Non-aqueous electrolyte storage element, storage device, method of using the same, and method of manufacturing the same

Abstract

A nonaqueous electrolyte power storage element according to one aspect comprises a positive electrode having positive electrode active material particles. The positive electrode active material particles include a lithium transition metal composite oxide having an α-NaFeO2 structure. The lithium transition metal composite oxide contains nickel and / or cobalt, and manganese, and the molar ratio of the content of the lithium with respect to the content of the transition metal in the lithium transition metal composite oxide exceeds 1.0. The lithium transition metal composite oxide demonstrates, in a diagram of X-ray diffraction analysis in which CuKα rays were used, a diffraction peak within the range of 20° to 22°. The positive electrode active material particles contain aluminum.

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte storage element, a storage device, a method for using them, and a method for manufacturing them.

Background Art

[0002] Non-aqueous electrolyte storage elements typified by lithium secondary batteries have been increasingly used in recent years, and the development of various cathode active materials has been demanded. Conventionally, as a cathode active material for non-aqueous electrolyte storage elements, a lithium transition metal composite oxide having an α-NaFeO2-type crystal structure has been studied, and a non-aqueous electrolyte secondary battery using LiCoO2 has been widely put into practical use. As a transition metal (Me) constituting the lithium transition metal composite oxide, manganese, which is abundant as a global resource, is used, and a non-aqueous electrolyte secondary battery using a so-called LiMeO2-type active material in which the molar ratio of lithium to the transition metal (Li / Me) constituting the lithium transition metal composite oxide is approximately 1 has also been put into practical use.

[0003] On the other hand, in recent years, among lithium transition metal composite oxides having an α-NaFeO2-type crystal structure, so-called lithium-excess type active materials in which the molar ratio of lithium to the transition metal (Li / Me) exceeds 1 have been developed (Patent Documents 1 and 2). Non-aqueous electrolyte storage elements using such lithium-excess type active materials have attracted attention because they have a larger discharge capacity than LiMeO2-type active materials.

[0004] In a conventional non-aqueous electrolyte storage element using a lithium-excess type active material for the cathode, in order to exhibit the above-described effects, the cathode potential generally reaches 4.5 V vs. Li / Li + through initial charge and discharge up to the above. In Patent Document 1, during the initial charge and discharge of a non-aqueous electrolyte secondary battery using a lithium-excess type active material for the cathode and silicon and carbon for the anode, the cathode potential is 4.60 V vs. Li / Li +Charging is performed until it reaches [a certain state]. In Patent Document 2, during the initial charge and discharge of a non-aqueous electrolyte secondary battery using a lithium-excess type active material for the positive electrode and graphite for the negative electrode, until the voltage reaches 4.7V, that is, until the positive electrode potential reaches 4.8V vs. Li / Li + Charging is performed until it reaches [a certain state].

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a non-aqueous electrolyte energy storage element, it is desirable that the internal resistance does not increase even when the charge and discharge cycles are repeated. However, conventional non-aqueous electrolyte energy storage elements using a lithium-excess type active material for the positive electrode also have a problem that the internal resistance tends to increase with the charge and discharge cycles.

[0007] An object of the present invention is to provide a non-aqueous electrolyte energy storage element using a lithium-excess type active material for the positive electrode, in which an increase in internal resistance associated with charge and discharge cycles is suppressed, as well as an energy storage device, a method of using such a non-aqueous electrolyte energy storage element and an energy storage device, and a manufacturing method thereof.

Means for Solving the Problems

[0008] The non-aqueous electrolyte storage element according to one aspect of the present invention includes a positive electrode having positive electrode active material particles. The positive electrode active material particles contain a lithium transition metal composite oxide having an α-NaFeO2 structure. The lithium transition metal composite oxide contains at least one of nickel and cobalt and manganese. The content of lithium with respect to the transition metal in the lithium transition metal composite oxide exceeds 1.0 in molar ratio. In the X-ray diffraction pattern using the CuKα ray of the lithium transition metal composite oxide, a diffraction peak exists in the range of 20° or more and 22° or less. The positive electrode active material particles contain aluminum, and it is a non-aqueous electrolyte storage element.

[0009] Another aspect of the present invention is a power storage device including two or more non-aqueous electrolyte storage elements and one or more of the non-aqueous electrolyte storage elements according to another aspect of the present invention.

[0010] The method of using the non-aqueous electrolyte storage element according to another aspect of the present invention includes charging in a range where the positive electrode potential is less than 4.5V vs.Li / Li + It is a method of using the non-aqueous electrolyte storage element according to one aspect of the present invention.

[0011] The method of using the power storage device according to another aspect of the present invention includes charging one or more of the non-aqueous electrolyte storage elements in a range where the positive electrode potential is less than 4.5V vs.Li / Li + It is a method of using the power storage device according to one aspect of the present invention.

[0012] The method of manufacturing the non-aqueous electrolyte storage element according to another aspect of the present invention includes performing initial charge and discharge in a range where the positive electrode potential is less than 4.5V vs.Li / Li + It is a method of manufacturing the non-aqueous electrolyte storage element according to one aspect of the present invention.

[0013] The method of manufacturing the power storage device according to another aspect of the present invention includes performing initial charge and discharge on one or more of the non-aqueous electrolyte storage elements in a range where the positive electrode potential is less than 4.5V vs.Li / Li + It is a method of manufacturing the power storage device according to one aspect of the present invention.

Advantages of the Invention

[0014] According to one aspect of the present invention, there is provided a non-aqueous electrolyte storage element using a lithium-excess type active material for a positive electrode, the non-aqueous electrolyte storage element in which an increase in internal resistance associated with charge and discharge cycles is suppressed, as well as a power storage device, a method for using such a non-aqueous electrolyte storage element and a power storage device, and a manufacturing method thereof.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0016] First, an overview of the non-aqueous electrolyte storage element, the power storage device, the method for using them, and the manufacturing method thereof disclosed in this specification will be described.

[0017] The non-aqueous electrolyte storage element according to one aspect of the present invention includes a positive electrode having positive electrode active material particles, the positive electrode active material particles containing a lithium transition metal composite oxide having an α-NaFeO2 structure, the lithium transition metal composite oxide including at least one of nickel and cobalt and manganese, the content of lithium with respect to the transition metal in the lithium transition metal composite oxide exceeding 1.0 in molar ratio, and there being a diffraction peak in the range of 20° or more and 22° or less in an X-ray diffraction pattern using the CuKα line of the lithium transition metal composite oxide, and the positive electrode active material particles containing aluminum.

[0018] A non-aqueous electrolyte energy storage device according to one aspect of the present invention is a non-aqueous electrolyte energy storage device using a lithium-excess type active material as a positive electrode, and an increase in internal resistance associated with charge-discharge cycles is suppressed. Although the reason for such an effect is not clear, the following is speculated. The lithium transition metal composite oxide provided in the positive electrode of the non-aqueous electrolyte energy storage device is a lithium transition metal composite oxide in which a diffraction peak exists in the range of diffraction angle 2θ of 20° or more and 22° or less in an X-ray diffraction pattern. In the X-ray diffraction pattern of the synthesized lithium-excess type active material (lithium transition metal composite oxide having an α-NaFeO2 structure and a lithium content relative to the transition metal exceeding 1.0 in molar ratio) before charge and discharge, there is a diffraction peak in the range of 20° or more and 22° or less that appears in the monoclinic crystal of the Li[Li 1 / 3 Mn 2 / 3 O2 type. In a conventional non-aqueous electrolyte energy storage device using a lithium-excess type active material, in order to activate the lithium-excess type active material, initial charge and discharge up to a positive electrode potential of 4.5 V vs. Li / Li + or higher is performed (hereinafter, "charging up to a positive electrode potential of 4.5 V vs. Li / Li + or higher to activate the lithium-excess type active material" is also referred to as high-potential formation). The diffraction peak in the range of 20° or more and 22° or less disappears due to a change in the symmetry of the crystal accompanying lithium desorption in the crystal when charging up to a positive electrode potential of 4.5 V vs. Li / Li + or higher is performed. That is, the presence of a diffraction peak in the range of 20° or more and 22° or less means that the positive electrode potential is 4.5 V vs. Li / Li +This means that charging (high potential formation) up to the above level has not been performed. In the case of a lithium-excess type active material that has been subjected to conventional high potential formation, it is considered that one of the factors contributing to the increase in internal resistance with the charge-discharge cycle is that a change in the crystal structure occurs in the direction of decreasing the solid-phase diffusion rate of lithium ions. On the other hand, the lithium-excess type active material (lithium transition metal composite oxide) provided in the non-aqueous electrolyte storage element has not been subjected to high potential formation. Therefore, in the lithium-excess type active material provided in the non-aqueous electrolyte storage element, it is considered that a change in the crystal structure in the direction of decreasing the solid-phase diffusion rate of lithium ions is unlikely to occur, and this is presumed to be one of the factors suppressing the increase in internal resistance associated with the charge-discharge cycle in the non-aqueous electrolyte storage element. Also, in the case of a lithium transition metal composite oxide containing manganese, it is considered that one of the factors contributing to the increase in internal resistance is that manganese elutes with the charge-discharge cycle. On the other hand, in the non-aqueous electrolyte storage element, it is presumed that the elution of manganese is suppressed because the positive electrode active material particles contain aluminum, and as a result, the increase in internal resistance is suppressed. Thus, according to the non-aqueous electrolyte storage element, it is presumed that the increase in internal resistance associated with the charge-discharge cycle is suppressed by the combination of the presence of a diffraction peak in the range of 20° or more and 22° or less in the X-ray diffraction pattern using the CuKα line of the lithium transition metal composite oxide and the fact that the positive electrode active material particles contain aluminum. Also, the non-aqueous electrolyte storage element according to one aspect of the present invention can have a high capacity retention rate after the charge-discharge cycle. In the non-aqueous electrolyte storage element that has not been subjected to high potential formation, it is presumed that by repeating the charge-discharge during use, the lithium-excess type active material is gradually activated, and the lithium ions desorbing from the lithium-excess type active material during charge-discharge gradually increase (hereinafter, "the gradual activation of the lithium-excess type active material with the repetition of charge-discharge during use, etc." is also referred to as time-dependent formation). Therefore, according to the non-aqueous electrolyte storage element, the capacity retention rate after the charge-discharge cycle is also high because it is presumed that the consumption of lithium ions by the negative electrode in the charge-discharge cycle is compensated by the replenishment from the lithium-excess type active material of the positive electrode.

[0019] Note that the composition ratio of the lithium transition metal composite oxide in this specification refers to the composition ratio when in a fully discharged state, which is determined by the following method. First, charge the non-aqueous electrolyte storage element at a constant current of 0.05C until the charging cut-off voltage during normal use is reached to make it in a fully charged state. After a 30-minute rest, discharge it at a constant current of 0.05C until the lower limit voltage during normal use is reached. Disassemble it, take out the positive electrode, assemble a test cell with a metal lithium electrode as the counter electrode, and perform a constant current discharge at a current value of 10 mA per 1 g of the positive electrode mixture until the positive electrode potential reaches 2.0 V vs. Li / Li + and adjust the positive electrode to a fully discharged state. Disassemble it again and take out the positive electrode. Using dimethyl carbonate, thoroughly wash the non-aqueous electrolyte adhering to the taken-out positive electrode, dry it at room temperature for one day and night, and then collect the lithium transition metal composite oxide of the positive electrode active material. Subject the collected lithium transition metal composite oxide to measurement. The operations from the disassembly of the non-aqueous electrolyte storage element to the measurement are carried out in an argon atmosphere with a dew point of -60°C or lower. Here, "during normal use" refers to the case where the non-aqueous electrolyte storage element is used by adopting the charge-discharge conditions recommended or specified for the non-aqueous electrolyte storage element. When a charger for the non-aqueous electrolyte storage element is prepared, it refers to the case where the non-aqueous electrolyte storage element is used by applying that charger.

[0020] Also, the X-ray diffraction measurement for the lithium transition metal composite oxide is performed on the lithium transition metal composite oxide that has been made in a fully discharged state by the above method. Specifically, the X-ray diffraction measurement is carried out by powder X-ray diffraction measurement using an X-ray diffractometer ("MiniFlex II" manufactured by Rigaku), with the X-ray source being CuKα rays, the tube voltage being 30 kV, and the tube current being 15 mA. At this time, the diffracted X-rays pass through a Kβ filter with a thickness of 30 μm and are detected by a high-speed one-dimensional detector (D / teX Ultra 2). Also, the sampling width is 0.02°, the scan speed is 5° / min, the divergence slit width is 0.625°, the receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm.

[0021] The peak differential pore volume of the above positive electrode active material particles is 0.5 mm3 It is preferably below / (g·nm). By using the positive electrode active material particles with a peak differential pore volume of 0.5 mm 3 / (g·nm) or less, the increase in internal resistance associated with charge-discharge cycles is more suppressed.

[0022] The peak differential pore volume of the positive electrode active material particles shall be the value obtained by the BJH method from the adsorption isotherm using the nitrogen gas adsorption method. Specifically, the peak differential pore volume is measured by the following method. 1.00 g of the powder of the sample to be measured (positive electrode active material particles) is placed in a sample tube for measurement and vacuum-dried at 120 °C for 12 hours to sufficiently remove the moisture in the measurement sample. Next, by the nitrogen gas adsorption method using liquid nitrogen, the isotherms on the adsorption side and the desorption side are measured within the range where the relative pressure P / P0 (P0 = about 770 mmHg) is from 0 to 1. Then, the pore distribution is evaluated by calculating using the desorption-side isotherm by the BJH method, and the peak differential pore volume is obtained.

[0023] The content of manganese relative to the transition metal in the above lithium transition metal composite oxide is preferably 0.3 or more and 0.65 or less in terms of molar ratio. Conventionally, when a lithium transition metal composite oxide containing such a relatively high content of manganese is used, an increase in internal resistance due to the elution of manganese is particularly likely to occur. In contrast, according to the non-aqueous electrolyte storage element according to one aspect of the present invention, even when a lithium transition metal composite oxide containing manganese with a content within the above range is used, the increase in internal resistance associated with charge-discharge cycles is sufficiently suppressed. Further, by using a lithium transition metal composite oxide containing manganese with a content within the above range, the capacity retention rate after charge-discharge cycles can be increased.

[0024] It is preferable that at least a part of the above aluminum is present in a particulate form on the surface of the above positive electrode active material particles. When aluminum is thus dispersed and present on the surface of the positive electrode active material particles, an increase in internal resistance associated with charge-discharge cycles is sufficiently suppressed. Further, the positive electrode active material particles in which aluminum is distributed in this manner can be efficiently produced by firing a mixture containing a positive electrode active material precursor, a lithium compound, and an aluminum compound, and are also excellent in productivity.

[0025] In the non-aqueous electrolyte storage element according to one aspect of the present invention, the positive electrode potential at the end-of-charge voltage during normal use is 4.5 V vs. Li / Li + and preferably less. When the positive electrode potential at the end-of-charge voltage during normal use is less than 4.5 V vs. Li / Li + a change in crystal structure in the direction of decreasing the solid-phase diffusion rate of lithium ions is suppressed, so that an increase in internal resistance associated with charge-discharge cycles is more sufficiently suppressed. Further, when the positive electrode potential at the end-of-charge voltage during normal use is less than 4.5 V vs. Li / Li + aging progresses gradually with repeated charge-discharge many times, so that the capacity retention rate can be further increased.

[0026] A method of using a non-aqueous electrolyte storage element according to another aspect of the present invention comprises charging in a range where the positive electrode potential is less than 4.5 V vs. Li / Li + and is a method of using a non-aqueous electrolyte storage element according to one aspect of the present invention.

[0027] According to the method of use, an increase in internal resistance associated with charge-discharge cycles of a non-aqueous electrolyte storage element using a lithium-excess type active material for the positive electrode is suppressed. Further, according to the method of use, the non-aqueous electrolyte storage element can be repeatedly used with a high capacity retention rate.

[0028] A method for manufacturing a non-aqueous electrolyte storage element according to another aspect of the present invention comprises performing initial charge-discharge in a range where the positive electrode potential is less than 4.5 V vs. Li / Li + and is a method for manufacturing a non-aqueous electrolyte storage element according to one aspect of the present invention.

[0029] According to the manufacturing method, a non-aqueous electrolyte storage element using a lithium-excess type active material for the positive electrode, in which an increase in internal resistance associated with charge-discharge cycles is suppressed, can be manufactured. Further, according to the manufacturing method, a non-aqueous electrolyte storage element having a high capacity retention rate in charge-discharge cycles can be manufactured.

[0030] Another aspect of the present invention is a power storage device including two or more non-aqueous electrolyte storage elements and one or more of the non-aqueous electrolyte storage elements according to another aspect of the present invention.

[0031] A power storage device according to one aspect of the present invention is a power storage device including one or more non-aqueous electrolyte storage elements using a lithium-excess type active material for the positive electrode, in which an increase in internal resistance associated with charge-discharge cycles is suppressed.

[0032] A method of using a power storage device according to another aspect of the present invention includes charging one or more of the non-aqueous electrolyte storage elements within a range where the positive electrode potential is less than 4.5 V vs. Li / Li + This is a method of using a power storage device according to one aspect of the present invention.

[0033] According to the method of use, an increase in internal resistance associated with charge-discharge cycles of a power storage device including one or more non-aqueous electrolyte storage elements using a lithium-excess type active material for the positive electrode is suppressed. Further, according to the method of use, the power storage device can be repeatedly used with a high capacity retention rate.

[0034] A method of manufacturing a power storage device according to another aspect of the present invention includes performing initial charge and discharge on one or more of the non-aqueous electrolyte storage elements within a range where the positive electrode potential is less than 4.5 V vs. Li / Li + This is a method of manufacturing a power storage device according to one aspect of the present invention.

[0035] According to the manufacturing method, it is possible to manufacture a power storage device including one or more non-aqueous electrolyte power storage elements using a lithium-excess type active material for the positive electrode, and having a suppressed increase in internal resistance associated with charge-discharge cycles. Further, according to the manufacturing method, it is possible to manufacture a power storage device having a high capacity retention rate in charge-discharge cycles.

[0036] Hereinafter, a non-aqueous electrolyte power storage element, a method of using the same, and a method of manufacturing the same according to an embodiment of the present invention will be described in detail.

[0037] <Non-aqueous electrolyte power storage element> The non-aqueous electrolyte power storage element according to an embodiment of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode and the negative electrode usually form an electrode body that is alternately stacked or wound through a separator. This electrode body is housed in a container, and the container is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. As the container, known metal containers, resin containers, etc. that are usually used can be used. Hereinafter, as an example of the non-aqueous electrolyte power storage element, a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as "secondary battery") will be described.

[0038] (Positive electrode) The positive electrode has a positive electrode substrate and a positive electrode active material layer disposed directly or via an intermediate layer on the positive electrode substrate.

[0039] The positive electrode substrate has conductivity. Having "conductivity" means that the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 7 Ω·cm or less, and "non-conductive" means that the above volume resistivity is 10 7It means being more than Ω·cm. As the material of the positive electrode substrate, metals such as aluminum, titanium, tantalum, stainless steel, or alloys thereof are used. Among these, aluminum or an aluminum alloy is preferable from the viewpoints of corrosion resistance, high conductivity, and cost. Examples of the positive electrode substrate include a foil and a vapor deposition film, and a foil is preferable from the viewpoint of cost. Therefore, an aluminum foil or an aluminum alloy foil is preferable as the positive electrode substrate. Examples of aluminum or an aluminum alloy include A1085, A3003, etc. defined in JIS-H-4000 (2014).

[0040] The average thickness of the positive electrode substrate is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less. By setting the average thickness of the positive electrode substrate to be not less than the above lower limit, the strength of the positive electrode substrate can be increased. By setting the average thickness of the positive electrode substrate to be not more than the above upper limit, the energy density per volume of the secondary battery can be increased. The "average thickness" refers to a value obtained by dividing the punching mass when punching out a substrate of a predetermined area by the true density and the punching area of the substrate. The same definition applies when using "average thickness" for other members, etc.

[0041] The intermediate layer is a layer disposed between the positive electrode substrate and the positive electrode active material layer. The configuration of the intermediate layer is not particularly limited. For example, it contains a resin binder and conductive particles. The intermediate layer reduces the contact resistance between the positive electrode substrate and the positive electrode active material layer by containing conductive particles such as carbon particles, for example.

[0042] The positive electrode active material layer is a layer of a positive electrode mixture containing positive electrode active material particles. The positive electrode active material layer (positive electrode mixture) may contain optional components such as a conductive agent, a binder, a thickener, and a filler, in addition to the positive electrode active material particles, as required.

[0043] (Positive electrode active material particles) The positive electrode active material particles include a lithium transition metal composite oxide having an α-NaFeO2 structure. The above positive electrode active material particles contain aluminum. Aluminum may be contained in the positive electrode active material particles as a component constituting the lithium transition metal composite oxide, or may be contained in the positive electrode active material particles as a component different from the lithium transition metal composite oxide.

[0044] The molar ratio (Li / Me) of the content of lithium (Li) to the transition metal (Me) in the lithium transition metal composite oxide exceeds 1.0. This lithium transition metal composite oxide is a so-called lithium-excess type active material. Further, in the X-ray diffraction pattern using the CuKα ray of the lithium transition metal composite oxide, a diffraction peak exists in the range where the diffraction angle 2θ is 20° or more and 22° or less.

[0045] The transition metal (Me) contained in the lithium transition metal composite oxide includes at least one of nickel (Ni) and cobalt (Co) and manganese (Mn). This transition metal preferably consists essentially of Ni and Mn, or preferably consists essentially of Ni, Mn, and Co. The lithium transition metal composite oxide may be represented by Li 1+α (Ni β Co γ Mn δ ) 1-α O2 (0 < α < 1, 0 ≤ β < 1, 0 ≤ γ < 1, 0 < δ < 1, β + γ + δ = 1, β + γ ≠ 0).

[0046] The content of lithium (Li) with respect to the transition metal (Me) in the lithium transition metal composite oxide, that is, (1 + α) / (1 - α), is preferably 1.05 or more and 1.5 or less, more preferably 1.1 or more and 1.4 or less, and even more preferably 1.2 or more and 1.35 or less in some cases. By setting (1 + α) / (1 - α) within the above range, the performance as a lithium-excess type active material such as a large discharge capacity is sufficiently exhibited, and the increase in the internal resistance of the secondary battery (non-aqueous electrolyte storage element) accompanying the charge-discharge cycle is further suppressed. Note that the content (content ratio) of each element in the lithium transition metal composite oxide is an atomic ratio and is equal to the molar ratio.

[0047] The content of Ni (Ni / Me) with respect to the transition metal (Me) in the above lithium transition metal composite oxide, that is, β may be, for example, 0.1 or more and 0.8 or less, preferably 0.2 or more and 0.7 or less, and more preferably 0.3 or more and 0.6 or less. By setting Ni / Me to be equal to or higher than the above lower limit, output performance, energy density, etc. can be enhanced. By setting Ni / Me to be equal to or lower than the above upper limit, the capacity retention rate, etc. can be enhanced.

[0048] The content of Co (Co / Me) with respect to the transition metal (Me) in the above lithium transition metal composite oxide, that is, γ may be, for example, 0 or more and 0.6 or less, and may also be 0.1 or more and 0.3 or less. By setting Co / Me to be equal to or higher than the above lower limit, output performance, energy density, etc. can be enhanced. On the other hand, by setting Co / Me to be equal to or lower than the above upper limit, while exhibiting a sufficient capacity retention rate, the raw material cost can be suppressed, etc.

[0049] The molar ratio of Mn (Mn / Me) with respect to the transition metal (Me) in the above lithium transition metal composite oxide, that is, δ may be, for example, 0.1 or more and 0.8 or less, and preferably 0.3 or more and 0.65 or less. By setting Mn / Me to be equal to or higher than the above lower limit, the effect of aging over time is enhanced, and the capacity retention rate can be enhanced. By setting Mn / Me to be equal to or lower than the above upper limit, elution of Mn can be suppressed, and an increase in the internal resistance of the secondary battery accompanying charge and discharge cycles can also be more suppressed, and output performance, etc. can also be enhanced.

[0050] The above lithium transition metal composite oxide may contain other transition metals, etc. within the range where the effects of the present invention are achieved, and other transition metals, etc. may be mixed as impurities. Further, the above lithium transition metal composite oxide may contain aluminum as described above. Examples of the lithium transition metal composite oxide containing aluminum include, for example, Li 1+α (Ni β Co γ Mn δ Al ε ) 1-αIt may be represented by O2 (0 < α < 1, 0 ≤ β < 1, 0 ≤ γ < 1, 0 < δ < 1, 0 < ε < 0.2, β + γ + δ + ε = 1, β + γ ≠ 0).

[0051] The positive electrode active material particles may contain other positive electrode active materials other than the above lithium transition metal composite oxide. As the other positive electrode active materials, they can be appropriately selected from known positive electrode active materials commonly used in lithium ion secondary batteries and the like. As the above other positive electrode active materials, materials that can usually occlude and release lithium ions are generally used. For example, the above-mentioned LiMeO2 type active materials, lithium transition metal oxides having a spinel type crystal structure, polyanion compounds, chalcogen compounds, sulfur, etc. may be mentioned. However, the content of the above lithium transition metal composite oxide (lithium-excess type active material) in all the positive electrode active materials contained in the positive electrode active material particles is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 99% by mass or more, and even more preferably 100% by mass.

[0052] Aluminum is preferably present on at least the surface of the positive electrode active material particles. For example, when the positive electrode active material particles are secondary particles, it is preferable that aluminum is present at least on the surface of these secondary particles. However, aluminum may be present between the primary particles of the positive electrode active material particles. Aluminum may be dissolved in the positive electrode active material.

[0053] Aluminum may be present so as to cover the entire surface of the positive electrode active material particles, or may be present in a particulate state on the surface of the positive electrode active material particles. However, from the viewpoints of productivity, suppression of increase in internal resistance, etc., at least a part of aluminum is preferably present in a particulate state on the surface of the positive electrode active material particles, that is, at least a part of aluminum is preferably dispersed and present in a particulate state on the surface of the positive electrode active material particles. At this time, the particles containing aluminum may be bonded to each other. Further, apart from the aluminum present on the surface of the positive electrode active material particles, aluminum may be present in a portion other than the surface of the positive electrode active material particles, that is, inside the positive electrode active material particles. A positive electrode active material such as a lithium transition metal composite oxide containing aluminum is used, and this aluminum may be present on the particle surface.

[0054] In one embodiment of the present invention, aluminum is present on the surface of the positive electrode active material particles in a compound state, more preferably in a state of particles of a compound. Examples of the aluminum compound include oxides, sulfides, halides, silicates, phosphates, sulfates, nitrates, alloys, etc. Among these, it is preferable that aluminum is present as an oxide (such as Al2O3, LiAlO2).

[0055] The content of aluminum in the positive electrode active material particles may be, for example, 0.01 mol% or more and 5 mol% or less with respect to the transition metal in the lithium transition metal composite oxide, but 0.1 mol% or more and 2.5 mol% or less is preferable, and 0.3 mol% or more and 1.5 mol% or less is more preferable. By setting the content of aluminum to be equal to or higher than the above lower limit, the effect of suppressing the elution of manganese due to the presence of aluminum in the positive electrode active material particles is enhanced, and the increase in the internal resistance of the secondary battery accompanying charge and discharge cycles can be more suppressed. On the other hand, by setting the content of aluminum to be equal to or lower than the above upper limit, the amount of the positive electrode active material relatively increases, so that the energy density etc. can be increased.

[0056] Here, the content of aluminum in the positive electrode active material particles is taken as the value measured by ICP (Inductively Coupled Plasma) emission spectrometry.

[0057] The peak differential pore volume of the positive electrode active material particles is not particularly limited, and is 0.01 mm 3 / (g·nm) or more and 2 mm 3 / (g·nm) or less, but may be 0.02 mm 3 / (g·nm) or more and 0.5 mm 3 / (g·nm) or less is preferable, and 0.3 mm 3 / (g·nm) or less is more preferable. When the peak differential pore volume is relatively small in this way, a lithium transition metal composite oxide with relatively high density can be obtained, and the energy density of the secondary battery can be increased. In addition, by using positive electrode active material particles whose peak differential pore volume is below the above upper limit, an increase in internal resistance associated with charge-discharge cycles is more suppressed. Positive electrode active material particles having a peak differential pore volume of, for example, 0.5 mm 3 / (g·nm) or less can be obtained, for example, by using a hydroxide precursor described later as a positive electrode active material precursor.

[0058] The average particle size of the positive electrode active material particles is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material particles to be at least the above lower limit, the production or handling of the positive electrode active material particles becomes easy. By setting the average particle size of the positive electrode active material particles to be at most the above upper limit, the electron conductivity of the positive electrode active material layer is improved. Here, the "average particle size" means a value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) based on the particle size distribution measured by the laser diffraction / scattering method for a dilution of the particles diluted with a solvent conforms to JIS-Z-8825 (2013).

[0059] The content of the positive electrode active material particles in the positive electrode active material layer (positive electrode mixture) is preferably 70% by mass or more and 98% by mass or less, more preferably 80% by mass or more and 97% by mass or less, and even more preferably 90% by mass or more and 96% by mass or less. By setting the content of the positive electrode active material particles within the above range, the electric capacity of the secondary battery can be increased.

[0060] (Method for manufacturing positive electrode active material particles) The positive electrode active material particles containing aluminum can be prepared by the following methods: (1) adding particulate positive electrode active material to a solution in which an aluminum compound (a compound containing aluminum) is dissolved or suspended, and then drying; (2) adding particulate positive electrode active material to a solution in which an aluminum compound is dissolved or suspended, and then reacting by heating or the like; (3) firing a mixture containing a positive electrode active material precursor, a lithium compound, and an aluminum compound; (4) firing a mixture containing an aluminum compound and particulate positive electrode active material; (5) firing a mixture containing a positive electrode active material precursor containing aluminum and a lithium compound, etc. Among these, the method of firing a mixture containing a positive electrode active material precursor, a lithium compound, and an aluminum compound is preferred. By manufacturing the positive electrode active material particles by such a method, it is possible to efficiently obtain the positive electrode active material particles in which at least a part of aluminum or an aluminum compound is present in a particulate state on the surface. In these positive electrode active material particles, for example, aluminum may be present between primary particles, a part of aluminum may be solid-solved, or particulate aluminums may be bonded to each other. In the case of the method using a solution in which an aluminum compound is dissolved or suspended as in the above (1) and (2), usually, a coating layer containing an aluminum compound is formed on the surface of the particulate positive electrode active material, and it is difficult to obtain positive electrode active material particles in which particulate aluminum or an aluminum compound is present on the surface. Hereinafter, the manufacturing method of the positive electrode active material particles according to the above method (3) will be described in detail.

[0061] Lithium transition metal composite oxides can usually be obtained by preparing a raw material containing metal elements (such as Li, Ni, Mn, etc.) according to the composition of the desired lithium transition metal composite oxide and firing it. In producing a lithium transition metal composite oxide having a desired composition, a so-called "solid phase method" in which salts of Li, Ni, Mn, etc. are mixed and fired, or a coprecipitation precursor in which Ni, Mn, etc. are present in one particle in advance is prepared, and a Li salt is mixed with this and fired, a "coprecipitation method" is known. Among these methods, the coprecipitation method, in which it is easy to obtain a target product in which each element is distributed with high uniformity, is preferred. Hereinafter, the coprecipitation method will be described.

[0062] As precursors (cathode active material precursors) obtained by the coprecipitation method, generally, hydroxide precursors and carbonate precursors are mentioned. Among them, the method for producing a hydroxide precursor is preferable because cathode active material particles with a small peak differential pore volume and sufficient suppression of the increase in internal resistance associated with charge-discharge cycles can be obtained.

[0063] When producing a hydroxide precursor, it is preferable to add an alkaline solution containing an alkali metal hydroxide (neutralizing agent), a complexing agent, and a reducing agent to water (aqueous solution) in a reaction vessel maintained at alkalinity together with a solution containing a transition metal (Me) to coprecipitate a transition metal hydroxide which is a hydroxide precursor. As the complexing agent, ammonia, ammonium sulfate, ammonium nitrate, etc. can be used. As the reducing agent, hydrazine, sodium borohydride, etc. can be used. As the alkali metal hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide, etc. can be used.

[0064] When producing a carbonate precursor, it is preferable to add an alkaline solution containing a neutralizing agent such as sodium carbonate or lithium carbonate and a complexing agent to water (aqueous solution) in a reaction vessel maintained at alkalinity together with a solution containing a transition metal (Me) to coprecipitate a transition metal carbonate which is a carbonate precursor.

[0065] Regarding the raw materials of the precursor, examples of the Ni compound include nickel hydroxide, nickel carbonate, nickel sulfate, nickel nitrate, nickel acetate, etc. Examples of the Co compound include cobalt sulfate, cobalt nitrate, cobalt acetate, etc. Examples of the Mn compound include manganese oxide, manganese carbonate, manganese sulfate, manganese nitrate, manganese acetate, etc.

[0066] In preparing the precursor, Mn is easily oxidized, so it is not easy to prepare a precursor in which Ni, Co and Mn are uniformly distributed in a divalent state, and the uniform mixing of Ni, Co and Mn at the atomic level is likely to be insufficient. Therefore, in order to suppress the oxidation of Mn present in the precursor, it is preferable to remove the dissolved oxygen in the water or solution. As a method for removing the dissolved oxygen, a method of bubbling with a gas that does not contain oxygen can be mentioned. Examples of the gas that does not contain oxygen include, but are not limited to, nitrogen gas, argon gas, carbon dioxide gas, and the like.

[0067] When preparing a precursor by coprecipitating a compound containing a transition metal in a solution, the pH of the solution, the dripping speed of the raw aqueous solution, etc. are not particularly limited, and conditions similar to those of conventionally known manufacturing conditions can be adopted. The pH of the solution can be, for example, 8 to 11, and may be 9.5 to 10.5. The dripping speed of the raw aqueous solution can be, for example, 0.1 cm 3 / min or more 10cm 3 / min or less.

[0068] When a complexing agent such as NH3 is present in the reaction vessel and certain convection conditions are applied, continuing stirring after the end of the drop of the raw solution promotes the rotation of the particles and their revolution in the stirring vessel, during which the particles collide with each other and grow stepwise into concentric spheres. In other words, the coprecipitation precursor is formed through a two-step reaction: a metal complex formation reaction when the raw solution is dropped into the reaction vessel, and a precipitation formation reaction that occurs while the metal complex is retained in the reaction vessel.

[0069] The preferred duration of stirring after completion of dropwise addition of the raw material aqueous solution, i.e., the reaction time, is influenced by the size of the reaction vessel, stirring conditions, pH, reaction temperature, etc., but is preferably, for example, from 0.5 hours to 20 hours, and more preferably from 1 hour to 15 hours.

[0070] By mixing the precursor (cathode active material precursor) obtained by the above method, a Li compound, and an aluminum compound and firing them, cathode active material particles are obtained. As the Li compound, lithium hydroxide, lithium carbonate, etc. can be used. Further, together with these Li compounds, LiF, Li2SO4, or Li3PO4 can be used as a sintering aid. The addition ratio of these sintering aids is preferably 1 to 10 mol% with respect to the total amount of the Li compound. Note that it is preferable to charge the total amount of the Li compound about 1 to 5 mol% in excess in anticipation of a part of the Li compound disappearing during firing. Examples of the aluminum compound include oxides, sulfides, halides, silicates, phosphates, sulfates, nitrates, alloys, etc., and oxides are preferable.

[0071] The firing temperature is preferably 750°C or higher and 1,000°C or lower. By setting the firing temperature to be equal to or higher than the above lower limit, cathode active material particles with a high degree of sintering can be obtained, and the charge-discharge cycle performance can be improved. On the other hand, by setting the firing temperature to be equal to or lower than the above upper limit, it is possible to suppress a decrease in discharge performance due to, for example, a structural change from the layered α-NaFeO2 structure to the rock salt-type cubic structure.

[0072] In order to obtain particles such as cathode active material particles in a predetermined shape, a crusher, a classifier, etc. are used. Examples of the crushing method include methods using a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve, etc. Wet crushing in which water or an organic solvent such as hexane coexists can also be used during crushing. As the classification method, a sieve, an air classifier, etc. are used as needed for both dry and wet processes.

[0073] (Components other than cathode active material particles) The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such conductive agents include graphite; carbon blacks such as furnace black and acetylene black; metals; and conductive ceramics. Examples of the shape of the conductive agent include powder form and fibrous form. Among these, acetylene black is preferred from the viewpoints of electron conductivity and coatability.

[0074] As for the content of the conductive agent in the positive electrode active material layer (positive electrode mixture), 1% by mass or more and 10% by mass or less is preferable, and 2% by mass or more and 5% by mass or less is more preferable. By setting the content of the conductive agent within the above range, the electric capacity of the secondary battery can be increased.

[0075] Examples of the binder include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0076] As for the content of the binder in the positive electrode active material layer (positive electrode mixture), 1% by mass or more and 10% by mass or less is preferable, and 2% by mass or more and 5% by mass or less is more preferable. By setting the content of the binder within the above range, the active material can be stably held.

[0077] Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, this functional group may be deactivated in advance by methylation or the like.

[0078] The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and aluminosilicate.

[0079] The positive electrode active material layer may contain, as components other than the positive electrode active material particles, conductive agent, binder, thickener, and filler, typical non-metal elements such as B, N, P, F, Cl, Br, I, etc., typical metal elements such as Li, Na, Mg, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, etc., and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W, etc.

[0080] (Negative electrode) The negative electrode has a negative electrode substrate and a negative electrode active material layer disposed directly or via an intermediate layer on the negative electrode substrate. The configuration of the intermediate layer of the negative electrode is not particularly limited and can be the same as that of the intermediate layer of the positive electrode.

[0081] The negative electrode substrate has conductivity. As the material of the negative electrode substrate, metals such as copper, nickel, stainless steel, nickel-plated steel, aluminum, or alloys thereof are used. Among these, copper or a copper alloy is preferable. Examples of the negative electrode substrate include a foil and a vapor deposition film, and a foil is preferable from the viewpoint of cost. Therefore, a copper foil or a copper alloy foil is preferable as the negative electrode substrate. Examples of the copper foil include a rolled copper foil and an electrolytic copper foil.

[0082] The average thickness of the negative electrode substrate is preferably 3 μm or more and 30 μm or less, and more preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate to be equal to or greater than the above lower limit, the strength of the negative electrode substrate can be increased. By setting the average thickness of the negative electrode substrate to be equal to or less than the above upper limit, the energy density per volume of the secondary battery can be increased.

[0083] The negative electrode active material layer is a layer of a negative electrode mixture containing a negative electrode active material. The negative electrode active material layer (negative electrode mixture) may contain, in addition to the negative electrode active material, optional components such as a conductive agent, a binder, a thickener, and a filler, as necessary. As the optional components such as the conductive agent, the binder, the thickener, and the filler, the same ones as those used in the positive electrode active material layer can be used. The content of each of these optional components in the negative electrode active material layer can be within the range described as the content of these in the positive electrode active material layer.

[0084] The negative electrode active material can be appropriately selected from known negative electrode active materials. As the negative electrode active material for a lithium-ion secondary battery, a material that can occlude and release lithium ions is usually used. Examples of the negative electrode active material include metallic Li; metals or semi-metals such as Si and Sn; metal oxides or semi-metal oxides such as SiO2, TiO2, and SnO2; Li4Ti5O 12 , LiTiO 2、 titanium-containing oxides such as TiNb2O7; polyphosphoric acid compounds; silicon carbide; carbon materials such as graphite (graphite), non-graphitic carbon (easily graphitizable carbon or hardly graphitizable carbon), etc. In the negative electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used.

[0085] "Graphite" refers to a carbon material having an average lattice plane spacing (d 002 ) of the (002) plane determined by X-ray diffraction method of 0.33 nm or more and less than 0.34 nm before charge-discharge or in the discharged state. Examples of graphite include natural graphite and artificial graphite. From the viewpoint of obtaining a material with stable physical properties, artificial graphite is preferred.

[0086] "Non-graphitic carbon" refers to a carbon material having an average lattice plane spacing (d 002 ) of the (002) plane determined by X-ray diffraction method of 0.34 nm or more and 0.42 nm or less before charge-discharge or in the discharged state. Examples of non-graphitic carbon include hardly graphitizable carbon and easily graphitizable carbon. Examples of non-graphitic carbon include materials derived from resins, petroleum pitch or materials derived from petroleum pitch, petroleum coke or materials derived from petroleum coke, plant-derived materials, alcohol-derived materials, etc.

[0087] Here, the "discharged state" that defines graphite and non-graphitic carbon means a state in which the open-circuit voltage is 0.7 V or higher in a single-pole battery using a negative electrode containing a carbon material as the working electrode and metallic Li as the counter electrode. Since the potential of the metallic Li counter electrode in the open-circuit state is approximately equal to the oxidation-reduction potential of Li, the open-circuit voltage in the above single-pole battery is approximately equal to the potential of the negative electrode containing the carbon material with respect to the oxidation-reduction potential of Li. That is, the fact that the open-circuit voltage in the above single-pole battery is 0.7 V or higher means that lithium ions that can be occluded and released during charge and discharge are sufficiently released from the carbon material that is the negative electrode active material.

[0088] "Carbon with poor graphitization property" refers to a carbon material having a d 002 of 0.36 nm or more and 0.42 nm or less.

[0089] "Carbon with easy graphitization property" refers to a carbon material having a d 002 of 0.34 nm or more and less than 0.36 nm.

[0090] In order to obtain a secondary battery with a high capacity retention rate, etc., as the negative electrode active material, a carbon material is preferable, and graphite is more preferable. When a carbon material is used as the negative electrode active material, the content of the carbon material in all the negative electrode active materials may be 50% by mass or more, may be 70% by mass or more, may be 90% by mass or more, or may be substantially 100% by mass.

[0091] The negative electrode active material is usually particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. By setting the average particle size of the negative electrode active material to the above lower limit or more, the production or handling of the negative electrode active material becomes easy. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electron conductivity of the active material layer is improved. In order to obtain powder with a predetermined particle size, a pulverizer, a classifier, etc. are used. The pulverization method and the classification method can be selected, for example, from the methods exemplified for the positive electrode above.

[0092] The content of the negative electrode active material in the negative electrode active material layer (negative electrode mixture) is preferably 60% by mass or more and 99% by mass or less, more preferably 90% by mass or more and 98% by mass or less. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the negative electrode active material layer.

[0093] The negative electrode active material layer may contain typical non-metal elements such as B, N, P, F, Cl, Br, I, etc., typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, etc., and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W, etc. as components other than the negative electrode active material, conductive agent, binder, thickener, and filler.

[0094] (Separator) The separator can be appropriately selected from known separators. As the separator, for example, a separator composed only of a base material layer, a separator in which a heat-resistant layer containing heat-resistant particles and a binder is formed on one or both surfaces of the base material layer, etc. can be used. Examples of the material of the base material layer of the separator include woven fabric, non-woven fabric, porous resin film, etc. Among these materials, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of the liquid retention property of the non-aqueous electrolyte. As the material of the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of the shut-down function, and polyimides and aramids are preferable from the viewpoint of oxidation decomposition resistance. As the base material layer of the separator, a material obtained by compounding these resins may be used.

[0095] The heat-resistant particles contained in the heat-resistant layer preferably have a mass reduction of 5% or less at 500 °C in air, and more preferably have a mass reduction of 5% or less at 800 °C in air. Examples of materials with a mass reduction of a predetermined amount or less include inorganic compounds. Examples of inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ionic crystals such as calcium fluoride and barium fluoride; covalent crystals such as silicon and diamond; and mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof. As the inorganic compound, these substances may be used alone or in combination, or two or more of them may be mixed and used. Among these inorganic compounds, from the viewpoint of the safety of the secondary battery, silicon oxide, aluminum oxide, or aluminosilicate is preferable.

[0096] From the viewpoint of strength, the porosity of the separator is preferably 80% by volume or less, and from the viewpoint of discharge performance, it is preferably 20% by volume or more. Here, the "porosity" is a volume-based value and means the measured value by a mercury porosimeter.

[0097] As the separator, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone, and polyvinylidene fluoride. Using a polymer gel has the effect of suppressing liquid leakage. As the separator, a porous resin film or non-woven fabric as described above may be used in combination with a polymer gel.

[0098] (Non-aqueous electrolyte) The non-aqueous electrolyte can be appropriately selected from known non-aqueous electrolytes. A non-aqueous electrolyte solution may be used as the non-aqueous electrolyte. The non-aqueous electrolyte solution contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

[0099] The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphate esters, sulfonic acid esters, ethers, amides, nitriles, etc. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are substituted with halogens may be used. For example, by using a fluorinated compound (fluorinated cyclic carbonate, fluorinated chain carbonate, etc.), it can be sufficiently used even under usage conditions where the positive electrode potential reaches a high potential.

[0100] Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, etc. Among these, EC, PC, and FEC are preferred.

[0101] Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, methyl trifluoroethyl carbonate (MFEC), bis(trifluoroethyl) carbonate, etc. Among these, EMC and MFEC are preferred.

[0102] As the non-aqueous solvent, it is preferable to use a cyclic carbonate or a chain carbonate, and it is more preferable to use a cyclic carbonate and a chain carbonate in combination. By using a cyclic carbonate, the dissociation of the electrolyte salt can be promoted and the ionic conductivity of the non-aqueous electrolyte can be improved. By using a chain carbonate, the viscosity of the non-aqueous electrolyte can be kept low. When a cyclic carbonate and a chain carbonate are used in combination, the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate: chain carbonate) is preferably in the range of, for example, 5:95 to 50:50.

[0103] As the electrolyte salt, it can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include lithium salts, sodium salts, potassium salts, magnesium salts, onium salts, etc. Among these, lithium salts are preferable.

[0104] Examples of the lithium salt include inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, LiN(SO2F)2, etc., and lithium salts having a halogenated hydrocarbon group such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, LiC(SO2C2F5)3, etc. Among these, inorganic lithium salts are preferable, and LiPF6 is more preferable.

[0105] The content of the electrolyte salt in the non-aqueous electrolyte is preferably 0.1 mol / dm 3 or more and 2.5 mol / dm 3 or less, more preferably 0.3 mol / dm 3 or more and 2.0 mol / dm 3 or less, even more preferably 0.5 mol / dm 3 or more and 1.7 mol / dm 3 or less, particularly preferably 0.7 mol / dm 3 or more and 1.5 mol / dm 3 or less. By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

[0106] The non-aqueous electrolyte may contain an additive. Examples of the additive include aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; partial halides of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; halogenated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyl disulfide, dipyridinium disulfide, perfluorooctane, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, tetrakis(trimethylsilyl) titanate, etc. These additives may be used alone or in combination of two or more.

[0107] The content of the additive contained in the non-aqueous electrolyte is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, still more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less based on the mass of the entire non-aqueous electrolyte. By setting the content of the additive within the above range, the capacity retention performance or cycle performance after high-temperature storage can be improved, or the safety can be further improved.

[0108] A solid electrolyte may be used for the non-aqueous electrolyte, or a non-aqueous electrolyte and a solid electrolyte may be used in combination.

[0109] As the solid electrolyte, any material having ion conductivity such as lithium, sodium, calcium, etc. and being solid at room temperature (for example, 15°C or higher and 25°C or lower) can be selected. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, polymer solid electrolytes, and the like.

[0110] Examples of the sulfide solid electrolyte in the case of a lithium-ion secondary battery include, for example, Li2S-P2S5, LiI-Li2S-P2S5, Li 10 Ge-P2S 12 and the like.

[0111] (Positive electrode potential at the end-of-charge voltage during normal use) In the secondary battery (non-aqueous electrolyte storage element), the positive electrode potential (positive electrode reaching potential) at the end-of-charge voltage during normal use is not particularly limited, but less than 4.5V vs. Li / Li + is preferable, less than 4.45V vs. Li / Li + is more preferable, and in some cases, less than 4.4V vs. Li / Li + is even more preferable. By setting the positive electrode potential at the end-of-charge voltage during normal use to be equal to or lower than the above upper limit, the increase in internal resistance associated with charge-discharge cycles is sufficiently suppressed. Also, by setting the positive electrode potential at the end-of-charge voltage during normal use to be equal to or lower than the above upper limit, aging over time gradually progresses, so that the capacity retention rate can be increased.

[0112] In the secondary battery, the positive electrode potential at the end-of-charge voltage during normal use is preferably more than 4.25V vs. Li / Li + more preferably more than 4.3V vs. Li / Li + and even more preferably more than 4.35V vs. Li / Li +The above may be even more preferable. By setting the positive electrode potential at the charging end voltage during normal use to be equal to or higher than the above lower limit, the discharge capacity can be increased, and the energy density, output performance, etc. can be enhanced. Further, by setting the positive electrode potential at the charging end voltage during normal use to be equal to or higher than the above lower limit, sufficient aging progresses during normal charging, so that the capacity retention rate can be increased.

[0113] The positive electrode potential at the charging end voltage during normal use in the secondary battery may be within the range between any of the above-mentioned upper limits and any of the above-mentioned lower limits.

[0114] <Method of using non-aqueous electrolyte storage element> The method of using the secondary battery (non-aqueous electrolyte storage element) according to an embodiment of the present invention is not particularly limited, but the following method is preferable. That is, the method of using the secondary battery according to an embodiment of the present invention includes charging the secondary battery within a range where the positive electrode potential (positive electrode reaching potential) is less than 4.5 V vs. Li / Li + According to this usage method, an increase in internal resistance associated with the charge-discharge cycle of the secondary battery using a lithium-excess type active material for the positive electrode is suppressed. Further, according to this usage method, the secondary battery can be repeatedly used with a high capacity retention rate.

[0115] The upper limit of the positive electrode potential (positive electrode reaching potential) in this charging is preferably less than 4.45 V vs. Li / Li + more preferably less than 4.4 V vs. Li / Li + and even more preferably less than 4.4 V vs. Li / Li in some cases. Further, the lower limit of the positive electrode potential in this charging is preferably more than 4.25 V vs. Li / Li + more preferably more than 4.3 V vs. Li / Li + even more preferably more than 4.35 V vs. Li / Li + and even more preferably more than 4.35 V vs. Li / Li in some cases.

[0116] This usage method may be the same as the conventionally known method of using a secondary battery except that the positive electrode potential (positive electrode reaching potential) in charging is set as described above.

[0117] <Method for manufacturing non-aqueous electrolyte storage element> The manufacturing method of a secondary battery (non-aqueous electrolyte storage element) according to an embodiment of the present invention includes assembling an uncharged and discharged non-aqueous electrolyte storage element including a positive electrode, a negative electrode, and a non-aqueous electrolyte, and performing initial charge and discharge on this uncharged and discharged non-aqueous electrolyte storage element. In this initial charge and discharge, the positive electrode potential (positive electrode reaching potential) is 4.5V vs.Li / Li + Initial charge and discharge is performed in a range less than. The positive electrode contains the positive electrode active material particles described above. According to this manufacturing method, a secondary battery using a lithium-excess type active material for the positive electrode, in which an increase in internal resistance associated with charge and discharge cycles is suppressed, can be manufactured. Further, according to this manufacturing method, a secondary battery with a high capacity retention rate in charge and discharge cycles can be manufactured.

[0118] In addition, in this manufacturing method, the initial charge and discharge does not actively activate the lithium-excess type active material, and may be performed, for example, for capacity confirmation. That is, the initial charge and discharge is simply the charge and discharge performed for the first time after assembling the uncharged and discharged non-aqueous electrolyte storage element. The number of charge and discharge cycles in the initial charge and discharge may be 1 or 2, or may be 3 or more.

[0119] The upper limit of the positive electrode potential (positive electrode reaching potential) in the initial charge and discharge is 4.45V vs.Li / Li + It may be less than, and 4.4V vs.Li / Li + It may also be less than. On the other hand, the lower limit of the positive electrode potential in the initial charge and discharge is not particularly limited, and for example, it may be more than 4.25V vs.Li / Li + It may be more than, 4.3V vs.Li / Li + Or more than 4.35V vs.Li / Li + Or more.

[0120] Assembling an uncharged non-aqueous electrolyte storage element including a positive electrode, a negative electrode, and a non-aqueous electrolyte includes, for example, preparing an electrode body, preparing a non-aqueous electrolyte, and accommodating the electrode body and the non-aqueous electrolyte in a container. Preparing the electrode body includes preparing a positive electrode, preparing a negative electrode, and forming the electrode body by laminating or winding the positive electrode and the negative electrode with a separator interposed therebetween.

[0121] Preparing the positive electrode can be carried out by applying a positive electrode mixture paste directly to the positive electrode substrate or via an intermediate layer and drying it. The positive electrode mixture paste contains components constituting a positive electrode active material layer (positive electrode mixture), such as positive electrode active material particles, and a dispersion medium. A suitable manufacturing method for the positive electrode active material particles is as described above. That is, the method for manufacturing the secondary battery or preparing the positive electrode preferably includes obtaining positive electrode active material particles by firing a mixture containing a positive electrode active material precursor, a lithium compound, and an aluminum compound.

[0122] Preparing the negative electrode can be carried out, for example, by applying a negative electrode mixture paste directly to the negative electrode substrate or via an intermediate layer and drying it. The negative electrode mixture paste contains components constituting a negative electrode active material layer (negative electrode mixture), such as a negative electrode active material, and a dispersion medium.

[0123] <Other Embodiments> The non-aqueous electrolyte storage element of the present invention is not limited to the above embodiments, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of one embodiment can be added with the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a well-known technique. Further, a part of the configuration of one embodiment can be deleted. Also, a well-known technique can be added to the configuration of one embodiment.

[0124] In the above-described embodiment, the non-aqueous electrolyte power storage device has been mainly described in the form of a non-aqueous electrolyte secondary battery, but other non-aqueous electrolyte power storage devices may also be used. Examples of other non-aqueous electrolyte power storage devices include capacitors (electric double layer capacitors, lithium ion capacitors), etc.

[0125] FIG. 1 shows a schematic view of a rectangular non-aqueous electrolyte power storage device 1 (non-aqueous electrolyte secondary battery), which is an embodiment of the non-aqueous electrolyte power storage device according to the present invention. Note that this figure is a perspective view of the inside of the container. In the non-aqueous electrolyte power storage device 1 shown in FIG. 1, an electrode body 2 is housed in a container 3. The electrode body 2 is formed by winding a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material with a separator interposed therebetween. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41, and the negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.

[0126] The configuration of the non-aqueous electrolyte power storage device according to the present invention is not particularly limited, and examples include a cylindrical battery, a prismatic battery (rectangular battery), a flat battery, etc. The power storage device according to an embodiment of the present invention includes two or more non-aqueous electrolyte power storage devices, and includes one or more non-aqueous electrolyte power storage devices according to the above-described embodiment (hereinafter referred to as "second embodiment"). Regarding at least one non-aqueous electrolyte power storage device included in the power storage device according to the second embodiment, the technology according to an embodiment of the present invention may be applied. It may include one non-aqueous electrolyte power storage device according to the above-described embodiment and one or more non-aqueous electrolyte power storage devices not according to the above-described embodiment, or may include two or more non-aqueous electrolyte power storage devices according to the above-described embodiment. An embodiment of the power storage device according to the second embodiment is shown in FIG. 2. In FIG. 2, the power storage device 30 according to the second embodiment includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of non-aqueous electrolyte power storage devices 1. The above-described power storage device 30 can be mounted as a power source for automobiles such as electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs).

Examples

[0127] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0128] [Example 1] (Preparation of hydroxide precursor) 315.4 g of nickel sulfate hexahydrate, 168.6 g of cobalt sulfate heptahydrate, and 530.4 g of manganese sulfate pentahydrate were weighed out. The total amount of these was dissolved in 4 dm of ion-exchanged water. 3 The molar ratio of Ni:Co:Mn was 30:15:55, and the mixture was dissolved in 1.0 mol / dm 3 Next, a 5 dm 3 2dm in the reaction vessel 3 The oxygen contained in the ion-exchanged water was removed by bubbling nitrogen gas for 30 minutes. The temperature of the reaction vessel was set at 50°C (±2°C), and the inside of the reaction vessel was stirred at a rotation speed of 1,500 rpm using a paddle blade equipped with a stirring motor, so that sufficient convection occurred in the reaction vessel. The sulfate stock solution was poured into the reaction vessel at a depth of 1.3 cm. 3 The solution was added dropwise to the reaction vessel at a rate of 4.0 mol / dm3 / min for 50 hours. 3 of sodium hydroxide, 1.25 mol / dm 3 of ammonia, and 0.1 mol / dm 3 The pH in the reaction vessel was controlled to be always 10.20 (±0.1) by appropriately dropping a mixed alkaline solution containing hydrazine of 1.0 mL. At the same time, a part of the reaction liquid was discharged by overflow, so that the total volume of the reaction liquid was always kept at 2 dm 3 The temperature was controlled so as not to exceed 100°C. After the dropwise addition, stirring in the reaction tank was continued for another hour. After stirring was stopped, the mixture was left to stand at room temperature for 12 hours or more. Next, the hydroxide precursor particles generated in the reaction tank were separated using a suction filtration device, and sodium ions attached to the particles were washed and removed using ion-exchanged water. The hydroxide precursor particles were dried in an air atmosphere at normal pressure and 80°C for 20 hours using an electric furnace. Then, in order to make the particle size uniform, the hydroxide precursor was ground for several minutes in an automatic agate mortar. In this way, a hydroxide precursor with a molar ratio of Ni:Co:Mn of 30:15:55 was obtained.

[0129] (Preparation of Cathode Active Material Particles) Lithium hydroxide monohydrate and aluminum oxide Al2O3 were added to the obtained hydroxide precursor, and they were thoroughly mixed using an automatic agate mortar. A mixed powder with a molar ratio of Li / (Ni, Co, Mn) (Li / Me) of 1.1 was prepared. The addition ratio of aluminum oxide was adjusted so that the molar ratio of Al / (Ni, Co, Mn) (Al / Me) was 0.005. The above mixed powder was pelletized. The pellet was placed in an alumina boat, and using a box-type electric furnace (model number: AMF20), the temperature was raised from room temperature to 900 °C over 10 hours under normal pressure in an air atmosphere and fired at 900 °C for 4 hours. After firing, the heater switch was turned off, and the alumina boat was allowed to cool naturally while remaining in the furnace. As a result, the temperature of the furnace decreased to about 200 °C after 5 hours, but the subsequent temperature decrease rate was somewhat slow. After one day and night had passed, after confirming that the temperature of the furnace was 60 °C or lower, the pellet was taken out and pulverized for several minutes using an automatic agate mortar to make the particle sizes uniform. In this way, cathode active material particles containing a lithium transition metal composite oxide (Ni:Co:Mn = 30:15:55, Li / Me = 1.1) were prepared. For the obtained cathode active material particles, powder X-ray diffraction measurement was performed using an X-ray diffractometer (manufactured by Rigaku, model name: MiniFlex II). It was confirmed that the lithium transition metal composite oxide in the obtained cathode active material particles had an α-NaFeO2 structure and that there was a diffraction peak in the range of 20° or more and 22° or less in the X-ray diffraction pattern. When the peak differential pore volume of the obtained cathode active material particles was measured by the method described above, it was 0.038 mm 3 / (g·nm).

[0130] (Preparation of Cathode) The positive electrode mixture paste was prepared with the obtained positive electrode active material particles, acetylene black (AB), and polyvinylidene fluoride (PVDF) contained at a ratio (in terms of solid content) of 90:5:5 by mass ratio, using N-methylpyrrolidone (NMP) as the dispersion medium. This positive electrode mixture paste was applied to an aluminum foil (thickness 15 μm) as the positive electrode substrate and dried to obtain a positive electrode.

[0131] (Fabrication of negative electrode) The negative electrode mixture paste was prepared with graphite as the negative electrode active material, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) contained at a ratio (in terms of solid content) of 96:3.2:0.8 by mass ratio, using water as the dispersion medium. This negative electrode mixture paste was applied to a strip-shaped copper foil (thickness 10 μm) as the negative electrode substrate and dried to obtain a negative electrode.

[0132] (Assembly of test battery) A test battery (non-aqueous electrolyte energy storage element) was assembled using the above positive electrode and the above negative electrode. As the non-aqueous electrolyte, a solution in which lithium hexafluorophosphate (LiPF6) was dissolved to a content of 1.0 mol / dm 3 in a non-aqueous solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:35:35 was used, and a microporous polyolefin membrane was used as the separator.

[0133] (Initial charge and discharge) The non-aqueous electrolyte energy storage element (uncharged non-aqueous electrolyte energy storage element) obtained before the initial charge and discharge was subjected to initial charge and discharge at 25°C as follows. Constant current and constant voltage charging was performed with a charging current of 0.1C and a charging termination voltage of 4.25V (the positive electrode reaching potential of 4.35V vs. Li / Li + ). The charging termination condition was set at the time when the current value decayed to 0.02C. Thereafter, constant current discharge was performed with a discharge current of 0.1C and a discharge termination voltage of 2.5V. By the above procedure, the non-aqueous electrolyte energy storage element of Example 1 was obtained.

[0134] [Examples 2 to 11, Comparative Examples 1 to 11, 13 to 16] Except that the molar ratio of lithium to transition metal (Li / Me) and the molar ratio of Ni, Co, and Mn (Ni:Co:Mn) in the target lithium transition metal composite oxide were adjusted to the values in Table 1, the amounts of nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate pentahydrate used, as well as the amounts of hydroxide precursor and lithium hydroxide monohydrate used, were adjusted. The firing temperature when preparing the positive electrode active material particles and the presence or absence of aluminum (Al) in the positive electrode active material particles were set as described in Table 1. The positive electrode potential at the initial charge and discharge was set to the potential described in Table 1. In the same manner as in Example 1, non-aqueous electrolyte storage elements of Examples 2 to 11 and Comparative Examples 1 to 11 and 13 to 16 were obtained. The presence or absence of aluminum (Al) in the positive electrode active material particles was adjusted by whether or not aluminum oxide Al2O3 was used when preparing the positive electrode active material particles.

[0135] [Example 12, Comparative Example 12] (Preparation of carbonate precursor) Weighed 17.7 g of nickel sulfate hexahydrate and 32.5 g of manganese sulfate pentahydrate, and dissolved the total amount in 200 cm of ion-exchanged water 3 to prepare a 1.0 M sulfate aqueous solution with a Ni:Mn molar ratio of 33:67. Next, 750 cm of ion-exchanged water was poured into a 2 dm 3 reaction vessel, and CO2 gas was bubbled for 30 minutes to dissolve CO2 in the ion-exchanged water. The temperature of the reaction vessel was set to 50 °C (±2 °C), and while stirring the inside of the reaction vessel at a rotation speed of 700 rpm using a paddle blade equipped with a stirring motor, the convection in the reaction layer was set to be sufficient. The total amount of the above sulfate aqueous solution was dropped at a rate of 2 cm 3 / min. Here, from the start to the end of the dropping, 1.0 mol / dm 3 3An aqueous solution containing sodium carbonate was appropriately dropped to control the pH in the reaction tank to always maintain 7.9 (±0.05). After the dropping was completed, stirring in the reaction tank was continued for another 5 hours. After stopping the stirring, it was left standing at room temperature for 12 hours or more. Next, using a suction filtration device, the carbonate precursor particles generated in the reaction tank were separated, and the sodium ions adhering to the particles were washed away using ion-exchanged water. These carbonate precursor particles were dried in an electric furnace at 80 °C for 20 hours under normal pressure in an air atmosphere. Thereafter, in order to make the particle sizes uniform, they were ground in an agate mortar for several minutes. In this way, a carbonate precursor with a Ni:Mn molar ratio of 1:3 was obtained.

[0136] (Preparation of Lithium Transition Metal Composite Oxide Particles) Lithium carbonate was added to the obtained carbonate precursor and thoroughly mixed using an agate mortar to prepare a mixed powder with a molar ratio of Li:(Ni,Mn) (Li / Me) of 1.3. The above mixed powder was pelletized. The pellet was placed in an alumina boat and, using a box-type electric furnace (model number: AMF20), the temperature was raised from room temperature to 890 °C over 10 hours under normal pressure in an air atmosphere and fired at 890 °C for 9 hours. After firing, the heater switch was turned off, and the alumina boat was left in the furnace and allowed to cool naturally. As a result, the temperature of the furnace decreased to about 200 °C after 5 hours, but the subsequent temperature decrease rate was rather slow. After one day and night had passed and it was confirmed that the temperature of the furnace was 60 °C or lower, the pellet was taken out and ground in an automatic agate mortar for several minutes to make the particle sizes uniform. In this way, lithium transition metal composite oxide particles (Ni:Mn = 33:67, Li / Me = 1.3) were prepared. These were used as the positive electrode active material particles according to Comparative Example 12.

[0137] (Aluminum Implantation into Lithium Transition Metal Composite Oxide Particles) 0.3 dm 3 In an Erlenmeyer flask of, aluminum sulfate hydrate was dissolved in ion-exchanged water to obtain a solution with a concentration of 0.5 mol / dm 3An aqueous solution containing aluminum sulfate was prepared and stirred at 25 °C using a stirrer at a rotation speed of 400 rpm. While stirring, 5.0 g of lithium transition metal composite oxide particles, which were the positive electrode active material particles according to Comparative Example 12 above, were added. Stirring was stopped 30 seconds after the addition, and the mixture was filtered by suction filtration, and then dried in air at normal pressure and 80 °C for 20 hours. Next, the solid was placed on the lid part of an alumina crucible, and using a box-type electric furnace (model number: AMF20), in an air atmosphere and under normal pressure, the temperature was raised from room temperature to 400 °C at a rate of 5 °C / min, held at 400 °C for 4 hours, and then allowed to cool naturally. In this way, a lithium transition metal composite oxide (Ni:Mn = 33:67, Li / Me = 1.3) with aluminum imparted was produced. This was used as the positive electrode active material particles according to Example 12.

[0138] Except for using the positive electrode active material particles of Example 12 and Comparative Example 12 above, non-aqueous electrolyte storage elements of Example 12 and Comparative Example 12 were obtained in the same manner as in Example 1.

[0139] For the positive electrode active material particles obtained in each example and comparative example, the peak differential pore volume was measured by the method described above. The measurement results are shown in Table 1. Also, for each non-aqueous electrolyte storage element, separately, in the state after initial charge and discharge, the positive electrode active material particles (lithium transition metal composite oxide) in the fully discharged state were taken out based on the method described above, and X-ray diffraction measurement was performed to confirm the presence or absence of diffraction peaks in the range of 20° or more and 22° or less. The results are shown in Table 1.

[0140] (Charge and Discharge Cycle Test) For each non-aqueous electrolyte storage element whose initial internal resistance was confirmed, a charge and discharge cycle test was performed at 45 °C in the following manner. Charge current 1.0C, charge termination voltage 4.25V (positive electrode arrival potential 4.35V vs. Li / Li +Constant current and constant voltage charging was performed. The charging termination condition was set at the time when the current value decayed to 0.05C. Thereafter, constant current discharging was performed with a discharging current of 1.0C and a discharging termination voltage of 2.5V. A rest period of 10 minutes was provided after charging and after discharging, respectively. This charge and discharge was carried out 100 cycles.

[0141] (Internal resistance increase rate) For each non-aqueous electrolyte storage element before the charge and discharge cycle test and after the charge and discharge cycle test, with a state where more than 10 minutes had elapsed after the end of discharge, the internal resistance (ACR) was measured using an AC impedance meter of 1 kHz. The increase rate (%) of the ACR after the charge and discharge cycle test with respect to the ACR before the charge and discharge cycle test was determined. The obtained internal resistance increase rate is shown in Table 1. Also, with respect to the internal resistance increase rate of the non-aqueous electrolyte storage elements of each comparative example using positive electrode active material particles not containing aluminum, it was evaluated whether the internal resistance increase rate of the non-aqueous electrolyte storage elements of each example etc. using positive electrode active material particles containing aluminum had decreased. Those in which the internal resistance increase rate has decreased by incorporating aluminum can be evaluated as having the increase in internal resistance associated with the charge and discharge cycle suppressed. This evaluation result is shown in Table 1 as the "suppression effect".

[0142]

Table 1

[0143] As can be seen from the comparison between Comparative Example 15 and Comparative Example 16, when a lithium transition metal composite oxide that is not a lithium excess type active material was used, when the positive electrode active material particles contained aluminum, the internal resistance increase rate after the charge and discharge cycle increased, and the suppression effect of the internal resistance increase did not appear. Also, in the non-aqueous electrolyte storage elements of these Comparative Examples 15 and 16, the internal resistance increase rate after the charge and discharge cycle all exceeded 10%, and the internal resistance increase rate was large.

[0144] As can be seen from the comparison between Comparative Example 13 and Comparative Example 14, even when a lithium-transition metal composite oxide, which is a lithium-excess type active material having no diffraction peak in the range of 20° or more and 22° or less in the X-ray diffraction pattern, is used, when aluminum is contained in the positive electrode active material particles, the increase rate of the internal resistance after charge and discharge cycles increases, and the effect of suppressing the increase in internal resistance is not exhibited. Further, in these non-aqueous electrolyte storage elements of Comparative Examples 13 and 14, the increase rate of the internal resistance after charge and discharge cycles all exceeded 10%, and the increase rate of the internal resistance was large.

[0145] On the other hand, as can be seen from the comparison between Examples 1 to 12 and Comparative Examples 1 to 12, when a lithium-transition metal composite oxide, which is a lithium-excess type active material having a diffraction peak in the range of 20° or more and 22° or less in the X-ray diffraction pattern, is used, when aluminum is contained in the positive electrode active material particles, the increase rate of the internal resistance after charge and discharge cycles decreases, and the effect of suppressing the increase in internal resistance can be confirmed. Further, among Examples 1 to 12, in the non-aqueous electrolyte storage elements of Examples 1 to 11 using positive electrode active material particles prepared using a hydroxide precursor and having a peak differential pore volume of 0.5 mm 3 / (g·nm) or less, the increase rate of the internal resistance after charge and discharge cycles was all less than 10%, and the increase rate of the internal resistance was very small.

Industrial Applicability

[0146] The present invention can be applied to non-aqueous electrolyte storage elements used as power sources for electronic devices such as personal computers and communication terminals, automobiles, industrial use, etc.

Explanation of Signs

[0147] 1 Non-aqueous electrolyte storage element 2 Electrode body 3 Container 4 Positive electrode terminal 41 Positive electrode lead 5 Negative electrode terminal 51 Negative electrode lead 20 Power storage unit 30 Power storage device

Claims

1. A non-aqueous electrolyte storage element comprising a positive electrode having positive electrode active material particles, The above positive electrode active material particles contain a lithium transition metal composite oxide having an α-NaFeO ２ structure, wherein the lithium transition metal composite oxide contains at least one of nickel and cobalt and manganese, wherein the content of lithium relative to the transition metal in the lithium transition metal composite oxide exceeds 1.0 in molar ratio, wherein in an X-ray diffraction pattern using CuKα rays of the lithium transition metal composite oxide, a diffraction peak exists in the range of 20° or more and 22° or less, wherein the positive electrode active material particles contain aluminum, and wherein the peak differential pore volume of the positive electrode active material particles is 0.5 mm3 / (g·nm) or less.

2. The non-aqueous electrolyte storage element according to claim 1, wherein the content of manganese relative to the transition metal in the lithium transition metal composite oxide is 0.3 or more and 0.65 or less in molar ratio.

3. The non-aqueous electrolyte storage element according to claim 1 or claim 2, wherein at least a part of the aluminum is present in a particulate form on the surface of the positive electrode active material particles.

4. The positive electrode potential at the charging cut-off voltage during normal use is less than 4.5 V vs. Li / Li ＋ The non-aqueous electrolyte storage element according to any one of claims 1 to 3, wherein the positive electrode potential at the charging cut-off voltage during normal use is less than 4.5 V vs. Li / Li

5. The positive electrode potential is 4.5 V vs. Li / Li ＋ The method for using a non-aqueous electrolyte storage element according to any one of claims 1 to 4, comprising charging in a range of less than

6. The positive electrode potential is 4.5 V vs. Li / Li ＋ The method for manufacturing a non-aqueous electrolyte storage element according to any one of claims 1 to 4, comprising performing initial charge and discharge in a range less than

7. A method for manufacturing a non-aqueous electrolyte storage element, the method comprising a positive electrode having positive electrode active material particles, wherein the positive electrode active material particles contain a lithium transition metal composite oxide having an α-NaFeO2 structure, wherein the lithium transition metal composite oxide contains at least one of nickel and cobalt and manganese, wherein the content of lithium relative to the transition metal in the lithium transition metal composite oxide exceeds 1.0 in molar ratio, wherein in an X-ray diffraction pattern using CuKα rays of the lithium transition metal composite oxide, a diffraction peak exists in the range of 20° or more and 22° or less, and wherein the positive electrode active material particles contain aluminum, the method comprising: obtaining the positive electrode active material particles by firing a mixture containing a positive electrode active material precursor, a lithium compound, and an aluminum compound, and performing initial charge and discharge in a range where the positive electrode potential is less than 4.5 V vs. Li / Li+. A method for manufacturing a non-aqueous electrolyte storage element comprising the above steps.

8. A power storage device comprising two or more non-aqueous electrolyte storage elements and one or more non-aqueous electrolyte storage elements according to any one of claims 1 to 4.

9. The method of using an electric storage device according to claim 8, comprising charging one or more of the non-aqueous electrolyte storage elements in a range where the positive electrode potential is less than 4.5 V vs. Li / Li ＋ ​

10. A method for manufacturing an electrical storage device according to claim 8, comprising performing initial charge and discharge on one or more of the non-aqueous electrolyte storage elements within a range where the positive electrode potential is less than 4.5 V vs. Li / Li ＋ ​

Images