JP5766761B2 - Non-aqueous electrolyte battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte battery.

Non-aqueous electrolyte batteries using lithium metal, lithium alloys, lithium compounds, or carbonaceous materials as negative electrodes are expected as high energy density batteries and are actively researched and developed. So far, lithium ion batteries including a positive electrode containing LiCoO ₂ or LiMn ₂ O ₄ as an active material and a negative electrode containing a carbonaceous material that occludes and releases lithium have been widely put into practical use for portable devices.

  On the other hand, when it is installed in a car such as an automobile or a train, the constituent materials of the positive electrode and the negative electrode are chemical, electrical, etc. because of storage performance under high temperature environment (60 ° C or higher), cycle performance, and long-term reliability of high output. Materials with excellent chemical stability, strength, and corrosion resistance are required.

  Therefore, from the above problems, high-temperature durability has become a major issue for lithium ion batteries to be mounted in cars and the like. In particular, it is difficult to use in an engine room of an automobile as an alternative to a lead storage battery.

  Various attempts have been made to improve the negative electrode characteristics. Patent Document 1 discloses that a negative electrode in which a specific metal, alloy, or compound is supported on a current collector made of aluminum or an aluminum alloy is used in a nonaqueous electrolyte secondary battery.

On the other hand, in Patent Document 2, primary particles having an average particle size of less than 1 μm of a lithium titanate compound represented by Li _a Ti _3-a O ₄ (0 <a <3) are formed into granules having an average particle size of 5 to 100 μm. It is described that the use of the agglomerated secondary particles as a negative electrode active material suppresses the agglomeration of secondary particles and increases the production yield of large-area negative electrodes for large batteries.

Also, considering the high capacity of the positive electrode material for high energy density of the battery is advanced, lithium cobalt oxide lithium-nickel-cobalt oxide as a positive electrode material in place of _{(LiCoO 2) (LiNi x Co} 1-x O ₂ ) and positive electrode materials such as lithium manganese oxide (LiMnO ₂ ) have been developed for practical use, but there are problems in life characteristics and thermal stability at high temperatures.

JP 2002-42889 A JP 2001-143702 A

  An object of the present invention is to provide a nonaqueous electrolyte battery having a high capacity and excellent storage performance and cycle performance at high temperatures.

The nonaqueous electrolyte battery according to the present invention is Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al and F, and a, b, c and Z are 0 ≦ a ≦ 2.5, 0 <b ≦ 1, 0 ≦ c ≦ 1, 2 ≦ Z ≦ 3), an Fe-containing phosphorus compound having an olivine structure, and the olivine A positive electrode including carbon particles attached to the surface of the Fe-containing phosphorus compound having a structure;
A negative electrode comprising a titanium-containing metal oxide that occludes and releases lithium ions;
And a non-aqueous electrolyte.

The nonaqueous electrolyte battery according to the present invention is Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al and F, and a, b, c and Z are 0 ≦ a ≦ 2.5, 0 <b ≦ 1, 0 ≦ c ≦ 1, 2 ≦ Z ≦ 3) and a positive electrode comprising an olivine-structured Fe-containing phosphorus compound When,
A negative electrode comprising a titanium-containing metal oxide that occludes and releases lithium ions;
And a non-aqueous electrolyte.

Further, the nonaqueous electrolyte battery according to the present invention is Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al and F, and a, b, c and Z is a lithium manganese-containing oxide particle represented by 0 ≦ a ≦ 2.5, 0 <b ≦ 1, 0 ≦ c ≦ 1, 2 ≦ Z ≦ 3) (provided that c = 0 and LiCo _{0. 33} except for _{Mn 0.33 Ni 0.34 O 2),} Li d Mn x Fe 1-x PO 4 of olivine structure (0 ≦ d ≦ 2.5,0 ≦ x <1) a positive electrode including a particle ,
A negative electrode comprising a titanium-containing metal oxide that occludes and releases lithium ions;
And a non-aqueous electrolyte.

  As described above in detail, according to the present invention, it is possible to provide a non-aqueous electrolyte battery having a high capacity and excellent storage performance and cycle performance at high temperatures.

1 is a partially cutaway cross-sectional view showing a prismatic nonaqueous electrolyte secondary battery according to an embodiment of the present invention. Sectional drawing in alignment with the AA of the secondary battery of FIG. The expanded sectional view about the principal part of the secondary battery of FIG.

Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al and F, and a, b, c and Z are 0 ≦ a ≦ 2.5, 0 < The positive electrode active material comprising a lithium manganese-containing oxide represented by b ≦ 1, 0 ≦ c ≦ 1, 2 ≦ Z ≦ 3) is LiNiO ₂ , LiCoO ₂ or spinel type lithium manganese oxide (LiMn ₂ O ₄ ) Although it has the advantage of higher weight energy density compared to ₄ ), if a negative electrode containing a titanium-containing metal oxide that occludes and releases lithium ions is used, a protective film is not formed on the surface of the negative electrode. Progresses and the charge / discharge efficiency of the negative electrode decreases.

  In addition, at the end of discharge, the negative electrode potential of the titanium-containing metal oxide rises slowly, while the positive electrode potential of the lithium manganese-containing oxide falls sharply, so that the battery voltage curve at the end of discharge is regulated by the change in positive electrode potential. . Even if the discharge is cut off when the positive electrode potential drops sharply, the positive electrode is already in an overdischarged state at that time, and the deterioration of the positive electrode proceeds.

  By adding the Fe-containing phosphorus compound having an olivine structure to the lithium manganese-containing oxide having the above composition, the iron component of the aforementioned Fe-containing phosphorus compound is deposited on the surface of the negative electrode containing the titanium-containing metal oxide, Since a protective film is generated on the surface, self-discharge of the negative electrode is suppressed, and charge / discharge efficiency of the negative electrode can be improved. Further, since the positive electrode potential decreases at the end of the discharge stepwise, the discharge potential can be reached by increasing the negative electrode potential, and overdischarge of the positive electrode can be prevented.

  As a result, it is possible to improve the storage performance and charge / discharge cycle performance in a high temperature environment of 60 ° C. or higher while taking advantage of the high weight energy density that is a feature of the lithium manganese-containing oxide. Thereby, for example, even when used in a high temperature environment of 60 ° C. or higher such as an engine room of an automobile, it is possible to realize a non-aqueous electrolyte battery having high capacity and excellent storage performance and cycle performance.

  Hereinafter, the positive electrode, the negative electrode, the nonaqueous electrolyte, and the separator included in the nonaqueous electrolyte battery of the present embodiment will be described.

1) Positive electrode The positive electrode includes a positive electrode current collector and a positive electrode layer that is supported on one or both surfaces of the positive electrode current collector and includes a positive electrode active material, a conductive agent, and a binder.

The positive electrode active material is Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al, and F, and a, b, c, and Z are 0 ≦ a ≦ 2) 0.5, 0 <b ≦ 1, 0 ≦ c ≦ 1, 2 ≦ Z ≦ 3), a first positive electrode active material containing a lithium manganese-containing oxide, and an Fe-containing phosphorus compound having an olivine structure And a second positive electrode active material.

  First, the composition of the first positive electrode active material will be described.

  The amount of Li can be increased or decreased in the range of 0 ≦ a ≦ 2.5 depending on the charge / discharge reaction.

  When the molar ratio b of Mn exceeds 1, the capacity decreases. A more preferable range of b is 0.1 ≦ b ≦ 0.8.

  Of the elements M, Co and Al have the effect of increasing the crystallinity of the lithium manganese-containing oxide. F has an effect of suppressing decomposition of the nonaqueous electrolyte. When the molar ratio c of the element M exceeds 1, the capacity decreases. A more preferable range of c is 0.1 ≦ c ≦ 0.8.

  When the molar ratio Z is less than 2 or exceeds 3, the capacity decreases. A more preferable range of Z is 2.2 ≦ Z ≦ 2.9.

Of the lithium manganese-containing oxides having the above-described composition, LiMn _1-xy Ni _x Co _y O ₂ (0 ≦ x <1, 0 ≦ y <1), LiMn _1-x Ni _x O ₂ (0 ≦ x <1), Li ₂ MnO ₃ , Li ₂ MnO ₃ —LiTO ₂ solid solution (T is at least one element selected from the group consisting of Mn, Ni and Co). Thereby, a high weight energy density of 200 mAh / g or more can be realized.

  The second positive electrode active material will be described.

  The Fe-containing phosphorus compound having an olivine structure desirably has a composition containing Mn. Thereby, the positive electrode potential can be improved. Further, it is allowed to contain metal elements other than Mn and Fe, for example, Co, Ni and the like.

The Fe-containing phosphorus compound having an olivine structure is Li _d Mn _x Fe _1-x PO ₄ (d can be increased or decreased in a range of 0 ≦ d ≦ 2.5 by charge / discharge reaction, x satisfies 0 ≦ x <1) It is desirable that Thereby, the effect which suppresses the overdischarge reaction of a positive electrode and the self-discharge reaction of a negative electrode can be heightened. A more preferable range of the molar ratio x of Mn is 0 <x ≦ 0.8. By setting it within this range, self-discharge at a high temperature is further suppressed. In addition, the battery capacity can be increased.

Since the Fe-containing phosphorus compound having an olivine structure has insulating properties, it is desirable to coat the surface of the particles with a conductive material such as carbon. As the carbon, the surface spacing d ₀₀₂ of (002) plane by X-ray diffraction include the following carbonaceous materials 0.37 nm.

  As a coating method, particles of an olivine-structured Fe-containing phosphorus compound are dispersed in a solution containing a component C, dried, and then fired in a reducing atmosphere at 400 to 800 ° C. to coat the surface of the particles with a conductive material. As a result, a second positive electrode active material is obtained.

  When the weight of the first positive electrode active material is 100% by weight, it is desirable that the weight of the second positive electrode active material is in the range of 1% by weight to 80% by weight. By setting this range, the cycle life performance is greatly improved. A more preferable range is 2% by weight or more and 60% by weight or less, and a further preferable range is 10% by weight or more and 60% by weight or less.

  Examples of the conductive agent include acetylene black, carbon black, graphite, and carbon fiber. In particular, vapor grown carbon fibers having a fiber diameter of 1 μm or less are preferred. By using this carbon fiber, the network of electron conduction inside the positive electrode can be improved, and the output performance of the positive electrode can be greatly improved.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

  The compounding ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 19% by weight of the conductive agent, and 1 to 7% by weight of the binder.

  The positive electrode current collector is preferably formed from an aluminum foil or an aluminum alloy foil. The thickness of the positive electrode current collector is desirably 20 μm or less, and more preferably 15 μm or less.

The positive electrode is produced, for example, by suspending a positive electrode active material, a conductive agent and a binder in a suitable solvent, applying this suspension to one or both sides of the positive electrode current collector, drying, and pressing. The The specific surface area by the BET method of the positive electrode layer is measured in the same manner as the negative electrode and is preferably in the range of 0.1 to ² m ² / g.

2) Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode layer supported on one or both sides of the negative electrode current collector and including a negative electrode active material, a conductive agent, and a binder.

  The negative electrode active material is a titanium-containing metal oxide that absorbs and releases lithium ions. Examples of the titanium-containing metal oxide include lithium titanium-containing composite oxides such as lithium titanium oxide, titanium-based oxides, and the like.

As the lithium-titanium-containing composite oxide, for example, Li _{4 + x} Ti ₅ O ₁₂ having a spinel structure (x may vary within a range of −1 ≦ x ≦ 3 by charge / discharge reaction), Li _{2 + x having} a ramsdelide structure Ti ₃ O ₇ (x may vary within a range of −1 ≦ x ≦ 3 by charge / discharge reaction) _, Li _{1 + x} Ti ₂ O ₄ (x is 0 ≦ x ≦ 1), Li _{1.1 + x} Ti _1.8 O ₄ (x is 0 ≦ x ≦ 1), Li _{1.07 + x} Ti _1.86 O ₄ (x is 0 ≦ x ≦ 1).

Examples of the titanium-based oxide include Li _x TiO ₂ (x is 0 ≦ x), TiO ₂ , Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe. titanium-containing metal composite oxide containing _{{e.g., TiO 2 -P 2 O 5,} TiO 2 -V 2 O 5, TiO 2 -P 2 O 5 -SnO 2, TiO 2 -P 2 O 5 -MeO (Me Is at least one element selected from the group consisting of Cu, Ni and Fe). The titanium-containing metal composite oxide is preferably low in crystallinity and has a microstructure in which the crystal phase and the amorphous phase coexist or exist alone. With such a microstructure, the cycle performance can be greatly improved. As TiO ₂ , anatase-type titanium dioxide, monoclinic titanium dioxide (referred to as so-called TiO ₂ (B)), and low crystalline titanium dioxide having a heat treatment temperature of 300 to 600 ° C. are preferable.

In particular, Li _{4 + x} Ti ₅ O _{12 having} a spinel structure, Li _{2 + x} Ti ₃ O _{7 having a} ramsdelide structure _, anatase-type titanium dioxide, and TiO ₂ (B) are preferable. TiO ₂ (B) is advantageous for increasing the capacity, and Li _{4 + x} Ti ₅ O ₁₂ having a spinel structure is advantageous for extending the life.

The average particle diameter of the primary particles of the negative electrode active material is preferably in the range of 0.001 to 1 μm. By setting the average particle size to 0.001 μm or more, the distribution of the nonaqueous electrolyte can be made uniform, and depletion of the nonaqueous electrolyte at the positive electrode can be suppressed. By setting the average particle size to 1 μm or less, it is possible to suppress a decrease in the porosity of the negative electrode when the negative electrode has a specific surface area of 3 to 50 m ² / g. Also, good performance can be obtained with any particle shape, either granular or fibrous. In the case of a fiber, the fiber diameter is preferably 0.1 μm or less.

The negative electrode active material preferably has an average particle size of 1 μm or less and a specific surface area in the range of ³ to 200 m ² / g according to the BET method by N ₂ adsorption. Thereby, the affinity with the nonaqueous electrolyte of the negative electrode can be further increased.

The specific surface area of the negative electrode is desirably in the range of 3 to 50 m ² / g. Thereby, it is possible to further improve the output performance and charge / discharge cycle performance of the nonaqueous electrolyte battery. A more preferable range of the specific surface area is 5 to 50 m ² / g. Here, the specific surface area of the negative electrode means a surface area per 1 g of the negative electrode layer (excluding the weight of the current collector). Note that the negative electrode layer is a porous layer containing a negative electrode active material, a conductive agent, and a binder carried on a current collector.

  The porosity of the negative electrode (excluding the current collector) is desirably in the range of 20 to 50%. Thereby, it is possible to obtain a negative electrode having excellent affinity between the negative electrode and the non-aqueous electrolyte and a high density. A more preferable range of the porosity is 25 to 40%.

  The negative electrode current collector is preferably an aluminum foil or an aluminum alloy foil. The thickness of the negative electrode current collector is desirably 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99.99 wt% or more. As the aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon is preferable. On the other hand, transition metals such as iron, copper, nickel, and chromium are preferably 100 ppm or less.

  Examples of the conductive agent include acetylene black, carbon black, coke, carbon fiber, graphite, metal compound powder, and metal powder. More preferably, metal powders such as coke, graphite, TiO, TiC, TiN, Al, Ni, Cu, and Fe having a heat treatment temperature of 800 ° C. to 2000 ° C. and an average particle diameter of 10 μm or less can be used.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber, and core-shell binder.

  The mixing ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the negative electrode active material, 1 to 18% by weight of the conductive agent, and 2 to 7% by weight of the binder.

  The negative electrode is produced, for example, by suspending the above-described negative electrode active material, conductive agent, and binder in an appropriate solvent, applying the suspension to a current collector, drying, and applying a heating press. The

3) Separator A separator can be disposed between the positive electrode and the negative electrode. As a separator, a synthetic resin nonwoven fabric, a cellulose nonwoven fabric, a polyethylene porous film, a polypropylene porous film, etc. can be used, for example.

The porosity of the separator is preferably 50% or more. The thickness of the separator is preferably 10 to 100 μm and the density is 0.2 to 0.9 g / cm ³ . Within this range, it is possible to balance mechanical strength and battery resistance reduction, and it is possible to provide a non-aqueous electrolyte battery with high output and few internal short circuits.

  An electrode group is obtained by interposing a separator between the positive electrode and the negative electrode in a spiral manner, laminating, and the like. In the electrode group, the positive electrode layer is a negative electrode layer facing this with the separator interposed therebetween. It is desirable to have a larger area than As a result, the potential of the edge portion of the positive electrode layer can be made equal to the potential of the positive electrode layer facing the negative electrode layer and the separator in the center, and the overcharge of the edge portion of the positive electrode layer is suppressed, and the positive electrode layer And the reaction with the non-aqueous electrolyte are suppressed. This makes it possible to improve the charge / discharge cycle life performance at high temperatures.

  The ratio (Sp / Sn) of the area (Sp) of the positive electrode layer to the area (Sn) of the negative electrode layer is preferably in the range of 0.85 to 0.999. The battery capacity is improved by setting the area ratio (Sp / Sn) to 0.85 or more. Further, by setting the area ratio (Sp / Sn) to 0.999 or less, gas generation from the negative electrode during high-temperature charge storage or high-temperature float charge can be suppressed. A more preferred range is from 0.95 to 0.99. The ratio (Lp / Ln) of the positive electrode width (Lp) to the negative electrode width (Ln) is preferably in the range of 0.9 to 0.99.

4) Nonaqueous electrolyte As the nonaqueous electrolyte, a liquid organic electrolyte prepared by dissolving an electrolyte in an organic solvent, a gel organic electrolyte obtained by combining a liquid organic solvent and a polymer material, or a lithium salt electrolyte And a solid non-aqueous electrolyte in which a polymer material is combined. Moreover, you may use the normal temperature molten salt (ionic melt) containing lithium ion as a non-aqueous electrolyte. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.

  The liquid organic electrolyte is prepared by dissolving the electrolyte in an organic solvent at a concentration of 0.5 to 2.5 mol / L.

Examples of the electrolyte include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Li (CF ₃ SO ₂ ). ₃ C, LiBF ₂ C ₂ O ₄ , LiB [(OCO) ₂ ] _{2 and the} like. The type of electrolyte used can be one type or two or more types. Among them, preferably comprises a lithium tetrafluoroborate (LiBF _4). Thereby, the chemical stability of the organic solvent is increased, the film resistance on the negative electrode can be reduced, and the low temperature performance and cycle life performance can be greatly improved.

  Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC), chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC), dimethoxyethane ( Examples thereof include chain ethers such as DME) and dietoethane (DEE), cyclic ethers such as tetrahydrofuran (THF) and dioxolane (DOX), γ-butyrolactone (GBL), acetonitrile (AN) and sulfolane (SL). These organic solvents can be used alone or in the form of a mixture of two or more. In particular, one or more first solvents selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC) and γ-butyrolactone (GBL), diethyl carbonate (DEC), methyl ethyl carbonate (MEC) and dimethyl Since the non-aqueous solvent containing the second solvent composed of one or more chain carbonates selected from the group consisting of carbonate (DMC) has high stability at a high potential of 4.4 to 4.5 V, the cycle It is possible to improve the life performance. The ratio of the second solvent is preferably 70% by volume or more. The non-aqueous solvent containing EC and DEC is excellent in stability at a high potential of 4.4 to 4.5 V, and can suppress oxidative decomposition of the non-aqueous electrolyte.

  Hereinafter, the nonaqueous electrolyte containing a room temperature molten salt will be described.

  The room temperature molten salt (ionic melt) is preferably composed of lithium ions, organic cations and organic anions. The room temperature molten salt is preferably liquid at room temperature or lower.

  The room temperature molten salt refers to a salt that is at least partially in a liquid state at room temperature, and the room temperature refers to a temperature range in which a power supply is assumed to normally operate. The temperature range in which the power supply is assumed to normally operate has an upper limit of about 120 ° C. and in some cases about 60 ° C., and a lower limit of about −40 ° C. and in some cases about −20 ° C. Especially, the range of -20 degreeC or more and 60 degrees C or less is suitable.

  For room temperature molten salts containing lithium ions, it is desirable to use an ionic melt composed of lithium ions, organic cations and anions. The ionic melt is preferably in a liquid state even at room temperature or lower.

Examples of the organic cation include alkyl imidazolium ions and quaternary ammonium ions having a skeleton represented by the following formula (1).

As the alkyl imidazolium ion, a dialkyl imidazolium ion, a trialkyl imidazolium ion, a tetraalkyl imidazolium ion and the like are preferable. As the dialkylimidazolium, 1-methyl-3-ethylimidazolium ion (MEI ⁺ ) is preferable. As the trialkylimidazolium ion, 1,2-diethyl-3-propylimidazolium ion (DMPI ⁺ ) is preferable. As the tetraalkylimidazolium ion, 1,2-diethyl-3,4 (5) -dimethylimidazolium ion is preferable.

  As the quaternary ammonium ion, a tetraalkylammonium ion or a cyclic ammonium ion is preferable. As the tetraalkylammonium ion, dimethylethylmethoxyethylammonium ion, dimethylethylmethoxymethylammonium ion, dimethylethylethoxyethylammonium ion, and trimethylpropylammonium ion are preferable.

  By using the alkylimidazolium ion or quaternary ammonium ion (particularly tetraalkylammonium ion), the melting point can be made 100 ° C. or lower, more preferably 20 ° C. or lower. Furthermore, the reactivity with the negative electrode can be lowered.

  The concentration of lithium ions is preferably 20 mol% or less. A more preferred range is in the range of 1 to 10 mol%. By setting it within the above range, a liquid room temperature molten salt can be easily formed even at a low temperature of 20 ° C. or lower. Further, the viscosity can be lowered even at room temperature or lower, and the ionic conductivity can be increased.

As anions, BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , (FSO ₂ ) ₂ N ⁻ , N It is preferable that at least one anion selected from (CF ₃ SO ₂ ) ₂ ⁻ , N (C ₂ F ₅ SO ₂ ) ₂ ⁻ , (CF ₃ SO ₂ ) ₃ C ^{− and the} like coexists. By coexisting a plurality of anions, a room temperature molten salt having a melting point of 20 ° C. or lower can be easily formed. More preferable anions include BF ₄ ⁻ , (FSO ₂ ) ₂ N ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , CH ₃ COO ⁻ , CO ₃ ²⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , N (C ₂ F ₅ SO ₂ ) ₂ ⁻ and (CF ₃ SO ₂ ) ₃ C ⁻ . These anions make it easier to form a room temperature molten salt at 0 ° C. or lower.

5) Container A metal container or a laminate film container can be used as a container for accommodating the positive electrode, the negative electrode, and the nonaqueous electrolyte.

  As the metal container, a metal can made of aluminum, aluminum alloy, iron, stainless steel or the like having a square or cylindrical shape can be used. Further, the plate thickness of the container is desirably 0.5 mm or less, and a more preferable range is 0.3 mm or less.

  Examples of the laminate film include a multilayer film in which an aluminum foil is covered with a resin film. As the resin, polymers such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used. The thickness of the laminate film is preferably 0.2 mm or less. The purity of the aluminum foil is preferably 99.5 wt% or more.

  The metal can made of an aluminum alloy is preferably an alloy containing an element such as manganese, magnesium, zinc, or silicon and having an aluminum purity of 99.8 wt% or less. The strength of the metal can made of an aluminum alloy is dramatically increased, and thus the thickness of the can can be reduced. As a result, a thin, lightweight, high output and excellent heat dissipation battery can be realized.

  The present invention can be applied to various forms of nonaqueous electrolyte batteries such as a cylindrical shape, a thin shape, a square shape, and a coin shape. One embodiment of a nonaqueous electrolyte battery is shown in FIGS. As shown in FIG. 1, the electrode group 1 is housed in a rectangular cylindrical metal container 2. The electrode group 1 has a spiral shape in which a positive electrode 3 (positive electrode layer 3b, positive electrode current collector 3a) and a negative electrode 4 (negative electrode layer 4b, negative electrode current collector 4a) are flattened with a separator 5 interposed therebetween. It has a wound structure. The electrode group 1 is produced, for example, by winding the positive electrode 3 and the negative electrode 4 in a spiral shape with a separator 5 interposed therebetween, and then applying a heat press.

  As shown in FIG. 3, the positive electrode 3 has a structure in which a positive electrode layer 3b is formed on one side or both sides of a positive electrode current collector 3a. On the other hand, the negative electrode 4 has a structure in which a negative electrode layer 4b is formed on one side or both sides of a negative electrode current collector 4a. A nonaqueous electrolyte (not shown) is held in the electrode group 1. As shown in FIG. 2, a plurality of strip-like positive electrode leads 6 are drawn from the end face of the electrode group 1. The positive electrode lead 6 is electrically connected to the end of the positive electrode 3 as shown in FIG. Similarly, as shown in FIG. 1, the strip-like negative electrode lead 7 is electrically connected to the end of the negative electrode 4. Although not shown here, a plurality of negative electrode leads 7 are also drawn from the same end face of the electrode group 1. The plurality of positive electrode leads 6 are electrically connected to the positive electrode conductive tab 8 in a bundled state. The positive electrode lead 6 and the positive electrode conductive tab 8 constitute a positive electrode terminal. The negative electrode lead 7 is connected to the negative electrode conductive tab 9 in a bundled state. The negative electrode lead 7 and the negative electrode conductive tab 9 constitute a negative electrode terminal. The metal sealing plate 10 is fixed to the opening of the metal container 2 by welding or the like. The positive electrode conductive tab 8 and the negative electrode conductive tab 9 are each drawn out from an extraction hole provided in the sealing plate 10. The inner peripheral surface of each extraction hole of the sealing plate 10 is covered with an insulating member 11 in order to avoid a short circuit due to contact with the positive electrode conductive tab 8 and the negative electrode conductive tab 9.

  Hereinafter, examples of the present invention will be described in detail with reference to the drawings described above, but the present invention is not limited to the examples described below.

Example 1
As the first positive electrode active material, lithium manganese nickel oxide (LiMn _0.2 Ni _0.8 O ₂ ) particles were prepared. Further, as the second positive electrode active material, lithium phosphate having an olivine structure having an average particle size of 0.1 μm of primary particles having carbon particles (average particle size of 0.005 μm) attached to the surface (adhesion amount 0.1 wt%). Iron (LiFePO ₄ ) particles were prepared. 10% by weight of the second positive electrode active material is added to 80% by weight of the first positive electrode active material, and 5% by weight of PVdF as a conductive agent and 5% by weight of PVdF with respect to the whole positive electrode are added thereto as a conductive agent. A slurry was prepared by mixing and dispersing in an n-methylpyrrolidone (NMP) solvent. A slurry is applied to both surfaces of a 15 μm thick aluminum alloy foil (99% purity), dried, and subjected to a pressing process. The positive electrode layer has a positive electrode layer thickness of 43 μm and an electrode density of 2.2 g / cm ³ . Was made. The specific surface area of the positive electrode layer was 5 m ² / g. The addition ratio of the second positive electrode active material when the first positive electrode active material was 100% by weight was 12.5% by weight.

TiO ₂ (B) powder having an average primary particle size of 1 μm, a BET specific surface area of 20 m ² / g, and a Li storage potential of about 1.5 V (vs. Li / Li ⁺ ), and an average particle size of 6 μm as a conductive agent. Graphite powder and PVdF as a binder were blended in a weight ratio of 90: 8: 2, dispersed in n-methylpyrrolidone (NMP) solvent, stirred at a rotational speed of 1000 rpm using a ball mill. A slurry was prepared using stirring under conditions of 2 hours. The obtained slurry was applied to an aluminum alloy foil having a thickness of 15 μm (purity 99.3%), dried, and subjected to a heat press process, whereby the thickness of the negative electrode layer on one side was 59 μm and the electrode density was 2.2 g. A negative electrode of / cm ³ was produced. The negative electrode porosity excluding the current collector was 35%. Moreover, the BET specific surface area (surface area per 1 g of negative electrode layer) of the negative electrode layer was 15 m ² / g.

  A method for measuring particles of the negative electrode active material is shown below.

  To measure the particles of the negative electrode active material, use a laser diffraction distribution analyzer (Shimadzu SALD-300). First, add approximately 0.1 g of the sample, a surfactant, and 1 to 2 mL of distilled water to a beaker. After stirring, the mixture was poured into a stirred water tank, and the light intensity distribution was measured 64 times at intervals of 2 seconds, and the particle size distribution data was analyzed.

Electrode active material, and a BET specific surface area by N ₂ adsorption of the negative electrode was measured under the following conditions.

2 g of a negative electrode active material 1 g of powder or 2 × 2 cm ² negative electrode was cut out and used as a sample. A BET specific surface area measuring device manufactured by Yuasa Ionics was used, and nitrogen gas was used as the adsorption gas.

  The porosity of the negative electrode is compared with the negative electrode layer volume when the porosity is 0%, and the increase from the negative electrode layer volume when the porosity is 0% is regarded as the void volume. Calculated. The volume of the negative electrode layer is the sum of the volumes of the negative electrode layers on both sides when the negative electrode layers are formed on both sides of the current collector.

  On the other hand, the surface of the positive electrode was closely adhered and covered with a separator made of a polyethylene porous film (thickness 20 μm, porosity 65%), and the negative electrode was layered thereon, and these were wound in a spiral shape to produce an electrode group. The ratio of the area of the positive electrode layer to the area of the negative electrode layer (Sp / Sn) was 0.98. Further, the negative electrode layer was arranged to cover the positive electrode layer with a separator interposed therebetween. The electrode width of the positive electrode layer was 50 mm, the electrode width of the negative electrode layer was 51 mm, and the length ratio (Lp / Ln) was 0.98.

  Further, this electrode group was further pressed and formed into a flat shape. The electrode group was housed in a thin metal can container made of an aluminum alloy (Al purity 99%) having a thickness of 0.25 mm.

On the other hand, lithium tetrafluoroborate (LiBF ₄ ) as a lithium salt is added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 2 as an organic solvent. A liquid organic electrolyte (non-aqueous electrolyte) was prepared by dissolving. This liquid organic electrolyte was poured into the electrode group in the container, and a thin secondary battery having the structure shown in FIG. 1 and having a thickness of 13 mm, a width of 62 mm, and a height of 95 mm was produced.

(Examples 2 to 4)
A thin secondary battery was produced in the same manner as described in Example 1 except that the composition of the lithium manganese-containing oxide as the first positive electrode active material was changed as shown in Table 1 below. .

(Example 5)
The composition of the lithium manganese-containing oxide as the first positive electrode active material is changed as shown in Table 1 below, and the composition of olivine-structured lithium iron phosphate particles to which carbon fine particles are attached is shown in Table 1 below. A thin secondary battery was produced in the same manner as described in Example 1 except that the above changes were made.

(Examples 6 and 7)
Except for changing the addition ratio of the second positive electrode active material when the first positive electrode active material is 100% by weight as shown in Table 1 below, the same as described in Example 1 above. A thin secondary battery was produced.

(Example 8)
Explained in Example 1 above, except that as the negative electrode active material, the average particle size of the primary particles is 0.6 μm, the BET specific surface area is 9 m ² / g, and Li ₄ Ti ₅ O ₁₂ having a spinel structure is used. In the same manner, a thin secondary battery was produced.

Example 9
A thin secondary battery was fabricated in the same manner as described in Example 8 except that the composition of the olivine-structured lithium iron phosphate particles was changed as shown in Table 1 below.

(Example 10)
The composition of the olivine-structured lithium iron phosphate particles is changed as shown in Table 1 below, and the addition ratio of the second cathode active material when the first cathode active material is 100% by weight is shown in Table 1 below. A thin secondary battery was fabricated in the same manner as described in Example 8 except that the changes were made as shown.

(Examples 11 and 12)
A thin secondary battery was produced in the same manner as described in Example 1 except that the composition of the lithium manganese-containing oxide as the first positive electrode active material was changed as shown in Table 1 below. .

(Example 13)
Explained in Example 1 described above, except that as the negative electrode active material, the average particle diameter of the primary particles is 0.5 μm, the BET specific surface area is 12 m ² / g, and Li ₂ Ti ₃ O ₇ having a ramsdelide structure is used. In the same manner, a thin secondary battery was produced.

(Example 14)
The negative electrode active material is the same as that described in Example 1 except that an average particle diameter of primary particles is 0.5 μm, a BET specific surface area is 12 m ² / g, and anatase TiO ₂ is used. A thin secondary battery was produced.

(Comparative Example 1)
A thin secondary battery was produced in the same manner as described in Example 8 except that the second positive electrode active material was not used.

(Comparative Example 2)
A thin secondary battery was fabricated in the same manner as described in Comparative Example 1 except that the composition of the first positive electrode active material was changed to that shown in Table 2.

(Comparative Examples 3 and 4)
A thin secondary battery was fabricated in the same manner as described in Comparative Example 1 except that the materials shown in Table 2 were used as the first positive electrode active material and the negative electrode active material.

(Comparative Example 5)
A thin secondary battery was fabricated in the same manner as described in Comparative Example 1 except that the composition of the first positive electrode active material was changed to that shown in Table 2.

(Comparative Example 6)
A thin secondary battery was fabricated in the same manner as described in Example 8 except that the first positive electrode active material was not used.

  Among the obtained secondary batteries of Examples 1 to 14 and Comparative Examples 1 to 2, 5 and 6, after charging in 30 minutes to 2.8 V at a constant current of 20 A at 25 ° C., 3 A to 1.2 V at 3 A The discharge capacity when discharged was measured. On the other hand, Comparative Examples 3-4 measured the discharge capacity when it discharged by 3A to 3V after charging in 30 minutes to 4.2V at 25 degreeC.

  For each secondary battery, as a high-temperature storage test, the remaining capacity and the recovery capacity after being fully charged at 25 ° C. and stored at 60 ° C. for one month were measured at 25 ° C.

  The remaining capacity was measured by the following method.

  For the secondary batteries of Examples 1 to 14 and Comparative Examples 1 to 2, 5 and 6 after storage, the discharge capacity when discharged at 3 A to 1.2 V was defined as the remaining capacity. On the other hand, in Comparative Examples 3 to 4, the discharge capacity when discharged at 3 A up to 3 V was defined as the remaining capacity.

  The recovery capacity was measured by the following method.

  After measuring the remaining capacity, the secondary batteries of Examples 1 to 14 and Comparative Examples 1 to 2, 5, and 6 were charged at a constant current of 20 A at 25 ° C. to 2.8 V in 30 minutes, and then to 1.2 V. The discharge capacity when discharged at 3 A was taken as the recovery capacity. On the other hand, after measuring the remaining capacity, in Comparative Examples 3 to 4, after charging at 25 ° C. to 4.2 V in 30 minutes, the discharge capacity when discharging to 3 V at 3 A was taken as the recovery capacity.

  Based on the discharge capacity before storage, the remaining capacity ratio (%) and the recovery capacity ratio (%) were calculated.

  As a high-temperature cycle life evaluation at 60 ° C., a cycle from a charge rate of 100% to 0% was repeated, and the cycle number with a capacity of 80% was defined as the cycle life.

The measurement results are shown in Tables 3 and 4 below.

As is apparent from Tables 1 to 4, Examples 1 to 14 are superior to Comparative Examples 1 to 6 in the remaining capacity after storage at 60 ° C., the recovery capacity, and the high-temperature cycle life performance. As for the high-temperature cycle life performance, it can be seen from the comparison between Example 1 and Example 8 that Example 8 using spinel-structured Li ₄ Ti ₅ O ₁₂ as the negative electrode active material is superior. As for the capacity, by comparison of Examples 1,8,13,14, it can be seen that the high capacity is obtained in Example 14 using the anatase type TiO ₂ in the negative electrode active material.

On the other hand, Comparative Example 1 not using the second positive electrode active material, Comparative Example 6 not using the first positive electrode active material, LiNiO ₂ , LiCoO _2, or spinel type lithium manganese oxide (LiMn ₂ O ₄ ) In Comparative Examples 2, 3, and 5 used for the materials, any of the capacity, remaining capacity, recovery capacity, and high-temperature cycle life performance was inferior to the Examples. Further, when a carbonaceous material was used as the negative electrode active material as in Comparative Examples 3 and 4, gas was generated due to the decomposition of the solvent, so that the high-temperature cycle life performance was remarkably lowered.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1] Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al and F, and a, b, c and Z are 0 ≦ a ≦ 2.5. , 0 <b ≦ 1,0 ≦ c ≦ 1,2 ≦ Z ≦ 3 and a lithium manganese-containing oxide particles represented by the meet), the olivine structure _{Li d Mn x Fe 1-x} PO 4 (0 ≦ d ≦ 2.5, 0 ≦ x <1) A nonaqueous electrolyte battery comprising: a positive electrode including particles; a negative electrode including a titanium-containing metal oxide that absorbs and releases lithium ions; and a nonaqueous electrolyte.
[2] The titanium-containing metal oxide may be Li _{4 + x} Ti ₅ O ₁₂ (−1 ≦ x ≦ 3), Li _{2 + x} Ti ₃ O ₇ (−1 ≦ x ≦ 3) or monoclinic system. The nonaqueous electrolyte battery according to [1], comprising titanium dioxide.
[3] The nonaqueous electrolyte battery according to [1] or [2], wherein the nonaqueous electrolyte contains ethylene carbonate and diethyl carbonate.
[4] The nonaqueous electrolyte according to any one of [1] to [3], wherein the positive electrode further includes carbon particles attached to the surface of the Li _d Mn _x Fe _1-x PO ₄ particles. battery.
[5] When the lithium manganese-containing oxide particles are 100% by weight, the Li _d Mn _x Fe _1-x PO ₄ particles have a weight in the range of 1% by weight to 80% by weight. The nonaqueous electrolyte battery according to any one of claims [1] to [4].

  DESCRIPTION OF SYMBOLS 1 ... Electrode group, 2 ... Container, 3 ... Positive electrode, 3a ... Positive electrode collector, 3b ... Positive electrode layer, 4 ... Negative electrode, 4a ... Negative electrode collector, 4b ... Negative electrode layer, 5 ... Separator, 6 ... Positive electrode lead, 7 ... Negative electrode lead, 8 ... Positive electrode conductive tab, 9 ... Negative electrode conductive tab, 10 ... Sealing plate, 11 ... Insulating member.

Claims (6)

Li _a Mn _b M _c O _Z (M is one or more elements selected from the group consisting of Ni, Co, Al and F, and a, b, c and Z are 0 ≦ a ≦ 2.5, 0 < b ≦ 1,0 ≦ c ≦ 1,2 ≦ Z ≦ 3 meet) represented by lithium manganese-containing oxide particles (where the c = 0 and _LiCo 0.33 _Mn 0.33 _{Ni 0.34} O ₂ and _{excluding), Li d Mn x Fe 1} -x PO 4 of olivine structure (0 ≦ d ≦ 2.5,0 ≦ x <1) a positive electrode including a particle,
A negative electrode comprising a titanium-containing metal oxide that occludes and releases lithium ions;
A non-aqueous electrolyte battery comprising a non-aqueous electrolyte. The titanium-containing metal oxide includes Li _{4 + x} Ti ₅ O ₁₂ (−1 ≦ x ≦ 3), Li _{2 + x} Ti ₃ O ₇ (−1 ≦ x ≦ 3) or monoclinic titanium dioxide. The nonaqueous electrolyte battery according to claim 1.   The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte includes ethylene carbonate and diethyl carbonate. The positive electrode, the _{Li d Mn x Fe 1-x} PO 4 nonaqueous electrolyte battery according to claim 1, characterized in that the particles further comprise carbon particles attached to the surface of the. Upon the lithium manganese-containing oxide particles is 100% by weight, claims wherein _{Li d Mn x Fe 1-x} PO 4 by weight of the particles 1 wt% or more, characterized in that it is in the range of 80 wt% or less The nonaqueous electrolyte battery according to any one of 1 to 4. The non-aqueous electrolyte battery according to claim 1, wherein the titanium-containing metal oxide is monoclinic titanium dioxide.