Nonaqueous electrolyte power storage element

Abstract

A nonaqueous electrolyte power storage element according to one aspect of the present invention is provided with: a positive electrode which has a positive electrode active material layer that contains a positive electrode active material; and a negative electrode which has a negative electrode active material layer that contains a negative electrode active material. The negative electrode active material contains silicon oxide, and the mass per unit area of one negative electrode active material layer is 2 mg / cm2 or more. The ratio QCX / QAX of the initial irreversible capacity QCX per unit area of the positive electrode to the initial irreversible capacity QAX per unit area of the negative electrode is 1.5 or more, and the charge rate S of the negative electrode in a discharged state of the nonaqueous electrolyte power storage element per 1 mass% of the silicon oxide content in the negative electrode active material is 0.7% / mass% or more.

Description

Non-aqueous electrolyte energy storage element

[0001] This invention relates to a non-aqueous electrolyte energy storage element.

[0002] Non-aqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, are widely used in electronic devices like personal computers and communication terminals, as well as automobiles, due to their high energy density. Generally, non-aqueous electrolyte secondary batteries consist of an electrode body with a pair of electrodes electrically isolated by a separator, and a non-aqueous electrolyte interposed between the electrodes. They are configured to charge and discharge by transferring charge-transporting ions between the two electrodes. Besides secondary batteries, capacitors such as lithium-ion capacitors and electric double-layer capacitors are also widely used as non-aqueous electrolyte energy storage elements.

[0003] One such non-aqueous electrolyte energy storage element has been developed in which silicon oxide is used as the active material for the negative electrode (see Patent Documents 1 and 2). Silicon oxide has the advantage of having a larger charge / discharge capacity per unit mass compared to carbon materials, which are widely used as negative electrode active materials.

[0004] Japanese Patent Publication No. 2011-113863 Japanese Patent Publication No. 2015-053152

[0005] However, compared to carbon materials, silicon dioxide undergoes significant volume changes due to expansion and contraction during charging and discharging. Repeated expansion and contraction can easily lead to particle cracking and electrical isolation. Therefore, non-aqueous electrolyte energy storage devices using silicon dioxide have a low capacity retention rate during charge-discharge cycles.

[0006] The object of the present invention is to provide a non-aqueous electrolyte energy storage element that uses silicon oxide as the negative electrode and has a high capacity retention rate during charge-discharge cycles.

[0007] A non-aqueous electrolyte energy storage element according to one aspect of the present invention is a non-aqueous electrolyte energy storage element comprising a positive electrode having a positive electrode active material layer containing a positive electrode active material, and a negative electrode having a negative electrode active material layer containing a negative electrode active material, wherein the negative electrode active material contains silicon oxide, and the mass per unit area of ​​one negative electrode active material layer is 2 [mg / cm²]. ２ The above is the initial irreversible capacity Q per unit area of ​​the negative electrode. ＡＸThe initial irreversible capacity Q per unit area of the above positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸ is 1.5 or more, and the charging rate S of the negative electrode in the discharged state of the non-aqueous electrolyte storage element per 1 mass% of the content of silicon oxide in the negative electrode active material defined by the following formula (1) is 0.7 [% / mass%] or more. S = {[(Q ＣＸ -Q ＡＸ ) / Q ＡＹ × 100} / C ＳｉＯ ... (1) (In formula (1), Q ＣＸ is the initial irreversible capacity per unit area of the positive electrode (μAh / cm ２ ), Q ＡＸ is the initial irreversible capacity per unit area of the negative electrode (μAh / cm ２ ), Q ＡＹ is the initial discharge capacity per unit area of the negative electrode (μAh / cm ２ ), C ＳｉＯ ＳｉＯ is the content (mass%) of silicon oxide in the negative electrode active material.)

[0008] According to one aspect of the present invention, there is provided a non-aqueous electrolyte storage element using silicon oxide as a negative electrode, which can provide a non-aqueous electrolyte storage element having a high capacity retention rate in a charge-discharge cycle.

[0009] FIG. 1 is a diagram schematically showing the first charge-discharge curves of the positive electrode and the negative electrode of the non-aqueous electrolyte storage element according to one aspect of the present invention.FIG. 2 is a perspective view showing a non-aqueous electrolyte storage element according to an embodiment of the present invention.FIG. 3 is a schematic view showing a power storage device including a plurality of non-aqueous electrolyte storage elements according to an embodiment of the present invention.

[0010] First, the outline of the non-aqueous electrolyte storage element disclosed by this specification will be described.

[0011] [1] The non-aqueous electrolyte storage element according to one aspect of the present invention is a non-aqueous electrolyte storage element including a positive electrode having a positive electrode active material layer containing a positive electrode active material and a negative electrode having a negative electrode active material layer containing a negative electrode active material, the negative electrode active material contains silicon oxide, and the mass per unit area in one layer of the negative electrode active material layer is ２ 2 [mg / cmThe above is the initial irreversible capacity Q per unit area of ​​the negative electrode. ＡＸ The initial irreversible capacitance Q per unit area of ​​the above positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸ The value is 1.5 or greater, and the charge rate S of the negative electrode in the discharge state of the non-aqueous electrolyte energy storage element is 0.7 [% / mass%] or greater per 1% by mass of silicon oxide content in the negative electrode active material defined by the following formula (1). S = {[(Q ＣＸ -Q ＡＸ ) / Q ＡＹ ] × 100} / C ＳｉＯ ...(1) (In formula (1), Q ＣＸ This is the initial irreversible capacity (μAh / cm²) per unit area of ​​the above positive electrode. ２ ) and Q ＡＸ This is the initial irreversible capacity (μAh / cm²) per unit area of ​​the negative electrode. ２ ) and Q ＡＹ This is the initial discharge capacity per unit area of ​​the negative electrode (μAh / cm²). ２ ) and C ＳｉＯ This represents the silicon dioxide content (mass%) in the above-mentioned negative electrode active material.

[0012] The non-aqueous electrolyte energy storage element described in [1] above is a non-aqueous electrolyte energy storage element that uses silicon oxide as the negative electrode and has a high capacity retention rate in charge-discharge cycles. The reason for this effect is not clear, but the following can be inferred. First, Figure 1 will be explained. Figure 1 is a schematic diagram showing the initial charge-discharge curves of the positive electrode and negative electrode in the non-aqueous electrolyte energy storage element described in [1] above. In Figure 1, curve A (dashed line) represents the initial charge curve of the positive electrode, curve B (solid line) represents the initial discharge curve of the positive electrode, curve C (dashed line) represents the initial charge curve of the negative electrode, and curve D (solid line) represents the initial discharge curve of the negative electrode. Also, Q ＣＸ Q is the initial irreversible capacity per unit area of ​​the positive electrode. ＣＹ Q is the initial discharge capacity per unit area of ​​the positive electrode (initial reversible capacity). ＡＸ Q is the initial irreversible capacity per unit area of ​​the negative electrode. ＡＹThis represents the initial discharge capacity (initial reversible capacity) per unit area of ​​the negative electrode. Here, in conventional non-aqueous electrolyte energy storage elements using silicon oxide as the negative electrode, it is thought that a high negative electrode potential in the discharge state (when the depth of discharge (DOD) is 100%) causes a decrease in the capacity retention rate during charge-discharge cycles. According to the inventors' findings, specifically, when the negative electrode potential is 0.45V vs. Li / Li ＋ When the above conditions are met, a decrease in the capacity retention rate during charge-discharge cycles, which is due to silicon oxide being the negative electrode active material, is likely to occur. In particular, when the mass per unit area of ​​one negative electrode active material layer is 2 [mg / cm³] ２ If the value is greater than or equal to the value above, the effects of silicon oxide in the charge-discharge cycle become significant. Specifically, if the mass per unit area of ​​one negative electrode active material layer is large, volume changes due to expansion and contraction of silicon oxide and particle cracking are likely to occur, leading to delamination of the negative electrode active material layer and a significant decrease in capacity retention. In contrast, in the non-aqueous electrolyte energy storage element described in [1] above, the initial irreversible capacity Q per unit area of ​​the negative electrode ＡＸ The initial irreversible capacitance Q per unit area of ​​the positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸThe value is increased to 1.5 or more. By doing so, it becomes a so-called positive electrode capacity-limited non-aqueous electrolyte energy storage element, and the negative electrode potential in the discharge state becomes low. Note that "positive electrode capacity-limited" refers to an element designed so that the discharge state is reached when the positive electrode becomes unable to discharge first during the discharge process. On the other hand, "negative electrode capacity-limited" refers to an element designed so that the discharge state is reached when the negative electrode becomes unable to discharge first during the discharge process. In other words, in the case of a negative electrode capacity-limited non-aqueous electrolyte energy storage element, the discharge lower limit voltage is reached mainly by an increase in the negative electrode potential, whereas in the case of a positive electrode capacity-limited non-aqueous electrolyte energy storage element, the discharge lower limit voltage is reached mainly by a decrease in the positive electrode potential. For this reason, in the case of a positive electrode capacity-limited non-aqueous electrolyte energy storage element, the negative electrode potential in the discharge state is low. Furthermore, in the non-aqueous electrolyte energy storage element described in [1] above, the charge rate S of the negative electrode in the discharge state of the non-aqueous electrolyte energy storage element per 1% by mass of silicon oxide content in the negative electrode active material defined by formula (1) is 0.7 [% / mass%] or more. This means that even in the discharge state, a certain amount of charge transport ions (e.g., lithium ions) remain in the silicon oxide, which is the negative electrode active material (there is a certain amount of remaining discharge capacity). In such a case, the degree of contraction of the silicon oxide in the discharge state is suppressed. Thus, in the non-aqueous electrolyte energy storage element described in [1] above, the ratio Q ＣＸ / Q ＡＸ Since the ratio is 1.5 or higher and the charge rate S is 0.7 [% / mass%] or higher, the volume change due to the expansion and contraction of silicon oxide particles is reduced. As a result, cracking and isolation of silicon oxide particles, as well as peeling of the negative electrode active material layer, are suppressed, and it is presumed that the capacity retention rate during the charge-discharge cycle is increased.

[0013] The initial irreversible capacity (Q) per unit area of ​​the positive electrode in a non-aqueous electrolyte energy storage element. ＣＸ ), the initial discharge capacity per unit area of ​​the positive electrode (Q ＣＹ ), the initial irreversible capacity per unit area of ​​the negative electrode (Q ＡＸ ) and the initial discharge capacity per unit area of ​​the negative electrode (Q ＡＹThese values ​​can be set in the design conditions of the non-aqueous electrolyte energy storage element. Each of these values ​​is measured from a non-aqueous electrolyte energy storage element in the state in which it is shipped from the manufacturing plant and distributed to the market by the following procedure. Note that "per unit area of ​​positive electrode" refers to the unit area of ​​the positive electrode active material layer that contributes to charging and discharging in opposition to the negative electrode active material layer. Similarly, "per unit area of ​​negative electrode" refers to the unit area of ​​the negative electrode active material layer that contributes to charging and discharging in opposition to the positive electrode active material layer.

[0014] First, the non-aqueous electrolyte energy storage element is charged with a constant current of 0.05C until it reaches the charging termination voltage for normal use, bringing it to a fully charged state. After a 30-minute rest, it is discharged with a constant current of 0.05C until it reaches the discharge termination voltage for normal use. "Normal use" refers to using the non-aqueous electrolyte energy storage element under the recommended or specified charge / discharge conditions, and, if equipment for using the non-aqueous electrolyte energy storage element is available, using that equipment. Next, the element is disassembled, and the negative and positive electrodes are removed. A certain area is cut from the region of the removed negative electrode that was facing the positive electrode to be used as the working electrode, and multiple test batteries A are assembled with a metallic lithium electrode as the counter electrode, and these are divided into multiple groups. Pure metallic lithium is used for the metallic lithium electrode here. Hereafter, for test battery A, the operation of applying current in the direction in which the negative electrode is electrochemically reduced is called charging, and the operation of applying current in the direction in which the negative electrode is electrochemically oxidized is called discharging. Test battery B is assembled using a working electrode, which is a portion of the region of the extracted positive electrode that was opposite the negative electrode, and a metallic lithium electrode as the counter electrode. Pure metallic lithium is used for the metallic lithium electrode in this test.

[0015] (1) Q ＣＸ -Q ＡＸ and Q ＡＹ For one group of test batteries A assembled from multiple units, the discharge current was set to a current equivalent to 0.05C in the non-aqueous electrolyte energy storage element before disassembly, and the potential of the negative electrode (working electrode) was set to 2.0V vs. Li / Li. ＋Constant current discharge is performed until the following occurs. The amount of electricity discharged per unit area of ​​the negative electrode at this time is equal to the initial irreversible capacitance (Q) per unit area of ​​the positive electrode. ＣＸ ) and the initial irreversible capacity (Q) per unit area of ​​the negative electrode ＡＸ ) The difference (Q ＣＸ -Q ＡＸ Next, the same current as the discharge current is used as the charging current, and the potential of the negative electrode (working electrode) is 0.02V vs. Li / Li ＋ Constant current charging is performed until the voltage reaches a certain level, and then constant potential charging is performed until the total charging time at that potential is 30 hours. After that, the same current as the discharge current is used to charge the negative electrode at a potential of 2.0V vs. Li / Li. ＋ Constant current discharge is performed until the following occurs. The amount of electricity discharged per unit area of ​​the negative electrode at this time is the reversible capacity, and the initial discharge capacity per unit area of ​​the negative electrode (Q) ＡＹ )

[0016] (2) Q ＡＸ and Q ＣＸ For the other group of test batteries A assembled from multiple units that were not used in (1) above, the discharge current was set to the same current as the discharge current corresponding to 0.05C in the non-aqueous electrolyte energy storage element before disassembly, and the potential of the negative electrode (working electrode) was set to 2.0V vs. Li / Li ＋ After performing constant current discharge until the desired result is reached, the device is disassembled again, the negative electrode (working electrode) is removed, the negative electrode active material layer from which the negative electrode substrate has been removed is dissolved in aqua regia, and the lithium ion content in the dissolved components is measured by ion chromatography. From this lithium ion content and the area of ​​the negative electrode (working electrode), the initial irreversible capacity (Q) per unit area of ​​the negative electrode is calculated. ＡＸ ) is calculated. Also, this Q ＡＸ And Q obtained in (1) above ＣＸ -Q ＡＸ Therefore, the initial irreversible capacitance (Q) per unit area of ​​the positive electrode ＣＸ ) calculate the ratio Q ＣＸ / Q ＡＸ Calculate.

[0017] (3) Q ＣＹFor the assembled test battery B, the charging current was set to a current equivalent to 0.05C in the non-aqueous electrolyte energy storage element before disassembly, and the potential of the positive electrode (working electrode) was compared to the positive electrode potential (V vs. Li / Li) when the state of charge (SOC) of the non-aqueous electrolyte energy storage element before disassembly was 100%. ＋ Constant current charging is performed until the potential reaches ), and then constant potential charging is performed until the total charging time at that potential is 30 hours. After that, the discharge current is set to a current equivalent to 0.05C in the non-aqueous electrolyte energy storage element before dismantling, and the potential of the positive electrode is set to the positive electrode potential (V vs. Li / Li) in the non-aqueous electrolyte energy storage element when the SOC is 0% before dismantling. ＋ Constant current discharge is performed until the value reaches ). The amount of electricity discharged per unit area of ​​the positive electrode at this time is the reversible capacity, and the initial discharge capacity per unit area of ​​the positive electrode is (Q). ＣＹ )

[0018] The silicon dioxide content in the negative electrode active material is measured either on the negative electrode active material (silicon dioxide and any other negative electrode active material) before charging and discharging, or, in the case of the negative electrode active material contained in the negative electrode of a non-aqueous electrolyte energy storage element, on the material after being treated according to the following procedure. For the other group of test batteries A assembled from multiple units that are not used in either (1) or (2) above, the discharge current is set to a current equivalent to 0.05C in the non-aqueous electrolyte energy storage element before disassembly, and the potential of the negative electrode (working electrode) is set to 2.0V vs. Li / Li ＋ Constant current discharge is performed until the negative electrode is fully discharged. Then, it is disassembled again and the negative electrode (working electrode) is removed. The removed negative electrode is washed with dimethyl carbonate. After that, the negative electrode active material layer containing the negative electrode active material is peeled off from the negative electrode substrate, and the negative electrode active material layer is washed with a binder-soluble solvent to remove the binder. The washed negative electrode active material layer is immersed in an acid or alkaline solution to remove metals derived from the negative electrode substrate and the SEI (solid electrolyte interface) coating, etc. After that, it is washed with water and dried under reduced pressure at room temperature for 24 hours to obtain the negative electrode active material. Disassembly of the non-aqueous electrolyte energy storage element and each test battery is performed in an argon atmosphere with a dew point of -60°C or lower.

[0019] [2] In the non-aqueous electrolyte energy storage element described in [1] above, the negative electrode active material may further contain a carbon-based active material.

[0020] The non-aqueous electrolyte energy storage element described in [2] above can achieve a lower negative electrode potential in the discharge state, thereby increasing the capacity retention rate during charge-discharge cycles.

[0021] "Carbon-based active material" refers to a carbon material used as the negative electrode active material. A carbon material is a material whose main constituent element is carbon. The main constituent element is the element that is present in the largest quantity by mass.

[0022] [3] In the non-aqueous electrolyte energy storage element described in [2] above, the positive electrode active material may contain a lithium transition metal composite oxide in which the nickel element content relative to all metal elements other than lithium is 70 mol% or more, and the carbon-based active material may contain artificial graphite.

[0023] The non-aqueous electrolyte energy storage element described in [3] above can achieve a higher capacity retention rate during charge-discharge cycles by lowering the negative electrode potential in the discharge state, among other things.

[0024] The elemental composition ratio of lithium transition metal composite oxides is measured either on the lithium transition metal composite oxide before charging and discharging, or, in the case of lithium transition metal composite oxide contained in the positive electrode of a non-aqueous electrolyte energy storage element, on a material treated according to the following procedure. First, the non-aqueous electrolyte energy storage element is charged with a constant current of 0.05 C until it reaches the charging termination voltage for normal use, bringing it to a fully charged state. After a 30-minute rest, it is discharged with a constant current of 0.05 C until it reaches the discharge termination voltage for normal use. It is then disassembled, the positive electrode is removed, and a test battery D is assembled with the removed positive electrode as the working electrode and the metallic lithium electrode as the counter electrode. Pure metallic lithium is used for the metallic lithium electrode here. For test battery D, with a current of 10 mA per gram of positive electrode active material, the potential of the positive electrode (working electrode) is 2.0 V vs. Li / Li ＋Constant current discharge is performed until the positive electrode is fully discharged. The device is disassembled again and the positive electrode is removed. The removed positive electrode is washed with dimethyl carbonate. Then, the positive electrode active material layer containing the lithium transition metal composite oxide is peeled off from the positive electrode substrate, and the positive electrode active material layer is washed with a solvent capable of dissolving the binder to remove the binder. After that, it is washed with water and dried under reduced pressure at room temperature for 24 hours to obtain the lithium transition metal composite oxide. The obtained lithium transition metal composite oxide is subjected to measurement. The work from disassembling the non-aqueous electrolyte energy storage element to obtaining the lithium transition metal composite oxide is carried out in an argon atmosphere with a dew point of -60°C or lower.

[0025] "Artificial graphite" refers to graphite that is produced artificially. "Graphite" is defined as the average lattice plane spacing (d) of the (002) plane, which is determined by X-ray diffraction before charging or discharging or during the discharge state. ００２) refers to carbon materials with a nautical radius of 0.33 nm or more and less than 0.34 nm. Here, the "discharge state" of a carbon-based active material means a state in which the carbon-based active material, which is the negative electrode active material, is discharged in such a way that sufficient charge transport ions (e.g., lithium ions) that can be absorbed and released during charging and discharging are released. For example, in a half-cell using a negative electrode containing a carbon-based active material as the negative electrode active material as the working electrode and metallic lithium as the counter electrode, this is a state in which the open-circuit voltage is 0.7 V or higher. Artificial graphite may be such that, in the X-ray diffraction pattern using CuKα rays, only two peaks appear in the diffraction angle 2θ range of 40° to 50°. In the case of natural graphite, it is said that a total of four peaks appear in the diffraction angle 2θ range of 40° to 50°: two peaks originating from the hexagonal crystal system structure and two peaks originating from the rhombohedral crystal system structure. In contrast, in the case of artificial graphite, it is generally said that only two peaks originating from the hexagonal crystal system structure appear. X-ray diffraction measurements of carbon-based active materials are performed on the carbon-based active material before charging and discharging, or, in the case of carbon-based active materials contained in the negative electrode of a non-aqueous electrolyte energy storage element, on a sample treated using the same procedure as the measurement of silicon dioxide content in the negative electrode active material described above. X-ray diffraction measurements of carbon-based active materials are performed by powder X-ray diffraction measurement using an X-ray diffractometer (Rigaku "MiniFlex II"), with the radiation source being CuKα rays, the tube voltage being 30kV, and the tube current being 15mA. At this time, the diffracted X-rays pass through a 30μm thick Kβ filter and are detected by a high-speed one-dimensional detector (D / teX Ultra 2). The sampling width is 0.02°, the scan speed is 5° / min, the diverging slit width is 0.625°, the receiving slit width is 13mm (OPEN), and the scattering slit width is 8mm. Furthermore, the Kα2 line is removed from the CuKα line, and an X-ray diffraction pattern based on the Kα1 line is obtained.

[0026] [4] In any of the non-aqueous electrolyte energy storage elements described in [1] to [3] above, the initial charge capacity ratio R between the positive electrode and the negative electrode, as defined by the following formula (2), may be 1.10 or less. R = (Q ＣＸ +Q ＣＹ ) / (Q ＡＸ +Q ＡＹ ) ...(2) (In formula (2), QＡＸ Q ＣＸ and Q ＡＹ This is equivalent to equation (1). Q ＣＹ This is the initial discharge capacity per unit area of ​​the above positive electrode (μAh / cm²). ２ )

[0027] The denominator in equation (2) above is Q. ＡＸ (Initial irreversible capacity per unit area of ​​the negative electrode) and Q ＡＹ The sum of (initial discharge capacity per unit area of ​​the negative electrode) and Q is the initial charge capacity per unit area of ​​the negative electrode, and the numerator is Q. ＣＸ (Initial irreversible capacity per unit area of ​​the positive electrode) and Q ＣＹ The sum of (initial discharge capacity per unit area of ​​the positive electrode) and is the initial charge capacity per unit area of ​​the positive electrode (see Figure 1). In the non-aqueous electrolyte energy storage element described in [4] above, the initial charge capacity ratio R is 1.10 or less, and the initial charge capacity of the negative electrode is sufficiently large relative to the initial charge capacity of the positive electrode, so that deposition of metallic lithium and the like on the negative electrode surface is less likely to occur, and the charge / discharge performance can be improved.

[0028] A non-aqueous electrolyte energy storage element, a method for manufacturing a non-aqueous electrolyte energy storage element, an energy storage device, and other embodiments according to one embodiment of the present invention will be described in detail below.

[0029] <Non-aqueous electrolyte energy storage element> A non-aqueous electrolyte energy storage element according to one embodiment of the present invention comprises a positive electrode, a negative electrode, a non-aqueous electrolyte, and a container for housing them. The non-aqueous electrolyte energy storage element may further include a separator interposed between the positive electrode and the negative electrode to electrically insulate them. The positive electrode, the negative electrode, and any separator typically constitute an electrode body. At least a portion of the non-aqueous electrolyte is usually present in a state of being impregnated into the electrode body. The non-aqueous electrolyte energy storage element according to one embodiment of the present invention may further include other components.

[0030] For example, the non-aqueous electrolyte energy storage element 1 shown in Figure 2, according to one embodiment of the present invention, comprises an electrode body 2, a non-aqueous electrolyte (not shown), and a rectangular parallelepiped container 3 that houses them. The non-aqueous electrolyte energy storage element 1 in Figure 2 further comprises a positive electrode lead 4, a positive electrode external terminal 5, a negative electrode lead 6, and a negative electrode external terminal 7. The positive electrode lead 4 and the negative electrode lead 6 are housed together with the electrode body 2, etc., inside the container 3. The positive electrode external terminal 5 and the negative electrode external terminal 7 are provided outside the container 3. The positive electrode constituting the electrode body 2 is electrically connected to the positive electrode external terminal 5 via the positive electrode lead 4. The negative electrode constituting the electrode body 2 is electrically connected to the negative electrode external terminal 7 via the negative electrode lead 6.

[0031] The non-aqueous electrolyte energy storage element of the present invention may also be a non-aqueous electrolyte secondary battery. The following will describe in detail the main components constituting the non-aqueous electrolyte energy storage element according to one embodiment of the present invention, focusing on the case where the non-aqueous electrolyte energy storage element is a non-aqueous electrolyte secondary battery (particularly a lithium-ion secondary battery), but this is not intended to limit the scope of application of the present invention.

[0032] Furthermore, the lower and upper limits of each numerical range described in the embodiments of the present invention can be combined in any way (however, the upper limit must be greater than the lower limit). Also, regarding the lower and upper limits of a numerical range, it means that the numerical range includes both the lower and upper limits. That is, a lower limit of A means that it is greater than or equal to A. Similarly, an upper limit of B means that it is less than or equal to B.

[0033] The positive electrode comprises a positive electrode substrate and a positive electrode active material layer laminated directly to the positive electrode substrate or via an intermediate layer. Typically, the positive electrode has a portion where the positive electrode substrate is exposed. This exposed portion of the positive electrode substrate is usually connected to the positive electrode lead described above. The positive electrode may have a shape such as a sheet, plate, or strip.

[0034] The thickness of the positive electrode is appropriately set according to the use of the non-aqueous electrolyte storage element and the like. The average thickness of the positive electrode may be, for example, 3 μm or more and 1,000 μm or less. The lower limit of the average thickness of the positive electrode may be 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, 100 μm or 200 μm. The upper limit of the average thickness of the positive electrode may be 500 μm, 400 μm, 300 μm, 200 μm, 150 μm, 100 μm or 50 μm. The average thickness of the positive electrode is the average thickness of the portion where the positive electrode active material layer is laminated directly on the positive electrode substrate or through an intermediate layer. When both the portion where the positive electrode active material layer is laminated on both sides of the positive electrode substrate and the portion where the positive electrode active material layer is laminated on only one side of the positive electrode substrate exist, it is the average thickness of the portion where the positive electrode active material layer is laminated on both sides of the positive electrode substrate. In addition, in this specification, "average thickness" means the average value of the thicknesses measured at any five locations.

[0035] The positive electrode substrate has conductivity. In this specification, "having conductivity" means that the volume resistivity is 10 －２ Ω·cm or less. The volume resistivity is the value measured in accordance with JIS-H-0505 (1975). However, when it is difficult to prepare a test piece conforming to the standard, for example, when it is difficult to adopt the measurement method in accordance with JIS-H-0505 (l975), it is replaced with another measurement method that can obtain equivalent results. In this specification, "not having conductivity" or "(electric) insulating" means that the above volume resistivity is 10 ７ Ω·cm or more.

[0036] Examples of the material of the positive electrode substrate include metals such as aluminum, titanium, iron, and their alloys (such as stainless steel). Among these, aluminum or an aluminum alloy is preferable from the viewpoints of potential resistance, high electron conductivity, and cost.

[0037] The positive electrode substrate has a shape such as a sheet shape, a plate shape, or a strip shape, for example.When the form of the positive electrode substrate, a foil, a vapor-deposited film, a mesh, a porous material, etc. are mentioned, and a foil is preferable. The positive electrode substrate may be, for example, an aluminum foil or an aluminum alloy foil.

[0038] The average thickness of the positive electrode substrate may be, for example, 1 μm or more and 50 μm or less. The lower limit of the average thickness of the positive electrode substrate may be 3 μm, 5 μm, 8 μm, 10 μm, or 15 μm. The upper limit of the average thickness of the positive electrode substrate may be 40 μm, 30 μm, 20 μm, 15 μm, or 10 μm.

[0039] The intermediate layer is a layer placed between the positive electrode substrate and the positive electrode active material layer. The intermediate layer includes, for example, a conductive agent and a binder. When the intermediate layer contains a conductive agent, the contact resistance between the positive electrode substrate and the positive electrode active material layer can be reduced. Examples of conductive agents and binders used in the intermediate layer are the same as those used in the positive electrode active material layer, which will be described later.

[0040] The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer may optionally contain conductive agents, binders, thickeners, fillers, and other optional components. The positive electrode active material layer may be formed from a positive electrode mixture containing the positive electrode active material and other optional components. The positive electrode active material layer may be provided on only one side of a positive electrode substrate having a shape such as a sheet, or on both sides.

[0041] For the positive electrode active material, known positive electrode active materials can be used. For lithium-ion secondary batteries, materials capable of intercalating and releasing lithium ions are typically used. Examples of positive electrode active materials include lithium transition metal composite oxides, polyanion compounds, chalcogen compounds, sulfur-based materials, and lithium oxide. One or more positive electrode active materials can be used.

[0042] Examples of transition metal elements included in lithium transition metal composite oxides include nickel, cobalt, and manganese. Lithium transition metal composite oxides may also contain typical metal elements such as aluminum. An example of a lithium transition metal composite oxide is α-NaFeO ２ Examples include lithium transition metal composite oxides having a type crystal structure and lithium transition metal composite oxides having a spinel-type crystal structure.

[0043] α-NaFeO ２Examples of the lithium transition metal composite oxide having a spinel crystal structure include those represented by the following formula (i).

[0044] Examples of the lithium transition metal composite oxide having a spinel crystal structure include Li α Mb β O ４ X γ (Mb is a metal element and a metalloid element other than the lithium element, and is at least one transition metal element. X is at least one element other than the lithium element, Mb, and the oxygen element. 0.90 ≦ α ≦ 1.33, 0 ≦ γ ≦ 1. β is a value determined according to the valences of α, γ, Mb, and X, and 1.5 ≦ β ≦ 2.5.) Mb preferably contains Mn. The content of Mn with respect to Mb (Mn / Mb) is preferably 50 mol% or more, more preferably 80 mol% or more.)

[0045] A polyanion compound is a compound composed of a polyanion (that is, a polyvalent oxoacid ion) and a cation. The polyanion compound preferably contains a lithium cation and a transition metal cation as the cation. Examples of the polyanion compound include Li α Mc β (AO γ ) δ X ε (A is at least one element selected from the group consisting of a boron element, an aluminum element, a silicon element, a phosphorus element, a sulfur element, a chlorine element, a titanium element, a vanadium element, a chromium element, a molybdenum element, and a tungsten element. Mc is a metal element and a metalloid element that is not the lithium element and is not the element selected as A, and is at least one transition metal element. X is at least one element other than the lithium element, Mc, A, and the oxygen element. 0.5 ≦ α ≦ , < β ≦ 2, 2 ≦ γ ≦ 4, ≦ δ ≦ 3, 0 ≦ ε ≦ 1.) Specific examples include, for example, LiFePO ４ LiMnPO ４ LiMn ｘ Fe PO ４ (0 < x < 1), LiNiPO ４ LiCoPO４ Li ３ V ２ (PO ４ ) ３ Li ２ MnSiO ４ Li ２ CoPO ４ F, Li ２ FeP ２ O ７ Li ２ MnP ２ O ７ Li ２ CoP ２ O ７ LiVP ２ O ７ These are some examples. The surface of the polyanionic compound particles may be coated with other materials (for example, carbon materials as described later).

[0046] Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide.

[0047] Examples of sulfur-based materials include elemental sulfur, metal sulfides such as lithium sulfide, organic disulfide compounds, and organic sulfur compounds such as carbon sulfide compounds.

[0048] The atoms or polyanions in these materials, which are the positive electrode active materials, may be partially substituted with atoms or anions of other elements. These materials may also be coated on the surface with other materials.

[0049] A lithium transition metal composite oxide is preferred as the positive electrode active material, and α-NaFeO ２ A lithium transition metal composite oxide having a crystalline structure is more preferred. Furthermore, in the lithium transition metal composite oxide, the nickel content relative to all metal elements other than lithium is preferably 70 mol% or more, more preferably 75 mol% or more, and even more preferably 80 mol% or more. In the lithium transition metal composite oxide, the nickel content relative to all metal elements other than lithium may be 100 mol% or less, 90 mol% or less, or 85 mol% or less.

[0050] Lithium transition metal composite oxides are preferably compounds represented by the following formula (i): Li α Ma β O ２ X γ ... (i) In equation (i), Ma is a metallic element or metalloid other than lithium, and is at least one transition metal element. X is at least one element other than lithium, Ma, and oxygen. 0.9 ≤ α ≤ 1.5 and 0 ≤ γ ≤ 1. β is a value determined by the valencies of α, γ, Ma, and X, and 0.5 ≤ β ≤ 1.5.

[0051] In formula (i), Ma preferably contains at least one of Ni, Co, and Mn, more preferably contains Ni, even more preferably contains Ni, Co, and Mn, and even more preferably is substantially composed of three elements: Ni, Co, and Mn. Ma may also contain other metallic elements. These other metallic elements may be transition metals or typical metallic elements.

[0052] In formula (i), the molar ratio of Ni to Ma (Ni / Ma) may be, for example, 0.5 or more and 1.0 or less, but is preferably 0.7 or more and 0.9 or less, and more preferably 0.75 or more and 0.85 or less.

[0053] In equation (i), the molar ratio of Co to Ma (Co / Ma) may be, for example, 0 or more and 0.3 or less, or 0.05 or more and 0.2 or less.

[0054] In equation (i), the molar ratio of Mn to Ma (Mn / Ma) may be, for example, 0 or more and 0.3 or less, or 0.05 or more and 0.2 or less.

[0055] In formula (i), the molar ratio of the total of Ni, Co, and Mn to Ma ((Ni + Co + Mn) / Ma) is preferably 0.9 or more and 1.0 or less, and more preferably 0.99 or more and 1.00 or less.

[0056] In formula (i), the upper limit of the molar ratio of Li to Ma (Li / Ma), i.e., α / β, is preferably 1.6, and may be more preferably 1.5, 1.4, 1.2, 1.1, or 1.05. The lower limit of the molar ratio (Li / Ma) is preferably 0.95, more preferably 1.0, and may be greater than 1.0.

[0057] By using a lithium transition metal composite oxide with the above composition, the initial irreversible capacity of the positive electrode is increased, and the Q ratio is increased. ＣＸ / Q ＡＸ It becomes easier to enlarge.

[0058] The positive electrode active material is usually in particulate form. The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. Setting the average particle size of the positive electrode active material above the lower limit facilitates the manufacture and handling of the positive electrode active material. Setting the average particle size of the positive electrode active material below the upper limit improves the electronic conductivity of the positive electrode active material layer. When a composite material of the positive electrode active material and other materials is used, the average particle size of the composite material is considered the average particle size of the positive electrode active material. "Average particle size" refers to the value (D50) at which the volume-based integrated distribution, calculated according to JIS-Z-8819-2 (2001), is 50%, based on the particle size distribution measured by laser diffraction / scattering on a dilution of particles diluted with a solvent, in accordance with JIS-Z-8825 (2013). For obtaining particles of the positive electrode active material and the negative electrode active material described later with predetermined particle sizes, known methods using, for example, pulverizers and classifiers can be employed.

[0059] The positive electrode active material preferably contains single-particle system particles. Single-particle system particles refer to particles in which the ratio of the average particle size to the average primary particle size is 3 or less. By using single-particle-diameter particles as the positive electrode active material, the initial irreversible capacity of the positive electrode is increased, and the ratio Q is increased. ＣＸ / Q ＡＸ This makes it easier to increase the size. The content of single-particle systems in the positive electrode active material is preferably 20% by mass or more and 100% by mass or less, and may be 40% by mass or more and 100% by mass or less.

[0060] The "average primary particle diameter" of the positive electrode active material is the average value of the primary particle diameters of any 50 primary particles constituting the positive electrode active material, as observed by a scanning electron microscope (SEM). Primary particles are particles in which no grain boundaries are observed externally in the SEM observation. The primary particle diameter of a primary particle is determined as follows: The shortest diameter passing through the center of the smallest circumscribed circle of the primary particle is defined as the minor diameter, and the diameter passing through the center and perpendicular to the minor diameter is defined as the major diameter. The average value of the major and minor diameters is defined as the particle diameter. If there are two or more shortest diameters, the longest perpendicular diameter is defined as the minor diameter. The "average particle size" of the positive electrode active material is a value obtained by measurement using the laser diffraction / scattering method described above. Furthermore, it has been confirmed that the average particle size based on the above measurements is in close agreement with the average secondary particle diameter, which is the average of the particle diameters of each particle (secondary particle) measured by extracting 50 particles from the SEM image of the particles, avoiding extremely large and extremely small particles. The particle diameter of each particle based on the measurement from this SEM image is determined as follows: The shortest diameter passing through the center of the smallest circumscribed circle of each particle is defined as the minor axis, and the diameter passing through the center and perpendicular to the minor axis is defined as the major axis. The average of the major axis and the minor axis is defined as the particle diameter of each particle. If there are two or more shortest diameters, the longest perpendicular diameter is defined as the minor axis.

[0061] The content of the positive electrode active material in the positive electrode active material layer is preferably 70% by mass or more and 99% by mass or less, and more preferably 70% by mass or more and 98% by mass or less. The lower limit of the content of the positive electrode active material in the positive electrode active material layer may be 80% by mass, or 90%, 95%, or 97% by mass. By setting the content of the positive electrode active material within the above range, it is possible to achieve both high energy density and manufacturability in the positive electrode active material layer.

[0062] Conductive agents are typically components made of conductive materials. Even if the volume resistivity of a conductive agent cannot be directly measured, the volume resistivity is 10 －２Materials whose conductivity is known to be Ω·cm or less are classified as conductive agents. Examples of conductive agents include carbon materials, metals, and conductive ceramics. A carbon material is a material whose main constituent element is carbon. The main constituent element is the element with the highest mass content. For example, the carbon content in a carbon material may be 80% by mass or more, 90% by mass or more, 95% by mass, 99% by mass, or 99.9% by mass or more. It is preferable that the carbon material is a carbon material other than a non-carbonized polymer compound. Examples of carbon materials include graphite, non-graphitic carbon, and graphene-based carbon. Examples of non-graphitic carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black. Examples of carbon black include furnace black, acetylene black, and Ketjen black. Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), and fullerene. Conductive agents can take the form of powder or fibers. One or more types of conductive agents can be used. These materials may also be used as a composite of conductive agents. For example, a composite material of carbon black and CNTs may be used.

[0063] As the conductive agent, carbon materials are preferred, more preferably at least one of carbon black and CNTs is used, and even more preferably both carbon black and CNTs are used.

[0064] The content of the conductive agent in the positive electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, more preferably 1.0% by mass or more and 9% by mass or less, and even more preferably 1.2% by mass or more and 8% by mass or less. The upper limit of the conductive agent content may be 5% by mass, 4% by mass, 3% by mass, or 2% by mass. By setting the conductive agent content within the above range, it is possible to increase the energy density of the non-aqueous electrolyte energy storage element. The technology disclosed herein can also be implemented in a form in which the positive electrode active material layer does not contain a conductive agent.

[0065] Examples of binders include water-based binders and organic solvent-based binders.

[0066] A water-based binder is a binder that dissolves or disperses in water. A water-based binder may be one in mass or more that dissolves or disperses in 100 parts by mass of water at 20°C. When forming a positive electrode active material layer using a positive electrode mixture paste in which the dispersion medium is water or a mixed solvent mainly composed of water, a water-based binder (a water-soluble or water-dispersible polymer material) can be used. Examples of water-based binders include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polytetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene, nitrile-butadiene rubber, and cellulose.

[0067] An organic solvent-based binder is a binder that dissolves or disperses in an organic solvent (e.g., N-methylpyrrolidone). An organic solvent-based binder may be a binder that dissolves or disperses at 1 part by mass or more per 100 parts by mass of an organic solvent (e.g., N-methylpyrrolidone) at 20°C. When forming a positive electrode active material layer using a positive electrode mixture paste in which the dispersion medium is an organic solvent or a mixed solvent mainly composed of an organic solvent, an organic solvent-based binder (a polymer material having solubility or dispersibility in an organic solvent) can be used. Examples of organic solvent-based binders include polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of ethylene and vinyl alcohol, polyacrylonitrile, polyphosphazene, polysiloxane, polyvinyl acetate, polymethyl methacrylate, polystyrene, polycarbonate, polyamide, polyimide, polyamideimide, crosslinked polymers of cellulose and chitosan pyrrolidone carboxylate, and derivatives of chitosan.

[0068] The binder may be a fluororesin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), a polyolefin (polyethylene, polypropylene, etc.), an elastomer (ethylene propylene diene rubber, styrene butadiene rubber, fluororubber, etc.), a polysaccharide polymer (cellulose, chitosan derivatives, etc.), etc. One or more types of binders may be used.

[0069] The binder content in the positive electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 9% by mass or less, and even more preferably 0.8% by mass or more and 8% by mass or less. The upper limit of the binder content may be 5% by mass, 4% by mass, 3% by mass, or 2% by mass. By setting the binder content within the above range, the positive electrode active material can be stably maintained. The technology disclosed herein can also be implemented in a form in which the positive electrode active material layer does not contain a binder.

[0070] Examples of thickening agents include polysaccharide polymers such as carboxymethylcellulose and methylcellulose. If the thickening agent has a functional group that reacts with lithium, etc., this functional group may be deactivated beforehand by methylation or the like. The thickening agent may also function as a binder. One or more types of thickening agents can be used. When the positive electrode active material layer contains a thickening agent, the content of the thickening agent in the positive electrode active material layer is preferably 0.1% by mass or more and 8% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and even more preferably 1% by mass or less. The technology disclosed herein can also be carried out in a form in which the positive electrode active material layer does not contain a thickening agent.

[0071] The filler is not particularly limited. The filler may be a component other than the positive electrode active material, conductive agent, binder, and thickener, and may be a component that is intentionally included. The filler may be included as a component that fills gaps in the positive electrode active material layer, or it may be included for other purposes. The filler may be an organic substance such as a polyolefin, or an inorganic substance such as an inorganic oxide, hydroxide, or carbonate. One or more types of fillers may be used. When the positive electrode active material layer contains a filler, the filler content in the positive electrode active material layer can be 0.1% by mass or more and 8% by mass or less, usually preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. The technology disclosed herein can also be carried out in a form in which the positive electrode active material layer does not contain a filler.

[0072] The positive electrode active material layer may further contain other components besides the positive electrode active material, conductive agent, binder, thickener, and filler. These other components may include those unintentionally present in the positive electrode active material layer. Furthermore, the positive electrode active material layer may contain impurities unintentionally present as these other components, insofar as they achieve the effects of the present invention. The upper limit of the content of these other components in the positive electrode active material layer may be 10% by mass, or 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present components in the positive electrode active material layer may be 10% by mass, or 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present impurities in the positive electrode active material layer may be 10% by mass, or 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0073] For example, a lower limit for the mass per unit area in one positive electrode active material layer is 3 mg / cm². ２ Preferably, 6 mg / cm ２ More preferably, 10 mg / cm² ２ This is even more preferable. The upper limit for the mass per unit area in one positive electrode active material layer is 50 mg / cm². ２ Preferably, 30 mg / cm³ ２ More preferably, 20 mg / cm² ２ That is even more preferable.

[0074] The porosity of the positive electrode active material layer may be, for example, 20% or more and 50% or less. The lower limit of the porosity of the positive electrode active material layer may be 25%, 30%, or 35%. The upper limit of the porosity of the positive electrode active material layer may be 45%, 40%, or 35%. The "porosity (%)" of the positive electrode active material layer and the negative electrode active material layer described later is calculated by taking the apparent volume (volume including voids) of the positive (negative) electrode active material layer as V １ Let V be the sum of the actual volumes of each material constituting the positive (negative) electrode active material layer. ２ In that case, (1-V ２ / V １ It is calculated using the formula ) × 100. V is the sum of the actual volumes of each material constituting the positive (negative) electrode active material layer. ２This can be calculated from the content of each material in the positive (negative) electrode active material layer and the true density of each material.

[0075] (Method for Manufacturing a Positive Electrode) A positive electrode can be manufactured by known methods. A positive electrode can be manufactured, for example, by applying a paste-like positive electrode mixture (positive electrode mixture paste) directly to a positive electrode substrate or via an intermediate layer, and drying it to form a positive electrode active material layer. The positive electrode mixture paste usually contains a positive electrode active material, other optional components, and a dispersion medium. After drying, the positive electrode active material layer may be pressed or otherwise subjected to other processes.

[0076] (Negative electrode) The negative electrode comprises a negative electrode substrate and a negative electrode active material layer laminated directly to the negative electrode substrate or via an intermediate layer. Typically, the negative electrode has a portion where the negative electrode substrate is exposed. This exposed portion of the negative electrode substrate is usually connected to the negative electrode lead described above. The negative electrode may have a shape such as a sheet, plate, or strip.

[0077] The thickness of the negative electrode is set appropriately according to the application of the non-aqueous electrolyte energy storage element. The average thickness of the negative electrode may be, for example, 3 μm or more and 1,000 μm or less. The lower limit of the average thickness of the negative electrode may be 4 μm, 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the negative electrode may be 500 μm, 400 μm, 300 μm, 250 μm, 200 μm, 150 μm, 100 μm, or 50 μm. The average thickness of the negative electrode is the average thickness of the portion in which the negative electrode active material layer is laminated directly to the negative electrode substrate or via an intermediate layer. If there are portions in which the negative electrode active material layer is laminated on both sides of the negative electrode substrate and portions in which the negative electrode active material layer is laminated on only one side of the negative electrode substrate, then the average thickness of the portion in which the negative electrode active material layer is laminated on both sides of the negative electrode substrate shall be used.

[0078] The negative electrode substrate is electrically conductive. Examples of materials for the negative electrode substrate include metals such as copper, nickel, titanium, iron, and their alloys (such as stainless steel), as well as carbon materials. Among these, copper or copper alloys are preferred.

[0079] The negative electrode substrate has a shape such as a sheet, plate, or strip. Examples of negative electrode substrate forms include foil, vapor-deposited film, mesh, and porous material, with foil being preferred. The negative electrode substrate may also be, for example, copper foil or copper alloy foil.

[0080] The average thickness of the negative electrode substrate may be, for example, 1 μm or more and 35 μm or less. The lower limit of the average thickness of the negative electrode substrate may be 2 μm, 3 μm, 4 μm, 5 μm, or 10 μm. The upper limit of the average thickness of the negative electrode substrate may be 30 μm, 20 μm, 15 μm, 10 μm, or 5 μm.

[0081] The configuration of the negative electrode intermediate layer is not particularly limited; for example, it can be selected from the configurations exemplified for the positive electrode intermediate layer.

[0082] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer optionally contains optional components such as a conductive agent, binder, thickener, and filler. The optional components such as the conductive agent, binder, thickener, and filler can be selected from the materials exemplified above for the positive electrode. The negative electrode active material layer may be formed from a negative electrode mixture containing the negative electrode active material and other optional components. The negative electrode active material layer may be provided on only one side of a negative electrode substrate having a shape such as a sheet, or on both sides.

[0083] The negative electrode active material contains silicon dioxide. Silicon dioxide usually exists as particles. Silicon dioxide is usually SiO₂ ｘ The compound is represented by (0 < x ≤ 2). The lower limit of x is preferably 0.8. The upper limit of x is preferably 1.2. The silicon dioxide particles are silicon (Si) and silicon dioxide (SiO ２ ) may coexist. The average particle size of silicon dioxide is preferably, for example, 0.1 μm or more and 20 μm or less. For the purpose of imparting electronic conductivity, the silicon dioxide particle surface is preferably carbon coated by CVD or the like and used as the negative electrode active material.

[0084] Silicon oxide content C in the negative electrode active material ＳｉＯThe lower limit of the silicon dioxide content (percentage of silicon dioxide in the total negative electrode active material) is preferably 1% by mass, more preferably 2% by mass, even more preferably 3% by mass, and even more preferably 4% by mass. By setting the silicon dioxide content to above the above lower limit, the discharge capacity of the non-aqueous electrolyte energy storage element can be increased. On the other hand, the upper limit of this content may be, for example, 100% by mass, but is preferably 30% by mass, more preferably 15% by mass, and even more preferably 10% by mass, 8% by mass, or 6% by mass. By setting the silicon dioxide content to below the above upper limit, the capacity retention rate in the charge-discharge cycle of the non-aqueous electrolyte energy storage element can be further increased.

[0085] The negative electrode active material preferably further contains a carbon-based active material. Examples of carbon-based active materials include graphite and non-graphitic carbon. The mass content of the carbon element in the carbon-based active material may be 80% by mass or more, 90% by mass or more, 95% by mass, 99% by mass, or 99.9% by mass or more.

[0086] "Non-graphite carbon" refers to the average lattice plane spacing (d) of the (002) plane, which is determined by X-ray diffraction before charging / discharging or during the discharge state. ００２ ) refers to carbon materials with a nautical index of 0.34 nm or more and 0.42 nm or less. Non-graphitic carbons include poorly graphitizable carbons and easily graphitizable carbons. "Potentially graphitizable carbon" refers to the above d ００２ This refers to carbon materials with a wavelength of 0.36 nm or more and 0.42 nm or less. "Easily graphitizable carbon" refers to the above d ００２ This refers to carbon materials with a nautical radius of 0.34 nm or more and less than 0.36 nm.

[0087] As the carbon-based active material, graphite is preferred, and artificial graphite is more preferred. By using such a carbon-based active material together with silicon dioxide, the initial irreversible capacity of the negative electrode is reduced, and the specific Q is lowered. ＣＸ / Q ＡＸ This makes it easier to increase the size. The graphite may have its surface coated with other materials such as non-graphite carbon. The average particle size of the graphite can be, for example, 1 μm or more and 100 μm or less.

[0088] The lower limit of the carbon-based active material content in the negative electrode active material may be, for example, 1% by mass, but 70% by mass is preferred, 85% by mass is more preferred, and 92% by mass is even more preferred. By setting the carbon-based active material content to be above the above lower limit, the capacity retention rate in the charge-discharge cycle of the non-aqueous electrolyte energy storage element can be further increased. On the other hand, the upper limit of this content is preferably 99% by mass, more preferably 98% by mass, and even more preferably 96% by mass. By setting the carbon-based active material content to be below the above upper limit, the discharge capacity of the non-aqueous electrolyte energy storage element can be increased.

[0089] When the negative electrode active material contains silicon dioxide and a carbon-based active material, the lower limit of the silicon dioxide content relative to the total content of silicon dioxide and carbon-based active material is preferably 1% by mass, more preferably 2% by mass, even more preferably 3% by mass, and even more preferably 4% by mass. By setting the silicon dioxide content above the above lower limit, the discharge capacity of the non-aqueous electrolyte energy storage element can be increased. On the other hand, the upper limit of this content may be, for example, 99% by mass, but is preferably 30% by mass, more preferably 15% by mass, and even more preferably 8% by mass. By setting the silicon dioxide content below the above upper limit, the capacity retention rate in the charge-discharge cycle of the non-aqueous electrolyte energy storage element can be further increased.

[0090] The negative electrode active material may further contain known negative electrode active materials commonly used in lithium-ion secondary batteries, etc., other than silicon dioxide and carbon-based active materials. However, the lower limit of the total content of silicon dioxide and carbon-based active materials relative to the negative electrode active material is preferably 90% by mass, and more preferably 99% by mass. On the other hand, the upper limit of this total content may be 100% by mass. Thus, by using only silicon dioxide, or only silicon dioxide and carbon-based active materials, as the negative electrode active material, the effects of the present invention are more fully realized.

[0091] The content of the negative electrode active material in the negative electrode active material layer is preferably, for example, 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. The lower limit of the content of the negative electrode active material in the negative electrode active material layer may be 95% by mass, 96% by mass or 97% by mass. 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 in the negative electrode active material layer.

[0092] When the negative electrode active material layer contains a conductive agent, the content of the conductive agent in the negative electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. The content of the conductive agent in the negative electrode active material layer may be 5% by mass or less, 2% by mass or less, or 1% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a conductive agent.

[0093] When the negative electrode active material layer contains a binder, the binder content in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. The binder content in the negative electrode active material layer may be 5% by mass or less, or 2% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a binder.

[0094] When the negative electrode active material layer contains a thickening agent, the content of the thickening agent in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. The content of the thickening agent in the negative electrode active material layer may be 5% by mass or less, 2% by mass or less, or 1% by mass or less. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a thickening agent.

[0095] The filler in the negative electrode active material layer is a component other than the negative electrode active material, conductive agent, binder, and thickener, and may be a component that is intentionally included. The filler may be included as a component that fills gaps in the negative electrode active material layer, or it may be included for other purposes. When the negative electrode active material layer contains a filler, the filler content in the negative electrode active material layer can be 0.1% by mass or more and 8% by mass or less, usually 5% by mass or less is preferred, 2% by mass or less is more preferred, and 1% by mass or less is even more preferred. The technology disclosed herein can also be carried out in a form in which the negative electrode active material layer does not contain a filler.

[0096] The negative electrode active material layer may further contain other components besides the negative electrode active material, conductive agent, binder, thickener, and filler. These other components may include those unintentionally present in the negative electrode active material layer. Furthermore, the negative electrode active material layer may contain impurities unintentionally present as these other components, insofar as they achieve the effects of the present invention. The upper limit of the content of these other components in the negative electrode active material layer may be 10% by mass, or 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present components in the negative electrode active material layer may be 10% by mass, or 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of unintentionally present impurities in the negative electrode active material layer may be 10% by mass, or 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0097] The lower limit of the mass per unit area in one negative electrode active material layer is 2 mg / cm². ２ Therefore, 5 mg / cm ２ Preferably, 7 mg / cm ２ This is more preferable. By having the mass per unit area of ​​one negative electrode active material layer be greater than or equal to the above lower limit, the discharge capacity of the non-aqueous electrolyte energy storage element can be increased. The upper limit for the mass per unit area of ​​one negative electrode active material layer is 30 mg / cm². ２ Preferably, 20 mg / cm³ ２ More preferably, 10 mg / cm² ２ That is even more preferable.

[0098] The porosity of the negative electrode active material layer may be, for example, 30% to 70%. The lower limit of the porosity of the negative electrode active material layer may be 35%, 40%, or 45%. The upper limit of the porosity of the negative electrode active material layer may be 60%, 50%, or 40%.

[0099] (Method for Manufacturing the Negative Electrode) The negative electrode can be manufactured by known methods. The negative electrode can be manufactured, for example, in the same way as the method for manufacturing the positive electrode described above, by applying a paste-like negative electrode mixture (negative electrode mixture paste) directly to the negative electrode substrate or via an intermediate layer, and drying it to form a negative electrode active material layer. After drying, the negative electrode active material layer may be pressed or otherwise subjected to the process. If the negative electrode active material is a metal such as metallic lithium, it can also be manufactured by laminating metal foil directly to the negative electrode substrate or via an intermediate layer, and then pressing it (e.g., roll rolling).

[0100] (ratio Q ＣＸ / Q ＡＸ ) In a non-aqueous electrolyte energy storage element according to one embodiment of the present invention, the initial irreversible capacity Q per unit area of ​​the negative electrode ＡＸ The initial irreversible capacitance Q per unit area of ​​the positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸ The lower limit is 1.5, and may also be 1.51 or 1.52. ＣＸ / Q ＡＸ When the ratio Q is above the lower limit mentioned above, the negative electrode potential in the discharge state becomes lower, suppressing the effects of silicon oxide in the charge-discharge cycle, resulting in a higher capacity retention rate during the charge-discharge cycle. ＣＸ / Q ＡＸ The upper limit may be, for example, 2.0, or it may be 1.8, 1.6, or 1.55.

[0101] Ratio Q ＣＸ / Q ＡＸ One method for adjusting it to 1.5 or higher is to adjust the initial irreversible capacitance Q per unit area of ​​the positive electrode. ＣＸ To increase the initial irreversible capacity Q per unit area of ​​the negative electrode ＡＸ One possible method is to combine appropriately reducing the size of the object.

[0102] Initial irreversible capacitance Q per unit area of ​​the positive electrode ＣＸ Methods to increase the initial irreversible capacity Q per unit area of ​​the positive electrode include, as mentioned above, using a lithium transition metal composite oxide as the positive electrode active material and increasing the nickel content in the lithium transition metal composite oxide, and using single-particle systems as the positive electrode active material, as well as using a positive electrode active material with a larger particle size and using a lithium-rich active material. A lithium-rich active material refers to a lithium transition metal composite compound represented by the above formula (i) where 1.0 < α / β. Furthermore, even if the mass of the positive electrode active material per unit area in one positive electrode active material layer is increased, the initial irreversible capacity Q per unit area of ​​the positive electrode can also be increased. ＣＸ It gets bigger.

[0103] Initial irreversible capacity Q per unit area of ​​the negative electrode ＡＸ Methods to reduce the initial irreversible capacity Q include, as mentioned above, using a carbon-based active material in combination with silicon oxide as the negative electrode active material, pre-doping the negative electrode active material with lithium, and reducing the specific surface area of ​​the negative electrode active material layer. Furthermore, even if the mass of the negative electrode active material per unit area in one negative electrode active material layer is reduced, the initial irreversible capacity Q per unit area of ​​the negative electrode can also be reduced. ＡＸ It becomes smaller.

[0104] In addition, the specific Q can also be adjusted by adjusting the composition of the non-aqueous electrolyte (for example, by adjusting the additives described later). ＣＸ / Q ＡＸ It can be adjusted.

[0105] (Charge S) In the non-aqueous electrolyte energy storage element according to one embodiment of the present invention, the lower limit of the charge S of the negative electrode in the discharge state of the non-aqueous electrolyte energy storage element per 1% by mass of silicon oxide content in the negative electrode active material is 0.7 [% / mass%], and preferably 0.8 [% / mass%].

[0106] The above charge level S is a value defined by the following formula (1): S = {[(Q ＣＸ - Q ＡＸ ) / Q ＡＹ ] × 100} / C ＳｉＯ ...(1) (In formula (1), Q ＣＸThis is the initial irreversible capacity (μAh / cm²) per unit area of ​​the above positive electrode. ２ ) and Q ＡＸ This is the initial irreversible capacity (μAh / cm²) per unit area of ​​the negative electrode. ２ ) and Q ＡＹ This is the initial discharge capacity per unit area of ​​the negative electrode (μAh / cm²). ２ ) and C ＳｉＯ This represents the silicon dioxide content (mass%) in the above-mentioned negative electrode active material.

[0107] The fact that the charge rate S of the negative electrode in the discharge state of a non-aqueous electrolyte energy storage element is 0.7 [% / mass%] or higher per 1 mass% of silicon dioxide content in the negative electrode active material means, for example, that if the silicon dioxide content in the negative electrode active material is 1 mass%, the charge rate of the negative electrode in the discharge state of the non-aqueous electrolyte energy storage element is 0.7% or higher, and for example, if the silicon dioxide content in the negative electrode active material is 10 mass%, the charge rate of the negative electrode in the discharge state of the non-aqueous electrolyte energy storage element is 7% or higher. By having the charge rate S of the negative electrode in the discharge state of a non-aqueous electrolyte energy storage element per 1 mass% of silicon dioxide content in the negative electrode active material be above the above lower limit, the degree of contraction of silicon dioxide in the discharge state is suppressed, and the capacity retention rate in the charge-discharge cycle can be increased. The upper limit of the charge rate S is preferably, for example, 2.0 [% / mass%], but may also be 1.5 [% / mass%], 1.2 [% / mass%], or 1.0 [% / mass%].

[0108] A method for achieving a charge rate S of the negative electrode in the discharge state of a non-aqueous electrolyte energy storage element of 0.7 [% / mass%] or more per 1% by mass of silicon dioxide content in the negative electrode active material is the ratio Q described above. ＣＸ / Q ＡＸ This can be achieved by adjusting the silicon dioxide content in the negative electrode active material after setting the ratio to 1.5 or higher.

[0109] (Initial charge capacity ratio R) The upper limit of the initial charge capacity ratio R between the positive electrode and the negative electrode in the non-aqueous electrolyte energy storage element according to one embodiment of the present invention is preferably 1.10, more preferably 1.00, and even more preferably 0.95.

[0110] The initial charge capacity ratio R mentioned above is a value defined by the following formula (2): R = (Q ＣＸ +Q ＣＹ ) / (Q ＡＸ +Q ＡＹ ) ...(2) (In formula (2), Q ＡＸ Q ＣＸ and Q ＡＹ This is equivalent to equation (1). Q ＣＹ This is the initial discharge capacity per unit area of ​​the above positive electrode (μAh / cm²). ２ )

[0111] When the initial charge capacity ratio R is less than or equal to the upper limit, the initial charge capacity of the negative electrode is sufficiently large relative to the initial charge capacity of the positive electrode, making it less likely for metallic lithium or the like to be deposited on the negative electrode surface, thereby improving charge and discharge performance. The lower limit of the initial charge capacity ratio R is preferably 0.70, more preferably 0.80, and even more preferably 0.85.

[0112] The initial charge capacity ratio R can be adjusted by the mass per unit area of ​​one positive electrode active material layer, the mass per unit area of ​​one negative electrode active material layer, the content of positive electrode active material in the positive electrode active material layer, the content of negative electrode active material in the negative electrode active material layer, and so on.

[0113] (Separator) A known separator can be used. Examples of separators include a separator consisting only of a substrate layer, or a separator in which an inorganic layer containing inorganic particles and a binder is formed on one or both sides of the substrate layer.

[0114] Examples of the substrate layer form of the separator include woven fabric, nonwoven fabric, and porous resin film. Among these forms, porous resin film is preferred from the viewpoint of strength, and nonwoven fabric is preferred from the viewpoint of liquid retention of non-aqueous electrolytes. The material of the substrate layer of the separator is not particularly limited as long as it has insulating properties, but resins such as polyolefins (polyethylene, polypropylene, etc.), polyimide, and aramid are preferred.

[0115] Examples of inorganic compounds constituting the inorganic particles include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, and magnesium oxide; 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, barium fluoride, and barium titanate; covalent crystals such as silicon; mineral resource-derived materials such as talc, zeolite, kaolin, bentonite, and mica, or their artificial counterparts. One or more types of inorganic particles can be used. The average particle size of the inorganic particles is preferably, for example, 0.5 μm to 10 μm. The inorganic particle content in the inorganic layer is preferably 50% to 99% by mass, and more preferably 80% to 98% by mass.

[0116] Examples of binders used in the inorganic layer include those similar to those exemplified in the positive electrode active material layer.

[0117] The porosity of the separator may be, for example, 20% or more and 80% or less. The lower limit of the separator's porosity may be 30%, 40%, or 50% from the viewpoint of discharge performance, etc. The upper limit of the separator's porosity may be 70%, 60%, or 50% from the viewpoint of strength, etc. In this specification, "porosity" refers to a volume-based value and means a measurement value obtained using a mercury porosimeter.

[0118] The average thickness of the separator may be, for example, 10 μm or more and 40 μm or less, or 15 μm or more and 30 μm or less.

[0119] A polymer gel composed of a polymer and a non-aqueous electrolyte may be used as a separator. A polymer gel may also be used in combination with a porous resin film, nonwoven fabric, etc., as described above, as a separator.

[0120] (Electrode Body) As the electrode body, known structures such as wound electrode bodies and laminated electrode bodies can be used.

[0121] A wound electrode has a structure in which the positive electrode and negative electrode are wound together while being insulated. The wound electrode may be cylindrical or flattened. The electrode 2 of the non-aqueous electrolyte energy storage element 1 in Figure 2 is a flattened wound electrode. A wound electrode can be manufactured, for example, by the following procedure. First, a laminate is obtained by stacking a positive electrode, a separator, and a negative electrode, each formed in a strip shape, in that order. A wound electrode is obtained by winding this laminate.

[0122] A laminated electrode body has a structure in which one or more positive electrodes and one or more negative electrodes are stacked in an insulated state. For example, a laminated electrode body can be obtained by stacking rectangular positive electrodes, separators, and negative electrodes in this order.

[0123] Other electrode structures can also be used, such as those in which at least one of the positive and negative electrodes is folded in a bellows-like manner and stacked.

[0124] (Non-aqueous electrolyte) Known non-aqueous electrolytes can be used as the non-aqueous electrolyte. A non-aqueous electrolyte is a medium that is responsible for transporting charge transport ions (e.g., lithium ions) between the positive electrode and the negative electrode, and which is substantially free of water. The water content in the non-aqueous electrolyte may be, for example, 10,000 ppm or less, 5,000 ppm or less, 1,000 ppm or less, 500 ppm or less, 100 ppm or less, preferably 50 ppm or less, and more preferably 20 ppm or less. Examples of non-aqueous electrolytes include non-aqueous electrolyte solutions and solid electrolytes. Non-aqueous electrolyte solutions and solid electrolytes may be used in combination. In one embodiment of the present invention, the non-aqueous electrolyte may be a non-aqueous electrolyte solution. That is, only a non-aqueous electrolyte solution may be used as the non-aqueous electrolyte. Furthermore, the non-aqueous electrolyte energy storage element may be a non-aqueous electrolyte energy storage element or a non-aqueous electrolyte secondary battery.

[0125] (Non-aqueous electrolyte) A non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in this non-aqueous solvent.

[0126] Any known non-aqueous solvent can be used. Examples of non-aqueous solvents include carbonates, esters, ethers, amides, and nitriles. Examples of carbonates include cyclic carbonates and linear carbonates. Examples of esters include carboxylic acid esters, phosphate esters, and sulfonic acid esters. As non-aqueous solvents, compounds in which some of the hydrogen atoms contained in these compounds are substituted with halogen atoms may also be used. One or more non-aqueous solvents can be used.

[0127] A cyclic carbonate is a carbonate having a ring structure containing a carbonate group (-O-C(=O)-O-). Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, chloroethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, styrene carbonate, 1-phenylvinylene carbonate, and 1,2-diphenylvinylene carbonate. A cyclic carbonate may be a saturated cyclic carbonate such as ethylene carbonate, or an unsaturated cyclic carbonate such as vinylene carbonate. "Saturated" means not having carbon-carbon unsaturated bonds (carbon-carbon double bonds and carbon-carbon triple bonds). "Unsaturated" means having carbon-carbon unsaturated bonds. As the cyclic carbonate, saturated cyclic carbonates are preferred, and ethylene carbonates are more preferred.

[0128] A chain-like carbonate refers to a carbonate that does not have a ring structure containing a carbonate group. Examples of chain-like carbonates include diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, diphenyl carbonate, trifluoroethyl methyl carbonate, and bis(trifluoroethyl) carbonate. The chain-like carbonate may be a saturated chain-like carbonate such as dimethyl carbonate, or an unsaturated chain-like carbonate such as diphenyl carbonate. A saturated chain-like carbonate is preferred as the chain-like carbonate, and ethyl methyl carbonate is more preferred.

[0129] The non-aqueous solvent preferably contains carbonate, and more preferably contains both cyclic carbonate and linear carbonate. The carbonate content in the non-aqueous solvent is preferably 80% to 100% by volume, may be 99% to 100% by volume, or 100% by volume. Using cyclic carbonate can promote the dissociation of the electrolyte salt and increase the ionic conductivity of the non-aqueous electrolyte. Using linear carbonate can keep the viscosity of the non-aqueous electrolyte low. When using both cyclic carbonate and linear carbonate, the volume ratio of cyclic carbonate to linear carbonate (cyclic carbonate: linear carbonate) is preferably in the range of 5:95 to 50:50.

[0130] An electrolyte salt is an ionic compound in which the cation is a charge transport ion and which is solid at room temperature (20°C) at 1 atmosphere. Known electrolyte salts can be used. Examples of electrolyte salts include lithium salts, sodium salts, potassium salts, magnesium salts, and onium salts. Among these, lithium salts are preferred. One or more electrolyte salts can be used.

[0131] LiPF is an example of a lithium salt. ６ LiPO ２ F ２ LiBF ４ LiClO ４ Inorganic lithium salts such as LiN(SO4) ２ F) ２ , LiN (SO ２ CF ３ ) ２ , LiN (SO ２ C ２ F ５ ) ２ , LiN (SO ２ CF ３ ) (SO ２ C ４ F ９ ) and other imide salts, LiB(C ２ O ４ ) ２ LiBF ２ (C ２ O ４ ), LiPF２ (C ２ O ４ ) ２ Examples include lithium oxalate salts such as LiN(SO4). ２ F) ２ This also applies to inorganic lithium salts. Among these, inorganic lithium salts are preferred, and LiPF ６ This is more preferable. In some cases, an imide salt may also be preferable.

[0132] The electrolyte salt content in the non-aqueous electrolyte is 0.1 mol / dm³ at 20°C and 1 atm. ３ 2.5mol / dm or more ３ The following is preferred: 0.3 mol / dm ３ 2.0mol / dm or more ３ The following is more preferable: 0.5 mol / dm ３ More than 1.7mol / dm ３ The following is even more preferable: 0.7 mol / dm ３ 1.5mol / dm or more ３ The following is particularly preferable. By setting the electrolyte salt content within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

[0133] The non-aqueous electrolyte may contain additives in addition to the non-aqueous solvent and electrolyte salt. One or more types of additives may be used. When additives are used in the non-aqueous electrolyte, the additive content in the non-aqueous electrolyte is preferably 0.01% to 10% by mass, more preferably 0.1% to 7% by mass, even more preferably 0.2% to 5% by mass, and particularly preferably 0.3% to 3% by mass. By adjusting the type and content of the additives, the initial irreversible capacity Q per unit area of ​​the negative electrode of the non-aqueous electrolyte energy storage element can be adjusted. ＡＸ The initial irreversible capacitance Q per unit area of ​​the positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸ It can be adjusted.

[0134] (Solid Electrolyte) The solid electrolyte can be selected from any material that has ionic conductivity, such as lithium, sodium, and calcium, and is solid at room temperature (20°C). Examples of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, halide solid electrolytes, and polymer solid electrolytes. One or more types of solid electrolytes can be used.

[0135] (Container) The container houses the electrode body and non-aqueous electrolyte in its internal space. The container material can be a metal material such as aluminum or stainless steel, or a resin material, with metal materials being preferred from the viewpoint of strength, etc. A composite material of metal and resin materials can also be used.

[0136] The shape of the container is not particularly limited, but it can be cylindrical, rectangular (square), disc-shaped, etc. The container may also be in the form of a sheet or other shape formed from a metal-resin composite film.

[0137] (Shape and application of non-aqueous electrolyte energy storage element) The shape of the non-aqueous electrolyte energy storage element according to one embodiment of the present invention is not particularly limited. The non-aqueous electrolyte energy storage element may be, for example, a cylindrical battery, a prismatic battery, a flat battery, a coin cell battery, a button cell battery, etc.

[0138] The applications of the non-aqueous electrolyte energy storage element according to one embodiment of the present invention are not particularly limited. The non-aqueous electrolyte energy storage element can be used, for example, as a power source for automobiles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, as a power source for electronic devices such as personal computers and communication terminals, and as a power storage power source.

[0139] The non-aqueous electrolyte energy storage element of the present invention can be used individually or in combination. The non-aqueous electrolyte energy storage element may be used individually when the required output and voltage are small. On the other hand, when at least one of the required output and voltage is large, the non-aqueous electrolyte energy storage element may be used as part of an energy storage device combined with other non-aqueous electrolyte energy storage elements. In an energy storage device composed of multiple non-aqueous electrolyte energy storage elements, at least one of the non-aqueous electrolyte energy storage elements included in the energy storage device may be a non-aqueous electrolyte energy storage element according to one embodiment of the present invention. The energy storage device will be described in detail later.

[0140] In the non-aqueous electrolyte energy storage element according to one embodiment of the present invention, the container may be restrained to maintain a certain thickness, or it may not be restrained in such a way. Alternatively, the container may be restrained to have a certain load applied to it. When the container is restrained, expansion of the container due to charge-discharge cycles, etc., may be suppressed, and a decrease in charge-discharge performance may be suppressed. When the container is restrained, the electrode body inside the container may or may not have a load applied to it. For example, the non-aqueous electrolyte energy storage element or energy storage device may be provided with a restraining member that performs such restraint.

[0141] <Method for Manufacturing a Non-Aqueous Electrolyte Energy Storage Element> A non-aqueous electrolyte energy storage element according to one embodiment of the present invention can be manufactured by a known method. The method for manufacturing the non-aqueous electrolyte energy storage element includes, for example, preparing a positive electrode, preparing a negative electrode, preparing a non-aqueous electrolyte, and housing the positive electrode, negative electrode, and non-aqueous electrolyte in a container. The manufacturing method may also include preparing a separator, and manufacturing an electrode body using the positive electrode, negative electrode, and separator. Housing the positive electrode, negative electrode, and non-aqueous electrolyte in a container may be equivalent to housing the electrode body and non-aqueous electrolyte in a container.

[0142] Preparing the positive electrode may also mean manufacturing the positive electrode. The positive electrode can be manufactured by the method described above. Preparing the negative electrode may also mean manufacturing the negative electrode. The negative electrode can be manufactured by the method described above. Preparing the non-aqueous electrolyte may also mean preparing the non-aqueous electrolyte. The non-aqueous electrolyte can be prepared, for example, by dissolving an electrolyte salt in a non-aqueous solvent. The positive electrode, negative electrode, separator, non-aqueous electrolyte, etc., may be prepared by purchase or other means.

[0143] The electrode bodies (or positive and negative electrodes) and the non-aqueous electrolyte can be housed in a container by known methods. If the non-aqueous electrolyte is a non-aqueous electrolyte solution, for example, the electrode bodies (or positive and negative electrodes) can be housed in the container first, and then the non-aqueous electrolyte solution can be injected through an inlet provided in the container. The inlet can be sealed after the non-aqueous electrolyte solution has been injected.

[0144] The method for manufacturing the non-aqueous electrolyte energy storage element may further include initial charging and discharging of the assembled uncharged / discharged energy storage element. In this initial charging and discharging, the initial irreversible capacity Q per unit area of ​​the negative electrode ＡＸ The initial irreversible capacitance Q per unit area of ​​the positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸ The value will be 1.5 or higher.

[0145] <Energy Storage Device> The energy storage device 30 in Figure 3 comprises a plurality of energy storage units 20. Each energy storage unit 20 comprises a plurality of electrically connected non-aqueous electrolyte energy storage elements 1. The energy storage device 30 may also include busbars (not shown) for electrically connecting the plurality of non-aqueous electrolyte energy storage elements 1, busbars (not shown) for electrically connecting the plurality of energy storage units 20, etc. The energy storage unit 20 or the energy storage device 30 may also include a condition monitoring device (not shown) for monitoring the state of one or more non-aqueous electrolyte energy storage elements 1.

[0146] <Other Embodiments> The non-aqueous electrolyte energy storage element of the present invention is not limited to the embodiments described above, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment may be added to the configuration of another embodiment, and a part of the configuration of one embodiment may be replaced with the configuration of another embodiment or with well-known technology. Furthermore, a part of the configuration of one embodiment may be deleted. Also, well-known technology may be added to the configuration of one embodiment.

[0147] In the above embodiment, a case in which a non-aqueous electrolyte energy storage element is used as a rechargeable non-aqueous electrolyte secondary battery was described, but the type, shape, dimensions, capacity, etc. of the non-aqueous electrolyte energy storage element are arbitrary. The present invention can also be applied to various secondary batteries, electric double-layer capacitors, lithium-ion capacitors, and other capacitors.

[0148] In the above embodiment, an electrode body in which a separator is interposed between the positive electrode and the negative electrode was described, but the electrode body does not need to have a separator. For example, the positive electrode and the negative electrode may be in direct contact with each other, with a non-conductive layer formed on the active material layer of either the positive electrode or the negative electrode. Thus, the positive electrode and the negative electrode may further have layers other than the base material, intermediate layer, and active material layer. Furthermore, the positive electrode and the negative electrode do not need to have a layered structure.

[0149] 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.

[0150] [Example 1] (Preparation of positive electrode) As the positive electrode active material, a mixture of single-particle system particles and particles other than single-particle system particles (secondary particles) was prepared using α-NaFeO ２ LiNi is a lithium transition metal composite oxide having a type crystal structure. ０．８ Co ０．１ Mn ０．１ O ２(NCM811) was prepared. In Table 1, single-particle systems are referred to as "single particles," and particles other than single-particle systems (secondary particles) are referred to as "secondary particles." A positive electrode mixture paste was prepared containing the above positive electrode active material, carbon black (CB), and polyvinylidene fluoride (PVDF) in a mass ratio of 97.0:2.0:1.0 (on a solid basis), with N-methylpyrrolidone (NMP) as the dispersion medium. This positive electrode mixture paste was applied to a strip of aluminum foil as the positive electrode substrate and dried to remove the NMP. 1 cm ２ The amount of positive electrode mixture paste applied per unit area (mass per unit area in one positive electrode active material layer) is 15.4 mg / cm² in terms of solid content. ２ This was then compressed using a roller press to form the positive electrode active material layer, and then dried under reduced pressure to obtain the positive electrode. The initial irreversible capacity Q per unit area of ​​the obtained positive electrode was... ＣＸ It is 427 μAh / cm² ２ , initial discharge capacity (initial reversible capacity) Q ＣＹ It is 2990 μAh / cm² ２ It is known that...

[0151] (Fabrication of the negative electrode) A mixture of silicon oxide and a carbon-based active material was prepared as the negative electrode active material. Artificial graphite was used as the carbon-based active material. The silicon oxide content in the negative electrode active material was C ＳｉＯ The amount was set to 5% by mass. A negative electrode mixture paste was prepared containing the above negative electrode active material, styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC) in a mass ratio of 98.0:1.0:1.0 (based on solid content), with water as the dispersion medium. This negative electrode mixture paste was applied to a strip of copper foil as the negative electrode substrate, dried, and the water was removed. 1 cm ２ The amount of negative electrode mixture paste applied per unit area (mass per unit area in one negative electrode active material layer) is 8.93 mg / cm² in terms of solid content. ２ This was then compressed using a roller press to form the negative electrode active material layer, and then dried under reduced pressure to obtain the negative electrode. The initial irreversible capacity Q per unit area of ​​the obtained negative electrode was... ＡＸ It is 271 μAh / cm² ２ , initial discharge capacity (initial reversible capacity) Q ＡＹ It is 3579 μAh / cm² ２It is known that...

[0152] The initial irreversible capacity Q per unit area of ​​the negative electrode obtained in this way ＡＸ The initial irreversible capacitance Q per unit area of ​​the positive electrode ＣＸ Ratio Q ＣＸ / Q ＡＸ The result was 1.57. The charge level S obtained by the above formula (1) was 0.87 as shown in the following formula: S = {[(Q ＣＸ - Q ＡＸ ) / Q ＡＹ ] × 100} / C ＳｉＯ = {[(427-271) / 3579]×100} / 5 ≈ 0.87 Also, the initial charge capacity ratio R obtained from the above formula (2) was 0.89 as shown in the following formula. R = (Q ＣＸ +Q ＣＹ ) / (Q ＡＸ +Q ＡＹ ) = (427 + 2990) / (271 + 3579) ≈ 0.89

[0153] (Preparation of non-aqueous electrolyte) A non-aqueous solvent is prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:35:35, to which lithium hexafluorophosphate (LiPF) is added as the electrolyte salt. ６ ) 1.0 mol / dm ３ A non-aqueous electrolyte was prepared by mixing the components to achieve the specified content.

[0154] (Fabrication of Non-Aqueous Electrolyte Energy Storage Element) A microporous polyolefin membrane with an inorganic layer formed on one side was prepared as a separator. An electrode body was fabricated by stacking the positive electrode and the negative electrode via this separator. The separator was positioned so that the side with the inorganic layer faced the positive electrode. This electrode body was placed in a rectangular container, the non-aqueous electrolyte was injected into it, and then the container was sealed.

[0155] (Initial Charge and Discharge) The obtained non-aqueous electrolyte energy storage element was subjected to three initial charge and discharge cycles at 25°C in the following manner. In the first cycle, constant current and constant voltage charging was performed with a charging current of 0.2C, a charging termination voltage of 4.18V, and a total charging time of 7 hours, followed by a 10-minute pause. Subsequently, constant current discharge was performed with a discharge current of 0.2C and a discharge termination voltage of 2.75V, followed by a 10-minute pause. In the second and third cycles, constant current and constant voltage charging was performed with a charging current of 1C, a charging termination voltage of 4.18V, and a total charging time of 3 hours, followed by a 10-minute pause. Subsequently, constant current discharge was performed with a discharge current of 1C and a discharge termination voltage of 2.75V, followed by a 10-minute pause. The initial charge and discharge was performed by the above procedure. This obtained the non-aqueous electrolyte energy storage element of Example 1. The measured values ​​for the non-aqueous electrolyte energy storage element of Example 1 described above are shown in Table 1.

[0156] [Example 2] As the positive electrode active material, a mixture of single-particle system particles and particles other than single-particle system particles (secondary particles) was used. ２ LiNi is a lithium transition metal composite oxide having a type crystal structure. ０．８ Co ０．１ Mn ０．１ O ２ A non-aqueous electrolyte energy storage element of Example 2 was obtained in the same manner as in Example 1, except that the necessary materials were prepared. The measured values ​​for each of the non-aqueous electrolyte energy storage elements of Example 2 are shown in Table 1.

[0157] [Comparative Example 1] (Preparation of the positive electrode) The positive electrode active material is a single-particle system, α-NaFeO ２ LiNi is a lithium transition metal composite oxide having a type crystal structure. ０．６ Co ０．２ Mn ０．２ O ２ (NCM622) was prepared. A positive electrode mixture paste was prepared containing the above positive electrode active material, CB, and PVDF in a mass ratio of 97.0:2.0:1.0 (on a solid basis), with NMP as the dispersion medium. This positive electrode mixture paste was applied to a strip of aluminum foil as the positive electrode substrate and dried to remove the NMP. 1 cm ２The amount of positive electrode mixture paste applied per unit area (mass per unit area in one positive electrode active material layer) is 17.0 mg / cm² in terms of solid content. ２ This was then compressed using a roller press to form the positive electrode active material layer, and then dried under reduced pressure to obtain the positive electrode. The initial irreversible capacity Q per unit area of ​​the obtained positive electrode was... ＣＸ It is 383 μAh / cm² ２ , initial discharge capacity (initial reversible capacity) Q ＣＹ It is 3036 μAh / cm² ２ It is known that...

[0158] (Fabrication of the negative electrode) A mixture of silicon oxide and a carbon-based active material was prepared as the negative electrode active material. For the carbon-based active material, a mixture of natural graphite and artificial graphite in a mass ratio of 1:1 was used. The silicon oxide content in the negative electrode active material was C ＳｉＯ The amount was set to 5% by mass. A negative electrode mixture paste was prepared containing the above negative electrode active material, SBR, and CMC in a mass ratio of 98.0:1.0:1.0 (based on solid content), with water as the dispersion medium. This negative electrode mixture paste was applied to a strip of copper foil as the negative electrode substrate, dried, and the water was removed. 1 cm ２ The amount of negative electrode mixture paste applied per unit area (mass per unit area in one negative electrode active material layer) is 8.80 mg / cm² in terms of solid content. ２ This was then compressed using a roller press to form the negative electrode active material layer, and then dried under reduced pressure to obtain the negative electrode. The initial irreversible capacity Q per unit area of ​​the obtained negative electrode was... ＡＸ It is 318 μAh / cm² ２ , initial discharge capacity (initial reversible capacity) Q ＡＹ It is 3540 μAh / cm² ２ It is known that...

[0159] (Preparation of non-aqueous electrolyte) A non-aqueous electrolyte was prepared in the same manner as in Example 1.

[0160] (Fabrication of Non-Aqueous Electrolyte Energy Storage Element) A microporous polyolefin membrane with an inorganic layer formed on one side was prepared as a separator. An electrode body was fabricated by stacking the positive electrode and the negative electrode via this separator. The separator was positioned so that the side with the inorganic layer faced the positive electrode. This electrode body was placed in a rectangular container, the non-aqueous electrolyte was injected into it, and then the container was sealed.

[0161] (Initial Charge and Discharge) The obtained non-aqueous electrolyte energy storage element was subjected to three initial charge and discharge cycles at 25°C in the following manner. In the first cycle, constant current and constant voltage charging was performed with a charging current of 0.2C, a charging termination voltage of 4.25V, and a total charging time of 7 hours, followed by a 10-minute rest period. Subsequently, constant current discharge was performed with a discharge current of 0.2C and a discharge termination voltage of 2.75V, followed by a 10-minute rest period. In the second and third cycles, constant current and constant voltage charging was performed with a charging current of 1C, a charging termination voltage of 4.25V, and a total charging time of 3 hours, followed by a 10-minute rest period. Subsequently, constant current discharge was performed with a discharge current of 1C and a discharge termination voltage of 2.75V, followed by a 10-minute rest period. The initial charge and discharge was performed by the above procedure. This obtained the non-aqueous electrolyte energy storage element of Comparative Example 1. The measured values ​​for the non-aqueous electrolyte energy storage element of Comparative Example 1 are shown in Table 1.

[0162] [Comparative Example 2] A mixture of silicon oxide and a carbon-based active material was prepared as the negative electrode active material. Artificial graphite was used as the carbon-based active material. The silicon oxide content in the negative electrode active material was C ＳｉＯ The amount was set to 5% by mass. The above negative electrode active material was used, and 1 cm ２ The amount of negative electrode mixture paste applied per unit area (mass per unit area in one negative electrode active material layer) is 8.93 mg / cm² in terms of solid content. ２ A non-aqueous electrolyte energy storage element of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except for the aforementioned difference. The measured values ​​for each of the non-aqueous electrolyte energy storage elements of Comparative Example 2 are shown in Table 1.

[0163] [Evaluation] (Capacity retention rate in charge-discharge cycles) Charge-discharge cycle tests were performed on each of the non-aqueous electrolyte energy storage elements obtained in the examples and comparative examples in the following manner. Constant current and constant voltage charging was performed in a constant temperature bath at 45°C with a charging current of 1.0C, a charging termination voltage of 4.18V (4.33V for each of the non-aqueous electrolyte energy storage elements in the comparative examples), and a total charging time of 3 hours, followed by a 10-minute rest period. Then, constant current discharge was performed with a discharge current of 1.0C and a discharge termination voltage of 2.75V, followed by a 10-minute rest period. This charge-discharge cycle was performed 1000 times. The capacity retention rate in charge-discharge cycles was calculated as the percentage of the discharge capacity at the 1000th cycle to the discharge capacity at the 1st cycle in this charge-discharge cycle test. The results are shown in Table 1.

[0164]

[0165] As shown in Table 1, ratio Q ＣＸ / Q ＡＸ In each of the non-aqueous electrolyte energy storage elements in Examples 1 and 2, where the ratio was 1.5 or higher and the charge level S was 0.7 [% / mass%] or higher, the capacity retention rate exceeded 90%, indicating a high capacity retention rate during charge-discharge cycles.

[0166] This invention can be applied to non-aqueous electrolyte energy storage elements used as power sources for electronic devices such as personal computers and communication terminals, as well as automobiles and the like.

[0167] 1. Non-aqueous electrolyte energy storage element 2. Electrode body 3. Container 4. Positive electrode lead 5. Positive electrode external terminal 6. Negative electrode lead 7. Negative electrode external terminal 20. Energy storage unit 30. Energy storage device

Claims

1. A non-aqueous electrolyte storage element comprising a positive electrode having a positive electrode active material layer containing a positive electrode active material, and a negative electrode having a negative electrode active material layer containing a negative electrode active material, wherein the negative electrode active material contains silicon oxide, and the mass per unit area in one layer of the negative electrode active material layer is 2 [mg / cm ２ or more, and the ratio Q ＡＸ of the initial irreversible capacity Q ＣＸ per unit area of the positive electrode to the initial irreversible capacity Q ＣＸ / Q ＡＸ of the negative electrode per unit area is 1.5 or more, and the charging rate S of the negative electrode in the discharged state of the non-aqueous electrolyte storage element per 1 mass% of the content of silicon oxide in the negative electrode active material defined by the following formula (1) is 0.7 [% / mass%] or more. A non-aqueous electrolyte storage element., S = {[(Q ＣＸ - Q ＡＸ ) / Q ＡＹ × 100} / C ＳｉＯ ... (1) (In formula (1), Q ＣＸ is the initial irreversible capacity per unit area of the positive electrode (μAh / cm ２ ), Q ＡＸ is the initial irreversible capacity per unit area of the negative electrode (μAh / cm ２ ), Q ＡＹ is the initial discharge capacity per unit area of the negative electrode (μAh / cm ２ ), and C ＳｉＯ is the content of silicon oxide in the negative electrode active material (mass%)).) 2. The non-aqueous electrolyte energy storage element according to claim 1, wherein the negative electrode active material further comprises a carbon-based active material.

3. The non-aqueous electrolyte energy storage element according to claim 2, wherein the positive electrode active material contains a lithium transition metal composite oxide in which the nickel element content relative to all metal elements other than lithium is 70 mol% or more, and the carbon-based active material contains artificial graphite.

4. A non-aqueous electrolyte energy storage element according to claim 1 or claim 2, wherein the initial charge capacity ratio R between the positive electrode and the negative electrode, as defined by the following formula (2), is 1.10 or less. R = (Q ＣＸ +Q ＣＹ ) / (Q ＡＸ +Q ＡＹ ) ...(2) (In formula (2), Q ＡＸ Q ＣＸ and Q ＡＹ This is equivalent to equation (1). Q ＣＹ This is the initial discharge capacity per unit area of ​​the above positive electrode (μAh / cm²). ２ )

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