminum foil. When such a positive electrode mixture layer is used, battery performance such as battery capacity, internal resistance, and charge / discharge characteristics is deteriorated.

  The aluminum foil used in the present invention is formed into an aluminum foil by subjecting an aluminum ingot to chamfering, homogenization treatment, hot rolling, cold rolling, and foil rolling according to a conventional method. If necessary, intermediate annealing may be performed between cold rolling and foil rolling, and final annealing may be performed after foil rolling.

B. Alkaline degreasing treatment and water-washing treatment of aluminum foil The aluminum foil may be subjected to alkali degreasing using an alkaline degreasing solution. The pH of the alkaline degreasing solution is preferably 12 to 14, and is preferably used at a temperature of 50 to 60 ° C. As the alkaline degreasing solution, for example, Surf Cleaner 420N-2 manufactured by Nippon Paint Co., Ltd. can be used. When the pH of the alkaline degreasing solution is less than 12 or when the use temperature is less than 50 ° C., the degreasing action is insufficient and the degreasing tends to be incomplete or unstable. When the pH exceeds 14 or when the temperature exceeds 60 ° C., the degreasing action is excessively sufficient, and the control of the degreasing amount becomes difficult and the production efficiency is also lowered. The alkaline degreasing treatment is usually performed by spraying an alkaline degreasing solution onto the aluminum foil or immersing the aluminum foil in the alkaline degreasing solution. The treatment time for alkaline degreasing is appropriately selected depending on the pH, concentration, temperature, etc. of the alkaline degreasing solution, but is usually 3 seconds to 30 seconds.

  The alkali degreased aluminum foil is washed with water. The water washing treatment is performed, for example, by spraying water of 10 to 35 ° C. with an electric conductivity of 1 μS / cm or less onto the aluminum foil or immersing the aluminum foil in this water. The water washing time and the amount of water washing are appropriately selected according to the amount of alkali components remaining on the sample surface.

C. The aluminum foil subjected to the water washing treatment after the acid treatment and water washing treatment alkali degreasing treatment of the aluminum foil is subjected to acid treatment using an acid solution. As the acid solution, a nitric acid solution, a hydrochloric acid solution, a sulfuric acid solution or the like is usually used, a nitric acid solution is preferably used, and a nitric acid aqueous solution is most preferably used. The concentration of the acid solution is 10 to 10
40% by weight, preferably 25 to 35% by weight. The temperature of the acid solution is 10 to 35 ° C, preferably 15 to 25 ° C. When the concentration of the acid solution is less than 10% by weight or when the temperature is less than 10 ° C., the effect of the acid treatment is insufficient and the effect of removing the smut tends to be insufficient. When the concentration of the acid solution exceeds 40% by weight or when the temperature exceeds 35 ° C., on the contrary, the action of the acid treatment is too sufficient to control the surface treatment amount and the production efficiency is lowered. The acid treatment time is appropriately selected depending on the concentration and temperature of the acid solution, but is usually 10 seconds to 1 minute.

  The acid-treated aluminum foil is washed with water. The water washing treatment is performed, for example, by spraying water of 10 to 35 ° C. with an electric conductivity of 1 μS / cm or less onto the aluminum foil or immersing the aluminum foil in this water. The water washing time and the amount of water washing are appropriately selected according to the amount of alkali components remaining on the sample surface. The aluminum foil thus washed with water is dried, but is usually dried by air drying at 30 to 60 ° C. Through the above surface treatment, that is, alkali degreasing treatment, water washing treatment, acid treatment, water washing treatment and drying treatment, a new oxide film is formed on the aluminum foil surface in addition to the natural oxide film.

  In the present invention, an alkali degreasing treatment, a water washing treatment, an acid treatment, a water washing treatment, and a drying treatment are not performed, that is, an aluminum foil having only a natural oxide film can be used. An aluminum foil formed with can also be used. When the corrosion resistance needs to be further strengthened by the oxide film by the surface treatment, it is preferable to use such a surface-treated type.

D. Relationship between Al purity and corrosion resistance As a result of intensive studies on the relationship between Al purity and corrosion resistance, the present inventors have obtained the following knowledge. That is, in the high purity aluminum material of 99.9% by weight or more used in the present invention, even if it has only a thin natural oxide film of about several nm, it can exhibit effective alkali resistance in a short time. It is.

  Such knowledge can be interpreted as follows. In general, an additive element of an aluminum alloy hardly affects the formation of a surface oxide film and the corrosion resistance when dissolved in a solid solution. However, crystal precipitates are usually present in aluminum alloys. These cause discontinuities at the interface with the matrix and cause defects in the surface oxide film, which adversely affects the corrosion resistance. Moreover, these crystal precipitates can form a matrix and a local battery, and can become a starting point of corrosion.

  In the high-purity aluminum material used in the present invention, the content of impurity elements that form crystal precipitates is extremely small. Therefore, in such a high-purity aluminum material, there are very few defects in the oxide film and local battery formation sites that become the starting point of corrosion, and the oxide film is difficult to be destroyed. Therefore, it has excellent corrosion resistance such as alkali resistance, such as a longer grace period until alkali dissolution starts.

E. Positive electrode plate on which a positive electrode mixture layer is formed First, lithium / transition metal composite oxide such as lithium cobaltate, lithium nickelate and lithium manganate is used as a positive electrode active material, PVDF (polyvinylidene fluoride), SBR as a binder (Styrene butadiene rubber), PTFE (polytetrafluoroethylene) or the like, and a mixture using carbon black, acetylene black, graphite or the like as a conductive additive is dispersed in water and kneaded to prepare a paste. The positive electrode active material paste thus prepared is an aqueous paste having a pH of 10 or higher.

The positive electrode active material paste is applied to at least one surface of the aluminum foil and dried to form a positive electrode mixture layer. The positive electrode active material paste thus applied is usually dried in an atmosphere of 90 to 150 ° C. or air drying.
As described above, a positive electrode plate in which a positive electrode mixture layer is provided on an aluminum foil current collector is manufactured.

F. Lithium Ion Battery A lithium ion battery using the aluminum foil according to the present invention as a current collector is shown in FIG. The lithium ion battery 5 is manufactured as follows. First, an electrolytic solution 6 in which lithium hexafluorophosphate or the like is dissolved in a mixed solvent of propylene carbonate / dimethoxyethane or the like is impregnated into a separator 7 made of polyethylene or the like, and a positive electrode plate 8 and a negative electrode such as graphite are interposed through the separator 7. The plate 9 is combined. In FIG. 2, 10 is a positive terminal, 11 is a negative terminal which is a case, and 12 is a safety valve. Since such a lithium ion battery has high alkali resistance on the surface of the current collector aluminum foil, it has excellent battery characteristics such as battery capacity, internal resistance, and charge / discharge cycle.

In the following, preferred embodiments of the present invention will be specifically described based on examples and comparative examples.
Examples 1-4 and Comparative Examples 1-2
From the molten metal having the composition shown in Table 1, an ingot having a thickness of 500 mm was obtained by a semi-continuous casting method, and the upper and lower surfaces were chamfered by 10 mm. Next, each ingot was subjected to a homogenization treatment at 530 ° C. for 3 hours, subjected to hot rolling at a starting temperature of 530 ° C. to a plate thickness of 3 mm, and then subjected to cold rolling and intermediate annealing at a temperature of 330 ° C. A 2 mm thick rolled plate (foil) was obtained. Then, the aluminum foil for collectors with a thickness of 20 μm was obtained through foil rolling.

  In Examples 2 and 4 and Comparative Example 2, the obtained aluminum foil was subjected to an alkaline degreasing treatment for 30 seconds at a temperature of 60 ° C. using an alkaline degreasing solution in which Nippon Paint Surf Cleaner 420N-2 was adjusted to pH 13. did. Thereafter, it was washed with water at 10 to 35 ° C. with an electric conductivity of 1 μS / cm or less. Subsequently, it was immersed in a 30% by weight nitric acid aqueous solution for 1 minute for acid treatment. Further, this was washed with water having an electric conductivity of 1 μS / cm or less at 10 to 35 ° C., air dried at 30 to 60 ° C. and dried. The samples of Examples 1 and 3 and Comparative Example 1 were not subjected to surface treatment by alkali degreasing, water washing, acid treatment and water washing. In this way, samples with or without surface treatment were produced.

  The following reaction resistance values were measured for each sample produced as described above. The reaction resistance value (Rct) is obtained from fitting of an equivalent circuit of alkali corrosion and an AC impedance measurement result, and is an index of the likelihood of a chemical reaction between the material and the test solution. A larger resistance value indicates that the chemical reaction is less likely to occur, that is, the corrosion resistance is better.

Measurement of reaction resistance A test piece of 2 cm × 5 cm was cut out from each sample. A sample plate was prepared by attaching a support plate to the back surface of the test piece and masking with a masking tape leaving a 1 cm × 1 cm window. A platinum plate was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode. A LiOH aqueous solution adjusted to pH 13 was used as a test solution. The resistance value was measured at a natural potential under the measurement conditions where the measurement temperature was 25 ± 1 ° C., the amplitude was ± 10 mV, the frequency range was 100 kHz to 100 Hz, and the sampling was 5 points / decade. The results were expressed in a Nyquist plot, and the reaction resistance value (Rct) was determined from fitting with an equivalent circuit of alkaline corrosion.

  Next, a sample of a positive electrode plate in which a positive electrode mixture layer was formed on the surface of a sample that was or was not subjected to surface treatment on an aluminum foil was prepared, and an electrode density test was performed.

  First, a positive electrode mixture paste was prepared. Lithium nickelate was used as the active material, acetylene black as the conductive material, PTFE dispersion as the binder, and water as the solvent. The composition was 87 parts of active material, 10 parts of conductive material, and 3 parts of binder. The solvent water was 75 parts relative to the total amount of these solids. Moreover, 1-2 parts of thickeners (carboxymethylcellulose etc.) were added with respect to the total amount of solid content as needed. These components were mixed and sufficiently kneaded with a disper to prepare a positive electrode mixture paste. When confirmed with a pH meter, the pH of the paste was 12.1. Next, after applying a predetermined amount of the positive electrode mixture paste prepared as described above to the aluminum foil sample with or without the surface treatment, drying is immediately started at 100 ° C., and the drying is finished within 10 seconds. Thus, a positive electrode plate sample was produced.

  The following electrode density ratio was measured for each sample of the positive electrode plate thus produced. Since the electrode density is obtained from the thickness of the positive electrode mixture layer corresponding to the amount of hydrogen generated by corrosion, it is an index of the alkali resistance of the material. That is, if the alkali resistance of the material is good, there is no generation of hydrogen due to corrosion, so the composite layer becomes thin and dense. On the other hand, if the alkali resistance is poor, the composite material layer swells and becomes thick due to hydrogen generation due to corrosion.

Electrode density measurement First, a positive electrode plate sample was embedded in a resin and polished to prepare a cross-sectional observation sample, and the thickness of the positive electrode mixture layer was measured by cross-sectional observation using an optical microscope. Next, as a reference sample, a positive electrode mixture paste was applied to a plastic film (polypropylene, fluororesin, etc.) in the same manner as in each Example and Comparative Example, dried, cross-sectional observation was performed, and the mixture layer thickness was measured. .
In each example and comparative example sample and reference sample, the reciprocal of the measured thickness was used as an electrode density index, and the ratio of the electrode density index of each example and comparative example to the electrode density index of the reference sample was determined. The ratio was used as the electrode density ratio of each example and comparative sample. That is, this electrode density ratio is represented by the thickness of the mixture layer of the reference sample with respect to the thickness of the positive electrode mixture layer of each example and comparative example. This electrode density ratio was used as an index of alkali resistance according to the following criteria.
◎: Electrode density ratio = 90 or more and 100% or less ○: Electrode density ratio = 80 or more and less than 90% Δ: Electrode density ratio = 70 or more and less than 80% ×: Electrode density ratio = 70% or less It was set as the pass which can be used as a positive electrode plate for lithium ion batteries without any problem, and Δ and X were set as rejected.

  Table 1 shows the component element composition, presence / absence of surface treatment, reaction resistance value, and electrode density ratio of each sample.

  From the results of Table 1, all of the aluminum foils for current collectors of Examples 1 to 4 showed a reaction resistance value of 10Ω or more. This shows good alkali resistance because the aluminum foil used contains almost no impurities that hinder the protective ability of the natural oxide film on the surface. On the other hand, in Comparative Examples 1 and 2, the protective ability of the natural oxide film is impaired by a large amount of impurity components contained in the used aluminum alloy (1N30), and the alkali resistance is inferior.

  Similarly, from the results in Table 1, the positive electrode plates of Examples 1 to 4 all passed the electrode density ratio and passed. This indicates that since the used aluminum foil contains a very small amount of impurity components and exhibits good alkali resistance, there is almost no generation of hydrogen and the mixture layer is dense. On the other hand, in Comparative Examples 1 and 2, since the alkali resistance is inferior due to a large amount of impurity components contained in the used aluminum alloy (1N30), hydrogen generation is large and the mixture layer is sparse.

Example 5 and Comparative Examples 3-9
The relationship between Al purity and surface treatment was examined. The sample used was a high-purity aluminum foil used in the present invention (Example 5, Al purity 99.99% by weight, Fe content 0.0011% by weight, Si content 0.0011% by weight, Cu content 0. 0043 wt%, Mg content 0.0001 wt%, Cr content 0.0001 wt%), JIS standard aluminum alloy 1050 (Comparative Example 3), 1N30 (Comparative Example 4), 1100 (Comparative Example 5), 3004 Aluminum foil processed from (Comparative Example 6), 5052 (Comparative Example 7), 5182 (Comparative Example 8), and 6061 (Comparative Example 9) was used.

  First, each of these samples was subjected to an alkaline degreasing treatment for 30 seconds at a temperature of 60 ° C. using an alkaline degreasing solution (Nippon Paint Surf Cleaner 420N-2) adjusted to pH 13. Thereafter, it was washed with water having a conductivity of 1 μS / cm or less and 10 to 35 ° C. Subsequently, it was immersed in a 30% by weight nitric acid aqueous solution for 1 minute for acid treatment. Further, this was washed with water having a conductivity of 1 μS / cm or less at 10 to 35 ° C., air-dried at 30 to 60 ° C. and dried. Then, these samples were immersed in an alkaline aqueous solution (LiOH aqueous solution) having a pH of 13, and the time until foaming occurred on the sample surface was measured. The results are shown in Table 2.

  As is clear from Table 2, it was shown that the high-purity aluminum foil used in the present invention has a longer time to foam than other Al alloys not having high purity. In such a high-purity aluminum material of 99.9% by weight or more used in the present invention, even if the natural oxide film to be formed is as thin as several nanometers, it can be used for a short time of 20 seconds or less. It has been found that effective resistance against alkalinity can be exhibited.

  Thus, the difference in the time until foaming occurs is considered to be due to the amount of crystal precipitates present in the aluminum alloy. In other words, this crystal precipitate causes a discontinuous portion at the interface with the matrix to cause defects in the surface oxide film, or the formation of a matrix and a local battery reduces the corrosion resistance. Accordingly, the crystal precipitates present in the aluminum foil samples not subjected to the surface treatment used in Examples 1 and 2 and Comparative Examples 1 and 2 (hereinafter referred to as “aluminum foil base material”) were observed.

(1) A reflected electron image was taken using an SEM. Ten fields of view were photographed at an observation magnification of 1000 times. The photographed image was binarized from the compound and matrix using an image analyzer, and the particle size and distribution state of the compound were examined. In the aluminum foil base materials of Examples 1 and 2, the average particle size is 0.08 μm to 0.13 μm, the compound area ratio is 0.5 to 0.7%, and in the aluminum foil base materials of Comparative Examples 1 and 2, the average particle size is The diameter was 1.9 μm to 2.0 μm, and the compound area ratio was 1.1 to 1.2%.
(2) These aluminum foil base materials were dissolved in hot phenol, and the filter residue after filtration was dissolved in hydrofluoric acid. The concentration of dissolved element was determined by ICP. A filter having a pore size of 1 μm and 0.1 μm was used. In the aluminum foil base materials of Examples 1 and 2, Fe = 0.3 ppm, Si = 0.6 ppm, and Cu = 0.1 ppm. In the aluminum foil base materials of Comparative Examples 1 and 2, Fe = 140 ppm, Si = 13 ppm, and Cu = 3 ppm.

  From the above results, it was found that the high-purity aluminum foil used in the present invention has a crystal grain size smaller than that of a conventional aluminum foil made of an aluminum alloy and a narrow distribution region. Furthermore, it has been found that the high-purity aluminum foil used in the present invention has a lower content of impurity elements that become crystal precipitates than an aluminum foil made of a conventional aluminum alloy.

  As described above, since the high-purity aluminum material used in the present invention contains a very small amount of impurities that become crystal precipitates, the generation of defects in the oxide film is reduced, and the local battery formation site that is the starting point of corrosion Is hardly present, and the oxide film is hardly broken. As a result, there is an advantageous effect that the grace period until alkali dissolution starts becomes longer and the alkali resistance is excellent.

  Since the aluminum foil used for the positive electrode plate according to the present invention is excellent in alkali resistance, the corrosion reaction due to the aqueous positive electrode active material paste can be suppressed. As a result, the electrode density of important physical properties required for the positive electrode of the lithium ion battery becomes dense and excellent. The lithium ion battery according to the present invention is excellent in battery capacity, internal resistance, and charge / discharge recycling characteristics.

FIG. 1 is a cross-sectional view of a positive electrode plate according to the present invention. FIG. 2 is a perspective view showing the inside of the lithium ion battery according to the present invention. FIG. 3 is an explanatory diagram illustrating a state in which the positive electrode mixture layer swells due to hydrogen gas generated in the positive electrode mixture layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ......... Positive electrode plate 2 ..... Aluminum foil 3 ..... Positive electrode mixture layer 4 ....... Hydrogen gas 5 ....... Lithium ion battery 6 ........ Electrolyte (impregnation state)
7 ... Separator 8 ... Positive electrode plate 9 ... Negative electrode plate 10 ... Positive electrode terminal 11 ... Negative electrode terminal 12 ... Safety valve

Claims (6)

Al purity is 99.9% by weight or more, and at least one of the group consisting of Si, Fe, Cu, Mn, Mg, Zn, Ti, Cr, Zr and V is contained as an impurity. A current collector made of an aluminum foil having a content of less than 0.03% by weight and a total amount of each element of less than 0.1% by weight; provided on at least one surface of the current collector A positive electrode mixture layer formed from an aqueous active material paste having a pH of 10 or more ,
Crystal precipitates present in the aluminum foil have an average particle size of 0.08 to 0.13 μm and an area ratio of 0.5 to 0.7%.
The aluminum foil, the positive electrode plate of a lithium-ion battery comprising the alkali resistance corrosion, characterized in Rukoto with the oxide film formed by surface treatment comprising an alkali degreasing treatment and acid treatment. The positive electrode plate of a lithium ion battery having alkali-corrosion resistance according to claim 1, wherein the acid treatment is performed using an acid solution of a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution . It is a manufacturing method of the positive electrode plate of the lithium ion battery provided with the alkali corrosion resistance of Claim 1 or 2, Comprising: At least one surface of the said aluminum foil is subjected to an alkali degreasing process using an alkaline degreasing solution, and is washed with water The aluminum foil that has been treated and washed with water is subjected to an acid treatment using an acid solution and washed with water, and the washed aluminum foil is dried to form an oxide film on the at least one surface of the aluminum foil. process and that; alkali resistant, characterized in that it comprises a; on the front surface of the aluminum foil oxide film has been formed, forming a positive-electrode mixture layer by applying and drying the pH10 or more aqueous active material paste A method for producing a positive electrode plate of a lithium ion battery having corrosive properties . The manufacturing method of the positive electrode plate of the lithium ion battery provided with the alkali corrosion resistance of Claim 3 whose said acid solution is a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution . The pH of the alkaline degreasing solution is 12 to 14, the temperature is 50 to 60 ° C., the alkaline degreasing time is 3 to 30 seconds, the concentration of the acid solution is 10 to 40% by weight and the temperature is 10 to 35 ° C. The method for producing a positive electrode plate of a lithium ion battery having alkali corrosion resistance according to claim 3 or 4, wherein the acid treatment time is 10 seconds to 1 minute. A lithium ion battery comprising the positive electrode plate according to claim 1.

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