JP2018160444A - Secondary battery, battery pack, and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery with self-discharge suppressed, a battery pack with self-discharge suppressed, and a vehicle equipped with the battery pack.SOLUTION: In an embodiment, there is provided a secondary battery including a negative electrode active material containing layer, a positive electrode active material containing layer, and an insulating layer. The insulating layer is provided between the negative electrode active material containing layer and the positive electrode active material containing layer, and includes insulating particles. The particle size distribution of the insulating particles in the insulating layer contains two or more peaks.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a secondary battery, a battery pack, and a vehicle.

  As secondary batteries such as lithium ion batteries are applied to in-vehicle applications and stationary applications, further increase in capacity, longer life, and higher output are required. Lithium titanium composite oxide is excellent in cycle performance because the volume change accompanying charge / discharge is small. Further, in the lithium occlusion / release reaction of the lithium-titanium composite oxide, in principle, it is difficult for the lithium metal to precipitate, so that the battery using the lithium-titanium composite oxide undergoes little performance deterioration even when repeated charging and discharging with a large current.

Japanese Patent No. 6070681

  An object is to provide a secondary battery in which self-discharge is suppressed, a battery pack in which self-discharge is suppressed, and a vehicle equipped with the battery pack.

  According to the embodiment, a secondary battery including a negative electrode active material-containing layer, a positive electrode active material-containing layer, and an insulating layer is provided. The insulating layer is provided between the negative electrode active material-containing layer and the positive electrode active material-containing layer, and includes insulating particles. The particle size distribution of the insulating particles in the insulating layer includes two or more peaks.

  According to another embodiment, a battery pack including the secondary battery according to the above embodiment is provided.

  According to still another embodiment, a vehicle equipped with the battery pack according to the above embodiment is provided.

The graph which shows the particle size distribution of the insulating particle in an example of the insulating layer which concerns on embodiment. Sectional drawing which shows schematically an example of the secondary battery which concerns on embodiment. Sectional drawing which expanded the A section of the secondary battery shown in FIG. The schematic sectional drawing of an example electrode composite body which the secondary battery of the other example which concerns on embodiment can comprise. The schematic sectional drawing of the electrode composite of the other example which the secondary battery of the other example which concerns on embodiment can comprise. The schematic sectional drawing of the secondary battery of the other example which concerns on embodiment. The perspective view which shows roughly an example of the assembled battery which concerns on embodiment. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. The block diagram which shows an example of the electric circuit of the battery pack shown in FIG. 1 is a cross-sectional view schematically showing an example of a vehicle according to an embodiment. The figure which showed schematically the other example of the vehicle which concerns on embodiment.

  In order to electrically insulate between the positive electrode and the negative electrode, a sheet-like separator is generally used. As a means for increasing the energy density of a secondary battery such as a lithium ion battery, there is a method of thinly applying insulating particles on an electrode instead of the separator. However, if the particle size of the insulating particles applied to the uneven electrode surface is small, the insulating particles can easily enter the gaps between the electrode active materials, and a part of the electrode may be exposed. On the other hand, when insulating particles having a large particle diameter are thinly applied, pinholes are likely to be generated, and the self-discharge of the secondary battery may be increased.

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

(First embodiment)
According to the first embodiment, a secondary battery including a negative electrode active material-containing layer, a positive electrode active material-containing layer, and an insulating layer is provided. The insulating layer is provided between the negative electrode active material-containing layer and the positive electrode active material-containing layer, and includes insulating particles. The particle size distribution of the insulating particles in the insulating layer includes two or more peaks.

  In the secondary battery according to the embodiment, the insulating layer is formed on the surface of the negative electrode active material-containing layer and / or the positive electrode active material-containing layer, for example.

  As described later, the negative electrode active material-containing layer can be included in the negative electrode. The negative electrode can include a current collector (negative electrode current collector) in addition to the negative electrode active material-containing layer. The positive electrode active material-containing layer can be included in the positive electrode. The positive electrode can include a current collector (positive electrode current collector) in addition to the positive electrode active material-containing layer. The negative electrode including the negative electrode active material-containing layer, the positive electrode active material-containing layer including the positive electrode active material-containing layer, and the insulating layer may constitute an electrode group. In the electrode group, the insulating layer may be formed on one side of the negative electrode and / or the positive electrode. Alternatively, the insulating layer can be formed on both sides of the negative electrode and / or the positive electrode.

  Alternatively, the negative electrode active material-containing layer may be provided on the surface of one surface of the current collector, and the positive electrode active material-containing layer may be provided on the surface on the back side of the current collector to constitute the electrode composite. That is, the negative electrode active material-containing layer and the positive electrode active material-containing layer can constitute a bipolar electrode. In the electrode composite, the insulating layer is formed on the surface of the negative electrode active material-containing layer and / or the positive electrode active material-containing layer. That is, the negative electrode active material-containing layer and / or the positive electrode active material-containing layer is located between the insulating layer and the current collector.

  The secondary battery according to the first embodiment can include an electrolyte. The electrolyte can be held in the above-described electrode group or electrode complex.

  The secondary battery according to the first embodiment may further include a separator disposed between the negative electrode active material-containing layer and the positive electrode active material-containing layer. The separator disposed between the negative electrode active material-containing layer and the positive electrode active material-containing layer can be adjacent to the insulating layer formed in the negative electrode active material-containing layer and / or the positive electrode active material-containing layer.

  In addition, the secondary battery according to the first embodiment can further include an electrode group or an electrode complex, and an exterior member that houses the electrolyte. The exterior member can accommodate a plurality of electrode groups. The plurality of electrode groups are, for example, electrically connected in series and accommodated in the exterior member.

  Furthermore, the secondary battery according to the first embodiment can further include a negative electrode terminal and a positive electrode terminal electrically connected to the current collector. The negative electrode terminal and the positive electrode terminal can be electrically connected to the current collector through an electrode current collection tab provided on the current collector.

  The secondary battery according to the first embodiment includes a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte.

  Hereinafter, the insulating layer, the negative electrode active material-containing layer, the positive electrode active material-containing layer, the current collector, the electrolyte, the separator, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail.

1) Insulating layer The insulating layer contains insulating particles containing at least two or more peaks in the particle size distribution.

  The fact that the particle size distribution of the insulating particles in the insulating layer includes two or more peaks may mean that the insulating particles contained in the insulating layer can be roughly classified into those having two or more particle sizes. Insulating particles with a large particle size have the effect of spatially separating the positive electrode and the negative electrode, while insulating particles with a small particle size are filled between insulating particles with a large particle size, Formation can be suppressed.

  For example, by using insulating particles having two or more peaks in the particle size distribution as insulating particles to be included in the insulating layer, the insulating layer can be formed without generating pinholes on the electrode, and the secondary battery self- Discharge can be suppressed.

  The two or more peaks may include a first peak having the highest peak intensity and a second peak having the second highest peak intensity after the first peak.

  The peak intensity of the first peak with respect to the peak intensity of the second peak is preferably 1 or more and 10 or less. The peak intensity ratio (first peak intensity / second peak intensity) is more preferably 1.2 or more and 5 or less.

  In the particle size distribution, one of the first particle diameter corresponding to the first peak and the second particle diameter corresponding to the second peak is preferably twice or more of the other. That is, the first particle diameter corresponding to the first peak is a value that is twice or more the second particle diameter corresponding to the second peak, or the second particle diameter is the first particle diameter. It is preferable that the value is twice or more.

  In the particle size distribution, the first peak is preferably on the low particle size side with respect to the second peak. In other words, it is preferable that the first particle diameter has a value smaller than the second particle diameter.

  The first particle diameter is preferably more than 0.1 μm and not more than 1 μm. A certain space | gap can be provided in an insulating layer by making a 1st particle diameter larger than 0.1 micrometer. As a result, when a liquid electrolyte or a gel electrolyte is used, a certain amount of the electrolyte can be impregnated and held in the insulating layer, and high output performance can be obtained. Moreover, the electrical micro short circuit between positive and negative electrodes can be prevented by making the 1st particle diameter into 1 micrometer or less. Moreover, it is preferable that a 2nd particle diameter is 0.3 micrometer or more and 5 micrometers or less.

  By setting the form of the insulating particles in the insulating layer within the above range, it is possible to secure a gap for maintaining high ion conductivity in the insulating layer and prevent a minute short circuit.

  In FIG. 1, the graph which shows the particle size distribution of the insulating particle in the insulating layer of an example which has a preferable form is shown. In FIG. 1, as a graph representing the particle size distribution of insulating particles, a curve indicating the frequency (vertical axis) in the insulating layer with respect to the particle size (horizontal axis) of the insulating particles in the insulating layer is illustrated. The curve shown in FIG. 1 has two peaks, and it can be seen that the frequency with respect to the particle diameter of the insulating particles includes two maximum values in the particle size distribution.

Examples of the insulating particles include metal oxides such as Al ₂ O ₃ , ZrO ₂ , SiO ₂ , and MgO. Moreover, if a solid electrolyte is used as the insulating particles, the resistance of the secondary battery can be lowered. Examples of solid electrolytes include Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) having a garnet-type structure, Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (LATP) having a NASICON-type structure (0 ≦ x ≦ 1), Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (LAGP) (0 ≦ x ≦ 1), La _{2 / 3-x} Li _x TiO ₃ having a perovskite structure (0.3 ≦ x ≦ 0.7) and the like.

  One kind of insulating particles may be used for the insulating layer, or two or more kinds may be used. For example, since different particle diameters are included, single-material insulating particles including two or more peaks in the particle size distribution may be used. Alternatively, for example, by using insulating particles of two or more kinds of materials having different particle diameters, the particle size distribution in the insulating layer may have two or more peaks.

As a specific example, a solid electrolyte having a relatively small particle size and a metal oxide such as alumina (Al ₂ O ₃ ) having a relatively large particle size can be used in combination. In a solid electrolyte having a small particle size, the ion conduction path in the solid is short. Therefore, the proportion of ion conduction that the solid electrolyte bears in the insulating layer increases, and ion conductivity in the insulating layer can be ensured. In this case, by using particles of an inexpensive material such as alumina as insulating particles having a large particle diameter to ensure insulation between the positive and negative electrodes, the cost can be reduced without reducing the ionic conductivity of the insulating layer. can do.

  The insulating layer may further include a binder in addition to the insulating particles.

  The amount of the binder contained in the insulating layer is preferably 1 part by weight or more and 5 parts by weight or less with respect to the whole insulating layer (100 parts by weight). By setting the content of the binder to 1 part by weight or more, sufficient adhesion strength with the electrode can be obtained. By setting the content of the binder to 5 parts by weight or less, high ion conductivity in the insulating layer can be ensured.

  As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber, polyacrylic acid compound, imide compound, carboxymethyl cellulose, and the like can be used. One of these may be used as a binder, or a combination of two or more may be used as a binder.

  The porosity of the insulating layer is preferably 20% or more and 80% or less. By setting the porosity to 20% or more, the liquid electrolyte can be sufficiently retained in the insulating layer, so that high ion conductivity can be ensured. By setting the porosity to 80% or less, a minute short circuit between the positive and negative electrodes can be prevented.

  In addition, as a means for electrically insulating the negative electrode layer and the positive electrode layer, for example, in a battery including a bipolar electrode provided with a sheet-like separator, the area of the negative electrode layer and / or the positive electrode is used in order to ensure insulation. In some cases, a sheet-like separator having an area larger than the area of the layer is used. However, in a bipolar battery including a liquid electrolyte, there is a risk that an electrolyte liquid junction may occur when such a separator is used. As a result of the external ion conduction path of the bipolar electrode being formed by the liquid electrolyte, the voltage in the bipolar stack (electrode assembly) can be reduced. In the secondary battery according to the embodiment, it is possible to reduce the liquid junction of the liquid electrolyte by making the area of the insulating layer the same as the area of the electrode on which the insulating layer is formed. The area of the insulating layer may be the same as the area of the electrode, or may be larger than the area of the electrode.

  The particle size distribution of the insulating particles in the insulating layer can be measured by, for example, the static image analysis method of JIS Z 8827-1 (2008).

  When the insulating layer to be measured is included in the secondary battery, for example, the target insulating layer is collected as follows, and the obtained insulating layer is measured.

  First, the secondary battery is disassembled and an electrode (positive electrode and / or negative electrode) coated with an insulating layer is taken out. Next, the electrode coated with the insulating layer is sufficiently washed with methyl ethyl carbonate and vacuum dried. Subsequently, a cross section of the insulating layer portion applied to the dried electrode is cut out by argon ion milling. The particle size distribution is measured by the image analysis method using the cut-out cross-sectional portion.

  Thus, the particle size distribution on the basis of the number is measured, and the particle diameter when the number frequency shows the maximum value with respect to the particle diameter is defined as the peak particle diameter. The maximum value of the number frequency corresponds to the peak intensity for the corresponding peak particle diameter.

  In addition, the thickness of the insulating layer can be confirmed using the cross-sectional image of the insulating layer portion obtained when the image analysis method is applied. The cross-sectional image is converted into monochrome 256 gradations and binarized by providing a threshold value. Accordingly, in the SEM image, the insulating particles and the binder are displayed as white and the void is displayed as black. By confirming the distribution of the insulating particles using this, the thickness of the insulating layer can be obtained.

  Further, the porosity of the insulating layer can be calculated using the binarized SEM image. The area of black pixels indicating voids relative to the area of all pixels in the binarized cross-sectional image is calculated as the void ratio.

2) Negative electrode active material-containing layer The negative electrode active material-containing layer can contain a negative electrode active material, and optionally a conductive agent and a binder.

  The negative electrode active material-containing layer may be formed on one side or both sides of the current collector to constitute a negative electrode. Alternatively, the negative electrode active material-containing layer is formed on one surface of the current collector, while the positive electrode active material-containing layer described later is formed on the back surface of the current collector to constitute a bipolar electrode.

The negative electrode active material-containing layer contains one or more negative electrode active materials. Examples of the negative electrode active material include lithium titanate having a ramsdellite structure (for example, Li ₂ Ti ₃ O ₇ ), lithium titanate having a spinel structure (for example, Li ₄ Ti ₅ O ₁₂ ), monoclinic titanium dioxide ( TiO ₂ ), anatase-type titanium dioxide, rutile-type titanium dioxide, hollandite-type titanium composite oxide, orthorhombic Na-containing titanium composite oxide (for example, Li ₂ Na ₂ Ti ₆ O ₁₄ ), monoclinic-type niobium titanium composite oxide objects (e.g., Nb ₂ TiO ₇₎ formula _{Ti 1-x M x + y} Nb niobium represented by _2-y O _7-σ such - titanium composite oxide (M is Mg, Fe, Ni, Co, W And at least one element selected from the group consisting of Ta and Mo; 0 ≦ x <1, 0 ≦ y <1, and −0.3 ≦ σ ≦ 0.3), and the general formula Li _{2 + a} M1 ₂ titanium represented by _{-b Ti 6-c M2 d O} 14 + δ Complex oxide (M1 is at least one element selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K, M2 is Zr, Sn, V, Nb, Ta, Mo, At least one element selected from the group consisting of W, Y, Fe, Co, Cr, Mn, Ni, and Al; 0 ≦ a ≦ 6, 0 ≦ b <2, 0 ≦ c <6, 0 ≦ d < 6 and -0.5 ≦ δ ≦ 0.5). Moreover, graphite (graphite) etc. can also be used as a negative electrode active material other than the said titanium containing oxide.

  The conductive agent is blended in order to improve current collecting performance and suppress contact resistance between the negative electrode active material and the current collector. Examples of the conductive agent include carbonaceous materials such as vapor grown carbon fiber (VGCF), acetylene black, carbon black, and graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Alternatively, instead of using a conductive agent, a carbon coat or an electron conductive inorganic material coat may be applied to the surface of the negative electrode active material particles.

  The binder is blended to fill a gap between the dispersed negative electrode active materials and bind the negative electrode active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and styrene butadiene rubber, polyacrylic acid compound, and imide compound. . One of these may be used as a binder, or a combination of two or more may be used as a binder.

  The active material, conductive agent, and binder in the negative electrode active material-containing layer are blended in proportions of 70% to 96% by mass, 2% to 28% by mass, and 2% to 28% by mass, respectively. It is preferable to do. By setting the amount of the conductive agent to 2% by mass or more, the current collecting performance of the negative electrode active material-containing 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 active material-containing layer and the current collector becomes sufficient, and excellent cycle performance 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.

  The negative electrode active material-containing layer can further include insulating particles. As the insulating particles included in the negative electrode active material-containing layer, insulating particles that can be included in the insulating layer can be used. By including the insulating particles, the lithium ion conductivity in the negative electrode active material-containing layer can be improved, and the output of the secondary battery can be increased.

The density of the negative electrode active material-containing layer (not including the current collector) is preferably 1.8 g / cm ³ or more and 2.8 g / cm ³ or less. The negative electrode active material-containing layer having a density within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is more preferably 2.1 g / cm ³ or more and 2.6 g / cm ³ or less.

  The negative electrode including the negative electrode active material-containing layer can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of the current collector. Next, the applied slurry is dried to obtain a laminate of the negative electrode active material-containing layer and the current collector. Thereafter, the laminate is pressed. In this way, a negative electrode is produced. Or you may produce a negative electrode with the following method. First, a negative electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. The mixture is then formed into pellets. Subsequently, a negative electrode can be obtained by arranging these pellets on a current collector.

3) Positive electrode active material-containing layer The positive electrode active material-containing layer can be formed on one side or both sides of a current collector to constitute a positive electrode. Alternatively, the above-described negative electrode active material-containing layer is formed on one surface of the current collector, while the positive electrode active material-containing layer is formed on the back surface of the current collector to constitute a bipolar electrode.

  The positive electrode active material-containing layer can contain a positive electrode active material, and optionally a conductive agent and a binder.

  As the positive electrode active material, for example, an oxide, a sulfide, or a polymer material can be used. The positive electrode active material-containing layer may contain one type of positive electrode active material, or may contain two or more types of positive electrode active materials. Examples of oxides and sulfides include compounds that can insert and desorb Li or Li ions.

As such a compound, for example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ; 0 <x ≦ 1) Lithium nickel composite oxide (for example, Li _x NiO ₂ ; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li _x CoO ₂ ; 0 <x ≦ 1), lithium nickel cobalt composite oxide (for example, Li _x Ni _{1-y Co y O 2;} 0 <x ≦ 1,0 <y <1), lithium-manganese-cobalt composite oxide (e.g., _{Li x Mn y Co 1-y} O 2; 0 <x ≦ 1,0 <y < 1) a lithium manganese nickel composite oxide having a spinel structure (for example, Li _x Mn _{2 -y} Ni _y O ₄ ; 0 <x ≦ 1, 0 <y <2), a lithium phosphorous oxide having an olivine structure (for example, Li _x FePO _4; 0 _{x ≦ 1, Li x Fe 1} -y Mn y PO 4; 0 <x ≦ 1,0 <y <1, Li x CoPO 4; 0 <x ≦ 1), ferrous sulfate _{(Fe 2 (SO 4) 3} ) , vanadium oxide (e.g. V ₂ O _5), and a lithium-nickel-cobalt-manganese composite oxide _{(LiNi 1-xy Co x Mn} y O 2; 0 <x <1,0 <y <1, x + y <1) is included. As the active material, these compounds may be used alone, or a plurality of compounds may be used in combination.

  Examples of the polymer material include conductive polymer materials such as polyaniline and polypyrrole, and disulfide polymer materials.

  In addition to the positive electrode active material, sulfur (S), carbon fluoride, and the like can be used.

More preferable examples of the positive electrode active material include a lithium manganese composite oxide having a spinel structure (for example, Li _x Mn ₂ O ₄ ; 0 <x ≦ 1) and a lithium nickel composite oxide (for example, Li _x NiO ₂ ; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li _x CoO ₂ ; 0 <x ≦ 1), lithium nickel cobalt composite oxide (for example, LiNi _1-y Co _y O ₂ ; 0 <x ≦ 1, 0 <y < 1) Lithium manganese nickel composite oxide having a spinel structure (for example, Li _x Mn _{2 -y} Ni _y O ₄ ; 0 <x ≦ 1, 0 <y <2), lithium manganese cobalt composite oxide (for example, Li _x Mn _y Co _1-y O ₂ ; 0 <x ≦ 1, 0 <y <1), lithium iron phosphate (for example, Li _x FePO ₄ ; 0 <x ≦ 1), and lithium nickel cobalt manganese composite oxide (LiNi _1-xy Co _{x Mn y O 2; 0 <x} <1,0 <y <1, x + y <1) are included. When these positive electrode active materials are used, the positive electrode potential can be increased.

When room temperature molten salt is used as the battery electrolyte, lithium iron phosphate, Li _x VPO ₄ F (0 ≦ x ≦ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or these It is preferable to use a positive electrode active material containing a mixture of the above. Since these compounds have low reactivity with room temperature molten salts, the cycle life can be improved. Details of the room temperature molten salt will be described later.

  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 positive electrode 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 storage / release sites of Li 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 fill a gap between the dispersed positive electrode active materials and to bind the positive electrode active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, a polyacrylic acid compound, and an imide compound. One of these may be used as a binder, or a combination of two or more may be used as a binder.

  The conductive agent is blended in order to improve current collection performance and suppress contact resistance between the positive electrode active material and the current collector. Examples of the conductive agent include carbonaceous materials such as vapor grown carbon fiber (VGCF), acetylene black, carbon black, and graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Further, the conductive agent can be omitted.

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

  By setting the amount of the binder to 2% by mass or more, sufficient electrode strength can be obtained. Further, when the amount of the binder is 20% by mass or less, the amount of the insulator included in the electrode is reduced, so that the internal resistance can be reduced.

  When a conductive agent is added, the positive electrode active material, the binder and the conductive agent are 80% by mass or more and 95% by mass or less, 2% by mass or more and 17% by mass or less, and 3% by mass or more and 18% by mass or less, respectively. It is preferable to mix | blend in a ratio.

  The effect mentioned above can be exhibited by making the quantity of a electrically conductive agent 3 mass% or more. Moreover, the ratio of the electrically conductive agent which contacts an electrolyte can be made low by making the quantity of an electrically conductive agent 18 mass% or less. When this ratio is low, decomposition of the electrolyte can be reduced under high temperature storage.

  The positive electrode active material-containing layer can further include insulating particles. As the insulating particles included in the positive electrode active material-containing layer, insulating particles that can be included in the insulating layer can be used. By including the insulating particles, the lithium ion conductivity in the positive electrode active material-containing layer can be improved, and the output of the secondary battery can be increased.

  The positive electrode including the positive electrode active material-containing layer can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of the current collector. Next, the applied slurry is dried to obtain a laminate of the positive electrode active material-containing layer and the current collector. Thereafter, the laminate is pressed. In this way, a positive electrode is produced. Alternatively, the positive electrode may be produced by the following method. First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. The mixture is then formed into pellets. Subsequently, a positive electrode can be obtained by arranging these pellets on a current collector.

4) Current collector The current collector is preferably made of aluminum or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si. For example, 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 can be used as the current collector.

A negative electrode active material-containing layer is formed thereon, and the current collector used in the negative electrode, that is, the negative electrode current collector, is electrically charged at the lithium insertion and desorption potential (vs. Li ^/ Li ⁺ ) of the negative electrode active material. Chemically stable materials can be used. In addition to the above aluminum and aluminum alloy, copper, nickel, and stainless steel can be suitably used for the negative electrode current collector.

  The thickness of the negative electrode current collector is preferably 5 μm or more and 20 μm or less. The negative electrode current collector having such a thickness can balance the strength and weight reduction of the negative electrode.

  A current collector used in the positive electrode on which the positive electrode active material-containing layer is formed, that is, the positive electrode current collector is an aluminum foil, or Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si. An aluminum alloy foil containing one or more elements selected from the above is preferable.

  The thickness of the aluminum foil or aluminum alloy foil as the positive electrode current collector is preferably 5 μm or more and 20 μm or less, and 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 as the positive electrode current collector is preferably 1% by mass or less.

5) Electrolyte As the electrolyte, for example, a liquid nonaqueous electrolyte or a gelled nonaqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

Examples of electrolyte salts include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoromethane 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 salt is preferably one that is difficult to oxidize even at a high potential, and LiPF ₆ is most preferred.

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

  As the organic solvent, a mixed solvent in which at least two of the group consisting of propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed, and a mixed solvent containing γ-butyrolactone (GBL) are preferable. . By using these mixed solvents, a secondary battery excellent in high temperature performance can be obtained.

  The gel nonaqueous electrolyte is prepared by combining a liquid nonaqueous electrolyte and a polymer material. Examples of the polymeric material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

  Alternatively, as the non-aqueous electrolyte, in addition to the liquid non-aqueous electrolyte and the gel-like non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, and the like are used. Also good.

  A room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15 ° C. or more and 25 ° C. or less) among organic salts formed by a combination of an organic cation and an anion. Room temperature molten salt includes room temperature molten salt that exists as a liquid alone, room temperature molten salt that becomes liquid when mixed with electrolyte salt, room temperature molten salt that becomes liquid when dissolved in organic solvent, or a mixture thereof It is. In general, the melting point of a room temperature molten salt used for a nonaqueous electrolyte secondary 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 salt in a polymer material and solidifying it.

  The inorganic solid electrolyte is a solid material having Li ion conductivity. An inorganic solid electrolyte contains the solid electrolyte which can be used as above-mentioned insulating particle, for example.

6) Separator The separator is made of, for example, a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films can be melted at a constant temperature to interrupt the current.

7) Exterior member As the exterior member, for example, a container made of a laminate film or a metal container can be used.

  The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

  As the laminate film, a multilayer film including a plurality of resin layers and a metal layer interposed between these resin layers is used. The resin layer includes, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). It is preferable that a metal layer consists of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be formed into the shape of the exterior member by sealing by heat sealing.

  The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and still more preferably 0.2 mm or less.

  The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When an aluminum alloy contains transition metals, such as iron, copper, nickel, and chromium, it is preferable that the content is 100 ppm or less (mass ratio).

  The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, a flat type (thin type), a square type, a cylindrical type, a coin type, or a button type. The exterior member is, for example, a small battery exterior member mounted on a portable electronic device or the like, a large battery exterior member mounted on a vehicle such as a two- to four-wheeled automobile or a railway vehicle, depending on the battery size. May be.

8) Negative electrode terminal The negative electrode terminal can be formed of a material that is electrochemically stable and has conductivity at the Li storage / release potential of the negative electrode active material described above. Specifically, the negative electrode terminal material includes copper, nickel, stainless steel, or aluminum, or at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. An aluminum alloy is mentioned. As a material for the negative electrode terminal, aluminum or an aluminum alloy is preferably used. In order to reduce the contact resistance with the negative electrode current collector, the negative electrode terminal is preferably made of the same material as the negative electrode current collector.

9) Positive electrode terminal The positive electrode terminal is formed of a material that is electrically stable and has conductivity in a potential range (vs. Li ^/ Li ⁺ ) of 3 V or more and 5 V or less with respect to the oxidation-reduction potential of lithium. Examples of the material of the positive electrode terminal include aluminum or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

  Next, the secondary battery according to the first embodiment will be described more specifically with reference to the drawings.

  FIG. 2 is a cross-sectional view schematically showing an example of the secondary battery according to the first embodiment. FIG. 3 is an enlarged cross-sectional view of part A of the secondary battery shown in FIG.

  The secondary battery 100 shown in FIGS. 2 and 3 includes the bag-shaped exterior member 2 shown in FIG. 2, the electrode group 1 shown in FIGS. 2 and 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. An electrolyte (not shown) is held by the electrode group 1.

  The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed therebetween.

  As shown in FIG. 2, the electrode group 1 is a flat wound electrode group. As shown in FIG. 3, the flat wound electrode group 1 includes a negative electrode 3, an insulating layer 4, and a positive electrode 5. The insulating layer 4 is interposed between the negative electrode 3 and the positive electrode 5.

  The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the negative electrode 3, the portion located in the outermost shell of the wound electrode group 1 has a negative electrode active material-containing layer 3 b formed only on the inner surface side of the negative electrode current collector 3 a as shown in FIG. 3. In other portions of the negative electrode 3, negative electrode active material-containing layers 3b are formed on both surfaces of the negative electrode current collector 3a.

  The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both surfaces thereof.

  As shown in FIG. 2, the negative electrode terminal 6 and the positive electrode terminal 7 are located in the vicinity of the outer peripheral end of the wound electrode group 1. The negative electrode terminal 6 is connected to a part of the negative electrode current collector 3a of the negative electrode 3 located in the outermost shell. Moreover, the positive electrode terminal 7 is connected to the positive electrode current collector 5a of the positive electrode 5 located in the outermost shell. 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. The bag-shaped exterior member 2 is heat-sealed by a thermoplastic resin layer disposed on the inner surface thereof.

  The secondary battery according to the first embodiment is not limited to the secondary battery having the configuration illustrated in FIGS. 2 and 3, and may be, for example, a battery having the configuration illustrated in FIGS. 4 to 6.

  First, an electrode assembly of a first example that can be provided in the secondary battery according to the first embodiment will be described with reference to FIG.

  FIG. 4 is a schematic cross-sectional view of a first example electrode assembly that can be provided in the secondary battery according to the first embodiment.

  An electrode composite 10A shown in FIG. 4 includes a positive electrode active material-containing layer 5b, an insulating layer 4, a negative electrode active material-containing layer 3b, and two current collectors 8. As illustrated, in the electrode assembly 10A, the insulating layer 4 is located between the positive electrode active material-containing layer 5b and the negative electrode active material-containing layer 3b. The insulating layer 4 is in contact with one surface of the positive electrode active material-containing layer 5b and one surface of the negative electrode active material-containing layer 3b. The surface of the positive electrode active material-containing layer 5 b that is not in contact with the insulating layer 4 is in contact with one current collector 8. Similarly, the surface of the negative electrode active material-containing layer 3 b that is not in contact with the insulating layer 4 is in contact with the other current collector 8. Thus, the electrode composite 10A has a structure in which one current collector 8, the negative electrode active material-containing layer 3b, the insulating layer 4, the positive electrode active material-containing layer 5b, and the other current collector 8 are laminated in this order. doing. In other words, the electrode assembly 10A of the example shown in FIG. 4 includes one set of electrode sets 12 including the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b, and the insulating layer 4 positioned therebetween. It is an electrode body.

  A bipolar electrode such as the electrode assembly 10A can be manufactured as follows, for example. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side of the current collector. Next, the applied slurry is dried to obtain a laminate of the negative electrode active material-containing layer and the current collector. Subsequently, a positive electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to the other surface of the current collector. Next, the applied slurry is dried to obtain an electrode set in which the negative electrode active material-containing layer, the current collector, and the positive electrode active material-containing layer are laminated. Thereafter, this electrode set is pressed. In this way, a bipolar electrode can be obtained.

  Next, a second example of the electrode assembly that can be included in the secondary battery according to the first embodiment will be described with reference to FIG.

  FIG. 5 is a schematic cross-sectional view of a second example electrode assembly that can be included in the secondary battery according to the first embodiment.

  The electrode complex 10B shown in FIG. 5 includes a plurality of, for example, four electrodes 11 having a bipolar structure. As shown in FIG. 5, each electrode 11 was formed on the current collector 8, the positive electrode active material-containing layer 5 b formed on one surface of the current collector 8, and the other surface of the current collector 8. And a negative electrode active material-containing layer 3b. As shown in FIG. 5, these electrodes 11 are arranged so that the positive electrode active material-containing layer 5 b of one electrode 11 faces the negative electrode active material-containing layer 3 b of the other one electrode 11 through the insulating layer 4. Has been placed.

  The electrode composite 10B further includes the other two insulating layers 4, the other two current collectors 8, the other positive electrode active material-containing layer 5b, and the other negative electrode active material-containing layer 3b. Contains. As shown in FIG. 5, one positive electrode active material-containing layer 5 b faces the negative electrode active material-containing layer 3 b of the electrode 11 positioned at the uppermost stage of the stacked body of the electrodes 11 through one insulating layer 4. . The surface of the positive electrode active material-containing layer 5 b that is not in contact with the insulating layer 4 is in contact with one current collector 8. In addition, one negative electrode active material-containing layer 3 b faces the positive electrode active material-containing layer 5 b of the electrode 11 positioned at the lowermost stage of the stacked body of the electrodes 11 via one insulating layer 4. The surface of the negative electrode active material-containing layer 3 b that is not in contact with the insulating layer 4 is in contact with one current collector 8.

  The electrode composite that can be included in the secondary battery according to the first embodiment can be thinned by bringing the positive electrode active material-containing layer, the insulating layer, and the negative electrode active material-containing layer into close contact with each other. Therefore, in the secondary battery according to the first embodiment, a large number of electrode sets including the positive electrode active material-containing layer, the negative electrode active material-containing layer, and the insulating layer positioned therebetween can be stacked. Thus, it is possible to provide a secondary battery that is thin, requires less space, has a large capacity, and suppresses self-discharge. 5 includes five electrode sets 12 of the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b, and the insulating layer 4 positioned therebetween. However, the number of electrode sets 12 can be appropriately selected according to the design of the shape and size of the battery.

  FIG. 6 is a schematic cross-sectional view of an example secondary battery according to the embodiment.

  As shown in FIG. 6, the secondary battery 100 includes an electrode assembly 10 </ b> C housed in the exterior member 2. The illustrated electrode complex 10C has the same structure as the electrode complex 10B shown in FIG. A positive electrode current collecting tab 8A is provided at one end of the current collector 8 located at the uppermost stage of the electrode composite 10C. On the other hand, a negative electrode current collecting tab 8B is provided at one end of the current collector 8 located at the lowest stage of the electrode composite 10C. A negative electrode terminal and a positive electrode terminal (not shown) are connected to the positive electrode current collecting tab 8A and the negative electrode current collecting tab 8B, respectively, and the negative electrode terminal and the positive electrode terminal extend to the outside of the exterior member 2.

  In FIG. 6, like the electrode composite 10B of FIG. 5, an electrode composite including five sets of electrode sets of the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b, and the insulating layer 4 positioned therebetween. The secondary battery 100 including 10C is shown as an example. However, the secondary battery according to the first embodiment includes an electrode composite including a number of electrode sets other than five, for example, one electrode set similar to the electrode composite 10A shown in FIG. Alternatively, an electrode composite including two or more electrode sets may be provided.

  The secondary battery according to the first embodiment includes a negative electrode active material-containing layer, a positive electrode active material-containing layer, and an insulating layer. The insulating layer is provided between the negative electrode active material-containing layer and the positive electrode active material-containing layer, and includes insulating particles. The particle size distribution of the insulating particles in the insulating layer includes two or more peaks. In the secondary battery having such a configuration, self-discharge is suppressed.

(Second Embodiment)
According to the second embodiment, an assembled battery is provided. The assembled battery according to the second embodiment includes a plurality of secondary batteries according to the first embodiment.

  In the assembled battery according to the second embodiment, the single cells may be arranged by being electrically connected in series or in parallel, or may be arranged by combining series connection and parallel connection.

  Next, an example of the assembled battery according to the second embodiment will be described with reference to the drawings.

  FIG. 7 is a perspective view schematically showing an example of an assembled battery according to the second embodiment. The assembled battery 200 shown in FIG. 7 includes five unit cells 100, four bus bars 21, a positive electrode side lead 22, and a negative electrode side lead 23. Each of the five single cells 100 is a secondary battery according to the second embodiment.

  The bus bar 21 connects the negative electrode terminal 6 of one unit cell 100 and the positive electrode terminal 7 of the unit cell 100 located adjacent thereto. In this way, the five unit cells 100 are connected in series by the four bus bars 21. That is, the assembled battery 200 of FIG. 7 is a 5-series assembled battery.

  As shown in FIG. 7, among the five unit cells 100, the positive terminal 7 of the unit cell 100 located at the left end of one row is connected to the positive lead 22 for external connection. Moreover, the negative electrode terminal 6 of the unit cell 100 located at the right end of the other row among the five unit cells 100 is connected to the negative electrode side lead 23 for external connection.

  The assembled battery according to the second embodiment includes the secondary battery according to the first embodiment. Therefore, self-discharge is suppressed.

(Third embodiment)
According to the third embodiment, a battery pack is provided. This battery pack includes the assembled battery according to the second embodiment. The battery pack may include a single secondary battery according to the first embodiment instead of the assembled battery according to the second embodiment.

  The battery pack according to the third embodiment can further include a protection circuit. The protection circuit has a function of controlling charging / discharging of the secondary battery. Or you may use the circuit contained in the apparatus (for example, electronic device, a motor vehicle, etc.) which uses a battery pack as a power supply as a protection circuit of a battery pack.

  The battery pack according to the third embodiment can further include an external terminal for energization. The external terminal for energization is for outputting a current from the secondary battery to the outside and / or for inputting a current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for energization. Further, when charging the battery pack, a charging current (including regenerative energy of motive power of an automobile or the like) is supplied to the battery pack through an external terminal for energization.

  Next, an example of a battery pack according to the third embodiment will be described with reference to the drawings.

  FIG. 8 is an exploded perspective view schematically showing an example of the battery pack according to the third embodiment. FIG. 9 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG.

  The battery pack 300 shown in FIG.8 and FIG.9 is equipped with the storage container 31, the lid | cover 32, the protection sheet 33, the assembled battery 200, the printed wiring board 34, the wiring 35, and the insulating board which is not shown in figure. .

  The container 31 is configured to accommodate the protective sheet 33, the assembled battery 200, the printed wiring board 34, and the wiring 35. The lid 32 houses the assembled battery 200 and the like by covering the housing container 31. Although not shown, the storage container 31 and the lid 32 are provided with an opening or a connection terminal for connection to an external device or the like.

  The protective sheet 33 is disposed on both inner side surfaces of the storage container 31 in the long side direction and on the inner side surface in the short side direction facing the printed wiring board 34 via the assembled battery 200. The protective sheet 33 is made of, for example, resin or rubber.

  The assembled battery 200 includes a plurality of single cells 100, a positive electrode side lead 22, a negative electrode side lead 23, and an adhesive tape 24. The assembled battery 200 may include one single battery 100.

  The unit cell 100 has a structure shown in FIGS. 2 and 3, for example. Alternatively, the unit cell 100 may have the structure shown in FIG. At least one of the plurality of unit cells 100 is a secondary battery according to the first embodiment. The plurality of single cells 100 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. Each of the plurality of unit cells 100 is electrically connected in series as shown in FIG. The plurality of single cells 100 may be electrically connected in parallel, or may be connected in combination of series connection and parallel connection. When the plurality of single cells 100 are connected in parallel, the battery capacity is increased as compared to the case where they are connected in series.

  The adhesive tape 24 fastens a plurality of unit cells 100. Instead of the adhesive tape 24, a plurality of single cells 100 may be fixed using a heat shrink tape. In this case, the protective sheets 33 are arranged on both side surfaces of the assembled battery 200, the heat shrink tape is circulated, and then the heat shrink tape is heat shrunk to bind the plurality of unit cells 100 together.

  One end of the positive electrode side lead 22 is connected to the positive electrode terminal 7 of the unit cell 100 located in the lowermost layer in the stacked body of the unit cells 100. One end of the negative electrode side lead 23 is connected to the negative electrode terminal 6 of the unit cell 100 located in the uppermost layer in the stacked body of the unit cells 100.

  The printed wiring board 34 includes a positive connector 341, a negative connector 342, a thermistor 343, a protection circuit 344, wirings 345 and 346, an external terminal 347 for energization, a positive wiring 348a, and a negative wiring. 348b. One main surface of the printed wiring board 34 faces the surface in which the negative electrode terminal 6 and the positive electrode terminal 7 extend in the assembled battery 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the assembled battery 200.

  The positive connector 341 is provided with a through hole. By inserting the other end of the positive electrode side lead 22 into this through hole, the positive electrode side connector 341 and the positive electrode side lead 22 are electrically connected. The negative electrode side connector 342 is provided with a through hole. By inserting the other end of the negative electrode side lead 23 into this through hole, the negative electrode side connector 342 and the negative electrode side lead 23 are electrically connected.

  The thermistor 343 is fixed to one main surface of the printed wiring board 34. The thermistor 343 detects the temperature of each unit cell 100 and transmits the detection signal to the protection circuit 344.

  The external terminal 347 for energization is fixed to the other main surface of the printed wiring board 34. The external terminal 347 for energization is electrically connected to a device existing outside the battery pack 300.

  The protection circuit 344 is fixed to the other main surface of the printed wiring board 34. The protection circuit 344 is connected to the external terminal 347 for energization through the plus side wiring 348a. The protection circuit 344 is connected to the external terminal 347 for energization via the minus side wiring 348b. Further, the protection circuit 344 is electrically connected to the positive connector 341 via the wiring 345. The protection circuit 344 is electrically connected to the negative connector 342 through the wiring 346. Further, the protection circuit 344 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

  The protection circuit 344 controls charging / discharging of the plurality of single cells 100. In addition, the protection circuit 344 is based on a detection signal transmitted from the thermistor 343 or a detection signal transmitted from each unit cell 100 or the assembled battery 200, and an external terminal for energizing the protection circuit 344 and an external device. The electrical connection with 347 is cut off.

  As a detection signal transmitted from the thermistor 343, for example, a signal detected that the temperature of the unit cell 100 is equal to or higher than a predetermined temperature can be cited. As a detection signal transmitted from each unit cell 100 or the assembled battery 200, for example, a signal that detects overcharge, overdischarge, and overcurrent of the unit cell 100 can be cited. When detecting an overcharge or the like for each unit cell 100, 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 100.

  Note that as the protection circuit 344, a circuit included in a device (for example, an electronic device, an automobile, or the like) that uses the battery pack 300 as a power source may be used.

  Such a battery pack 300 is used, for example, in applications that require excellent cycle performance when a large current is taken out. Specifically, the battery pack 300 is used, for example, as a power source for electronic devices, a stationary battery, a vehicle-mounted battery, or a railcar battery. An example of the electronic device is a digital camera. This battery pack 300 is particularly preferably used as a vehicle-mounted battery.

  Further, the battery pack 300 includes the external terminals 347 for energization as described above. Accordingly, the battery pack 300 can output the current from the assembled battery 200 to the external device and the current from the external device to the assembled battery 200 via the external terminal 347 for energization. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 347 for energization. When charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 347 for energization. When this battery pack 300 is used as a vehicle-mounted battery, regenerative energy of vehicle power can be used as a charging current from an external device.

  The battery pack 300 may include a plurality of assembled batteries 200. In this case, the plurality of assembled batteries 200 may be connected in series, may be connected in parallel, or may be connected by combining series connection and parallel connection. Further, the printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode side lead 22 and the negative electrode side lead 23 may be used as external terminals for energization.

  The battery pack according to the third embodiment includes the secondary battery according to the first embodiment or the assembled battery according to the second embodiment. Therefore, self-discharge is suppressed.

(Fourth embodiment)
According to a fourth embodiment, a vehicle is provided. This vehicle is equipped with the battery pack according to the third embodiment.

  In the vehicle according to the fourth embodiment, the battery pack recovers, for example, regenerative energy of the power of the vehicle.

  Examples of the vehicle according to the fourth embodiment include, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, an assist bicycle, and a railway vehicle.

  The mounting position of the battery pack in the vehicle according to the fourth embodiment is not particularly limited. For example, when the battery pack is mounted on an automobile, the battery pack can be mounted on the engine room of the vehicle, behind the vehicle body, or under the seat.

  Next, an example of a vehicle according to the fourth embodiment will be described with reference to the drawings.

  FIG. 10 is a cross-sectional view schematically illustrating an example of a vehicle according to the fourth embodiment.

  A vehicle 400 shown in FIG. 10 includes a vehicle main body 40 and the battery pack 300 according to the third embodiment.

  A vehicle 400 shown in FIG. 10 is a four-wheeled vehicle. As the vehicle 400, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, an assist bicycle, and a railway vehicle can be used.

  This vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the battery pack 300 may be connected in series, may be connected in parallel, or may be connected by a combination of series connection and parallel connection.

  Battery pack 300 is mounted in an engine room located in front of vehicle body 40. The mounting position of the battery pack 300 is not particularly limited. The battery pack 300 may be mounted behind the vehicle body 40 or under the seat. The battery pack 300 can be used as a power source for the vehicle 400. In addition, the battery pack 300 can recover the regenerative energy of the power of the vehicle 400.

  Next, an embodiment of a vehicle according to the fourth embodiment will be described with reference to FIG.

  FIG. 11 is a diagram schematically illustrating another example of the vehicle according to the fourth embodiment. A vehicle 400 shown in FIG. 11 is an electric vehicle.

  A vehicle 400 shown in FIG. 11 includes a vehicle main body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 that is a higher-level control means of the vehicle power supply 41, and an external terminal (external power supply). Terminal 43), an inverter 44, and a drive motor 45.

  The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine room, behind a vehicle body or under a seat. In addition, in the vehicle 400 shown in FIG. 11, the mounting location of the vehicle power supply 41 is schematically shown.

  The vehicle power supply 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

  The three battery packs 300a, 300b, and 300c are electrically connected in series. The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device (VTM: Voltage Temperature Monitoring) 301a. The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300 a, 300 b, and 300 c can be detached independently and can be replaced with another battery pack 300.

  Each of the assembled batteries 200a to 200c includes a plurality of single cells connected in series. At least one of the plurality of unit cells is a secondary battery according to the second embodiment. The assembled batteries 200a to 200c are charged and discharged through the positive terminal 413 and the negative terminal 414, respectively.

  The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c in order to collect information related to the maintenance of the vehicle power supply 41, and the battery management device 411 includes the single batteries included in the assembled batteries 200a to 200c included in the vehicle power supply 41. Information on the voltage and temperature of the battery 100 is collected.

  A communication bus 412 is connected between the battery management device 411 and the assembled battery monitoring devices 301a to 301c. The communication bus 412 is configured to share a set of communication lines with a plurality of nodes (battery management device and one or more assembled battery monitoring devices). The communication bus 412 is a communication bus configured based on, for example, a CAN (Control Area Network) standard.

  The assembled battery monitoring devices 301a to 301c measure the voltage and temperature of individual cells constituting the assembled batteries 200a to 200c based on a command from the battery management device 411 through communication. However, the temperature can be measured at only a few locations per assembled battery, and the temperature of all the cells need not be measured.

  The vehicle power supply 41 can also include an electromagnetic contactor (for example, a switch device 415 shown in FIG. 11) for turning on and off the connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a precharge switch (not shown) that is turned on when the assembled batteries 200a to 200c are charged, and a main switch (not shown) that is turned on when the battery output is supplied to the load. Is included. The precharge switch and the main switch include a relay circuit (not shown) that is turned on or off by a signal supplied to a coil disposed in the vicinity of the switch element.

  The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 controls the output voltage based on a control signal from the battery management device 411 or the vehicle ECU 42 for controlling the entire vehicle operation.

  The drive motor 45 is rotated by electric power supplied from the inverter 44. This rotation is transmitted to the axle and the drive wheels W via, for example, a differential gear unit.

  Although not shown, the vehicle 400 includes a regenerative brake mechanism. The regenerative brake mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts the kinetic energy into regenerative energy as electric energy. The regenerative energy recovered by the regenerative brake mechanism is input to the inverter 44 and converted into a direct current. The direct current is input to the vehicle power supply 41.

  One terminal of the connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41 via a current detection unit (not shown) in the battery management device 411. The other terminal of the connection line L <b> 1 is connected to the negative input terminal of the inverter 44.

  One terminal of the connection line L <b> 2 is connected to the positive terminal 413 of the vehicle power supply 41 via the switch device 415. The other terminal of the connection line L2 is connected to the positive input terminal of the inverter 44.

  The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to an external power source, for example.

  The vehicle ECU 42 manages the entire vehicle by cooperatively controlling the battery management device 411 together with other devices in response to an operation input from the driver or the like. Between the battery management device 411 and the vehicle ECU 42, data transfer relating to maintenance of the vehicle power source 41 such as the remaining capacity of the vehicle power source 41 is performed via a communication line.

  The vehicle according to the fourth embodiment is equipped with the battery pack according to the third embodiment. Therefore, since the self-discharge of the battery pack is suppressed, the reliability of the vehicle is high.

[Example]
Examples will be described in detail below.

Example 1
<Production of negative electrode>
As the negative electrode active material, 90% by mass of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) powder having a spinel structure was used. 7% by mass of graphite was used as the conductive agent, and 3% by mass of PVdF was used as the binder. These components were mixed with N-methylpyrrolidone (NMP) to prepare a slurry. The slurry is applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, temporarily dried at 80 ° C., and then dried at 130 ° C. to obtain a laminate of the negative electrode active material and the current collector. It was. The laminate was pressed to obtain a negative electrode.

<Preparation of positive electrode>
As the positive electrode active material, lithium cobaltate (LiCoO ₂ ) was used. As a conductive agent, 3% by mass of acetylene black and 3% by mass of graphite were used with respect to 90% by mass of lithium cobalt oxide. As a binder, 4% by mass of polyvinylidene fluoride (PVdF) was used. The above components were added to N-methylpyrrolidone (NMP) and mixed to prepare a slurry. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm and dried to obtain a laminate of a positive electrode active material and a current collector. The laminate was pressed to obtain a positive electrode.

<Preparation of insulating layer>
As insulating particles, 92% by mass of Li ₇ La ₃ Zr ₂ O ₁₂ powder was used. In the particle size distribution of the insulating particles used, the particle diameter (first particle diameter) corresponding to the peak having the strongest peak intensity (first peak), and then the peak having the second highest peak intensity (second peak). The particle diameters corresponding to (second particle diameter) were 0.11 μm and 0.30 μm, respectively. As a binder, 3% by mass of styrene butadiene rubber and 3% by mass of carboxymethyl cellulose were used. The above components were added to water and mixed to prepare a slurry. This slurry was applied to both sides of the negative electrode at a thickness of 10 μm and dried.

<Production of electrode group>
A positive electrode and a negative electrode on which an insulating layer was formed were laminated to obtain a laminate. Next, this laminate was wound in a spiral shape. The electrode group after winding was heated and pressed at 80 ° C. to produce a flat electrode group. The obtained electrode group is housed in a pack made of a laminate film having a three-layer structure of nylon layer / aluminum layer / polyethylene layer and a thickness of 0.1 mm, and dried in a vacuum at 80 ° C. for 16 hours. did.

<Preparation of liquid nonaqueous electrolyte>
1 mol / L of LiPF ₆ as an electrolyte salt was dissolved in a mixed solvent of propylene carbonate (PC) and diethyl carbonate (DEC) (volume ratio 1: 2) to obtain a liquid nonaqueous electrolyte.

  After injecting the liquid non-aqueous electrolyte into the laminate film pack containing the electrode group, the pack was completely sealed by heat sealing. Thereby, a secondary battery was obtained.

(Example 2-9)
A secondary battery was fabricated in the same manner as in Example 1, except that the first particle diameter and the second particle diameter were set to the values shown in Table 2 in the particle size distribution of the insulating particles.

(Examples 10-14)
Insulating particles of the materials shown in Table 1 were used as the insulating particles, and in the particle size distribution, the first particle diameter and the second particle diameter were changed to the values shown in Table 2, and Example 1 and A secondary battery was produced in the same manner.

(Examples 15-17)
As the negative electrode active material, the compounds shown in Table 1 were used. Further, in the particle size distribution of the insulating particles, the first particle diameter and the second particle diameter were set to values shown in Table 2. A secondary battery was fabricated in the same manner as in Example 1 except for these.

(Examples 18-19)
As the positive electrode active material, the compounds shown in Table 1 were used. Further, in the particle size distribution of the insulating particles, the first particle diameter and the second particle diameter were set to values shown in Table 2. A secondary battery was fabricated in the same manner as in Example 1 except for these.

(Example 20)
When the insulating layer was produced, a secondary battery was produced in the same manner as in Example 1 except that the slurry of the material of the insulating layer was applied on both sides of the positive electrode instead of being applied on both sides of the negative electrode.

(Example 21)
Example of manufacturing the insulating layer, except that the slurry of the insulating layer material was applied to both sides of the negative electrode and both sides of the positive electrode in a thickness of 5 μm instead of being applied to both sides of the negative electrode at a thickness of 10 μm. A secondary battery was produced in the same manner as in Example 1.

(Example 22)
Except that mixed particles of Li ₇ La ₃ Zr ₂ O ₁₂ powder having an average particle diameter of 0.50 μm and Al ₂ O ₃ powder having an average particle diameter of 1.0 μm were used as insulating particles. A secondary battery was fabricated in the same manner as in Example 1.

(Comparative Example 1-4)
A secondary battery was fabricated in the same manner as in Example 1 except that insulating particles having a particle size distribution having a single peak corresponding to the first particle diameter shown in Table 4 were used as the insulating particles. .

(Comparative Example 5-16)
Rechargeable batteries in the same manner as in Examples 10-21 except that insulating particles having a particle size distribution having a single peak corresponding to the first particle diameter shown in Table 4 were used as insulating particles. Was made.

(Comparative Example 17)
In the same manner as in Example 1, except that an electrode group was prepared using a laminate obtained by laminating a positive electrode, a cellulose separator having a thickness of 15 μm, and a negative electrode without producing an insulating layer. A secondary battery was produced.

(Comparative Example 18)
In the same manner as in Example 1, except that an electrode group was prepared using a laminate obtained by laminating a positive electrode, a cellulose separator having a thickness of 6 μm, and a negative electrode without producing an insulating layer. A secondary battery was produced.

  Table 1 below summarizes the materials used for the insulating particles, the negative electrode active material, and the positive electrode active material in Example 1-22. In addition, when an insulating layer is manufactured, an electrode coated with a material for the insulating layer is also shown.

  In Table 2 below, the particle diameter (first particle diameter) corresponding to the peak (first peak) having the strongest peak intensity in the particle size distribution of the insulating particles used in Example 1-22, and then the peak The particle diameter (second particle diameter) corresponding to the strong peak (second peak) is summarized.

  Table 3 below summarizes the materials used for the insulating particles, the negative electrode active material, and the positive electrode active material in Comparative Example 1-18. In addition, when an insulating layer is manufactured, an electrode coated with a material for the insulating layer is also shown.

  Table 4 below summarizes the particle sizes corresponding to the particle size distribution of the insulating particles used in Comparative Example 1-16. In Comparative Examples 17 and 18, since a cellulose separator was used instead of the insulating layer, there was no particle size distribution.

  The secondary battery obtained in Example 1-22 and the secondary battery obtained in Comparative Example 1-18 were each charged to 2.5 V, and then left in a 60 ° C. environment for 4 weeks to determine the remaining capacity. It was measured. Here, the remaining capacity (%) was defined as “remaining capacity (%) = capacity after storage / capacity before storage × 100”. Moreover, the thickness of the insulating layer in each secondary battery was confirmed by the method described above.

  The results for Examples 1-22 are summarized in Table 5. Further, the thicknesses of the insulating layers confirmed in the respective secondary batteries are also summarized.

  The results in Comparative Example 1-18 are summarized in Table 6. Further, the thicknesses of the insulating layers confirmed in the respective secondary batteries are also summarized. In addition, about the comparative examples 17 and 18, the thickness of a cellulose separator is shown.

  From the results shown in Table 5 and Table 6, it can be seen that the secondary battery produced in Example 1-22 has a higher remaining capacity than the secondary batteries produced in Comparative Examples 1-16 and 18. That is, it can be seen that the secondary battery of Example 1-22 had less self-discharge amount than the secondary batteries of Comparative Examples 1-16 and 18.

  Comparing the results of Example 6 and Examples 15-17 having the same particle size distribution for the insulating particles in the insulating layer, it can be seen that the self-discharge amount varies depending on the difference in the compound used as the negative electrode active material. The residual capacity in Example 17 using graphite as the negative electrode active material was lower than that in the other examples, but was higher than that in Comparative Example 12 using graphite as well. Also, in Examples 15 and 16, the remaining capacity was higher than those of Comparative Examples 10 and 11 using the same negative electrode active material.

  From the comparison between the results of Example 6 and the results of Examples 18 and 19, even when various positive electrode active materials were used, by using insulating particles containing two or more peaks in the particle size distribution for the insulating layer, It can be seen that a similar remaining capacity can be obtained.

  The secondary battery of Comparative Example 17 exhibited a residual capacity comparable to that of the secondary battery of Example 1-22. However, in Comparative Example 17, in order to achieve a residual capacity comparable to that of Example 1-22, a cellulose separator having a thickness (15 μm) about three times the thickness of the insulating layer in Example 1-22 was used. Used. The secondary battery of Comparative Example 17 becomes thick, and a high energy density cannot be obtained.

  From the comparison between Example 1-22 and Comparative Example 1-18, in the secondary battery using the insulating layer including the insulating particles including two or more peaks in the particle size distribution, the interval between the negative electrode layer and the positive electrode layer is It can be seen that self-discharge could be suppressed while the thickness was reduced. This indicates that by using insulating particles having two or more peaks in the particle size distribution in the insulating layer, the energy density can be increased and self-discharge can be suppressed.

(Examples 23-28)
A secondary battery was fabricated in the same manner as in Example 1 except that the first particle diameter and the second particle diameter were set to the values shown in Table 8 in the particle size distribution of the insulating particles.

The first particle size and the second particle size were controlled as follows. For each example, first insulating particles (Li ₇ La ₃ Zr ₂ O ₁₂ powder) having a particle size distribution including a single peak corresponding to the first particle diameters shown in Table 8 were prepared. . It was also prepared second insulating particles having a particle size distribution including a single peak corresponding to the second diameter of the values shown in Table _{8 (Li 7 La 3 Zr 2} O 12 powder). The first insulating particles and the second insulating particles were mixed. By doing so, the particle diameter (first particle diameter) corresponding to the peak (first peak) having the strongest peak intensity in the particle size distribution of the insulating particles, and then the peak having the second highest peak intensity (second peak). The particle diameter (second particle diameter) corresponding to (peak) was set to the value shown in Table 8.

(Examples 29-35)
In the particle size distribution of the insulating particles, the first particle diameter and the second particle diameter were set to values shown in Table 8. Further, the ratio of the peak intensity of the peak (first peak) having the strongest peak intensity in the particle size distribution of the insulating particles to the peak intensity of the peak having the second highest peak intensity (second peak) (first peak). The intensity / second peak intensity was set to the values shown in Table 8. A secondary battery was fabricated in the same manner as in Example 1 except for these.

  The first particle size and the second particle size were controlled by the same method as in Examples 23-28. The peak intensity ratio between the first peak and the second peak was controlled by changing the mixing ratio of the first insulating particles and the second insulating particles. For example, when the ratio of the first insulating particles is increased, the value of the peak intensity ratio increases.

  Table 7 below summarizes the materials used for the insulating particles, the negative electrode active material, and the positive electrode active material in Examples 23-35. In addition, when an insulating layer is manufactured, an electrode coated with a material for the insulating layer is also shown.

  In Table 8 below, the particle diameter (first particle diameter) corresponding to the peak (first peak) having the strongest peak intensity in the particle size distribution of the insulating particles used in Examples 23 to 35, and then the peak The particle diameter (second particle diameter) corresponding to the strong peak (second peak) is summarized. The ratio of the peak intensity of the first peak to the peak intensity of the second peak (first peak intensity / second peak intensity) is also shown.

(Examples 36-47)
The insulating particles of the material shown in Table 9 were used as the insulating particles, and the first particle diameter and the second particle diameter were set to values shown in Table 10 in the particle size distribution. Moreover, the compound shown in Table 9 was used as a negative electrode active material and a positive electrode active material. A secondary battery was fabricated in the same manner as in Example 1 except for these.

(Example 48)
A secondary battery was fabricated in the same manner as in Example 41, except that when the insulating layer was formed, the slurry of the insulating layer material was applied to both sides of the positive electrode instead of being applied to both sides of the negative electrode.

(Example 49)
Example of manufacturing the insulating layer, except that the slurry of the insulating layer material was applied to both sides of the negative electrode and both sides of the positive electrode in a thickness of 5 μm instead of being applied to both sides of the negative electrode at a thickness of 10 μm. A secondary battery was produced in the same manner as in No.41.

(Examples 50-51)
A secondary battery was fabricated in the same manner as in Example 41 except that the compounds shown in Table 9 were used as the positive electrode active material.

(Examples 52-58)
Except that the ratio of the peak intensity of the first peak to the peak intensity of the second peak (first peak intensity / second peak intensity) in the particle size distribution of the insulating particles was set to the value shown in Table 10. A secondary battery was produced in the same manner as in Example 51.

  Table 9 below summarizes the materials used for the insulating particles, the negative electrode active material, and the positive electrode active material in Examples 36-58. In addition, when an insulating layer is manufactured, an electrode coated with a material for the insulating layer is also shown.

  Table 10 below summarizes the first particle diameter and the second particle diameter in the particle size distribution of the insulating particles used in Examples 36-58. The ratio of the peak intensity of the first peak to the peak intensity of the second peak (first peak intensity / second peak intensity) is also shown.

(Comparative Example 19-20)
A secondary battery was fabricated in the same manner as in Example 1 except that insulating particles having a particle size distribution having a single peak corresponding to the first particle diameter shown in Table 12 were used as the insulating particles. .

(Comparative Example 21-24)
A secondary battery was fabricated in the same manner as in Example 36 except that insulating particles having a particle size distribution having a single peak corresponding to the first particle diameter shown in Table 12 were used as insulating particles. .

(Comparative Example 25-28)
Rechargeable batteries in the same manner as in Examples 48-51 except that insulating particles having a particle size distribution having a single peak corresponding to the first particle diameter shown in Table 12 were used as insulating particles. Was made.

  Table 11 below summarizes the materials used for the insulating particles, the negative electrode active material, and the positive electrode active material in Comparative Examples 19-28. In addition, when an insulating layer is manufactured, an electrode coated with a material for the insulating layer is also shown.

  Table 12 below summarizes the particle sizes corresponding to the particle size distribution of the insulating particles used in Comparative Examples 19-28.

  The secondary batteries obtained in Examples 23-58 and the secondary batteries obtained in Comparative Examples 19-28 were each charged to 2.5 V, and then left in a 60 ° C. environment for 4 weeks to determine the remaining capacity. It was measured. Here, the remaining capacity (%) was defined as “remaining capacity (%) = capacity after storage / capacity before storage × 100”. Moreover, the thickness and porosity of the insulating layer in each secondary battery were confirmed by the method described above.

  The results for Examples 23-35 are summarized in Table 13. Moreover, the thickness and the porosity of the insulating layer confirmed in each secondary battery are put together.

  The results for Examples 36-58 are summarized in Table 14. Moreover, the thickness and the porosity of the insulating layer confirmed in each secondary battery are put together.

  The results for Comparative Examples 19-28 are summarized in Table 15. Moreover, the thickness and the porosity of the insulating layer confirmed in each secondary battery are put together.

In Examples 23-35 and Comparative Examples 19-20, Li ₇ La ₃ Zr ₂ O ₁₂ powder as the insulating particles and spinel type lithium titanium oxide Li ₄ Ti ₅ O ₁₂ as the negative electrode active material for any secondary battery. Lithium cobaltate was used as the powder and the positive electrode active material. From the results shown in Table 13 and Table 15, it can be seen that the secondary batteries produced in Examples 23-35 have a higher remaining capacity than the secondary batteries produced in Comparative Examples 19-20. That is, in Examples 23-35, it can be seen that the amount of self-discharge was small as compared with the secondary batteries of Comparative Examples 19-20.

In Examples 36-49 and Comparative Examples 21-26, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ powder as the insulating particles and monoclinic crystal as the negative electrode active material for any secondary battery Type niobium titanium composite oxide Nb ₂ TiO ₇ powder and lithium nickel cobalt manganese composite oxide LiNi _0.5 Co _0.2 Mn _0.3 O ₂ powder were used as the positive electrode active material. From the results of Tables 14 and 15, it can be seen that the secondary batteries produced in Examples 36-49 have a higher remaining capacity than the secondary batteries produced in Comparative Examples 21-26. That is, in Examples 36-49, it can be seen that the amount of self-discharge was small as compared with the secondary batteries of Comparative Examples 21-26.

In Example 50 and Comparative Example 27, for any secondary battery, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ powder was used as insulating particles, and monoclinic niobium titanium composite oxide was used as the negative electrode active material. Nb ₂ TiO ₇ powder, and lithium nickel cobalt manganese composite oxide LiNi _0,6 Co _0.2 Mn _0.2 O ₂ powder were used as the positive electrode active material. From the results of Table 14 and Table 15, it can be seen that the secondary battery produced in Example 50 has a higher remaining capacity than the secondary battery produced in Comparative Example 27. That is, in Example 50, it can be seen that the amount of self-discharge was small as compared with the secondary battery of Comparative Example 27.

In Examples 51-58 and Comparative Example 28, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ powder as the insulating particles and monoclinic niobium titanium as the negative electrode active material for any secondary battery The composite oxide Nb ₂ TiO ₇ powder and the lithium nickel cobalt manganese composite oxide LiNi _0,8 Co _0.1 Mn _0.1 O ₂ powder were used as the positive electrode active material. From the results of Table 14 and Table 15, it can be seen that the secondary battery produced in Examples 51-58 has a higher remaining capacity than the secondary battery produced in Comparative Example 28. That is, in Examples 51-58, it can be seen that the amount of self-discharge was small as compared with the secondary battery of Comparative Example 28.

  As described above, in the secondary battery using the insulating layer including the insulating particles including two or more peaks in the particle size distribution, the self-discharge is performed while the interval between the negative electrode active material-containing layer and the positive electrode active material-containing layer is reduced. It can be seen from a comparison between the example and the comparative example. This indicates that by using insulating particles having two or more peaks in the particle size distribution in the insulating layer, the energy density can be increased and self-discharge can be suppressed.

  The secondary battery according to at least one embodiment and example described above includes a negative electrode active material-containing layer, a positive electrode active material-containing layer, and an insulating layer. The insulating layer is provided between the negative electrode active material-containing layer and the positive electrode active material-containing layer, and includes insulating particles. The particle size distribution of the insulating particles in the insulating layer includes two or more peaks. In the secondary battery having such a configuration, self-discharge is suppressed.

  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.

  DESCRIPTION OF SYMBOLS 1 ... Winding type electrode group, 2 ... Exterior member, 3 ... Negative electrode, 3a ... Negative electrode collector, 3b ... Negative electrode active material containing layer, 4 ... Insulating layer, 5 ... Positive electrode, 5a ... Positive electrode collector, 5b ... Positive electrode active material-containing layer, 6 ... negative electrode terminal, 7 ... positive electrode terminal, 8 ... current collector, 8A ... positive electrode current collector tab, 8B ... negative electrode current collector tab, 10A ... electrode composite, 10B ... electrode composite, 10C ... Electrode composite, 11 ... electrode of bipolar structure, 12 ... electrode assembly, 21 ... bus bar, 22 ... positive electrode side lead, 23 ... negative electrode side lead, 24 ... adhesive tape, 31 ... container, 32 ... lid, 33 ... protective sheet 34 ... Printed circuit board, 35 ... Wiring, 40 ... Vehicle body, 41 ... Power supply for vehicle, 42 ... Electric control device, 43 ... External terminal, 44 ... Inverter, 45 ... Drive motor, 100 ... Secondary battery, 200 ... Assembled battery, 200a ... assembled battery, 200b ... assembled battery, 200 ... battery pack, 300 ... battery pack, 300a ... battery pack, 300b ... battery pack, 300c ... battery pack, 301a ... battery pack monitoring device, 301b ... battery pack monitoring device, 301c ... battery pack monitoring device, 341 ... positive side connector 342 ... Negative electrode side connector, 343 ... Thermistor, 344 ... Protection circuit, 345 ... Wiring, 346 ... Wiring, 347 ... External terminal for energization, 348a ... Positive side wiring, 348b ... Negative side wiring, 400 ... Vehicle, 411 ... Battery management device, 412 ... communication bus, 413 ... positive electrode terminal, 414 ... negative electrode terminal, 415 ... switch device, L1 ... connection line, L2 ... connection line, W ... drive wheel.

Claims (17)

A negative electrode active material-containing layer;
A positive electrode active material-containing layer;
Provided between the negative electrode active material-containing layer and the positive electrode active material-containing layer, and comprising an insulating layer containing insulating particles;
A secondary battery in which a particle size distribution of the insulating particles in the insulating layer includes two or more peaks.   The secondary battery according to claim 1, wherein the two or more peaks include a first peak having the highest peak intensity and a second peak having the second highest peak intensity after the first peak.   The secondary battery according to claim 2, wherein one of the first particle diameter corresponding to the first peak and the second particle diameter corresponding to the second peak is twice or more of the other.   4. The secondary battery according to claim 3, wherein the first particle diameter exceeds 0.1 μm and is 1 μm or less, and the second particle diameter is 0.3 μm or more and 5 μm or less.   The secondary battery according to any one of claims 2 to 4, wherein, in the particle size distribution, the first peak is on a low particle size side with respect to the second peak.   The secondary battery according to any one of claims 1 to 5, wherein at least one of the negative electrode active material-containing layer and the positive electrode active material-containing layer contains the insulating particles.   The secondary battery according to claim 1, wherein the insulating particles include at least one of a metal oxide and a solid electrolyte.   The secondary battery according to claim 7, wherein the insulating particles include the solid electrolyte.   The secondary battery according to any one of claims 1 to 8, further comprising a non-aqueous electrolyte.   The secondary battery according to claim 9, wherein the nonaqueous electrolyte includes a gel-like nonaqueous electrolyte. The negative electrode active material-containing layer is a spinel type lithium titanate, represented by the general formula Ti _1-x M _{x + y} Nb _{2 -y} O _7-σ , where M is Mg, Fe, Ni, Co, W, Ta, and Niobium-titanium composite oxide, which is at least one element selected from the group consisting of Mo, 0 ≦ x <1, 0 ≦ y <1, and −0.3 ≦ σ ≦ 0.3, and a general formula Li _{2 + a} M 1 _{2 -b} Ti _{6 -c} M 2 _d O _{14 + δ} , where M 1 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K M2 is at least one element selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. ≦ a ≦ 6, 0 ≦ b <2, 0 ≦ c <6, 0 ≦ d <6, and −0.5 ≦ δ ≦ 0.5 The secondary battery according to any one of claims 1 to 10 including at least one titanium-containing oxide selected from Ranaru group. An exterior member;
A plurality of electrode groups each including a negative electrode including the negative electrode active material-containing layer, a positive electrode including the positive electrode active material-containing layer, and the insulating layer;
The secondary battery according to claim 1, wherein the plurality of electrode groups are electrically connected in series and accommodated in the exterior member.   A battery pack comprising the secondary battery according to any one of claims 1 to 12. An external terminal for energization,
The battery pack according to claim 13, further comprising a protection circuit.   The battery pack according to claim 13 or 14, comprising a plurality of the secondary batteries, wherein the secondary batteries are electrically connected in series, parallel, or a combination of series and parallel.   A vehicle equipped with the battery pack according to any one of claims 13 to 15.   The vehicle according to claim 16, comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.