Electrode, secondary battery, battery pack, and vehicle

Abstract

To provide an electrode with excellent input / output performance, a secondary battery and a battery pack with excellent input / output performance, and a vehicle equipped with this battery pack.SOLUTION: An electrode according to an embodiment includes an active material-containing layer including an active material, inorganic solid particles having lithium ion conductivity, and a carbon material. The active material-containing layer exhibits a first peak indicating the maximum logarithmic differential pore volume in a logarithmic differential pore volume distribution curve obtained by mercury intrusion porosimetry. The pore diameter D1 of the first peak is 0.05 μm or more and 10 μm or less. The first pore volume corresponding to the first peak is 20% or more and 50% or less of the total pore volume in the active material-containing layer. The ratio of the second pore volume in the range of 0.005 μm or more and 0.02 μm or less to the first pore volume is 0.1% or more and 5% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to an electrode, a secondary battery, a battery pack, and a vehicle. [Background technology]

[0002] In recent years, secondary batteries such as lithium-ion secondary batteries and nonaqueous electrolyte secondary batteries have been developed as high-energy density batteries. Secondary batteries are expected to be used as power sources for vehicles such as hybrid electric vehicles and electric vehicles, or as power sources for large-scale electricity storage. When used as a power source for a vehicle, secondary batteries are required to achieve not only high energy density but also rapid charge / discharge performance and long-term reliability.

[0003] Rapid charging and discharging is possible when lithium ions and electrons move rapidly between a positive electrode and a negative electrode, which are capable of absorbing and releasing lithium ions and electrons, via an electrolyte and an external circuit, respectively. Such batteries capable of rapid charging and discharging have the advantage of significantly shortening charging times. Furthermore, using such batteries capable of rapid charging and discharging as a vehicle power source can improve the power performance of the vehicle and also enable efficient recovery of regenerative energy.

[0004] As a method for improving the input / output performance of secondary batteries, it has been reported that a polymer solid electrolyte is incorporated into the electrodes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-44216 [Patent Document 2] International Publication No. 2019 / 225387 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides an electrode with excellent input / output performance, a secondary battery and battery pack with excellent input / output performance, and a vehicle equipped with this battery pack. [Means for solving the problem]

[0007] According to an embodiment, an electrode is provided that includes an active material-containing layer that includes an active material, inorganic solid particles having lithium ion conductivity, and a carbon material. The active material contains one or more lithium-containing transition metal composite oxides, including lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese cobalt composite oxide, lithium manganese nickel composite oxide, lithium phosphate, and lithium nickel cobalt manganese composite oxide. The active material-containing layer exhibits a first peak indicating the maximum logarithmic differential pore volume in a logarithmic differential pore volume distribution curve measured by mercury intrusion porosimetry. The pore diameter D1 of the first peak is 0.05 μm or more and 10 μm or less. The first pore volume corresponding to the first peak is 20% or more and 50% or less of the total pore volume in the active material-containing layer. The ratio of the second pore volume having a diameter in the range of 0.005 μm or more and 0.02 μm or less to the first pore volume is 0.1% or more and 5% or less.

[0008] According to another embodiment, a secondary battery is provided that includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode , the electrodes according to the above embodiment.

[0009] According to yet another embodiment, there is provided a battery pack including the secondary battery according to the above embodiment.

[0010] According to yet another embodiment, a vehicle including the battery pack according to the above embodiment is provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view schematically showing an example of an electrode according to the embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view schematically illustrating an example of an electrode according to an embodiment. [Figure 3] FIG. 10 is an enlarged cross-sectional view schematically showing an example of a conventional electrode. [Figure 4] 4 is a graph showing the logarithmic differential pore volume distribution of an active material-containing layer of an example of an electrode according to an embodiment. [Figure 5] This is an enlarged graph of part S1 in Figure 4. [Figure 6] 10 is a graph showing the logarithmic differential pore volume distribution of the active material-containing layer of another example of the electrode according to the embodiment. [Figure 7] 7 is an enlarged graph of part S2 in FIG. 6. [Figure 8] 1 is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment. [Figure 9] FIG. 9 is an enlarged cross-sectional view of part A of the secondary battery shown in FIG. 8. [Figure 10] FIG. 10 is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 11] FIG. 11 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. [Figure 12] FIG. 1 is a perspective view schematically illustrating an example of a battery pack according to an embodiment. [Figure 13] FIG. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 14] FIG. 14 is a block diagram showing an example of an electrical circuit of the battery pack shown in FIG. [Figure 15] 1 is a partially see-through view schematically illustrating an example of a vehicle according to an embodiment. [Figure 16] 1 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0012] One method for improving the input / output performance of an electrode is to mix inorganic solid particles with lithium ion conductivity, such as solid electrolyte particles, into the active material-containing layer. Solid electrolyte particles have superior lithium ion conductivity compared to active materials. Adding solid electrolyte particles can reduce the lithium ion conduction resistance in the active material-containing layer. The effect of reducing lithium ion conduction resistance is more likely to be achieved when the specific surface area of ​​the solid electrolyte particles is high. On the other hand, when the solid electrolyte particles are made finer to increase the specific surface area, the solid electrolyte is more likely to aggregate, making it difficult to uniformly disperse it in the active material-containing layer.

[0013] The following describes embodiments with reference to the drawings. Note that common components throughout the embodiments are designated by the same reference numerals, and redundant explanations will be omitted. Each figure is a schematic diagram for explaining and facilitating understanding of the embodiments. While the shapes, dimensions, and ratios may differ from those of actual devices, these may be appropriately modified in design, taking into consideration the following explanation and known techniques.

[0014] [First embodiment] According to a first embodiment, an electrode is provided. The electrode includes an active material-containing layer containing an active material, inorganic solid particles having lithium ion conductivity, and a carbon material. A logarithmic differential pore volume distribution curve of the active material-containing layer obtained by mercury intrusion porosimetry includes a first peak indicating the maximum logarithmic differential pore volume. The pore diameter D1 corresponding to the peak top position of the first peak is in the range of 0.05 μm to 10 μm. Of the total pore volume of the active material-containing layer represented by the logarithmic differential pore volume distribution curve, the proportion of the first pore volume corresponding to the first peak is 20% to 50%. The ratio of the second pore volume in the range of 0.005 μm to 0.02 μm to the first pore volume is 0.1% to 5%.

[0015] Such an electrode may be, for example, a battery electrode. The battery in which the electrode is used may be, for example, a secondary battery such as a lithium secondary battery. The secondary battery referred to here includes a nonaqueous electrolyte secondary battery containing a nonaqueous electrolyte. As a specific example, the electrode may be a nonaqueous electrolyte battery electrode in which an active material-containing layer (electrode layer) is formed on a foil-shaped current collector (current collector foil). The electrode may be included in the battery as, for example, a positive electrode and / or a negative electrode.

[0016] The active material-containing layer contains an active material, inorganic solid particles having lithium ion conductivity, and a carbon material as a conductive agent. In addition to the active material, inorganic solid particles, and carbon material, the active material-containing layer may further contain, for example, another conductive agent and a binder.

[0017] The electrode according to the embodiment contains inorganic solid particles having lithium ion conductivity, thereby reducing the lithium ion conduction resistance of the active material-containing layer. Furthermore, the carbon material contained in the electrode reduces the increase in electronic conduction resistance due to the addition of inorganic solid particles. Furthermore, in an active material-containing layer in which the pore diameter D1 of the first peak is in the range of 0.05 μm to 10 μm, the first pore volume of the peak accounts for 20% to 50% (0.2 to 0.5) of the total pore volume of the active material-containing layer, and the ratio of the second pore volume, which is the sum of the pore volumes of pores having a pore diameter of 0.005 μm to 0.02 μm, to the first pore volume is 0.1% to 5% (0.001 to 0.05), the inorganic solid particles are well dispersed. Therefore, the lithium ion conduction resistance can be uniformly reduced throughout the active material-containing layer. Therefore, the use of the electrode according to the embodiment can improve the input / output performance of a secondary battery.

[0018] The electrode may further include a current collector. The active material-containing layer may be provided, for example, on at least one main surface of the current collector. The active material-containing layer may be provided on one main surface of the current collector. Alternatively, the active material-containing layer may be provided on both main surfaces of the current collector, for example, on both the front and rear surfaces of a foil-shaped current collector.

[0019] The current collector may include a portion on the surface of which no active material-containing layer is formed, and this portion can function as a current collecting tab.

[0020] A specific example of an electrode according to an embodiment is shown in Fig. 1. Fig. 1 is a cross-sectional view that schematically shows one example of an electrode according to an embodiment. In the example shown in Fig. 1, an embodiment of the electrode as a positive electrode of a battery is described. Fig. 1 is a schematic cross-sectional view that shows a cross section that intersects with the main surface of a positive electrode 5.

[0021] The positive electrode 5 shown in FIG. 1 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b provided on the positive electrode current collector 5a. The positive electrode current collector 5a includes a portion that does not support the positive electrode active material-containing layer 5b, i.e., a positive electrode current collector tab 5c. In the example shown, the positive electrode active material-containing layer 5b is supported on both the front and back main surfaces of the positive electrode current collector 5a. The positive electrode 5 may also be an electrode in which the positive electrode active material-containing layer 5b is supported on only one surface of the positive electrode current collector 5a.

[0022] Such an electrode is shown in more detail in Fig. 2. Fig. 2 is an enlarged cross-sectional view schematically illustrating an example of an electrode according to an embodiment. In the example shown in Fig. 2, an aspect as a positive electrode is described, similar to Fig. 1. Furthermore, Fig. 2 is a schematic cross-sectional view showing a part of a cross section intersecting with the main surface of the positive electrode 5, similar to Fig. 1. However, unlike Fig. 1, Fig. 2 shows an example in which an active material-containing layer is supported on only one surface of a current collector.

[0023] The positive electrode 5 shown in FIG. 2 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b provided on the positive electrode current collector 5a. In the illustrated example, the positive electrode active material-containing layer 5b is supported on one main surface of the positive electrode current collector 5a. The positive electrode active material-containing layer 5b contains active material particles 51, inorganic solid particles 52, and particulate carbon material 53. As illustrated in FIG. 2, the inorganic solid particles 52 in the positive electrode active material-containing layer 5b are dispersed as primary particles without agglomeration. The presence of the fine inorganic solid particles 52 uniformly dispersed in the form of primary particles in the positive electrode active material-containing layer 5b allows the large surface area to be effectively utilized for promoting lithium ion conduction. Therefore, the electrode according to this embodiment has excellent input / output performance.

[0024] For comparison, an example of a conventional electrode is shown in FIG. 3. FIG. 3 is an enlarged cross-sectional view schematically illustrating an example of a conventional electrode. FIG. 3 is a schematic cross-sectional view illustrating a portion of a cross section intersecting the main surface of the electrode. The conventional electrode 10 shown in FIG. 3 includes a current collector 10a and an active material-containing layer 10b provided on the current collector 10a. In the illustrated example, the active material-containing layer 10b is supported on one main surface of the current collector 10a. The active material-containing layer 10b contains active material particles 11, inorganic solid particles 12, and particulate carbon material 13. The inorganic solid particles 12 are contained in the active material-containing layer 10b as inorganic solid secondary particles 12A, which are aggregates of the inorganic solid particles 12. The surfaces of the inorganic solid particles 12 facing inward of the inorganic solid secondary particles 12A are not effectively utilized, and therefore, despite the addition of fine inorganic solid particles 12, an effect similar to that achieved by adding large inorganic solid particles is achieved.

[0025] Specific examples of logarithmic differential pore volume distribution curves obtained by mercury intrusion porosimetry for the active material-containing layer included in the electrode according to the embodiment are shown. Figures 4 and 6 are graphs showing the logarithmic differential pore volume distributions of the active material-containing layer of one example of the electrode according to the embodiment and another example. Figures 5 and 7 are graphs enlarging portions S1 in Figure 4 and S2 in Figure 6, respectively.

[0026] The logarithmic differential pore volume distribution curves shown in Figures 4 and 6 each have a peak top at a pore diameter D1 in the range of 0.05 μm to 10 μm (horizontal axis direction) and include a first peak P1 that indicates the maximum logarithmic differential pore volume (vertical axis direction) in the logarithmic differential pore volume distribution curve. The first pore volume corresponding to the first peak P1, i.e., the cumulative pore volume at the first peak P1, accounts for 20% to 50% of the total pore volume of the active material-containing layer measured by mercury intrusion porosimetry shown in the graph. The cumulative pore volume for a certain range of pore diameters (horizontal axis) corresponds to the integral of the logarithmic differential pore volume distribution (vertical axis) over that range, i.e., the area under the logarithmic differential pore volume distribution curve in the corresponding width along the horizontal axis of the graph.

[0027] Furthermore, the first pore volume does not correspond to the cumulative pore volume in the range of 0.05 μm or more and 10 μm or less, but corresponds to the cumulative pore volume in the range of pore diameters (horizontal axis) corresponding to the minimum values ​​of the logarithmic differential pore volume (vertical axis) before and after the peak top of the first peak P1. For example, in the example shown in Figure 4, the cumulative pore volume in the range of pore diameters from 0.07 μm to 0.4 μm corresponds to the first pore volume, and in the example shown in Figure 6, the cumulative pore volume in the range of pore diameters from 0.09 μm to 0.4 μm corresponds to the first pore volume.

[0028] In the illustrated example, the logarithmic differential pore volume distribution curve includes the second peak P2 within the pore diameter range of 0.005 μm to 0.02 μm (horizontal axis direction). The electrode according to the embodiment also includes an embodiment in which the second peak P2 does not fall within the above-mentioned range of the logarithmic differential pore volume distribution curve of the active material-containing layer. For example, the shoulder of the first peak may fall within the pore diameter range of 0.005 μm to 0.02 μm.

[0029] The cumulative pore volume (second pore volume) in the pore diameter range of 0.005 μm or more and 0.02 μm or less has a value of 0.1% or more and 5% or less in ratio to the first pore volume of the first peak P1 (0.001≦second pore volume / first pore volume≦0.05).

[0030] The first peak P1 mainly reflects pores formed between active material particles in the active material-containing layer, and the pore diameter range of 0.005 μm to 0.02 μm in the logarithmic differential pore volume distribution curve mainly reflects pores formed between inorganic solid particles that are not excessively aggregated.

[0031] As shown in the examples of Figures 4 and 5 and Figures 6 and 7, respectively, in an active material-containing layer in which the logarithmic differential pore volume distribution curve measured by mercury intrusion porosimetry includes the most intense peak (first peak P1) within the above-mentioned range, and the pore volume of that peak (first pore volume) and the pore volume of pores with a pore diameter of 0.005 μm to 0.02 μm (second pore volume) satisfy the above-mentioned conditions, the inorganic solid particles are uniformly dispersed within the layer without agglomeration. Therefore, an electrode equipped with such an active material-containing layer can exhibit excellent input / output performance. Furthermore, because there is little variation in the diffusion rate of lithium ions within the active material-containing layer, the entire active material-containing layer can participate evenly in charge / discharge reactions, making partial degradation unlikely.

[0032] The total pore volume of the active material-containing layer measured by mercury porosimetry is preferably 0.05 mL / g or more and 0.10 mL / g or less. An active material-containing layer having a total pore volume within this range has a high energy density and can retain a sufficient amount of electrolyte. The total pore volume is more preferably 0.06 mL / g or more and 0.08 mL / g or less.

[0033] The electrodes will be described in detail below.

[0034] The active material-containing layer may contain, as the active material, one type of compound alone, or may contain two or more types of compounds in combination.

[0035] The active material-containing layer contains, for example, an active material in the form of particles. The active material is preferably contained in the active material-containing layer in the form of primary particles. Solid electrolyte particles can be dispersed more easily in active material in the form of primary particles than in active material that has aggregated to form secondary particles. The active material particles preferably have an average primary particle diameter of 1 μm or more and 20 μm or less.

[0036] The inorganic solid particles are blended to enhance the lithium ion conductivity of the active material-containing layer. The inorganic solid particles preferably contain at least one compound selected from the group consisting of a first metal oxide containing at least one element selected from the group consisting of Ti, Ge, Sr, Zr, Sn, Al, Sc, Y, Ba, P, and Ca, a lanthanoid oxide, and a first sulfide containing at least one element selected from the group consisting of Li, Ge, P, Si, Sn, Al, Ga, B, and In. The lanthanoid oxide is an oxide containing a lanthanoid element such as La, Ce, Pr, or Nd. The first metal oxide may further contain a lanthanoid element such as La.

[0037] Examples of inorganic solid particles include oxide-based solid electrolytes and sulfide-based solid electrolytes. A lithium phosphate solid electrolyte having a NASICON structure and represented by the general formula LiMe2(PO4)3 is preferably used as the oxide-based solid electrolyte. In the general formula, Me is preferably at least one element selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), and aluminum (Al). The element Me more preferably contains any one of Ge, Zr, and Ti, and Al.

[0038] A specific example of a lithium phosphate solid electrolyte with a NASICON structure is LATP (Li 1+d+e Al d Ti 2-d Si e P 3-e O 12 ;0 <d≦2、0≦e<3)、Li 1+f+e Al f Ge 2-f Si e PO 3-e O 12 ;0≦f≦2, 0≦e<3, Li 1+f Al f Zr 2-f (PO4)3; 0≦f≦2, and Li 1+2g Ca g Zr 1-g(PO4)3;0≦g<1. 1+2g Ca g Zr 1-g (PO4)3 is preferably used as inorganic solid electrolyte particles because of its high water resistance, reducibility, and low cost.

[0039] In addition to the lithium phosphate solid electrolyte, other oxide-based solid electrolytes include Li h PO i N j and the amorphous LIPON compound (e.g., Li 2.9 PO 3.3 N 0.46 );Li with garnet structure 5+k X k La 3-k Mα2O 12 Li3Mβ is a compound represented by the formula: where X is at least one selected from the group consisting of Ca, Sr, and Ba, Mα is at least one selected from the group consisting of Nb and Ta, and 0≦k≦0.5; 2-k L2O 12 wherein Mγ is at least one selected from the group consisting of Ta and Nb, L may include Zr, and 0≦k≦0.5; Li 7-3k Al k La3Zr3O 12 and 0≦k≦0.5; and Li 5+f La3Mγ 2-f Zr f O 12 where Mγ is at least one selected from the group consisting of Nb and Ta, and 0≦f≦2. LLZ compounds (e.g., Li7La3Zr2O 12 ) are mentioned.

[0040] Alternatively, a sodium-containing solid electrolyte may be used as the solid electrolyte. The sodium-containing solid electrolyte has excellent ionic conductivity of sodium ions. Examples of the sodium-containing solid electrolyte include β-alumina, sodium phosphorus sulfide, and sodium phosphate. The sodium ion-containing solid electrolyte is preferably in the form of glass ceramics.

[0041] Inorganic solid particles are 1 x 10 at 25°C. -5 A solid electrolyte having a lithium ion conductivity of 1000 S / cm or more is preferred. The lithium ion conductivity can be measured, for example, by an AC impedance method. Specifically, inorganic solid particles are first molded using a tablet molding machine to obtain a green compact. Gold (Au) is vapor-deposited on both sides of this green compact to obtain a measurement sample. The AC impedance of the measurement sample is measured using an impedance measurement device. For example, a Solartron Frequency Response Analyzer Model 1260 is used as the measurement device. The measurement is performed at a measurement frequency of 5 Hz to 32 MHz, a measurement temperature of 25°C, and in an argon atmosphere.

[0042] A complex impedance plot is created based on the measured AC impedance. The complex impedance plot is plotted with the real component on the horizontal axis and the imaginary component on the vertical axis. The ionic conductivity σ of the inorganic solid particles is calculated using the following formula: Li In the following formula, Z Li is the resistance calculated from the diameter of the arc of the complex impedance plot, S is the area, and d is the thickness.

[0043]

number

[0044] The solid electrolyte is preferably a Lewis acid. Such a solid electrolyte is easily positively charged, and can capture anions in the electrolyte. This allows lithium ions, which are cations, to move more easily within the active material-containing layer. Examples of such solid electrolytes include the above-mentioned Li 1+2g Ca g Zr 1-g Examples include (PO4)3 and LATP.

[0045] The shape of the inorganic solid particles is not particularly limited, but may be, for example, spherical, elliptical, flat, or fibrous.

[0046] The inorganic solid particles preferably have an average primary particle size of 2 μm or less. If the inorganic solid particles have a small average primary particle size, the internal resistance of the battery tends to be low.

[0047] The inorganic solid particles preferably have an average primary particle size of 0.2 μm or more. If the inorganic solid particles have a large average primary particle size, aggregation of the particles tends to be suppressed.

[0048] Such an electrode contains a carbon material as a conductive agent. The conductive agent is blended to improve current collection performance and reduce contact resistance between the active material and the current collector. It is desirable to use at least a particulate carbon material as the carbon material. Examples of such particulate conductive agents include carbon black, such as acetylene black, and graphite. One of these may be used as the conductive agent, or two or more may be used in combination. Other conductive agents that can be used include, for example, fibrous carbon materials and flat or flake-shaped carbon materials. Examples of fibrous carbon materials include vapor-grown carbon fiber (VGCF), carbon nanofibers, and carbon nanotubes. Examples of flat or flake-shaped carbon materials include graphene. In addition to incorporating a conductive agent, the surfaces of the active material particles may be further coated with carbon or an electronically conductive inorganic material.

[0049] In the active material-containing layer, the amount of carbon material blended per 100 parts by mass of active material is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass. A large amount of carbon material can increase the electronic conductivity of the active material-containing layer. On the other hand, an excessively large amount of carbon material may decrease the energy density.

[0050] The binder is blended to fill gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0051] In the active material-containing layer, the amount of binder per 100 parts by mass of active material is preferably 0 to 10 parts by mass, more preferably 1 to 5 parts by mass. A large amount of binder ensures sufficient adhesion between the active material-containing layer and the current collector, resulting in excellent cycle performance. On the other hand, an excessively large amount of binder may result in a decrease in energy density.

[0052] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and extracted from the active material. For example, the current collector is preferably made of copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector with such a thickness can balance the strength and weight of the electrode.

[0053] The electrode according to the embodiment can be used as either a positive electrode or a negative electrode, and is preferably used as a positive electrode.

[0054] Next, the electrode according to the first embodiment will be described in detail with respect to both the negative electrode and the positive electrode.

[0055] (positive electrode) The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer can be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer can contain a positive electrode active material, inorganic solid particles, a carbon material, and optionally other conductive agents and binders. The positive electrode current collector and the positive electrode active material-containing layer can be the current collector and the active material-containing layer described above, respectively.

[0056] The positive electrode active material can include, for example, a lithium-containing transition metal composite oxide. The lithium-containing transition metal composite oxide preferably contains at least one transition metal selected from the group consisting of nickel, cobalt, and manganese. The lithium-containing transition metal composite oxide preferably further contains at least one element of titanium and aluminum in addition to these transition metals. The lithium-containing transition metal composite oxide is Li 1-v Ni 1-a-b Co a Mn b A c which can be represented by O2. A is at least one element selected from the group consisting of Al, Ti, Zr, Nb, Mg, Cr, V, Fe, Ta, Mo, Zn, Ca, Sn, Si, and P, v is 0 or more and 1 or less, a is 0 or more and 1 or less, b is 0 or more and 1 or less, the sum of a and b is 1 or less, and c is 0 or more and 1 or less.

[0057] Examples of the lithium-containing transition metal composite oxide include lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-yO2; where 0 < x ≤ 1, 0 < y < 1), a lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-w Ni w O4; where 0 < x ≤ 1, 0 < w < 2), a lithium phosphate having an olivine structure (e.g., Li x FePO4; where 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; where 0 < x ≤ 1, 0 < y < 1, Li x CoPO4; where 0 < x ≤ 1), and a lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0058] Alternatively, the positive electrode active material may contain other oxides and sulfides. Examples of the oxides and sulfides include compounds into which Li or Li ions can be inserted and desorbed. Examples of other oxides include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, and vanadium oxides (e.g., V2O5). Examples of other sulfides include iron sulfate (Fe2(SO4)3).

[0059] 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. A positive electrode active material having a specific surface area of 0.1 m 2 / g or more can sufficiently secure Li ion insertion and extraction sites. A 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.

[0060] The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0061] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0062] The density of the positive electrode active material-containing layer is 3.0 g / cm 3 More than 3.6g / cm 3 Preferably, it is 3.2 g / cm or less. 3 More than 3.5g / cm 3 More preferably, it is:

[0063] (Negative electrode) The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode active material-containing layer may include a negative electrode active material, inorganic solid particles, a carbon material, and optionally other conductive agents and binders. The negative electrode current collector and the negative electrode active material-containing layer may be the current collector and active material-containing layer described above, respectively.

[0064] As the negative electrode active material, for example, lithium titanate having a ramsdellite structure (e.g., Li 2+m Ti3O7, 0≦m≦3), lithium titanates with spinel structure (e.g., Li 4+m Ti5O 12 and m is 0≦m≦3), titanium dioxide (TiO2), anatase-type titanium dioxide, rutile-type titanium dioxide, niobium pentoxide (Nb2O5), hollandite-type titanium composite oxides, and lithium titanium oxides having a ramsdellite structure (e.g., Li 2+m Ti3O7, 0≦m≦3), orthorhombic titanium-containing composite oxide, and monoclinic niobium titanium composite oxide.

[0065] As an example of orthorhombic titanium-containing composite oxide, Li 2+n M1 2-r Ti 6-s M2 t O 14+σ Here, M1 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M2 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦n≦6, 0≦r<2, 0≦s<6, 0≦t<6, and −0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+n Na2Ti6O 14 (0≦n≦6).

[0066] As an example of the monoclinic niobium titanium composite oxide, Li u Ti 1-g M3 g Nb 2-r M4 r O 7+δ Here, M3 is at least one selected from the group consisting of Zr, Si, and Sn. M4 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦u≦5, 0≦g<1, 0≦r<2, and -0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium composite oxides include Li u Examples include Nb2TiO7 (0≦u≦5).

[0067] Another example of monoclinic niobium titanium composite oxide is Li u Ti 1-g M5 g+r Nb 2-r O 7-δ Here, M5 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦u≦5, 0≦g<1, 0≦r<2, and −0.3≦δ≦0.3.

[0068] The negative electrode current collector is preferably made of, for example, copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0069] The negative electrode current collector may also include a portion on the surface of which the negative electrode active material-containing layer is not formed, and this portion can function as a negative electrode current collecting tab.

[0070] The density of the negative electrode active material-containing layer (excluding the current collector) is 1.8 g / cm 3 More than 2.8g / cm 3 A negative electrode having a negative electrode active material-containing layer with a density within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is preferably 2.1 g / cm or less. 3 More than 2.6g / cm 3 More preferably, it is:

[0071] <Manufacturing method> Next, a method for manufacturing an electrode according to an embodiment will be described.

[0072] First, inorganic solid particles are dispersed in a solvent and stirred to prepare a first slurry. For example, N-methyl-2-pyrrolidone is used as the solvent. The solid content in the dispersion is adjusted to 10% or more and 70% or less. A bead mill is used as the stirrer. Specific examples of bead mill stirrers include the Star Mill LME4 bead mill manufactured by Ashizawa Finetech Co., Ltd. The stirring is carried out for 1 minute to 1 hour under the following conditions: a bead diameter of 0.1 mm to 5 mm, a bead filling rate of 40% to 90%, and a stirring speed of 300 rpm to 2000 rpm. It is more preferable to perform the stirring at a stirring speed of 700 rpm to 1500 rpm.

[0073] Next, the first slurry, active material, granular carbon, and optionally a binder and other carbon materials are mixed and stirred to prepare a second slurry. Here, a two-stage stirring process is performed: stirring using a planetary mixer followed by further stirring using a bead mill. In the first stage of stirring using the planetary mixer, the stirring speed is, for example, between 30 rpm and 6000 rpm, and the stirring time is between 10 minutes and 2 hours. In the second stage of stirring using the bead mill, the bead diameter is between 0.5 mm and 3 mm, the bead filling rate is between 40% and 90%, and the stirring speed is between 300 rpm and 2000 rpm, and the stirring time is between 3 minutes and 1 hour.

[0074] The second slurry is applied to one or both sides of a current collector, and the coating is dried, for example, at a temperature of 100°C to 120°C, to obtain a laminate of an active material-containing layer and a current collector. This laminate is then pressed to obtain an electrode. This method suppresses aggregation of the inorganic solid particles, ensuring that the inorganic solid particles are sufficiently dispersed among the active materials. This allows inorganic solid particles with a large specific surface area to be dispersed throughout the active material-containing layer, resulting in an electrode that exhibits excellent output performance.

[0075] <Measurement method> The measurement method for the electrode will be described below. Specifically, a method for obtaining a logarithmic differential pore volume distribution curve of the active material-containing layer by mercury porosimetry and a method for confirming the active material contained in the electrode will be described.

[0076] When measuring electrodes that are installed in a battery, remove the electrodes from the battery using the following procedure.

[0077] First, the battery is placed in a discharged state. Here, "discharged" refers to a state in which the battery is discharged to 0% charge. The discharged battery is placed in an inert atmosphere glove box, for example, a glove box filled with argon gas. Next, the target electrode is removed from the battery in the glove box. Specifically, the battery's exterior is cut open while paying careful attention not to short-circuit the positive and negative electrodes. From the battery, for example, if the electrode used as the positive electrode is to be used as the measurement sample, the electrode connected to the positive terminal is cut out. Alternatively, if the electrode used as the negative electrode is to be used as the measurement sample, the electrode connected to the negative terminal is cut out. The removed electrode is immersed in diethyl carbonate solvent, for example, for 3 minutes, and then dried in a glove box under an inert gas atmosphere.

[0078] (Method for obtaining logarithmic differential pore volume distribution curve) The logarithmic differential pore volume distribution curve of the active material-containing layer by mercury intrusion porosimetry can be obtained, for example, by the following method.

[0079] The electrode to be measured is cut to obtain multiple test pieces. The size of the test piece is, for example, a strip with a short side of 1.25 cm and a long side of 2.5 cm. The test piece is cut at a point including the center of an imaginary line parallel to the short side of the electrode. In this case, if the electrode is a wound type, the imaginary line parallel to the long side is further cut at a point that divides the number of test pieces equally. Furthermore, if the electrode is a stacked type, the center of the imaginary line parallel to the long side of the electrode is further cut for each stacked electrode to obtain the number of test pieces. If the number of electrodes is less than the intended number of test pieces, multiple pieces may be cut from one electrode.

[0080] Next, multiple test pieces are placed in the measurement cell of the measurement device, and mercury is allowed to penetrate into the pores of the test pieces. The number of test pieces is, for example, 16 to 32. For example, a 5 cc cell for large pieces with a stem volume of 0.4 cc is used as the measurement cell. For example, a Shimadzu Autopore 9520 (Autopore 9520 model manufactured by Shimadzu Corporation) is used as the measurement device. For example, the initial pressure is set to 7 kPa and the final pressure is set to 414 MPa during measurement. The measurement is performed at 1.1 of the initial pressure. n The pressure is measured at each pressure multiplied by 7 kPa, where n is a positive integer. That is, measurements are taken at pressures of, for example, 7 kPa, 7.7 kPa, 8.47 kPa, 9.317 kPa, 7 x 1.1 n The measurement is performed at 7 kPa (pounds per square inch absolute) until the pressure reaches 414 MPa. 7 kPa corresponds to 1.0 psia (pounds per square inch absolute), which corresponds to pores with a diameter of approximately 180 μm. 414 MPa corresponds to approximately 6 psia, which corresponds to pores with a diameter of approximately 0.003 μm. The mercury contact angle is set to 130 degrees, and the mercury surface tension is set to 485 dynes / cm. By processing the obtained data, the logarithmic differential pore volume distribution curve of the active material-containing layer, as well as the total pore volume and the pore volume for each pore size range, can be obtained.

[0081] (Method for identifying active materials and inorganic solid particles) The composition of the active material and inorganic solid particles contained in the active material-containing layer of an electrode can be confirmed by combining elemental analysis using a scanning electron microscope (SEM-EDX) equipped with an energy dispersive X-ray analyzer, X-ray diffraction (XRD) measurement, and inductively coupled plasma (ICP) optical emission spectroscopy. SEM-EDX analysis can determine the shape of the components contained in the active material-containing layer and the composition of the components contained in the active material-containing layer (each element from B to U in the periodic table). ICP measurement can quantify the elements in the active material-containing layer. Finally, XRD measurement can confirm the crystalline structure of the materials contained in the active material-containing layer.

[0082] A cross section of the electrode extracted in this manner is cut out using Ar ion milling. The cut cross section is observed using an SEM. Sample sampling is also carried out in an inert atmosphere such as argon or nitrogen, to prevent exposure to air. Several particles are selected from the 3000x SEM observation image. In this case, the particle size distribution of the selected particles is chosen to be as wide as possible.

[0083] Next, each of the selected particles is subjected to elemental analysis using EDX, which allows the type and amount of elements contained in each of the selected particles other than Li to be identified.

[0084] Regarding Li, information about the Li content in the entire active material-containing layer can be obtained by ICP optical emission spectroscopy. ICP optical emission spectroscopy is performed according to the following procedure.

[0085] A powder sample is prepared from the dried electrode as follows: The active material-containing layer is peeled off from the current collector and ground in a mortar. The ground sample is dissolved in acid to prepare a liquid sample. Acids that can be used in this process include hydrochloric acid, nitric acid, sulfuric acid, and hydrogen fluoride. This liquid sample is then subjected to ICP atomic emission spectroscopy to determine the concentrations of elements contained in the active material and inorganic solid particles being measured.

[0086] The crystal structure of the compound contained in each particle selected by SEM can be identified by XRD measurement. Identifying the crystal structure makes it possible to distinguish between composite oxides and electrode active materials. XRD measurement is performed using CuKα radiation as the radiation source in the measurement range of 2θ = 5° to 90°. This measurement allows the X-ray diffraction pattern of the compound contained in the selected particle to be obtained.

[0087] The XRD measurement device used was a SmartLab manufactured by Rigaku Co., Ltd. The measurement conditions were as follows: X-ray source: Cu target Output: 45kV, 200mA Soller slit: 5° for both incident and receiving light Step width (2θ): 0.02 deg Scan speed: 20deg / min Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm) Measurement range: 5°≦2θ≦90°.

[0088] When using other equipment, perform measurements using standard Si powder for powder X-ray diffraction to find conditions under which measurement results for peak intensity, half-width, and diffraction angle equivalent to those obtained with the above equipment are obtained, and then measure the sample under those conditions.

[0089] The conditions for XRD measurement should be such that an XRD pattern suitable for Rietveld analysis can be obtained. To collect data for Rietveld analysis, the step width should be set to 1 / 3-1 / 5 of the minimum half-width of the diffraction peak, and the measurement time or X-ray intensity should be adjusted appropriately so that the intensity at the peak position of the most intense reflection is 5000 cps or higher.

[0090] The XRD pattern obtained in this manner is analyzed by the Rietveld method, which calculates the diffraction pattern from a pre-estimated crystal structure model. The crystal structure model is estimated based on the results of EDX and ICP analysis. By fitting all of these calculated values ​​to the actual measured values, it is possible to precisely analyze the parameters related to the crystal structure (lattice constants, atomic coordinates, occupancy, etc.).

[0091] XRD measurements can be performed by directly attaching the electrode sample to the glass holder of a wide-angle X-ray diffractometer. To do this, first measure the XRD spectrum for each type of metal foil used in the electrode current collector to determine the position of the peaks originating from the current collector. The presence or absence of peaks from additives such as conductive agents and binders must also be determined. If the peaks from the current collector and the active material overlap, it is recommended to peel the active material-containing layer from the current collector before measurement. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. Of course, if these characteristics are known in advance, this step can be omitted.

[0092] (Method for measuring particle size) The average primary particle size of the primary particles of the active material and the average primary particle size of the inorganic solid particles can be obtained by observation with a transmission electron microscope (TEM).

[0093] The electrode used as a measurement sample is photographed using a TEM at a magnification of, for example, 50,000 times, so that the primary particles of the active material and inorganic solid particles are clearly visible. Next, for each of the active material and inorganic solid particles, primary particles that are visible in their entirety are selected from the primary particles captured in the TEM image. Next, these primary particles are approximated to ellipses. In this approximation, the ratio of the major and minor axes of the ellipse is set so that the difference between the outline of the primary particle and the outline of the circumference of the ellipse is minimized. Next, the lengths of the major and minor axes of the ellipse are measured. The arithmetic mean of the lengths of the major and minor axes of the ellipse obtained in this way is taken as the particle size of the primary particles. The same procedure is performed on 100 randomly selected particles, and the arithmetic mean of these measurements is taken as the average particle size of the primary particles.

[0094] The electrode according to the first embodiment includes an active material-containing layer containing an active material, inorganic solid particles having lithium ion conductivity, and a carbon material. A logarithmic differential pore volume distribution curve of the active material-containing layer measured by mercury intrusion porosimetry has a peak top at a pore diameter D1 in the range of 0.05 μm to 10 μm, and includes a first peak indicating the maximum logarithmic differential pore volume. The ratio of the first pore volume of the first peak to the total pore volume is 20% to 50%. The ratio of the second pore volume in the range of 0.005 μm to 0.02 μm to the first pore volume is 0.1% to 5%. The electrode exhibits excellent input / output performance.

[0095] [Second embodiment] According to a second embodiment, there is provided a secondary battery including a positive electrode, a negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is the electrode according to the first embodiment.

[0096] The secondary battery according to the second embodiment may further include a separator disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly.

[0097] The secondary battery according to the second embodiment may further include an exterior member that houses the electrode group and the electrolyte.

[0098] Furthermore, the secondary battery according to the second embodiment may further include a positive electrode terminal electrically connected to the positive electrode and a negative electrode terminal electrically connected to the negative electrode.

[0099] The secondary battery according to the second embodiment may be, for example, a lithium secondary battery, and includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0100] The positive electrode, negative electrode, electrolyte, separator, exterior member, positive electrode terminal, and negative electrode terminal will be described below.

[0101] 1) Positive electrode The positive electrode may be in the form of the positive electrode of the electrode according to the first embodiment, or in a battery including the electrode according to the first embodiment as a negative electrode, the positive electrode may be a positive electrode other than the electrode according to the first embodiment.

[0102] The other positive electrode may not contain solid electrolyte particles in the active material-containing layer (positive electrode active material-containing layer). Furthermore, in a logarithmic differential pore volume distribution curve of the active material-containing layer of the other positive electrode measured by mercury intrusion porosimetry, the peak top position of the most intense peak may be outside the range of 0.05 μm to 10 μm. Even if the most intense peak is located within the range of 0.05 μm to 10 μm, the proportion of the pore volume (first pore volume) corresponding to that peak may be less than 20% or more than 50% of the total. Alternatively, the ratio of the pore volume (second pore volume) in the range of 0.005 μm to 0.2 μm corresponding to the pore volume (first pore volume) of the most intense peak may be less than 0.1% or more than 5%. Other details of the other positive electrode are the same as those of the electrode according to the first embodiment.

[0103] Since the description overlaps with that in the first embodiment, detailed description will be omitted.

[0104] 2) Negative electrode The negative electrode may be in the form of the negative electrode of the electrode according to the first embodiment, or in a battery including the electrode according to the first embodiment as a positive electrode, the negative electrode may be a negative electrode other than the electrode according to the first embodiment.

[0105] The other negative electrode may not contain solid electrolyte particles in the active material-containing layer (negative electrode active material-containing layer). Furthermore, in a logarithmic differential pore volume distribution curve of the active material-containing layer of the other negative electrode measured by mercury intrusion porosimetry, the peak top position of the most intense peak may be outside the range of 0.05 μm to 10 μm. Even if the most intense peak is located within the range of 0.05 μm to 10 μm, the proportion of the pore volume (first pore volume) corresponding to that peak may be less than 20% or more than 50% of the total. Alternatively, the ratio of the pore volume (second pore volume) in the range of 0.005 μm to 0.2 μm corresponding to the pore volume (first pore volume) of the most intense peak may be less than 0.1% or more than 5%. Other details of the other negative electrode are the same as those of the electrode according to the first embodiment.

[0106] Since the description overlaps with that in the first embodiment, detailed description will be omitted.

[0107] 3) Electrolyte The electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous 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.

[0108] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoride (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), and lithium bistrifluoromethylsulfonylimide (LiN(CFSO)), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF is most preferred.

[0109] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or in combination.

[0110] The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0111] Alternatively, in addition to liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room temperature molten salts containing lithium ions (ionic melts), polymer solid electrolytes, inorganic solid electrolytes, and the like may be used as the nonaqueous electrolyte.

[0112] Room-temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room-temperature molten salts include room-temperature molten salts that exist as a liquid on their own, room-temperature molten salts that become liquid when mixed with an electrolyte salt, room-temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. Generally, the melting point of room-temperature molten salts used in secondary batteries is 25°C or lower. Furthermore, organic cations generally have a quaternary ammonium skeleton.

[0113] The solid polymer electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0114] The inorganic solid electrolyte is a solid material that has Li-ion conductivity.

[0115] 4) Separator The separator is formed from, for example, a porous film containing polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. Separators made of porous films coated with inorganic or organic compounds can also be used. From the viewpoint of safety, it is preferable to use porous films made from polyethylene or polypropylene. This is because these porous films melt at a certain temperature and are capable of interrupting current.

[0116] 5) Exterior materials The exterior member may be, for example, a container made of a laminate film or a metal container.

[0117] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0118] The laminate film is a multilayer film containing multiple resin layers and metal layers interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layers are preferably made of aluminum foil or aluminum alloy foil to reduce weight. The laminate film can be molded into the shape of the exterior component by sealing it by heat fusion.

[0119] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0120] 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 the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 100 ppm by mass or less. A battery equipped with such a metal container can dramatically improve long-term reliability and heat dissipation performance in high-temperature environments.

[0121] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin, button, sheet, laminated, or the like. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery. For example, the exterior member may be an exterior member for a small battery mounted in a portable electronic device or the like. Alternatively, the exterior member may be an exterior member for a large battery mounted in a vehicle such as a two-wheeled or four-wheeled automobile.

[0122] 6) Positive terminal The positive electrode terminal has a potential range of 3V to 4.5V relative to the redox potential of lithium (vs. Li / Li +) and can be formed from a material that is electrically stable and conductive. Examples of materials for the positive electrode terminal include aluminum and aluminum alloys 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 from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0123] 7) Negative terminal The negative electrode terminal has a potential range of 0.8V to 3V relative to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, 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 material for the negative electrode terminal is preferably aluminum or an aluminum alloy. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0124] Next, the secondary battery according to the second embodiment will be described in more detail with reference to the drawings.

[0125] Fig. 8 is a cross-sectional view schematically showing an example of a secondary battery according to Embodiment 2. Fig. 9 is an enlarged cross-sectional view of part A of the secondary battery shown in Fig. 8.

[0126] 8 and 9 includes a bag-shaped exterior member 2 shown in Fig. 8, an electrode group 1 shown in Fig. 8 and 9, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0127] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0128] As shown in Fig. 8, the electrode group 1 is a flat wound electrode group. As shown in Fig. 9, the flat wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0129] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the portion of the negative electrode 3 located at the outermost shell of the wound-type electrode group 1, the negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Fig. 9. In the other portions of the negative electrode 3, the negative electrode active material-containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0130] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides of the positive electrode current collector 5a.

[0131] As shown in FIG. 8, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral edge of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located at the outermost shell of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to a portion located at the outermost shell of the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend to the outside from an opening of the bag-shaped exterior member 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening is closed by heat sealing this.

[0132] The secondary battery according to the second embodiment is not limited to the secondary battery having the configuration shown in FIGS. 8 and 9, but may also be a battery having the configuration shown in FIGS. 10 and 11, for example.

[0133] Fig. 10 is a partially cutaway perspective view schematically showing another example of the secondary battery according to Embodiment 2. Fig. 11 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 10.

[0134] 10 and 11 includes an electrode group 1 shown in Fig. 10 and 11, an exterior member 2 shown in Fig. 10, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. The electrolyte is held in the electrode group 1.

[0135] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0136] The electrode group 1 is a laminated electrode group, as shown in Fig. 11. The laminated electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0137] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0138] The negative electrode current collector 3a of each negative electrode 3 includes a portion on one side where no negative electrode active material-containing layer 3b is supported on any surface. This portion serves as a negative electrode current collector tab 3c. As shown in FIG. 11 , the negative electrode current collector tab 3c does not overlap with the positive electrode 5. The multiple negative electrode current collector tabs 3c are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the exterior member 2.

[0139] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. Like the negative electrode current collector tab 3c, the positive electrode current collector tab does not overlap with the negative electrode 3. The positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 3c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2.

[0140] The secondary battery according to the second embodiment includes the electrode according to the first embodiment as at least one of the positive electrode and the negative electrode, and therefore has excellent input / output performance.

[0141] [Third embodiment] According to a third embodiment, there is provided a battery pack. The battery pack according to the third embodiment includes a plurality of secondary batteries according to the second embodiment.

[0142] In the battery pack according to the third embodiment, the cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0143] Next, an example of a battery pack according to a third embodiment will be described with reference to the drawings.

[0144] Fig. 12 is a perspective view schematically showing an example of a battery pack according to the third embodiment. The battery pack 200 shown in Fig. 12 includes five cells 100a to 100e, four bus bars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five cells 100a to 100e is a secondary battery according to the second embodiment.

[0145] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a to the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four bus bars 21. That is, the battery pack 200 in FIG. 12 is a five-series battery pack. Although an example is not shown, in a battery pack including a plurality of cells electrically connected in parallel, the plurality of cells can be electrically connected by, for example, connecting the negative electrode terminals to each other by a bus bar and connecting the positive electrode terminals to each other by a bus bar.

[0146] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to a positive electrode lead 22 for external connection. Also, the negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to a negative electrode lead 23 for external connection.

[0147] The battery pack according to the third embodiment includes the secondary battery according to the second embodiment, and therefore the battery pack has excellent input / output performance.

[0148] [Fourth embodiment] According to a fourth embodiment, a battery pack is provided. This battery pack includes the battery assembly according to the third embodiment. This battery pack may include a single secondary battery according to the second embodiment instead of the battery assembly according to the third embodiment.

[0149] The battery pack according to the fourth embodiment may further include a protection circuit. The protection circuit has a function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0150] The battery pack according to the fourth embodiment may further include external terminals for current flow. The external terminals for current flow are for outputting current from the secondary battery to the outside and / or inputting 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 terminals for current flow. When charging the battery pack, charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminals for current flow.

[0151] Next, an example of a battery pack according to a fourth embodiment will be described with reference to the drawings.

[0152] Fig. 13 is an exploded perspective view schematically showing an example of a battery pack according to the fourth embodiment, and Fig. 14 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 13.

[0153] The battery pack 300 shown in FIGS. 13 and 14 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0154] 13 is a bottomed, square container having a rectangular bottom. The container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31 to accommodate the battery pack 200 and other components. Although not shown, the container 31 and the lid 32 are provided with openings or connection terminals for connection to external devices and the like.

[0155] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0156] At least one of the plurality of cells 100 is a secondary battery according to the second embodiment. The plurality of cells 100 are electrically connected in series as shown in FIG. 14 . The plurality of cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0157] The adhesive tape 24 fastens the plurality of cells 100 together. Heat-shrinkable tape may be used to secure the plurality of cells 100 together instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both side surfaces of the battery pack 200, and the heat-shrinkable tape is wrapped around the cells 100, and the heat-shrinkable tape is then thermally shrunk to bind the plurality of cells 100 together.

[0158] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0159] The printed wiring board 34 is installed along one of the shorter sides of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wires 342a and 343a, an external terminal 350 for supplying current, a positive wire (positive wire) 348a, and a negative wire (negative wire) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0160] The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

[0161] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100 and transmits the detection signal to the protection circuit 346.

[0162] The external terminals 350 for applying current are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for applying current are electrically connected to devices located outside the battery pack 300. The external terminals 350 for applying current include a positive terminal 352 and a negative terminal 353.

[0163] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via a wiring 343a. The protection circuit 346 is also electrically connected to each of the plurality of single cells 100 via wiring 35.

[0164] The protective sheet 33 is disposed on both inner surfaces of the long sides of the container 31 and on the inner surface of the short side that faces the printed wiring board 34 across the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0165] The protection circuit 346 controls charging and discharging of the plurality of cells 100. Furthermore, the protection circuit 346 cuts off the electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from each cell 100 or the battery pack 200.

[0166] An example of the detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal indicating that overcharge, overdischarge, or overcurrent of the cell 100 is detected. When detecting overcharge or the like for each 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 cell 100.

[0167] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0168] As described above, the battery pack 300 is also provided with the external terminals 350 for current application. Therefore, the battery pack 300 can output current from the battery assembly 200 to an external device and input current from the external device to the battery assembly 200 via the external terminals 350 for current application. In other words, when the battery pack 300 is used as a power source, the current from the battery assembly 200 is supplied to the external device via the external terminals 350 for current application. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 via the external terminals 350 for current application. When the battery pack 300 is used as an in-vehicle battery, regenerative energy from the vehicle's power can be used as the charging current from the external device.

[0169] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as the positive and negative terminals of the external terminals for supplying current, respectively.

[0170] Such a battery pack is used in applications requiring excellent cycle performance when drawing a large current, for example. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an on-board battery.

[0171] The battery pack according to the fourth embodiment includes the secondary battery according to the second embodiment or the battery pack according to the third embodiment, and therefore has excellent input / output performance.

[0172] [Fifth embodiment] According to a fifth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fourth embodiment.

[0173] In the vehicle according to the fifth embodiment, the battery pack recovers, for example, regenerative energy for powering the vehicle. The vehicle may include a mechanism (regenerator) for converting the kinetic energy of the vehicle into regenerative energy.

[0174] Examples of the vehicle according to the fifth embodiment include two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, power-assisted bicycles, and railcars.

[0175] The mounting position of the battery pack in the vehicle according to the fifth embodiment is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0176] The vehicle according to the fifth embodiment may be equipped with a plurality of battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, in parallel, or in a combination of series and parallel connections. For example, if each battery pack includes a battery assembly, the battery assembly may be electrically connected in series, in parallel, or in a combination of series and parallel connections. Alternatively, if each battery pack includes a single battery, the batteries may be electrically connected in series, in parallel, or in a combination of series and parallel connections.

[0177] Next, an example of a vehicle according to a fifth embodiment will be described with reference to the drawings.

[0178] FIG. 15 is a partial perspective view schematically illustrating an example of a vehicle according to the fifth embodiment.

[0179] A vehicle 400 shown in Fig. 15 includes a vehicle body 40 and a battery pack 300 according to the third embodiment. In the example shown in Fig. 15, the vehicle 400 is a four-wheeled automobile.

[0180] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (for example, single cells or assembled batteries) included in the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0181] 15 illustrates an example in which the battery pack 300 is mounted in an engine compartment located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, at the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for powering the vehicle 400.

[0182] Next, with reference to FIG. 16, an embodiment of a vehicle according to the fifth embodiment will be described.

[0183] Fig. 16 is a diagram that schematically shows an example of a control system related to an electrical system in a vehicle according to Embodiment 5. A vehicle 400 shown in Fig. 16 is an electric vehicle.

[0184] The vehicle 400 shown in Figure 16 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0185] Vehicle 400 has vehicle power supply 41 mounted, for example, in the engine compartment, the rear of the vehicle body, or under the seat. Note that in vehicle 400 shown in Fig. 16, the mounting location of vehicle power supply 41 is shown schematically.

[0186] 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.

[0187] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). 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 300a to 300c are the same as the battery pack 300 described above, and the assembled batteries 200a to 200c are the same as the assembled battery 200 described above. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can each be removed independently and replaced with another battery pack 300.

[0188] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the second embodiment. Each of the assembled batteries 200a to 200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0189] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c and collects information on the voltage, temperature, etc. of each of the cells 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0190] The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0191] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each of the cells constituting the battery packs 200a to 200c based on commands received through communication from the battery management device 411. However, the temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all the cells.

[0192] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 16) that switches between electrical connection and disconnection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a-200c are being charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is being supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0193] 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 is controlled based on control signals from the battery management unit 411 or the vehicle ECU 42, which controls the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0194] The drive motor 45 is rotated by the electric power supplied from the inverter 44. The drive force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0195] Although not shown, the vehicle 400 also includes a regenerative braking mechanism. The regenerative braking mechanism (for example, a regenerator) rotates the drive motor 45 when the vehicle 400 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into direct current. The converted direct current is input to the vehicle power supply 41.

[0196] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to a negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided on the connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0197] One terminal of a connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive input terminal 418 of the inverter 44. A switch device 415 is provided on the connection line L2 between the positive terminal 413 and the positive input terminal 418.

[0198] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to, for example, an external power source.

[0199] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, thereby managing the entire vehicle 400. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0200] The vehicle according to the fifth embodiment is equipped with the battery pack according to the fourth embodiment, and therefore has a battery pack with excellent input / output performance, and can therefore exhibit high performance.

[0201] [Example] Examples will be described below, but the present invention is not limited to the examples listed below as long as they do not depart from the gist of the present invention.

[0202] <Electrode fabrication> Example 1 First, inorganic solid particles were mixed with N-methyl-2-pyrrolidone to a solid content of 60%, and dispersed using a bead mill (Star Mill LME4) manufactured by Ashizawa Finetech Co., Ltd. to prepare a first slurry. The first slurry was prepared under the following dispersion conditions: bead diameter Φ0.1 mm, bead filling rate 60%, and stirring speed 700 rpm. The inorganic solid particles had an average particle size of 0.5 μm and a lithium ion conductivity of 1×10 -4 Li in S / cm 1.5 Al 0.5 Ti 1.5 (PO4)3 was used. Hereinafter, these inorganic solid particles will be referred to as LATPO1.

[0203] The active material, granular carbon, and binder were mixed with the first slurry, and the mixture was stirred using a planetary mixer. The mixture was then further stirred in a bead mill to prepare a second slurry. The second slurry was prepared under the following dispersion conditions: a bead diameter of 2 mm, a bead filling rate of 60%, and a stirring speed of 1000 rpm. The active material was a lithium-containing nickel-manganese-cobalt composite oxide (LiNi) with an average particle size of 6.4 μm. 0.5 Mn 0.2 Co 0.3 O2 particles were used. Acetylene black with an average particle size of 0.2 μm was used as the granular carbon. Polyvinylidene fluoride was used as the binder. In the second slurry, the amounts of inorganic solid particles, granular carbon, and binder per 100 parts by mass of active material were 3 parts by mass, 3 parts by mass, and 2 parts by mass, respectively.

[0204] Next, the second slurry was applied to both sides of the current collector, and the coating was dried to obtain an active material-containing layer. The current collector was an aluminum alloy foil with a thickness of 12 μm. The current collector and the active material-containing layer were pressed to obtain an electrode. The density of the active material-containing layer was 3.3 g / cm. 3 It was.

[0205] (Example 2-3) In Examples 2 and 3, electrodes were produced in the same manner as in Example 1, except that the conditions for the stirring treatment using a bead mill when preparing the second slurry were changed as shown in Table 1 below.

[0206] (Examples 4-7) In Examples 4-7, instead of LATPO1, inorganic solid particles were used, and the average particle size was 0.7 μm and the lithium ion conductivity was 1×10 -4 Li in S / cm 1.5 Al 0.5 Ti 1.5 (PO4)3 was used. Hereinafter, these inorganic solid particles will be referred to as LATPO2. In Examples 4-7, electrodes were produced in the same manner as in Example 1, except that LATPO2 was used instead of LATPO1 and the conditions for bead mill dispersion in preparing the first slurry were changed as shown in Table 1 below.

[0207] (Comparative Example 1-2) In Comparative Example 1-2, an electrode was prepared using the same procedure as in Example 1, except that the conditions for bead mill dispersion when preparing the first slurry or the conditions for stirring using a bead mill when preparing the second slurry were changed as shown in Table 1 below.

[0208] Table 1 below summarizes the electrode fabrication conditions for each example and comparative example. Specifically, it shows the average particle size of LATPO1 and LATPO2 used as inorganic solid particles before bead mill treatment, the bead mill dispersion conditions in preparing the first slurry, and the bead mill stirring conditions in preparing the second slurry. The bead mill treatment conditions for preparing the first and second slurries include the bead diameter, bead packing ratio, and stirring speed.

[0209] [Table 1]

[0210] <Measurement of logarithmic differential pore volume distribution curve> Using the method described above, the logarithmic differential pore volume distribution curves of the active material-containing layers of the electrodes prepared in Examples 1-7 and Comparative Examples 1-2 were measured by mercury intrusion porosimetry. For the active material-containing layers of all electrodes, the highest peak (first peak) of log differential intrusion appeared in the range of 0.05 μm to 10 μm. From the obtained logarithmic differential pore volume distribution curves, the first pore volume corresponding to the highest peak (first peak) and the second pore volume in the range of 0.005 μm to 0.02 μm were determined, and the ratio of the first pore volume to the total pore volume and the ratio of the second pore volume to the first pore volume were calculated, respectively. The obtained results are shown in Table 2 below.

[0211] <Input / output performance evaluation> A two-electrode coin cell was fabricated, and the input / output performance (rate performance) was evaluated. The electrodes fabricated in Examples 1-7 and Comparative Examples 1-2 were used as the working electrodes. The electrodes were circular with a diameter of 14 mm. Lithium metal was used as the counter electrode. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in which lithium hexafluorophosphate (LiPF6) was dissolved. The ratio of ethylene carbonate to diethyl carbonate in the mixed solvent was 1:2. The concentration of LiPF6 was 1 mol / L. The amount of electrolyte was 200 μL.

[0212] First, the fabricated coin cell was charged at a current density of 1C in an environment of 25°C until the state of charge (SOC) reached 100%. It was then discharged at a current density of 1C until the SOC reached 0%, and the 1C discharge capacity was measured. It was then charged again at a current density of 1C until the SOC reached 100%. It was then discharged at a current density of 3C until the SOC reached 0%, and the 3C discharge capacity was measured. The 3C / 1C rate capacity ratio was calculated by dividing the discharge capacity at 3C by the discharge capacity at 1C. The results are shown in Table 2.

[0213] [Table 2]

[0214] Table 2 shows that the electrodes prepared in Examples 1-7 had better input / output performance than the electrodes prepared in Comparative Examples 1-2. In the electrodes prepared in Examples 1-7, the first peak, whose peak top was the maximum logarithmic differential pore volume in a logarithmic differential pore volume distribution curve measured by mercury intrusion porosimetry, had a first pore volume with a ratio of 20% to 50% of the total pore volume, and the ratio of the second pore volume with a particle size of 0.005 μm to 0.02 μm to the first pore volume was 0.1% to 5%. In contrast, in both Comparative Examples 1 and 2, the ratio of the second pore volume to the first pore volume was 0%. In addition, in the electrode prepared in Comparative Example 2, the first pore volume also exceeded 50% of the total pore volume.

[0215] In Comparative Example 1, the stirring speed was low during the bead mill dispersion in the preparation of the first slurry, causing the inorganic solid particles (LATPO1) to aggregate in the first slurry. In other words, the inorganic solid particles could not be uniformly dispersed, resulting in poor input / output performance of the electrode.

[0216] In Comparative Example 2, the stirring speed during the bead mill stirring process for preparing the second slurry was low, causing the inorganic solid particles (LATPO1) to aggregate in the second slurry. Furthermore, the proportion of the first pore volume derived from the active material was high, which indicates that the active material, inorganic solid particles, and carbon material could not be well mixed. As a result, the input / output performance of the electrode was poor.

[0217] According to at least one of the embodiments and examples described above, an electrode including an active material-containing layer is provided. The active material-containing layer includes an active material, inorganic solid particles having lithium ion conductivity, and a carbon material. The active material-containing layer exhibits a first peak indicating the maximum logarithmic differential pore volume in a logarithmic differential pore volume distribution curve obtained by mercury intrusion porosimetry. The pore diameter D1 of the first peak is 0.05 μm or more and 10 μm or less, and the first pore volume corresponding to the first peak is 20% or more and 50% or less of the total pore volume. The second pore volume in the range of 0.005 μm or more and 0.02 μm or less is 0.1% or more and 5% or less of the first pore volume. The electrode has excellent input / output performance, and it is possible to provide a secondary battery and a battery pack having excellent input / output performance, as well as a vehicle equipped with this battery pack.

[0218] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. The inventions described in the original claims of this application are set forth below. [1] A battery comprising an active material-containing layer including an active material, inorganic solid particles having lithium ion conductivity, and a carbon material; The active material-containing layer exhibits a first peak indicating a maximum logarithmic differential pore volume in a logarithmic differential pore volume distribution curve obtained by mercury intrusion porosimetry, and the pore diameter D 1 is 0.05 μm or more and 10 μm or less, a first pore volume corresponding to the first peak is 20% or more and 50% or less of a total pore volume in the active material-containing layer, and a ratio of a second pore volume having a size in the range of 0.005 μm or more and 0.02 μm or less to the first pore volume is 0.1% or more and 5% or less. [2] The electrode according to [1], wherein the active material contains particles having an average primary particle size of 1 μm or more and 20 μm or less, and the inorganic solid particles have an average primary particle size of 0.2 μm or more and 2 μm or less. [3] The electrode according to [1] or [2], wherein the active material contains a lithium-containing transition metal composite oxide. [4] a positive electrode; a negative electrode; Electrolytes and A secondary battery comprising: A secondary battery, wherein at least one of the positive electrode and the negative electrode is the electrode according to any one of [1] to [3]. [5] A battery pack comprising the secondary battery according to [4]. [6] An external terminal for applying current; Protection circuit and The battery pack according to [5], further comprising: [7] A battery comprising a plurality of the secondary batteries, The battery pack according to [5] or [6], wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. [8] A vehicle equipped with a battery pack according to any one of [5] to [7]. [9] The vehicle according to [8], including a mechanism for converting the kinetic energy of the vehicle into regenerative energy. [Explanation of symbols]

[0219] 1...electrode group, 2...exterior member, 3...negative electrode, 3a...negative electrode current collector, 3b...negative electrode active material-containing layer, 3c...negative electrode current collector tab, 4...separator, 5...positive electrode, 5a...positive electrode current collector, 5b...positive electrode active material-containing layer, 5c...positive electrode current collector tab, 6...negative electrode terminal, 7...positive electrode terminal, 10...electrode, 10a...current collector, 10b...active material-containing layer, 11...active material particles, 12...inorganic solid particles, 12A...inorganic solid secondary particles, 13...carbon material, 21 ...bus bar, 22...positive electrode side lead, 22a...other end, 23...negative electrode side lead, 23a...other end, 24...adhesive tape, 31...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power supply, 42...electrical control device, 43...external terminal, 44...inverter, 45...drive motor, 51...active material particles, 52...inorganic solid particles, 53...carbon material, 100...two secondary battery, 200... battery pack, 200a... battery pack, 200b... battery pack, 200c... 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, 342... positive electrode side connector, 343... negative electrode side connector, 345... thermistor, 346... protection circuit, 342a... wiring, 34 3a...wiring, 350...external terminal for current supply, 352...positive terminal, 353...negative terminal, 348a...positive wiring, 348b...negative wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive terminal, 414...negative terminal, 415...switch device, 416...current detection unit, 417...negative input terminal, 418...positive input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. The battery includes an active material-containing layer that includes an active material, inorganic solid particles having lithium ion conductivity, and a carbon material, the active material contains one or more kinds of lithium-containing transition metal composite oxides, and the lithium-containing transition metal composite oxides include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese cobalt composite oxide, lithium manganese nickel composite oxide, lithium phosphate, and lithium nickel cobalt manganese composite oxide; The active material-containing layer exhibits a first peak indicating a maximum logarithmic differential pore volume in a logarithmic differential pore volume distribution curve obtained by mercury intrusion porosimetry, and the pore diameter D １ is 0.05 μm or more and 10 μm or less, a first pore volume corresponding to the first peak is 20% or more and 50% or less of a total pore volume in the active material-containing layer, and a ratio of a volume of second pores having a size in the range of 0.005 μm or more and 0.02 μm or less to the volume of the first pores is 0.1% or more and 5% or less.

2. 2. The electrode according to claim 1, wherein the active material contains particles having an average primary particle diameter of 1 μm or more and 20 μm or less, the inorganic solid particles have an average primary particle diameter of 0.2 μm or more and 2 μm or less, the particle diameters of the primary particles of the active material and the primary particles of the inorganic solid particles are each an arithmetic mean value of lengths of major axes and minor axes of ellipses that approximate the primary particles as observed with a transmission electron microscope, and the average primary particle diameter is the arithmetic mean value of the particle diameters.

3. A positive electrode and a negative electrode; Electrolytes and A secondary battery comprising: The secondary battery, wherein the positive electrode is the electrode according to claim 1 or 2.

4. A battery pack comprising the secondary battery according to claim 3.

5. An external terminal for applying current; Protection circuit and The battery pack according to claim 4, further comprising:

6. A battery includes a plurality of the secondary batteries, 6. The battery pack according to claim 4, wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

7. A vehicle comprising the battery pack according to any one of claims 4 to 6.

8. 8. The vehicle according to claim 7, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

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