JP5165875B2 - Non-aqueous electrolyte battery - Google Patents

Description

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

  In recent years, as a result of rapid technological development in the electronics field, electronic devices have become smaller and lighter. As a result, electronic devices have become portable and cordless. Along with this, a battery that is a power source is also required to be small, light, and have high energy density. Lithium secondary batteries having a high energy density have been developed to meet this demand, and thin and light lithium secondary batteries have been commercialized.

  By the way, as a secondary battery, a nonaqueous electrolyte secondary battery capable of rapid charging and high output discharge has been studied as described in Patent Document 1 in order to eliminate the troublesomeness of charging for several hours. In Patent Document 1, a current collector made of an aluminum foil or an aluminum alloy foil having an average crystal grain size of 50 μm or less is used, and negative electrode active material particles having a particle size distribution in which the average particle size of primary particles is 1 μm or less are used. Fast charging and high power discharge are possible.

In this nonaqueous electrolyte secondary battery, there is a demand for further improvement of the quick charge performance.
JP-A-2005-123183

  An object of the present invention is to provide a nonaqueous electrolyte battery excellent in rapid charging performance.

A nonaqueous electrolyte battery according to the present invention includes a positive electrode current collector, and a positive electrode including a positive electrode active material-containing layer carried on the positive electrode current collector,
A negative electrode current collector made of an aluminum foil having an average crystal grain size of 0.01 to 50 μm or an aluminum alloy foil having an average crystal grain size of 0.01 to 50 μm, and supported on the negative electrode current collector, and having an average particle diameter of 1 μm A negative electrode including a negative electrode active material-containing layer containing the following lithium titanium oxide particles;
A nonaqueous electrolyte battery comprising a nonaqueous electrolyte containing an organic solvent composed of at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate and γ-butyrolactone ,
The amount of the organic solvent to the battery capacity 1Ah is in the range of 6-8 g / Ah, and the 130~290cm with respect to the positive electrode active the the material containing layer facing area of the negative electrode active material-containing layer is the organic solvent 1 g ² / It is the range of g.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte battery excellent in the quick charge performance can be provided.

  Lithium titanium oxide has a small degree of expansion and contraction due to insertion and extraction of lithium, so that it undergoes little structural change when subjected to a rapid charge cycle, and is desirably used as a negative electrode active material. By making the average particle diameter of the lithium titanium oxide particles 1 μm or less, the lithium diffusion time can be shortened and the specific surface area can be improved. A more preferable average particle diameter is 0.3 μm or less. However, if the average particle size is small, the aggregation of primary particles tends to occur, or the nonaqueous electrolyte distribution may be biased toward the negative electrode, leading to depletion of the electrolyte at the positive electrode, so the lower limit is set to 0.001 μm. It is desirable to do.

  Lithium titanium oxide particles having an average particle size of 1 μm or less are used as the negative electrode active material, and the average crystal particle size of the aluminum foil or aluminum alloy foil used for the negative electrode current collector is 0.01 to 50 μm. This is because when the average crystal grain size exceeds 50 μm, the crystal grain size is large and the grain boundary is large, so that pinholes and cracks are likely to occur, and a long charge / discharge cycle life cannot be obtained. This is because when the average crystal grain size is less than 0.01 μm, there are many amorphous portions in the microstructure, and sufficient conductivity cannot be obtained. A more preferable average crystal grain size is 0.01 to 3 μm.

  As a result of repeated research, the present inventors have not only used the negative electrode active material and the negative electrode current collector in order to improve the quick charge performance and the high output discharge performance. It has been found that the balance between the counter area and the non-aqueous electrolyte is very important, and by controlling this balance, rapid charging performance and high power discharging performance are improved.

That is, in the non-aqueous electrolyte battery using the negative electrode current collector and the negative electrode active material, the amount of the organic solvent with respect to the battery capacity 1Ah (organic solvent weight ratio) is 6 to 8 g / Ah, and the positive electrode active material is contained with respect to 1 g of the organic solvent. By making the opposing area (opposite area ratio) of the layer and the negative electrode active material-containing layer 130 to 290 cm ² / g, the internal resistance can be reduced without impairing the energy density of the nonaqueous electrolyte battery, and the rapid charging performance It was determined that high power discharge performance could be improved.

Even if the weight ratio of the organic solvent is 6 to 8 g / Ah, if the facing area ratio is less than 130 cm ² / g, the internal resistance increases, and the charging time becomes longer. In addition, when the organic solvent weight ratio is within the above range, if the facing area ratio exceeds 290 cm ² / g, the increase in the battery thickness due to the increase in the separator amount and the current collector amount becomes significant. This is disadvantageous when a small size and light weight are required. From the above, the facing area ratio is desirably 130 to 290 cm ² / g. Furthermore, when the facing area ratio is 150 cm ² / g or more, it is possible to suppress an increase in electrode resistance when charging and discharging for 2000 cycles or more are repeated. As the facing area ratio increases, the ratio of separators and current collectors in the electrode group increases. For this reason, the more practical range is 250 cm < ² > / g or less from the viewpoint of obtaining a high battery capacity while ensuring excellent rapid charging performance. Therefore, a more preferable range is 150 to 250 cm ² / g.

Even if the facing area ratio is 130 to 290 cm ² / g, if the weight ratio of the organic solvent is less than 6 g / Ah, the internal resistance increases, so the charging time becomes longer. Further, when the counter area ratio is within this range, if the organic solvent weight ratio exceeds 8 g / Ah, excess nonaqueous electrolyte that is not impregnated in the positive and negative electrodes and the separator remains, which is disadvantageous in terms of miniaturization and weight reduction. Become. In view of the above, the organic solvent weight ratio is desirably 6 to 8 g / Ah. A more preferable range is 6.5 to 7.5 g / Ah. By setting within this range, the electrode group can be uniformly impregnated with the nonaqueous electrolyte in a short time.

  Here, the facing area between the positive electrode active material-containing layer and the negative electrode active material-containing layer means an area where the positive electrode active material-containing layer and the negative electrode active material-containing layer face each other with a separator therebetween. The battery capacity means the nominal capacity of the nonaqueous electrolyte battery.

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

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

The average crystal grain size of aluminum and aluminum alloy used for the negative electrode current collector is measured by the method described below. The structure of the current collector surface is observed with a metallographic microscope, the number n of crystal particles existing in a 1 mm × 1 mm visual field is measured, and the average crystal particle area S (μm ² ) is calculated from the following equation (0).

S = (1 × 10 ⁶ ) / n (0)
Here, the value represented by (1 × 10 ⁶ ) is a visual field area (μm ² ) of 1 mm × 1 mm, and n is the number of crystal grains. The average crystal grain size d (μm) is calculated from the following formula (1) using the obtained average crystal grain area S. Such calculation of the average crystal grain size d is performed for five locations (five fields of view), and the average value is defined as the average crystal grain size. Note that the assumed error is about 5%.

d = 2 (S / π) ^1/2 (1)
Aluminum foil and aluminum alloy foil having an average crystal grain size of 0.01 to 50 μm are obtained by annealing an aluminum foil or aluminum alloy foil having an average crystal grain diameter of 90 μm at 50 to 250 ° C. and then cooling to room temperature. Can do.

  The thickness of the negative electrode current collector is preferably 20 μm or less in order to increase the capacity. A more preferable range is 12 μm or less. Further, the lower limit value of the thickness of the negative electrode current collector is desirably 3 μm.

  The purity of aluminum used for the negative electrode current collector is preferably 99.99% or more for improving corrosion resistance and increasing strength. The aluminum alloy is preferably an alloy containing one or more elements selected from the group consisting of iron, magnesium, zinc, manganese and silicon in addition to aluminum. For example, an Al-Fe alloy, an Al-Mn alloy, and an Al-Mg alloy can obtain higher strength than aluminum. On the other hand, the content of transition metals such as nickel and chromium in aluminum and aluminum alloys is preferably 100 ppm or less (including 0 ppm). For example, an Al—Cu-based alloy increases strength but deteriorates corrosion resistance, and is not suitable as a current collector. The aluminum content in the aluminum alloy is desirably 95% by weight or more and 99.5% by weight or less. If it is out of this range, sufficient strength may not be obtained even if the average crystal grain size is 0.01 to 50 μm. A more preferable aluminum content is 98% by weight or more and 99.5% by weight or less.

Examples of the lithium titanium oxide include spinel-type lithium titanate (for example, Li _{4 + x} Ti ₅ O ₁₂ (x is −1 ≦ x ≦ 3)) and ramsdellite-type lithium titanate (for example, Li ₂ Ti _3). And O ₇ ). According to the lithium titanate having a spinel structure, a sufficient effect can be obtained in improving the quick charge performance.

  A carbon material can be used as a conductive agent for increasing electron conductivity and suppressing contact resistance with the current collector. Examples thereof include acetylene black, carbon black, coke, carbon fiber, and graphite.

  Examples of the binder for binding the active material and the conductive agent include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and styrene butadiene rubber.

  Regarding the mixing ratio of the negative electrode active material, the conductive agent, and the binder, the negative electrode active material is 80% by weight to 95% by weight, the conductive agent is 3% by weight to 18% by weight, and the binder is 2% by weight or more. It is preferable to make it into the range of 7 weight% or less.

The density of the negative electrode is desirably 1.5 g / cm ³ or more and 5 g / cm ³ or less. Thereby, a high battery capacity can be obtained. A more preferable range is 2 g / cm ³ or more and 4 g / cm ³ or less.

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

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

  Examples of the positive electrode current collector include an aluminum foil and an aluminum alloy foil. Each of the aluminum foil and the aluminum alloy foil preferably has an average crystal grain size of 50 μm or less. More preferably, it is 3 μm or less. As a result, the strength of the positive electrode current collector is increased, the positive electrode can be densified without breaking the positive electrode current collector, and the capacity density can be improved. As the average crystal grain size is smaller, the occurrence of pin poles and cracks can be reduced, and the chemical strength and physical strength of the positive electrode current collector can be increased. In order to secure an appropriate hardness by setting the microstructure of the current collector to be crystalline, the lower limit value of the average crystal grain size is desirably 0.01 μm.

  The thickness of the positive electrode current collector is preferably 20 μm or less in order to increase the capacity. A more preferable range is 15 μm or less. Moreover, it is desirable that the lower limit value of the thickness of the positive electrode current collector be 3 μm.

Examples of the positive electrode active material include oxides, sulfides, and polymers. As the oxide, for example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide such as Li _x Mn ₂ O ₄ or Li _x MnO ₂ , lithium such as Li _x NiO _2, etc. nickel composite oxide, for example, Li _x lithium-cobalt composite oxides such as CoO _2, for example, LiNi _1-y Co _y O ₂ lithium-nickel-cobalt composite oxide such as, for example, lithium manganese cobalt such as LiMn _y Co _1-y O ₂ composite oxides, for example olivine, such as _{Li x Mn 2-y Ni y} O 4 spinel-type lithium-manganese-nickel composite oxide such as, for example, _{Li x FePO 4, Li x Fe} 1-y Mn y PO 4, Li x CoPO 4 Lithium phosphorus oxide having a structure, for example, iron sulfate such as Fe ₂ (SO ₄ ) ₃ , for example, vanadium oxide such as V ₂ O ₅ And so on. In addition, it is preferable that x and y are the range of 0-1.

  Examples of the polymer include conductive polymer materials such as polyaniline and polypyrrole, and disulfide polymer materials. In addition, sulfur (S), carbon fluoride, and the like can be used. Preferred positive electrode active materials include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, spinel type lithium manganese nickel composite oxide, lithium manganese cobalt composite oxide, lithium phosphorus Examples include acid iron. According to these active materials, a high positive electrode voltage can be obtained.

  Examples of the conductive agent for increasing the electron conductivity and suppressing the contact resistance with the current collector include acetylene black, carbon black, and graphite.

  Examples of the binder for binding the active material and the conductive agent include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

  Regarding the mixing ratio of the positive electrode active material, the conductive agent and the binder, the positive electrode active material is 80% by weight to 95% by weight, the conductive agent is 3% by weight to 18% by weight, and the binder is 2% by weight to 7%. It is preferable to make it into the range below weight%.

  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.

3) Non-aqueous electrolyte Examples of the non-aqueous electrolyte include a non-aqueous electrolyte prepared by dissolving an electrolyte in an organic solvent, and a gel non-aqueous electrolyte in which a non-aqueous electrolyte and a polymer material are combined. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.

Examples of the electrolyte include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Li (CF ₃ SO ₂ ). ₃ C, LiB [(OCO) ₂ ] _{2 and the} like. The type of electrolyte used can be one type or two or more types.

  The electrolyte concentration in the organic solvent is desirably in the range of 0.5 to 2 mol / L.

  As the organic solvent, one kind or two or more kinds selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC) and γ-butyrolactone (GBL) can be mixed and used. If a solvent other than the above is used, the volume necessary for the organic solvent weight ratio to be 6 to 8 g / Ah increases, which not only lowers the energy density of the battery but also improves the quick charge performance. It becomes difficult.

  The weight of the organic solvent in the nonaqueous electrolyte battery is measured by gas chromatography. First, the battery is disassembled, and the positive electrode, the negative electrode, the separator, and the outer container are immersed in acetone, and organic solvents (for example, ethylene carbonate, propylene carbonate, and γ-butyrolactone) are extracted into acetone. This extract is analyzed by gas chromatography using CBP-1 as the stationary phase and helium gas as the mobile phase. The quantification is performed by a calibration curve obtained by analyzing a known amount of an organic solvent (for example, ethylene carbonate, propylene carbonate, and γ-butyrolactone) to be measured under the same conditions.

4) Container As the container, a laminate film container or a metal container is used. The shape of the container depends on the form of the nonaqueous electrolyte secondary battery. Examples of the form of the nonaqueous electrolyte secondary 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 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 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).

  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 average crystal grain size of each of aluminum and aluminum alloy is preferably 50 μm or less. By setting the average crystal grain size to 50 μm or less, the strength of a metal container made of aluminum or an aluminum alloy is increased, and sufficient mechanical strength can be ensured even if the thickness of the container is reduced. In addition, More preferably, it is 10 micrometers or less. Further, it is desirable that the lower limit value of the average crystal grain size is 0.01 μm. These features are suitable for batteries that require high temperature conditions, high energy density, etc., for example, in-vehicle secondary batteries. For the same reason as the negative electrode current collector, the purity of aluminum is preferably 99.99% or more. As the aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon 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.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a flat type nonaqueous electrolyte battery in which the direction in which the positive electrode terminal is drawn out and the direction in which the negative electrode terminal is drawn out is the same will be described with reference to FIGS.

  As shown in FIG. 1, the flat electrode group 1 has a structure in which a positive electrode 2 and a negative electrode 3 are wound into a flat shape with a separator 4 interposed therebetween. The strip-like positive electrode terminal 5 is electrically connected to the positive electrode 2. On the other hand, the strip-like negative electrode terminal 6 is electrically connected to the negative electrode 3. The electrode group 1 is housed in a laminate film container 7 in which a sealing portion 8 is formed on both long sides and one short side. As shown in FIGS. 1 and 2, the tips of the positive electrode terminal 5 and the negative electrode terminal 6 are drawn out from the sealing portion 8 on the short side of the container 7.

  As shown in FIG. 3, the positive electrode 2 includes a positive electrode current collector 2a and a positive electrode active material-containing layer 2b supported on one or both surfaces of the positive electrode current collector 2a. The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on one or both surfaces of the negative electrode current collector 3a. The separator 4 is interposed between the positive electrode active material-containing layer 2b and the negative electrode active material-containing layer 3b.

  Next, a flat type nonaqueous electrolyte battery in which the direction in which the positive electrode terminal is drawn out and the direction in which the negative electrode terminal is drawn is opposite to each other will be described with reference to FIGS.

  As shown in FIG. 4, in the flat electrode group 1, the positive electrode terminal 5 is drawn out from one short side end surface, and the negative electrode terminal 6 is drawn out from the other short side end surface. The positive electrode terminal 5 and the negative electrode terminal 6 are made of a conductive material such as aluminum or an aluminum alloy, for example. In the electrode group 1, for example, as shown in FIG. 4, separators 4 are folded into ninety-nine, and sheet-like positive electrodes 2 and sheet-like negative electrodes 3 are alternately inserted between overlapping separators. The sheet-like positive electrode 2 includes a positive electrode current collector and a positive electrode active material-containing layer laminated on one or both surfaces of the positive electrode current collector. As shown in FIG. 5, the positive electrode terminal 5 is one in which the vicinity of the center of the short side of the positive electrode current collector projects in the long side direction. The positive terminal 5 is drawn from each positive electrode 2 and bundled together by welding. On the other hand, the sheet-like negative electrode 3 includes a negative electrode current collector and a negative electrode active material-containing layer laminated on one or both surfaces of the negative electrode current collector. As shown in FIG. 4, the negative electrode terminal 6 is one in which the vicinity of the center of the short side of the negative electrode current collector projects in the long side direction. The negative terminal 6 is pulled out from each negative electrode 3, and is bundled together by welding.

  A container in which the electrode group 1 of FIG. 4 is housed is shown in FIG. As shown in FIG. 6, the container 9 is formed by subjecting the laminate film to an electrode group housing portion 10 composed of a rectangular recess formed by, for example, deep drawing or pressing, and processing of the laminate film. And a rectangular lid body 11 made of a flat plate portion. When the laminate film is folded back along the dotted line toward the container, the electrode group storage unit 10 can be covered with the lid 11. The inner surface of the lid 11 is joined to the three sides 12a to 12c at the periphery of the opening of the electrode group storage unit 10 by, for example, heat sealing. FIG. 7 shows a state in which the lid 11 is joined to the three sides 12 a to 12 c at the periphery of the opening of the electrode group storage unit 10 and is arranged with the lid 11 facing down. As the laminate film, for example, a laminate film in which a metal layer is disposed between a thermoplastic resin layer and a resin layer can be used. Since the thermoplastic resin layer is positioned on the inner surfaces of the electrode group housing part 10 and the lid body 11, the lid body 11 can be joined to the electrode group housing part 10 by thermal fusion. The thermoplastic resin layer is made of, for example, polypropylene (PP) or polyethylene (PE). The metal layer is preferably an aluminum foil or an aluminum alloy foil. The resin layer is used to reinforce the metal layer and can be formed from a polymer such as nylon or polyethylene terephthalate (PET).

  The electrode group 1 is housed in the electrode group housing portion 10 of the container 9 while holding the nonaqueous electrolyte. As shown in FIG. 7, the positive terminal 5 is drawn out from between the short side 12 a of the periphery of the opening of the electrode group storage unit 10 and the lid 11. The negative electrode terminal 6 is drawn out from between the short side 12 b on the opposite side of the periphery of the opening of the electrode group storage unit 10 and the lid 11. The long side 12c at the periphery of the opening of the electrode group housing portion 10 and the lid 11 are bent substantially vertically after being joined by thermal fusion.

  The flat type electrode group is folded in a ninety nine shape as illustrated in FIG. 4 even when the positive electrode and the negative electrode are wound into a flat shape through a separator as illustrated in FIG. Alternatively, a positive electrode and a negative electrode may be alternately interposed between the separators. Or you may laminate | stack a positive electrode, a negative electrode, and a separator. The shape of the separator can be a bag or a sheet. Furthermore, two or more electrode groups in which the positive electrode, the negative electrode, and the separator are wound in a spiral shape may be stacked. When laminating the positive electrode and the negative electrode, it is preferable to fold the separator into ninety nines from the viewpoint of yield.

  As a separator, a synthetic resin nonwoven fabric, a polyethylene porous film, a polypropylene porous film, etc. can be used, for example.

[Example]
Embodiments of the present invention will be described below with reference to the drawings described above. It should be noted that the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

Example 1
<Production of negative electrode>
As a negative electrode active material, Li occlusion potential is 1.55 V (vs. Li / Li ⁺ ), Li ₄ Ti ₅ O ₁₂ , a spinel structure, and lithium titanate having an average particle diameter shown in Table 1 below. Powder was prepared.

  A laser diffraction particle size distribution analyzer (Shimadzu Corporation, model number SALD-300) was used to measure the particle size of the negative electrode active material. First, about 0.1 g of a sample was put in a beaker or the like, and then a surfactant and 1 to 2 mL of distilled water were added and stirred sufficiently, and poured into a stirred water tank. The light intensity distribution was measured 64 times at intervals of 2 seconds, the particle size distribution data was analyzed, and the particle size (D50) having a cumulative frequency distribution of 50% was defined as the average particle size.

  This negative electrode active material, a carbon powder having an average particle diameter of 0.4 μm as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were blended in a weight ratio of 90: 7: 3, and these were mixed. -A slurry was prepared by dispersing in a methylpyrrolidone (NMP) solvent.

  On the other hand, an aluminum foil having a thickness of 15 μm and a purity of 99.99% and having an average crystal grain size shown in Table 1 below was prepared as a negative electrode current collector.

  The slurry was applied to the obtained negative electrode current collector, dried, and then pressed to support the negative electrode active material-containing layer on the negative electrode current collector, thereby producing a negative electrode.

<Preparation of positive electrode>
Lithium cobalt oxide (LiCoO ₂ ) as an active material, graphite powder as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder are blended in a weight ratio of 87: 8: 5, and these are mixed. -A slurry was prepared by dispersing in a methylpyrrolidone (NMP) solvent. A slurry was applied to an aluminum foil having a thickness of 15 μm and a purity of 99.99% and having an average crystal grain size shown in Table 1 below, dried, and then pressed to include a positive electrode active material in the positive electrode current collector. The layer was supported to produce a positive electrode.

  An aluminum-containing laminate film having a thickness of 0.1 mm was prepared as a material for forming the container (exterior member). The aluminum layer of this aluminum-containing laminate had a thickness of about 0.03 mm. Polypropylene was used as the resin for reinforcing the aluminum layer. The laminate film was bonded by heat sealing to obtain a container (exterior member).

  Next, the belt-like positive electrode terminal was electrically connected to the positive electrode, and the belt-like negative electrode terminal was electrically connected to the negative electrode. A separator made of a polyethylene porous film having a thickness of about 20 μm was coated in close contact with the positive electrode. The positive electrode covered with the separator was overlapped with the negative electrode so as to face each other, and these were wound in a spiral shape to produce an electrode group. This electrode group was pressed into a flat shape. An electrode group formed into a flat shape was inserted into a container (exterior member).

A non-aqueous electrolyte was prepared by dissolving 1.5 mol / L of lithium salt LiBF ₄ in an organic solvent in which EC, PC, and GBL were mixed at a volume ratio of 1: 1: 1. The obtained non-aqueous electrolyte was poured into a container to produce a flat lithium secondary battery as shown in FIG.

  In the fabricated battery, the organic solvent weight (organic solvent weight ratio) with respect to the battery capacity 1Ah and the facing area (facing area ratio) of the positive electrode active material-containing layer and the negative electrode active material-containing layer with respect to 1 g of the organic solvent are shown in Table 1 below. The amount of the electrolyte and the opposing area of the positive and negative electrodes were set so as to be the values shown.

(Examples 2-11 and Comparative Examples 1-5)
Except for setting the type of organic solvent, the organic solvent weight ratio, the opposing area ratio, the average crystal grain size, and the average grain size to the values shown in Table 1 below, lithium 2 having the same configuration as described in Example 1 was used. A secondary battery was produced. In addition, the composition of the organic solvent used in Example 12 is a mixture of EC and PC at a volume ratio of 1: 1, and the composition of the organic solvent used in Example 13 is a volume ratio of EC and GBL of 1. The composition of the organic solvent used in Comparative Example 1 was a mixture of EC, PC, and GBL at a volume ratio of 1: 1: 1.

  In the obtained battery, rapid charging at 20 C at 25 ° C. was performed up to 2.8 V, and the charging time was measured. Here, the charging time is defined as 100% discharge capacity when discharged from a charged state to 2.0 V at a rate of 1C at 25 ° C., until the charge capacity reaches 80% of the discharge capacity. Time.

Moreover, in the cycle test, after performing quick charge to 25V and 20C at 2.8V for 10 minutes, the charge / discharge cycle which discharges to 25V at 1C and 2.0V was repeated. When the discharge capacity at the first cycle at this time is 100%, the number of cycles until the discharge capacity maintenance rate reaches 80% is shown.

As is clear from Table 1, with respect to the organic solvent weight ratio, Examples 1 and 2 having 6 to 8 g / Ah had a charging time as compared with Comparative Example 1 having an organic solvent weight ratio of less than 6 g / Ah. It was short and had excellent quick charge cycle characteristics. Further, when the weight ratio of the organic solvent exceeded 8 g / Ah when the facing area ratio was 130 to 290 cm ² / g, an excessive electrolyte solution that was not impregnated in the electrode group remained in the container. Therefore, the organic solvent weight ratio is desirably in the range of 6 to 8 g / Ah in order to improve the quick charge performance without impairing the energy density.

Regarding the facing area ratio, Examples ³ , 4, 8, and 9 with 130 to 290 cm ² / g had shorter charging times than Comparative Example 2 with the facing area ratio of less than 130 cm ² / g. Further, when the weight ratio of the organic solvent was 6 to 8 g / Ah and the facing area ratio exceeded 290 cm ² / g, the battery thickness increased due to the increase in the separator amount and the current collector amount. Therefore, in order to improve the quick charge performance without impairing the energy density, the facing area ratio is preferably in the range of 130 to 290 cm ² / g. In addition, Example 8 having an opposing area ratio of 150 cm ² / g or more had a longer cycle life than Example 3 having an opposing area ratio of 130 cm ² / g.

From the comparison of Examples 5 and 6 and Comparative Examples 3 and 4, even if the organic solvent weight ratio is 6 to 8 g / Ah and the facing area ratio is in the range of 130 to 290 cm ² / g, the average crystal grain size It has been found that the charging time becomes longer when the value is out of the range of 0.01 to 50 μm. On the other hand, from the comparison of Examples 1 and 7 and Comparative Example 5, even when the average particle diameter of the negative electrode active material exceeds 1 μm, the effect of specifying the organic solvent weight ratio and the opposed area ratio cannot be obtained. confirmed.

Therefore, in order to obtain excellent quick charge performance, the average crystal particle size of the negative electrode current collector is 0.01 to 50 μm, the average particle size of the lithium titanium oxide particles is 1 μm or less, and the weight ratio of the organic solvent is 6 to 8 g / Ah, it is desirable that the facing area ratio is 130 to 290 cm ² / g at the same time.

  Furthermore, from the results of Examples 10 and 11, it can be confirmed that sufficient rapid charging performance can be obtained even if the type of organic solvent is changed to a mixed solvent of EC and PC or a mixed solvent of EC and GBL. It was.

In addition to LiBF _{4 of} this example, the electrolyte includes LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ), LiN (C ₂ F ₅ SO ₂ ) ₂ , Li (CF ₃ SO ₂ ) ₃ C, LiB [(OCO) ₂ ] _{2 and the} like can be mentioned, and one type or two or more types of electrolytes can be used.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The partial notch perspective view of the nonaqueous electrolyte battery which concerns on embodiment of this invention. Sectional drawing obtained when the nonaqueous electrolyte battery of FIG. 1 is cut | disconnected in the battery thickness direction. The expanded sectional view of the A section of FIG. The perspective view which showed typically the electrode group used with the nonaqueous electrolyte battery which concerns on another embodiment of this invention. The top view of the electrode group of FIG. The perspective view of the container in which the electrode group of FIG. 4 is accommodated. The perspective view which shows the nonaqueous electrolyte battery which concerns on another embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrode group, 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Separator, 5 ... Positive electrode terminal, 6 ... Negative electrode terminal, 7, 9 ... Container, 8, 12a-12c ... Sealing part, 10 ... Electrode group accommodating part, 11: Lid.

Claims (3)

A positive electrode comprising a positive electrode current collector and a positive electrode active material-containing layer carried on the positive electrode current collector;
A negative electrode current collector made of an aluminum foil having an average crystal grain size of 0.01 to 50 μm or an aluminum alloy foil having an average crystal grain size of 0.01 to 50 μm, and supported on the negative electrode current collector, and having an average particle diameter of 1 μm A negative electrode including a negative electrode active material-containing layer containing the following lithium titanium oxide particles;
A nonaqueous electrolyte battery comprising a nonaqueous electrolyte containing an organic solvent composed of at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate and γ-butyrolactone ,
The amount of the organic solvent to the battery capacity 1Ah is in the range of 6-8 g / Ah, and the 130~290cm with respect to the positive electrode active the the material containing layer facing area of the negative electrode active material-containing layer is the organic solvent 1 g ² / A nonaqueous electrolyte battery characterized by being in the range of g. The amount of the organic solvent with respect to the battery capacity 1Ah is in the range of 6.5 to 7.5 g / Ah, and the opposing area of the positive electrode active material-containing layer and the negative electrode active material-containing layer is 150 with respect to 1 g of the organic solvent. The nonaqueous electrolyte battery according to claim 1, which is in a range of ˜250 cm ² / g. The lithium titanium oxide is non-aqueous electrolyte battery according to claim 1-2 any one of claims to characterized by having a spinel structure.

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