JP6353114B2 - Negative electrode - Google Patents

Description

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

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

  On the other hand, when it is installed in a car such as an automobile or a train, the constituent materials of the positive electrode and the negative electrode are chemical, electrical, etc. because of storage performance under high temperature environment (60 ° C or higher), cycle performance, and long-term reliability of high output. A material excellent in chemical stability, strength and corrosion resistance is preferred. Furthermore, high performance is required even in a cold region, and it is desirable to have high output performance and long life performance in a low temperature environment (−40 ° C.). In addition, non-volatile electrolytes and non-flammable electrolytes have been developed as non-aqueous electrolytes from the viewpoint of improving safety performance, but they have not been put into practical use because of a decrease in output characteristics, low temperature performance, and long life performance.

  As described above, at least high temperature durability is required to mount a lithium ion battery in a car or the like. This is because if it is inferior in high temperature durability, it is difficult to use it in an engine room of an automobile as an alternative to a lead storage battery.

  In such a secondary battery, if the negative electrode is thinned and densified to increase the capacity, the current collector strength is not sufficient, so there are significant restrictions on battery capacity, output performance, cycle life, and reliability. There is a risk of receiving. Although electrode thinning has been studied from the viewpoint of increasing the output, it is difficult to obtain a high output because the particle diameter of the active material is as large as several μm to several tens of μm. In particular, in a low temperature environment (−20 ° C. or lower), the utilization factor of the active material is reduced and it is difficult to discharge. Further, if the particle size of the negative electrode active material is increased instead of making the negative electrode thinner, it becomes difficult to obtain higher performance with an increase in the interfacial resistance of the electrode.

By the way, lithium iron phosphate (Li _x FePO ₄ ) and lithium manganese phosphate (Li _x MnPO ₄ ) have attracted attention as lithium ion metal compounds having an olivine crystal structure as positive electrode active materials for improving the positive electrode performance. Improvement of thermal stability is achieved. However, since these positive electrode active materials have low electronic conductivity, there is a problem in charge / discharge rate performance. In addition, at a high temperature of 45 ° C. or higher, iron or manganese in the positive electrode active material is dissolved and deposited on the negative electrode, and cycle life deterioration is accelerated. On the other hand, when a carbon material is used for the negative electrode at a low temperature, deterioration due to metal lithium precipitation is likely to accelerate. Therefore, when lithium ion batteries using these positive electrode active materials are used in automobiles, it is necessary to keep the battery temperature as constant as possible by subjecting the battery to air cooling or water cooling, which increases the volume or weight of the battery pack. Incurs an increase in cost.

JP 2001-143702 A Japanese Patent No. 4237659

  According to the embodiment, a negative electrode active material, a non-aqueous electrolyte battery, and a battery pack that are excellent in high-temperature cycle performance can be provided.

According to the embodiment, a negative electrode active material is provided. The negative electrode active material is Li _{2 + a Ad} Ti _6-b B _b O _14-c (A includes at least one element selected from the group consisting of Na and K, and B is Ta or Nb, a, b, c And d satisfying 0 ≦ a ≦ 5, 0 <b <6, 0 ≦ c ≦ 0.6, and 0 <d ≦ 3), and a carbon material covering at least a part of the surface of the particle Including.

Moreover, according to the embodiment, a nonaqueous electrolyte battery including a positive electrode, a negative electrode including the negative electrode active material of the embodiment, and a nonaqueous electrolyte is provided.

  Furthermore, according to the embodiment, a battery pack including a nonaqueous electrolyte battery is provided. Moreover, according to embodiment, the vehicle containing the battery pack of embodiment is provided.

FIG. 1 is a partially cutaway perspective view showing a nonaqueous electrolyte battery according to an embodiment. FIG. 2 is an enlarged cross-sectional view of a part A in FIG. FIG. 3 is a partially cutaway cross-sectional view of the nonaqueous electrolyte battery of the embodiment. FIG. 4 is a side view of the battery of FIG. FIG. 5 is a perspective view illustrating an example of an assembled battery used in the battery pack according to the embodiment. FIG. 6 is a perspective view schematically showing the battery pack according to the embodiment. FIG. 7 is an exploded perspective view of the battery pack according to the embodiment. FIG. 8 is a block diagram showing an electric circuit of the battery pack of FIG.

(First embodiment)
According to the first embodiment, Li _{2 + a Ad} Ti _6-b B _b O _14-c (A is at least one element selected from the group consisting of Na, K, Mg, Ca, Ba and Sr, B Is a metal element other than Ti, a, b, c and d are atomic ratios or molar ratios, and 0 ≦ a ≦ 5, 0 ≦ b ≦ 6, 0 ≦ c ≦ 0.6, 0 ≦ d ≦ 3 A negative electrode active material is provided, which includes a particle represented by (Fill) and a carbon material that covers at least a part of the particle surface.

  Since this negative electrode active material can form a film on the surface (particularly on the carbon material) during initial charging, it suppresses the reductive decomposition reaction of the nonaqueous electrolyte in the negative electrode in a high temperature environment (for example, 45 ° C. or higher). be able to. In addition, this negative electrode active material exhibits excellent electronic conductivity even after the film is formed. Therefore, since the negative electrode containing the negative electrode active material can reduce resistance, the high-temperature cycle life performance and large current discharge performance of a nonaqueous electrolyte battery can be improved.

  Although the form of a carbon material is not specifically limited, For example, it can be set as a layer form, particle form, fiber form, etc. The content of the carbon material in the negative electrode active material is desirably in the range of 0.05% by weight to 5% by weight. Thereby, it is possible to improve the high-temperature cycle life performance without significantly reducing the discharge capacity of the nonaqueous electrolyte battery as compared with the case where no carbon material is used. A more preferable range of the content of the carbon material is a range of 0.1 wt% or more and 3 wt% or less.

In _{Li 2 + a A d Ti 6} -b B b O 14-c, B element, selected V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, from the group consisting of Ta and Al It is preferable that it is at least one kind of element. More preferably, it is Nb. Nb improves cycle life performance. Further, c is preferably in the range of 0 ≦ c ≦ 0.6. When c exceeds this range, the capacity is significantly reduced. A more preferable range is 0 ≦ c ≦ 0.2. Within this range, the capacity of the negative electrode is reduced little and high electron conductivity can be exhibited. On the other hand, a more preferable range of d is a range of 1 ≦ d ≦ 2.5. This range is preferable because the potential of the negative electrode shifts to the base side and a high battery voltage can be obtained.

Particles represented by _{Li 2 + a A d Ti 6} -b B b O 14-c preferably has a crystal structure of the space group Cmca.

_{Li 2 + a A d Ti 6} -b B b O a specific composition represented by particles _{14-c, Li 2 + a} SrTi 6 O 14-c, Li 2 + a BaTi 6 O 14-c, Li 2 + a MgTi 6 O 14 _{-c, Li 2 + a KTi 5} TaO 14-c, Li 2 + a K 0.5 Sr 0.5 Ta 0.5 Ti 5.5 O 14-c, Li 2 + a Na 0.5 Sr 0.5 Ta 0.5 Ti _5.5 O _14-c , Li _{2 + a} Sr _0.5 Ta _0.5 Ti ₆ O _14-c, Li _{2 + a} NaTi ₅ NbO _14-c , Li _{2 + a} Na ₂ Ti ₆ O _14-c , Li _{2 + a} Na _{0. 5} Sr _0.5 Ti _5.5 Nb _0.5 O _{14-c and the} like. With these compositions, the electronic conductivity of the negative electrode active material can be improved, so that large current performance and cycle life performance can be significantly improved. The composition to be used is not limited to one type, and two or more types of particles having different compositions may be used in combination.

The negative electrode containing the negative electrode active material has a potential range of 2 V to 0.5 V (2 to 0.5 V vs. Li / Li ⁺ ) with respect to the electrode potential of lithium metal at the time of occlusion (charge) release (discharge) of lithium ions, More preferably, it is used in the range of 2 V to ¹ V (2 to 1 V vs. Li / Li ⁺ ). Even if the negative electrode containing the negative electrode active material of the embodiment is used in this potential range, it can suppress reductive decomposition of the nonaqueous electrolyte in a high temperature environment. Further, by using the negative electrode in this potential range, metal Li deposition during charging in a low temperature environment is greatly suppressed, and cycle life performance and safety are greatly improved.

The true density of the negative electrode active material (excluding the carbon material) is preferably 3.5 to 4.8 g / cm ³ . Within this range, the volume specific capacity can be increased.

  The form of the negative electrode active material can be primary particles alone, secondary particles, or a mixture of single primary particles and secondary particles. It is preferable that secondary particles are contained. The average particle diameter (diameter) of the primary particles is preferably in the range of 0.001 to 2 μm. Moreover, the preferable average particle diameter of a secondary particle is 2-20 micrometers. Within this range, the packing density of the negative electrode can be increased.

The negative electrode active material is produced by, for example, a solid phase synthesis method, a hydrothermal synthesis method, or a liquid phase synthesis method. Hereinafter, a solid phase synthesis method using LiSrTi ₆ O _14-c as an example will be described as an example of a method for producing a negative electrode active material. After mixing raw materials SrCO ₃ , TiO ₂ and Li ₂ CO ₃ in a stoichiometric ratio, the resulting mixture is subjected to a pre-baking treatment at 400 to 700 ° C. for 1 to 3 hours to obtain a predetermined average particle size. Grind up to. The obtained sample powder is mixed with a solution containing a carbon precursor (for example, a polyvinyl alcohol solution, an aqueous carboxymethyl cellulose solution), and the obtained dispersion is sprayed and dried to obtain a sample powder. Then, at least a part of the surface is coated with carbon material particles having an average primary particle size of 2 μm or less by subjecting the sample powder to a main firing treatment in the range of 800 to 1300 ° C. in an inert atmosphere in an argon stream. LiSrTi ₆ O _14-c particles are obtained. The value of c can be controlled by the amount of carbon, the main firing temperature, and the time. According to the hydrothermal synthesis method or the liquid phase synthesis method, LiSrTi ₆ O _14-c particles having at least a part of the surface coated with carbon material particles having an average primary particle size of 0.5 μm or less can be obtained.

The negative electrode active material may contain a negative electrode active material other than an oxide represented by Li _{2 + a Ad} Ti _6-b B _b O _14-c . Examples of other negative electrode active materials include titanium oxide. As long as the titanium oxide is capable of occluding and releasing Li, the titanium oxide may include lithium at the time of synthesis, or may not change to a composition that does not include lithium at the time of synthesis and that includes lithium during subsequent charging and discharging. . An example of including lithium at the time of synthesis is lithium titanium oxide. Examples of the lithium titanium oxide include spinel structure lithium titanium oxide (for example, general formula Li 4/3 _{+ x} Ti _5/3 O ₄ (0 ≦ x ≦ 1)), ramsdelide structure lithium titanium oxide (for example, general formula Li _{2 + x} Ti ₃ O ₇ (0 ≦ x ≦ 1)) _, Li _{1 + x} Ti ₂ O ₄ (0 ≦ x ≦ 1), Li _{1.1 + x} Ti _1.8 O ₄ (0 ≦ x ≦ 1), Li _{1. 07 + x} Ti _1.86 O ₄ (0 ≦ x ≦ 1) is included. Examples that do not contain lithium during synthesis include titanium dioxide and niobium titanium oxide. Examples of titanium dioxide include those having a monoclinic structure, those having a rutile structure, and those having an anatase structure. Examples of titanium dioxide having a monoclinic structure include those represented by the general formula Li _x TiO ₂ (0 ≦ x, more preferably 0 ≦ x ≦ 1) (bronze structure (B)). Titanium dioxide having a rutile structure or anatase structure can represent the composition before charging with TiO ₂ . Since irreversible lithium may remain in the titanium dioxide after the battery is charged / discharged, the titanium dioxide after the battery is charged / discharged is preferably Li _x TiO ₂ (0 ≦ x, more preferably Can be represented by 0 <x ≦ 1).

Examples of niobium titanium oxide include Li _a TiM _b Nb _{2 ± β} O _{7 ± σ} (0 ≦ a ≦ 5, 0 ≦ b ≦ 0.3, 0 ≦ β ≦ 0.3, 0 ≦ σ ≦ 0.3). , M includes one represented by one or more elements selected from the group consisting of Fe, V, Mo, and Ta.

  The negative electrode including the negative electrode active material can include, for example, a negative electrode current collector and a negative electrode material layer including a negative electrode active material, a conductive agent, and a binder. The negative electrode material layer has a porous structure and can be supported on one side or both sides of the negative electrode current collector.

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

As the conductive agent, for example, acetylene black, carbon black, coke, carbon fiber, graphite, Li ₄ Ti ₅ O ₁₂ , metal compound powder, metal powder, or the like can be used alone or in combination. Examples of more preferable conductive agents include carbon fibers having a fiber diameter of 1 μm or less, coke having a heat treatment temperature of 800 ° C. to 2000 ° C. and an average particle diameter of 10 μm or less, graphite, acetylene black, TiO, TiC, TiN, Al, Ni, Cu, Metal powder such as Fe can be mentioned. A conductive agent containing carbon fiber having a fiber diameter of 1 μm or less or Li ₄ Ti ₅ O ₁₂ can reduce electrode resistance and improve cycle life performance.

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

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

The specific surface area of the negative electrode is preferably in the range of 1 to ²⁰ m ² / g. Within this range, reductive decomposition of the non-aqueous electrolyte in a high temperature environment can be suppressed, so that the cycle life can be improved. Here, the specific surface area of the negative electrode means the surface area per 1 g of the negative electrode material layer (excluding the weight of the current collector).

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

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

According to the negative electrode active material of the first embodiment described above, particles represented by Li _{2 + a Ad} Ti _6-b B _b O _14-c and a carbon material covering at least a part of the particle surface. Therefore, the high-temperature cycle life performance and large current discharge performance of the nonaqueous electrolyte battery can be improved.
(Second Embodiment)
The nonaqueous electrolyte battery according to the second embodiment includes a positive electrode, a negative electrode including the negative electrode active material of the first embodiment, and a nonaqueous electrolyte. The nonaqueous electrolyte battery can further include a separator disposed between the positive electrode and the negative electrode, and an exterior member.

  The form of the nonaqueous electrolyte battery may be a square battery, a cylindrical battery, or a thin battery. As the exterior member, a metal container, a laminate film container including a metal layer and a resin layer, or the like can be used. A laminate film container is more preferable because it can reduce the weight.

Hereinafter, each member will be described.
(Positive electrode)
The positive electrode includes a positive electrode active material. Examples of the positive electrode active material include lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, lithium cobalt aluminum composite oxide, lithium nickel aluminum composite oxide, lithium nickel cobalt manganese composite oxide, spinel. Type lithium manganese nickel composite oxide, lithium manganese cobalt composite oxide, olivine type lithium phosphorus oxide, and fluorinated iron sulfate. According to these, a high positive electrode voltage can be obtained.

Examples of the lithium manganese composite oxide include Li _x Mn ₂ O ₄ and Li _x MnO ₂ (0 ≦ x ≦ 1). Examples of the lithium nickel aluminum composite oxide include Li _x Ni _1-y Al _y O ₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1 (more preferably 0 <y <1)). Examples of the lithium cobalt composite oxide include Li _x CoO ₂ (0 ≦ x ≦ 1). Examples of the lithium nickel cobalt composite oxide include Li _x Ni _1-yz Co _y Mn _z O ₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1 (more preferably 0 <y <1 ), 0 ≦ z ≦ 1 (more preferably 0 <z <1)). Examples of the lithium manganese cobalt composite oxide include Li _x Mn _y Co _1-y O ₂ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1 (more preferably 0 <y <1)). Examples of the spinel type lithium manganese nickel composite oxide include Li _x Mn _2-y Ni _y O ₄ (0 ≦ x ≦ 1, 0 ≦ y ≦ 2 (more preferably 0 <y <2)). . Examples of the lithium phosphates having an olivine _{structure, Li x FePO 4, Li x} MnPO 4, Li x Fe 1-y Mn y PO 4, Li x CoPO 4 (0 ≦ x ≦ 1,0 ≦ y ≦ 1 (More preferably 0 <y <1)), and fluorinated iron sulfate (for example, Li _x FeSO ₄ F (0 ≦ x ≦ 1)). Note that when x is 1, lithium is completely released from the positive electrode active material by charging.

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

  The form of the positive electrode active material may be single primary particles, secondary particles, or a mixture of single primary particles and secondary particles. The average particle diameter (diameter) of the primary particles can be 1 μm or less, and a more preferable range is 0.05 to 0.5 μm.

It is preferable that at least a part of the particle surface of the positive electrode active material is coated with a carbon-containing material. Thereby, the electronic conductivity of the positive electrode active material particles can be improved. The carbon material is preferably a carbonaceous material having a (002) plane spacing d ₀₀₂ of 0.344 nm or more by powder X-ray diffraction. Since such a carbonaceous material can be produced at a firing temperature as low as about 700 ° C., the crystallinity of the positive electrode active material particles does not become too high, and the lithium occlusion / release performance of the positive electrode active material particles can be improved. it can.

As a preferred positive electrode active material, a first positive electrode active material (fluorinated sulfuric acid compound) represented by Li _x Fe _1-w Mn _w SO ₄ F (0 ≦ x ≦ 1.1, 0 ≦ w ≦ 0.2) Li _x Fe ₁ -yz Mn _y M _z PO ₄ (M is at least one element selected from the group consisting of Mg, Al, Ti and Zr, 0 ≦ x ≦ 1.1, 0 ≦ y) ≦ 1, 0 ≦ z ≦ 0.2) using the second positive electrode active material (phosphate compound of olivine structure) or both the first positive electrode active material and the second positive electrode active material Is mentioned. Thereby, the decomposition reaction of the nonaqueous electrolyte in a high temperature environment can be suppressed, and the charge / discharge cycle life of the battery can be greatly improved.

You may add the oxide of the at least 1 sort (s) of metal selected from the group which consists of cobalt, nickel, and manganese to the positive electrode containing a 2nd positive electrode active material. Preferred examples of the metal oxide include Li _x CoO ₂ (0 <x <1), LiNi _1-e Co _e Mn _f O ₂ (0 <e <1, 0 <f <1), Li _x Mn ₂ O ₄ (0 <x <1) and the like are included. By adding 30% by weight or less of metal oxide, the electrode density is increased and the volume specific capacity of the electrode is improved. The kind of metal oxide to be used can be one kind or two kinds or more.

  The operating voltage of the nonaqueous electrolyte battery according to the embodiment including the positive electrode including the first positive electrode active material and / or the second positive electrode active material and the negative electrode including the negative electrode active material of the first embodiment is When the positive electrode active material is included, the voltage is 2.5 to 1.6 V (intermediate voltage 2.17 V), and when the second positive electrode active material is included, the voltage is 3 to 1.8 V (intermediate voltage 2.66 to 2 V). When both the first positive electrode active material and the second positive electrode active material are included, the intermediate voltage is 2.4 to 2.05 V.

  The non-aqueous electrolyte battery of the embodiment can increase the average operating voltage by about 0.15 V to 0.5 V compared to the non-aqueous electrolyte battery using only lithium titanium oxide or titanium dioxide as the negative electrode active material. As a result, when the assembled battery is configured by connecting the nonaqueous electrolyte batteries of the embodiment in series, a high assembled battery voltage can be obtained with a small number of batteries, and thus the battery pack can be reduced in size and weight.

  The operating range of the assembled battery in which the nonaqueous electrolyte batteries of the embodiment are in series or 6 in series is in the range of 15V to 10V, and a parallel system with a lead storage battery or a lead storage battery can be substituted. Since this assembled battery can take out high output and large current discharge in the range of 15V to 10V, more preferably in the range of 15V to 13V, it can be used as a battery pack for idling stop vehicles with regenerative function (ISS) and micro hybrid vehicles. Best to use. In addition, the battery pack including the assembled battery according to the embodiment can be installed in the engine room of the automobile because of high temperature durability and high safety, and can improve the living space of the automobile. Similarly, since the operating range of the assembled battery in which the nonaqueous electrolyte battery of the embodiment is 18 series to 24 series can be adapted to the range of 54V to 24V, it is optimal for a micro hybrid vehicle.

  The positive electrode can include a positive electrode current collector and a positive electrode material layer including a positive electrode active material, a conductive agent, and a binder. The positive electrode material layer has a porous structure and can be supported on one side or both sides of the positive electrode current collector.

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

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

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

  The positive electrode is produced, for example, by suspending a positive electrode active material, a conductive agent, and a binder in an appropriate solvent, applying the suspension to a positive electrode current collector, drying, and pressing.

The specific surface area by the BET method of the positive electrode material layer is measured in the same manner as the negative electrode, and is preferably in the range of 0.1 to 10 m ² / g.

Examples of the positive electrode current collector include an aluminum foil and an aluminum alloy foil. The thickness of the positive electrode current collector can be 20 μm or less, and a more preferable range is 15 μm or less.
(Nonaqueous electrolyte)
The non-aqueous electrolyte is a liquid, gel, or solid electrolyte having lithium ion conductivity or sodium ion conductivity. Examples of liquid nonaqueous electrolytes include organic electrolytes and ionic liquids. Examples of the gel-like non-aqueous electrolyte include a gel-like organic electrolyte obtained by combining a liquid organic solvent and a polymer material. Examples of the solid non-aqueous electrolyte include a polymer solid electrolyte and an inorganic solid electrolyte.

  The liquid non-aqueous electrolyte is prepared by, for example, dissolving a lithium electrolyte in an organic solvent at a concentration of 1.5 to 3 mol / L. Thereby, a high output can be taken out even in a low temperature environment. If it is smaller than this range, the lithium ion concentration at the interface between the positive electrode and the non-aqueous electrolyte may be drastically reduced during discharge with a large current, and the output may be reduced. On the other hand, when the concentration exceeds 3 mol / L, the viscosity of the non-aqueous electrolyte increases, so that the migration rate of lithium ions decreases and the output may decrease. A more preferable range of the concentration is 0.5 to 2.5 mol / L. A sodium salt may be used in place of the lithium electrolyte.

Examples of the lithium electrolyte include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _2. , Li (CF ₃ SO ₂ ) ₃ C, LiB [(OCO) ₂ ] _{2 and the} like. The type of electrolyte used can be one type or two or more types. Among _them, LiPF _6, LiBF 4, LiN preferably contains _{(FSO 2)} 2. Thereby, the chemical stability of the organic solvent is increased, the film resistance on the negative electrode can be reduced, and the low temperature performance and cycle life performance can be greatly improved.

  Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC), chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC), dimethoxyethane ( Chain ethers such as DME) and dietoethane (DEE), cyclic ethers such as tetrahydrofuran (THF) and dioxolane (DOX), γ-butyrolactone (GBL), 2-methyl-γ-butyrolactone (MBL), acetonitrile (AN), Examples include 3-methoxypropiononitrile (MOPN) and sulfolane (SL). These organic solvents can be used alone or in the form of a mixture of two or more. In particular, propylene carbonate (PC), ethylene carbonate (EC), or γ-butyrolactone (GBL) is mainly used because the boiling point becomes 200 ° C. or higher and the thermal stability becomes high. In particular, by containing γ-butyrolactone (GBL), 2-methyl-γ-butyrolactone (MBL) or 3-methoxypropiononitrile (MOPN), it becomes possible to dissolve and use a high concentration lithium salt. In addition, stability (high boiling point, high flash point, low vapor pressure) in a high temperature environment is high, and output performance in a low temperature environment is also high.

  Examples of the ionic liquid include a room temperature molten salt (ionic melt) containing lithium ions. The room temperature molten salt (ionic melt) is preferably composed of lithium ions, organic cations and anions. The room temperature molten salt is preferably liquid at room temperature or lower. Hereinafter, an electrolyte containing a room temperature molten salt will be described.

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

  Examples of the organic cation include alkyl imidazolium ions and quaternary ammonium ions having a skeleton shown in Chemical Formula 1 below.

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

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

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

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

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

Examples of the solid non-aqueous electrolyte include a composite of lithium metal oxide, lithium metal sulfide, or lithium salt electrolyte and a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.
(Separator)
A separator can be disposed between the positive electrode and the negative electrode. The form of the separator includes a nonwoven fabric and a porous membrane. Further, the separator material includes cellulose and polyolefin. The type of material used can be one type or two or more types. Preferred separators include nonwoven fabrics or porous membranes containing cellulose or polyolefin with a thickness of 30 μm or less and a porosity of 50% or more. In particular, it is preferable to use a cellulose fiber separator having a porosity of 60% or more. This separator has good electrolyte impregnation properties and can provide high output performance from low to high temperatures. Moreover, by combining with the negative electrode of the embodiment, even when the porosity is 60% or more, it does not react with the negative electrode even during long-term charge storage, float charge, and overcharge, and the negative electrode and the positive electrode are short-circuited by dendri deposition of lithium metal. There is no problem. A more preferable range of the porosity is 62% to 80%. The diameter of the cellulose fiber is preferably 10 μm or less. Thereby, affinity with a nonaqueous electrolyte improves and battery resistance can be made small. A more preferable range is 3 μm or less. Examples of the separator include non-woven fabric, film, and paper.
The separator preferably has a thickness of 20 to 100 μm and a density of 0.2 to 0.9 g / cm ³ . Within this range, it is possible to balance mechanical strength and battery resistance reduction, and it is possible to provide a battery that is high in output and difficult to short-circuit internally. Moreover, there is little heat shrinkage in a high temperature environment, and good high temperature storage performance can be obtained.
(Exterior material)
Examples of the exterior member include a laminate film container having a wall thickness of 0.2 mm or less and a metal container having a wall thickness of 0.5 mm or less. The shape of the container depends on the form of the nonaqueous electrolyte battery. Examples of the nonaqueous electrolyte battery include a flat battery, a square battery, a cylindrical battery, a coin battery, a button battery, a sheet battery, a stacked battery, a large battery mounted on an electric vehicle, and the like.

  A more preferable range of the thickness of the laminate film is 0.5 mm or less. Moreover, it is desirable that the lower limit value of the thickness of the laminate film be 0.01 mm.

  On the other hand, the more preferable range of the plate thickness of the metal container is 0.5 mm or less. Further, the lower limit value of the plate thickness of the metal container is desirably 0.05 mm.

  Examples of the laminate film include a multilayer film including a metal layer and a resin layer that covers the metal layer. In order to reduce the weight, the metal layer is preferably an aluminum foil or an aluminum alloy foil. The resin layer is for reinforcing the metal layer, and can be formed of a polymer such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET). One or more types of resin can be used.

  A laminate film container can be obtained, for example, by laminating a laminate film by thermal fusion.

  The metal container is preferably made of aluminum or an aluminum alloy. The strength is increased by a metal container made of an aluminum alloy, and sufficient mechanical strength can be ensured even if the thickness of the container is reduced. Thereby, since the heat dissipation of a container can be improved, the raise of battery temperature can be suppressed. Further, the energy density can be improved to reduce the weight and size of the battery. These features are suitable for batteries that require high temperature conditions, high energy density, and the like, for example, in-vehicle batteries. As the aluminum alloy, an alloy containing at least one element selected from magnesium, zinc, silicon and the like is preferable. On the other hand, it is preferable that the content of transition metals such as iron, copper, nickel, and chromium in aluminum and aluminum alloy is 100 ppm or less.

  The metal container can be sealed with a laser. For this reason, the volume of a sealing part can be decreased compared with the container made from a laminate film, and an energy density can be improved.

  The non-aqueous electrolyte battery of the embodiment can be applied to various forms of non-aqueous electrolyte batteries such as a square, cylindrical, flat, thin, coin type, etc. Examples include a rectangular battery or a cylindrical battery using a manufactured exterior member, and a thin battery using a laminated film exterior member.

  1 and 2 show an example of a non-aqueous electrolyte battery using a laminate-fill container.

  The laminated electrode group 1 is housed in a bag-like container 2 made of a laminate film having a metal layer interposed between two resin films. As shown in FIG. 2, the stacked electrode group 1 has a structure in which positive electrodes 3 and negative electrodes 4 are alternately stacked with separators 5 interposed therebetween. There are a plurality of positive electrodes 3, each of which includes a current collector 3 a and a positive electrode active material-containing layer 3 b formed on both surfaces of the current collector 3 a. A plurality of negative electrodes 4 are present, each including a current collector 4a and a negative electrode active material-containing layer 4b formed on both surfaces of the current collector 4a. One side of the current collector 4 a of each negative electrode 4 protrudes from the positive electrode 3. The protruding current collector 4 a is electrically connected to the strip-shaped negative electrode terminal 6. The tip of the strip-like negative electrode terminal 6 is drawn out from the container 2 to the outside. Although not shown, the current collector 3a of the positive electrode 3 has a side protruding from the negative electrode 4 on the side opposite to the protruding side of the current collector 4a. The current collector 3 a protruding from the negative electrode 4 is electrically connected to the belt-like positive electrode terminal 7. The tip of the strip-like positive electrode terminal 7 is located on the opposite side to the negative electrode terminal 6 and is drawn out from the side of the container 2 to the outside.

  3 and 4 show an example of a non-aqueous electrolyte battery using a metal container.

  The electrode group 11 is housed in a rectangular cylindrical metal container 12. The electrode group 11 has a structure in which a positive electrode 13 and a negative electrode 14 are wound in a spiral shape so that a flat shape is formed with a separator 15 interposed therebetween. A nonaqueous electrolyte (not shown) is held by the electrode group 11. As shown in FIG. 4, a strip-like positive electrode lead 16 is electrically connected to each of a plurality of locations at the end of the positive electrode 13 located on the end face of the electrode group 1. In addition, a strip-like negative electrode lead 17 is electrically connected to each of a plurality of locations at the end of the negative electrode 14 located on this end face. The plurality of positive electrode leads 16 are electrically connected to the positive electrode conductive tab 18 in a bundled state. A positive electrode terminal is constituted by the positive electrode lead 16 and the positive electrode conductive tab 18. The negative electrode lead 17 is connected to the negative electrode conductive tab 19 in a bundled state. The negative electrode lead 17 and the negative electrode conductive tab 19 constitute a negative electrode terminal. The metal sealing plate 20 is fixed to the opening of the metal container 12 by welding or the like. The positive electrode conductive tab 18 and the negative electrode conductive tab 19 are each drawn out from an extraction hole provided in the sealing plate 20. The inner peripheral surface of each extraction hole of the sealing plate 20 is covered with an insulating member 21 in order to avoid a short circuit due to contact with the positive electrode conductive tab 18 and the negative electrode conductive tab 19.

According to the nonaqueous electrolyte battery of the second embodiment described above, since the negative electrode including the negative electrode active material according to the first embodiment is included, high-temperature cycle life performance and large current discharge performance can be improved.
(Third embodiment)
According to the third embodiment, it is possible to provide an assembled battery having a nonaqueous electrolyte battery as a unit cell and a battery pack including the assembled battery. As the nonaqueous electrolyte battery, the nonaqueous electrolyte battery of the second embodiment can be used.

  Examples of the assembled battery include a plurality of unit cells electrically connected in series or in parallel as a constituent unit, a unit composed of a plurality of unit cells electrically connected in series, or electrically connected in parallel Examples include a unit including a unit composed of a plurality of unit cells.

  Examples of embodiments in which a plurality of non-aqueous electrolyte batteries are electrically connected in series or in parallel include those in which a plurality of batteries each equipped with a container are electrically connected in series or in parallel, accommodated in a common housing What includes a plurality of electrode groups electrically connected in series or in parallel is included. In the former specific example, the positive terminals and the negative terminals of a plurality of nonaqueous electrolyte batteries are connected by a metal bus bar (for example, aluminum, nickel, copper). In the latter specific example, a plurality of electrode groups are accommodated in a single casing in an electrochemically insulated state by partition walls, and these electrode groups are electrically connected in series. By setting the number of electrically connected batteries in the range of 5 to 7, the voltage compatibility with the lead storage battery is improved. In order to further increase the voltage compatibility with the lead storage battery, a configuration in which five or six unit cells are connected in series is preferable.

  A metal can, a plastic container, or the like made of aluminum alloy, iron, stainless steel, or the like can be used for a housing in which the assembled battery is stored. Further, the plate thickness of the container is desirably 0.5 mm or more.

An example of the assembled battery will be described with reference to FIG. Assembled battery 31 shown in FIG. 5 includes a plurality of nonaqueous electrolyte batteries 321 _to 323 ₅ of the square of the second embodiment as the unit cell. A battery 32 ₁ of the positive electrode conductive tab 18 and the negative electrode conductive tab 19 of the battery 32 ₂ located next to it, are electrically connected by a lead 33. Further, a negative electrode conductive tab 19 of the battery 32 ₃ positioned positive electrode conductive tab 18 of the battery 32 ₂ next to it, are electrically connected by a lead 33. Thus between the battery ₃₂₁ to 323 ₅ are connected in series.

An example of a battery pack provided with an assembled battery made up of the nonaqueous electrolyte battery shown in FIGS. 1 and 2 will be described with reference to FIG. The battery pack 40 includes a housing 41 and an assembled battery 42 accommodated in the housing 41. Battery pack 42 is to nonaqueous electrolyte battery 43 _{1-43 5} a plurality (e.g. five) are electrically connected in series. A nonaqueous electrolyte battery ₄₃ 1-43 ₅ is laminated in the thickness direction. The housing 41 has an opening 44 on each of the upper part and the four side surfaces. Side nonaqueous electrolyte battery ₄₃ 1-43 ₅ positive and negative terminals 7,6 are protruded is exposed to the opening 44 of the housing 41. Output positive terminal of the assembled battery 42 45 form a strip, one end is electrically connected to one of the positive terminal 7 of the nonaqueous electrolyte battery 43 _{1-43 5,} and the other end of the housing 41 opening 44 protrudes from the upper portion of the housing 41. On the other hand, the output negative terminal 46 of the assembled battery 42, without a band, one end of which is connected one of the negative electrode terminal 6 and the electrically non-aqueous electrolyte battery 43 _{1-43 5,} and the other end of the housing 41 It protrudes from the opening 44 and protrudes from the upper part of the housing 41.

  Another example of the battery pack will be described in detail with reference to FIGS. A plurality of unit cells 51 composed of a flat type non-aqueous electrolyte battery are stacked so that the negative electrode terminal 52 and the positive electrode terminal 53 extending to the outside are aligned in the same direction, and are assembled by fastening with an adhesive tape 54. A battery 55 is configured. These unit cells 51 are electrically connected to each other in series as shown in FIG.

  The printed wiring board 56 is disposed to face the side surface of the unit cell 51 from which the negative electrode terminal 52 and the positive electrode terminal 53 extend. As shown in FIG. 8, a thermistor 57, a protection circuit 58, and a terminal 59 for energizing external devices are mounted on the printed wiring board 56. An insulating plate (not shown) is attached to the surface of the printed wiring board 56 facing the assembled battery 55 in order to avoid unnecessary connection with the wiring of the assembled battery 55.

  The positive electrode lead 60 is connected to the positive electrode terminal 53 located at the lowermost layer of the assembled battery 55, and the tip thereof is inserted into and electrically connected to the positive electrode connector 61 of the printed wiring board 56. The negative electrode lead 62 is connected to the negative electrode terminal 52 located on the uppermost layer of the assembled battery 55, and the tip thereof is inserted into and electrically connected to the negative electrode side connector 63 of the printed wiring board 56. These connectors 61 and 63 are connected to the protection circuit 58 through wirings 64 and 65 formed on the printed wiring board 56.

  The thermistor 57 detects the temperature of the unit cell 51, and the detection signal is transmitted to the protection circuit 58. The protection circuit 58 can cut off the plus wiring 66a and the minus wiring 66b between the protection circuit 58 and the energization terminal 59 to the external device under a predetermined condition. The predetermined condition is, for example, when the temperature detected by the thermistor 57 is equal to or higher than a predetermined temperature. The predetermined condition is when an overcharge, overdischarge, overcurrent, or the like of the unit cell 51 is detected. This detection of overcharge or the like is performed for each unit cell 51 or the assembled battery 55. When detecting each unit cell 51, 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 unit cell 51. 7 and 8, a voltage detection wiring 67 is connected to each unit cell 51, and a detection signal is transmitted to the protection circuit 58 through the wiring 67.

  Protective sheets 68 made of rubber or resin are disposed on the three side surfaces of the assembled battery 55 excluding the side surfaces from which the positive electrode terminal 53 and the negative electrode terminal 52 protrude.

  The assembled battery 55 is stored in a storage container 69 together with each protective sheet 68 and the printed wiring board 56. That is, the protective sheet 68 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 69, and the printed wiring board 56 is disposed on the inner side surface on the opposite side in the short side direction. The assembled battery 55 is located in a space surrounded by the protective sheet 68 and the printed wiring board 56. The lid 70 is attached to the upper surface of the storage container 69.

  In addition, instead of the adhesive tape 54, a heat shrink tape may be used for fixing the assembled battery 55. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the assembled battery.

  7 and 8 show the configuration in which the unit cells 51 are connected in series, but in order to increase the battery capacity, they may be connected in parallel. The assembled battery packs can be connected in series or in parallel.

  Moreover, the aspect of a battery pack is changed suitably by a use. As a use of the battery pack, one in which charging / discharging with a large current is desired is preferable. Specific examples include a power source for a digital camera, a vehicle for a two- to four-wheel hybrid electric vehicle, a two- to four-wheel electric vehicle, an assist bicycle, and the like. In particular, the vehicle-mounted one is suitable.

According to the third embodiment described above, since the nonaqueous electrolyte battery according to the second embodiment is used, the assembled battery and the battery pack with improved charge / discharge cycle life performance and high current discharge performance under a high temperature environment Can be provided. For this reason, it becomes possible to provide an assembled battery and a battery pack suitable as an alternative power source for a lead battery used as a starter power source for a vehicle or as an in-vehicle secondary battery mounted on a hybrid vehicle.
[Example]
Hereinafter, examples will be described in detail with reference to the drawings. However, the present invention is not limited to the examples described below.

Example 1
LiMn _0.85 Fe _0.1 Mg _0.05 PO having an olivine structure with an average particle diameter of 50 nm of primary particles in which carbon material particles (average particle diameter of 5 nm) are attached to the surface of the positive electrode active material (average particle diameter of 5 nm). ₄ is used, and as a conductive agent, 3% by weight of vapor-grown carbon fiber having a fiber diameter of 0.1 μm with respect to the whole positive electrode, 5% by weight of graphite powder, and 5% by weight of the whole positive electrode as a binder. % PVdF was mixed and dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a slurry, which was then coated on both sides of a 15 μm thick aluminum alloy foil (purity 99%), dried, and subjected to a pressing process. The positive electrode material layer on one side had a thickness of 43 μm and an electrode density of 2.2 g / cm ³ . The specific surface area of the positive electrode material layer was 5 m ² / g.

The negative electrode active material was produced by the following method. A raw material prepared by adjusting SrCO ₃ , TiO _2, and Li ₂ CO ₃ to a stoichiometric ratio was subjected to a temporary baking treatment at 650 ° C. for 2 hours, and then a sample powder was obtained by pulverization. After spraying a mixture of the sample powder and the polyvinyl alcohol liquid of the carbon precursor, drying was performed. The obtained powder was subjected to a main firing treatment at 1100 ° C. in an inert atmosphere in an argon stream to obtain a negative electrode active material powder.
By subjecting the obtained negative electrode active material powder to X-ray diffraction and elemental analysis, the negative electrode active material has a surface of Li ₂ SrTi ₆ O _13.9 powder coated with a 1 wt% carbon material layer. The average particle diameter of the primary particles of the negative electrode active material is 0.8 μm, the true density of the negative electrode active material is 3.85 g / cm ³ (excluding the carbon material), and Li ₂ SrTi ₆ O _13.9 is a space group Cmca. It was confirmed that it had the following crystal structure. A negative active material, acetylene black powder as a conductive agent, graphite powder having an average particle diameter of 6 μm, and PVdF as a binder are blended in a weight ratio of 85: 6: 5: 4 to give n-methylpyrrolidone. A slurry was prepared by dispersing in (NMP) solvent and using a ball mill with stirring at a rotational speed of 1000 rpm and stirring time of 2 hours. The obtained slurry was applied to an aluminum alloy foil (purity 99.3%) having a thickness of 15 μm, dried, and subjected to a heating press process, whereby the thickness of the negative electrode material layer on one side was 59 μm and the electrode density was 2.8 g. A / cm ³ negative electrode was produced. Further, the BET specific surface area of the negative electrode material layer (surface area per 1 g of the negative electrode material layer) was 8 m ² / g.

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

  A laser diffraction distribution measuring device (Shimadzu SALD-300) was used for particle measurement of the negative electrode active material. First, about 0.1 g of a sample, a surfactant, and 1 to 2 mL of distilled water were added to a beaker and stirred sufficiently, then poured into a stirred water tank, and the luminous intensity distribution was measured 64 times at intervals of 2 seconds. Distribution data was obtained. After confirming from the electron micrograph that the negative electrode active material was primary particles, the D50 value of the particle size distribution was taken as the average particle size of the primary particles.

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

Two pieces of 1 g of powdered negative electrode active material or ² × ² cm ² negative electrodes were cut out and used as samples. A BET specific surface area measuring apparatus manufactured by Yuasa Ionics was used, and nitrogen gas was used as an adsorption gas.

  The porosity of the negative electrode is determined by comparing the volume of the negative electrode material layer with the volume of the negative electrode material layer when the porosity is 0%, and the increase from the volume of the negative electrode material layer when the porosity is 0% It is calculated by regarding it as a volume. Note that the volume of the negative electrode material layer is the sum of the volumes of the negative electrode material layers on both sides when the negative electrode material layers are formed on both sides of the current collector.

A battery was produced from the positive electrode and the negative electrode by the following method. After preparing an electrode group in which a positive electrode, a 12 μm-thick polyethylene porous film and a negative electrode are laminated, a strip-like positive electrode terminal is electrically connected to a plurality of positive electrode aluminum foil current collectors, and a plurality of negative electrode aluminum A strip-shaped negative electrode terminal was electrically connected to the foil current collector. This electrode group was inserted into a container (exterior member).
Lithium salt LiPF ₆ was dissolved at 1.5 mol / L in an organic solvent in which PC and DEC were mixed at a volume ratio of 2: 1 as a non-aqueous electrolyte to prepare a liquid non-aqueous electrolyte. The obtained non-aqueous electrolyte was poured into a container, and had the structure shown in FIG. 1 described above, and was a thin non-aqueous electrolyte having a laminate film molding size (cup size) of 6 mm in thickness, 70 mm in width, and 110 mm in height. A secondary battery was produced. In the obtained secondary battery, the negative electrode has a potential of 1.0 V (vs. Li ^/ Li ⁺ ) to 1.8 V (vs. Li) with respect to the electrode potential of the lithium metal during occlusion (charge) release (discharge) of lithium ions. / Li ⁺ ).
(Examples 2-16 and Comparative Examples 1-7)
Using the positive electrode active material and the negative electrode active material shown in Table 1 below, a nonaqueous electrolyte secondary battery was produced in the same manner as described in Example 1 above.

  Each of the obtained non-aqueous electrolyte secondary batteries of Examples and Comparative Examples was discharged at 25 ° C. at a constant current of 1 C (1 hour rate) up to 3 V in 90 minutes and then discharged at 1.5 C to 1 C. The capacity (Ah) and the open circuit voltage (V) at a discharge rate of 50% were measured. As a large current discharge performance, a capacity retention rate at 10 C discharge (capacity at 1 C discharge was taken as 100%) was measured. In the 60 ° C high-temperature cycle test, after charging to the maximum charging voltage of each battery at a constant current of 3C in an environment of 60 ° C, the discharge cycle was repeated at 3C up to 1.5V, reaching 80% capacity of the initial capacity. The cycle life was taken as the cycle life.

  The measurement results are shown in Table 1 below.

  As is clear from Table 1, the nonaqueous electrolyte secondary batteries of Examples 1 to 16 are excellent in 60 ° C. high-temperature cycle life performance as compared with Comparative Examples 1 to 7. In addition, the batteries of Examples 1 to 16 are excellent in discharge capacity, 50% discharge rate voltage (intermediate voltage), and 10C discharge maintenance rate. Therefore, according to Examples 1-16, it is possible to improve 60 degreeC high temperature cycle life performance, without impairing discharge capacity, the voltage of 50% discharge rate (intermediate voltage), and 10C discharge maintenance factor.

  Moreover, the assembled batteries 1 and 2 using each of the nonaqueous electrolyte secondary batteries of Examples and Comparative Examples as unit cells were produced. From the nonaqueous electrolyte secondary batteries of Examples 1 to 16, the unit cells were electrically connected in series of 5 or 6 in series, and assembled batteries 1 of Examples 17 to 32 were obtained. Moreover, from the nonaqueous electrolyte secondary battery of Examples 1-16, the unit cell was electrically connected in 18-24 series, and the assembled battery 2 of Examples 17-32 was obtained. On the other hand, from the nonaqueous electrolyte secondary batteries of Comparative Examples 1 to 7, unit cells were electrically connected in series in 5 to 7 to obtain assembled batteries 1 of Comparative Examples 8 to 14. From the nonaqueous electrolyte secondary batteries of Comparative Examples 1 to 7, unit cells were electrically connected in series 18 to 25 to obtain assembled batteries 2 of Comparative Examples 8 to 14.

  The obtained assembled batteries 1 of Examples 17 to 32 and Comparative Examples 8 to 14 were charged at a constant current of 1 C (1 hour rate) at 25 ° C. in 15 minutes to 15 V, and then discharged at 1 C to 10.5 V. The open circuit voltage (V) at a discharge rate of 50% was measured. Moreover, the capacity maintenance rate at the time of 10C discharge from the discharge rate 50% (capacity at the time of 1C discharge from the discharge rate 50% was set to 100%) was measured as a large current discharge performance. On the other hand, the assembled batteries 2 of Examples 17 to 32 and Comparative Examples 8 to 14 were charged at a constant current of 1 C (1 hour rate) at 25 ° C. in 90 minutes to 54 V, and then discharged at 1 C to 38 V. The open circuit voltage (V) at a discharge rate of 50% was measured. Moreover, the capacity maintenance rate at the time of 10C discharge from the discharge rate 50% (capacity at the time of 1C discharge from the discharge rate 50% was set to 100%) was measured as a large current discharge performance. The measurement results are shown in Table 2 below.

  As is apparent from Table 2, the 5-series or 6-series assembled battery 1 of Examples 17 to 32 has a high voltage equivalent to or higher than the 5-series to 7-series assembled battery 1 of Comparative Examples 8 to 14. And high current discharge performance. Moreover, the 18-24 series assembled battery 2 of Examples 17-32 can obtain a high voltage equal to or higher than the 18 series-25 series assembled battery 2 of Comparative Examples 8-14, and has a large current discharge performance. Is excellent.

In addition, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of 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 scope of claims of the present application will be appended.
[1] Li _{2 + a Ad} Ti _6-b B _b O _14-c (A is at least one element selected from the group consisting of Na, K, Mg, Ca, Ba and Sr, and B is a metal element other than Ti. A, b, c, and d satisfy 0 ≦ a ≦ 5, 0 ≦ b ≦ 6, 0 ≦ c ≦ 0.6, and 0 ≦ d ≦ 3),
A negative electrode active material comprising a carbon material covering at least a part of the surface of the particle.
[2] The negative electrode active material according to [1], wherein the content of the carbon material is in the range of 0.05% by weight to 5% by weight.
[3] a positive electrode;
A negative electrode comprising the negative electrode active material according to any one of [1] or [2];
A non-aqueous electrolyte battery comprising a non-aqueous electrolyte.
[4] The positive electrode includes a first positive electrode active material represented by Li _x Fe _1-w Mn _w SO ₄ F (0 ≦ x ≦ 1.1, 0 ≦ w ≦ 0.2), and Li _x Fe. _1-yz Mn _y M _z PO ₄ (M is at least one element selected from the group consisting of Mg, Al, Ti and Zr, 0 ≦ x ≦ 1.1, 0 ≦ y ≦ 1, 0 ≦ The nonaqueous electrolyte battery according to [3], including a second positive electrode active material represented by z ≦ 0.2).
[5] A battery pack including the assembled battery in which the nonaqueous electrolyte battery according to [3] or [4] is electrically connected in a range of 5 series, 6 series, or 18 series to 24 series.

DESCRIPTION OF SYMBOLS 1,11 ... Electrode group, 2 ... Exterior member, 3,13 ... Positive electrode, 3a ... Positive electrode collector, 3b ... Positive electrode active material containing layer, 4,14 ... Negative electrode, 4a ... Negative electrode collector, 4b ... Negative electrode active Substance-containing layer, 5, 15 ... separator, 6 ... negative electrode terminal, 7 ... positive electrode terminal, 12 ... metal container, 16 ... positive electrode lead, 17 ... negative electrode lead, 18 ... positive electrode conductive tab, 19 ... negative electrode conductive tab, 20 ... Sealing plate, 21 ... insulating member, 31 ... assembled battery, 32 _{1 to} 32 ₅ , 43 ₁ to 43 ₅ ... nonaqueous electrolyte battery, 33 ... lead, 40 ... battery pack, 41 ... housing, 42 ... assembled battery, 44 DESCRIPTION OF SYMBOLS ... Opening part, 45 ... Output positive terminal, 46 ... Output negative terminal, 51 ... Unit cell, 55 ... Assembly battery, 56 ... Printed wiring board, 57 ... Thermistor, 58 ... Protection circuit, 59 ... Current supply to external equipment Terminal.

Claims (5)

_{Li 2 + a A d Ti 6} -b B b O 14-c (A comprises at least one type of elemental selected from the group consisting of Na and K, B is at least one kind selected from the group consisting of Ta and Nb consists elemental, and a, b, represented by c and d are 0 ≦ a ≦ 5,0 <b < 6,0 ≦ c ≦ 0.6,0 < satisfy d ≦ 3) particles,
A negative electrode comprising a negative electrode active material, comprising a carbon material covering at least a part of the surface of the particle.   The negative electrode according to claim 1, wherein the content of the carbon material is in a range of 0.05% by weight to 5% by weight. 2. The negative electrode is used in a potential range of 2 V (vs. Li ^/ Li ⁺ ) to 0.5 V (vs. Li ^/ Li ⁺ ) with respect to an electrode potential of lithium metal during occlusion and release of lithium ions. Or the negative electrode of 2. The negative electrode according to claim 1, wherein a true density of the negative electrode active material excluding the carbon material is 3.5 to 4.8 g / cm ³ .   The negative electrode according to any one of claims 1 to 4, wherein the negative electrode active material is a primary particle alone, a secondary particle, or a mixture of a single primary particle and a secondary particle.