JP2010267487A - Lithium transition metal composite oxide and method of manufacturing the same, as well as nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium transition metal composite oxide having satisfactory initial charge and discharge characteristics, a method for manufacturing the same, and a nonaqueous electrolyte secondary battery. <P>SOLUTION: The method for manufacturing the lithium transition metal composite oxide uses a baking tool which is subjected to heat treatment at least once together with a lithium compound as a baking tool used for baking a raw material of the lithium transition metal composite oxide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

    The present invention relates to a lithium transition metal composite oxide, a method for producing the same, and a nonaqueous electrolyte secondary battery using the same.

  In recent years, demand for non-aqueous electrolyte secondary batteries that are small and light and have a high energy density as a power source for portable devices and automobiles is rapidly increasing. Among them, lithium ion secondary batteries 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 are rapid because of their low weight per unit of electricity and high energy density. Is popular.

  Currently, lithium transition metal composite oxides include lithium-manganese composite oxides, lithium-cobalt composite oxides, or lithium-nickel composite oxides, and composites in which some of the transition metals in these composite oxides are replaced with other metals. An oxide is used.

  These lithium transition metal composite oxides are generally synthesized by mixing and firing a compound as a raw material.

In Patent Document 1, LiOH, Ni (OH) ₂ , Mn ₃ O ₄ and Co (OH) ₂ as raw materials are wet pulverized to prepare a slurry, and the prepared slurry is spray-dried, and then placed in an alumina crucible. A method of synthesizing Li _1.05 (Ni _0.33 Mn _0.33 Co _0.33 ) O ₂ by firing in oxygen or in the air is described.

Japanese Patent Laid-Open No. 2005-141983

  However, when a firing jig made of a heat-resistant ceramic mainly composed of alumina or the like is used as a firing jig when firing the raw material of the lithium transition metal composite oxide, an electrode active having good initial charge / discharge characteristics is used. It was difficult to synthesize the material. Therefore, the present invention has been made in view of such circumstances, and the present invention provides a lithium transition metal composite oxide having better initial charge / discharge characteristics than before.

As a result of intensive studies to achieve the above object, the present inventors have used the firing jig that has been heat-treated at least once with the lithium compound as the firing jig used when firing the raw material. We obtained the knowledge that lithium transition metal complex oxides with high charge / discharge characteristics can be synthesized.
That is, the present invention is a method for producing a lithium transition metal composite oxide, comprising: mixing a raw material of the lithium transition metal composite oxide to obtain a mixture; and firing the mixture to obtain a lithium transition metal composite oxide. A firing jig that has been heat-treated at least once with a lithium compound as a pretreatment in the firing step.
The lithium transition metal composite oxide preferably contains nickel.

Furthermore, it is preferable to use lithium carbonate as the lithium compound.
Moreover, it is preferable that the said baking jig has a heat resistant ceramic as a main component.
In the heat treatment, it is preferable to heat treat the firing jig and the lithium compound at 600 ° C. to 1000 ° C.

  The lithium transition metal composite oxide of the present invention is produced by the above production method.

  The nonaqueous electrolyte secondary battery of the present invention is characterized in that the lithium transition metal composite oxide is used as an electrode active material.

  According to the present invention, a lithium transition metal composite oxide having good initial charge / discharge characteristics can be obtained.

Next, an embodiment of the present invention will be described in detail.
The present invention is a method for producing a lithium transition metal composite oxide. The production method of the present invention includes a step of mixing the raw materials of the lithium transition metal composite oxide to obtain a mixture, and a firing step of firing the mixture to obtain a lithium transition metal composite oxide. The present invention is characterized in that as a pretreatment in the firing step, a firing jig that has been heat-treated at least once with a lithium compound is used.
By using the lithium transition metal composite oxide synthesized by the production method of the present invention as an electrode active material, a non-aqueous electrolyte secondary battery having a high initial charge / discharge capacity can be obtained.
Lithium transition metal composite oxides include lithium-manganese composite oxides, lithium-cobalt composite oxides or lithium-nickel composite oxides, and composite oxides in which some of the transition metals in these composite oxides are replaced with other metals. Can be used. Examples of the other metal elements include various metal elements such as lithium, nickel, cobalt, iron, chromium, vanadium, titanium, copper, aluminum, gallium, bismuth, tin, zinc, magnesium, germanium, niobium, tantalum, and zirconium. These can be used in combination. The inventors of the present invention have a remarkable effect in the case of a lithium / nickel composite oxide containing nickel, or a composite oxide obtained by substituting a part of lithium or nickel with another metal, in addition to lithium. I got the knowledge. In particular, it has been found that when the Ni content of the lithium-containing transition metal composite oxide is included in a molar ratio of Li: Ni = 1.0: 0.4 or more, the effects of the present invention are more remarkably exhibited.
That is, it is more preferable that the lithium transition metal composite oxide contains nickel.
Moreover, as a raw material for the lithium transition metal oxide, lithium, nickel, or a compound of the above metal element is used. Specific examples include oxides, carbonates, inorganic acid salts, organic acid salts, and chlorides of the metal elements.
The firing jig used in the present invention is not limited to a shape such as a cylindrical shape, a flat plate shape, or a box shape.
Moreover, it is preferable that the firing jig used in the present invention is mainly composed of heat-resistant ceramics. As the heat-resistant ceramic, a ceramic mainly composed of alumina, zirconia, magnesia, silica or the like is preferable. More preferably, a ceramic mainly composed of alumina is preferable. A plurality of oxides other than the main components such as alumina, zirconia, magnesia, and silica may be contained.
The present invention is characterized in that as a pretreatment of the firing jig, both the firing jig and the lithium compound are heat-treated at least once. Examples of the lithium compound include Li ₂ CO ₃ , LiNO ₃ , LiOH, LiOH · H ₂ O, LiH, LiCl, LiF, LiBr, LiI, Li ₂ O, lithium sulfate, lithium nitrite, lithium acetate, lithium dicarboxylate, Examples include lithium citrate, fatty acid lithium, alkyl lithium, and lithium halide. Among these, it is more preferable that the lithium compound is lithium carbonate. Furthermore, in addition to the lithium compound, other metal elements that are constituent elements of the lithium transition metal oxide as described above may be contained. Moreover, those compounds may be contained.
The heat treatment temperature of the present invention is preferably in the range of 600 ° C to 1000 ° C.

  Next, a nonaqueous electrolyte secondary battery using the lithium transition metal composite oxide produced by the production method of the present invention as an electrode active material will be described in detail.

  The configuration of the non-aqueous electrolyte secondary battery may include at least a positive electrode and a negative electrode, and may include a liquid electrolyte or a solid electrolyte, and a separator for separating the positive electrode and the negative electrode.

  Next, an example of a method for producing the nonaqueous electrolyte secondary battery will be described in detail.

  First, an electrode active material is formed into an electrode shape. For example, an electrode active material is mixed with a conductive additive, a binder, and in some cases, a solid electrolyte, and an organic solvent is added to form a slurry. The slurry is applied onto the positive electrode current collector by an arbitrary coating method, and dried. By doing so, a positive electrode is formed.

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, and polyacene can be used. Further, two or more kinds of these conductive auxiliary agents can be mixed and used. 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. Polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, fluorinated polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene Various resins such as rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, polyethylene oxide, carboxymethyl cellulose, and nitrocellulose can be used.

  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, Nonaqueous solvents such as acetone, protic solvents such as methanol and ethanol, and the like can be used.

The solid electrolyte is not particularly limited, and is 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—. such as _{P 2 S 5, Li 2 S} -B 2 S 3 and the like.

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

  A coin-type secondary battery is manufactured using the positive electrode, electrolyte, separator, and negative electrode thus formed.

  Moreover, as the negative electrode active material constituting the negative electrode, carbonaceous materials capable of inserting and extracting lithium ions, metals such as aluminum, magnesium, tin, and silicon, metal oxides, metal sulfides, metal nitrides, A lithium alloy or the like can be used. Examples of the carbonaceous material include graphite materials such as graphite, coke, carbon fiber, and spherical carbon or carbonaceous materials, thermosetting resins, isotropic pitches, mesophase pitch-based carbon fibers, and mesophase microspheres.

A liquid or solid electrolyte can be used as the electrolyte. 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 ), LiOSO ₂ C ₄ F _{9 and the} like. Can be mentioned.

  Examples of the organic solvent include carbonate solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and methyl isopropyl carbonate, and ester solvents such as γ-butyrolactone, methyl formate, and methyl acetate. . These organic solvents may be used alone or in combination of two or more. It is also possible to add additives such as vinylene carbonate.

Examples of the solid electrolyte include the electrolytes described above, and a gel-like one in which the liquid electrolyte is held in a polyethylene oxide polymer can also be used.
In addition, the type of electrolyte, the blending ratio thereof, the type of additive, the amount of addition thereof, 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, polytetrafluoroethylene, polyester, nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polyolefin resins such as polyethylene and polypropylene, and the like are used. Moreover, a nonwoven fabric filter such as glass fiber, a nonwoven fabric filter of glass fiber and polymer fiber, or the like can also be used.

  The shape of the lithium ion secondary battery according to the present invention is not particularly limited, and may be any of a paper type, a coin type, a cylindrical type, and a square type. Also, the exterior method is not particularly limited, and a metal case, mold resin, aluminum laminate film, or the like may be used.

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

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

As before firing jig processing <br/> firing _{jig, Al 2 O 3: 91wt%} , SiO 2: using ceramic Napishtim- consisting 9 wt%.
Li ₂ CO ₃ , NiO, and Co ₃ O ₄ as raw materials for the electrode active material are weighed in a molar ratio of Li: Ni: Co = 1.10: 0.8: 0.2, and dry mixed. Placed in the basket. The soot was heat-treated in oxygen at 700 ° C. for 8 hours. After cooling, the powder in the basket was taken out and used as a pretreatment for the firing jig.
Li is a raw material for manufacturing <br/> electrode active material of lithium transition metal complex oxide _Li 2 _CO 3, NiO, and _Co 3 _{O 4} in a molar ratio: Ni: Co = 1.10: 0.8 : 0. 2 was weighed and mixed with pure water to prepare a slurry. The resulting slurry was spray dried. The dry powder was put into the firing jig subjected to the pretreatment, and heat-treated in oxygen at 700 ° C. for 8 hours to synthesize a lithium transition metal composite oxide.
Preparation of Battery As a positive electrode active material, 85 wt% of the lithium transition metal composite oxide synthesized by the above method, 7.5 wt% of acetylene black as a conductive auxiliary agent and 7.5 wt% of polyvinylidene fluoride as a binder were mixed, and N-methyl-2 -A slurry was prepared by dispersing in pyrrolidone. This was applied onto an aluminum foil having a thickness of 20 μm so as to be 12 mg / cm ² , dried and pressed to prepare an electrode sheet. The electrode sheet was punched out to a diameter of 14 mm to make a positive electrode.
A battery was prepared using metallic lithium as a negative electrode, a polyethylene porous membrane as a separator, and a 3: 7 (volume 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 battery was performed. The charge / discharge performance was evaluated by setting the current value to 200 μA in the voltage range of 3.0V-4.3V.

  Table 1 shows the results of charge / discharge performance evaluation. The initial charge capacity was 206 mAh / g and the initial discharge capacity was as high as 184 mAh / g, and good initial charge / discharge characteristics were obtained.

The firing jig was pretreated in the same manner as in Example 1. However, Li ₂ CO ₃ , NiO, Co ₃ O ₄ , and Mn ₃ O ₄ in a molar ratio of Li: Ni: Co: Mn = 1.10: 0.45: 0.10 are used as compounds for the pretreatment. : Weighed to use 0.45.
Li ₂ CO ₃ , NiO, Co ₃ O ₄ , and Mn ₃ O ₄ used as raw materials for the electrode active material in a molar ratio of Li: Ni: Co: Mn = 1.10: 0.45: 0.10: 0.45 And was mixed with pure water to prepare a slurry. The resulting slurry was spray dried. The dry powder was put in the baking jig subjected to the pretreatment, and heat-treated at 950 ° C. for 20 hours in oxygen to synthesize a lithium transition metal composite oxide.
Using the obtained lithium transition metal composite oxide, a 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 175 mAh / g and the initial discharge capacity was as high as 149 mAh / g, and good initial charge / discharge characteristics were obtained.

The firing jig was pretreated in the same manner as in Example 1. However, Li ₂ CO ₃ , NiO, Co ₃ O ₄ , and Mn ₃ O ₄ in a molar ratio of Li: Ni: Co: Mn = 1.10: 0.33: 0.33 are used as pretreatment compounds. : Weighed and used to 0.33.
Li ₂ CO ₃ , NiO, Co ₃ O ₄ , and Mn ₃ O ₄ used as raw materials for the electrode active material in a molar ratio of Li: Ni: Co: Mn = 1.10: 0.33: 0.33: 0.33 And was mixed with pure water to prepare a slurry. The resulting slurry was spray dried. The dry powder was put in the firing jig subjected to the pretreatment, and heat-treated in the atmosphere at 950 ° C. for 20 hours to synthesize a lithium transition metal composite oxide.
Using the obtained lithium transition metal composite oxide, a 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 175 mAh / g, which was the same as when using a non-heat-treated firing jig, but the initial discharge capacity was as high as 157 mAh / g, and good initial charge / discharge characteristics were obtained. .

The firing jig was pretreated in the same manner as in Example 1. However, Li ₂ CO ₃ , Mn ₃ O ₄ , and Al ₂ O ₃ are used as a compound for the pretreatment so that the molar ratio of Li: Mn: Al = 1.025: 1.962: 0.013. Weighed and used.
Li ₂ CO ₃ , Mn ₃ O ₄ , and Al ₂ O ₃ that are raw materials for the electrode active material are weighed so that the molar ratio is Li: Mn: Al = 1.005: 1.962: 0.013, and pure A slurry was prepared by mixing with water. The resulting slurry was spray dried. The dry powder was put in the firing jig subjected to the pretreatment, and heat-treated in the atmosphere at 850 ° C. for 20 hours to synthesize a lithium transition metal composite oxide.
Using the obtained lithium transition metal composite oxide, a 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. Although the initial discharge capacity was 114 mAh / g, the initial charge capacity was as high as 121 mAh / g, and good initial charge / discharge characteristics were obtained.

Comparative Example 1

A lithium transition metal composite oxide was synthesized in the same manner as in Example 1. However, a firing jig that was not pretreated was used as the firing jig.
Using the obtained lithium transition metal composite oxide, a 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 202 mAh / g, and the initial discharge capacity was 169 mAh / g. The results were inferior to those of Example 1.

Comparative Example 2

A lithium transition metal composite oxide was synthesized in the same manner as in Example 2. However, a firing jig that had not been pretreated was used.
Using the obtained lithium transition metal composite oxide, a 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 172 mAh / g, and the initial discharge capacity was 138 mAh / g. The result was inferior to that of Example 2.

Comparative Example 3

A lithium transition metal composite oxide was synthesized in the same manner as in Example 3. However, a firing jig that had not been pretreated was used.
Using the obtained lithium transition metal composite oxide, a 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 175 mAh / g, and the initial discharge capacity was 156 mAh / g. The results were inferior to those of Example 3.

Comparative Example 4

A lithium transition metal composite oxide was synthesized in the same manner as in Example 4. However, a firing jig that had not been pretreated was used.
Using the obtained lithium transition metal composite oxide, a 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 119 mAh / g, and the initial discharge capacity was 115 mAh / g. The results were inferior to those of Example 4.

Claims (7)

A method for producing a lithium transition metal composite oxide, comprising:
Mixing step of mixing raw materials of the lithium transition metal composite oxide to obtain a mixture;
Firing the mixture to obtain a lithium transition metal composite oxide,
A method for producing a lithium transition metal composite oxide, characterized in that, in the firing step, a firing jig subjected to heat treatment at least once together with a lithium compound is used as a pretreatment. The method for producing a lithium transition metal composite oxide according to claim 1, wherein the lithium transition metal composite oxide contains nickel.   3. The method for producing a lithium transition metal composite oxide according to claim 1, wherein lithium carbonate is used as the lithium compound.   The method for producing a lithium transition metal composite oxide according to any one of claims 1 to 3, wherein the firing jig includes a heat-resistant ceramic as a main component.   5. The method for producing a lithium transition metal composite oxide according to claim 1, wherein a temperature of the heat treatment is 600 ° C. to 1000 ° C. 6.   The lithium transition metal complex oxide manufactured by the manufacturing method in any one of Claims 1-5. A nonaqueous electrolyte secondary battery using the lithium transition metal composite oxide according to claim 6 as an electrode active material.