JPWO2010082240A1 - Composite oxide and method for producing the same, and nonaqueous electrolyte secondary battery using the composite oxide - Google Patents

Abstract

Provided is a composite oxide containing at least nickel and lithium, which can enhance charge / discharge characteristics of a secondary battery when used as an electrode active material. The method for producing a composite oxide is a method for producing a composite oxide containing at least nickel and lithium, a mixing step of mixing at least a nickel raw material and a lithium raw material to obtain a mixture, and firing the mixture. And a firing step for obtaining a composite oxide. The nickel raw material contains metallic nickel.

Description

  The present invention relates to a composite oxide, a method for producing the same, and a non-aqueous electrolyte secondary battery using the composite oxide.

  In recent years, secondary batteries that are small and light and have a high energy density have been desired as power sources for portable devices and automobiles, and demand for non-aqueous electrolyte secondary batteries is rapidly increasing. Among non-aqueous electrolyte secondary batteries, a lithium ion secondary battery using a carbon material that can occlude and release lithium ions for the negative electrode and a lithium transition metal composite oxide for the positive electrode It is rapidly spreading due to its small weight and high energy density.

  Currently, lithium cobalt oxide is widely used as a lithium transition metal composite oxide that is a positive electrode material. However, cobalt is a very expensive metal and has limited resources. Therefore, development of an active material with reduced cobalt content and replacement of the active material are desired. In recent years, lithium manganate, lithium nickelate, and lithium transition metal composite oxides in which some of these oxides are substituted with other metal elements have attracted attention. Nickel and manganese are relatively inexpensive metals compared to cobalt and can be supplied stably. Among these materials, lithium nickelate, which has the same crystal structure as lithium cobaltate, shows a lower electrochemical potential than lithium cobaltate, so high capacity is expected by using lithium nickelate as the positive electrode material. it can.

Therefore, it has been proposed to use lithium nickelate as a positive electrode material. For example, Japanese Patent Laid-Open No. 9-241027 (hereinafter referred to as Patent Document 1) discloses a composition formula Li capable of charging and discharging a large capacity by baking lithium oxide and nickel oxide in an inert gas-oxygen mixed atmosphere. It is described that a lithium nickel oxide represented by ₂ NiO _{2 + y} is obtained.

It has also been proposed to use a lithium nickel composite oxide in which a part of lithium nickelate is substituted with a metal element such as manganese as a positive electrode material. JP-A-8-45509 (hereinafter referred to as Patent Document 2) discloses Li _w Ni _x Co _y B _z O as a positive electrode active material capable of maintaining good battery performance during use and storage in a high temperature environment. A lithium nickel composite oxide represented by ₂ is disclosed.

JP-A-9-241027 JP-A-8-45509

  However, in the method for producing a lithium nickel composite oxide described in Patent Document 1 and Patent Document 2, nickel oxide is used as a nickel raw material. When nickel oxide is used as a raw material, the reactivity between nickel oxide and lithium carbonate is poor. Therefore, nickel oxide tends to remain in the manufacturing process of the lithium nickel composite oxide, and it is difficult to produce a layered rock salt structure. Therefore, when a lithium nickel composite oxide synthesized using nickel oxide as a raw material is used as a positive electrode active material such as a non-aqueous electrolyte secondary battery, the charge / discharge characteristics of the obtained secondary battery are insufficient. There is a problem that it is low.

  Accordingly, an object of the present invention is to provide a composite oxide containing at least nickel and lithium, which can enhance the charge / discharge characteristics of a secondary battery when used as an electrode active material.

  As a result of intensive studies to achieve the above object, the present inventors have produced a composite oxide containing at least nickel and lithium by using a nickel raw material containing nickel metal, thereby producing the composite oxide. It has been found that when used as an electrode active material, a composite oxide capable of improving the charge / discharge characteristics of the secondary battery can be obtained. Based on this knowledge, the present invention has the following features.

  The method for producing a composite oxide according to the present invention is a method for producing a composite oxide containing at least nickel and lithium, wherein at least a nickel raw material and a lithium raw material are mixed to obtain a mixture, and And a firing step of firing the mixture to obtain a composite oxide. The nickel raw material contains metallic nickel.

  In the method for producing a composite oxide of the present invention, the composite oxide may contain at least one metal element other than nickel and lithium.

  Moreover, in the manufacturing method of the complex oxide of this invention, it is preferable to contain manganese as said metal element. In this case, in the mixing step, the raw material of manganese is further mixed to obtain a mixture. In this case, it is preferable that the raw material of manganese contains at least one selected from the group consisting of manganese dioxide, trimanganese tetroxide, and manganese carbonate.

  Furthermore, in the method for producing a composite oxide of the present invention, cobalt can be contained as the metal element. In this case, in the mixing step, a cobalt raw material is further mixed to obtain a mixture. In this case, the cobalt raw material preferably contains at least one selected from the group consisting of cobalt hydroxide and cobalt tetroxide.

  Furthermore, in the method for producing a composite oxide of the present invention, it is preferable that the lithium raw material contains lithium carbonate.

  In the method for producing a composite oxide of the present invention, the average particle diameter of metallic nickel is preferably less than 10 μm.

  The composite oxide according to the present invention is manufactured by a manufacturing method having any of the above-described characteristics.

  A non-aqueous electrolyte secondary battery according to the present invention uses the above composite oxide as an electrode active material.

  According to this invention, when used as an electrode active material, it is possible to obtain a composite oxide containing at least nickel and lithium that can improve the charge / discharge characteristics of the secondary battery.

It is a figure which shows the relationship between the average particle diameter of metal nickel powder used in Example 3, and charging / discharging capacity | capacitance.

  The present invention is a method for producing a composite oxide containing at least nickel and lithium, the step of mixing at least a nickel raw material and a lithium raw material to obtain a mixture, and firing the mixture to obtain a composite oxide. The manufacturing method provided with the baking process to obtain. In the production method of the present invention, the nickel raw material contains metallic nickel. According to the present invention, when used as an electrode active material, it is possible to synthesize a complex oxide having a high charge / discharge capacity and further having good cycle characteristics. When metallic nickel is used as the raw material for nickel, the reaction between metallic nickel and lithium carbonate begins below the melting point of lithium carbonate, which is the lithium raw material, so that the composite oxide after heat treatment is difficult to aggregate and good characteristics are obtained. It is done.

  The composite oxide obtained by the production method of the present invention may be lithium nickelate obtained by mixing and firing a nickel raw material containing metallic nickel and a lithium raw material, and includes at least nickel and lithium, A nickel-containing lithium transition metal composite oxide containing a metal element other than nickel and lithium may be used. This nickel-containing lithium transition metal composite oxide is obtained by mixing and firing a nickel raw material containing metallic nickel, a lithium raw material, and a raw material containing at least one metal element other than nickel and lithium. It is a complex oxide. Examples of the metal element include manganese and cobalt.

  Examples of manganese raw materials include manganese oxides, carbonates, inorganic acid salts, organic acid salts, and chlorides. Specifically, manganese dioxide, manganese tetraoxide, and manganese carbonate are included in the group. It is preferable to use at least one selected from the above. Examples of cobalt raw materials include cobalt oxides, carbonates, inorganic acid salts, organic acid salts, and chlorides. Specifically, the cobalt raw materials are selected from the group consisting of cobalt hydroxide and cobalt tetroxide. It is preferable to use at least one selected from the above. In addition to these elements, various metal elements such as iron, chromium, vanadium, titanium, copper, aluminum, gallium, bismuth, tin, zinc, magnesium, germanium, niobium, tantalum, and zirconium can be mentioned. Multiple types can also be used in combination. Examples of the raw material for the metal element include oxides, carbonates, inorganic acid salts, organic acid salts, and chlorides of the above metal elements.

Complex oxide obtained by the production method of the present invention, the composition formula _{Li 1 + α Ni x Mn y} Co z M b O 2 + c (-1 <a ≦ 0.5,0 ≦ b <0.3, -0.1 < c <0.1, 0 <x <1, 0 <y <1, 0 <z <0.34, x + y + z = 1, and M represents a metal element other than Ni, Mn, and Co). Preferably there is.

  Examples of the lithium source include lithium oxides, carbonates, inorganic acid salts, organic acid salts, and chlorides. Specifically, lithium carbonate is preferably used.

  Furthermore, the average particle diameter of the metallic nickel used in the production method of the present invention is preferably less than 10 μm.

  In the production method of the present invention, the reaction temperature, reaction atmosphere, production process and the like are not particularly limited, and can be arbitrarily set in consideration of the required characteristics and productivity of the secondary battery. .

  A non-aqueous electrolyte secondary battery using a composite oxide obtained by the production method of the present invention as an electrode active material is for isolating at least a positive electrode, a negative electrode, a liquid electrolyte or a solid electrolyte, and a positive electrode and a negative electrode. And a separator.

  An example of a method for producing the above nonaqueous electrolyte secondary battery will be described.

  First, an electrode active material is formed into an electrode shape. For example, an electrode active material is mixed with a conductive additive and a binder, and optionally mixed with a solid electrolyte, and an organic solvent is added to prepare a slurry. This slurry is coated on the positive electrode current collector by an arbitrary coating method, and dried to form the positive electrode.

  Here, the conductive auxiliary agent is not particularly limited, and examples thereof include carbonaceous fine particles such as graphite, carbon black, and acetylene black, carbon fibers such as vapor grown carbon fiber (VGCF), carbon nanotube, and carbon nanohorn, Conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, polyacene and the like can be used as a conductive aid. Further, two or more kinds of these conductive auxiliary agents can be mixed and used. In addition, the content of the conductive auxiliary agent in the positive electrode is preferably 3 to 80% by weight.

  Also, the binder is not particularly limited, and polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, fluorinated polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile. -Various resins such as butadiene rubber, fluoro rubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, polyethylene oxide, carboxymethyl cellulose, and nitrocellulose can be used as a binder.

  Further, the organic solvent is not particularly limited, and basic solvents such as dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, propylene carbonate, diethyl carbonate, dimethyl carbonate, and γ-butyrolactone, acetonitrile, tetrahydrofuran, nitrobenzene, acetone Nonaqueous solvents such as methanol, protic solvents such as methanol and ethanol, and the like can be used as the organic solvent.

The solid electrolyte is not particularly limited, and a polyethylene oxide polymer, a polymer containing a polyorganosiloxane chain or a polyoxyalkylene chain, Li ₂ S—SiS ₂ , Li ₂ S—GeS ₂ , Li ₂ S— P ₂ S ₅ , Li ₂ S—B ₂ S ₃ or the like can be used as the solid electrolyte.

  Note that the type and blending ratio of the organic solvent, the type and addition amount of the solid electrolyte, and the like can be arbitrarily set in consideration of the required characteristics and productivity of the secondary battery.

  For example, a coin-type secondary battery is manufactured using the positive electrode formed in this way, and an electrolyte, a separator, and a negative electrode.

  Examples of the negative electrode active material constituting the negative electrode include carbon materials capable of inserting and extracting lithium ions, metals such as aluminum, magnesium, tin, and silicon, metal oxides, metal sulfides, metal nitrides, lithium alloys, etc. Can be used. As the carbon material, graphite material such as graphite, coke, carbon fiber, spherical carbon or carbonaceous material, thermosetting resin, isotropic pitch, mesophase pitch-based carbon fiber, mesophase microsphere, etc. can be used. .

As the electrolyte, a liquid or solid electrolyte can be used. As the liquid electrolyte, a nonaqueous electrolytic solution in which a lithium salt is dissolved in an organic solvent is usually used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiOSO ₂ CF ₃ , LiAlCl ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiOSO ₂ C ₄ F _{9 and the} like. Can be used.

  Also, as the organic solvent, carbonate solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and methyl isopropyl carbonate, ester solvents such as γ-butyrolactone, methyl formate, and methyl acetate should be used. Can do. One or more of these organic solvents may be used in combination. It is also possible to add additives such as vinylene carbonate.

 As the solid electrolyte, the above-listed compounds and the like can be used, and a gel-like one in which the above liquid electrolyte is held in a polyethylene oxide polymer can also be used. In addition, the type and blending ratio of the electrolyte, the type and amount of additive, and the like can be arbitrarily set in consideration of the required characteristics and productivity of the secondary battery.

  As the separator, a microporous polymer film is usually used. For example, polyolefin resins such as polytetrafluoroethylene, polyester, nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polyethylene, and polypropylene are used. Further, a nonwoven fabric filter such as glass fiber, a nonwoven fabric filter of glass fiber and polymer fiber, and the like can also be used.

  The shape of the nonaqueous electrolyte secondary battery using the composite oxide of the present invention, for example, a lithium ion secondary battery is not particularly limited, and may be any of a paper type, a coin type, a cylindrical type, a square type, and the like. May be. Further, the exterior form is not particularly limited, and a metal case, a mold resin, an aluminum laminate film, or the like may be used.

  According to the embodiment of the present invention configured as described above, since the non-aqueous electrolyte secondary battery is configured using the composite oxide as an electrode active material, the non-aqueous electrolyte secondary battery having a high charge / discharge capacity is formed. A secondary battery can be obtained. In addition, a non-aqueous electrolyte secondary battery having a relatively low capacity reduction and good cycle characteristics even after repeated charge and discharge can be obtained.

  In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible in the range which does not deviate from a summary.

  Moreover, the Example shown below is an example and this invention is not limited to the following Example.

Example 1
As nickel raw materials, metallic nickel powder having an average particle size of 0.5 μm, cobalt trioxide as a cobalt raw material, manganese trioxide as a manganese raw material, and lithium carbonate as a lithium raw material were used. These raw materials were weighed so that a molar ratio of Li: Ni: Mn: Co = 1.1: 0.33: 0.33: 0.33 and mixed with pure water to prepare a slurry. The obtained slurry was sprayed and dried, and the obtained dry powder was heat-treated in the atmosphere at a temperature of 950 ^° C. for 40 hours to synthesize a composite oxide.

  Using the obtained composite oxide, a secondary battery was produced as follows, and the charge / discharge capacity was measured.

88% by weight of the composite oxide synthesized by the above method as a positive electrode active material, 6% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of polyvinylidene fluoride (PVDF) as a binder are mixed together, and N-methyl A slurry was prepared by dispersing in -2-pyrrolidone (NMP). This slurry was applied on an aluminum foil having a thickness of 20 μm at a coating amount of 10 mg / cm ² , dried and pressed to prepare an electrode sheet. The obtained electrode sheet was punched out into a disc having a diameter of 14 mm to produce a positive electrode.

A secondary battery was prepared using metallic lithium as a negative electrode, a polyethylene porous membrane as a separator, and a 3: 7 (weight ratio) mixture of ethylene carbonate and diethyl carbonate using 1 mol / L LiPF ₆ as a supporting salt as an electrolyte. .

  The charge / discharge performance evaluation of the produced secondary battery was performed. A 30-cycle charge / discharge test was conducted at a current value of 400 μA in a voltage range of 3.0 V to 4.3 V.

  Table 1 shows the results of charge / discharge performance evaluation. The initial charge capacity was 173 mAh / g, and the initial discharge capacity was 154 mAh / g. The discharge capacity at the 30th cycle was as high as 152 mAh / g, and good cycle characteristics were obtained.

(Example 2)
As nickel raw materials, metallic nickel powder having an average particle size of 0.5 μm, cobalt trioxide as a cobalt raw material, and lithium carbonate as a lithium raw material were used.

These raw materials were weighed so that a molar ratio of Li: Ni: Mn: Co = 1.1: 0.80: 0: 0.20 and mixed with pure water to prepare a slurry. The obtained slurry was sprayed and dried, and the obtained dry powder was heat-treated in oxygen at a temperature of 750 ^° C. for 40 hours to synthesize a composite oxide.

  Using the obtained composite oxide, a secondary battery was produced in the same manner as in Example 1, and the charge / discharge performance was measured.

  Table 1 shows the results of charge / discharge performance evaluation. The initial charge capacity was 207 mAh / g, and the initial discharge capacity was 185 mAh / g. The discharge capacity at the 30th cycle was as high as 181 mAh / g, and good cycle characteristics were obtained.

Example 3
A composite oxide was synthesized in the same manner as in Example 2. However, the nickel raw material has a mean particle size of 0.2, 0.5, 3.5, 5.0, and 10 μm. The metallic nickel powder has a different particle size, the manganese raw material is manganese trioxide, the cobalt raw material Lithium carbonate was used as a raw material for cobalt trioxide and lithium.

  Using the obtained nickel-containing lithium transition metal compound, a battery was produced in the same manner as in Example 1, and the charge / discharge performance was measured.

  FIG. 1 shows the results of charge / discharge performance evaluation.

When metallic nickel powder having an average particle diameter of 10 μm was used, the initial charge capacity was 200 mAh / g, and the initial discharge capacity was 172 mAh / g, which were high values. The discharge capacity at the 30th cycle was as high as 165 mAh / g, and good cycle characteristics were obtained.

  In addition, when metallic nickel powder having an average particle diameter of 0.5 μm is used, the initial charge capacity is 205 mAh / g, and the initial discharge capacity is 186 mAh / g, which is higher than when metallic nickel powder having an average particle diameter of 10 μm is used. showed that. Furthermore, the discharge capacity at the 30th cycle was as high as 182 mAh / g, and good cycle characteristics were obtained. This may be because the reaction with lithium carbonate easily progressed by using a metal nickel powder having a small particle size as a raw material.

  From the above results, it was found that higher charge / discharge characteristics and cycle characteristics can be obtained by using metallic nickel powder having a small average particle size as a raw material. Accordingly, the particle diameter of the metallic nickel powder is preferably less than 10 μm.

(Comparative Example 1)
A composite oxide was synthesized in the same manner as in Example 1. However, nickel oxide having an average particle size of 0.9 μm was used as a nickel raw material.

  Using the obtained nickel-containing lithium transition metal compound, a secondary battery was produced in the same manner as in Example 1, and the charge / discharge performance was measured.

  Table 1 shows the results of charge / discharge performance evaluation. As a result of the charge / discharge test, the initial charge capacity was 170 mAh / g, the initial discharge capacity was 144 mAh / g, and the discharge capacity at the 30th cycle was 138 mAh / g. The results were inferior to those of Example 1.

(Comparative Example 2)
A composite oxide was synthesized in the same manner as in Example 2. However, nickel oxide having an average particle size of 0.9 μm was used as the nickel raw material.

  Using the obtained nickel-containing lithium transition metal compound, a secondary battery was produced in the same manner as in Example 1, and the charge / discharge performance was measured.

  Table 1 shows the results of charge / discharge performance evaluation. As a result of the charge / discharge test, the initial charge capacity was 173 mAh / g, the initial discharge capacity was 150 mAh / g, and the discharge capacity at the 30th cycle was 129 mAh / g. The result was inferior to that of Example 2.

  It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the scope and meaning equivalent to the scope of claims.

  According to this invention, when used as an electrode active material, it is possible to obtain a composite oxide containing at least nickel and lithium, which can improve the charge / discharge characteristics of the secondary battery. In addition, it is possible to obtain a non-aqueous electrolyte secondary battery having a relatively small capacity reduction even when charging and discharging are repeated and having good cycle characteristics.

Claims (10)

A method for producing a composite oxide containing at least nickel and lithium,
A mixing step of mixing at least a nickel raw material and a lithium raw material to obtain a mixture;
A firing step of firing the mixture to obtain a composite oxide,
A method for producing a composite oxide, wherein the nickel raw material contains metallic nickel.   The method for producing a composite oxide according to claim 1, wherein the composite oxide contains at least one metal element other than nickel and lithium. The composite oxide contains manganese as the metal element;
The method for producing a composite oxide according to claim 2, wherein, in the mixing step, the raw material of manganese is further mixed to obtain the mixture.   The method for producing a composite oxide according to claim 3, wherein the raw material of manganese contains at least one selected from the group consisting of manganese dioxide, trimanganese tetraoxide, and manganese carbonate. The composite oxide contains cobalt as the metal element;
5. The method for producing a composite oxide according to claim 2, wherein, in the mixing step, a cobalt raw material is further mixed to obtain the mixture. 6.   The method for producing a composite oxide according to claim 5, wherein the cobalt raw material contains at least one selected from the group consisting of cobalt hydroxide and cobalt tetroxide.   The method for producing a composite oxide according to claim 1, wherein the lithium raw material contains lithium carbonate.   The method for producing a composite oxide according to any one of claims 1 to 7, wherein an average particle diameter of the metallic nickel is less than 10 µm.   A composite oxide produced by the production method according to any one of claims 1 to 8. A nonaqueous electrolyte secondary battery using the composite oxide according to claim 9 as an electrode active material.

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