JPWO2006123531A1 - Method for producing positive electrode using proton-containing nickel-based transition metal oxide - Google Patents

Abstract

The present invention provides a positive electrode for a non-aqueous electrolyte secondary battery using a proton-containing nickel-based transition metal oxide, which can obtain extremely good high rate discharge characteristics, and a proton-containing nickel-based battery An object of the present invention is to provide a nonaqueous electrolyte secondary battery having excellent self-discharge characteristics by using a transition metal oxide having a large BET specific surface area as a positive electrode active material. The present invention relates to a method for producing a positive electrode using a proton-containing nickel-based transition metal oxide as a positive electrode active material, wherein the chemical formula of the proton-containing nickel-based transition metal oxide is HxLiyNi1-aMaO2 (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 0.3 ≦ x + y ≦ 1.92, 0 <a ≦ 0.5, M is Co, Ti, V, Cr, Mn, Fe, Al, Cu and Zn At least one selected from the group consisting of: In addition, the positive electrode active material has the chemical formula HxLiyNi1-aMaO2 (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M is Co, Ti, V, Cr, Mn, Fe , At least one selected from the group consisting of Al, Cu and Zn), characterized in that a proton-containing nickel-based transition metal oxide having a BET specific surface area of 6 m 2 / g or more is used. .

Description

  The present invention relates to a method for producing a positive electrode for a non-aqueous electrolyte secondary battery using a proton-containing nickel-based transition metal oxide.

  A transition metal oxide such as lithium cobaltate, lithium manganate, or lithium nickelate is used as the positive electrode active material provided in the positive electrode of the nonaqueous electrolyte secondary battery. Among these, those in which the metal in the transition metal oxide is mainly nickel are generally highly expected because they generally exhibit a high discharge capacity. Hereinafter, this is referred to as “nickel-based transition metal oxide”.

A general nickel-based transition metal oxide is manufactured through a heat treatment step. For example, lithium nickelate (LiNiO ₂ ) includes Ni (NO ₃ ) ₂ , Ni (OH) ₂ , NiCO _3, or NiO as a nickel source, and LiOH, LiNO ₃ , Li ₂ CO ₃ , or the like as a lithium source. It is manufactured by being mixed with Li ₂ O or the like and heat-treated at about 600 to 900 ° C. in an oxygen stream.

  However, in the lithium nickelate manufactured through the heat treatment process, nickel and lithium ions are easily substituted to form an asymmetric structure, which causes a problem that the discharge capacity is reduced.

Therefore, it has been attempted to produce a nickel-based transition metal oxide by another method. For example, Japanese Patent Application Laid-Open No. 09-219193, which is a Japanese patent publication, discloses a method of synthesizing lithium nickelate by reacting nickel oxyhydroxide with a lithium ion-containing solution. Further, Japanese Unexamined 6-349494 discloses a Japanese Patent Publication, generally by ion exchange _A x _B y MO _z (where, 0 ≦ x ≦ 2,0 ≦ y ≦ 2,1.5 ≦ z ≦ 3, M = Mn, Fe, Ni, Co, V, Cr, Sc, A and B are elements composed of H, Li, Na, K, Cs, Ca, Mg, Rb and mixtures thereof ) Is disclosed.

Japanese Patent Laid-Open No. 09-320588, which is a Japanese patent publication, includes a chemical formula H _x Li _y MO ₂ (0 ≦ x ≦ 2, 0 ≦ y ≦ 2, 1 <(x + y) ≦ 2, where M is Co, Ni A method for producing LiMO ₂ is disclosed in which a compound represented by 1 or 2 transition metals selected from among (2) is chemically oxidized in a solution containing lithium ions.

  In Japanese Patent Laid-Open Publication No. 2000-123836, which is a Japanese patent publication, an aqueous lithium hydroxide solution is passed through nickel oxyhydroxide containing 10 mol% of cobalt to perform an ion exchange reaction between protons and lithium ions. A method for producing a positive electrode active material is disclosed.

  In the above manufacturing method, since the positive electrode active material is manufactured in an aqueous solution, it does not go through a heat treatment step. Therefore, the nickel-based transition metal oxide produced by this production method is less likely to produce an asymmetric structure, and thus is superior to that produced through a heat treatment step. In addition, there is an advantage that manufacturing is easy.

(1) However, when the above-described “nickel-based transition metal oxide produced in an aqueous solution” is used as a positive electrode active material of a nonaqueous electrolyte secondary battery, good high rate discharge characteristics cannot be obtained. There was a problem. The cause has not been clarified. Since the production is carried out in an aqueous solution, protons are contained in the nickel-based transition metal oxide, and this is thought to affect the high rate discharge characteristics. Since “a nickel-based transition metal oxide produced in an aqueous solution” contains protons, it is hereinafter referred to as “a proton-containing nickel-based transition metal oxide”.

  Accordingly, the present invention aims to provide a positive electrode for a non-aqueous electrolyte secondary battery using a proton-containing nickel-based transition metal oxide, which can obtain extremely good high rate discharge characteristics. . Furthermore, it aims at providing the nonaqueous electrolyte secondary battery which shows a very favorable high rate discharge characteristic by using the positive electrode for a nonaqueous electrolyte secondary battery.

(2) Furthermore, conventionally, the BET specific surface area of the proton-containing nickel-based transition metal oxide has always been small. Specifically, the BET specific surface area was less than 6 m ² / g. For this reason, there has been an interest in the characteristics of the proton-containing nickel-based transition metal oxide having a BET specific surface area of 6 m ² / g or more. However, because it was not manufactured, its properties remained unknown.

  Accordingly, an object of the present invention is to provide a new production method for controlling the BET specific surface area of a proton-containing nickel-based transition metal oxide.

(3) The present invention is a proton-containing nickel-based transition metal oxide having a large BET specific surface area that has not been produced conventionally (the chemical formula is represented by H _x Li _y Ni _1-a M _a O ₂₎ . Where 0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M is Co, Ti, V, Cr, Mn, Fe, Al, Cu and It is an object to provide a non-aqueous electrolyte secondary battery having excellent characteristics by using at least one selected from the group consisting of Zn as a positive electrode active material. Specifically, an object is to provide a non-aqueous electrolyte secondary battery having excellent self-discharge characteristics that cannot be predicted by those skilled in the art.

The present invention relates to a method for producing a positive electrode using a proton-containing nickel-based transition metal oxide as a positive electrode active material, wherein the chemical formula of the proton-containing nickel-based transition metal oxide is H _x Li _y Ni _1-a M _a O ₂ (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92, 0 <a ≦ 0.5, M is Co, Ti, V, Cr , Mn, Fe, Al, Cu, and Zn).

The present invention is characterized in that the proton-containing nickel-based transition metal oxide has a specific surface area of 6 m ² / g or more by the BET method. The invention of the present application is characterized in that, in the method of manufacturing a nonaqueous electrolyte secondary battery provided with a positive electrode and a negative electrode, the method of manufacturing the positive electrode is the manufacturing method described above.

In the present invention, the chemical formula is H _x Li _y Ni _1-a M _a O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, where M is Co, Ti , V, Cr, Mn, Fe, Al, Cu, and a proton-containing nickel-based transition metal oxide represented by at least one selected from the group consisting of Zn, BET of the proton-containing nickel-based transition metal oxide The specific surface area according to the method is 6 m ² / g or more.

  The invention of the present application is a non-aqueous electrolyte secondary battery comprising the proton-containing nickel-based transition metal oxide.

The present invention is a method for producing a proton-containing nickel-based transition metal oxide, which has a chemical formula of Ni _1-a M _a (OH) ₂ (0 <a ≦ 0.5, M is Co, A first step of contacting a hydroxide represented by at least one selected from Ti, V, Cr, Mn, Fe, Al, Cu and Zn with a solution containing an oxidizing agent and lithium ions; A second step of passing a solution containing lithium ions through the product obtained in one step and drying the product.

A positive electrode active material as a starting material used in manufacturing the positive electrode includes a proton-containing nickel-based transition metal oxide having a specific value of x and y (the chemical formula is H _x Li _y Ni _1-a M _a O ₂ Here, 0 <a ≦ 0.5, and M is at least one selected from the group consisting of Co, Ti, V, Cr, Mn, Fe, Al, Cu, and Zn. In this case, it became clear that the positive electrode was extremely excellent in terms of high rate discharge characteristics.

That is, the present invention relates to a method for producing a positive electrode using a proton-containing nickel-based transition metal oxide as a positive electrode active material, wherein the chemical formula of the proton-containing nickel-based transition metal oxide is H _x Li _y Ni _{1. −a} M _a O ₂ (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92, 0 <a ≦ 0.5, M is Co, Ti, V , Cr, Mn, Fe, Al, Cu, and Zn).

_{H x Li y Ni 1-a} M a O 2 (0.3 ≦ x ≦ 0.92 is a chemical formula shown here, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92,0 < a ≦ 0.5, M is at least one selected from the group consisting of Co, Ti, V, Cr, Mn, Fe, Al, Cu, and Zn) is a chemical formula at the time of manufacturing the positive electrode.

That is, this is the composition at the time of preparation. In the process in which the proton-containing nickel-based transition metal oxide represented by this chemical formula is charged, lithium ions are desorbed from the proton-containing nickel-based transition metal oxide to cause electron transfer. For example, when movement of z occurs as the number of electrons along with the desorption of lithium ions, the chemical formula becomes H _x Li _yz Ni _1-a M _a O ₂ . At this time, the average valence of Ni and M changes from “4- (x + y)” to “4- (x + yz)”.

As shown in the above chemical formula, a proton-containing nickel-based transition metal oxide (H _x Li _y Ni _1-a M _a O ₂ ) in which the values of x and y are in the predetermined range is used as the positive electrode active material Thus, when the positive electrode is manufactured, the high rate discharge characteristic of the positive electrode is always excellent. Furthermore, the high rate discharge characteristics of the nonaqueous electrolyte secondary battery using the positive electrode are always excellent. The saliency of this effect is not anticipated by those skilled in the art. Specific evaluation results will be described in the first embodiment.

Furthermore, the present invention relates to a proton-containing nickel-based transition metal oxide having a chemical formula represented by H _x Li _y Ni _1-a M _a O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, and M is at least one selected from the group consisting of Co, Ti, V, Cr, Mn, Fe, Al, Cu and Zn), and has a specific surface area of 6 m ² / g or more.

As a result of analyzing the BET specific surface area of the conventional proton-containing nickel-based transition metal oxide, all the BET specific surface areas were small and less than 6 m ² / g. That is, conventionally, there has been no proton-containing nickel-based transition metal oxide having a BET specific surface area of 6 m ² / g or more.

  However, as described later, the present inventor controls the BET specific surface area by changing a process of the method for producing a proton-containing nickel-based transition metal oxide that has not been noticed by those skilled in the art. Made it possible.

  Furthermore, as a result of investigating the correlation between the BET specific surface area and the self-discharge characteristics of the proton-containing nickel-based transition metal oxide by the inventors of the present application, and having a specific BET specific surface area, It turned out that the effect different from the conventional knowledge is acquired.

  In addition, as is well known, the BET method is a Langmuir theory in which three members of Brunauer, Emmett, and Teller are monolayer adsorption theory (molecules can be stacked and adsorbed indefinitely, and there is interaction between adsorption layers. This is a method for obtaining the surface area based on the theory that the Langmuir equation is established for each layer and extended to a multimolecular layer. Specifically, molecules having a known size are adsorbed on the surface of the powder particles, and the surface area of the sample is determined from the adsorbed amount.

  Conventionally, lithium nickelate used in non-aqueous electrolyte secondary batteries has a problem that self-discharge characteristics deteriorate when the BET specific surface area is large (see Japanese Patent Publication Gazette as a reference patent document). No. 09-298062). However, it has been found that the proton-containing nickel-based transition metal oxide of the present application tends to have the opposite tendency, that is, the self-discharge characteristics tend to be good when the BET specific surface area is large. Furthermore, it has been found that the self-discharge is minimized when it has a specific BET specific surface area. Such a phenomenon is not anticipated by those skilled in the art.

Here, the manufacturing method of the new proton-containing nickel-based transition metal oxide is as follows.
In the production method of the present invention, the chemical formula is Ni _1-a M _a (OH) ₂ (0 <a ≦ 0.5, M is selected from Co, Ti, V, Cr, Mn, Fe, Al, Cu and Zn. A first step in which a hydroxide represented by at least one kind is brought into contact with a solution containing an oxidizing agent and lithium ions, and a solution containing lithium ions is passed through the product obtained by the first step. A second step of drying.

By this production method, a proton-containing nickel-based transition metal oxide having a BET specific surface area of 6 m ² / g or more could be obtained. The difference from the prior art is in the second step. That is, conventionally, the product obtained in the first step has been washed with deionized water. Washing with deionized water is common knowledge for those skilled in the art as a method for synthesizing inorganic compounds. Therefore, changing the process of washing with deionized water is not usually employed. However, the inventors of the present application decided not to wash with deionized water, but to pass a solution containing lithium ions and dry it as it was.

  As the “solution containing lithium ions” in the first step of the present invention, lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium oxide, lithium nitrate, lithium sulfate, lithium chloride, lithium oxalate, lithium acetate And a solution in which at least one selected from the group consisting of lithium citrate is dissolved in a solvent such as water can be used. A solution in which these lithium salts do not reach saturation may be used. However, a solution saturated with a lithium salt is preferred.

  The “oxidant” in the first step is at least one selected from the group consisting of oxygen, ozone, peroxodisulfate, hypochlorite, permanganate, dichromate, bromine, and chlorine. Can be. Further, not only a chemical oxidation method using an oxidizing agent but also an electrochemical method can be used. The number of moles of oxidizing agent is preferably present in excess of 1 mole of nickel hydroxide from the viewpoint of reaction rate.

  Moreover, water or an organic solvent can be used as a solvent of the “solution” used in the second step. The solution preferably contains only lithium ions (and protons) as cations. However, it is not necessary to be limited to this, for example, sodium ion, potassium ion, etc. may be contained. Regarding the lithium ion concentration, from the viewpoint of reaction rate, it is preferable that the number of moles of lithium ions is excessive with respect to the number of moles of metal contained in the hydroxide. Specifically, a saturated aqueous solution of lithium hydroxide or the like is preferable.

  In the second step, “to pass a solution containing lithium ions” means, for example, (i) when removing the oxidizing agent used in the first step from the product filtered after finishing the first step. (Ii) The product filtered after finishing the first step is dispersed again in the solution containing lithium ions, and then, for example, Stirring for about 0.5 hour and collecting the product by filtration again.

  In the second step, the collected product is dried as it is. That is, washing with deionized water is not performed after passing a solution containing lithium ions and before drying. Here, when passing the solution through the solution containing lithium ions in the second step, the same solution containing lithium ions as the solution used in the first step (however, the solution containing no oxidant) is used. It is preferable. This is because side reactions are unlikely to occur.

Through the second step as described above, a proton-containing nickel-based transition metal oxide having a BET specific surface area of 6 m ² / g or more is obtained. Conventionally, it is considered that the BET specific surface area was 6 m ² / g or less because it was washed with deionized water.

In the second step of this production method, the product is produced by a special technical feature that “the solution containing lithium ions is not passed and then washed with deionized water before drying”. In the proton-containing nickel-based transition metal oxide, a change to a special technical feature that “the BET specific surface area is 6 m ² / g or more” is inevitably brought about. Therefore, the invention of the manufacturing method of the present application and the resulting invention have corresponding special technical features.

  It has been found that the BET specific surface area can be adjusted by variously changing the reaction conditions in the second step. The relationship between these various reaction conditions and the BET specific surface area will be described later in the second embodiment.

By the method as described above, a proton-containing nickel-based transition metal oxide having a large specific surface area of BET specific surface area of 6 m ² / g or more was obtained.
Moreover, when the BET specific surface area is 6 m ² / g or more, it is always possible to obtain proton-containing lithium nickel oxide having a smaller self-discharge than before.

Further, when M of the transition metal oxide (H _x Li _y Ni _1-a M _a O ₂ ) is Co, the specific surface area by the BET method may be 14.5 to 16.5 m ² / g. More preferable. In this case, the self-discharge characteristic is minimized. Specific evaluation results will be described later in the second embodiment.

  When the values of x and y are 0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92, self-discharge characteristics are further improved. I know that. The reason is not clear. Specific evaluation results will be described later in the second embodiment. Therefore, a proton-containing nickel-based transition metal oxide in which the values of x and y satisfy the condition of 0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92 When the positive electrode is produced by using it, both the high rate discharge characteristic and the self-discharge characteristic are extremely excellent.

  This application includes a patent application filed with the Japan Patent Office on April 28, 2005 (Japanese Patent Application No. 2005-132069) and a patent application filed with the Japan Patent Office on January 19, 2006 (Japanese Patent Application No. 2006-010554), the contents of which are incorporated herein by reference.

Shows the distribution of the values of x and y in the proton-containing nickel-based transition metal oxide prepared in this application _{(H x Li y Ni 0.76 M} 0.24 O 2). The evaluation result of the high rate discharge characteristic of the proton containing type nickel-type transition metal oxide whose x is about 0.7 is shown. The evaluation result of the high rate discharge characteristic of the proton content type nickel system transition metal oxide whose y is about 0.8 is shown.

  The present invention will be specifically described in the following embodiments. However, the technical scope of the present invention is not construed as being limited by the following embodiments.

[Embodiment 1]
(1) Proton-containing lithium nickelate was produced. The manufacturing method includes the following first step and second step.

(First Step) 2.0 g of hydroxide (average particle size: 10 μm) represented by the chemical formula Ni _0.76 Co _0.24 (OH) ₂ was dispersed in 50 ml of an aqueous solution of lithium salt. To this dispersed aqueous solution was added 12% hypochlorous acid (NaClO) functioning as an oxidizing agent. The kind and concentration of the reaction solution during the reaction in the first step, the addition amount of the oxidizing agent, the reaction temperature, and the reaction time are as shown in the column of the first step in Table 1, respectively. During the reaction, stirring was continued.

(Second step) After the reaction in the first step was completed, filtration was performed. The product obtained by filtration was dispersed in 50 ml of a lithium hydroxide aqueous solution adjusted to a predetermined concentration, and further stirred for 0.5 hour. This was filtered again, and after the solution was removed from the product, it was directly dried at 65 ° C. for 12 hours. The predetermined concentration of the lithium hydroxide concentration in the second step is as shown in the column of the second step in Table 1.

(2) Composition analysis of various produced proton-containing nickel-based transition metal oxides was performed.
The value of y in the chemical formula was calculated from the molar ratio of Li / (Ni + M) after quantification of Li, Ni and M by inductively coupled plasma (ICP) analysis. The value of x in the chemical formula was calculated from the molar ratio of H / (Ni + M) after quantification of H, Ni and M by Rutherford backscattering analysis (RBS) -hydrogen forward scattering analysis (HFS).

  The results of these composition analyzes are shown in the column of the composition formula of the produced proton-containing nickel-based transition metal oxide in Table 1. In addition, the values of x and y in the chemical formula of the produced proton-containing nickel-based transition metal oxide are taken as the X-axis and Y-axis of the graph, respectively, and proton-containing nickel-based transition metal oxides serving as examples and comparative examples Is shown in FIG. In this method, a proton-containing nickel-based transition metal oxide having a y value greater than 1 in the chemical formula could not be obtained. This is probably because an oxidation reaction and a reaction for exchanging protons for lithium ions (ion exchange reaction) occur in parallel, so that a larger amount of ion exchange than the oxidation reaction cannot be performed. In addition, materials having an x value greater than 1 are only those that are not sufficiently oxidized from nickel hydroxide.

(3) A positive electrode was manufactured using the manufactured proton-containing nickel-based transition metal oxide as a positive electrode active material.
The positive electrode is manufactured by the following method. Proton-containing nickel-based transition metal oxide (89% by mass), acetylene black (4% by mass), and polyvinylidene fluoride (7% by mass) produced by the above-described production method are N-methyl-2-pyrrolidone ( Hereinafter, it is abbreviated as NMP.) By mixing in, a positive electrode paste was manufactured. This positive electrode paste was applied onto an aluminum foil having a thickness of 20 μm. Thereafter, NMP was removed by drying under reduced pressure at 70 ° C. The coating weight after removing NMP was 1.00 g / 100 cm ² . The obtained positive electrode was pressed with a roller and then cut into a size of 30 mmW × 40 mmL × 50 μmT by a slitter to produce a plate-shaped positive electrode.

(4) The high rate discharge characteristics of the positive electrode were evaluated.
The high rate discharge characteristics of the positive electrodes of Examples and Comparative Examples shown in Table 1 were evaluated. Evaluation is based on the following method.
As working electrodes, positive electrodes of Examples and Comparative Examples shown in Table 1 were used. A metal lithium plate was used as a reference electrode and a counter electrode. As an electrolytic solution, a solution in which LiClO ₄ is dissolved in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 1 so that the concentration becomes 1 mol / dm ³ is used. It was. Thus, a tripolar glass cell was produced.

The electrochemical potential behavior is evaluated by the following method. In 25 ° C., after which the current density is charged to 4.2V (vs.Li/Li ⁺⁾ so that 0.25 mA / cm ² relative to the plate-like positive electrode, 1.5V (vs.Li/Li ⁺ ) Was discharged at a low rate (current density: 0.25 mA / cm ² ). Then, after charging again as described above, high-rate discharge (current density: 5.0 mA / cm ² ) was performed up to 1.5 V (vs. Li / Li ⁺ ).

  The discharge capacity at the time of low rate discharge, the discharge capacity at the time of high rate discharge, and the ratio thereof are shown in Table 1 as evaluation results. FIG. 2 shows the evaluation results of the high rate discharge characteristics of the proton-containing nickel-based transition metal oxide having x of about 0.7. FIG. 3 shows the evaluation results of the high rate discharge characteristics of the proton-containing nickel-based transition metal oxide in which y is about 0.8.

From Table 1, the chemical formula is H _x Li _y Ni _0.76 Co _0.24 O ₂ (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92). When a positive electrode was produced using a certain proton-containing nickel-based transition metal oxide, it was revealed that the positive electrode exhibited a particularly good high rate discharge characteristic. That is, the high rate discharge characteristics of the positive electrodes A01 to A15 were superior to those of R01 to R14. If FIG.2 and FIG.3 is seen, the mode of remarkable effect will be easy to understand. Such a result is not anticipated by one skilled in the art. The mechanism by which such a particularly good high rate discharge characteristic is obtained has not been accurately grasped at present. This is probably because the proton-containing nickel-based transition metal oxide serving as the host layer has specific H and Li sites.

(5) The characteristics of the non-aqueous electrolyte secondary battery when the non-aqueous electrolyte secondary battery was manufactured using the positive electrode were evaluated.
Using the positive electrode shown in Table 1, a non-aqueous electrolyte secondary battery was manufactured. The manufacturing method is as follows.
As the positive electrode, those shown in the above-mentioned examples and comparative examples were used.

  The manufacturing method of the negative electrode is as follows. Scaly graphite was used as the negative electrode active material. A negative electrode paste was produced by mixing flaky graphite (80% by mass) having an average particle size of 10 μm and polyvinylidene fluoride (20% by mass) with NMP. This negative electrode paste was applied onto a copper foil having a thickness of 15 μm. The NMP was removed by drying the copper foil coated with the negative electrode paste at 150 ° C. This was compression molded with a roll press and cut into a size of 30 mmW × 40 mmL × 35 μmT with a slitter to produce a plate-like negative electrode.

The obtained positive electrode and negative electrode were superposed through a polyethylene separator (a communicating porous body having a thickness of 20 μm and a porosity of 40%), whereby a power generation element was formed. This power generation element was inserted into a container having a height of 70 mm, a width of 34 mm, and a thickness of 1 mm. A nonaqueous electrolyte secondary battery was manufactured by injecting a nonaqueous electrolyte into the container. In this case, an electrolyte solution as a nonaqueous electrolyte is prepared by dissolving 1 mol / dm ³ of LiPF ₆ in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 1. It was. The nominal capacity (1C) of the manufactured nonaqueous electrolyte secondary battery is 12 mAh.

  The high rate discharge characteristics of the nonaqueous electrolyte secondary battery were evaluated. The evaluation method is as follows. At 25 ° C., the battery was charged to 4.2 V at a current of 2.4 mA, and then discharged to 2.75 V at 2.8 mA corresponding to low rate discharge. Thereafter, the battery was charged again to 4.2 V at a current of 2.4 mA, and then discharged to 2.75 V at 36 mA corresponding to high rate discharge. The discharge capacity is also shown in Table 1.

As a result, the chemical formula is H _x Li _y Ni _0.76 Co _0.24 O ₂ (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y ≦ 1.92). It has been clarified that when a positive electrode is produced using a proton-containing nickel-based transition metal oxide, the non-aqueous electrolyte secondary battery exhibits a particularly good high rate discharge characteristic. That is, the high rate discharge characteristics of the nonaqueous electrolyte secondary batteries of A01 to A15 were superior to those of R01 to R14. Such a result is not anticipated by one skilled in the art.

(6) It should be noted that the proton-containing nickel-based transition metal oxide represented by the chemical formula H _x Li _y Ni _1-a Co _a O ₂ (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1) , 1.3 ≦ x + y ≦ 1.92), if the value of a is 0 <a ≦ 0.5, the effect of the present invention is that the high-rate discharge characteristics that are not anticipated by those skilled in the art can be obtained. The inventor of the present application confirmed that

  Even in the case where nickel in the proton-containing nickel-based transition metal oxide is substituted with at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Al, Cu and Zn, Co As in the case of substitution, when x and y are in the predetermined range, the high-rate discharge characteristics of the positive electrode manufactured using the proton-containing nickel-based transition metal oxide are excellent. The inventor confirmed.

[Embodiment 2]
(1) A positive electrode active material was produced. The manufacturing method includes the following first step and second step.

(First Step) 2.0 g of hydroxide (average particle size: 10 μm) whose chemical formula is represented by Ni _1-a Co _a (OH) ₂ is dispersed in 50 ml of an aqueous lithium hydroxide solution adjusted to a predetermined concentration. It was done. To this dispersion was added 7.7 g of sodium peroxodisulfate (Na ₂ S ₂ O ₈ ) that functions as an oxidizing agent. Then, the reaction for 12 hours was performed at a predetermined temperature. During the reaction, stirring was continued. Here, the value of a of the hydroxide represented by Ni _1-a Co _a (OH) ₂ , the concentration of the lithium hydroxide aqueous solution, and the temperature during the reaction are as shown in Table 2 and Table 3, respectively. It is. Although Tables 2 and 3 are supposed to be arranged vertically as one table originally, they are described in two for the sake of space.

(Second step) After the reaction in the first step was completed, filtration was performed. The product obtained by filtration (the product obtained through the first step) was passed through 50 ml of a lithium hydroxide aqueous solution having a predetermined concentration shown in Tables 2 and 3. Thereafter, drying was performed at 80 ° C. for 1 hour.

  Here, “0 (50 ° C.)” shown in the column of the second step in Table 2 and Table 3 means that the solution was passed with deionized water at 50 degrees Celsius. The temperature of the lithium hydroxide aqueous solution in the second step when not specified is 25 ° C.

(2) The BET specific surface area of the product produced through the second step was measured. For measurement of the specific surface area by the BET method, Shimadzu Corporation micromeritics, Gemini 2375, V4.01 were used.
The results are as shown in Table 2 and Table 3 together. The BET specific surface area of the proton-containing nickel-based transition metal oxide (H _x Li _y Ni _1-a M _a O ₂ ) produced by carrying out the production method of the present application was always 6 m ² / g or more. On the other hand, as the concentration of the lithium hydroxide solution used in the second step is reduced, the BET specific surface area of the proton-containing nickel-based transition metal oxide (H _x Li _y Ni _1-a M _a O ₂ ) is: It has become smaller. As in the prior art, when the liquid flow in the second step was performed with deionized water, the BET specific surface area was always less than 6 m ² / g.

(3) The composition analysis of the proton-containing nickel-based transition metal oxide was performed.
The method of composition analysis is the same as in the first embodiment. The results are as shown in the product columns in Tables 2 and 3.

(4) The self-discharge characteristics of the nonaqueous electrolyte secondary battery produced using these positive electrodes were evaluated.
Evaluation is based on the following method. About the manufactured nonaqueous electrolyte secondary battery, charge and discharge were repeated 10 cycles. The discharge capacity discharged at the 10th cycle at this time was defined as “P [mAh]”. Thereafter, the nonaqueous electrolyte secondary battery was charged and left at 25 ° C. for 30 days. Then, “discharge capacity Q [mAh]”, which was the capacity that could be subsequently discharged, was determined. The ratio of Q to P is the discharge capacity retention rate. Therefore, the higher the discharge capacity retention rate, the better the self-discharge characteristics. The results of discharge capacity retention are shown in Tables 2 and 3.

  Usually, the larger the BET specific surface area, the worse the self-discharge characteristics. However, as shown in Tables 2 and 3, it was found that in the proton-containing nickel-based transition metal oxide, when the BET specific surface area is large, the self-discharge tends to be small. Such a phenomenon is not anticipated by those skilled in the art.

In this production and evaluation, only a proton-containing nickel-based transition metal oxide having a BET specific surface area of 24 m ² / g or less was obtained. When the BET specific surface area is 6 m ² / g or more and 24 m ² / g or less, it is certain that the discharge capacity retention rate is good. Preferably, the self-discharge characteristics of the proton-containing nickel-based transition metal oxide having a BET specific surface area of 14.5 m ² / g or more and 16.5 m ² / g or less are particularly good.

(5) The chemical formula _{H x Li y Ni 1-a} M a O proton content type is represented by ₂ nickel based transition metal oxide (0 <x ≦ 1,0 <y ≦ 1,1 ≦ x + y ≦ 2 ), When M is not cobalt but is one or more selected from the group consisting of Ti, V, Cr, Mn, Fe, Al, Cu and Zn, the BET specific surface area is 6 m ² / The inventor of the present application confirmed that the self-discharge characteristic is excellent when it is g or more.

[Other embodiments]
(1) As the negative electrode active material, scaly graphite, amorphous carbon, oxide, or nitride may be used. These may be used alone or in admixture of two or more.

(2) As a binder used when producing a positive electrode or a negative electrode, polytetrafluoroethylene, ethylene-propylene-diene terpolymer, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate , Polyethylene, nitrocellulose, polyvinylidene fluoride, polyethylene, polypropylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, styrene-butadiene rubber (SBR), or carboxymethylcellulose (CMC) ) Etc. can be used.

(3) As a solvent used when mixing the binder, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN -Dimethylaminopropylamine, ethylene oxide, tetrahydrofuran or the like can be used.

(4) As the current collector of the electrode, iron, copper, stainless steel, nickel, or aluminum can be used. The form may be a sheet form, a foam form, a mesh form, a porous form, or an expanded lattice form. Furthermore, a current collector having a hole in an arbitrary shape can also be used.

(5) As the electrolyte, an electrolytic solution can be used. Examples of the organic solvent constituting the electrolyte include ethylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, and 2-methyl. Tetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate and the like can be used. These may be used alone or in admixture of two or more. Further, a carbonate compound such as vinylene carbonate or butylene carbonate, a benzene compound such as biphenyl or cyclohexylbenzene, or a sulfur compound such as propane sultone can be mixed in an organic solvent. As _the supporting salt constituting the _{electrolyte, LiPF 6, LiClO 4, LiBF} 4, LiAsF 6, LiPF (CF 3) 5, LiPF 2 (CF 3) 4, LiPF 3 (CF 3) 3, LiPF 4 ( CF ₃ ) ₂ , LiPF ₅ (CF ₃ ), LiPF ₃ (C ₂ F ₅ ) ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF _{3) 2, LiN (COCF 2} CF 3) 2, etc. _LiC 4 BO ₈ may be used. These may be used alone or in combination of two or more.

(6) A combination of an electrolytic solution and a solid electrolyte may be used as the electrolyte. As the solid electrolyte at this time, a crystalline inorganic solid electrolyte or an amorphous inorganic solid electrolyte can be used. The former includes LiI, Li ₃ N, Li _{1 + x} M _x Ti _2-x (PO ₄ ) ₃ (M = Al, Sc, Y, La),
A thio LISICON represented by Li _0.5-3x R _{0.5 + x} TiO ₃ (R = La, Pr, Nd, Sm) or Li _4-x Ge _1-x P _x S ₄ can be used. The latter includes LiI—Li ₂ O—B ₂ O ₅ system, Li ₂ O—SiO ₂ system,
A LiI—Li ₂ S—B ₂ S ₃ system, a LiI—Li ₂ S—SiS ₂ system, a Li ₂ S—SiS ₂ —Li ₃ PO ₄ system, or the like may be used.

(7) As the separator, a polyolefin microporous film represented by polyethylene, nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, or the like can be used.

(8) The shape of the nonaqueous electrolyte secondary battery is not particularly limited. The shape may be a square, an ellipse, a coin, a button, a sheet, or the like.

Claims (7)

In a method for producing a positive electrode using a proton-containing nickel-based transition metal oxide as a positive electrode active material,
The chemical formula of the proton-containing nickel-based transition metal oxide is H _x Li _y Ni _1-a M _a O ₂ (0.3 ≦ x ≦ 0.92, 0.38 ≦ y ≦ 1, 1.3 ≦ x + y .Ltoreq.1.92, 0 <a.ltoreq.0.5, and M is at least one selected from the group consisting of Co, Ti.V, Cr, Mn, Fe, Al, Cu and Zn). . In the method of manufacturing the positive electrode according to claim 1,
The proton-containing nickel-based transition metal oxide has a specific surface area of 6 m ² / g or more according to the BET method. In a method for producing a nonaqueous electrolyte secondary battery including a positive electrode and a negative electrode,
The method for manufacturing the positive electrode is the manufacturing method according to claim 1. In a method for producing a nonaqueous electrolyte secondary battery including a positive electrode and a negative electrode,
The method for producing the positive electrode is the production method according to claim 2. The chemical formula is H _x Li _y Ni _1-a M _a O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M is Co, Ti, V, Cr , Mn, Fe, Al, Cu, and a proton-containing nickel-based transition metal oxide represented by at least one selected from the group consisting of Zn and Zn,
The proton-containing nickel-based transition metal oxide has a specific surface area of 6 m ² / g or more according to the BET method.   A nonaqueous electrolyte secondary battery comprising the proton-containing nickel-based transition metal oxide according to claim 5. A method for producing a proton-containing nickel-based transition metal oxide,
The manufacturing method is
The chemical formula is Ni _1-a M _a (OH) ₂ (0 <a ≦ 0.5, M is at least one selected from the group consisting of Co, Ti, V, Cr, Mn, Fe, Al, Cu, and Zn). A first step of contacting the represented hydroxide with a solution comprising an oxidant and lithium ions; and
A second step of allowing the product obtained in the first step to pass through a solution containing lithium ions and drying the solution.

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