JP2023102080A - Nonaqueous electrolyte storage element, equipment, and use of nonaqueous electrolyte storage element - Google Patents

Abstract

To provide a nonaqueous electrolyte storage element high in capacity maintenance ratio after a discharge/charge cycle.SOLUTION: A nonaqueous electrolyte storage element comprises: a positive electrode in which a positive electrode potential for a discharge final voltage in ordinary use is less than 3.69 Vvs.Li/Li+ and which contains a lithium transition metal composite oxide including a nickel element; a nonaqueous electrolyte; and a separator in which membrane resistance at 25°C in the state of being impregnated with the nonaqueous electrolyte is 2.5 Ω cm2 or more.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte storage element, an apparatus, and a method of using the non-aqueous electrolyte storage element.

Non-aqueous electrolyte secondary batteries, typified by lithium-ion secondary batteries, are widely used in electronic devices such as personal computers, communication terminals, and automobiles because of their high energy density. A non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring charge transport ions between the electrodes. Capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries.

Lithium-transition metal composite oxides and the like are known as positive electrode active materials for non-aqueous electrolyte storage elements. Patent Literature 1 describes a non-aqueous electrolyte secondary battery in which a nickel-containing lithium transition metal composite oxide represented by Li _1.02 Ni _0.82 Co _0.15 Al _0.03 O ₂ is used as a positive electrode active material.

JP 2017-107827 A

A lithium-transition metal composite oxide containing a nickel element, which is a positive electrode active material, has advantages such as a large discharge capacity. In addition, in order to increase the discharge capacity of the non-aqueous electrolyte storage device, it is conceivable to set the discharge end voltage low so that the charge transport ions such as lithium ions are discharged to the positive electrode active material as much as possible. However, in a non-aqueous electrolyte storage element having a positive electrode containing a lithium-transition metal composite oxide containing nickel, the final discharge voltage is set low, and the positive electrode potential at the end of discharge is 3.69 V vs. When charging/discharging is repeated to reach less than Li/Li ⁺ , the discharge capacity may significantly decrease.

An object of the present invention is to provide a positive electrode containing a lithium-transition metal composite oxide containing nickel element, wherein the positive electrode potential at the discharge end voltage during normal use is 3.69 V vs. An object of the present invention is to provide a non-aqueous electrolyte storage element having a Li/Li ⁺ less than a non-aqueous electrolyte storage element and having a high capacity retention rate after charge-discharge cycles, an apparatus equipped with such a non-aqueous electrolyte storage element, and a method of using such a non-aqueous electrolyte storage element.

In the non-aqueous electrolyte storage element according to one aspect of the present invention, the positive electrode potential at the discharge end voltage during normal use is 3.69 V vs. A positive electrode containing a lithium transition metal composite oxide having a ratio of less than Li/Li ⁺ and containing a nickel element, a non-aqueous electrolyte, and a separator having a membrane resistance at 25° C. of 2.5 Ω·cm or ^more when impregnated with the non-aqueous electrolyte.

A device according to another aspect of the present invention includes a non-aqueous electrolyte storage element and a charge/discharge control device, wherein the non-aqueous electrolyte storage element includes a positive electrode containing a lithium transition metal composite oxide containing nickel, a non-aqueous electrolyte, and a separator having a membrane resistance of 2.5 Ω·cm ² or more at 25°C when impregnated with the non-aqueous electrolyte. It is configured to discharge to less than Li/Li ⁺ .

A method of using a non-aqueous electrolyte storage element according to another aspect of the present invention is such that a positive electrode potential of a non-aqueous electrolyte storage element is 3.69 V vs. 3.69 V vs. a non-aqueous electrolyte storage element including a positive electrode containing a lithium transition metal composite oxide containing nickel, a non-aqueous electrolyte, and a separator having a membrane resistance of 2.5 Ω·cm ² or more at 25° C. when impregnated with the non-aqueous electrolyte. Discharging to less than Li/Li ⁺ is provided.

According to one aspect of the present invention, the positive electrode includes a lithium-transition metal composite oxide containing nickel element, and the positive electrode potential at the discharge end voltage during normal use is 3.69 V vs. It is possible to provide a non-aqueous electrolyte storage element having a ratio of less than Li/Li ⁺ and having a high capacity retention rate after charge-discharge cycles, an apparatus equipped with such a non-aqueous electrolyte storage element, and a method of using such a non-aqueous electrolyte storage element.

FIG. 1 is a see-through perspective view showing an embodiment of a non-aqueous electrolyte storage element. FIG. 2 is a schematic diagram showing an embodiment of a power storage device configured by assembling a plurality of non-aqueous electrolyte power storage elements.

First, an overview of the non-aqueous electrolyte storage element, equipment, and method of using the non-aqueous electrolyte storage element disclosed by the present specification will be described.

In the non-aqueous electrolyte storage element according to one aspect of the present invention, the positive electrode potential at the discharge end voltage during normal use is 3.69 V vs. A positive electrode containing a lithium transition metal composite oxide having a ratio of less than Li/Li ⁺ and containing a nickel element, a non-aqueous electrolyte, and a separator having a membrane resistance at 25° C. of 2.5 Ω·cm or ^more when impregnated with the non-aqueous electrolyte.

The non-aqueous electrolyte storage element includes a positive electrode containing a lithium transition metal composite oxide containing nickel element, and the positive electrode potential at the discharge end voltage during normal use is 3.69 V vs. A non-aqueous electrolyte energy storage device having a ratio of less than Li/Li ⁺ and having a high capacity retention rate after charge-discharge cycles. Although the reason for this is not clear, the following reasons are presumed. Generally, in a non-aqueous electrolyte storage element in which a lithium-transition metal composite oxide containing nickel element is used as a positive electrode active material, the positive electrode potential is 3.69 V vs. When the battery is deeply discharged to less than Li/Li ⁺ , the gaps between the primary particles of the lithium-transition metal composite oxide widen, and the non-aqueous electrolyte penetrates into the secondary particles. As a result, cracking of the secondary particles of the lithium-transition metal composite oxide and growth of a deteriorated layer on the surface of the primary particles are likely to occur, and discharge capacity decreases with charge-discharge cycles. In particular, when a separator impregnated with a non-aqueous electrolyte and having a low membrane resistance at 25° C. is used, the lithium-transition metal composite oxide is more likely to be discharged more deeply. In such a case, the non-aqueous electrolyte solution easily penetrates into the secondary particles, and cracking of the secondary particles and growth of a deteriorated layer on the surface of the primary particles are more likely to occur, resulting in a significant decrease in the capacity retention rate after charge-discharge cycles. On the other hand, according to the non-aqueous electrolyte storage element according to one aspect of the present invention, the positive electrode potential is 3.69 V vs. 3.69 V vs. 3.69 V vs. 3.69 V vs. 3.69 ^V vs. Since the lithium-transition metal composite oxide is suppressed from being discharged too deeply even when discharged to less than Li/Li ⁺ , cracking of the secondary particles is suppressed, and the capacity retention rate after charge-discharge cycles is increased.

“Normal use” refers to the case where the non-aqueous electrolyte storage element is used under the charging/discharging conditions recommended or specified for the non-aqueous electrolyte storage element. The charging/discharging conditions are determined, for example, by the settings of the device using the non-aqueous electrolyte storage element. The “positive electrode potential at the final discharge voltage” refers to the open circuit potential (Open Circuit Potential: OCP) of the positive electrode at the final discharge voltage.

The membrane resistance at 25°C of the separator impregnated with the non-aqueous electrolyte is a value measured at a temperature of 25°C by the following procedure. A pouch cell is produced by sandwiching a sheet of separator impregnated with a non-aqueous electrolyte between a pair of aluminum foil electrodes (25 mm long and 30 mm wide) with lead tabs. The separator is cut into a length of 34 mm and a width of 45 mm. Moreover, the non-aqueous electrolyte provided in the non-aqueous electrolyte storage element is used as the non-aqueous electrolyte. That is, the non-aqueous electrolyte storage element is disassembled, and the measurement is performed using the separator and the non-aqueous electrolyte that constitute the non-aqueous electrolyte storage element. The prepared pouch cell is sandwiched between a pair of silicon sheets, and the four corners of the range of 35 mm in length and 60 mm in width in the direction of sandwiching the pair of silicon sheets are fixed by tightening with screws at a torque pressure of 10 cN·m. AC impedance is measured in the frequency range from 10 ⁻⁵ Hz to 10 ⁻⁶ Hz with an applied potential amplitude of 5 mV for the pouch cell in a fixed state. The membrane resistance is obtained from the resistance at a frequency of 10 ⁻⁶ Hz and the area of the separator (25 mm long and 30 mm wide) in contact with the aluminum foil electrode.

It is preferable that the content ratio of the nickel element to the metal elements other than the lithium element in the lithium-transition metal composite oxide is 50 mol % or more. By using a lithium-transition metal composite oxide having a high nickel content, the discharge capacity of the non-aqueous electrolyte storage element is increased. On the other hand, such a lithium-transition metal composite oxide generally has a positive electrode potential of 3.69 V vs. Cracking of the secondary particles is particularly likely to occur when discharge is performed to less than Li/Li ⁺ . Therefore, when one aspect of the present invention is applied to a non-aqueous electrolyte storage element using a lithium-transition metal composite oxide with a high nickel element content, the effect of improving the capacity retention rate is particularly pronounced.

The positive electrode potential at the end of charge voltage during normal use is 4.30 V vs. It is preferably Li/Li ⁺ or more. The positive electrode potential at the charging end voltage during normal use is 4.30 V vs. When the ratio is Li/Li ⁺ or more, the discharge capacity of the non-aqueous electrolyte storage element can be increased, the energy density can be increased, and the like.

The separator preferably has an inorganic particle layer. By using such a separator, for example, when the material of the base material layer of the separator is polyethylene, polyene formation of the base material layer of the separator, which is usually likely to occur when charging is performed such that the positive electrode potential reaches a high potential, is suppressed, and the capacity retention rate after charge-discharge cycles can be further increased.

A device according to another aspect of the present invention includes a non-aqueous electrolyte storage element and a charge/discharge control device, wherein the non-aqueous electrolyte storage element includes a positive electrode containing a lithium transition metal composite oxide containing nickel, a non-aqueous electrolyte, and a separator having a membrane resistance of 2.5 Ω·cm ² or more at 25°C when impregnated with the non-aqueous electrolyte. It is configured to discharge to less than Li/Li ⁺ .

The device has a positive electrode potential of 3.69 V vs. the non-aqueous electrolyte storage element. Even in the case where discharging to less than Li/Li ^{2 +} and charging are repeated, the capacity retention rate of the non-aqueous electrolyte storage element after charge-discharge cycles is high. Therefore, the device can be used for a long period of time, and the replacement frequency of the non-aqueous electrolyte storage element can be reduced.

A method of using a non-aqueous electrolyte storage element according to another aspect of the present invention is such that a positive electrode potential of a non-aqueous electrolyte storage element is 3.69 V vs. 3.69 V vs. a non-aqueous electrolyte storage element including a positive electrode containing a lithium transition metal composite oxide containing nickel, a non-aqueous electrolyte, and a separator having a membrane resistance of 2.5 Ω·cm ² or more at 25° C. when impregnated with the non-aqueous electrolyte. Discharging to less than Li/Li ⁺ is provided.

According to the method of use, the positive electrode potential as described above is 3.69 V vs. the non-aqueous electrolyte storage element. The capacity retention rate is also high when the discharge to less than Li/Li ⁺ and the charge are repeated.

A non-aqueous electrolyte storage element, a power storage device, a device, a method for using the non-aqueous electrolyte storage element, a method for manufacturing the non-aqueous electrolyte storage element, and other embodiments according to one embodiment of the present invention will be described in detail. Note that the name of each component (each component) used in each embodiment may be different from the name of each component (each component) used in the background art.

<Non-aqueous electrolyte storage element>
A non-aqueous electrolyte storage element according to one embodiment of the present invention (hereinafter also simply referred to as a "storage element") includes an electrode body having a positive electrode, a negative electrode, and a separator, a non-aqueous electrolyte, and a container that accommodates the electrode body and the non-aqueous electrolyte. The electrode body is usually a laminated type in which a plurality of positive electrodes and a plurality of negative electrodes are laminated with separators interposed therebetween, or a wound type in which positive electrodes and negative electrodes are laminated with separators interposed and wound. The non-aqueous electrolyte exists in a state impregnating the positive electrode, the negative electrode and the separator. A non-aqueous electrolyte secondary battery (hereinafter also simply referred to as a “secondary battery”) will be described as an example of a non-aqueous electrolyte storage element.

(positive electrode)
The positive electrode has a positive electrode base material and a positive electrode active material layer disposed directly on the positive electrode base material or via an intermediate layer.

A positive electrode base material has electroconductivity. Whether or not a material has "conductivity" is determined using a volume resistivity of 10 ⁷ Ω·cm as a threshold measured according to JIS-H-0505 (1975). As the material for the positive electrode substrate, metals such as aluminum, titanium, tantalum and stainless steel, or alloys thereof are used. Among these, aluminum or an aluminum alloy is preferable from the viewpoint of potential resistance, high conductivity, and cost. Examples of the positive electrode substrate include foil, deposited film, mesh, porous material, and the like, and foil is preferable from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferable as the positive electrode substrate. Examples of aluminum or aluminum alloy include A1085, A3003, A1N30, etc. defined in JIS-H-4000 (2014) or JIS-H4160 (2006).

The average thickness of the positive electrode substrate is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, even more preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode substrate within the above range, it is possible to increase the strength of the positive electrode substrate and increase the energy density per volume of the non-aqueous electrolyte storage element.

The intermediate layer is a layer arranged between the positive electrode substrate and the positive electrode active material layer. The intermediate layer contains a conductive agent such as carbon particles to reduce the contact resistance between the positive electrode substrate and the positive electrode active material layer. The composition of the intermediate layer is not particularly limited, and includes, for example, a binder and a conductive agent.

The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer contains optional components such as a conductive agent, a binder, a thickener, a filler, etc., as required.

The positive electrode active material contains a lithium transition metal composite oxide containing nickel element. The lower limit of the content ratio (Ni/Me) of the nickel element (Ni) to all the metal elements (Me) other than the lithium element in the lithium-transition metal composite oxide containing the nickel element may be, for example, 30 mol% or 40 mol%, but is preferably 50 mol%. By using such a lithium-transition metal composite oxide with a high nickel element content, the discharge capacity can be increased. On the other hand, the upper limit of the nickel element content ratio (Ni/Me) may be, for example, 100 mol %, 90 mol %, 80 mol %, 70 mol %, 60 mol %, or 50 mol %. The content ratio (Ni/Me) of the nickel element can be set to be equal to or greater than any of the lower limits described above and equal to or less than any of the upper limits described above.

The lithium-transition metal composite oxide containing nickel preferably further contains at least one of manganese and cobalt, more preferably both manganese and cobalt. The content ratio (Mn/Me) of the manganese element (Mn) to all the metal elements (Me) other than the lithium element in the lithium-transition metal composite oxide containing the nickel element is preferably 5 mol% or more and 50 mol% or less, and more preferably 10 mol% or more and 40 mol% or less. The content ratio (Co/Me) of the cobalt element (Co) with respect to all the metal elements (Me) other than the lithium element in the lithium-transition metal composite oxide containing the nickel element is preferably 1 mol% or more and 40 mol% or less, and more preferably 5 mol% or more and 30 mol% or less.

The lithium-transition metal composite oxide containing the nickel element may further contain a metal element (Me') other than the nickel element, manganese element, cobalt element and lithium element. Other metal elements (Me') include, for example, an aluminum element. However, the content ratio (Me'/Me) of the other metal element (Me') to all the metal elements (Me) other than the lithium element in the lithium-transition metal composite oxide containing the nickel element is preferably 10 mol% or less, and may be more preferably 5 mol% or less, 1 mol% or less, 0.1 mol% or less, or 0 mol%.

In this specification, the composition ratio of the lithium-transition metal composite oxide containing nickel element refers to the composition ratio before charging/discharging or when completely discharged by the following method. First, the non-aqueous electrolyte storage element is charged at a constant current with a charging current of 0.05 C until it reaches the charging end voltage for normal use, and is brought into a fully charged state. After resting for 30 minutes, constant current discharge is performed at a discharge current of 0.05C to the lower limit voltage for normal use. The battery was disassembled, the positive electrode was taken out, and a test battery with a metallic lithium electrode as the counter electrode was assembled. Constant current discharge is performed until Li/Li ⁺ to adjust the positive electrode to a fully discharged state. Pure metallic lithium is used for the metallic lithium electrode here. Dismantle again and take out the positive electrode. Using dimethyl carbonate, the non-aqueous electrolyte adhering to the taken-out positive electrode is sufficiently washed and dried at room temperature for a whole day and night. The sampled lithium-transition metal composite oxide containing nickel element is subjected to measurement. The work from dismantling the non-aqueous electrolyte storage element to extracting the lithium transition metal composite oxide containing nickel element is performed in an argon atmosphere with a dew point of -60°C or less.

Examples of lithium-transition metal composite oxides containing nickel include compounds having a layered α-NaFeO ₂ -type crystal structure, compounds having a spinel-type crystal structure, etc. Compounds having a layered α-NaFeO ₂ -type crystal structure are preferred. These materials may be coated with other materials on their surfaces. Moreover, these materials may be used individually by 1 type, and 2 or more types may be mixed and used.

The lithium-transition metal composite oxide containing nickel element may be a compound represented by Formula 1 below.

Li _1+α Me _1-α O ₂ . . . 1
In Formula 1, Me is a metal element other than Li, including Ni. 0≦α<1.

α in Formula 1 may be 0 or more and 0.5 or less, 0 or more and 0.3 or less, 0 or more and 0.1 or less, or 0. In addition to Ni, Me may further contain metallic elements such as Co and Mn. As the preferred content ratio (composition ratio) of each metal element such as Ni to Me in the compound represented by Formula 1, the preferred content ratio of each element in the lithium-transition metal composite oxide described above can be adopted.

Specific examples of lithium transition metal composite oxides containing nickel include LiNi3 _{/ 5Co1} / _{5Mn1/ 5O2} , LiNi1 _/2Co1 / _{5Mn3 / 10O2} , LiNi1/ _{2Co3 / 10Mn1} / _5O2 , and LiNi8 _{/ 10Co1} / _{10Mn1/ 10O2} . I can.

The content of the lithium-transition metal composite oxide containing nickel element in the positive electrode active material layer is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, and even more preferably 90% by mass or more and 98.5% by mass or less. By setting the content of the lithium-transition metal composite oxide containing the nickel element within the above range, it is possible to achieve both high energy density and manufacturability of the positive electrode active material layer. In some aspects, the content of the lithium-transition metal composite oxide may be 92% by mass or more, or 95% by mass or more.

The positive electrode active material layer may further contain a positive electrode active material other than the lithium-transition metal composite oxide containing the nickel element. Examples of such positive electrode active materials include conventionally known positive electrode active materials such as lithium-transition metal composite oxides, polyanion compounds, chalcogen compounds, and sulfur that do not contain nickel element. These materials may be coated with other materials on their surfaces. Moreover, these materials may be used individually by 1 type, and 2 or more types may be mixed and used.

The lower limit of the content of the lithium-transition metal composite oxide containing nickel element in all positive electrode active materials is preferably 80% by mass, more preferably 90% by mass, still more preferably 95% by mass, and even more preferably 99% by mass. The positive electrode active material may be only a lithium-transition metal composite oxide containing nickel element. Thus, by increasing the content of the lithium-transition metal composite oxide containing the nickel element with respect to all the positive electrode active materials, the discharge capacity of the non-aqueous electrolyte storage element can be increased.

The positive electrode active material is usually particles (powder). The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By making the average particle size of the positive electrode active material equal to or more than the above lower limit, manufacturing or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electron conductivity of the positive electrode active material layer is improved. Note that when a composite of a positive electrode active material and another material is used, the average particle size of the composite is taken as the average particle size of the positive electrode active material. The "average particle size" is based on JIS-Z-8825 (2013), based on the particle size distribution measured by a laser diffraction/scattering method for a diluted solution of particles diluted with a solvent, and based on JIS-Z-8819-2 (2001).

A pulverizer, a classifier, or the like is used to obtain powder having a predetermined particle size. Pulverization methods include, for example, methods using a mortar, ball mill, sand mill, vibrating ball mill, planetary ball mill, jet mill, counter jet mill, whirling jet mill, or sieve. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane is allowed to coexist can also be used. As a classification method, a sieve, an air classifier, or the like is used as necessary, both dry and wet.

The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 98% by mass or less, and even more preferably 80% by mass or more and 95% by mass or less. 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 of the positive electrode active material layer.

The conductive agent is not particularly limited as long as it is a conductive material. Examples of such conductive agents include carbonaceous materials, metals, and conductive ceramics. Carbonaceous materials include graphite, non-graphitic carbon, graphene-based carbon, and the like. Examples of non-graphitic carbon include carbon nanofiber, pitch-based carbon fiber, and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Graphene-based carbon includes graphene, carbon nanotube (CNT), fullerene, and the like. The shape of the conductive agent may be powdery, fibrous, or the like. As the conductive agent, one type of these materials may be used alone, or two or more types may be mixed and used. Also, these materials may be combined for use. For example, a composite material of carbon black and CNT may be used. Among these, carbon black is preferable from the viewpoint of electron conductivity and coatability, and acetylene black is particularly preferable.

The content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 10% by mass or less, more preferably 3% by mass or more and 9% by mass or less. By setting the content of the conductive agent within the above range, the energy density of the non-aqueous electrolyte storage element can be increased.

Examples of binders include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, polyacryl, and polyimide; ethylene-propylene-diene rubbers (EPDM), sulfonated EPDM, styrene-butadiene rubbers (SBR), elastomers such as fluororubbers; polysaccharide polymers, and the like.

The content of the binder in the positive electrode active material layer is preferably 1% by mass or more and 10% by mass or less, more preferably 3% by mass or more and 9% by mass or less. By setting the binder content within the above range, the positive electrode active material can be stably retained.

Examples of thickeners include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium or the like, the functional group may be previously deactivated by methylation or the like. When a thickener is used, the content of the thickener in the positive electrode active material layer can be 8% by mass or less, preferably 5% by mass or less or 1% by mass or less. The technique disclosed here can be preferably implemented in a mode in which the positive electrode active material layer does not contain a thickening agent.

A filler is not specifically limited. Fillers include polyolefins such as polypropylene and polyethylene; inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide and aluminosilicate; , spinel, olivine, sericite, bentonite, mica, and other substances derived from mineral resources, or artificial products thereof. When using a filler, the content of the filler in the positive electrode active material layer can be 8% by mass or less, preferably 5% by mass or less or 1% by mass or less. The technology disclosed here can be preferably implemented in a mode in which the positive electrode active material layer does not contain filler.

The positive electrode active material layer contains typical nonmetallic elements such as B, N, P, F, Cl, Br, and I; typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; You may

Although the porosity of the positive electrode active material layer is not particularly limited, it is, for example, 20% or more and 45% or less. In some aspects, the porosity of the positive electrode active material layer may be 22% or more and 42% or less, or may be 25% or more and 38% or less. When the porosity of the positive electrode active material layer is within such a range, together with the use of the above-described high-resistance separator, the above-described effects can be exhibited more effectively. The “porosity (%)” of the positive electrode active material layer is obtained by the formula {1−(V ₂ /V ₁ )}×100, where V ₁ is the apparent volume (volume including voids) of the positive electrode active material layer and V ₂ is the sum of the actual volumes of the materials constituting the positive electrode active material layer. The sum _V2 of the actual volume of each material constituting the positive electrode active material layer can be calculated from the content of each material in the positive electrode active material layer and the true density of each material. The same applies to the porosity of the negative electrode active material layer, which will be described later.

(negative electrode)
The negative electrode has a negative electrode base material and a negative electrode active material layer disposed directly on the negative electrode base material or via an intermediate layer. The structure of the intermediate layer is not particularly limited, and can be selected from, for example, the structures exemplified for the positive electrode.

A negative electrode base material has electroconductivity. As materials for the negative electrode substrate, metals such as copper, nickel, stainless steel, nickel-plated steel, aluminum, alloys thereof, carbonaceous materials, and the like are used. Among these, copper or a copper alloy is preferred. Examples of negative electrode substrates include foils, deposited films, meshes, porous materials, and the like, and foils are preferred from the viewpoint of cost. Therefore, copper foil or copper alloy foil is preferable as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

The average thickness of the negative electrode substrate is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, even more preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate within the above range, it is possible to increase the strength of the negative electrode substrate and increase the energy density per volume of the non-aqueous electrolyte storage element.

The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer contains arbitrary components such as a conductive agent, a binder, a thickener, a filler, etc., as required. Optional components such as conductive agents, binders, thickeners, and fillers can be selected from the materials exemplified for the positive electrode.

When a conductive agent is used in the negative electrode active material layer, the content of the conductive agent in the negative electrode active material layer can be 10% by mass or less, preferably 8% by mass or less or 3% by mass or less. The technology disclosed here can be preferably implemented in a mode in which the negative electrode active material layer does not contain a conductive agent. When a binder is used in the negative electrode active material layer, the binder content relative to the negative electrode active material layer is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 8% by mass or less. When a thickener is used in the negative electrode active material layer, the content of the thickener in the negative electrode active material layer can be 0.5% by mass or more and 8% by mass or less, preferably 1% by mass or more and 6% by mass or less. When a filler is used in the negative electrode active material layer, the content of the filler with respect to the negative electrode active material layer can be 8% by mass or less, preferably 5% by mass or less or 1% by mass or less. The technique disclosed here can be preferably implemented in a mode in which the negative electrode active material layer does not contain a filler.

The negative electrode active material layer includes typical nonmetallic elements such as B, N, P, F, Cl, Br, and I; typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W; , may be contained as a component other than the filler.

The negative electrode active material can be appropriately selected from known negative electrode active materials. Materials capable of intercalating and deintercalating lithium ions are usually used as negative electrode active materials for lithium ion secondary batteries. As a negative electrode active substance, for example, metal or half metal such as metal Li; SI, SN; SI oxide, TI oxide, SN oxide, metal oxide or semi -metal oxide; LI ₄ Ti ₅ O ₁₂ , Litio _2, Tinb ₂ O ₇ , etc. Shaft; polyirin oxide, carbon material, such as carbon material such as graphite (graphite), non -black lead carbon (graphite), non -black lead -based carbon or hard -leading carbon. Among these materials, graphite and non-graphitic carbon are preferred, and graphite is more preferred. In the negative electrode active material layer, one type of these materials may be used alone, or two or more types may be mixed and used.

“Graphite” refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane determined by X-ray diffraction before charging/discharging or in a discharged state of 0.33 nm or more and less than 0.34 nm. Graphite includes natural graphite and artificial graphite. Artificial graphite is preferable from the viewpoint that a material with stable physical properties can be obtained.

“Non-graphitic carbon” refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane of 0.34 nm or more and 0.42 nm or less as determined by an X-ray diffraction method before charging/discharging or in a discharged state. Non-graphitizable carbon includes non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials.

Here, the term “discharged state” means a state in which the carbon material, which is the negative electrode active material, is discharged such that lithium ions that can be intercalated and deintercalated are sufficiently released during charging and discharging. For example, in a half-cell using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and metal Li as a counter electrode, the open circuit voltage is 0.7 V or higher.

The term “non-graphitizable carbon” refers to a carbon material having a d ₀₀₂ of 0.36 nm or more and 0.42 nm or less.

“Graphitizable carbon” refers to a carbon material having a d ₀₀₂ of 0.34 nm or more and less than 0.36 nm.

The negative electrode active material is usually particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide or a polyphosphate compound, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 μm or less. By making the average particle size of the negative electrode active material equal to or greater than the above lower limit, the production or handling of the negative electrode active material is facilitated. By making the average particle size of the negative electrode active material equal to or less than the above upper limit, the electron conductivity of the negative electrode active material layer is improved. A pulverizer, a classifier, or the like is used to obtain powder having a predetermined particle size. The pulverization method and the powder class method can be selected from, for example, the methods exemplified for the positive electrode. When the negative electrode active material is metal such as metal Li, the negative electrode active material layer may be foil-shaped.

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

Although the porosity of the negative electrode active material layer is not particularly limited, it is, for example, 30% or more and 55% or less. In some aspects, the porosity of the negative electrode active material layer may be 32% or more and 52% or less, or 35% or more and 50% or less. When the porosity of the negative electrode active material layer is within such a range, together with the use of the above-described high-resistance separator, the above-described effects can be exhibited more effectively.

(separator)
A separator having a membrane resistance of 2.5 Ω·cm ² or more at 25° C. in a state impregnated with a non-aqueous electrolyte is used as the separator. The separator includes, for example, a separator consisting of only a substrate layer, a separator having a substrate layer and an inorganic particle layer laminated on one or both surfaces of the substrate layer, and the like. The separator is preferably a separator having a substrate layer and an inorganic particle layer laminated on one or both surfaces of the substrate layer.

In one embodiment of the non-aqueous electrolyte storage element of the present invention, it is preferable that the surface of the positive electrode faces the surface of the inorganic particle layer of the separator. For example, when the separator has a base material layer and inorganic particle layers laminated on both sides of the base material layer, the above configuration is usually inevitably satisfied. Further, when the separator has a substrate layer and an inorganic particle layer laminated only on one surface of this substrate layer, the inorganic particle layer side of the separator is arranged on the positive electrode side, and the substrate layer side of the separator is arranged on the negative electrode side. In the case of such a configuration, for example, the material of the base material layer of the separator is polyethylene, and polyene formation of the base material layer of the separator is suppressed when charging is performed such that the positive electrode potential reaches a high potential, and the capacity retention rate after charge-discharge cycles can be further increased. Among them, in a non-aqueous electrolyte storage element using a separator having an inorganic particle layer laminated only on one surface of a base material layer, and in which the inorganic particle layer faces the surface of the positive electrode, the effect of applying this aspect can be more preferably exhibited.

Examples of the shape of the base layer of the separator include woven fabric, nonwoven fabric, and porous resin film. Among these shapes, a porous resin film is preferred from the viewpoint of strength, and a non-woven fabric is preferred from the viewpoint of retention of a non-aqueous electrolyte. The material of the base layer of the separator is usually resin. As the material for the base layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of shutdown function, and polyimide, aramid, and the like are preferable from the viewpoint of oxidative decomposition resistance. A material obtained by combining these resins may be used as the base material layer of the separator.

The average thickness of the base material layer of the separator is preferably 5 μm or more and 30 μm or less, more preferably 10 μm or more and 20 μm or less (for example, 16 μm or less). By setting the average thickness of the base material layer of the separator within the above range, it is possible to achieve compatibility between sufficient strength and the like and high energy density and the like. The average thickness of the base material layer of the separator means the average value of thicknesses measured at arbitrary five points in the base material layer obtained by removing the inorganic particle layer from the separator. The same applies to the average thickness of the separator, which will be described later.

The inorganic particle layer is a layer containing inorganic particles. The inorganic particles are preferably the main component in the inorganic particle layer. A main component means a component with the largest content on a mass basis. The inorganic particle layer may be a layer containing inorganic particles and a binder. The content of the inorganic particles in the inorganic particle layer is preferably 50% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 97% by mass or less.

Inorganic particles are particles composed of inorganic compounds. The inorganic particles may be particles consisting essentially of an inorganic compound. Examples of inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; Mineral resource-derived substances such as kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof may be used. As the inorganic compound, a single substance or a composite of these substances may be used alone, or two or more of them may be mixed and used. Among these inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate is preferable from the viewpoint of the safety of the non-aqueous electrolyte storage device.

As the binder for the inorganic particle layer, those exemplified as the binder for the positive electrode active material layer can be used. The content of the binder in the inorganic particle layer is, for example, preferably 1% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 30% by mass or less.

The porosity of the inorganic particle layer is preferably 80% by volume or less, more preferably 60% by volume or less, from the viewpoint of strength and the like. The porosity is preferably 20% by volume or more, more preferably 40% by volume or more, from the viewpoint of discharge performance and the like. In some aspects, the porosity of the inorganic particle layer may be 55% by volume or less, or may be 50% by volume or less. When the porosity of the inorganic particle layer is within such a range, the application effect of the present embodiment can be exhibited more preferably. Here, the “porosity of the inorganic particle layer” is a value calculated by the formula “{1−(apparent density of inorganic particle layer/true density of inorganic particle layer)}×100”. The true density of the inorganic particle layer is calculated from the true density and the content ratio of the constituent components of the inorganic particle layer. The apparent density of the inorganic particle layer is calculated from the mass and apparent volume of the inorganic particle layer.

The average thickness of one layer of the inorganic particle layer is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less, and even more preferably 3 μm or more and 6 μm or less. When the average thickness of one layer of the inorganic particle layer is at least the above lower limit, for example, when the material of the base material layer of the separator is polyethylene and charging is performed so that the positive electrode potential reaches a high potential, polyene formation of the base material layer is particularly sufficiently suppressed, and the capacity retention rate after charge-discharge cycles can be further increased. When the average thickness of one layer of the inorganic particle layer is equal to or less than the above upper limit, it is possible to prevent the separator from becoming too thick and increase the energy density per volume of the non-aqueous electrolyte storage element. The average thickness of one inorganic particle layer is calculated by dividing the difference between the average thickness of the separator and the average thickness of the substrate layer by the number of inorganic particle layers.

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

The average thickness of the separator (the total average thickness of the substrate layer and the inorganic particle layer of the entire separator) is preferably 5 μm or more and 35 μm or less, preferably 10 μm or more and 30 μm or less, and more preferably 15 μm or more and 25 μm or less. By setting the average thickness of the separator within the above range, it is possible to achieve compatibility between sufficient strength and the like and high energy density and the like.

The air permeability of the separator is not particularly limited, but may be, for example, 200 seconds/100 cm ³ or more. In some aspects, the air permeability of the separator may be 210 sec/100 cm ³ or greater, such as 240 sec/100 cm ³ or greater. Also, the air permeability of the separator may be, for example, 300 seconds/100 cm ³ or less. In some aspects, the air permeability of the separator may be 280 sec/100 cm ³ or less, such as 250 sec/100 cm ³ or less. The "air permeability" referred to here is a value measured by the "Gurley tester method" conforming to JIS-P8117 (2009).

The lower limit of the membrane resistance at 25° C. of the separator impregnated with the non-aqueous electrolyte is 2.5 Ω·cm ² , preferably 2.8 Ω·cm ² , more preferably 3.0 Ω·cm ² , still more preferably 3.2 Ω·cm 2 , 3.3 Ω ^{·cm 2 ,} 3.5 Ω·cm ² , 4.0 Ω·cm ² , 4.5 Ω·cm ² or 5.0 Ω·cm ² (for example, 5.2 Ω·cm 2 ). cm ² ) may be even more preferred. When the membrane resistance at 25° C. of the separator impregnated with the non-aqueous electrolyte is equal to or higher than the above lower limit, the capacity retention rate after charge-discharge cycles can be increased. On the other hand, the upper limit of the film resistance may be, for example, 10.0 Ω·cm ² , 8.0 Ω·cm ² , 6.0 Ω·cm ² , 5.0 Ω·cm ² or 4.0 Ω·cm ² . The membrane resistance at 25° C. of the separator impregnated with the non-aqueous electrolytic solution can be at least any one of the above lower limits and not more than any of the above upper limits.

The membrane resistance at 25° C. of the separator impregnated with the non-aqueous electrolyte can be adjusted by the type of separator, the composition of the non-aqueous electrolyte, and the like. For example, when the porosity of the separator is low, the membrane resistance at 25° C. when impregnated with the non-aqueous electrolyte tends to be high. However, since the material of each layer of the separator, the diameter of the pores, etc. also have an effect, for example, the magnitude relationship of the porosity of the separator does not necessarily match the magnitude relationship of the film resistance. Further, when the viscosity of the non-aqueous electrolyte is high, the membrane resistance tends to be high. In addition, the electrolyte salt concentration of the non-aqueous electrolyte, the material of each component of the non-aqueous electrolyte, and the like may affect the membrane resistance. A commercially available product can be used as the separator. For example, various commercially available separators are prepared, combined with various non-aqueous electrolytes, and the membrane resistance of the separators in each combination at 25 ° C. is measured, and the combination of the separator and the non-aqueous electrolyte having a membrane resistance at 25 ° C. of 2.5 Ω cm ² or more may be selected and used.

(Non-aqueous electrolyte)
The non-aqueous electrolyte can be appropriately selected from known non-aqueous electrolytes. The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in this non-aqueous solvent.

The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Non-aqueous solvents include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, amides, nitriles and the like. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are substituted with halogens may be used.

Cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, and the like. Among these, EC and PC are preferred. When EC and PC are used together, the volume ratio of EC to PC (EC:PC) may be approximately 10:1 to 1:5 (eg 8:1 to 1:1, typically 5:1 to 2:1).

Chain carbonates include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diphenyl carbonate, trifluoroethylmethyl carbonate, bis(trifluoroethyl) carbonate and the like. Among these, EMC is preferred.

As the non-aqueous solvent, it is preferable to use a cyclic carbonate or a chain carbonate, and it is more preferable to use a combination of a cyclic carbonate and a chain carbonate. By using a cyclic carbonate, it is possible to promote the dissociation of the electrolyte salt and improve the ionic conductivity of the non-aqueous electrolyte. By using a chain carbonate, the viscosity of the non-aqueous electrolyte can be kept low. When a cyclic carbonate and a chain carbonate are used together, the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate:chain carbonate) is, for example, preferably in the range of 5:95 to 50:50, more preferably in the range of 20:80 to 40:60. The volume ratio of cyclic carbonate to chain carbonate (cyclic carbonate:chain carbonate) may be, for example, in the range of 30:70 to 40:60.

The electrolyte salt can be appropriately selected from known electrolyte salts. Examples of electrolyte salts include lithium salts, sodium salts, potassium salts, magnesium salts, onium salts and the like. Among these, lithium salts are preferred.

Lithium salts include inorganic lithium salts such as _LiPF6 , _{LiPO2F2 , LiBF4} , _LiClO4 , LiN(SO2F)2; 2CF ₃ ) _{2 , LiN} (SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ CF ₃ )(SO ₂ C 4 F ₉ ), LiC(SO ₂ CF ₃ ) ₃ , LiC( _{SO 2 C 2 F 5 ) 3} and _other lithium salts having halogenated hydrocarbon groups. Among these, inorganic lithium salts are preferred, and _LiPF6 is more preferred.

The content of the electrolyte salt in the non-aqueous electrolytic solution is preferably 0.1 mol/dm ³ or more and 2.5 mol/dm 3 or less, more preferably 0.3 mol/dm ³ or more and 2.0 mol/dm ^{3 or} less, further preferably 0.5 mol/dm ³ or more and 1.7 mol/dm ³ or less, and particularly 0.7 mol/dm ³ or more and 1.5 mol/dm ^{3 or} less at 20° C. and 1 atm. Preferred. By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

The non-aqueous electrolyte may contain additives in addition to the non-aqueous solvent and electrolyte salt. Examples of additives include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; partial halides of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5- Halogenated anisole compounds such as difluoroanisole; vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; , diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyl disulfide, dipyridinium disulfide, 1,3-propenesultone, 1,3-propanesultone, 1,4-butanesultone, 1, 4-butene sultone, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetrakis trimethylsilyl titanate, lithium monofluorophosphate, lithium difluorophosphate and the like. These additives may be used singly or in combination of two or more.

The content of the additive contained in the nonaqueous electrolyte is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less. By setting the content of the additive within the above range, it is possible to improve capacity retention performance or cycle performance after high-temperature storage, or to further improve safety.

(positive electrode potential, etc.)
The positive electrode potential at the discharge end voltage during normal use in the non-aqueous electrolyte storage element according to one embodiment of the present invention is 3.69 V vs. Li/Li ⁺ less than 3.66 V vs. Less than Li/Li ⁺ is preferred, 3.63 V vs. Less than Li/Li ⁺ is more preferred, 3.61 V vs. Less than Li/Li ⁺ is even more preferred. When the positive electrode potential at the discharge end voltage during normal use is less than the above upper limit, the discharge capacity of the non-aqueous electrolyte storage element can be increased. The positive electrode potential at the discharge end voltage during normal use is, for example, 3.40 V vs. Li/Li ⁺ or more, 3.50V vs. Li/Li ⁺ or more, 3.54V vs. Li/Li ⁺ or more, 3.58V vs. Li/Li ⁺ or more or 3.60 V vs. It may be Li/Li ⁺ or more. The positive electrode potential at the discharge cutoff voltage during normal use can be at least one of the above lower limits and below one of the above upper limits. The positive electrode potential at the discharge final voltage during normal use can be adjusted by the set discharge final voltage, the type and amount of the active material used in the positive electrode and the negative electrode, and the like.

In the non-aqueous electrolyte storage element according to one embodiment of the present invention, the positive electrode potential at the charging end voltage during normal use is, for example, 4.00 V vs. Li/Li ⁺ or higher, but 4.30V vs. Li/Li ⁺ or more is preferable, and 4.32 V vs. Li/Li ⁺ or more is more preferable, and 4.34 V vs. More preferably Li/Li ⁺ or more. The discharge capacity of the non-aqueous electrolyte storage element can be increased by setting the positive electrode potential at the end-of-charge voltage during normal use to the above lower limit or more. The positive electrode potential at the charge termination voltage during normal use is, for example, 4.50 V vs. Li/Li ⁺ or less, 4.45V vs. Li/Li ⁺ or less, 4.40 V vs. Li/Li ⁺ or less or 4.35V vs. It may be Li/Li ⁺ or less. The positive electrode potential at the end-of-charge voltage during normal use can be at least one of the above lower limits and not more than any of the above upper limits. The positive electrode potential at the end-of-charge voltage during normal use can be adjusted by the end-of-charge voltage to be set, the type and amount of the active material used in the positive electrode and the negative electrode, and the like.

The shape of the non-aqueous electrolyte storage element of the present embodiment is not particularly limited, and examples thereof include cylindrical batteries, rectangular batteries, flat batteries, coin batteries, button batteries, and the like.

FIG. 1 shows a non-aqueous electrolyte storage element 1 as an example of a square battery. In addition, the same figure is taken as the figure which saw through the inside of a container. An electrode body 2 having a positive electrode and a negative electrode wound with a separator sandwiched therebetween is housed in a rectangular container 3 . The positive electrode is electrically connected to the positive electrode terminal 4 via a positive electrode lead 41 . The negative electrode is electrically connected to the negative terminal 5 via a negative lead 51 .

<Power storage device>
The non-aqueous electrolyte storage element of the present embodiment can be mounted as a power storage unit (battery module) configured by collecting a plurality of non-aqueous electrolyte storage elements 1 in a power source for automobiles such as electric vehicles (EV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV), power sources for electronic devices such as personal computers and communication terminals, or power sources for power storage. In this case, the technology of the present invention may be applied to at least one non-aqueous electrolyte storage element included in the storage unit.

FIG. 2 shows an example of a power storage device 30 in which a power storage unit 20 in which two or more electrically connected non-aqueous electrolyte power storage elements 1 are assembled is further assembled. The power storage device 30 may include a bus bar (not shown) electrically connecting two or more non-aqueous electrolyte power storage elements 1, a bus bar (not shown) electrically connecting two or more power storage units 20, or the like. The power storage unit 20 or the power storage device 30 may include a state monitoring device (not shown) that monitors the state of one or more non-aqueous electrolyte power storage elements.

<Equipment>
A device according to one embodiment of the present invention includes a non-aqueous electrolyte storage element and a charge/discharge control device. The non-aqueous electrolyte storage element includes a positive electrode containing a lithium transition metal composite oxide containing nickel, a non-aqueous electrolyte, and a separator having a membrane resistance of 2.5 Ω·cm or ^more at 25° C. when impregnated with the non-aqueous electrolyte. The specific form and preferred form of the non-aqueous electrolyte storage element provided in the device are the same as the specific form and preferred form of the non-aqueous electrolyte storage element according to the embodiment of the present invention described above.

The charge/discharge control device sets the positive electrode potential to 3.69 V vs. the non-aqueous electrolyte storage element. It is configured to discharge to less than Li/Li ⁺ . For example, in this charge/discharge control device, a final voltage (discharge final voltage) for discharging the non-aqueous electrolyte storage element is set, and the positive electrode potential at this discharge final voltage is 3.69 V vs. It is less than Li/Li ⁺ . In other words, in the device, the charge/discharge control device controls the non-aqueous electrolyte storage element so that the positive electrode potential is 3.69 V vs. It is configured to be able to discharge to less than Li/Li ⁺ . In addition, when using the apparatus, the positive electrode potential is 3.69 V vs. Li/Li ⁺ less than discharge was not performed, and the positive electrode potential was 3.69 V vs. Charging may occur before reaching less than Li/Li ⁺ . It is preferable that the charge/discharge control device is configured to discharge the non-aqueous electrolyte storage element according to the above-described embodiment of the present invention to a suitable range of positive electrode potential at the discharge end voltage during normal use of the non-aqueous electrolyte storage element. Further, the charge/discharge control device is preferably configured to charge the non-aqueous electrolyte storage element according to the above-described embodiment of the present invention to a suitable range of positive electrode potential at the end-of-charge voltage during normal use of the non-aqueous electrolyte storage element.

In this way, the device has a positive electrode potential of 3.69 V vs. the non-aqueous electrolyte storage element. Since the charge/discharge control device is configured to discharge to less than Li/Li ⁺ , the discharge capacity of the non-aqueous electrolyte storage element is large. In addition, since the device includes a positive electrode containing a lithium-transition metal composite oxide containing nickel element, a non-aqueous electrolyte, and a separator having a membrane resistance at 25° C. of 2.5 Ω·cm ² or more when impregnated with the non-aqueous electrolyte, the positive electrode potential is 3.69 V vs. the non-aqueous electrolyte storage element. Even in the case where discharging to less than Li/Li ^{2 +} and charging are repeated, the capacity retention rate of the non-aqueous electrolyte storage element after charge-discharge cycles is high.

Examples of such devices include, but are not limited to, electronic devices such as personal computers, communication terminals, home appliances, automobiles (EV, HEV, PHEV, etc.), and other industrial devices.

<How to use the non-aqueous electrolyte storage element>
A non-aqueous electrolyte storage element according to an embodiment ^of the present invention is used in such a manner that the positive electrode potential is 3.69 V vs. 3.69 V vs. 3.69 V vs. Discharging to less than Li/Li ⁺ is provided.

The specific form and preferred form of the non-aqueous electrolyte electric storage element used in the method of use are the same as the specific form and preferred form of the non-aqueous electrolytic electric storage element according to the embodiment of the present invention described above. In addition, the preferred range of the positive electrode potential at the end of discharge in the discharge of the usage method is the same as the preferred range of the positive electrode potential at the discharge end voltage during normal use of the non-aqueous electrolyte storage element according to one embodiment of the present invention. According to this method of use, the capacity retention rate of the non-aqueous electrolyte storage element after charge-discharge cycles is high.

The method of use is such that the positive electrode potential is 4.30 V vs. Preferably, it further comprises charging to Li/Li ⁺ or higher. The preferred range of the positive electrode potential at the end of charging in the above charging of the usage method is the same as the preferred range of the positive electrode potential at the end of charging voltage during normal use of the non-aqueous electrolyte storage element according to one embodiment of the present invention.

<Method for manufacturing non-aqueous electrolyte storage element>
A method for manufacturing the non-aqueous electrolyte storage element of the present embodiment can be appropriately selected from known methods. The manufacturing method includes, for example, preparing an electrode body, preparing a non-aqueous electrolyte, and storing the electrode body and the non-aqueous electrolyte in a container. Preparing the electrode body includes preparing a positive electrode and a negative electrode, and forming the electrode body by laminating or winding the positive electrode and the negative electrode with a separator interposed therebetween.

A suitable method for containing the non-aqueous electrolyte in the container can be selected from known methods. For example, after injecting the non-aqueous electrolyte from an injection port formed in the container, the injection port may be sealed.

<Other embodiments>
The non-aqueous electrolyte storage device and the like of the present invention are not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of one embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a known technique. Furthermore, some of the configurations of certain embodiments can be deleted. Also, well-known techniques can be added to the configuration of a certain embodiment.

In the above embodiment, the non-aqueous electrolyte storage element is used as a chargeable/dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery), but the type, shape, size, capacity, etc. of the non-aqueous electrolyte storage element are arbitrary. The present invention can also be applied to capacitors such as various secondary batteries, electric double layer capacitors, and lithium ion capacitors.

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

[Example 1]
(Preparation of positive electrode)
A positive electrode mixture paste containing LiNi _1/2 Co _1/5 Mn _3/10 O ₂ as a positive electrode active material, PVDF as a binder, acetylene black as a conductive agent, and N-methylpyrrolidone as a dispersion medium was prepared. The mass ratio of the positive electrode active material, the binder, and the conductive agent was 93:3.5:3.5 in terms of solid content. A positive electrode active material layer was formed by coating the positive electrode material mixture paste on an aluminum foil as a positive electrode substrate, drying, and pressing. As a result, a positive electrode in which the positive electrode active material layer was laminated on the positive electrode substrate was obtained. The porosity of the positive electrode active material layer was set to 30%.

(Preparation of negative electrode)
A negative electrode mixture paste containing graphite as a negative electrode active material, SBR as a binder, and CMC as a thickener and using water as a dispersion medium was prepared. The mass ratio of the negative electrode active material, the binder, and the thickener was 98:1:1 in terms of solid content. The negative electrode mixture paste was applied to a copper foil as a negative electrode base material, dried, and pressed to form a negative electrode active material layer. As a result, a negative electrode in which the negative electrode active material layer was laminated on the negative electrode substrate was obtained. The porosity of the negative electrode active material layer was set to 35%.

(Preparation of non-aqueous electrolyte)
A non-aqueous electrolyte solution was prepared by mixing LiPF ₆ as an electrolyte salt at a concentration of 1.0 mol/dm ³ with a non-aqueous solvent obtained by mixing ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) at a predetermined volume ratio.

(Assembly of non-aqueous electrolyte storage element)
An electrode assembly was produced by laminating the above positive electrode and negative electrode with a separator interposed therebetween. A non-aqueous electrolyte storage element of Example 1 was obtained by housing the electrode body in a container and injecting the non-aqueous electrolyte into the container.
The separator has an average thickness of 20 μm, in which an inorganic particle layer containing aluminum-containing oxide particles (average thickness: 4 μm, porosity: 48% by volume) is laminated on one side of a substrate layer that is a polyolefin porous resin film. The membrane resistance of this separator impregnated with the prepared non-aqueous electrolytic solution at 25° C. was measured by the method described above and was 3.3 Ω·cm ² . In the production of the electrode body, the separator was arranged so that the inorganic particle layer side of the separator faced the positive electrode and the substrate layer side of the separator faced the negative electrode, thereby obtaining the electrode body.

[Example 2, Comparative Examples 1 and 2, Reference Examples 1 to 4]
Non-aqueous electrolyte storage elements of Example 2, Comparative Examples 1 and 2, and Reference Examples 1 to 4 were obtained in the same manner as in Example 1, except that the separators shown in Table 1 (both separators in which an inorganic particle layer was laminated on one side of a base layer made of a polyolefin porous resin film) were used. The air permeability of the separator used in Example 2 was 273 sec/cm ³ . Further, the non-aqueous electrolyte storage elements of Reference Examples 1 to 4 differ only in discharge final voltage, which will be described later.

[evaluation]
(Charge-discharge cycle test)
A charge/discharge cycle test was performed on each of the obtained non-aqueous electrolyte storage elements in the following manner. Constant-current and constant-voltage charging was performed at 45° C. with a charging current of 1.0 C and a charge termination voltage of 4.25 V. The charge termination condition was the time when the current value attenuated to 0.1C. Thereafter, constant current discharge was performed with a discharge current of 1.0 C and a discharge final voltage shown in Table 1. A rest period of 10 minutes was provided after charging and after discharging. This charging/discharging was performed 1,000 cycles.
Table 1 also shows the positive electrode potential at the final discharge voltage in the first cycle. Further, the positive electrode potential at the charging end voltage (4.25 V) in the first cycle was 4.34 V vs. Li/Li ⁺ .
The ratio of the discharge capacity at the 1,000th cycle to the discharge capacity at the 1st cycle in each non-aqueous electrolyte storage element was determined as the capacity retention rate. Then, in each of the non-aqueous electrolyte storage elements of Examples 1 and 2 and Comparative Examples 1 and 2 having a discharge end voltage of 2.75 V, the capacity retention rate (relative value) of each non-aqueous electrolyte storage element was obtained as a relative value based on the capacity retention rate of the non-aqueous electrolyte storage element of Example 1 (100%). Further, in each of the non-aqueous electrolyte storage elements of Reference Examples 1 to 4 having a discharge end voltage of 3.50 V, the capacity retention rate (relative value) of each non-aqueous electrolyte storage element was obtained as a relative value with the capacity retention rate of the non-aqueous electrolyte storage element of Reference Example 1 as a reference (100%). Table 1 shows these capacity retention rates (relative values).

Like the non-aqueous electrolyte storage elements of Reference Examples 1 to 4, the final discharge voltage was 3.50 V, and the positive electrode potential at this time was 3.69 V vs. In the case of Li/Li ⁺ , the capacity retention rate was almost the same regardless of the difference in the separator.
On the other hand, the discharge end voltage is 2.75 V, and the positive electrode potential at this time is 3.69 V vs. When the ratio is less than Li/Li ⁺ , the non-aqueous electrolyte storage elements of Comparative Examples 1 and ² using a separator having a membrane resistance of less than 2.5 Ω cm at 25° C. when impregnated with the non-aqueous electrolyte had a low capacity retention rate. On the other hand, the discharge end voltage is 2.75 V, and the positive electrode potential at this time is 3.69 V vs. When the ratio is less than Li/Li ⁺ , the non-aqueous electrolyte storage elements of Examples 1 and 2 using a separator having a membrane resistance of 2.5 Ω·cm or ^more at 25° C. when impregnated with the non-aqueous electrolyte had a high capacity retention rate. Among them, the non-aqueous electrolyte storage element of Example 2, which used a separator having a membrane resistance of 5.3 Ω·cm ² at 25° C. when impregnated with the non-aqueous electrolyte, had a particularly high capacity retention rate.

INDUSTRIAL APPLICABILITY The present invention can be applied to electronic devices such as personal computers and communication terminals, non-aqueous electrolyte storage elements used as power sources for automobiles and the like.

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

Claims (6)

The positive electrode potential at the discharge end voltage during normal use is 3.69 V vs. Li/Li ⁺ less than
a positive electrode containing a lithium transition metal composite oxide containing nickel element;
a non-aqueous electrolyte;
and a separator having a membrane resistance of 2.5 Ω·cm ² or more at 25° C. when impregnated with the non-aqueous electrolyte. 2. The non-aqueous electrolyte storage element according to claim 1, wherein the content ratio of the nickel element to the metal elements other than the lithium element in the lithium-transition metal composite oxide is 50 mol % or more. The positive electrode potential at the end of charge voltage during normal use is 4.30 V vs. 3. The non-aqueous electrolyte storage element according to claim 1, wherein Li/Li ⁺ or more. 4. The non-aqueous electrolyte storage element according to claim 1, wherein said separator has an inorganic particle layer. Equipped with a non-aqueous electrolyte storage element and a charge/discharge control device,
The non-aqueous electrolyte storage element is
a positive electrode containing a lithium transition metal composite oxide containing nickel element;
a non-aqueous electrolyte;
a separator having a membrane resistance of 2.5 Ω·cm ² or more at 25° C. when impregnated with the non-aqueous electrolyte;
In the charge/discharge control device, the positive electrode potential of the non-aqueous electrolyte storage element is 3.69 V vs. A device configured to discharge to less than Li/Li ⁺ . a positive electrode containing a lithium transition metal composite oxide containing nickel element;
a non-aqueous electrolyte;
The positive electrode potential of the non-aqueous electrolyte storage element is ^3.69 V vs. A method of using a non-aqueous electrolyte storage element comprising discharging to less than Li/Li ⁺ .

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