JP4507537B2 - Lithium ion secondary battery and manufacturing method thereof - Google Patents

Description

The present invention relates to a lithium ion secondary battery and a method for manufacturing the same. In detail, it is related with the lithium ion secondary battery using the positive electrode active material containing lithium, and its manufacturing method. The present invention also relates to a positive electrode for a lithium ion secondary battery having a positive electrode active material containing lithium . Hereinafter, the “lithium ion secondary battery” is simply referred to as “secondary battery” in the present specification.

  A secondary battery including a positive electrode having a positive electrode active material containing lithium is known. A typical configuration of such a positive electrode includes a configuration in which the positive electrode active material is held in a positive electrode current collector mainly composed of a conductive material such as metal. As the positive electrode active material, an oxide having lithium and a transition metal as constituent elements, such as a lithium / nickel composite oxide or a lithium / cobalt composite oxide, is usually used. As a method for holding the positive electrode active material on the positive electrode current collector, a method including an operation of attaching a paste-like positive electrode active material composition containing an appropriate solvent and the positive electrode active material to the current collector is common. As a solvent constituting such a composition, an aqueous solvent (typically water) tends to be preferred. By using an aqueous solvent, one or two or more effects can be expected among reduction of material cost, simplification of equipment, reduction of waste, improvement of handleability, and the like.

However, when an aqueous solvent is used as a constituent solvent of the composition, lithium may be irreversibly eluted from the positive electrode active material. When such lithium elution occurs, the amount of lithium that can contribute to the battery reaction decreases. As a result, the battery capacity (capacity density) per unit mass of the positive electrode active material tends to decrease.
Patent Document 1 listed below describes a technique for suppressing elution of lithium by limiting the specific surface area of the positive electrode active material. The following patent document 2 is mentioned as another prior art document relevant to this invention. Here, providing a more suitable method for producing a secondary battery with good performance (for example, a secondary battery including a positive electrode active material having a high capacity density) using a positive electrode active material composition containing an aqueous solvent. It is beneficial if you can.
JP 2002-42817 A JP 2000-106174 A

  One object of the present invention is to provide a suitable method for producing a secondary battery using a positive electrode active material composition containing an aqueous solvent. Another object of the present invention is to provide a secondary battery manufactured by such a method. Another related object is to provide a positive electrode active material composition that includes an aqueous solvent and is suitable for manufacturing a secondary battery, and a method for preparing the same. Moreover, it is providing the positive electrode for secondary batteries manufactured by such a method and the method of manufacturing the positive electrode for secondary batteries using such a composition.

The present inventor has found that the above problem can be solved by using a lithium salt that supplies lithium ions to an aqueous solvent, and has completed the present invention.
That is, one of the secondary battery manufacturing method provided by this application is an aqueous solvent, a lithium solution containing lithium salt supplies lithium ions in the aqueous-based solvent, a cathode active material containing lithium wherein And a step of preparing a positive electrode active material composition by mixing a positive electrode active material of a material different from the lithium salt . The manufacturing method can include a step of attaching the composition to the positive electrode current collector.
In the positive electrode active material composition prepared by this method, lithium ions supplied from the lithium salt are present in an aqueous solvent. Thus, by making lithium ions exist (included) in the aqueous solvent, it is possible to suppress a phenomenon in which lithium constituting the positive electrode active material is eluted into the aqueous solvent. Therefore, a secondary battery with better performance can be obtained using the positive electrode active material composition containing the aqueous solvent.

  As the lithium salt, one kind of lithium salt may be used, or two or more kinds of lithium salts may be used in combination. It is preferable to use at least one lithium salt that shifts the pH of the aqueous solvent to the alkali side. Thereby, the phenomenon that the lithium which comprises a positive electrode active material elutes to an aqueous medium can be suppressed more effectively. The lithium salt particularly preferably used is lithium hydroxide (lithium hydroxy salt).

In this manufacturing how, in the preparation step, mixing the positive electrode active material in a lithium solution comprising the lithium salt and the aqueous solvent. According to this aspect, it can suppress more effectively that lithium elutes from a positive electrode active material. In a more preferred embodiment, a lithium solution having a pH of about 10 or higher (typically about 10 to 13.5) and a positive electrode active material are mixed. By using a lithium solution having a pH of about 12 or more (typically about 12 to 13.5), even better results can be obtained.

Further, according to this application, the secondary batteries produced by any of the methods described above is provided. In such a secondary battery, since elution of lithium from the positive electrode active material in the positive electrode active material composition is suppressed, the secondary battery can include a positive electrode active material having a higher capacity density. That is, it can be excellent in battery performance.

  Hereinafter, preferred embodiments of the present invention will be described in detail. It should be noted that technical matters other than the contents particularly mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the technical contents disclosed in the present specification and the common general technical knowledge in the field.

The method of the present invention can be applied to the manufacture of the secondary batteries comprising a positive electrode active material containing lithium. Typically, it is applied to the manufacture of a secondary battery provided with a positive electrode active material substantially composed of an oxide having lithium and a transition metal compound as constituent elements. When the positive electrode active material is substantially composed of a lithium / nickel composite oxide and / or a lithium / cobalt composite oxide, the effect of applying the method of the present invention is exhibited well. This is because lithium constituting such a complex oxide is easily eluted in water. A particularly preferable application target is a secondary battery using a lithium / nickel composite oxide as a positive electrode active material. Further, the present invention is applied to a positive electrode active material composition containing such a positive electrode active material, a positive electrode for a secondary battery provided with the positive electrode active material, a secondary battery configured using the positive electrode, and a method for producing them. be able to.

Here, “lithium / nickel composite oxide” means an oxide having lithium and nickel as constituent metal elements, and at least one other metal element in addition to lithium and nickel (that is, transition other than lithium and nickel) It is meant to include composite oxides containing a metal element and / or a typical metal element. Such a complex oxide can be represented, for example, by the following general formula (1).
LiNi _1-x A _x O ₂ (1)
Here, A in the above formula (1) is cobalt (Co), aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium ( Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum ( It may be one or more metal elements selected from the group consisting of La) and cerium (Ce). Moreover, x in Formula (1) is 0 <= x <= 0.7, Preferably it is 0.1 <x <0.3. Recently, a combination of three or more elements as element A is also used, but the above general formula includes such complex oxides.
Similarly, the lithium-cobalt composite oxide is at least one metal element other than lithium and nickel (for example, Ni, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, It is meant to include composite oxides containing one or more metal elements selected from the group consisting of Cu, Zn, Ga, In, Sn, La and Ce.

  In the above method, a positive electrode active material composition containing an aqueous solvent is used. Here, the “aqueous solvent” refers to water or a mixed solvent mainly composed of water. As a solvent other than water constituting the mixed solvent, an organic solvent (such as a lower alcohol) that can be uniformly mixed with water can be used. Since the solvent constituting the positive electrode active material composition is an aqueous solvent, according to the production method of the present invention, one or two of reduction of material cost, simplification of equipment, reduction of waste, improvement of handleability, etc. The above effects can be obtained. A particularly preferred aqueous solvent is water.

  The positive electrode active material composition used in such a method is prepared using a lithium salt that supplies lithium ions to an aqueous solvent. This lithium salt (hereinafter sometimes referred to as “lithium ion source”) is a material different from the positive electrode active material. For example, lithium salts such as lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium bromide, and lithium chloride can be used. It is preferable to use a lithium ion source that dissolves in water and exhibits alkalinity (that is, a lithium compound that can function as a pH adjuster that shifts pH to the alkali side). One or more of such lithium ion sources can be used in combination with one or more lithium ion sources (for example, dissolved in water and exhibiting almost neutrality). Particularly preferred lithium ion source is lithium hydroxide.

The amount (content) of lithium salt used with respect to the aqueous solvent (typically water) is not particularly limited. For example, about 2 × 10 ^{−4 to} 3.5 × 10 ⁻¹ mol of lithium salt in terms of lithium can be used per 1 liter of aqueous solvent. Usually, it is appropriate to use a lithium salt of about 8.5 × 10 ^{−3 to} 3.5 × 10 ⁻¹ mol / liter, and a more preferable amount is 8.9 × 10 ⁻² to 2 × 10 ^−1. mol / liter. When lithium hydroxide is used as the lithium salt, the preferred amount is about 0.2 to 8.5 g / liter, more preferably about 2 to 5 g / liter. Although it varies depending on the type of the positive electrode active material to be used, usually, when these are mixed in the same amount ratio as the water and lithium salt contained in the positive electrode active material composition, the water has a pH of 10 to 13.5 ( It is preferable to use an amount of lithium salt that can be adjusted to pH 12 to 13.5). For example, when the positive electrode active material contains a lithium / nickel oxide and / or a lithium / cobalt oxide, it is particularly preferable to use the above amount of lithium salt.

  In addition, the said composition can contain the 1 type, or 2 or more types of material used for a general positive electrode active material composition as needed. Examples of such a material include a conductive material, a binder, and a thickener. As the conductive material, for example, a carbon material such as carbon black can be used. As the binder, polytetrafluoroethylene (PTFE) or the like can be used. As the thickener, methyl cellulose (MC), carboxymethyl cellulose (CMC), ethyl cellulose (EC) and the like can be used. Although it does not specifically limit, the usage-amount of the electrically conductive material with respect to 100 mass parts of positive electrode active materials can be 1-15 mass parts, for example. Moreover, the total usage-amount of a binder and a thickener with respect to 100 mass parts of positive electrode active materials can be about 1-10 mass parts, for example.

The positive electrode active material composition can be prepared, for example, by the following method. That is, first, an aqueous solvent (typically water) and a lithium salt are mixed. Thereafter, the positive electrode active material is further mixed. Typically, a lithium solution is prepared by dissolving a lithium salt in an aqueous solvent. This lithium solution and the positive electrode active material are mixed. Here, the liquidity of the lithium solution before mixing with the positive electrode active material is preferably in the range of pH 10 to 13.5, and more preferably in the range of pH 12 to 13.5. Further, the positive electrode active material is preferably mixed in a state where the lithium salt is almost completely dissolved in the aqueous solvent. However, the positive electrode active material may be mixed in a state where a part of the lithium salt remains undissolved.
As another preparation method, a method in which the positive electrode active material and the lithium salt are mixed almost simultaneously with the aqueous solvent can be mentioned. It is also possible to employ a method in which a positive electrode active material and a lithium salt are successively mixed in an aqueous solvent. However, it is preferable to shorten the time during which the aqueous solvent not containing a lithium salt (no lithium ions derived from the lithium salt) and the positive electrode active material contact each other as much as possible. Therefore, it is preferable to mix the lithium salt and the aqueous solvent before mixing the positive electrode active material and the aqueous solvent. Thereby, the effect which suppresses that lithium elutes from a positive electrode active material is heightened.

  In addition, the timing which mixes other materials (conductive material, a binder, a thickener, etc.) mentioned above is not specifically limited. For example, the other material and the positive electrode active material may be mixed with the aqueous solvent almost simultaneously, or the positive electrode active material may be further mixed after mixing the other material with the aqueous solvent. Further, after mixing the positive electrode active material with the aqueous solvent, another material may be further mixed.

  The positive electrode active material composition thus prepared is suitable as a composition for producing (manufacturing) a positive electrode for a secondary battery (typically a lithium ion battery). A preferred production example of such a positive electrode will be described. First, the composition is attached to a positive electrode current collector mainly composed of a conductive material such as metal (aluminum material or the like). As a method for this attachment, a method of immersing the positive electrode current collector in the above composition, a method of applying the above composition to the positive electrode current collector, or the like can be used. For example, a method of coating using a comma coater, a die coater or the like, or a method of brush coating, spray coating or the like can be employed. Thereafter, the solvent is removed from the composition attached to the positive electrode current collector to form a layer containing the positive electrode active material (positive electrode active material layer) on the surface of the current collector. This layer is pressed if necessary. In this manner, a positive electrode having a positive electrode active material (positive electrode active material layer) on the surface of the positive electrode current collector can be produced. In addition, when using the positive electrode electrical power collector comprised with the material (especially aluminum material) which is easy to corrode at high pH, it is preferable to remove a solvent in as short time as possible after application | coating of a composition. This is because corrosion of the positive electrode can increase the internal resistance of the battery.

A positive electrode for a secondary battery produced using the positive electrode active material composition can be preferably used as a constituent material of a secondary battery together with an appropriate negative electrode and an electrolytic solution. As the negative electrode, a negative electrode active material containing one or more negative electrode active materials used in conventional lithium ion secondary batteries such as amorphous carbon and graphite carbon on the surface of a metal (copper material, etc.) negative electrode current collector. Those provided with a material layer can be used.
In addition, as the electrolytic solution, a nonaqueous electrolytic solution used in a conventional lithium ion secondary battery can be used. For example, one or two of propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. Solvent compounds including LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _3, etc. An electrolyte or the like in which one or more of (salt) is dissolved can be used.

One preferred embodiment of the secondary batteries Manufacturing method according to the present invention includes a positive electrode having the positive electrode active material composition is deposited on the positive electrode current collector sheet, the positive electrode active material on the surface of the positive electrode current collector sheet The process of producing. Moreover, it has the process of preparing the negative electrode sheet which has a negative electrode active material on the surface of a sheet-like negative electrode collector (metal foil etc.). Moreover, it has the process of preparing a sheet-like separator (separator sheet). As this separator, a sheet made of porous polyolefin (polyethylene, polypropylene, etc.) can be used. And it has the process of superposing | stacking a positive electrode sheet and a negative electrode sheet through a separator sheet, and winding this, and producing an electrode body (winding type electrode body). Furthermore, it has the process of accommodating this winding type electrode body in a container with nonaqueous electrolyte solution. The secondary battery manufactured by such a method can be provided with a positive electrode active material having a higher capacity density because lithium is prevented from being eluted from the positive electrode active material when the positive electrode is produced. That is, it can be excellent in battery performance.

Examples of the present invention will be described below, but the present invention is not intended to be limited to the specific examples.
<Example 1: Preparation and evaluation of positive electrode active material composition>
A positive electrode active material composition was prepared by the preparation methods (preparation conditions) shown in the following experimental examples. In these experimental examples, a lithium / nickel composite oxide (average particle diameter of about 10 μm) represented by the composition formula LiNi _0.7 Co _0.2 Al _0.1 O ₂ was used as the positive electrode active material.

[Experimental Example 1: Preparation of positive electrode active material composition (a)]
As shown in FIG. 1, lithium hydroxide was dissolved in ion-exchanged water to prepare a lithium solution having a pH of about 10 (lithium hydroxide concentration of about 2 × 10 ⁻⁴ mol / liter). To this lithium solution, the positive electrode active material, acetylene black as a conductive material, polytetrafluoroethylene (PTFE) as a binder, and carboxymethylcellulose (CMC) as a thickener were added and mixed. In this way, a paste-like positive electrode active material composition (a) was prepared. This composition contains positive electrode active material: acetylene black: PTFE: CMC at a mass ratio of about 100: 10: 2: 1. Further, this composition contains about 140 g of a positive electrode active material with respect to about 100 cm ^{3 of the} lithium solution.

[Experimental Examples 2 to 5: Preparation of positive electrode active material compositions (b) to (e)]
In Experimental Example 1, the pH of the lithium solution before mixing the electrode constituent materials (positive electrode active material, acetylene black, PTFE and CMC) was adjusted to about pH 11 (Experimental Example 2: Lithium hydroxide concentration of about 1.35 × 10 6). ^-3 mol / l) pH about 12 (experimental example 3: lithium concentration of about 8.5 × 10 ^-3 mol / liter hydroxide), pH about 13 (experiment 4: lithium hydroxide concentration of about 2.1 × 10 ^{- 1} mol / liter) and pH of about 13.5 (Experimental Example 5: Lithium hydroxide concentration of about 3.5 × 10 ⁻¹ mol / liter). About other points, it carried out similarly to Experimental example 1 (refer FIG. 1), and prepared the paste-form positive electrode active material composition (b)-(e).

[Experimental Example 6: Preparation of positive electrode active material composition (f)]
In Experimental Example 6, lithium hydroxide was not used for preparing the positive electrode active material composition. That is, as shown in FIG. 2, electrode constituent materials (positive electrode active material, acetylene black, PTFE and CMC) were added to ion exchange water (pH about 7) and mixed. In other respects, a paste-like positive electrode active material composition (f) was prepared in the same manner as in Experimental Example 1.

  The positive electrode active material compositions (a) to (f) prepared as described above were allowed to stand at room temperature (about 25 ° C.), and the relationship between the standing time after preparation and the pH of the composition was examined. The result is shown in FIG. In FIG. 3, the plot indicated by the symbol “♦” corresponds to the composition (a). The plot indicated by ■ is for the composition (b), the plot indicated by the symbol “▲” is for the composition (c), the plot indicated by the symbol “x” is for the composition (d), and the symbol “*” The plot indicated by “” corresponds to the composition (e), and the plot indicated by the symbol “●” corresponds to the composition (f). Note that the time point of “0 Hr” on the horizontal axis in FIG. 3 is about 30 minutes after the positive electrode active material is added to the lithium solution (water in Experimental Example 6) (after the positive electrode active material and water coexist). Corresponds to the elapsed time. In Experimental Examples 1 to 3 and Experimental Example 6, the pH of the lithium solution used (water in Experimental Example 6) and the pH of the compositions (a) to (c) and (f) at the time of 0 Hr shown in FIG. This is considered to be because the pH of the composition increased between the coexistence of the positive electrode active material and water and the start of pH measurement.

  As shown in FIG. 3, the pHs of the compositions (a) to (d) of Experimental Examples 1 to 4 and the composition (f) of Experimental Example 6 are both increased to about pH 13.1 over time. . Such an increase in pH is related to the elution of lithium from the positive electrode active material (lithium ions are supplied from the positive electrode active material). In Experimental Examples 1 to 4, by using a lithium ion source (here, lithium hydroxide) that is different from the positive electrode active material, water (lithium solution containing lithium ions) prepared in advance to be alkaline and the positive electrode active material are mixed. Thus, compositions (a) to (d) are prepared. Therefore, as compared with the composition (f) of Experimental Example 6 that does not include such a lithium ion source (lithium salt), lithium that is eluted (irreversibly lost) from the positive electrode active material until the pH of the composition is stabilized. The amount is considered to be reduced. On the other hand, the composition (e) of Experimental Example 5 prepared using a lithium solution prepared at a pH higher than the above stable pH (here, pH of about 13.1) shows little change in pH over time. The liquid stability (pH) of the material was stable over time. This suggests that the elution of lithium from the positive electrode active material is well suppressed in the composition (e) of Experimental Example 5.

<Example 2: Production of positive electrode for lithium ion secondary battery>
Using the positive electrode active material compositions (a) to (f) prepared in Example 1, a positive electrode for a lithium ion secondary battery was produced. In this example, a composition that was allowed to stand for about 24 hours after preparation (that is, a composition that had passed about 24.5 hours in the state where the positive electrode active material and the aqueous solvent coexisted) was used.
The positive electrode was produced as follows. That is, each composition (after a predetermined time) obtained in Example 1 was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of about 20 μm and dried. The coating amount of the composition was adjusted so that the mass after drying was about 7.5 mg / cm ² per side. Then, it pressed so that the whole thickness might be set to about 75 micrometers. In this way, a positive electrode sheet having a positive electrode active material layer formed from the compositions (a) to (f) on both surfaces of the positive electrode current collector was produced.

<Example 3: Production and evaluation of lithium ion secondary battery>
A lithium ion secondary battery was produced using each positive electrode sheet obtained in Example 2.
That is, ion-exchanged water, artificial graphite (average particle size of about 10 μm) as a negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as a binder are mixed to produce a paste-like negative electrode active material. A substance composition was prepared. This paste contains graphite: SBR: CMC in a mass ratio of approximately 97: 2: 1. The negative electrode active material composition was applied to both sides of a copper foil (negative electrode current collector) having a thickness of about 14 μm and dried. The coating amount of the composition was adjusted so that the mass after drying was about 5 mg / cm ² per side. Then, it pressed so that the whole thickness might be set to about 80 micrometers. Thus, the negative electrode sheet | seat provided with a negative electrode active material layer on both surfaces of a negative electrode collector was produced.

A porous polyethylene sheet having a thickness of about 25 μm was used as the separator. The positive electrode sheet and the negative electrode sheet were stacked so as to face each other through this separator sheet, and this was wound to produce a wound electrode body. The obtained electrode body was accommodated in an aluminum cylindrical container together with a non-aqueous electrolyte solution. As the electrolytic solution, a 1: 3 (volume ratio) mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) containing LiPF ₆ at a concentration of about 1 mol / liter was used. Thus, the lithium ion secondary battery provided with the positive electrode produced using each composition (a)-(f) which concerns on Experimental example 1-6 was obtained.

  The initial capacities of these lithium ion secondary batteries were measured, and the initial capacity density of the positive electrode active material constituting each battery was evaluated. That is, as charge / discharge of the first cycle, constant voltage-constant voltage charge at a current density of 1/5 C was performed for a total of 6 hours with an upper limit voltage of 4.1 V, and then discharged at 1/5 C up to 3 V. Note that 1C in these batteries was 10A. In the second and third cycles, 1 C constant current-constant voltage charging was performed at 4.1 V for a total of 2.5 hours, and then discharged to 1 V at 1 C. In the fourth cycle, 1 C constant current-constant voltage charging was performed at 4.1 V for a total of 2.5 hours, and then discharged to 1 V at 1/5 C. The discharge capacity at the fourth cycle was defined as the initial battery capacity (mAh). This value was divided by the mass (g) of the positive electrode active material used for the production of each battery, and the initial battery capacity (initial capacity density) of the positive electrode active material was determined. The results are shown in FIG. 4 as the relationship between the lithium solution (water in the composition (f)) used for the preparation of each composition and the capacity density of the positive electrode active material in the secondary battery produced using the composition. Show. Reference numerals (a) to (f) attached to the respective plots in FIG. 4 indicate names of the corresponding positive electrode active material compositions.

  As can be seen from FIG. 4, the lithium ion secondary battery manufactured using the compositions (a) to (e) according to Experimental Examples 1 to 5 was manufactured using the composition (f) according to Experimental Example 6. In comparison with the above, the capacity density of the positive electrode active material was improved. This indicates that in the compositions (a) to (e) prepared using a lithium ion source (lithium hydroxide), elution of lithium from the positive electrode active material is suppressed as compared with the composition (f). Suggests that. Particularly good results were obtained in Experimental Examples 3 to 5 (compositions (c) to (e)) in which the pH of the lithium solution used for preparing the composition was 12 or more.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

It is explanatory drawing which shows the outline of the positive electrode active material composition preparation method which concerns on Experimental Examples 1-5. It is explanatory drawing which shows the outline of the positive electrode active material composition preparation method concerning Experimental example 6. FIG. It is a characteristic view which shows the relationship between the elapsed time after preparation, and pH of a positive electrode active material composition. It is a characteristic view which shows the relationship between the manufacturing method of a secondary battery, and the capacity density of a positive electrode active material.

Claims (5)

The lithium solution containing lithium salt supplies lithium ions in an aqueous solvent and the aqueous solvent, the positive electrode active material composition by mixing a positive electrode active material of a different material than the lithium salt A cathode active material containing lithium Preparing a product;
Adhering the composition to a positive electrode current collector. A method for producing a lithium ion secondary battery.   The method according to claim 1, wherein a lithium salt that shifts the pH of the aqueous solvent to the alkali side is used as the lithium salt.   The method according to claim 1, wherein lithium hydroxide is used as the lithium salt. The method according to any one of claims 1 to 3 , wherein the positive electrode active material is mixed with the lithium solution having a pH of 10 or more. The lithium ion secondary battery manufactured by the method as described in any one of Claim 1 to 4 .

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