JP2006339009A - Non-aqueous electrolyte battery and battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte battery superior in high load-current cycle characteristics at high temperature. <P>SOLUTION: The non-aqueous electrolyte battery is equipped with a positive electrode, a negative electrode, a non-aqueous solvent containing γ-butyrolactone, and a non-aqueous electrolyte including an electrolyte salt which is dissolved in the non-aqueous solvent and contains fluorine system lithium salt consisting of LiBF<SB>4</SB>and/or LiPF<SB>6</SB>and difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate(2-)-0,0) lithium borate as expressed in the chemical formula. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte battery and a battery pack including the assembled battery of the non-aqueous electrolyte battery.

As means for improving the cycle characteristics of the non-aqueous electrolyte battery, for example, difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate (2-)-0,0) lithium borate and LiPF ₆ were used. It is known to use an electrolyte (for example, Patent Document 1). However, the battery including the electrolyte described in Patent Document 1 does not have sufficient high-temperature cycle characteristics at a high load current such as rapid charging.
JP 2002-63935 A

  An object of this invention is to provide the nonaqueous electrolyte battery excellent in the high load current cycle characteristic under high temperature, and the battery pack provided with this nonaqueous electrolyte battery.

A nonaqueous electrolyte battery according to the present invention comprises a positive electrode,
A negative electrode,
a non-aqueous solvent containing γ-butyrolactone, a fluorine-based lithium salt dissolved in the non-aqueous solvent and composed of LiBF ₄ and / or LiPF ₆ and difluoro (trifluoro-2-oxide-2-trifluoro And a nonaqueous electrolyte containing an electrolyte salt containing methylpropionate (2-)-0,0) lithium borate.

  The battery pack according to the present invention includes the assembled battery of the nonaqueous electrolyte battery. In the assembled battery, it is preferable that the nonaqueous electrolyte batteries are electrically connected in series or in parallel.

  The battery pack may include a protection circuit that can detect a battery voltage of the nonaqueous electrolyte battery. Furthermore, the battery pack can be used on a vehicle.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte battery excellent in the high load current cycle characteristic under high temperature and the battery pack provided with this nonaqueous electrolyte battery can be provided.

According to the present invention, it is possible to obtain a non-aqueous electrolyte battery that is extremely excellent in high load current cycle characteristics at high temperatures. Difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate (2-)-0,0) lithium borate is not sufficient for high-temperature cycle characteristics, and it can be used for a high load current. There is a problem that is not suitable. Therefore, as a result of diligent research to improve high-load current cycle characteristics at high temperatures, as a result, a fluorine-based lithium salt composed of LiBF ₄ and / or LiPF ₆ as an electrolyte salt, and difluoro (trifluoro) represented by the following chemical formula 3 -2-oxide-2-trifluoro-methylpropionate (2-)-0,0) lithium borate and γ-butyrolactone (GBL) as a non-aqueous solvent achieves the above object. I found out.

  That is, GBL has high thermal stability and is advantageous for cycle characteristics at high temperatures, but has high reactivity with the electrode. The reason why the reactivity with the electrode is large is considered that GBL has a relatively high HOMO (easily withdrawing electrons, that is, is easily oxidized) and low LUMO (easily receives electrons, that is, is easily reduced). It is done. Lithium borate represented by the above chemical formula 3 can form a stable protective film against GBL on the surface of the positive electrode and the negative electrode at the time of initial charge, and a protective film formation reaction occurs at the time of charging during the cycle. The protective film can be regenerated, and a dense protective film can be formed as compared with vinylene carbonate (VC) that causes a film-forming reaction only at the initial charge. However, when the electrolyte salt is only this lithium borate, the formation of the protective film continuously occurs during charging and discharging, so that the film becomes too thick at the end of the cycle, and rapid capacity deterioration is confirmed. Since the fluorine-based lithium salt has higher electrochemical stability than lithium borate and can appropriately suppress the formation of the protective film of lithium borate, the ion conductivity of the protective film can be improved. As a result, it is possible to avoid the ion diffusion during rapid charging from being limited by the protective film, and it is possible to sufficiently suppress the reaction between the positive and negative electrodes and the GBL at a high temperature. In addition, the fluorine-based lithium salt has higher conductivity than lithium borate, and can contribute to improvement of the conductivity of the nonaqueous electrolyte. As a result, it is possible to improve high load current cycle characteristics at high temperatures.

  The electrolyte salt desirably has a molar ratio defined by the following formula (A).

0.05 ≦ (M ₁ / M ₂ ) ≦ 1.5 (A)
However, M ₁ is at the number of moles of the fluorine-based lithium salt, M ₂ represents the number of moles of said lithium borate.

When the molar ratio (M ₁ / M ₂ ) of the mixed salt is less than 0.05, there is a possibility that a sufficient effect for improving the cycle characteristics cannot be obtained. On the other hand, if the molar ratio (M ₁ / M ₂ ) exceeds 1.5, not only is the non-aqueous electrolyte less conductive and not suitable for high-load current use, but capacity degradation at the end of the cycle is severe. There is a fear. A more preferable range is 0.1 ≦ (M ₁ / M ₂ ) ≦ 1.5.

  Hereinafter, the positive electrode, the negative electrode, and the nonaqueous electrolyte will be described.

1) Positive electrode For example, a positive electrode is prepared by adding a conductive agent and a binder to a positive electrode active material, suspending them in an appropriate solvent, applying the suspension to a current collector such as an aluminum foil, drying, and pressing. 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, LiNi _1-yz Co _y M _z O ₂ (M is at least one selected from the group consisting of Al, Cr and Fe) Element), 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1}, lithium manganese cobalt composite oxide {for example, LiMn _1-yz Co _y M _z O ₂ (M is a group consisting of Al, Cr and Fe) At least one selected element), 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1}, lithium manganese nickel composite compound {for example, LiMn _x Ni _x M _1-2x O ₂ (M is Co, Cr) , A And at least one element selected from the group consisting of Fe), 1/3 ≦ x ≦ 1/2, for _{example, LiMn 1/3 Ni 1/3 Co 1/3 O} 2, LiMn 1/2 Ni 1 / ₂ O _2}, spinel type lithium-manganese-nickel composite oxide _{(Li x Mn 2-y Ni} y O 4), lithium phosphates having an olivine structure _{(Li x FePO 4, Li x} Fe 1-y Mn y PO 4 , Li _x CoPO ₄ ), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), vanadium oxide (eg, 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. More preferable positive electrodes for secondary batteries include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese nickel composite compound, and spinel type lithium manganese nickel with high battery voltage. Examples include composite oxides, lithium manganese cobalt composite oxides, and lithium iron phosphate. Note that x, y, and z that are not described in the above preferred ranges are preferably 0 or more and 1 or less. Examples of the positive electrode for the primary battery include manganese dioxide, iron oxide, copper oxide, iron sulfide, and carbon fluoride.

  Examples of the conductive agent include acetylene black, ketjen black, and graphite.

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

The mixing 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 18% by weight of the conductive agent, and 2 to 7% by weight of the binder. In addition, it is preferable to add Sn as a component other than the active material, the conductive agent, and the binder in the positive electrode. By adding Sn, a chemical reaction between the nonaqueous electrolyte and the positive electrode can be suppressed, which leads to improvement in cycle characteristics. The amount of Sn added is preferably in the range of 0.5 wt% or more and 20 wt% or less with respect to the active material. If the amount is less than 0.5% by weight, the effect of adding Sn is not sufficient, and if the amount is more than 20% by weight, the capacity may be reduced. Sn can be added to the raw material of the positive electrode active material, whereby a mixture of the positive electrode active material and a compound containing Sn such as Li ₂ SnO ₃ can be obtained. A sufficient effect can be obtained even when Sn is mixed with the positive electrode active material.

2) Negative electrode For example, the negative electrode is prepared by adding a binder to a powdered negative electrode active material, suspending these in an appropriate solvent, applying the suspension to a metal current collector such as a copper foil, and drying. It is produced by pressing into a strip electrode. You may add a electrically conductive agent as needed. Examples of the conductive agent include acetylene black, ketjen black, graphite, and metal powder. The compounding ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 80 to 98% by weight of the negative electrode active material, 0 to 18% by weight of the conductive agent, and 2 to 7% by weight of the binder.

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

  The negative electrode active material is preferably a material that occludes and releases lithium ions, and examples thereof include lithium metal, a lithium alloy, a carbonaceous material, and a metal compound.

  Examples of the lithium alloy include a lithium aluminum alloy, a lithium zinc alloy, a lithium magnesium alloy, a lithium silicon alloy, and a lithium lead alloy. When a lithium alloy foil is used, it may be used as a strip electrode as it is.

Examples of the carbonaceous material that absorbs and releases lithium ions include natural graphite, artificial graphite, coke, vapor grown carbon fiber, mesophase pitch carbon fiber, spherical carbon, and resin-fired carbon. More preferable carbonaceous materials include vapor grown carbon fiber, mesophase pitch carbon fiber, and spherical carbon. Plane spacing d ₀₀₂ of (002) plane by X-ray diffraction of the carbonaceous material is preferably not more than 0.340 nm.

Examples of the metal compound include metal oxides, metal sulfides, metal nitrides, and the like. For example, as a metal oxide, lithium titanate {for example, Li _{4 + x} Ti ₅ O ₁₂ , x is −1 ≦ x ≦ 3}, tungsten oxide (for example, WO ₃ ), amorphous tin oxide, tin silicon oxide (for example, SnSiO ₃ ), silicon oxide (for example, SiO), and the like. Examples of the metal sulfide include lithium sulfide (eg, TiS ₂ ), molybdenum sulfide (eg, MoS ₂ ), and iron sulfide (eg, FeS, FeS ₂ , Li _x FeS ₂ ). Examples of the metal nitride include lithium cobalt nitride (Li _x Co _y N, 0 <x <4, 0 <y <0.5).

  Among them, the negative electrode active material is preferably a material that occludes lithium at a potential of 0.4 V or more with respect to the potential of metallic lithium. Since lithium borate represented by Chemical Formula 3 is not so high in electrochemical stability on the reduction side, a negative electrode active material (for example, a carbonaceous material) that occludes lithium at a potential of less than 0.4 V with respect to the potential of metallic lithium. ), And a charge / discharge cycle is performed at a high load current, lithium borate may be reduced and decomposed preferentially, resulting in poor cycle characteristics. Among the negative electrode active materials that occlude lithium at a potential of 0.4 V or more with respect to the potential of metallic lithium, lithium titanate and iron sulfide are particularly preferable. This is because such a negative electrode active material is excellent in reversibility of insertion and extraction of lithium.

Moreover, it is preferable that the specific surface area by BET method of lithium titanate exists in the range of 7 g / m < ² > or more and 100 g / m < ² > or less. If the specific surface area is less than 7 g / m ² , the conductivity of the negative electrode is low, so that the negative electrode impedance increases during rapid charging, and the rapid charging characteristics may be degraded. When the specific surface area is larger than 100 g / m ² , the reactivity with the electrolytic solution is increased and the cycle characteristics may be deteriorated.

3) Nonaqueous electrolyte A nonaqueous electrolyte contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. Further, the non-aqueous solvent may contain a polymer.

The electrolyte salt includes a fluorine-based lithium salt composed of LiBF ₄ and / or LiPF ₆ and difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate (2-)-0, 0) Lithium borate. The non-aqueous solvent includes γ-butyrolactone.

In addition to the fluorine-based lithium salt and lithium borate described above, the electrolyte salt includes bistrifluoromethanesulfonylamide lithium (LiTFSI), lithium trifluoromethyltriflate (LiTFS), bispentafluoroethanesulfonylamide lithium (LiBETI), LiClO. ₄ , one or more kinds selected from LiAsF ₆ and LiSbF ₆ may be included.

  The electrolyte salt concentration is preferably in the range of 1.5M or more and 3M or less. When the electrolyte salt concentration is less than 1.5M, not only the above-described decomposition of lithium borate in Chemical Formula 3 but also the decomposition reaction of GBL proceeds, making it difficult to improve the high load current cycle characteristics at high temperatures. On the other hand, when the electrolyte salt concentration exceeds 3M, the viscosity increases, and it becomes difficult to improve the high-load current cycle characteristics at high temperatures. A more preferable range is 1.5M or more and 2.5M or less.

  The content of γ-butyrolactone (GBL) in the non-aqueous solvent is preferably in the range of 25% by volume to 88% by volume. When the amount of GBL is less than 25% by volume, there is a possibility that a sufficient effect of improving the thermal stability cannot be obtained. If the amount of GBL exceeds 88% by volume, it may not be possible to improve the cycle characteristics even when a fluorine-based lithium salt and lithium borate are used. A more preferable range is in the range of 40% by volume to 80% by volume.

  Solvent components other than GBL are not particularly limited, and examples thereof include organic solvents and ionic liquids. Examples of the organic solvent include propylene carbonate (PC: dielectric constant at 40 ° C. of 65), ethylene carbonate (EC: dielectric constant at 20 ° C. of 90), 1,2-dimethoxyethane (DME), γ-butyrolactone (GBL : Dielectric constant at 20 ° C is 42), tetrahydrofuran (THF: dielectric constant at 20 ° C is 7.4), 2-methyltetrahydrofuran (2-MeHF: dielectric constant at 20 ° C is 6.2), 1, 3-dioxolane (dielectric constant at 20 ° C. is 7.1), sulfolane (dielectric constant at 30 ° C. is 42), acetonitrile (AN: dielectric constant at 20 ° C. is 38), diethyl carbonate (DEC: at 20 ° C.) Dielectric constant of 2.8), dimethyl carbonate (DMC: dielectric constant at 20 ° C: 3.1), methyl ethyl carbonate (MEC: dielectric constant at 20 ° C of 2.9), Dipro Le carbonate (DPC), and the like.

On the other hand, examples of the ionic liquid include cation species selected from the group consisting of imidazolium salts, quaternary ammonium salts, pyrrolidinium salts, and piperidinium salts, BF ₄ , PF ₆ , bistrifluoromethanesulfonylamide anion (TFSI), And an anionic species selected from the group consisting of fluoromethyl triflate anion (TFS), bispentafluoroethanesulfonylamide anion (BETI), dicyanamide anion (DCA) and Cl. The solvent component may be one kind or two or more kinds.

  Moreover, when combining 2 or more types of organic solvents, it is desirable that the dielectric constant of each organic solvent is 20 or more. By using a combination of solvents having a dielectric constant of 20 or more, characteristics when a high load current flows are advantageous, and as a result, high load current cycle characteristics at high temperatures are improved.

  Examples of the organic solvent having a dielectric constant of 20 or more include propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane, acetonitrile and the like.

  Moreover, the additive may be included. Although it does not specifically limit as an additive, Vinylene carbonate (VC), vinylene acetate (VA), vinylene butyrate, vinylene hexanate, vinylene crotonate, catechol carbonate, etc. are mentioned. The concentration of the additive is preferably between 0.1 wt% and 3 wt% of the nonaqueous electrolyte. A more preferable range is 0.5% by weight or more and 1% by weight or less.

  The non-aqueous electrolyte desirably contains a non-ionic surfactant. Thereby, since the impregnation property of the nonaqueous electrolyte can be improved, the distribution of the nonaqueous electrolyte in the battery can be made uniform. As a result, it is possible to reduce the bias of the current distribution at the time of initial charge, so that a uniform protective film can be formed on the electrode surface. Due to the uniform protective film, the bias of the current distribution during cycling is reduced, so that the high load current cycle characteristics at high temperature can be further improved.

The amount of the nonionic surfactant is desirably in the range of 0.1% by weight to 3% by weight. If it is less than 0.1% by weight, the effect of improving the impregnation property may not be sufficiently obtained. On the other hand, if it is larger than 3% by weight, the conductivity of the nonaqueous electrolyte may be lowered. A more preferable range is 0.5% by weight or more and 1% by weight or less. Moreover, as a nonionic surfactant, the trialkyl phosphate shown to following Chemical formula 4 is preferable, and a trioctyl phosphate (TOP) is still more preferable especially. Improvement of impregnation can be achieved by adding the surfactant shown here.

  However, R is an alkyl group.

  The nonaqueous electrolyte battery according to the present invention can have various forms such as a cylindrical shape, a square shape, a flat shape, and a coin shape. An example of the coin-type non-aqueous electrolyte battery is shown in FIG.

  A pellet-shaped positive electrode 2 is accommodated in a metal positive electrode container 1 that also serves as a positive electrode terminal. The separator 3 is laminated on the positive electrode 2. The pellet-shaped negative electrode 4 is laminated on the separator 3. The nonaqueous electrolyte is impregnated in the positive electrode 2, the separator 3, and the negative electrode 4. The metal negative electrode container 5 also serving as the negative electrode terminal is caulked and fixed to the positive electrode container 1 via an insulating gasket 6 with the inner surface being in contact with the negative electrode 4.

  An example of the flat type nonaqueous electrolyte battery is shown in FIG.

  As shown in FIG. 2, the electrode group 7 has a structure in which a positive electrode 8 and a negative electrode 9 are wound in a spiral shape so as to have a flat shape with a separator 10 interposed therebetween. The electrode group 7 is manufactured by winding a positive electrode 8 and a negative electrode 9 in a spiral shape with a separator 10 interposed therebetween, and then applying a heat press. The positive electrode 8, the negative electrode 9, and the separator 10 in the electrode group 7 may be integrated with a polymer having adhesiveness. The strip-like positive electrode terminal 11 is electrically connected to the positive electrode 8. On the other hand, the strip-like negative electrode terminal 12 is electrically connected to the negative electrode 9. The electrode group 7 is housed in a laminated film container 13 with the ends of the positive electrode terminal 11 and the negative electrode terminal 12 protruding from the container 13. The laminated film container 13 is sealed by heat sealing.

  It is also possible to use a battery pack including an assembled battery in which a nonaqueous electrolyte battery is configured as a single battery. The non-aqueous electrolyte battery according to the present invention is particularly suitable when the protection circuit detects only the battery voltage because the positive or negative electrode potential can be easily controlled by detecting the battery voltage. In particular, lithium nickel-based metal oxides such as lithium nickel composite oxide, lithium nickel cobalt composite oxide, lithium manganese nickel composite compound, and spinel type lithium manganese nickel composite oxide have a high effect of suppressing overvoltage. The voltage variation between the single batteries can be reduced, and the voltage detection becomes easier.

  The single batteries constituting the assembled battery may be connected in series or in parallel. Further, it is desirable to use the flat battery shown in FIG.

  The battery unit 21 in the battery pack of FIG. 3 is composed of a flat type non-aqueous electrolyte battery shown in FIG. The plurality of battery units 21 are stacked in the thickness direction with the direction in which the positive electrode terminal 11 and the negative electrode terminal 12 protrude are aligned. As shown in FIG. 4, the battery units 21 are connected in series to form an assembled battery 22. As shown in FIG. 3, the assembled battery 22 is integrated by an adhesive tape 23.

  A printed wiring board 24 is disposed on the side surface from which the positive electrode terminal 11 and the negative electrode terminal 12 protrude. As shown in FIG. 4, a thermistor 25, a protection circuit 26, and a terminal 27 for energizing external devices are mounted on the printed wiring board 24.

  As shown in FIGS. 3 and 4, the positive side wiring 28 of the assembled battery 22 is electrically connected to the positive side connector 29 of the protection circuit 26 of the printed wiring board 24. The negative electrode side wiring 30 of the assembled battery 22 is electrically connected to the negative electrode side connector 31 of the protection circuit 26 of the printed wiring board 24.

  The thermistor 25 is for detecting the temperature of the battery unit 21, and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the plus side wiring 31a and the minus side wiring 31b between the protection circuit and a terminal for energization to an external device under a predetermined condition. The predetermined condition is, for example, when the detected temperature of the thermistor becomes equal to or higher than a predetermined temperature, or when overcharge, overdischarge, overcurrent, or the like of the battery unit 21 is detected. This detection method is performed for each individual battery unit 21 or the entire battery unit 21. When detecting each battery unit 21, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each battery unit 21. In the case of FIG. 4, wiring 32 for voltage detection is connected to each battery unit 21, and a detection signal is transmitted to the protection circuit 26 through these wirings 32.

  With respect to the assembled battery 22, protective sheets 33 made of rubber or resin are disposed on three side surfaces other than the side surfaces from which the positive electrode terminal 11 and the negative electrode terminal 12 protrude. Between the side surface from which the positive electrode terminal 11 and the negative electrode terminal 12 protrude and the printed wiring board 24, a block-shaped protection block 34 made of rubber or resin is disposed.

  The assembled battery 22 is stored in a storage container 35 together with the protective sheets 33, the protective blocks 34, and the printed wiring board 24. That is, the protective sheet 33 is disposed on each of the inner side surface in the long side direction and the inner side surface in the short side direction of the storage container 35, and the printed wiring board 24 is disposed on the inner side surface on the opposite side in the short side direction. The assembled battery 22 is located in a space surrounded by the protective sheet 33 and the printed wiring board 24. A lid 36 is attached to the upper surface of the storage container 35.

  In addition, instead of the adhesive tape 23, a heat shrink tape may be used for fixing the assembled battery 22. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tube is circulated, and then the heat shrinkable tube is thermally contracted to bind the assembled battery.

  3 and 4 are connected in series, but may be connected in parallel to increase the battery capacity. Of course, the assembled battery packs can be connected in series and in parallel.

  Moreover, the aspect of a battery pack is changed suitably by a use.

  As a use of the battery pack, one that is supposed to be used in a high temperature environment is preferable. Specific examples include in-vehicle use such as two-wheel to four-wheel hybrid electric vehicles, two-wheel to four-wheel electric vehicles, and assist bicycles, and emergency use of electronic devices.

  In the case of in-vehicle use, cycle characteristics in a high temperature environment of about 60 ° C. are required. In the case of emergency use of electronic equipment, cycle characteristics under a high temperature environment of about 45 ° C. are required. As shown in the examples described later, since the rapid charge cycle characteristics at 60 ° C. are improved, it can be applied to both in-vehicle use and emergency use of electronic devices. In particular, the vehicle-mounted one is suitable.

[Example]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
<Preparation of positive electrode>
As a positive electrode active material, a mixture of compounds containing LiCoO ₂ and Sn was prepared. This positive electrode active material is blended with graphite powder so that the proportion of the conductive material is 8% by weight with respect to the whole positive electrode, and PVdF is blended with the positive electrode as a binder so as to be 5% by weight with respect to the whole positive electrode. After preparing a slurry by dispersing in a pyrrolidone (NMP) solvent, a positive electrode having an electrode density of 3.3 g / cm ³ was prepared through coating, drying, and pressing on an aluminum foil having a thickness of 15 μm.

<Production of negative electrode>
A slurry obtained by mixing 90 parts by weight of Li ₄ Ti ₅ O ₁₂ (specific surface area of 9 m ² / g by BET method) and 10 parts by weight of PVdF as a binder in an N-methylpyrrolidone (NMP) solution. Was prepared. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm, dried and pressed to prepare a negative electrode.

A method for measuring the specific surface area of the negative electrode active material by the BET method will be described below. When a mixed gas of nitrogen is allowed to flow into the U-shaped cell containing the sample and the sample chamber is cooled to liquid nitrogen temperature, only N ₂ gas is adsorbed on the sample surface. Next, desorption starts when the cell is returned to room temperature. The specific surface area was measured by detecting the amount of desorbed N ₂ gas and dividing by the sample weight.

  As a measuring device, a product name manufactured by Yuasa Ionics used Kantasorb. The sample amount was set to around 0.5 g, and the sample was deaerated at 120 ° C. for 15 minutes as a pretreatment.

<Preparation of non-aqueous electrolyte>
1M LiBF ₄ and 1M difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate (2-)-0 in a solvent in which EC and GBL were mixed at a volume ratio (EC: GBL) of 1: 2 , 0) Lithium borate {LiBF ₂ (HHIB)} was dissolved to obtain a non-aqueous electrolyte (non-aqueous electrolyte). The molar ratio (M ₁ / M ₂ ) in this nonaqueous electrolyte was 1.

<Battery assembly>
The positive electrode is housed in a positive electrode can made of stainless steel, the negative electrode is housed in a negative electrode can made of stainless steel, and a separator made of polypropylene non-woven fabric is disposed between the positive electrode and the negative electrode, and 1 × 10 ⁻³ Torr. The coin type non-aqueous electrolyte battery having the structure shown in FIG. 1 was assembled by allowing the negative electrode can to be caulked and fixed to the positive electrode can via an insulating gasket after being left under reduced pressure for 2 hours.

(Examples 2 to 21)
A battery was fabricated in the same manner as in Example 1 except that the nonaqueous electrolyte composition, the positive electrode active material, and the negative electrode active material were changed as shown in Tables 1 and 2 below.

(Example 22)
0.5% by weight of trioctyl phosphate was mixed with the nonaqueous electrolytic solution of Example 1. A battery was fabricated in the same manner as in Example 1 except that such a nonaqueous electrolyte was used.

(Comparative Examples 1-16)
A battery was fabricated in the same manner as in Example 1 except that the nonaqueous electrolyte composition, the positive electrode active material, and the negative electrode active material were changed as shown in Tables 3 to 4 below.

The obtained battery was charged at 60 ° C. at a current value of 5 C until the battery voltage reached 2.7 V, and discharged at a charge value of 1 C until the battery voltage reached 1.5 V. Tables 1 to 4 below show the number of cycles in which the capacity retention rate reached 60% (the capacity of the first cycle was set to 100%). For those using a carbonaceous material as the negative electrode active material, the cutoff voltage during charging was 4.2 V, and the cutoff voltage during discharging was 3 V. Note that charging at 5C corresponds to rapid charging.

As is apparent from Tables 1 to 4, according to Examples 1 to 22 comprising an electrolyte salt containing LiBF ₄ and / or LiPF ₆ and LiBF ₂ (HHIB) and a non-aqueous solvent containing GBL, It can be understood that the quick charge cycle characteristics are superior to those of Comparative Examples 1-16.

The molar ratio (M ₁ / M ₂ ) was more excellent when the molar ratio (M ₁ / M ₂ ) was in the range of 0.05 or more and 1.5 or less from the comparison of Examples 1 and 15 to 19. It can be seen that cycle characteristics can be obtained, and further excellent cycle characteristics can be obtained in the range of 0.1 to 1.5.

  As for the electrolyte salt concentration, it can be seen from the comparison of Examples 1, 20, and 21 that more excellent cycle characteristics can be obtained in Example 1 in the range of 1.5 M or more and 3 M or less.

  As for the addition of Sn, it can be seen from the comparison between Examples 1 and 4 that more excellent cycle characteristics can be obtained in Example 1 using the positive electrode active material containing Sn.

  As for the solvent composition, it can be seen from the comparison of Examples 1 and 2 that superior cycle characteristics can be obtained in Example 2 using a non-aqueous solvent containing EC, PC and GBL.

  Regarding the positive electrode active material, lithium borate was added because the original cycle characteristics of Li—Ni oxide (Ni-rich composite oxide) were lower than that of Li—Co oxide, as compared with Examples 1 and 11-14. Although there are those having a lower cycle number than Li-Co oxide (Co-rich composite oxide) of Example 1, implementation using lithium nickel cobalt composite oxide or lithium manganese nickel composite oxide In Examples 11 to 13, good cycle characteristics are obtained. Lithium-nickel-cobalt composite oxide and lithium-manganese-nickel composite oxide have a lower battery operating voltage than lithium cobaltate, so that the decomposition reaction of lithium borate proceeds gently, and the effect of suppressing the resistance increase at the end of the cycle is suppressed. Because it is expensive. On the other hand, when a lithium manganese composite oxide is used as in Example 14, the battery operating voltage is higher than that of lithium cobaltate, so that the decomposition reaction of lithium borate easily proceeds.

  As for the negative electrode active material, in comparison with Examples 1, 9, and 10, it was more excellent in Examples 1 and 10 that used an active material that occludes lithium at a potential of 0.4 V or more with respect to the potential of metallic lithium. It can be understood that cycle characteristics can be obtained. Among them, high cycle characteristics were obtained in Example 1 using lithium titanate.

Regarding the specific surface area of the negative electrode active material, by comparing Examples 1 to 5 to 8, in Examples 1, 5, and 6 having a specific surface area of 7 g / m ² or more and 100 g / m ² or less, a more excellent cycle It can be understood that characteristics can be obtained.

  On the other hand, from the results of Comparative Examples 1 to 14, when only one of the fluorine-based lithium salt or lithium borate is used as the electrolyte salt, the cycle characteristics can be improved even if the same active material as in the examples is used. I understand that I can't hope. Further, from the results of Comparative Example 15, it can be understood that the improvement in cycle characteristics cannot be expected with a lithium borate derivative different from the example. This is because lithium borate derivatives different from the examples are easily decomposed by GBL and also have poor conductivity.

  Furthermore, even if the nonaqueous electrolyte similar to Example 1 is used, if GBL is not contained in the nonaqueous solvent as in Comparative Example 16, the resistance increase due to the protective film formed on the electrode surface becomes large. , Cycle life is shortened.

  As described above in detail, if a non-aqueous electrolyte battery is produced, rapid charging is possible and the cycle characteristics at high temperature can be made extremely excellent.

  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.

The typical sectional view showing the coin type nonaqueous electrolyte battery which is one embodiment of the nonaqueous electrolyte battery concerning the present invention. The typical sectional view showing the flat type nonaqueous electrolyte battery which is another embodiment of the nonaqueous electrolyte battery concerning the present invention. The disassembled perspective view of the battery pack which is another embodiment of the nonaqueous electrolyte battery which concerns on this invention. The block diagram which shows the electric circuit of the battery pack of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Positive electrode can, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Negative electrode can, 6 ... Insulating gasket, 8 ... Positive electrode, 9 ... Negative electrode, 10 ... Separator, 11 ... Positive electrode terminal, 12 ... Negative electrode terminal, 13 DESCRIPTION OF SYMBOLS ... Container, 21 ... Battery unit, 22 ... Assembly battery, 23 ... Adhesive tape, 24 ... Printed wiring board, 28 ... Positive electrode side wiring, 29 ... Positive electrode side connector, 30 ... Negative electrode side wiring, 31 ... Negative electrode side connector, 33 ... Protective block, 35 ... storage container, 36 ... lid.

Claims (5)

A positive electrode;
A negative electrode,
a non-aqueous solvent containing γ-butyrolactone, a fluorine-based lithium salt dissolved in the non-aqueous solvent and composed of LiBF ₄ and / or LiPF ₆ and difluoro (trifluoro-2-oxide-2-trifluoro A nonaqueous electrolyte battery comprising: a nonaqueous electrolyte containing an electrolyte salt containing methylpropionate (2-)-0,0) lithium borate.

2. The nonaqueous electrolyte battery according to claim 1, wherein the electrolyte salt has a molar ratio defined by the following formula (A).
0.05 ≦ (M ₁ / M ₂ ) ≦ 1.5 (A)
However, M ₁ is at the number of moles of the fluorine-based lithium salt, M ₂ represents the number of moles of said lithium borate.   The nonaqueous electrolyte battery according to claim 1, wherein a concentration of the electrolyte salt is 1.5 M or more and 3 M or less.   The nonaqueous electrolyte battery according to claim 1, wherein the nonaqueous solvent is composed of γ-butyrolactone and a solvent having a dielectric constant of 20 or more.   A battery pack comprising the assembled battery of a nonaqueous electrolyte battery according to claim 1.

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