JP5003030B2 - Cathode active material for nonaqueous electrolyte secondary battery, method for producing the same, and nonaqueous electrolyte secondary battery including the same - Google Patents

Description

  The present invention relates to a proton-containing transition metal oxide as a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery including the proton-containing transition metal oxide.

  In recent years, small and lightweight lithium ion secondary batteries have been widely used as power sources for electronic devices such as mobile phones and digital cameras. Such multi-functionalization of electronic devices has advanced remarkably, and lithium ion secondary batteries such as lithium cobaltate / carbon material system, lithium manganate / carbon material system and lithium nickelate / carbon material system which are currently used are being used. Alternative high energy density batteries are expected.

Among them, lithium nickelate is a layered compound having the same crystal structure as lithium cobaltate, and lithium is inserted between NiO ₆ octahedron layers sharing an edge. Lithium nickelate has the highest discharge capacity among the positive electrode active materials, and is highly expected as a high capacity active material.

The method for producing lithium nickelate uses Ni (NO ₃ ) ₂ , Ni (OH) ₂ , NiCO _3, or NiO as the nickel source, and LiOH, LiNO ₃ , Li ₂ CO ₃ , Li ₂ O, or the like as the lithium source. However, it is common to perform heat treatment at about 600 to 900 ° C. in an oxygen stream after mixing the two, but a manufacturing method that is not a solid-phase firing method is also being studied.

Patent Document 1 discloses a method for producing lithium nickelate in which nickel oxyhydroxide and a solution containing lithium ions are reacted as one of low-temperature synthesis methods. Patent Document 2 discloses a chemical formula H _x Li _y MO ₂ (where 0 ≦ x ≦ 2, 0 ≦ y ≦ 2, 1 ≦ x + y ≦ 2, M is one selected from Co and Ni, or A method for producing LiMO ₂ is disclosed in which a compound represented by two kinds of transition metals is chemically oxidized in a solution containing lithium ions. However, none of the positive electrode active materials described in Patent Document 1 and Patent Document 2 contains Ni, Co, and Mn at the same time.

Patent Document 3 discloses a general formula A _x B _y MO _z (where 0 ≦ x ≦ 2, 0 ≦ y ≦ 2, 1.5 ≦ z ≦ 3, M = Mn, Fe, Ni, Co, V, Cr or Sc, A and B are synthesis methods of active materials represented by H, Li, Na, K, Cs, Ca, Mg and Rb, and mixtures thereof by a low temperature ion exchange method Is disclosed. However, LiMnO ₂ and LiMn ₂ O ₄ are only exemplified as the obtained positive electrode active material.

Furthermore, Patent Document 4 discloses a method for producing a general formula H _x A _1-x MO ₂ (where x = 0.99 to 0, A is a group 1a alkali metal, M = Co, Ni). However, only H _x Li _1-x CoO ₂ and H _x Li _1-x NiO ₂ are described, and those containing Ni, Co, and Mn at the same time are not illustrated.

  In addition, there is an attempt to use nickel oxyhydroxide as a positive electrode active material of a non-aqueous secondary battery. Patent Document 5 discloses NiOOHLi, and Patent Document 6 discloses oxywater containing 20 to 75 mol% of cobalt. Nickel oxide is disclosed. Furthermore, Patent Document 7 discloses a method for producing cobalt-containing lithium nickelate, in which an aqueous lithium hydroxide solution is passed through nickel oxyhydroxide containing 10 mol% of cobalt, and an ion exchange reaction between hydrogen ions and lithium ions is performed. Is disclosed. However, in any case, a positive electrode active material containing Ni, Co, and Mn simultaneously is not exemplified.

  Note that Patent Document 6 and Patent Document 7 do not clarify the content ratio of hydrogen and lithium in these positive electrode active materials.

Further, Patent Documents 8 and 9 disclose composite oxides containing Li, Ni, Co, and Mn as positive electrode active materials for non-aqueous secondary batteries. These composite oxides contain protons. Not included.
JP 09-219193 A Japanese Patent Application Laid-Open No. 09-320588 Japanese Patent Laid-Open No. 06-349494 Japanese Patent No. 3263882 JP 2000-323174 A Japanese Unexamined Patent Publication No. 63-19760 JP 2000-123836 A Japanese Patent Laid-Open No. 2005-1000094 JP 2000-133262 A

  In lithium nickelate containing protons as a positive electrode active material of a non-aqueous secondary battery, if the amount of nickel per mole ratio of the composition formula is 0.5 or less, the amount of charge is limited by the valence of nickel. There was a problem that it was.

Further, in LiNi _1/3 Mn _1/3 Co _1/3 O ₂ which is a composite oxide not containing protons as a positive electrode active material of a non-aqueous secondary battery, three-component composite water containing Ni, Mn and Co is used. The manufacturing process is complicated because an oxide is produced, and this is mixed with a lithium compound and then fired.

  Accordingly, an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that has a simple manufacturing process, is industrially advantageous, and has a large discharge capacity.

The invention according to claim 1, the positive electrode active material for a nonaqueous electrolyte secondary battery, the chemical formula _{H x Li y Co 1-a} -b-c Ni a Mn b M c O 2 ( however, M is Al, Mg, Zn And a metal element selected from Cr , 0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ 1/10, 1/3 ≦ a + b ≦ 2/3).

According to a second aspect of the invention, in the manufacturing method of the nonaqueous electrolyte cathode active material for electrolyte secondary battery, the chemical formula _{Co 1-a-b-c} Ni a Mn b M c (OH) 2 ( However, M is Al, Mg , Zn, and Cr , 0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ 1/10, 1/3 ≦ a + b ≦ 2/3) a solution containing a transition metal hydroxide, a lithium ion, and an oxidant are brought into contact with each other. characterized Rukoto was passed through a solution containing lithium ions.

  According to a third aspect of the present invention, in the nonaqueous electrolyte secondary battery, the positive electrode active material for a nonaqueous electrolyte secondary battery according to the first aspect is provided.

In the present invention, the non-aqueous electrolyte formula the positive electrode active material for a secondary battery _{H x Li y Co 1-a} -b-c Ni a Mn b M c O 2 ( however, M is Al, Mg, Zn, and, Cr A metal element selected from : 0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ 1 / 10, 1/3 ≦ a + b ≦ 2/3), a nonaqueous electrolyte secondary battery having a large discharge capacity per unit mass can be obtained. .

In the positive electrode active material of the present invention, even if Ni is 0.5 or less, the combined amount of Ni and Mn is between 1/3 and 2/3 per mole ratio of the composition formula. , valence change from trivalent Ni to tetravalent is performed smoothly in the charging process, the lithium nickel dioxide containing no Mn, up to 3.7 valent about valence of Ni is trivalent in charge process However, it is considered that the problem that the amount of charged electricity cannot be sufficiently obtained is eliminated.

In the present invention, the positive electrode active material for a non-aqueous electrolyte secondary battery has the chemical formula H _x Li _y Co _1-a-b-c Ni _a Mn _{b McO 2} (where M is Al, Mg, Zn, and , Metal element selected from Cr , 0 <x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ The proton-containing transition metal oxide represented by 1/10, 1/3 ≦ a + b ≦ 2/3) is used. This proton-containing transition metal oxide has a chemical formula Co _1-ab-c Ni _a Mn _{b Mc} (OH) ₂ (where M is a metal element selected from Al, Mg, Zn, and Cr , 0 < x ≦ 1, 0 <y ≦ 1, 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ 1/10, 1/3 ≦ a + b after contacting the solution with an oxidizing agent containing a transition metal hydroxide and lithium ion represented by ≦ 2/3), manufactured in Ru is passed through the resulting product in a solution containing lithium ions method be able to. In addition, the present invention is characterized in that the proton-containing transition metal oxide is used as a positive electrode active material of a nonaqueous electrolyte secondary battery.

In the chemical formula _{H x Li y Co 1-a} -b-c Ni a Mn b M proton-containing transition metal oxide represented by c _{O 2} of the present invention and 0 <x ≦ 1. When x = 0, that is, when H is not contained in the transition metal oxide, there is a problem in that the high rate discharge characteristic is lowered as in the case of the conventional lithium nickelate. In addition, a material having a value of x greater than 1 is only a material that is not sufficiently oxidized from nickel hydroxide, and therefore a sufficient charge / discharge capacity as a positive electrode active material cannot be obtained.

  y represents the number of moles of Li that is occluded or released from the proton-containing transition metal oxide during charge / discharge of the battery. When y is 1 or more, the cycle performance deteriorates, and therefore it is necessary to satisfy y <1. .

The value of x + y before battery production can be expressed by the following formula (1).
x + y = 4- (average valence of Co, Ni and Mn) (1)

That is, the chemical formula _{H x Li y Co 1-a} -b-c Ni a Mn b M c O 2 of the present invention is a chemical formula at the time of producing the positive electrode active material. That is, this is the composition when the battery is charged. In the process in which the proton-containing transition metal oxide represented by this chemical formula is charged, lithium ions are desorbed from the proton-containing transition metal oxide, and electron transfer occurs. For example, the positive electrode active material with elimination of lithium ions, if z movement occurs as the number of electrons, the chemical formula _{H x Li y-z Co 1} -a-b-c Ni a Mn b M c O 2 It becomes. At this time, the average valences of Co, Ni, Mn, and M change from [4- (x + y)] to [4- (x + yz)].

  Since the positive electrode active material before being assembled into the battery is in a discharged state, it is in the range of 1 ≦ x + y ≦ 2. Li is released as the positive electrode active material is charged, and y is infinitely close to 0 when the positive electrode active material is fully charged. For example, in a positive electrode active material in a discharged state, when x = 0.1 and y = 0.9, since y is close to 0 in a fully charged state, x + y is close to 0.1. Therefore, in the proton-containing transition metal oxide of the present invention, the value of x + y varies in the range of 0 <x + y ≦ 2 depending on the charge / discharge state.

“Fully charged state” means that a non-aqueous electrolyte secondary battery using a proton-containing transition metal oxide as a positive electrode active material is charged to 4.3 V (vs. Li ^/ Li ⁺ ) at a constant current of 0.1 CmA. Further, it means a state in which a 4.3 V (vs. Li ^/ Li ⁺ ) constant voltage charge was performed for 5 hours.

Further, the substitution amount a (mol) of Ni is set to 1/6 ≦ a ≦ 1/3. When a is smaller than 1/6, sufficient charge / discharge capacity cannot be obtained. This is considered to be because Mn substituted for the purpose of controlling the valence of Ni was not sufficiently dissolved. Moreover, when a is larger than 1/3, sufficient charge / discharge capacity cannot be obtained. This is considered to be caused by the fact that the valence change of Ni is not smoothly performed as in the case of lithium nickelate.

The substitution amount b (mol) of Mn is set to 1/6 ≦ b ≦ 1/3. When b is smaller than 1/6, sufficient charge / discharge capacity cannot be obtained. This is considered to be caused by the fact that the valence change of Ni is not smoothly performed as in the case of lithium nickelate. Moreover, when b is larger than 1/3, sufficient charge / discharge capacity cannot be obtained. This is considered to be because Mn substituted for the purpose of controlling the valence of Ni was not sufficiently dissolved.

Therefore, (a + b) is 1/3 or more and 2/3 or less . In the positive electrode active material of the present invention, even when the substitution amount a of Ni is 1/6 ≦ a ≦ 1/3, the combined amount of Ni and Mn (a + b) is 1/3 or more per mole ratio of the composition formula 2/3 or less .

  The solution containing lithium ions used when producing a proton-containing transition metal oxide in the present invention may be a solution containing unsaturated lithium ions or a liquid phase dispersion containing a saturated or higher lithium compound. Good. The lithium ion source may be one type or a mixture of two or more types.

  The lithium ion source is at least one selected from lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium oxide, lithium nitrate, lithium sulfate, lithium chloride, lithium oxalate, lithium acetate, or lithium citrate. It is preferred to include seeds.

  As a solvent of the solution containing lithium ions, water is preferably used, but an organic solvent may be used. This solution does not necessarily need to contain only lithium ions (and protons) as cations, and may contain sodium ions, potassium ions, and the like, for example.

  The lithium ion concentration is preferably such that the number of moles of lithium ions is excessive with respect to the number of moles of nickel hydroxide in terms of reaction rate.

The oxidizing agent used in the production of the proton-containing transition metal oxide in the present invention is selected from oxygen, ozone, peroxodisulfate, hypochlorite, permanganate, dichromate, bromine, and chlorine. At least one of the above can be used. Further, not only a chemical oxidation method using an oxidizing agent but also an electrochemical method may be used. The amount of the oxidizing agent from the standpoint of reaction rate, is the chemical formula _{Co 1-a-b-c} Ni a Mn b M c (OH) molar excess relative to the transition metal hydroxide to 1 mole of the formula ₂ It is preferable.

The chemical formula _{Co 1-a-b-c} Ni a Mn b M c (OH) and the transition metal hydroxide represented by the _second oxidant, or the time of contacting the these with the lithium ion is not particularly limited 1 to 240 hours are preferable. The reaction rate can be increased by increasing the temperature of the solution. However, in order not to boil the solution, the temperature is preferably not higher than the boiling point of the solvent used, and is in the range of 25 to 80 ° C. Is more preferable in consideration of workability.

A product obtained by bringing a transition metal hydroxide represented by the chemical formula Co _1-a-b-c Ni _a Mn _b M _c (OH) ₂ into contact with a solution containing lithium ions and an oxidant is used as lithium. Pass through a solution containing ions. Here, “liquid passing” means that a solution containing a transition metal hydroxide represented by the chemical formula Co _1-a-b-c Ni _a Mn _{b Mc} (OH) ₂ , a lithium ion, and an oxidizing agent are brought into contact with each other. The solution containing lithium ions is gradually added to the product obtained and stirred, and then filtered, or the product and the solution containing lithium ions are mixed, stirred, filtered, etc. means.

The solution used in the step of passed through a solution containing lithium ions, a solution containing a chemical formula _{Co 1-a-b-c} Ni a Mn b M c (OH) transition metal hydroxide represented by ₂ and lithium ion The same solution containing lithium ions as that used in the step of contacting with the oxidizing agent can be used.

Formula _{Co 1-a-b-c} Ni a Mn b M c (OH) solution with a proton-containing transition metal oxide obtained by contacting an oxidizing agent containing a transition metal hydroxide and lithium ion represented by ₂ Since an object can electrochemically occlude and release alkali metals, a non-aqueous electrolyte secondary battery exhibiting excellent characteristics can be obtained by using an electrode including the alkali metal.

  In the nonaqueous electrolyte secondary battery of the present invention, the negative electrode active material is not particularly limited, and a carbon material such as graphite or amorphous carbon, an oxide, or a nitride can be used as the negative electrode active material. In these, since capacity | capacitance and charging / discharging cycling performance are excellent, it is preferable to use carbon materials and oxides, such as graphite and amorphous carbon.

  Binders used when producing positive and negative electrodes include ethylene-propylene-diene terpolymer, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, and polyvinylidene fluoride. Selected from polyethylene, polypropylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, styrene-butadiene rubber (SBR) or carboxymethylcellulose (CMC). Can be used.

  As the solvent used when mixing the binder, either a non-aqueous solvent or an aqueous solution can be used. As the non-aqueous solvent, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like can be used. On the other hand, a dispersing agent, a thickener, etc. can be added and used for aqueous solution.

  Iron, copper, stainless steel, nickel, and aluminum can be used as the current collector of the electrode. Moreover, a sheet | seat, a foam, a mesh, a porous body, an expanded lattice, etc. can be used as the shape. Further, the current collector can be used with a hole formed in an arbitrary shape.

  As an organic solvent used in the electrolytic solution, ethylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran , 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate, etc., alone or in combination Can be used. Also, carbonate compounds such as vinylene carbonate and butylene carbonate, benzene compounds such as biphenyl and cyclohexylbenzene, and sulfur compounds such as propane sultone can be used alone or in the electrolyte.

Furthermore, it can use combining electrolyte solution and a solid electrolyte. As the solid electrolyte, a crystalline or 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), Li _{0. 5-3x} R _{0. 5 + x} TiO ₃ (R = La, Pr, Nd, Sm), or thio LISICON represented by Li _4-x Ge _1-x P _x S ₄ can be used, and the latter includes LiI-Li ₂ O—B ₂ O ₅ system, Li _{A 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 can be used.

Examples of the salt dissolved in the organic solvent include 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 , LiC ₄ BO ₈ or the like can be used alone or in combination. Among these, LiPF ₆ is preferable as the lithium salt because the cycle performance is good. Furthermore, the concentration of these lithium salts is preferably in the range of 0.5 to 2.0 mol / dm ³ .

  A microporous membrane such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, and polyolefin can be used as a separator for a nonaqueous electrolyte secondary battery.

  The shape of the nonaqueous electrolyte secondary battery is not particularly limited, and a rectangular shape, an elliptical shape, a coin shape, a button shape, a sheet shape, and the like can be used.

  Below, this invention is demonstrated in detail based on an Example. However, the present invention is not limited to the following examples.

[Examples 1 to 4 and Comparative Examples 1 to 10]
[Example 1]
After dispersing 5.0 g of transition metal hydroxide (Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ ) in 125 ml of 7.0 mol / dm ³ lithium hydroxide aqueous solution at 80 ° C., 12% Sodium hypochlorite (43 ml) was added and the mixture was kept at 80 ° C. and stirred for 3 hours. After filtering this, 21 ml of a 14.0 mol / dm ³ lithium hydroxide aqueous solution was added, stirred for 0.5 hour, filtered, dried at 65 ° C. for 12 hours, and H _0.2 Li _0. A powder a of proton-containing transition metal oxide of the present invention represented by ₈ Co _1/2 Ni _1/3 Mn _1/6 O ₂ was obtained.

  A paste was prepared by mixing 89% by mass of this powder a (positive electrode active material), 4% by mass of acetylene black and 7% by mass of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP). . This paste was applied onto an aluminum foil having a thickness of 20 μm and dried under reduced pressure at 150 ° C. to evaporate NMP. After pressing this with a roller, it was made into a size of 30 mmW × 40 mmL × 50 μmT with a slitter to produce a positive electrode A containing the proton-containing transition metal oxide powder a of the present invention.

[Example 2]
Example 1 except that Co _1/3 Ni _1/3 Mn _1/3 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner, a proton-containing transition metal oxide powder b of the present invention represented by H _0.2 Li _0.8 Co _1/3 Ni _1/3 Mn _1/3 O ₂ was obtained. A positive electrode B containing the powder b was produced in the same manner as in Example 1 except that the powder b was used instead of the powder a.

[Example 3]
Example 1 except that Co _2/3 Ni _1/6 Mn _1/6 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a proton-containing transition metal oxide powder c of the present invention represented by H _0.2 Li _0.8 Co _2/3 Ni _1/6 Mn _1/6 O ₂ was obtained. A positive electrode C containing the powder c was produced in the same manner as in Example 1 except that the powder c was used instead of the powder a.

[Example 4]
Example 1 except that Co _1/2 Ni _1/6 Mn _1/3 (OH) ₂ was used as the transition metal hydroxide instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ In the same manner as above, a proton-containing transition metal oxide powder d represented by H _0.2 Li _0.8 Co _1/2 Ni _1/6 Mn _1/3 O ₂ was obtained. A positive electrode D containing the powder d was produced in the same manner as in Example 1 except that the powder d was used instead of the powder a.

[Comparative Example 1]
Example 1 except that Co _7/12 Ni _1/3 Mn _1/12 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a proton-containing transition metal oxide powder e of the present invention represented by H _0.4 Li _0.6 Co _7/12 Ni _1/3 Mn _1/12 O ₂ was obtained. A positive electrode E containing the powder e was produced in the same manner as in Example 1 except that the powder e was used instead of the powder a.

[Comparative Example 2]
Example 1 except that Co _1/4 Ni _1/3 Mn _5/12 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner, a proton-containing transition metal oxide powder f represented by the present invention represented by H _0.8 Li _0.2 Co _1/4 Ni _1/3 Mn _5/12 O ₂ was obtained. A positive electrode F containing the powder f was produced in the same manner as in Example 1 except that the powder f was used instead of the powder a.

[Comparative Example 3]
Example 1 except that Co _3/4 Ni _1/6 Mn _1/12 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a powder g of proton-containing transition metal oxide of the present invention represented by H _0.4 Li _0.6 Co _3/4 Ni _1/6 Mn _1/12 O ₂ was obtained. A positive electrode G containing the powder g was produced in the same manner as in Example 1 except that the powder g was used instead of the powder a.

[Comparative Example 4]
Example 1 except that Co _5/12 Ni _1/6 Mn _5/12 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a proton-containing transition metal oxide powder h represented by H _0.8 Li _0.2 Co _5/12 Ni _1/6 Mn _5/12 O ₂ was obtained. A positive electrode H containing the powder h was produced in the same manner as in Example 1 except that the powder h was used instead of the powder a.

[Comparative Example 5]
Example 1 except that Co _7/12 Ni _1/12 Mn _1/3 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a proton-containing transition metal oxide powder i of the present invention represented by H _0.4 Li _0.6 Co _7/12 Ni _1/12 Mn _1/3 O ₂ was obtained. A positive electrode I containing the powder i was produced in the same manner as in Example 1 except that the powder i was used instead of the powder a.

[Comparative Example 6]
Example 1 except that Co _1/4 Ni _5/12 Mn _1/3 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a proton-containing transition metal oxide powder j represented by H _0.5 Li _0.5 Co _1/4 Ni _5/12 Mn _1/3 O ₂ was obtained. A positive electrode J containing the powder j was produced in the same manner as in Example 1 except that the powder j was used instead of the powder a.

[Comparative Example 7]
Example 1 except that Co _3/4 Ni _1/12 Mn _1/6 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner, a proton-containing transition metal oxide powder k of the present invention represented by H _0.4 Li _0.6 Co _3/4 Ni _1/12 Mn _1/6 O ₂ was obtained. A positive electrode K containing the powder k was produced in the same manner as in Example 1 except that the powder k was used instead of the powder a.

[Comparative Example 8]
Example 1 except that Co _5/12 Ni _5/12 Mn _1/6 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner as above, a proton-containing transition metal oxide powder l represented by H _0.5 Li _0.5 Co _5/12 Ni _5/12 Mn _1/6 O ₂ was obtained. A positive electrode L containing the powder l was produced in the same manner as in Example 1 except that the powder l was used instead of the powder a.

[Comparative Example 9]
Example 1 except that Co _1/6 Ni _1/6 Mn _2/3 (OH) ₂ was used in place of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide In the same manner, a proton-containing transition metal oxide powder m represented by the present invention represented by H _0.8 Li _0.2 Co _1/6 Ni _1/6 Mn _2/3 O ₂ was obtained. A positive electrode M containing the powder m was produced in the same manner as in Example 1 except that the powder m was used instead of the powder a.

[Comparative Example 10]
97 g of the same transition metal hydroxide (Co _2/3 Ni _1/6 Mn _1/6 (OH) ₂ ) as in Example 1 was mixed with 74 g of lithium carbonate and sintered at 1000 ° C. for 12 hours in the atmosphere. Thus, a proton-containing transition metal oxide powder n represented by LiCo _2/3 Ni _1/6 Mn _1/6 O ₂ was obtained. A positive electrode N containing the powder n was produced in the same manner as in Example 1 except that the powder n was used instead of the powder a.

[Composition analysis of proton-containing transition metal oxides]
The lithium content contained in the powders a to n obtained in Examples 1 to 4 and Comparative Examples 1 to 10 was quantified using inductively coupled plasma analysis (ICP). Moreover, the average valence of the transition metals of the powders a to n was measured by redox titration.

The composition of the proton-containing transition metal oxide contained in the powders a to n is shown in Table 1. In Table 1, “y (Li content)” indicates a molar ratio of Li / (Coi + Ni + Mn). Moreover, since the average valences of the transition metals of the powders a to n were all 3.0, x + y = 1, so the amount (x) of H per mole contained in the powders a to n is Calculated from (2).
x = 1.0-y (Li content) (2)

[Measurement of electrochemical potential behavior]
The positive electrodes A to D obtained in Examples 1 to 4 and the positive electrodes E to N obtained in Comparative Examples 1 to 10 were used as a reference electrode and a counter electrode, a metallic lithium plate, and a volume ratio 1 of EC and DEC as an electrolytic solution. A tripolar glass cell was prepared using 1 mol / dm ³ LiClO ₄ dissolved in a 1: 1 mixed solvent. The electrochemical potential behavior of this electrode was examined as follows.

At 25 ° C., 4.3 Vvs. At a current of 0.1 CmA. After charging to Li / Li ⁺ , 1.5Vvs. Discharge was performed to Li / Li ⁺ . The charge capacity and discharge capacity of the first cycle are shown in Table 2.

  As can be seen from Table 2, in the positive electrodes A to D of Examples 1 to 4, compared with the positive electrode N of Comparative Example 10, a particularly large charge electric charge and activity of 193.4 to 194.9 mAh per mass of the active material were obtained. A large discharge capacity of 285.2 to 290.9 mAh per mass of material could be obtained.

  Here, it was clarified that the charge in which the potential is preciously shifted in the first cycle is desorption of lithium, and that lithium can be electrochemically desorbed from the proton-containing transition metal oxide.

  On the other hand, in the positive electrodes E to M of Comparative Examples 1 to 9, a sufficient charge / discharge capacity was not obtained. The reason is considered to be that Mn substituted for the purpose of controlling the valence of Ni was not sufficiently dissolved.

The proton-containing transition metal oxide powders a to d used in Examples 1 to 4 were all x + y = 1 before assembling the batteries, but the values of x + y were the concentrations of the lithium hydroxide aqueous solution and the oxidizing agent. Depending on the synthesis conditions such as reaction temperature and reaction time, any value can be obtained. For example, in Example 1, when the concentration of the lithium hydroxide aqueous solution is 3.5 mol / dm ³ and the stirring time is 12 hours, the transition metal has an average valence of 2.5 and y = 0.6. A transition metal oxide was obtained. Here, since x + y = 1.5, x = 0.9.

[Examples 5 and 6]
[Example 5]
The electrode A containing the positive electrode active material powder a obtained in Example 1 was used as a positive electrode plate. A metal Li foil having a size of 30 mmW × 40 mmL was used as the negative electrode plate. The positive electrode and the negative electrode thus obtained were stacked with a polyethylene separator, which is a continuous porous body having a thickness of 20 μm and a porosity of 40%, sandwiched therebetween, and placed in a container having a height of 70 mm, a width of 34 mm, and a thickness of 1 mm. The nonaqueous electrolyte secondary battery O of Example 5 of the present invention was obtained by inserting and injecting a nonaqueous electrolyte therein. As this non-aqueous electrolyte, a solution obtained 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 was used.

[Example 6]
The electrode A containing the positive electrode active material powder a obtained in Example 1 was used as a positive electrode plate. Further, 80% by mass of flaky graphite having an average particle size of 10 μm and 20% by mass of PVDF were mixed in NMP to prepare a paste. This paste was applied onto a copper foil having a thickness of 15 μm and dried at 150 ° C. to evaporate NMP. This was compression molded with a roll press and cut into a size of 30 mmW × 40 mmL × 35 μmT with a slitter to prepare a negative electrode plate.

Furthermore, the positive electrode and the negative electrode thus obtained were stacked with a polyethylene separator, which is a continuous porous body having a thickness of 20 μm and a porosity of 40%, interposed therebetween, and had a height of 70 mm, a width of 34 mm, and a thickness of 1 mm. The nonaqueous electrolyte secondary battery P of Example 6 of the present invention was obtained by inserting it into the container and injecting a nonaqueous electrolyte therein. As this non-aqueous electrolyte, a solution obtained 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 was used.

  The batteries O and P were charged at a constant current-constant voltage of up to 4.2 V at 0.2 CmA at 25 ° C. for 8 hours, and then discharged at a constant current of 0.2 CmA up to 1.5 V for 50 cycles. The ratio at the 50th cycle to the discharge capacity at the 1st cycle is defined as “discharge capacity maintenance rate,%”. The results are shown in Table 3 together with the charge amount and discharge capacity in the first cycle.

  Each of these batteries could be repeatedly charged and discharged. In addition, the battery P of Example 6 has a discharge that continuously changes from 4.2 V to 1.5 V, and the value of the discharge capacity corresponds to about 147 mAh / g per positive electrode. is there. Furthermore, the discharge capacity retention rate after 50 cycles was 92.0%, which was superior to the battery O of Example 5 using a lithium metal negative electrode, indicating excellent cycle performance.

[Examples 7 to 12]
[Example 7]
Other than using Co _5/12 Ni _1/3 Mn _1/6 Al _1/12 (OH) ₂ instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide Is a powder of a proton-containing transition metal oxide of the present invention represented by H _0.2 Li _0.8 Co _5/12 Ni _1/3 Mn _1/6 Al _1/12 O ₂ as in Example 1. q was obtained. A positive electrode Q containing the powder q was produced in the same manner as in Example 1 except that the powder q was used instead of the powder a.

[Example 8]
Other than using Co _5/12 Ni _1/3 Mn _1/6 Mg _1/12 (OH) ₂ instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide Is a proton-containing transition metal oxide powder represented by H _0.2 Li _0.8 Co _5/12 Ni _1/3 Mn _1/6 Mg _1/12 O ₂ as in Example 1. r was obtained. A positive electrode R containing the powder r was produced in the same manner as in Example 1 except that the powder r was used instead of the powder a.

[Example 9]
Other than using Co _5/12 Ni _1/3 Mn _1/6 Zn _1/12 (OH) ₂ instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide Is a powder of a proton-containing transition metal oxide of the present invention represented by H _0.2 Li _0.8 Co _5/12 Ni _1/3 Mn _1/6 Zn _1/12 O ₂ in the same manner as in Example 1. s was obtained. A positive electrode S containing the powder s was produced in the same manner as in Example 1 except that the powder s was used instead of the powder a.

[Example 10]
Other than using Co _5/12 Ni _1/3 Mn _1/6 Cr _1/12 (OH) ₂ instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide Is a powder of the proton-containing transition metal oxide of the present invention represented by H _0.2 Li _0.8 Co _5/12 Ni _1/3 Mn _1/6 Cr _1/12 O ₂ as in Example 1. t was obtained. A positive electrode T containing the powder t was produced in the same manner as in Example 1 except that the powder t was used instead of the powder a.

[Example 11]
Other than using Co _4/10 Ni _1/3 Mn _1/6 Al _1/10 (OH) ₂ instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide in the same manner as in example _1, the proton-containing transition metal oxide of the present invention represented by _{H 0.2 Li 0.8 C o 4/} 10 Ni 1/3 Mn 1/6 Al 1/10 O 2 A powder u was obtained. A positive electrode U containing the powder u was produced in the same manner as in Example 1 except that the powder u was used instead of the powder a.

[Example 12]
Other than using Co _4/10 Ni _1/3 Mn _1/6 Mg _1/10 (OH) ₂ instead of Co _1/2 Ni _1/3 Mn _1/6 (OH) ₂ as the transition metal hydroxide Is a powder of a proton-containing transition metal oxide of the present invention represented by H _0.2 Li _0.8 Co _4/10 Ni _1/3 Mn _1/6 Mg _1/10 O ₂ as in Example 1. v was obtained. A positive electrode V containing the powder v was produced in the same manner as in Example 1 except that the powder v was used instead of the powder a.

[Measurement of electrochemical potential behavior]
Electrochemical potential behavior of the positive electrodes Q to V obtained in Examples 7 to 12 was examined using the same tripolar glass cell as in Example 1 under the same conditions as in Example 1. The charge capacity and discharge capacity in the first cycle are shown in Table 4.

As can be seen from Table 4, in the positive electrodes Q to V of Examples 7 to 12, it was found that the amount of charge and the discharge capacity per mass of the active material were comparable to those of Examples 1 to 4. From this result, a part of Co in the proton-containing transition metal oxide represented by H0.2Li0.8Co1 / 2Ni1 / 3Mn1 / 6O2 is substituted with a metal element other than Co, Ni, Mn, and the substitution amount is 1 / in the case of 10 or less, it was found that the amount of charge and discharge capacity of Ri per mass of comparable active material and if not replaced can be obtained.

Claims (3)

Formula _{H x Li y Co 1-a} -b-c Ni a Mn b M c O 2 ( where the metal element M is selected Al, Mg, Zn, and from Cr, 0 <x ≦ 1,0 < y ≦ 1, 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ 1/10, 1/3 ≦ a + b ≦ 2/3) A positive electrode active material for a non-aqueous electrolyte secondary battery. Formula _{Co 1-a-b-c} Ni a Mn b M c (OH) 2 ( where the metal element M is selected Al, Mg, Zn, and from Cr, 0 <x ≦ 1,0 < y ≦ 1 0 <x + y ≦ 2, 1/6 ≦ a ≦ 1/3, 1/6 ≦ b ≦ 1/3, 0 ≦ c ≦ 1/10, 1/3 ≦ a + b ≦ 2/3) after contacting the solution containing a transition metal hydroxide and lithium ion and an oxidizing agent, a non-aqueous electrolyte according to claim 1, wherein is passed through the resulting product in a solution containing lithium ions, characterized in Rukoto A method for producing a positive electrode active material for a secondary battery. A nonaqueous electrolyte secondary battery comprising the positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1.