JP6585141B2 - Non-aqueous electrolyte battery - Google Patents

Description

  Embodiments described herein relate generally to a non-aqueous electrolyte battery negative electrode and a non-aqueous electrolyte battery.

  The battery includes a negative electrode capacity regulation design in which the negative electrode capacity is smaller than the positive electrode capacity, and a positive electrode capacity restriction design in which the positive electrode capacity is smaller than the negative electrode capacity. In a battery using lithium titanate for the negative electrode, the negative electrode capacity regulation design is advantageous in order to realize excellent cycle performance and safety. In addition, when lithium titanate is used as the negative electrode active material, it is known that overcharge cycle performance is improved when aluminum or an aluminum alloy is used as the negative electrode current collector.

JP 2002-42889 A

H.F.Xiang, X. Zhang, Q.Y.Jin, C.P.Zhang, C.H.Chen, X.W.Ge, J. Power Sources, 183, 355-360 (2008)

  The problem to be solved by the present invention is to provide a nonaqueous electrolyte battery excellent in charge / discharge cycle performance and safety performance, and a negative electrode used in the battery.

According to the embodiment, a current collector made of aluminum or an aluminum alloy, and a carbon material having a specific surface area of 10 to 1000 m ² / g as a negative electrode active material and a lithium titanium composite oxide as a negative electrode active material. A negative electrode including a negative electrode material layer,
A positive electrode including a positive electrode active material;
A non-aqueous electrolyte containing a non-aqueous solvent in which 20 to 80% by volume is propylene carbonate,
Satisfy the following formulas (1) and (2),
10Sa ≦ Se ≦ 500Sa (1)
Sa is an area (m ² ) of the negative electrode, Se is a surface area (m ² ) of the conductive agent, and the area of the negative electrode is a value obtained by multiplying the width and length of the negative electrode material layer,
1.02Ca ≦ Cc ≦ 1.50Ca (2)
The Ca is the electric capacity (Ah) of the negative electrode when charged to Li / Li ⁺ to 1.0 V, and the Cc is the charge when charged to Li / Li ⁺ to 4.2 V. The electrical capacity (Ah) of the positive electrode,
At a charging current in the range of 1 × 10 ^{−4 to} 2C rate, the lithium occlusion / release reaction of the negative electrode occurs within a range of 1.2 to 2.5 V with respect to Li / Li ⁺ , and the reduction of the nonaqueous electrolyte The plateau potential of the decomposition reaction is in the range of 0.55 to 1.1 V with respect to Li / Li ⁺ , and the plateau potential of the Li—Al alloying reaction is 0.2 to 0.5 V with respect to Li / Li ⁺ . A non-aqueous electrolyte battery that is within range is provided.

The disassembled perspective view of the nonaqueous electrolyte battery which concerns on embodiment. The partial expansion perspective view of the electrode group used for the nonaqueous electrolyte battery of FIG. The characteristic view which shows the change at the time of charge of the positive electrode potential of the battery of Example 1, and a negative electrode potential. The characteristic view which shows the change at the time of charge of the positive electrode potential of the battery of Example 5, and a negative electrode potential.

  The inventors use lithium titanate as the negative electrode active material of the non-aqueous electrolyte battery, use aluminum or an aluminum alloy as the negative electrode current collector, and have a negative electrode capacity regulation design in which the negative electrode capacity is smaller than the positive electrode capacity. Although excellent cycle performance can be obtained, if the battery falls into an overcharged state, a negative electrode current collector becomes brittle because a lithium aluminum alloy is formed on the negative electrode current collector, and the negative electrode cannot maintain its shape. It was found that the thermal stability was also lowered.

Further, the inventors have 1 × 10 ⁻⁴ among negative electrodes including a negative electrode current collector made of aluminum or an aluminum alloy and a negative electrode material layer formed on the negative electrode current collector and including a negative electrode active material and a conductive agent. At a charging current in the range of ˜2C rate, the occlusion / release reaction potential of lithium is in the range of 1.2 to 2.5 V with respect to Li / Li ⁺ , and the reductive decomposition reaction potential of the nonaqueous electrolyte is changed to Li / Li ⁺ . On the other hand, by using the negative electrode of the embodiment in which the Li—Al alloying reaction potential is in the range of 0.2 to 0.5 V with respect to Li / Li ^{+ in} the range of 0.55 to 1.1 V, We have determined that a non-aqueous electrolyte battery excellent in both charge / discharge cycle performance and safety can be obtained.

Here, the reason why the charging current is in the range of 1 × 10 ^{−4 to} 2C rate is as follows. When the charging current is smaller than the 1 × 10 ⁻⁴ C rate, the Joule heat generation until reaching the overcharged state is small and the temperature rise of the battery itself is small, so that the effect of this embodiment is difficult to obtain. On the other hand, when the charging current is larger than the 2C rate, the effect of this embodiment is obtained because the overvoltage during charging is large and the reductive decomposition reaction of the nonaqueous electrolyte is less likely to occur preferentially than the Li-Al alloying reaction. Hateful.

Further, the reason for the lithium occlusion / release reaction potential to be in the range of 1.2 to 2.5 V with respect to Li / Li ⁺ is as follows. If the occlusion-release reaction potential is lower than 1.2 V, the lithium occlusion-release reaction takes precedence over the non-aqueous electrolyte reductive decomposition reaction during overcharging, so that the reductive decomposition reaction of the non-aqueous electrolyte does not occur. The negative electrode potential reaches the Li—Al alloying reaction potential. Further, if the occlusion-release reaction potential is nobler than 2.5V, a high battery voltage cannot be obtained.

If the reductive decomposition reaction potential of the nonaqueous electrolyte is nobler than 1.1 V with respect to Li / Li ⁺ , the reductive decomposition of the nonaqueous electrolyte occurs even in the overcharged state, so the charge / discharge cycle performance decreases. To do. If the reductive decomposition reaction potential is lower than 0.55 V, the negative electrode potential reaches the Li—Al alloying reaction potential when the reductive decomposition reaction occurs during overcharge. The reason why the Li—Al alloying reaction potential is in the range of 0.2 to 0.5 V with respect to Li / Li ⁺ is that a negative electrode current collector made of aluminum or aluminum alloy is used.

For example, in a nonaqueous electrolyte battery (hereinafter referred to as battery A) using lithium titanate as a negative electrode active material and lithium cobaltate as a positive electrode active material and having a negative electrode capacity regulation design, the negative electrode potential is 1.0 V (vs. Li). / Li ^+), the positive electrode potential is charged until it reaches 4.3V (vs.Li/Li ^+), charging voltage of the battery a is 3.3V. According to the industrial lithium secondary battery safety test (single battery and battery system) (SBA S 1101) established by the Japan Battery Association, the battery voltage reached 120% of the upper limit charging voltage in the overcharge test. At that time, constant current charging is stopped. Therefore, the upper limit voltage during the overcharge test of battery A is 3.96V. When Al or an Al alloy is used for the negative electrode current collector of the battery A, if the battery voltage during the overcharge test is 3.96 V, the negative electrode potential is about 0.4 V (vs. Li ^/ Li ⁺ ) and the positive electrode Since the potential is in the vicinity of about 4.4 V (vs. Li / Li ⁺ ), the Li—Al alloying reaction proceeds in the negative electrode current collector.

According to the negative electrode of the embodiment, when the battery voltage during the overcharge test is 3.96 V, the negative electrode potential is 0.55 to 1.1 V (vs. Li / Li ⁺ ) of the reductive decomposition reaction potential of the nonaqueous electrolyte. The positive electrode potential is in the range of about 4.5 to 4.9 V (vs. Li / Li ⁺ ). As a result, in the negative electrode, the reductive decomposition reaction of the nonaqueous electrolyte occurs in preference to the Li-Al alloying reaction, so that the Li-Al alloy formation reaction in the negative electrode current collector is suppressed, and high heat is generated even during overcharge. Stability can be maintained. Further, overcharge can be reliably detected by the value of the positive electrode potential. Thereby, the outstanding safety performance can be obtained. Furthermore, since the negative electrode current collector does not become brittle and the shape of the negative electrode can be maintained, excellent charge / discharge cycle performance can also be obtained.

The negative electrode of the embodiment preferably satisfies the following formula (1) and uses a carbon material having a specific surface area of 10 to 1000 m ² / g as the conductive agent. Examples of the carbon material include carbon black, graphite (graphite), graphene, fullerenes, coke and the like. Among these, carbon black and graphite are preferable, and examples of the carbon black include acetylene black, ketjen black, and furnace black.

10Sa ≦ Se ≦ 500Sa (1)
Here, Sa is the area (m ² ) of the negative electrode, and Se is the surface area (m ² ) of the conductive agent. A conductive agent made of a carbon material having a specific surface area of 10 to 1000 m ² / g promotes a reductive decomposition reaction of a nonaqueous electrolyte that occurs at a negative electrode potential in the range of 0.55 to 0.9 V with respect to Li / Li ⁺ . Can do. By setting the surface area Se of the conductive agent to 10 Sa (m ² ) or more, the reductive decomposition reaction of the nonaqueous electrolyte can be further promoted. However, when the surface area Se of the conductive agent exceeds 500 Sa (m ² ), the side reaction on the surface of the nonaqueous electrolyte and the negative electrode outside the range of 0.55 to 1.1 V with respect to Li / Li ⁺ increases, and the battery There is a concern that the resistance will increase. Therefore, by using a carbon material having a negative electrode satisfying the formula (1) and having a specific surface area of 10 to 1000 m ² / g as the conductive agent, it is outside the range of 0.55 to 1.1 V with respect to Li / Li ⁺ . It is possible to promote the reductive decomposition reaction of the nonaqueous electrolyte that occurs in the range of 0.55 to 1.1 V with respect to Li / Li ⁺ while suppressing side reactions on the nonaqueous electrolyte and the negative electrode surface. Since the negative electrode potential is kept substantially constant during reductive decomposition, the positive electrode potential rises, and overcharge can be reliably detected by the increase in the positive electrode potential.

  The negative electrode of the embodiment can be produced as follows. The negative electrode includes a current collector and a negative electrode material layer (negative electrode active material-containing layer) that is supported on one or both surfaces of the current collector and includes a negative electrode active material, a conductive agent, and a binder. In this negative electrode, for example, a conductive agent and a binder are added to a powdered negative electrode active material, these are suspended in an appropriate solvent, and this suspension (slurry) is applied to a current collector, dried, pressed Then, it is manufactured by forming a strip electrode.

  An aluminum foil or an aluminum alloy foil is used for the current collector. The aluminum foil and aluminum alloy foil desirably have an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and still more preferably 5 μm or less. By setting the average crystal grain size of the aluminum foil or aluminum alloy foil to 50 μm or less, the strength of the aluminum foil or aluminum alloy foil can be dramatically increased. For this reason, it is possible to increase the negative electrode capacity by increasing the pressure during pressing to increase the density of the negative electrode material layer. Further, it is possible to prevent the current collector from being dissolved and corroded in an overdischarge cycle under a high temperature environment (40 ° C. or higher). For this reason, an increase in negative electrode impedance can be suppressed. Furthermore, output performance, rapid charge, and charge / discharge cycle performance can also be improved.

The average crystal grain size is determined as follows. The structure of the current collector surface is observed with an optical microscope, and the number n of crystal grains existing within 1 mm × 1 mm is determined. Using this n, the average crystal grain area S is determined from S = 1 × 10 ⁶ / n (μm ² ). The average crystal particle diameter d (μm) is calculated from the obtained S value by the following formula (A).

d = 2 (S / π) ^1/2 (A)
The average crystal grain size of the aluminum foil or aluminum alloy foil changes under complex influences from a plurality of factors such as material structure, impurities, processing conditions, heat treatment history, and annealing conditions. The crystal grain size can be adjusted by combining the above factors in the production process of the current collector.

  The thickness of the current collector is desirably 20 μm or less, more preferably 15 μm or less. The aluminum foil preferably has a purity of 99% by mass or more. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. Transition metals such as iron, copper, nickel and chromium contained as alloy components are preferably 1% by mass or less.

By using the aluminum foil or aluminum alloy foil as described above for the current collector, the Li—Al alloying reaction proceeds in a range of 0.2 to 0.5 V with respect to Li / Li ⁺ .

As the negative electrode active material, a material in which a lithium occlusion / release reaction proceeds in a range of 1.2 to 2.5 V with respect to Li / Li ⁺ can be used. For example, lithium titanium complex oxide is mentioned. The lithium titanium composite oxide is, for example, a spinel type lithium titanate represented by Li _{4 + x} Ti ₅ O ₁₂ (x varies in the range of −1 ≦ x ≦ 3 by charge / discharge reaction), ramsteride type Li _{2 + x} Ti ₃ O ₇ (x varies in the range of −1 ≦ x ≦ 3 by charge / discharge reaction), at least one selected from the group consisting of Ti and P, V, Sn, Cu, Ni and Fe And metal complex oxides containing these elements. Examples of the metal composite oxide containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni and Fe include 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). This metal complex oxide has a low crystallinity and preferably has a microstructure in which a crystal phase and an amorphous phase coexist or exist alone. Such a microstructured metal composite oxide can greatly improve the cycle performance. These metal composite oxides change to lithium titanium composite oxides when lithium is inserted by charging. Among lithium titanium composite oxides, spinel type lithium titanate is preferable because of its excellent cycle characteristics.

  Examples of other negative electrode active materials include metal compounds.

As the metal compound, metal sulfide or metal nitride can be used. As the metal sulfide, titanium sulfide such as TiS ₂ , molybdenum sulfide such as MoS ₂ , iron sulfide such as FeS, FeS ₂ , and Li _x FeS ₂ can be used. Metal nitrides can be used, for example, lithium cobalt nitride (e.g. _{Li s Co t N, 0 <} s <4,0 <t <0.5).

  The type of the negative electrode active material can be one type or two or more types.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyacrylic acid, fluorine rubber, and styrene butadiene rubber.

Examples of the conductive agent include carbon black, graphite (graphite), graphene, fullerenes, coke and the like. Among these, carbon black and graphite are preferable, and examples of the carbon black include acetylene black, ketjen black, and furnace black. In order to facilitate the reductive decomposition reaction of the nonaqueous electrolyte generated in the range of 0.55 to 1.1 V with respect to Li / Li ⁺ , those having a specific surface area of 10 to 1000 m ² / g are preferable. Moreover, it is desirable that the relationship of the formula (1) is established between the negative electrode and the conductive agent.

  The blending ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 73 to 96% by weight of the negative electrode active material, 2 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

  Hereinafter, the nonaqueous electrolyte battery of the embodiment will be described in detail for each member.

1) Positive electrode This positive electrode has a positive electrode current collector and a positive electrode material layer (positive electrode active material-containing layer) supported on one or both surfaces of the current collector and containing an active material, a conductive agent, and a binder.

  For this positive electrode, for example, a conductive agent and a binder are added to the positive electrode active material, these are suspended in an appropriate solvent, and this suspension is applied to a current collector such as an aluminum foil, dried and pressed. It is produced by forming a strip electrode.

Examples of the positive electrode active material include various oxides and sulfides. For example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg, Li _x NiO ₂₎ ), Lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel cobalt composite oxide {for example, Li _x Ni _1-yz Co _y M _z O ₂ (M is at least selected from the group consisting of Al, Cr and Fe) 1 element), 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1}, lithium manganese cobalt composite oxide {for example, Li _x Mn _1-yz Co _y M _z O ₂ (M is Al, At least one element selected from the group consisting of Cr and Fe), 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1}, lithium manganese nickel composite compound {for example, Li _x Mn _1/3 Ni _{1 / 3} Co _{1 /} 3 O ₂ or _Li x such _{Li x Mn 1/2 Ni 1/2 O 2} Mn y Ni y M 1-2y O 2 (M is at least one selected from the group consisting of Co, Cr, Al and Fe Kinds of elements, 1/3 ≦ y ≦ 1/2)}, spinel type lithium manganese nickel composite oxide (for example, Li _x Mn _{2 -y} Ni _y O ₄ ), lithium phosphorus oxide having an olivine structure (for example, Li _x such _{FePO 4, Li x Fe 1-} y Mn y PO 4, Li x CoPO 4), iron sulfate (e.g. _{Fe 2 (SO 4) 3)} , vanadium oxide (e.g. V ₂ O _5), and the like. In addition, conductive polymer materials such as polyaniline and polypyrrole, disulfide-based polymer materials, organic materials such as sulfur (S) and carbon fluoride, and inorganic materials are also included. In addition, about x, y, and z which do not have the description of the preferable range above, it is preferable that it is the range of 0 or more and 1 or less.

  More preferable positive electrode active materials are lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese nickel composite compound, spinel type lithium manganese nickel composite oxide, lithium manganese cobalt. Examples include composite oxides and lithium iron phosphate. According to these positive electrode active materials, a high battery voltage is obtained.

  The type of the positive electrode active material can be one type or two or more types.

  Examples of the conductive agent include carbon black, graphite (graphite), graphene, fullerenes, coke and the like. Among these, carbon black and graphite are preferable, and examples of the carbon black include acetylene black, ketjen black, and furnace black.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyacrylic acid, and fluorine 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 20% by weight of the conductive agent, and 2 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 average crystal grain size of the aluminum foil and the aluminum alloy foil is preferably 50 μm or less. More preferably, it is 30 μm or less. More preferably, it is 5 μm or less. When the average crystal grain size is 50 μm or less, the strength of the aluminum foil or aluminum alloy foil can be dramatically increased, the positive electrode can be densified with a high press pressure, and the battery capacity is increased. Can be made.

  The thickness of the current collector is 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. As the aluminum alloy, an alloy containing elements such as magnesium, zinc and silicon is preferable. On the other hand, the content of transition metals such as iron, copper, nickel and chromium is preferably 1% by mass or less.

2) Nonaqueous electrolyte The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. Further, the non-aqueous solvent may contain a polymer. However, as the non-aqueous electrolyte, one that can cause reductive decomposition with the negative electrode in the range of 0.55 to 0.9 V with respect to Li / Li ⁺ is used.

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , Li (CF ₃ SO ₂ ) ₂ N (bistrifluoromethanesulfonylamide lithium; commonly known as LiTFSI), LiCF ₃ SO ₃ (commonly known as LiTFS), and Li (C ₂ F ₅ SO ₂ ). ₂ N (bis pentafluoroethanesulfonyl amide lithium; called _{LiBETI), LiClO 4, LiAsF 6} , LiSbF 6, bisoxalato Lato lithium borate _{(LiB (C 2 O 4)} 2 ( known as LiBOB)), difluoro (oxalato) borate Lithium (LiF ₂ BC ₂ O ₄ ), difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate (2-)-0,0) lithium borate (LiBF ₂ (OCOOC (CF ₃ ) ₂ ) Lithium salt such as (commonly known as LiBF ₂ (HHIB)). These electrolyte salts may be used alone or in combination of two or more. Particularly preferred are LiPF ₆ and LiBF ₄ .

  The electrolyte salt concentration is preferably in the range of 1.0 M or more and 3.0 M or less. Thereby, the performance when a high load current is passed can be improved.

The non-aqueous solvent is not particularly limited, but propylene carbonate (PC), ethylene carbonate (EC), 1,2-dimethoxyethane (DME), γ-butyrolactone (GBL), tetrahydrofuran (THF), 2 -Methyltetrahydrofuran (2-MeHF), 1,3-dioxolane, sulfolane, acetonitrile (AN), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), dipropyl carbonate (DPC), etc. It is done. These solvents may be used alone or in combination of two or more. When two or more kinds of solvents are combined, it is preferable to select from all solvents having a dielectric constant of 20 or more. Here, in order to promote reductive decomposition in the range of 0.55 to 1.1 V with respect to Li / Li ⁺ , the non-aqueous electrolyte preferably contains propylene carbonate, and the amount thereof is 100% by volume of the non-aqueous solvent. On the other hand, it is preferable to be within a range of 20 to 80% by volume.

  An additive may be added to the non-aqueous electrolyte. Although it does not specifically limit as an additive, Vinylene carbonate (VC), fluoro vinylene carbonate, methyl vinylene carbonate, fluoromethyl vinylene carbonate, ethyl vinylene carbonate, propyl vinylene carbonate, butyl vinylene carbonate, dimethyl vinylene carbonate, diethyl Examples include vinylene carbonate, dipropyl vinylene carbonate, vinylene acetate (VA), vinylene butyrate, vinylene hexanate, vinylene crotonate, catechol carbonate, propane sultone, and butane sultone. The type of additive can be one type or two or more types.

Moreover, in order to accelerate | stimulate the reductive decomposition in the range of 0.55-1.1V with respect to Li / Li ⁺ , what contains the cation represented by Chemical formula 1 as an additive is mentioned.

  Here, R, R ′, and R ″ each represent H, a halogen, an alkyl group, or a halogenated alkyl group, and may be the same as or different from each other.

  Examples of the cation represented by Chemical Formula 1 include 1-ethyl-3-methylimidazolium {EMI (R is an ethyl group, R ′ is a proton, R ″ is a methyl group)}, 1-butyl-3- Methylimidazolium {BMI (R is a butyl group, R ′ is a proton, R ″ is a methyl group), 1-ethyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, dimethyl Ethylimidazolium {DMEI (R is an ethyl group, R ′ is a methyl group, R ″ is a methyl group), etc. The concentration of the additive is 0.1% by weight with respect to 100% by weight of the nonaqueous electrolyte. The range is preferably 3% by weight or less, and more preferably 0.5% by weight or more and 1% by weight or less.

3) Separator The separator is not particularly limited as long as it has insulating properties, and a porous film or a nonwoven fabric made of a polymer such as polyolefin, cellulose, polyethylene terephthalate, and vinylon can be used. Inorganic particles may be contained in the porous film or nonwoven fabric. One type of separator material may be used, or two or more types may be used in combination.

4) Exterior member As the exterior member, a laminate film having a thickness of 0.5 mm or less or a metal container having a thickness of 3 mm or less is used. The metal container is more preferably 0.5 mm or less in thickness. A resin container made of a polyolefin resin, a polyvinyl chloride resin, a polystyrene resin, an acrylic resin, a phenol resin, a polyphenylene resin, a fluorine resin, or the like may be used.

  Examples of the shape of the exterior member, that is, the battery shape, include a flat type (thin type), a square type, a cylindrical type, a coin type, and a button type. In addition, the battery can be applied to, for example, a small-sized application loaded on a portable electronic device or the like, and a large-sized application loaded on a two-wheel to four-wheeled vehicle or the like.

  As the laminate film, a multilayer film in which a metal layer is interposed between resin layers is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin layer, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used. The laminate film can be formed into the shape of an exterior member by sealing by heat sealing.

  The metal container is made of aluminum or an aluminum alloy. As the aluminum alloy, an alloy containing elements such as magnesium, zinc and silicon is preferable. When transition metals such as iron, copper, nickel and chromium are contained in the alloy, the amount is preferably 100 ppm or less.

  The nonaqueous electrolyte battery desirably satisfies the following formula (2).

1.02Ca ≦ Cc ≦ 1.50Ca (2)
However, Ca is the electric capacity (Ah) of the negative electrode when charging to 1.0 V with respect to Li / Li ⁺ , and Cc is that of the positive electrode when charging to 4.2 V with respect to Li / Li ⁺ . Electric capacity (Ah).

  Here, when Cc is smaller than 1.02Ca, the negative electrode potential is unlikely to decrease during overcharge, and thus the effect of the present embodiment is difficult to obtain. On the other hand, if Cc is greater than 1.50Ca, the positive electrode potential is unlikely to rise, so that the reductive decomposition reaction of the non-aqueous electrolyte is completed during overcharge, which may make it difficult to obtain the effects of the present embodiment.

  An example of the nonaqueous electrolyte battery of the embodiment is shown in FIG. The battery shown in FIG. 1 is a sealed square nonaqueous electrolyte battery. The nonaqueous electrolyte battery includes an outer can 1, a lid 2, a positive external terminal 3, a negative external terminal 4, and an electrode group 5. An exterior member is composed of the exterior can 1 and the lid 2.

  The outer can 1 has a bottomed rectangular tube shape, and is formed of a metal such as aluminum, an aluminum alloy, iron, or stainless steel, for example.

  As shown in FIG. 2, the flat electrode group 5 has a positive electrode 6 and a negative electrode 7 wound in a flat shape with a separator 8 therebetween. The positive electrode 6 is a positive electrode except for, for example, a strip-shaped positive electrode current collector made of a metal foil, a positive electrode current collector tab 6a having one end parallel to the long side of the positive electrode current collector, and at least the positive electrode current collector tab 6a. And a positive electrode material layer (positive electrode active material-containing layer) 6b formed on the current collector. On the other hand, the negative electrode 7 excludes, for example, a strip-shaped negative electrode current collector made of a metal foil, a negative electrode current collector tab 7a having one end parallel to the long side of the negative electrode current collector, and at least a portion of the negative electrode current collector tab 7a. And a negative electrode material layer (negative electrode active material-containing layer) 7b formed on the negative electrode current collector.

  In the positive electrode 6, the separator 8, and the negative electrode 7, the positive electrode current collecting tab 6 a protrudes from the separator 8 in the winding axis direction of the electrode group, and the negative electrode current collecting tab 7 a protrudes from the separator 8 in the opposite direction. Thus, the positive electrode 6 and the negative electrode 7 are wound while being shifted in position. As a result of such winding, as shown in FIG. 2, the electrode group 5 has the positive electrode current collecting tab 6a wound in a spiral shape from one end face and is wound in a spiral form from the other end face. The negative electrode current collection tab 7a protrudes. An electrolytic solution (not shown) is impregnated in the electrode group 5.

  As shown in FIG. 1, the positive electrode current collecting tab 6a and the negative electrode current collecting tab 7a are each divided into two bundles with the vicinity of the winding center of the electrode group as a boundary. The conductive clamping member 9 includes first and second clamping parts 9a and 9b that are substantially U-shaped, and a connecting part that electrically connects the first clamping part 9a and the second clamping part 9b. 9c. In each of the positive and negative electrode current collecting tabs 6a and 7a, one bundle is sandwiched by the first sandwiching portion 9a, and the other bundle is sandwiched by the second sandwiching portion 9b.

  The positive electrode lead 10 includes a substantially rectangular support plate 10a, a through hole 10b opened in the support plate 10a, a bifurcated bifurcated branch from the support plate 10a, and a strip-shaped current collector 10c, 10d extending downward. Have On the other hand, the negative electrode lead 11 includes a substantially rectangular support plate 11a, a through hole 11b opened in the support plate 11a, a bifurcated branch from the support plate 11a, and a strip-shaped current collector 11c extending downward. 11d.

  The positive electrode lead 10 sandwiches the clamping member 9 between the current collectors 10c and 10d. The current collector 10 c is disposed in the first clamping part 9 a of the clamping member 9. The current collector 10d is disposed in the second clamping unit 9b. The current collectors 10c and 10d, the first and second clamping parts 9a and 9b, and the positive electrode current collector tab 6a are joined by, for example, ultrasonic welding. Thereby, the positive electrode 6 and the positive electrode lead 10 of the electrode group 5 are electrically connected via the positive electrode current collection tab 6a.

  The negative electrode lead 11 sandwiches the clamping member 9 between the current collectors 11c and 11d. The current collector 11 c is disposed in the first clamping part 9 a of the clamping member 9. On the other hand, the current collection part 11d is arrange | positioned at the 2nd clamping part 9b. The current collectors 11c and 11d, the first and second sandwiching portions 9a and 9b, and the negative electrode current collector tab 7a are joined by, for example, ultrasonic welding. Thereby, the negative electrode 7 and the negative electrode lead 11 of the electrode group 5 are electrically connected via the negative electrode current collection tab 7a.

  The materials of the positive and negative electrode leads 10 and 11 and the clamping member 9 are not particularly specified, but are preferably the same material as the positive and negative electrode external terminals 3 and 4. For the positive electrode external terminal 3, for example, aluminum or an aluminum alloy is used, and for the negative electrode external terminal 4, for example, aluminum, an aluminum alloy, copper, nickel, nickel-plated iron, or the like is used. For example, when the material of the external terminal is aluminum or an aluminum alloy, the lead material is preferably aluminum or an aluminum alloy. In addition, when the external terminal is copper, it is desirable that the material of the lead is copper.

  The rectangular plate-like lid 2 is seam welded to the opening of the outer can 1 by, for example, a laser. The lid 2 is made of a metal such as aluminum, aluminum alloy, iron or stainless steel, for example. The lid 2 and the outer can 1 are preferably formed from the same type of metal. The positive external terminal 3 is electrically connected to the support plate 10 a of the positive electrode lead 10, and the negative external terminal 4 is electrically connected to the support plate 11 a of the negative electrode lead 11. The insulating gasket 12 is disposed between the positive and negative external terminals 3 and 4 and the lid 2 and electrically insulates the positive and negative external terminals 3 and 4 and the lid 2. The insulating gasket 12 is preferably a resin molded product.

According to the negative electrode of the embodiment described above, the occlusion / release reaction potential of lithium is within the range of 1.2 to 2.5 V with respect to Li / Li ^{+ at} the charging current in the range of 1 × 10 ^{−4 to} 2C rate. Thus, the reductive decomposition reaction potential of the nonaqueous electrolyte is in the range of 0.55 to 1.1 V with respect to Li / Li ⁺ , and the Li—Al alloying reaction potential is 0.2 to ^{0 with} respect to Li / Li ⁺ . Since the negative electrode potential reaches within a range of 0.55 to 1.1 V with respect to Li / Li ^{+ due} to overcharging because of the range of 0.5 V, the reductive decomposition reaction of the nonaqueous electrolyte occurs. It is maintained almost constant and the positive electrode potential increases. As a result, overcharge can be detected by increasing the positive electrode potential before the negative electrode potential reaches the Li—Al alloying reaction potential. Moreover, since the Li—Al alloying reaction of the negative electrode current collector can be avoided, the strength and thermal stability of the negative electrode can be maintained. Thereby, the outstanding safety | security is realizable. Furthermore, since the negative electrode current collector does not become brittle and the shape of the negative electrode can be maintained, excellent charge / discharge cycle performance can also be obtained.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(Example 1) <Fabrication of positive electrode>
LiCoO ₂ is used as the positive electrode active material, and graphite powder is used as a conductive agent at a ratio of 8% by weight with respect to the whole positive electrode, and PVdF is used as a binder at 5% by weight with respect to the whole positive electrode. A slurry was prepared by mixing and dispersing in an n-methylpyrrolidone (NMP) solvent. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and pressed to produce a positive electrode having an electrode density of 3.3 g / cm ³ .

<Production of negative electrode>
Li ₄ Ti ₅ O ₁₂ is used as the negative electrode active material, and PVdF is used as a binder for the negative electrode so that graphite having a specific surface area of 20 m ² / g as a conductive agent is 10% by weight with respect to the whole negative electrode. A slurry was prepared by mixing in an N-methylpyrrolidone (NMP) solution to 3 wt%. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm, dried and pressed to form a negative electrode material layer on the current collector, and a strip-shaped negative electrode having an electrode density of 2.1 g / cm ^3. It was created. The obtained negative electrode satisfied the relationship of Se = 75Sa. The specific surface area of the conductive agent ^(m 2 / g), the measurement of the surface area of the conductive agent ^{(m 2)} and the area of the negative electrode ^{(m 2)} was performed by the following method.

  The specific surface area of the conductive agent was measured using BELSORP manufactured by Nippon Bell Co., Ltd. and calculated by the BET method. The surface area of the conductive agent was calculated by multiplying the specific surface area of the conductive agent by the conductive agent weight of the electrode. The area of the negative electrode was calculated by multiplying the width and length of the negative electrode material layer forming portion of the strip-shaped negative electrode.

<Positive adjustment of positive electrode and negative electrode>
And Cc = 1.10Ca by adjusting the amount of the positive electrode and the negative electrode, the negative electrode potential when the positive electrode potential becomes 4.7V (vs.Li/Li ⁺⁾ becomes 1.0V (vs.Li/Li ⁺⁾ I did it.

<Preparation of non-aqueous electrolyte>
A nonaqueous electrolyte composed of 33% by volume of PC and 67% by volume of DEC was mixed with 1.5M LiPF ₆ and 2% by weight of EMIBF ₄ to obtain a nonaqueous electrolyte.

<Battery assembly>
After impregnating a 20 μm-thick separator made of cellulose non-woven electrolyte with a non-aqueous electrolyte, the positive electrode is covered with this separator, and the negative electrode is overlapped with the separator so as to face the positive electrode and wound into a spiral shape. Groups were made. The electrode group was pressed into a flat shape. A flat-shaped electrode group is inserted into a can-shaped container made of aluminum having a thickness of 0.3 mm, and a flat type having a thickness of 5 mm, a width of 30 mm, a height of 25 mm, a weight of 100 g and a rated capacity of 6 Ah shown in FIG. A nonaqueous electrolyte battery was produced.

(Example 2)
A non-aqueous electrolyte composed of 33% by volume of PC and 67% by volume of DEC was mixed with 1.5M LiPF ₆ and 2% by weight of EMIBF ₄ to obtain a non-aqueous electrolyte. A battery was fabricated in the same manner as in Example 1 except that this nonaqueous electrolyte was used.

(Example 3)
A non-aqueous electrolyte composed of 33% by volume of PC and 67% by volume of DEC was mixed with 1.5M LiPF ₆ to obtain a non-aqueous electrolyte. A battery was fabricated in the same manner as in Example 1 except that this nonaqueous electrolyte was used.

(Example 4)
A non-aqueous solvent composed of 33% by volume of PC and 67% by volume of DEC was mixed with 1.5M LiPF ₆ and 0.1M lithium difluoro (oxalato) borate to obtain a non-aqueous electrolyte. A battery was fabricated in the same manner as in Example 1 except that this nonaqueous electrolyte was used.

(Example 5)
A non-aqueous electrolyte was prepared by mixing 1.5 M LiPF ₆ in a non-aqueous solvent consisting of 33 vol% EC and 67 vol% DEC. A battery was fabricated in the same manner as in Example 1 except that this nonaqueous electrolyte was used.

(Example 6)
A battery was fabricated in the same manner as in Example 1 except that the amounts of the positive electrode and the negative electrode were adjusted so that Cc = 0.90Ca.

  About the obtained battery, the charge / discharge cycle test was implemented with the following method, and the result is shown in Table 1. A cycle test in which the battery voltage was charged to 2.8 V at a 2C rate in a 60 ° C. environment and then discharged to 1.5 V was performed, and the number of cycles when the discharge capacity reached 80% of the initial cycle capacity was measured.

  Moreover, the overcharge test which charges a battery to 3.96V was implemented, the battery temperature after 30 minutes was measured, and the result is shown in Table 1.

For the negative electrode, the occlusion / release reaction potential of lithium, the reductive decomposition reaction potential of the nonaqueous electrolyte, and the Li—Al alloying reaction potential at a charging current in the range of 1 × 10 ^{−4 to} 2C rate were measured by the following methods. The results and the charging rate at the time of measurement are shown in Table 1 below.

A 2 cm × 2 cm size negative electrode was cut out from the battery, and this was used as a working electrode, and a three-electrode cell using metallic lithium as a counter electrode and a reference electrode was produced. This three-electrode cell was subjected to constant current discharge at a 0.2 C rate until the potential of the working electrode reached 3.0 V (vs. Li ^/ Li ⁺ ) in a 25 ° C. environment, and then at a 0.1 C rate for 100 hours. The battery was charged, and the lithium occlusion / release potential, the reduction reaction potential of the nonaqueous electrolyte, and the Li—Al alloying reaction potential were estimated from the plateau of the charge curve.

  Cc and Ca were measured by the following method.

Cc was measured by cutting out a 2 cm × 2 cm size positive electrode from the battery and using this as a working electrode to produce a three-electrode cell using metallic lithium for the counter electrode and the reference electrode. The three-electrode cell was discharged at a constant current of 0.1 C until the potential of the working electrode reached 3.0 V (vs. Li ^/ Li ⁺ ) in a 25 ° C. environment, and then 4.2 V (vs. Li / Cc was measured by performing constant-current charging at a rate of 0.1 C until reaching Li ⁺ ) and then performing constant-potential charging for 10 hours. The measurement of Ca was performed by cutting out a 2 cm × 2 cm size negative electrode from the battery, using this as a working electrode, and preparing a three-electrode cell using metallic lithium as a counter electrode and a reference electrode. The three-electrode cell was subjected to constant current discharge at a rate of 0.1 C until the working electrode potential reached 3.0 V (vs. Li ^/ Li ⁺ ) in a 25 ° C. environment, and then 1.0 V (vs. Li / Ca was measured by performing constant-current charging at a rate of 0.1 C until reaching Li ⁺ ) and then performing constant-potential charging for 10 hours.

  As is clear from Table 1, the batteries of Examples 1 to 4 have a lower battery temperature after the overcharge test than the batteries of Examples 5 and 6, and the safety of the batteries of Examples 1 to 4 is high. It was done. In addition, the batteries of Examples 1 to 4 are excellent in charge / discharge cycle performance as compared with the batteries of Examples 5 and 6.

  FIG. 3 shows changes with time of the positive electrode potential and the negative electrode potential during the overcharge test of Example 1, and FIG. As shown in FIG. 3, before overcharging, the negative electrode potential is substantially constant and the positive electrode potential rises slowly. When falling into an overcharged state, the negative electrode potential drops rapidly and reaches the reductive decomposition reaction potential of the nonaqueous electrolyte. While the reductive decomposition reaction occurs, the negative electrode potential is kept substantially constant, so that the positive electrode potential rises, and overcharge is detected by the rise of the positive electrode potential. Therefore, overcharge can be detected before the Li—Al alloying reaction occurs. On the other hand, in Example 5, as shown in FIG. 4, when the overcharged state is reached, the negative electrode potential drops significantly and reaches the Li—Al alloying reaction potential. Occurs.

According to the negative electrode for a non-aqueous electrolyte battery of at least one embodiment and example described above, the lithium occlusion / release reaction potential with respect to Li / Li ⁺ is at a charging current in the range of 1 × 10 ^{−4 to} 2C rate. Within the range of 1.2 to 2.5 V, the reductive decomposition reaction potential of the nonaqueous electrolyte is within the range of 0.55 to 1.1 V with respect to Li / Li ⁺ , and the Li—Al alloying reaction potential is Li Since it is in the range of 0.2 to 0.5 V with respect to / Li ⁺ , a nonaqueous electrolyte battery having excellent charge / discharge cycle performance and safety performance can be realized.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
Hereinafter, the invention described in the claims of the original application of the present application will be added.
[1] and the current collector made of aluminum or aluminum alloy, it is formed on the current collector, a negative electrode for nonaqueous electrolyte battery comprising a negative electrode material layer containing an anode active material and a conductive agent, 1 × 10 ^{- 4}
At a charging current in the range of ˜2C rate, the occlusion / release reaction potential of lithium is in the range of 1.2 to 2.5 V with respect to Li / Li ⁺ , and the reductive decomposition reaction potential of the nonaqueous electrolyte is changed to Li / Li ⁺ . On the other hand, the non-aqueous electrolyte battery is characterized in that the Li—Al alloying reaction potential is in the range of 0.2 to 0.5 V with respect to Li / Li ⁺ within the range of 0.55 to 1.1 V. Negative electrode.
[2] The negative electrode for a nonaqueous electrolyte battery according to [1], wherein the negative electrode active material contains a lithium titanium composite oxide.
[3] The non-aqueous solution according to any one of [1] to [2], which satisfies the following formula (1), and the conductive agent is a carbon material having a specific surface area of 10 to 1000 m ² / g. Electrode battery negative electrode.
10Sa ≦ Se ≦ 500Sa (1)
However, Sa is an area (m ² ) of the negative electrode, and Se is a surface area (m ² ) of the conductive agent.
It is.
[4] A nonaqueous electrolyte battery comprising the negative electrode for a nonaqueous electrolyte battery according to any one of [1] to [3], a positive electrode, and a nonaqueous electrolyte.
[5] The nonaqueous electrolyte battery according to [4], wherein the following expression (2) is satisfied.
1.02Ca ≦ Cc ≦ 1.50Ca (2)
However, Ca is the electric capacity (Ah) of the negative electrode when charged to 1.0 V with respect to Li / Li ⁺ , and Cc is charged to 4.2 V with respect to Li / Li ⁺ . The electric capacity (Ah) of the positive electrode.
[6] The nonaqueous electrolyte battery according to any one of [4] to [5], wherein the nonaqueous electrolyte includes a nonaqueous solvent whose propylene carbonate is 20 to 80% by volume.
[7] The nonaqueous electrolyte battery according to any one of [4] to [6], wherein the nonaqueous electrolyte includes a cation represented by Chemical Formula 1.
Here, R, R ′, and R ″ each represent H, a halogen, an alkyl group, or a halogenated alkyl group, and may be the same as or different from each other.
[8] Lithium bisoxalatoborate (LiB (C ₂ O ₄ ) ₂ ), lithium difluoro (oxalato) borate (LiF ₂ BC ₂ O ₄ ) and difluoro (trifluoro-2-oxide-) are added to the non-aqueous electrolyte. The non-water according to any one of [4] to [6], comprising at least one selected from the group consisting of 2-trifluoro-methylpropionate (2-)-0,0) lithium borate Electrolyte battery.

  DESCRIPTION OF SYMBOLS 1 ... Exterior can, 2 ... Cover, 3 ... Positive electrode external terminal, 4 ... Negative electrode external terminal, 5 ... Electrode group, 6 ... Positive electrode, 6a ... Positive electrode current collection tab, 6b ... Positive electrode material layer, 7 ... Negative electrode, 7a ... Negative electrode Current collecting tab, 7b ... negative electrode material layer, 8 ... separator, 9 ... clamping member, 10 ... positive electrode lead, 11 ... negative electrode lead, 12 ... insulating gasket.

Claims (5)

A negative electrode material layer comprising a current collector made of aluminum or an aluminum alloy, and a lithium-titanium composite oxide formed as the negative electrode active material and a carbon material having a specific surface area of 10 to 1000 m ² / g as a conductive agent. A negative electrode comprising:
A positive electrode including a positive electrode active material;
_{LiPF 6, LiBF 4, Li (} CF 3 SO 2) 2 N ( bis trifluoromethane sulfonyl amide _{lithium), LiCF 3 SO 3, Li} (C 2 F 5 SO 2) 2 N ( bis pentafluoroethanesulfonyl amide lithium), LiClO ₄ , LiAsF ₆ , LiSbF ₆ , lithium bisoxalatoborate (LiB (C ₂ O ₄ ) ₂ ), lithium difluoro (oxalato) borate (LiF ₂ BC ₂ O ₄ ), and difluoro (trifluoro-2- One or two or more electrolyte salts selected from the group consisting of oxide-2-trifluoro-methylpropionate (2-)-0,0) lithium borate, and 20 to 80% by volume are propylene carbonate, The balance is ethylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran 2-methyltetrahydrofuran, 1,3-dioxolane, sulfolane, acetonitrile, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and a non-aqueous solvent is one kind or two or more solvents selected from the group consisting of dipropyl carbonate A non-aqueous electrolyte consisting of only ,
Satisfy the following formulas (1) and (2),
10Sa ≦ Se ≦ 500Sa (1)
Sa is an area (m ² ) of the negative electrode, Se is a surface area (m ² ) of the conductive agent, and the area of the negative electrode is a value obtained by multiplying the width and length of the negative electrode material layer,
1.02Ca ≦ Cc ≦ 1.50Ca (2)
The Ca is the electric capacity (Ah) of the negative electrode when charged to Li / Li ⁺ to 1.0 V, and the Cc is the charge when charged to Li / Li ⁺ to 4.2 V. The electrical capacity (Ah) of the positive electrode,
At a charging current in the range of 1 × 10 ^{−4 to} 2C rate, the lithium occlusion / release reaction of the negative electrode occurs within a range of 1.2 to 2.5 V with respect to Li / Li ⁺ , and the reduction of the nonaqueous electrolyte The plateau potential of the decomposition reaction is in the range of 0.55 to 1.1 V with respect to Li / Li ⁺ , and the plateau potential of the Li—Al alloying reaction is 0.2 to 0.5 V with respect to Li / Li ⁺ . A non-aqueous electrolyte battery that is within range.   The nonaqueous electrolyte battery according to claim 1, wherein the carbon material includes any one of carbon black, graphite (graphite), graphene, fullerenes, and coke. The electrolyte salt of the non-aqueous electrolyte includes lithium bisoxalatoborate (LiB (C ₂ O ₄ ) ₂ ), lithium difluoro (oxalato) borate (LiF ₂ BC ₂ O ₄ ) and difluoro (trifluoro-2-oxide). The nonaqueous electrolyte battery according to claim 1, comprising at least one selected from the group consisting of 2-trifluoro-methylpropionate (2-)-0,0) lithium borate.   The positive electrode active material is lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese nickel composite compound, spinel type lithium manganese nickel composite oxide, lithium manganese cobalt composite. The nonaqueous electrolyte battery according to claim 1, comprising at least one selected from the group consisting of an oxide and lithium iron phosphate. The positive electrode active material is Li _x Mn _y Ni _y M _1-2y O ₂ (M is at least one element selected from the group consisting of Co, Cr, Al and Fe, 1/3 ≦ y ≦ 1/2 The nonaqueous electrolyte battery of any one of Claims 1-3 containing the lithium manganese nickel composite compound represented by this.