JP5833176B2 - Nonaqueous electrolyte battery and battery pack - Google Patents

Description

  Embodiments described herein relate generally to a nonaqueous electrolyte battery and a battery pack.

  In recent years, research and development of non-aqueous electrolyte batteries such as lithium ion secondary batteries have been actively promoted as high energy density batteries. Non-aqueous electrolyte batteries are expected as a power source for uninterruptible power supplies of hybrid vehicles, electric vehicles, and mobile phone base stations. Therefore, the nonaqueous electrolyte battery is also required to have other characteristics such as rapid charge / discharge characteristics and long-term reliability. For example, a non-aqueous electrolyte battery capable of rapid charge / discharge not only greatly shortens the charging time, but also improves the power performance of a hybrid vehicle or the like and efficiently recovers the regenerative energy of the power.

  In order to enable rapid charge / discharge, it is necessary that electrons and lithium ions can move quickly between the positive electrode and the negative electrode. In a battery using a carbon-based negative electrode, when rapid charge and discharge are repeated, dendritic deposition of metallic lithium occurs on the electrode, and there is a risk of heat generation or ignition due to an internal short circuit.

  Accordingly, a battery using a metal composite oxide as a negative electrode instead of a carbonaceous material has been developed. In particular, a battery using titanium oxide as a negative electrode has characteristics that it can be stably charged and discharged quickly and has a longer life than a carbon-based negative electrode.

  However, titanium oxide has a higher potential for metal lithium (noble) than carbonaceous material. Moreover, titanium oxide has a low capacity per weight. For this reason, the battery using titanium oxide for the negative electrode has a problem that the energy density is low.

For example, the electrode potential of titanium oxide is about 1.5 V with respect to metallic lithium, and is higher (noble) than the potential of the carbon-based negative electrode. The potential of the titanium oxide is electrochemically restricted because it is caused by an oxidation-reduction reaction between Ti ³⁺ and Ti ⁴⁺ when lithium is electrochemically inserted and desorbed. There is also a fact that rapid charge and discharge of lithium ions can be stably performed at a high electrode potential of about 1.5V. Therefore, it is substantially difficult to lower the electrode potential in order to improve the energy density.

On the other hand, regarding the capacity per unit weight, the theoretical capacity of titanium dioxide (anatase type) is about 165 mAh / g, and the theoretical capacity of lithium titanium composite oxide such as Li ₄ Ti ₅ O ₁₂ is also 180 mAh / g. Degree. On the other hand, the theoretical capacity of a general graphite electrode material is 385 mAh / g or more. Therefore, the capacity density of titanium oxide is significantly lower than that of the carbon-based negative electrode. This is due to the fact that there are few equivalent sites that occlude lithium in the crystal structure of the titanium oxide, and because the lithium is easily stabilized in the structure, the substantial capacity is reduced.

JP 2010-80188 A JP 2009-21102 A

Journal of Solid State Chemistry 53, pp144-147 (1984) M. GASPERIN, Journal of Solid State Chemistry 53, pp144-147 (1984) I. Beharouak and K. Amine, Electrochemistry Communications, 5, 435 (2003)

  An object of the present invention is to provide a nonaqueous electrolyte battery having excellent rapid charge / discharge performance and higher energy density, and a battery pack including the battery.

In one aspect, a non-aqueous electrolyte battery including an exterior member and a positive electrode, a negative electrode, and a non-aqueous electrolyte housed in the exterior member, wherein the exterior member is a laminate film having a thickness of 0.5 mm or less. A negative electrode layer comprising a negative electrode active material, a conductive agent, and a binder, a current collector, and a negative electrode layer selected from a laminate film container and a metal container having a thickness of 1 mm or less. The negative electrode active material includes Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3), wherein M1 is at least one selected from the group consisting of Zr, Si and Sn, and M2 is composed of V, Ta and Bi. A non-aqueous electrolyte battery that is at least one selected from the group is provided.

  In another aspect, a battery pack including the nonaqueous electrolyte battery is provided.

Schematic view showing the crystal structure of the monoclinic form TiNb ₂ O _7. The schematic diagram which looked at the crystal structure of FIG. 1 from the other direction. Sectional drawing of the flat type nonaqueous electrolyte battery which concerns on 2nd Embodiment. The expanded sectional view of the A section of FIG. The partial notch perspective view which shows typically the other flat type nonaqueous electrolyte battery which concerns on 2nd Embodiment. The expanded sectional view of the B section of FIG. The disassembled perspective view of the battery pack which concerns on 3rd Embodiment. The block diagram which shows the electric circuit of the battery pack of FIG. 2 is a powder X-ray diffraction pattern of the monoclinic complex oxide synthesized in Example 1. FIG. 4 is a powder X-ray diffraction pattern of the monoclinic complex oxide synthesized in Example 2. FIG. The powder X-ray diffraction pattern of the complex oxide synthesize | combined by the comparative example. The first charge / discharge curves obtained for Examples 1 and 2 and Comparative Example.

(First embodiment)
The battery active material according to the first embodiment is Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 A monoclinic complex oxide represented by ≦ δ ≦ 0.3). Here, the M1 is at least one selected from the group consisting of Zr, Si and Sn, and the M2 is at least one selected from the group consisting of V, Ta and Bi.

Such a monoclinic complex oxide has a lithium occlusion potential of about 1.5 V (vs. Li / Li ⁺ ), so that stable repeated rapid charge / discharge is possible.

As an example of the monoclinic complex oxide represented by Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} , a schematic diagram of the crystal structure of monoclinic TiNb ₂ O ₇ is shown in FIG. And 2.

As shown in FIG. 1, in the crystal structure of monoclinic TiNb ₂ O ₇ , metal ions 101 and oxide ions 102 constitute a skeleton structure portion 103. In the metal ions 101, Nb ions and Ti ions are randomly arranged at a ratio of Nb: Ti = 2: 1. The skeletal structure portions 103 are alternately arranged three-dimensionally, so that void portions 104 exist between the skeleton structure portions 103. The void 104 serves as a lithium ion host.

In FIG. 1, a region 105 and a region 106 are portions having two-dimensional channels in the [100] direction and the [010] direction. As shown in FIG. 2, each of the monoclinic TiNb ₂ O ₇ crystal structures has a void portion 107 in the [001] direction. The void portion 107 has a tunnel structure that is advantageous for conducting lithium ions, and serves as a conductive path in the [001] direction that connects the region 105 and the region 106. The presence of this conductive path enables lithium ions to move between the region 105 and the region 106.

  As described above, the crystal structure of the monoclinic complex oxide is a region having a two-dimensional channel in which the equivalent insertion space of lithium ions is large and structurally stable, and the diffusion of lithium ions is fast. And the conductive path in the [001] direction connecting them improves the insertion / extraction of lithium ions into / from the insertion space and effectively increases the insertion / desorption space of lithium ions. Thereby, it is possible to provide high capacity and high rate performance.

  The plane index of the crystal shown in the present embodiment has symmetry of the space group C2 / m, and is based on atomic coordinates described in Non-Patent Document 1 (Journal of Solid State Chemistry 53, pp144-147 (1984)). And indexing.

Furthermore, Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ of} this embodiment (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) In addition to the tetravalent cation selected from Ti, Zr, Si and Sn, the monoclinic complex oxide represented by the formula further includes a pentavalent cation selected from Nb, V, Ta and Bi. Is included.

  When lithium ions are inserted into the voids 104, the metal ions 101 constituting the skeleton are reduced to trivalent, and thereby the electrical neutrality of the crystal is maintained. In the monoclinic complex oxide of this embodiment, not only tetravalent cations are reduced from tetravalent to trivalent, but also pentavalent cations are reduced from pentavalent to trivalent. For this reason, compared with the compound containing only a tetravalent cation, the reduction valence per active material weight is large. Therefore, even if many lithium ions are inserted, the electrical neutrality of the crystal can be maintained. For this reason, an energy density can be raised compared with a compound like a titanium oxide containing only a tetravalent cation. As a result, the theoretical capacity of the monoclinic complex oxide of this embodiment is about 387 mAh / g, which is more than twice that of titanium oxide having a spinel structure.

Since Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} of this embodiment has one tetravalent cation and two pentavalent cations per chemical formula, theoretically, a maximum of 5 between the layers can be obtained. It is possible to insert two lithium ions. Thus, in the formula _{Li x Ti 1-y M1 y} Nb 2-z M2 z O 7 ± δ, x is 0 to 5. Further, δ varies depending on the reduction state of the monoclinic complex oxide. If δ exceeds −0.3, phase separation may occur. On the other hand, up to δ = + 0.3 is the measurement error range.

The monoclinic complex oxide in the present embodiment preferably contains Ti and Nb, and more preferably TiNb ₂ O ₇ . This is because, in the formula of the monoclinic complex oxide, when y = 0 and z = 0, the tetravalent cation is Ti ⁴⁺ and the pentavalent cation is Nb ⁵⁺ . It is an oxide. Since this can provide an ideal crystal lattice for conducting lithium ions, it is possible to further improve the rapid charge / discharge performance and the electrode capacity.

Furthermore, in the monoclinic complex oxide of the present embodiment, the highest intensity peak appears at 2θ = 26 ° ± 0.5 ° in the diffraction diagram of powder X-ray diffraction using a Cu—Kα ray source, In addition, it is preferable that two peaks appear at 2θ = 44 ° ± 1 °, and the intensity ratio (I _H / I _L ) of these two peaks is less than 1. Here, I _H is a peak on the high angle side, and I _L is a peak on the low angle side.

  The peak appearing at 2θ = 26 ° ± 0.5 ° is considered to be mainly the peak of the (0 0 3) plane. When the peak appearing at 2θ = 26 ° ± 0.5 ° is the highest intensity peak, it is assumed that the crystallite size of the (0 0 3) plane is large in the crystal structure, and the crystallites in the [001] direction Can be interpreted as growing. As described above, since the [001] direction is the only path connecting the upper and lower two-dimensional channels, the growth of this portion improves the insertion / extraction of lithium ions into the insertion space. At the same time, the insertion / desorption space for lithium ions effectively increases. Thereby, it is possible to provide a high charge / discharge capacity and a high rate performance. In addition, since lithium ion insertion / extraction is high, there is little loss of lithium and it is possible to provide excellent charge / discharge efficiency.

  Although it is considered that the peak of (1 1 1) plane may appear in the range of 2θ = 26 ° ± 0.5 °, the peak of (0 0 3) plane and (1 1 1) plane are In many cases, it is difficult to separate the peaks because the intervals are close.

  The two peaks appearing at 2θ = 44 ° ± 1 ° are the (0 0 5) plane peak on the low angle side and the (−10 0 3) plane peak on the high angle side. it is conceivable that.

When the peak intensity ratio (I _H / I _L ) is less than 1, a composite oxide having high lithium ion conductivity and high capacity can be obtained. Preferably, the peak intensity ratio (I _H / I _L ) is less than 1.0, more preferably 0.5 or less. The range where the two peaks appear is more preferably 2θ = 44 ° ± 1.0 °.

<Particle size and BET specific surface area>
The average particle diameter of the composite oxide in the present embodiment is not particularly limited, and can be changed according to desired battery characteristics. Furthermore, the BET specific surface area of the composite oxide in the present embodiment is not particularly limited, but is preferably 5 m ² / g or more and less than 200 m ² / g.

When the specific surface area is 5 m ² / g or more, a contact area with the electrolytic solution can be secured, good discharge rate characteristics can be easily obtained, and the charging time can be shortened. On the other hand, if the specific surface area is less than 200 m ² / g, the reactivity with the electrolytic solution does not become too high, and the life characteristics can be improved. Moreover, the coating property of the slurry containing an active material used for manufacturing the electrode described later can be improved.

  Here, the measurement of the specific surface area uses a method in which molecules having a known adsorption occupation area are adsorbed on the surface of the powder particles at the temperature of liquid nitrogen and the specific surface area of the sample is obtained from the amount. The BET method based on low-temperature and low-humidity physical adsorption of inert gas is the most widely used theory, which is the most famous theory for calculating specific surface area, which is an extension of the monolayer adsorption theory Langmuir theory to multi-layer adsorption. is there. The specific surface area determined in this way is referred to as the BET specific surface area.

<Manufacturing method>
The monoclinic complex oxide of this embodiment can be manufactured by the following method.
First, an oxide or salt containing at least one selected from the group consisting of Ti, Zr, Si and Sn, and an oxide containing at least one selected from the group consisting of Nb, V, Ta and Bi or The salt is represented by Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) Mix in a molar ratio so as to form a monoclinic complex oxide. The salt is preferably a salt such as carbonate and nitrate that decomposes at a relatively low temperature to produce an oxide.

  Next, the obtained mixture is pulverized, mixed so as to be as uniform as possible, and then fired. Firing is performed in a temperature range of 1000 to 1500 ° C. for a total of 10 to 40 hours.

The crystallinity is improved by increasing the firing temperature to a range of 1300 to 1500 ° C., and in the diffraction diagram of powder X-ray diffraction using a Cu—Kα ray source, 2θ = 26 ° ± 0.5 °. A monoclinic type composite in which the peak with the highest intensity appears and two peaks appear at 2θ = 44 ° ± 1 ° and the intensity ratio (I _H / I _L ) of these two peaks is less than 1 An oxide can be obtained.

  The monoclinic complex oxide synthesized as described above is inserted with lithium ions when charged. Alternatively, a monoclinic complex oxide containing lithium can be obtained in advance by using a compound containing lithium such as lithium carbonate as a synthetic raw material.

<Powder X-ray diffraction measurement>
The powder X-ray diffraction measurement of the active material is performed as follows. First, the target sample is pulverized until the average particle size becomes about 5 μm. The average particle diameter can be determined by a laser diffraction method. The crushed sample is filled in a holder portion having a depth of 0.2 mm formed on a glass sample plate. At this time, care should be taken so that the sample is sufficiently filled in the holder portion. Also, be careful that there are no cracks or voids due to insufficient filling of the sample. Next, using another glass plate from the outside, it is sufficiently pressed and smoothed. Be careful not to cause unevenness from the reference surface of the holder due to excessive or insufficient filling amount. Next, the glass plate filled with the sample is placed in a powder X-ray diffractometer, and a diffraction pattern is obtained using Cu-Kα rays.

  In addition, when the orientation of the sample is high, the position of the peak may be shifted or the intensity ratio may be changed depending on how the sample is filled. Such samples are measured in the form of pellets. The pellet may be a green compact having a diameter of 10 mm and a thickness of 2 mm, for example. The green compact can be produced by applying a pressure of about 250 MPa to the sample for 15 minutes. The obtained pellet is placed in an X-ray diffractometer and the surface is measured. By measuring by such a method, the difference in the measurement result by the operator can be eliminated and the reproducibility can be enhanced.

When powder X-ray diffraction measurement is performed on the active material contained in the electrode, for example, the following can be performed.
In order to grasp the crystal state of the active material, lithium ions are completely separated from the monoclinic compound. For example, when used as a negative electrode, the battery is completely discharged. However, residual lithium ions may exist even in a discharged state.

  The battery is then disassembled in a glove box filled with argon and washed with a suitable solvent. For example, ethyl methyl carbonate may be used. The washed electrode may be cut out to the same extent as the area of the holder of the powder X-ray diffractometer and directly attached to the glass holder for measurement. At this time, XRD is measured in advance according to the type of metal foil of the electrode substrate, and it is grasped at which position the peak derived from the substrate appears. In addition, the presence or absence of a peak of a mixture such as a conductive additive or a binder is also grasped in advance. When the peak of the substrate and the peak of the active material overlap, it is desirable to measure by peeling the active material from the substrate. This is for separating overlapping peaks when quantitatively measuring the peak intensity. Of course, this operation can be omitted if these are known in advance. The electrode may be physically peeled off, but is easily peeled off when ultrasonic waves are applied in a solvent. By measuring the electrode thus collected, powder X-ray diffraction measurement of the active material can be performed.

  The powder X-ray diffraction results thus obtained were analyzed by the Rietveld method. In the Rietveld method, parameters related to the crystal structure (lattice constant, atomic coordinates, occupancy, etc.) can be refined by fully fitting the diffraction pattern calculated from the crystal structure model estimated in advance with the actual measurement value. The characteristics of the crystal structure of the selected material can be investigated.

  According to the above embodiment, it is possible to provide a battery active material having excellent repeated rapid charge / discharge performance and a high energy density.

(Second Embodiment)
In the second embodiment, a nonaqueous electrolyte battery including a negative electrode including the battery active material in the first embodiment, a positive electrode, a nonaqueous electrolyte, a separator, and an exterior member is provided.

  Hereinafter, the negative electrode, the positive electrode, the nonaqueous electrolyte, the separator, and the exterior member will be described in detail.

1) Negative electrode The negative electrode includes a current collector and a negative electrode layer (negative electrode active material-containing layer). The negative electrode layer is formed on one side or both sides of the current collector, and includes an active material, and optionally a conductive agent and a binder.

The negative electrode active material includes Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} described in the first embodiment (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, A monoclinic complex oxide represented by 0 ≦ δ ≦ 0.3) is used. Here, M1 is at least one selected from the group consisting of Zr, Si and Sn, and M2 is at least one selected from the group consisting of V, Ta and Bi.

  A negative electrode using such a negative electrode active material has excellent rapid charge / discharge performance and can provide a non-aqueous electrolyte battery having a high energy density.

Also expressed by the above Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) In the monoclinic complex oxide, a peak of the highest intensity appears at 2θ = 26 ° ± 0.5 ° in a diffraction diagram of powder X-ray diffraction using a Cu—Kα ray source, and 2θ = 44. It is preferable to use a monoclinic complex oxide in which two peaks I _H and I _L appear at ° ± 1 ° and the intensity ratio (I _H / I _L ) of these two peaks is less than 1. Here, I _H is a peak on the high angle side, and I _L is a peak on the low angle side. Since the monoclinic complex oxide satisfying the above conditions has higher crystallinity, the negative electrode using such a negative electrode active material has better rapid charge / discharge performance and higher energy density. It is possible to provide a non-aqueous electrolyte battery having

The negative electrode active material is Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) Although the monoclinic complex oxide represented may be used alone, other active materials may be mixed and used. Examples of other active materials include titanium dioxide having anatase structure (TiO ₂ ), lithium titanate having a ramsdellite structure (eg, Li ₂ Ti ₃ O ₇ ), lithium titanate having a spinel structure (eg, Li ₄ Ti ₅ O ₁₂ ) is included.

  The conductive agent is blended in order to improve current collection performance and suppress contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black, and graphite.

  The binder is blended to fill a gap between the dispersed negative electrode active materials and bind the active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and styrene butadiene rubber.

  The active material, conductive agent and binder in the negative electrode layer are preferably blended in a proportion of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively. . By setting the amount of the conductive agent to 2% by mass or more, the current collecting performance of the negative electrode layer can be improved. Further, by setting the amount of the binder to 2% by mass or more, the binding property between the negative electrode layer and the current collector is sufficient, and excellent cycle characteristics can be expected. On the other hand, the conductive agent and the binder are each preferably 28% by mass or less in order to increase the capacity.

  As the current collector, a material that is electrochemically stable at the lithium insertion and extraction potential of the negative electrode active material is used. The current collector is preferably made of copper, nickel, stainless steel or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu and Si. The thickness of the current collector is preferably 5 to 20 μm. A current collector having such a thickness can balance the strength and weight reduction of the negative electrode.

  The negative electrode is prepared by, for example, suspending a negative electrode active material, a binder and a conductive agent in a commonly used solvent to prepare a slurry. The slurry is applied to a current collector, dried, a negative electrode layer is formed, and then pressed. It is produced by giving. The negative electrode may also be produced by forming a negative electrode active material, a binder, and a conductive agent into a pellet to form a negative electrode layer, which is disposed on a current collector.

2) Positive electrode The positive electrode includes a current collector and a positive electrode layer (positive electrode active material-containing layer). The positive electrode layer is formed on one side or both sides of the current collector, and includes an active material, and optionally a conductive agent and a binder.

For example, an oxide or a sulfide can be used as the active material. Examples of oxides and sulfides include manganese dioxide (MnO ₂ ) that occludes lithium, iron oxide, copper oxide, nickel oxide, lithium manganese complex 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 (eg LixCoO ₂ ), lithium nickel cobalt composite oxide (eg LiNi _1-y Co _y O ₂ ), lithium manganese cobalt composite oxide (eg _{Li x Mn y Co 1-y} O 2), lithium manganese nickel complex oxide having a spinel structure (e.g., _{Li x Mn 2-y Ni y} O 4), lithium phosphates having an olivine structure (e.g., 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 (for example, V ₂ O ₅ ), and lithium nickel cobalt manganese composite oxide Is included. In the above formula, 0 <x ≦ 1 and 0 <y ≦ 1. As the active material, these compounds may be used alone, or a plurality of compounds may be used in combination.

Examples of more preferable active materials include lithium manganese composite oxides (eg, Li _x Mn ₂ O ₄ ), lithium nickel composite oxides (eg, Li _x NiO ₂ ), and lithium cobalt composite oxides (eg, LixCoO ₂ ) having a high positive electrode voltage. ), Lithium nickel cobalt composite oxide (eg, LiNi _1-y Co _y O ₂ ), lithium manganese nickel composite oxide having a spinel structure (eg, Li _x Mn _2-y Ni _y O ₄ ), lithium manganese cobalt composite oxide (e.g. _{Li x Mn y Co 1-y} O 2), lithium iron phosphate (e.g. Li _x FePO _4), and includes a lithium-nickel-cobalt-manganese composite oxide. In the above formula, 0 <x ≦ 1 and 0 <y ≦ 1.

When normal temperature molten salt is used as the non-aqueous electrolyte of the battery, examples of preferable active materials include lithium iron phosphate, Li _x VPO ₄ F (0 ≦ x ≦ 1), lithium manganese composite oxide, lithium nickel composite oxide. And lithium nickel cobalt composite oxide. Since these compounds have low reactivity with room temperature molten salts, the cycle life can be improved.

  The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material having a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material having a primary particle size of 1 μm or less can smoothly diffuse lithium ions in a solid.

The specific surface area of the active material is preferably 0.1 m ² / g or more and 10 m ² / g or less. The positive electrode active material having a specific surface area of 0.1 m ² / g or more can sufficiently ensure the occlusion / release sites of lithium ions. The positive electrode active material having a specific surface area of 10 m ² / g or less is easy to handle in industrial production and can ensure good charge / discharge cycle performance.

  The binder is blended to bind the active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

  The conductive agent is blended as necessary in order to enhance the current collecting performance and suppress the contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black, and graphite.

  In the positive electrode layer, the active material and the binder are preferably blended in a proportion of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

  Sufficient electrode strength can be obtained by setting the binder to an amount of 2% by mass or more. Moreover, the content of the insulator of an electrode can be reduced by setting it as 20 mass% or less, and an internal resistance can be reduced.

  When a conductive agent is added, the active material, the binder and the conductive agent are blended in a proportion of 77% to 95% by weight, 2% to 20% by weight, and 3% to 15% by weight, respectively. It is preferable to do. The conductive agent can exhibit the above-described effects by adjusting the amount to 3% by mass or more. Moreover, by setting it as 15 mass% or less, decomposition | disassembly of the nonaqueous electrolyte on the surface of the positive electrode conductive agent under high temperature storage can be reduced.

  The current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

  The thickness of the aluminum foil or aluminum alloy foil is desirably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

  For the positive electrode, for example, an active material, a binder, and a conductive agent blended as necessary are suspended in a suitable solvent to prepare a slurry, and this slurry is applied to a positive electrode current collector and dried to form a positive electrode layer. After forming, it is produced by applying a press. The positive electrode may also be produced by forming a positive electrode layer by forming an active material, a binder, and a conductive agent blended as necessary into a pellet shape, and placing this on a current collector.

3) Nonaqueous electrolyte The nonaqueous electrolyte may be, for example, a liquid nonaqueous electrolyte prepared by dissolving an electrolyte in an organic solvent, or a gelled nonaqueous electrolyte obtained by combining a liquid electrolyte and a polymer material. .

  The liquid non-aqueous electrolyte is preferably one in which the electrolyte is dissolved in an organic solvent at a concentration of 0.5 mol / L or more and 2.5 mol / L or less.

Examples of electrolytes include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluorometa Lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ] and mixtures thereof are included. The electrolyte is preferably one that is not easily oxidized even at a high potential, and LiPF ₆ is most preferred.

  Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate; chain forms such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) Carbonates; tetrahydrofuran (THF), cyclic ethers such as 2methyltetrahydrofuran (2MeTHF), dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), Acetonitrile (AN) and sulfolane (SL) are included. These organic solvents can be used alone or as a mixed solvent.

  Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

  Alternatively, a non-aqueous electrolyte may be a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, or the like.

  A room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15 to 25 ° C.) among organic salts composed of a combination of an organic cation and an anion. The room temperature molten salt includes a room temperature molten salt that exists alone as a liquid, a room temperature molten salt that becomes liquid when mixed with an electrolyte, and a room temperature molten salt that becomes liquid when dissolved in an organic solvent. In general, the melting point of a room temperature molten salt used for a nonaqueous electrolyte battery is 25 ° C. or less. The organic cation generally has a quaternary ammonium skeleton.

The polymer solid electrolyte is prepared by dissolving an electrolyte in a polymer material and solidifying it.
The inorganic solid electrolyte is a solid material having lithium ion conductivity.

4) Separator The separator may be formed of, for example, a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. Especially, since the porous film formed from polyethylene or a polypropylene can melt | dissolve at a fixed temperature and can interrupt | block an electric current, safety | security can be improved.

5) Exterior member As the exterior member, a laminate film having a thickness of 0.5 mm or less or a metal container having a thickness of 1 mm or less can be used. The thickness of the laminate film is more preferably 0.2 mm or less. The metal container is more preferably 0.5 mm or less in thickness, and further preferably 0.2 mm or less in thickness.

  The shape of the exterior member may be a flat type (thin type), a square type, a cylindrical type, a coin type, a button type, or the like. The exterior member may be, for example, a small battery exterior member that is loaded on a portable electronic device or the like, or a large battery exterior member that is loaded on a two-wheel to four-wheel automobile or the like, depending on the battery size.

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

  The metal container is made of aluminum or an aluminum alloy. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. When the alloy contains a transition metal such as iron, copper, nickel, or chromium, the content is preferably 1% by mass or less.

6) Nonaqueous electrolyte secondary battery Next, the nonaqueous electrolyte battery according to the second embodiment will be described more specifically with reference to the drawings. FIG. 3 is a cross-sectional view of a flat type nonaqueous electrolyte secondary battery. FIG. 4 is an enlarged cross-sectional view of part A in FIG. Each figure is a schematic diagram for promoting the explanation of the embodiment and its understanding, and its shape, dimensions, ratio, etc. are different from the actual device, but these are considered in the following explanation and known techniques. Thus, the design can be changed as appropriate.

  The flat wound electrode group 1 is housed in a bag-shaped exterior member 2 made of a laminate film having a metal layer interposed between two resin layers. As shown in FIG. 4, the flat wound electrode group 1 is formed by winding a laminate of the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4 in this order from the outside in a spiral shape and press-molding. Is done.

  The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode layer 3b. The negative electrode layer 3b contains the above negative electrode active material. As shown in FIG. 4, the outermost negative electrode 3 has a configuration in which a negative electrode layer 3b is formed only on one surface on the inner surface side of the negative electrode current collector 3a. In the other negative electrode 3, negative electrode layers 3b are formed on both surfaces of the negative electrode current collector 3a.

  In the positive electrode 5, positive electrode layers 5b are formed on both surfaces of the positive electrode current collector 5a.

  As shown in FIG. 3, in the vicinity of the outer peripheral end of the wound electrode group 1, the negative electrode terminal 6 is connected to the negative electrode current collector 3 a of the outermost negative electrode 3, and the positive electrode terminal 7 is the positive electrode current collector of the inner positive electrode 5. It is connected to the body 5a. The negative electrode terminal 6 and the positive electrode terminal 7 are extended to the outside from the opening of the bag-shaped exterior member 2. For example, the liquid non-aqueous electrolyte is injected from the opening of the bag-shaped exterior member 2. The wound electrode group 1 and the liquid nonaqueous electrolyte are completely sealed by heat-sealing the opening of the bag-shaped exterior member 2 with the negative electrode terminal 6 and the positive electrode terminal 7 interposed therebetween.

  The negative electrode terminal 6 can be formed of a material that is electrochemically stable and has conductivity at the Li occlusion / release potential of the negative electrode active material described above. Specific examples include copper, nickel, stainless steel, and aluminum. The negative electrode terminal 6 is preferably formed of the same material as the negative electrode current collector 3a in order to reduce the contact resistance with the negative electrode current collector 3a.

  The positive electrode terminal 7 can be formed of, for example, a material having electrical stability and conductivity in a range where the potential with respect to the lithium ion metal is 3 V or more and 5 V or less. Specifically, it is formed from aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal 7 is preferably formed of the same material as the positive electrode current collector 5a in order to reduce the contact resistance with the positive electrode current collector 5a.

  The nonaqueous electrolyte battery according to the second embodiment is not limited to the one shown in FIGS. 2 and 3 described above, and may be a battery shown in FIGS. 5 and 6, for example. FIG. 5 is a partially cutaway perspective view schematically showing another flat type nonaqueous electrolyte secondary battery according to the second embodiment, and FIG. 6 is an enlarged cross-sectional view of a portion B in FIG.

  The laminated electrode group 11 is housed in an exterior member 12 made of a laminate film in which a metal layer is interposed between two resin films. As shown in FIG. 6, the stacked electrode group 11 has a structure in which positive electrodes 13 and negative electrodes 14 are alternately stacked with separators 15 interposed therebetween. There are a plurality of positive electrodes 13, each of which includes a current collector 13 a and a positive electrode active material-containing layer 13 b supported on both surfaces of the current collector 13 a. There are a plurality of negative electrodes 14, each including a negative electrode current collector 14 a and a negative electrode active material-containing layer 14 b supported on both surfaces of the negative electrode current collector 14 a. One side of the negative electrode current collector 14 a of each negative electrode 14 protrudes from the negative electrode 14. The protruding negative electrode current collector 14 a is electrically connected to the strip-shaped negative electrode terminal 16. The tip of the strip-shaped negative electrode terminal 16 is drawn out from the exterior member 11 to the outside. Although not shown, the positive electrode current collector 13a of the positive electrode 13 has a side protruding from the positive electrode 13 on the side opposite to the protruding side of the negative electrode current collector 14a. The positive electrode current collector 13 a protruding from the positive electrode 13 is electrically connected to the belt-like positive electrode terminal 17. The tip of the belt-like positive electrode terminal 17 is located on the opposite side to the negative electrode terminal 16 and is drawn out from the side of the exterior member 11 to the outside.

  According to the above embodiment, it is possible to provide a non-aqueous electrolyte battery having excellent repeated rapid charge / discharge performance and high energy density.

(Third embodiment)
Next, a battery pack according to a third embodiment will be described with reference to the drawings. The battery pack includes one or a plurality of nonaqueous electrolyte batteries (unit cells) according to the second embodiment. When a plurality of unit cells are included, each unit cell is electrically connected in series or in parallel.

  7 and 8 show an example of the battery pack 20. The battery pack 20 includes a plurality of flat batteries 21 having the structure shown in FIG. FIG. 7 is an exploded perspective view of the battery pack 20, and FIG. 8 is a block diagram showing an electric circuit of the battery pack 20 of FIG.

  The plurality of unit cells 21 are laminated so that the negative electrode terminal 6 and the positive electrode terminal 7 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 22 to constitute an assembled battery 23. These unit cells 21 are electrically connected to each other in series as shown in FIG.

  The printed wiring board 24 is disposed to face the side surface of the unit cell 21 from which the negative electrode terminal 6 and the positive electrode terminal 7 extend. As shown in FIG. 8, a thermistor 25, a protection circuit 26, and a terminal 27 for energizing external devices are mounted on the printed wiring board 24. Note that an insulating plate (not shown) is attached to the surface of the printed wiring board 24 facing the assembled battery 23 in order to avoid unnecessary connection with the wiring of the assembled battery 23.

  The positive electrode side lead 28 is connected to the positive electrode terminal 7 positioned at the lowermost layer of the assembled battery 23, and the tip thereof is inserted into the positive electrode side connector 29 of the printed wiring board 24 and electrically connected thereto. The negative electrode side lead 30 is connected to the negative electrode terminal 6 located in the uppermost layer of the assembled battery 23, and the tip thereof is inserted into the negative electrode side connector 31 of the printed wiring board 24 and electrically connected thereto. These connectors 29 and 31 are connected to the protection circuit 26 through wirings 32 and 33 formed on the printed wiring board 24.

  The thermistor 25 detects the temperature of the unit cell 21, and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the plus side wiring 34a and the minus side wiring 34b between the protection circuit 26 and the energization terminal 27 to the external device under a predetermined condition. The predetermined condition is, for example, when the temperature detected by the thermistor 25 is equal to or higher than a predetermined temperature. The predetermined condition is when the overcharge, overdischarge, overcurrent, etc. of the cell 21 are detected. This detection of overcharge or the like is performed for each single cell 21 or the entire single cell 21. When detecting each single cell 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 unit cell 21. In the case of FIG. 7 and FIG. 8, wiring 35 for voltage detection is connected to each single cell 21, and a detection signal is transmitted to the protection circuit 26 through these wirings 35.

  Protective sheets 36 made of rubber or resin are disposed on the three side surfaces of the assembled battery 23 excluding the side surfaces from which the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

  The assembled battery 23 is stored in a storage container 37 together with the protective sheets 36 and the printed wiring board 24. That is, the protective sheet 36 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 37, 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 23 is located in a space surrounded by the protective sheet 36 and the printed wiring board 24. The lid 38 is attached to the upper surface of the storage container 37.

  In addition, instead of the adhesive tape 22, a heat shrink tape may be used for fixing the assembled battery 23. 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.

  7 and 8 show the configuration in which the unit cells 21 are connected in series, but in order to increase the battery capacity, they may be connected in parallel. Alternatively, series connection and parallel connection may be combined. The assembled battery packs can be further connected in series or in parallel.

  Moreover, the aspect of a battery pack is changed suitably by a use. The battery pack according to the present embodiment is suitably used for applications that require excellent cycle characteristics when a large current is taken out. Specifically, it is used as a power source for a digital camera, or as an in-vehicle battery for, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, and an assist bicycle. In particular, it is suitably used as a vehicle-mounted battery.

  According to the above embodiment, it is possible to provide a battery pack having excellent repeated rapid charge / discharge performance and a high energy density.

  Hereinafter, based on an Example, the said embodiment is described in detail. The crystal phase of the synthesized monoclinic complex oxide and the crystal structure were estimated by powder X-ray diffraction using Cu-Kα rays. The composition of the product was analyzed by ICP method, and it was confirmed that the target product was obtained.

<Example 1>
(Synthesis)
Single unit represented by the general formula Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) TiNb ₂ O _{7 in} which x = 0, y = 0, and z = 0 was synthesized among the oblique complex oxides. Commercially available oxide reagents Nb ₂ O ₅ and TiO ₂ were used as starting materials. These powders were weighed to a molar ratio of 1: 1 and mixed in a mortar. Next, it was placed in an electric furnace and baked at 1250 ° C. for a total of 20 hours. The synthesis method used here is based on the method described in Non-Patent Document 2 (M. GASPERIN, Journal of Solid State Chemistry 53, pp144-147 (1984)).

(Powder X-ray diffraction measurement)
The obtained sample was subjected to powder X-ray diffraction measurement as follows. First, the sample was pulverized until the average particle size became about 10 μm. The crushed sample was filled in a holder portion having a depth of 0.2 mm formed on a glass sample plate. Next, another glass plate was used from the outside, and it was sufficiently pressed and smoothed. Next, the glass plate filled with the sample was placed in a powder X-ray diffractometer, and a diffraction pattern was obtained using Cu-Kα rays.

  As a result, the diffractogram shown in FIG. 9 was obtained. From the result of the crystal structure analysis by the Rietveld method, it was confirmed that the synthesized sample had the target monoclinic crystal.

As shown in FIG. 9, the highest intensity peak appeared at 2θ = 23.96 °, and two peaks appeared in the range of 2θ = 44 ° ± 1 °. Specifically, these two peaks are a low angle peak at 2θ = 44.06 ° and a high angle peak at 2θ = 44.46 °. The peak intensity ratio (I _H / I _L ) between the intensity (I _L ) of the peak on the low angle side and the intensity (I _H ) of the peak on the high angle side was 1.37.

(Production of electrodes)
Acetylene black as a conductive agent was mixed with the monoclinic complex oxide synthesized above in a proportion of 10 parts by weight with respect to the oxide. This mixture is dispersed in NMP (N-methyl-2-pyrrolidone), and as a binder, polyvinylidene fluoride (PVdF) is mixed with the oxide in a 10-fold ratio to produce an electrode slurry. did. This slurry was applied onto a current collector made of aluminum foil using a blade. This was dried under vacuum at 130 ° C. for 12 hours to obtain an electrode.

<Example 2>
(Synthesis)
Single unit represented by the general formula Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) TiNb ₂ O _{7 in} which x = 0, y = 0, and z = 0 was synthesized among the oblique complex oxides. Commercially available oxide reagents Nb ₂ O ₅ and TiO ₂ were used as starting materials. These powders were weighed to a molar ratio of 1: 1 and mixed in a mortar. Next, it was put into an electric furnace and baked at 1400 ° C. for a total of 20 hours.

(Powder X-ray diffraction measurement)
The obtained sample was subjected to powder X-ray diffraction measurement in the same manner as in Example 1. As a result, the diffractogram shown in FIG. 10 was obtained. Similarly, from the analysis result by the Rietveld method, it was confirmed that the synthesized sample had the target monoclinic crystal.

Further, as shown in FIG. 10, the highest intensity peak appeared at 2θ = 26.14 °, and two peaks appeared in the range of 2θ = 44 ° ± 1 °. Specifically, these two peaks are a low-angle peak at 2θ = 44.12 ° and a high-angle peak at 2θ = 44.52 °. The peak intensity ratio (I _H / I _L ) of the peak intensity (I _L ) on the low angle side and the peak intensity (I _H ) on the high angle side was 0.32.

(Production of electrodes)
Using the monoclinic complex oxide synthesized above, an electrode was produced in the same manner as in Example 1.

<Comparative example>
(Synthesis)
As a comparative example, a composite oxide represented by the formula LiSr _0.5 Ti ₃ O ₇ was synthesized. This composite oxide contains tetravalent and divalent cations as cations. The tetravalent cation in the crystal is Ti, and the divalent cation is Sr. This composite oxide is described in Non-Patent Document 3 (I. Beharouak and K. Amine, Electrochemistry Communications, 5, 435 (2003)).

As starting materials, commercially available reagents Li ₂ CO ₃ , SrCO ₃ and TiO ₂ were used. These powders were weighed at a molar ratio of a desired composition and mixed in a mortar. Next, it was placed in an electric furnace and baked at 1250 ° C. for a total of 20 hours.

(Powder X-ray diffraction measurement)
The obtained sample was subjected to powder X-ray diffraction measurement in the same manner as in Example 1. As a result, the diffraction pattern shown in FIG. 11 was obtained. Since the characteristics of the obtained diffraction pattern coincided with the characteristics of the diffraction pattern of the compound described in Non-Patent Document 3, it was inferred that the target composite oxide was obtained. Furthermore, as a result of Rietveld analysis from the information of Non-Patent Document 3, it was confirmed that the target composite oxide was obtained. Further, as shown in FIG. 11, the peak with the highest intensity appeared in the vicinity of 2θ = 46 °. Two peaks did not appear in the range of 2θ = 44 ° ± 1 °.

(Production of electrodes)
Using the composite oxide synthesized above, an electrode was produced in the same manner as in Example 1.

<Electrochemical measurement>
Electrochemical measurement cells were produced using the electrodes of Examples 1 and 2 and the comparative example, a metal lithium foil as a counter electrode, and a nonaqueous electrolyte. As the nonaqueous electrolyte, a solution obtained by dissolving lithium hexafluorophosphate at a concentration of 1 M in a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1: 1) was used.

  About each measurement cell of Examples 1, 2 and a comparative example, the charge / discharge test was done at room temperature. The charge / discharge test was performed at a charge / discharge current value of 0.2 C (time discharge rate) in a potential range of 1.0 V to 3.0 V on the basis of a metal lithium electrode. However, the comparative example was measured in a potential range of 1.0 V to 2.0 V in order to protect the crystal structure.

  Next, 50 cycles were repeatedly charged / discharged (one cycle of charge / discharge), and the discharge capacity retention rate after 50 cycles was examined. Charging / discharging is based on a metal lithium electrode, the examples are 1.0 V to 3.0 V, the comparative example is a potential range of 1.0 V to 2.0 V, the current value is 1 C (time discharge rate), and room temperature (25 ° C). In order to confirm the discharge capacity maintenance rate after 50 times, charge and discharge were performed again at 0.2 C (time discharge rate), and the capacity maintenance rate was calculated with the initial discharge capacity being 100%.

  Moreover, the ratio of 0.2 C discharge capacity and 1.0 C discharge capacity was calculated as an index of rate performance.

<Result>
The results are shown in Table 1.

The initial charge / discharge curves obtained for Examples 1 and 2 and the comparative example are shown in FIG. The results of the charge / discharge test are shown in Table 1.

  As shown in Table 1 and FIG. 12, Examples 1 and 2 using a complex oxide containing a tetravalent cation and a pentavalent cation in the crystal structure are divalent and tetravalent in the crystal structure. The initial discharge capacity and the initial charge / discharge efficiency were higher than in the comparative example using the composite oxide containing the cation. Moreover, the discharge capacity maintenance factor and charge / discharge efficiency after 50 cycles were also high, and it was shown that charging / discharging was possible stably. Moreover, since the 1C / 0.2C capacity ratio was high, the rate performance was also high. Thus, the composite oxide containing a tetravalent cation and a pentavalent cation has excellent performance because the pentavalent cation attracts an electron cloud of oxide ions, so that the electronic correlation between Li and oxide ions This is considered to be due to the fact that the pentavalent cation is reduced with the insertion of Li.

Further, in Example 2, the peak with the highest intensity appears at 2θ = 26 ± 0.5 ° which is considered to be the peak of (0 0 3) plane as shown in FIG. 10, and the line width is also sharp. From this, it is considered that the crystallites in the [001] direction are growing well. The intensity ratio (I _H / I _L ) of the two peaks appearing in the range of 2θ = 44 ° ± 1 ° was 0.32. In Example 2, the charge / discharge capacity, the charge / discharge efficiency, the capacity retention rate, and the rate performance were all higher than in Example 1 in which the peak intensity ratio was 1.37.

From this, the maximum intensity peak appears at 2θ = 26 ± 0.5 °, and the intensity ratio (I _H / I _L ) of the two peaks appearing in the range of 2θ = 44 ° ± 1 ° is less than 1. The oblique crystal type composite oxide is considered to have further excellent performance.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

[Appendix]
[1] Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ ≦ 0.3) A battery active material comprising a monoclinic complex oxide: wherein M1 is at least one selected from the group consisting of Zr, Si and Sn, and M2 is V, Ta and At least one selected from the group consisting of Bi.
[2] In a powder X-ray diffraction diffraction diagram using a Cu-Kα radiation source, the highest intensity peak appears at 2θ = 26 ° ± 0.5 °, and two peaks appear at 2θ = 44 ° ± 1 °. The active material for a battery according to the above [1], wherein the intensity ratio (I _H / I _L ) of these two peaks is less than 1, wherein I _H is the high angle side I _L is a low angle peak.
[3] The battery active material according to [1] or [2], wherein the monoclinic complex oxide is TiNb ₂ O ₇ .
[4] A non-aqueous electrolyte battery comprising a negative electrode including the battery active material according to any one of [1] to [3], a positive electrode, and a non-aqueous electrolyte.
[5] A battery pack comprising the nonaqueous electrolyte battery according to [4].

  DESCRIPTION OF SYMBOLS 1,11 ... Electrode group, 2,12 ... Exterior member, 3,14 ... Negative electrode, 4,15 ... Separator, 5,13 ... Positive electrode, 6,16 ... Negative electrode terminal, 7, 17 ... Positive electrode terminal, 20 ... Battery pack , 21 ... single cell, 24 ... printed wiring board, 25 ... thermistor, 26 ... protection circuit, 37 ... storage container, 101 ... metal ion, 102 ... oxide ion, 103 ... skeleton structure part, 104 ... gap part, 105, 106... Region, 107.

Claims (5)

A non-aqueous electrolyte battery including an exterior member and a positive electrode, a negative electrode, and a non-aqueous electrolyte housed in the exterior member,
The exterior member is selected from a laminate film container made of a laminate film having a thickness of 0.5 mm or less and a metal container made of a metal plate having a thickness of 1 mm or less,
The negative electrode includes a negative electrode layer containing a negative electrode active material, a conductive agent and a binder, and a current collector,
The negative electrode active material is Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _{7 ± δ} (0 ≦ x ≦ 5, 0 ≦ y ≦ 1, 0 ≦ z ≦ 2, 0 ≦ δ
≦ 0.3), and the monoclinic complex oxide has crystallites grown in the [001] direction,
here,
M1 is at least one selected from the group consisting of Zr, Si and Sn;
The nonaqueous electrolyte battery, wherein M2 is at least one selected from the group consisting of V, Ta, and Bi.   The non-aqueous electrolyte battery according to claim 1, wherein the conductive agent is at least one selected from the group consisting of acetylene black, carbon black, and graphite. The nonaqueous electrolyte battery according to claim 1, wherein the monoclinic complex oxide has a specific surface area of 5 m ² / g or more and less than 200 m ² / g. The non-aqueous electrolyte battery according to claim 1, wherein the monoclinic complex oxide is TiNb ₂ O ₇ .   A battery pack comprising the nonaqueous electrolyte battery according to claim 1.

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