JP2022048657A - Power storage element - Google Patents

Abstract

To provide a power storage element in which a decrease in output after being left at high temperature is suppressed.SOLUTION: A power storage element includes an electrode having an active material layer containing active material particles, the active material layer contains hydrophilized non-graphitic carbon and does not contain a binder, and the content of the hydrophilized non-graphitic carbon is more than 4 mass%. Further, the active material layer contains particles of nickel-containing lithium transition metal composite oxide as the active material particles.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power storage element.

Patent Document 1 describes a positive electrode for a lithium ion secondary battery containing a conductive auxiliary agent, in which an acetylene black having a hydrophilic functional group on the surface is used as the conductive auxiliary agent, and the surface hydrophilic group ratio of the acetylene black is used. However, a positive electrode for a lithium ion secondary battery, which is 19.5% or more and 22.4% or less, is described.

JP-A-2015-176831

An object of the present invention is to provide a power storage element in which a decrease in output after being left at a high temperature is suppressed.

The power storage element according to one aspect of the present invention includes an electrode having an active material layer containing active material particles, and comprises an electrode.
The active material layer contains hydrophilized non-graphitable carbon and does not contain binder.

The power storage element according to one aspect of the present invention is suppressed from a decrease in output after being left at a high temperature.

FIG. 1 is a perspective view of a power storage element according to the present embodiment. FIG. 2 is a perspective view showing a state in which the outermost peripheral portion of the wound electrode body of the power storage element according to the present embodiment is stretched. FIG. 3 is a schematic view of a power storage device including a plurality of power storage elements according to the present embodiment.

First, an outline of the power storage element 1 disclosed by the present specification will be described.

The power storage element 1 according to one aspect of the present invention includes an electrode having an active material layer containing active material particles, and the active material layer contains hydrophilized non-graphitable carbon and does not contain a binder.

The power storage element 1 can suppress a decrease in output after being left at a high temperature.

Here, in the power storage element 1, the content of the hydrophilized non-graphitic carbon in the active material layer may be more than 4% by mass.

With this power storage element 1, it is possible to further suppress a decrease in output after being left at a high temperature.

Here, in the power storage element 1, the active material layer may contain particles of the nickel-containing lithium transition metal composite oxide as the active material particles.

With this power storage element 1, it is possible to further suppress a decrease in output after being left at a high temperature.

The configuration of the power storage element, the configuration of the power storage device, the method of manufacturing the power storage element, and other embodiments according to the embodiment of the present invention will be described in detail. 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 technology.

<Structure of power storage element>
The power storage element according to the embodiment of the present invention includes an electrode body 2 having a positive electrode 40, a negative electrode 50, and a separator 60, an electrolyte, and a case 3 containing the electrode body 2 and the electrolyte. The electrode body 2 is usually wound in a state where the positive electrode 40 and the negative electrode 50 are laminated via the separator 60, or a plurality of positive electrodes 40 and a plurality of negative electrodes 50 are laminated via the separator 60. It is a laminated type. The electrolyte is present in the positive electrode 40, the negative electrode 50 and the separator 60. Hereinafter, a non-aqueous electrolyte secondary battery (particularly, a lithium ion secondary battery, hereinafter also simply referred to as a “secondary battery”) will be described as an example of a power storage element, but there is no intention of limiting the application target of the present invention. ..

As shown in FIG. 1, the power storage element 1 of the present embodiment includes a wound electrode body 2 in a wound state and a case 3 accommodating the electrode body 2. Further, the power storage element 1 includes two external terminals (positive electrode terminal 4 and negative electrode terminal 5) that are attached to the case 3 with at least a part exposed or are composed of at least a part of the case 3. The electrode body 2 is connected to each of the external terminals 4 and 5 in the case 3 via a current collector or the like. The external terminals 4 and 5 are attached to the case 3. The case 3 has a flat rectangular parallelepiped shape, and has a case main body 31 that opens toward one side and a long and thin rectangular lid 32 that covers the opening of the case main body 31. The two external terminals 4 and 5 are arranged apart from each other in the long side direction of the lid 32.
In the power storage element 1 of the present embodiment, the electrode body 2 is housed in the case 3 so that the winding axis direction of the electrode body 2 is the same as the long side direction of the lid 32 of the case 3.

As shown in FIG. 2, the electrode body 2 is formed by stacking a long sheet-shaped positive electrode 40, a long sheet-shaped negative electrode 50, and two long sheet-shaped separators 60 and 60, and further winding the electrode body 2. Is formed. In other words, the electrode body 2 is formed by winding a strip-shaped laminate including a positive electrode 40, a negative electrode 50, and two separators 60 and 60. The two separators 60 and 60 are arranged so as to electrically insulate the positive electrode 40 and the negative electrode 50, respectively. In the present embodiment, the electrode body 2 is a flat wound body.

(Positive electrode)
The positive electrode 40 has a positive electrode base material 41 and a positive electrode active material layer 42 arranged directly on the positive electrode base material 41 or via an intermediate layer (not shown). In the present embodiment, the positive electrode active material layers 42 are laminated on both sides of the positive electrode base material 41.

The positive electrode base material 41 has conductivity. Whether or not it has "conductivity" is determined with a volume resistivity of ¹⁰⁷ Ω · cm measured in accordance with JIS-H-0505 (1975) as a threshold value. As the material of the positive electrode base material 41, 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 base material 41 include a foil and a vapor-deposited film, and the foil is preferable from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferable as the positive electrode base material 41. Examples of aluminum or aluminum alloy include A1085 and A3003 specified in JIS-H-4000 (2014).

The average thickness of the positive electrode substrate 41 is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, further 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 base material 41 in the above range, it is possible to increase the energy density per volume of the secondary battery while increasing the strength of the positive electrode base material 41.

The intermediate layer is a layer arranged between the positive electrode base material 41 and the positive electrode active material layer 42. The intermediate layer contains conductive particles such as carbon particles to reduce the contact resistance between the positive electrode base material 41 and the positive electrode active material layer 42. The composition of the intermediate layer is not particularly limited and includes, for example, a resin binder and conductive particles.

The positive electrode active material layer 42 contains a positive electrode active material. In the present embodiment, the positive electrode active material layer 42 preferably contains the positive electrode active material and the conductive agent. In this case, the conductive agent contains at least hydrophilized non-graphitic carbon, and the positive electrode active material layer 42 does not contain a binder (binder). The positive electrode active material layer 42 contains optional components such as a thickener and a filler, if necessary.

The positive electrode active material can be appropriately selected from known positive electrode active materials. As the positive electrode active material for a lithium ion secondary battery, a material capable of storing and releasing lithium ions is usually used. Examples of the positive electrode active material include a lithium transition metal composite oxide (a lithium transition metal composite oxide having an α-NaFeO type ₂ crystal structure or a spinel type crystal structure), a polyanion compound, a chalcogen compound, sulfur and the like. .. Examples of the lithium transition metal composite oxide having an α-NaFeO type ₂ crystal structure include Li [Li _x Ni _(1-x) ] O ₂ (0 ≦ x <0.5) and Li [Li _x Ni _γ Co ₍ 0 ≦ x <0.5). _1-x-γ )] O ₂ (0 ≦ x <0.5, 0 <γ <1), Li [Li _x Co _(1-x) ] O ₂ (0 ≦ x <0.5), Li [ Li _x Ni _γ Mn _(1-x-γ) ] O ₂ (0 ≦ x <0.5, 0 <γ <1), Li [Li _x Ni _γ Mn _β Co _(1-x-γ-β) ] O ₂ (0≤x <0.5, 0 <γ, 0 <β, 0.5 <γ + β <1), Li [Li _x Ni _γ Co _β Al _(1-x-γ-β) ] O ₂ ( Examples thereof include 0 ≦ x <0.5, 0 <γ, 0 <β, 0.5 <γ + β <1). Examples of the lithium transition metal composite oxide having a spinel-type crystal structure include LixMn ₂ O ₄ and Li _x Ni _γ Mn _(2-γ) O ₄ . Examples of the polyanionic compound include LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F and the like. Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, molybdenum dioxide and the like. The atoms or polyanions in these materials may be partially substituted with atoms or anion species consisting of other elements. The surface of these materials may be coated with other materials. In the positive electrode active material layer 42, one of these materials may be used alone, or two or more of them may be mixed and used.

In a preferred embodiment, the positive electrode active material is composed of the above lithium transition metal composite oxide containing Li and a transition metal. For example, as the above-mentioned lithium transition metal composite oxide, a nickel-containing lithium transition metal composite oxide containing at least lithium (Li) and nickel (Ni) as constituent elements is exemplified. Such composite oxides may have a layered α-NaFeO type ₂ crystal structure (ie, an X-ray diffraction pattern that can be attributed to the space group R3-m). Further, as the above-mentioned lithium transition metal composite oxide, a cobalt-containing lithium transition metal composite oxide containing at least lithium (Li) and cobalt (Co) as constituent elements is exemplified. Such composite oxides may have a layered α-NaFeO type ₂ crystal structure. Further, as the above-mentioned lithium transition metal composite oxide, a manganese-containing lithium transition metal composite oxide containing at least lithium (Li) and manganese (Mn) as constituent elements is exemplified. Such composite oxides may have a layered α-NaFeO type ₂ crystal structure or a spinel type crystal structure.

The positive electrode active material preferably contains the above-mentioned nickel-containing lithium transition metal composite oxide. By including the nickel-containing lithium transition metal composite oxide described above in the positive electrode active material, the dispersed state of the hydrophilized non-graphular carbon can be easily improved in the positive electrode active material layer 42. Therefore, it is possible to more sufficiently suppress a decrease in the output of the power storage element 1 after being left at a high temperature.

In the above nickel-containing lithium transition metal composite oxide, the molar ratio (Ni / Me) of nickel (Ni) to the total number of moles of the transition metal (Me) contained is not particularly limited. The molar ratio (Ni / Me) may be, for example, 10 mol% or more, preferably 20 mol% or more, and more preferably 30 mol% or more. By using a nickel-containing lithium transition metal composite oxide containing nickel in such a proportion, the effect of reducing the output of the power storage element 1 after being left at a high temperature can be more sufficiently exhibited. In some embodiments, the molar proportion (Ni / Me) associated with nickel may be 50 mol% or more, 60 mol% or more (eg 80 mol% or more). On the other hand, the above ratio (Ni / Me) may be, for example, 100 mol% or less, or 90 mol% or less. In some embodiments, the proportion (Ni / Me) may be 85 mol% or less, or 80 mol% or less (eg, 60 mol% or less).

The nickel-containing lithium transition metal composite oxide preferably further contains at least one of manganese and cobalt as a transition metal, and more preferably contains both manganese and cobalt. More preferred examples include layered nickel cobalt manganese-containing lithium transition metal composite oxides (NCMs) containing cobalt and manganese as constituent elements in addition to lithium and nickel. In such NCM, the molar ratio (Ni / Me) related to nickel is contained as the molar ratio (Mn / Me) of manganese (Mn) to the total number of moles of the transition metal (Me) contained. An NCM having a larger molar ratio (Co / Me) of cobalt (Co) to the total number of moles of the transition metal (Me), or an NCM containing Ni, Co, and Mn in substantially the same ratio is preferable.

As a suitable example of the nickel-containing lithium transition metal composite oxide described above, for example, the composite oxide represented by the following composition formula (1) is exemplified.
Li _x Ni _a Co _b Mn _c M _{d Oe} Composition formula (1)
[In the composition formula (1), M is at least one element selected from elements other than Li, Ni, Co and Mn, and is 0 <x≤1.3, a + b + c + d = 1, 0 <a≤1. , 0 ≦ b <1, 0 ≦ c <1, 0 ≦ d <1, and 1.7 ≦ e ≦ 2.3 are satisfied. ]

Specifically, in the above composition formula (1), M is selected from the group consisting of, for example, Al, Mg, Zr, W, Ti, Ca, K, Na, Si, B, F, Bi, Er, and Lu. It is one kind or two or more kinds of elements. Of these, as M, any one of Al, B, Zr, W, and Ti, or a combination of two or more thereof is preferable. Further, in the composition formula (1), x is preferably 1 or more, and may be 1. From the viewpoint of more sufficiently suppressing the output decrease of the power storage element 1, a is preferably 0.3 or more, more preferably 1/3 or more. Further, a may be less than 1, preferably 0.9 or less, and more preferably 0.8 or less. In some embodiments, a may be, for example, 0.6 or less, or 0.5 or less. b is preferably more than 0, more preferably 0.05 or more. In some embodiments, b may be 0.1 or greater, 0.2 or greater, or 0.3 or greater. Further, b is preferably less than 1, more preferably 0.5 or less. In some embodiments, b may be 1/3 or less, 0.2 or less, or 0.1 or less. c is preferably more than 0, more preferably 0.05 or more. In some embodiments, c may be 0.1 or greater, 0.2 or greater, or 0.3 or greater. Further, c is preferably less than 1, more preferably 0.5 or less. In some embodiments, c may be 1/3 or less, 0.2 or less, or 0.1 or less. d is preferably 0.1 or less, and may be substantially 0. e is a value determined within the range of 1.7 ≦ e ≦ 2.3 so as to satisfy the charge neutrality condition, and may be substantially 2.

The property of the positive electrode active material is a powder composed of particles before being blended in the mixture composition for the positive electrode active material layer. The positive electrode active material typically includes secondary particles formed by aggregating primary particles. The active material particles of the positive electrode 40 may have a hollow structure in which voids are formed inside the secondary particles in which the primary particles are aggregated. Since the active material particles of the positive electrode 40 have the above-mentioned hollow structure, the hydrophilized non-graphitic carbon enters the voids (typically, the hollow portion) of the secondary particles. As a result, the above-mentioned performance improving effect (for example, the effect of suppressing the output decrease of the power storage element after being left at a high temperature) can be more effectively exhibited. The average particle size D1 of the active material particles of the positive electrode 40 is preferably 0.1 μm or more and 20 μm or less, for example. The average particle size D1 of the positive electrode active material particles is more preferably 0.5 μm or more, further preferably 0.8 μm or more, and particularly preferably 1 μm or more (for example, 3 μm or more). The average particle size D1 of the positive electrode active material particles is more preferably 15 μm or less, further preferably 10 μm or less, and particularly preferably 5 μm or less. When the average particle size D1 of the positive electrode active material particles is within the above range, the performance improving effect (for example, the effect of suppressing the output decrease of the power storage element after being left at a high temperature) by the hydrophilized non-graphitic carbon is further improved. It can be fully demonstrated. Further, by setting the average particle size D1 of the active material particles of the positive electrode 40 to be equal to or higher than the above lower limit, the production or handling of the positive electrode active material becomes easier. By setting the average particle size D1 of the active material particles of the positive electrode 40 to be equal to or less than the above upper limit, the electron conductivity of the positive electrode active material layer 42 is further improved. When a composite of the positive electrode active material and another material is blended in the positive electrode active material layer 42, the average particle size of the composite is defined as the average particle size D1 of the active material particles. The "average particle size D1" is based on JIS-Z-8825 (2013), and is based on the particle size distribution measured by the laser diffraction / scattering method for a diluted solution obtained by diluting the particles with a solvent. It means a value at which the volume-based integrated distribution calculated according to 8819-2 (2001) is 50%.

A crusher, a classifier, or the like is used to obtain a powder containing particles having a predetermined particle size. Examples of the crushing method include a method using a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve, or the like. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. As a classification method, a sieve, a wind power classifier, or the like is used as needed for both dry type and wet type.

The content of the positive electrode active material in the positive electrode active material layer 42 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 80% by mass or more and 96% by mass or less (for example, 85% by mass). More than 95% by mass or less) is more preferable. By setting the content of the positive electrode active material within the above range, it is possible to achieve both high energy density and ease of manufacture of the positive electrode active material layer 42.

In the present embodiment, the positive electrode active material layer 42 does not contain a binder and contains hydrophilized non-graphitable carbon as a conductive agent. In addition, "does not contain binder" means that the content of the binder in the positive electrode active material layer 42 is less than 3000 ppm (less than 0.3% by mass).

The above binder is a conventionally known component (for example, a resin component) generally used in the positive electrode active material layer of a conventional power storage element. Specific examples of the binder include, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylene-tetrafluoro. Ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid modified SBR, ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, fluororubber, arabic rubber, polyvinylidene fluoride (PVDF) ), Polyvinylidene chloride (PVDC), polyethylene (PE), polypropylene (PP), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide-propylene oxide copolymer (PEO-PPO) and the like. In the positive electrode active material layer of the conventional power storage element, these binders bind the positive electrode active materials to each other via the binder, but swell by the non-aqueous electrolyte at a high temperature and act as a component capable of increasing the electric resistance. Therefore, it can be a factor that limits the decrease in electrical resistance. Further, these binders may be unevenly distributed due to migration during the production of the positive electrode and cause non-uniformity of the charge / discharge reaction, which may be a factor of causing deterioration.

On the other hand, in the power storage element 1 of the present embodiment, since the positive electrode active material layer 42 does not contain the binder, it is possible to prevent the binder from swelling due to the non-aqueous electrolyte at a high temperature and eliminating the electrical contact between the active material particles. can. Further, since the positive electrode active material layer 42 contains the hydrophilized non-graphitable carbon, the hydrophilized non-graphitable carbon acts as a substitute for the binder and causes electrical contact between the active material particles even at high temperatures. Can be maintained. Further, in the power storage element 1 of the present embodiment, as compared with the power storage element containing a binder in the positive electrode active material layer, non-uniformity of the charge / discharge reaction due to uneven distribution of the binder and deterioration due to the non-uniformity occur. It becomes difficult. Therefore, it is possible to suppress an increase in resistance in the positive electrode active material layer 42 even at a high temperature. As a result, it is possible to suppress a decrease in the output of the power storage element 1 after being left at a high temperature.

The hydrophilized non-graphitic carbon is a carbonaceous material other than graphite and is a hydrophilized carbonaceous material. The hydrophilization treatment is a treatment for increasing the surface free energy (increasing the wettability). Examples of the hydrophilic non-graphitic carbon include amorphous carbon (amorphous carbon), non-graphitizable carbon (hard carbon), easily graphitizable carbon (soft carbon), carbon black, and carbon fiber (carbon fiber). ) Etc., each of which has been subjected to a hydrophilization treatment. As the non-graphitic carbon, carbon black is preferable. Since these non-graphitic carbons have lower crystallinity than graphite, they have appropriate flexibility. Therefore, even if the positive electrode 40 repeatedly expands and contracts due to charging and discharging, the shape of the positive electrode 40 can be appropriately maintained. Examples of the non-graphic carbon include resin-derived carbonaceous materials, petroleum pitch-derived carbonaceous materials, petroleum coke, petroleum coke-derived carbonaceous materials, plant-derived carbonaceous materials, alcohol-derived carbonaceous materials, and the like. Can be mentioned.

It is preferable that hydrophilic functional groups are present on the surface of the hydrophilized non-graphitic carbon. Examples of the hydrophilic functional group include a functional group containing oxygen (O), specifically, an acidic functional group containing -OH,> C = O, or the like. Examples of the acidic functional group containing -OH include a hydroxy group, a sulfo group, a phenol group and the like. Examples of the acidic functional group containing> C = O include a lactone group, an aldehyde group, a ketone group and the like. Examples of the acidic functional group containing both -OH and> C = O include a carboxy group. Of these acidic functional groups, a carboxy group, a ketone group, a hydroxy group and a sulfo group are preferable, and a carboxy group and a hydroxy group are particularly preferable. This kind of hydrophilic functional group and a functional group such as a hydroxyl group existing on the surface of the positive electrode active material can be dehydrated and condensed to be bonded. As a result, the positive electrode active materials can be firmly bonded to each other via the non-graphitic carbon without using a binder, and the positive electrode active material can be firmly bonded to the positive electrode base material 41 via the non-graphitable carbon. Can be tied to.

In a preferred embodiment, the acidic functional group present on the surface of the hydrophilized non-graphitic carbon comprises a carboxy group. When carboxy groups are present on the surface of the hydrophilized non-graphitable carbon particles, more carboxy groups are anionized (-COO- ⁾ by placing the particles in a stronger alkaline environment. This increases the electrostatic repulsive force between the hydrophilized non-graphitable carbon particles. For example, when the above-mentioned nickel-containing lithium transition metal composite oxide is used as a positive electrode active material to prepare a mixture composition for a positive electrode, the mixture composition is based on the carboxy group present on the particle surface of non-graphitic carbon. , Tends to be alkaline. When this mixture composition is applied onto the positive electrode base material 41 to prepare the positive electrode active material layer 42, the electrostatic repulsive force between the hydrophilized non-graphitic carbon particles increases. As a result, at least the aggregation of the non-graphitic carbon particles is suppressed, the particles are more sufficiently dispersed, and as a result, the positive electrode active material layer 42 having a good dispersed state can be formed. Since the output performance of the power storage element 1 can be improved by the amount that the positive electrode active material layer 42 is in a good dispersed state, it is possible to further suppress a decrease in the output of the power storage element 1 after being left at a high temperature.
When the acidic functional group existing on the surface of the hydrophilic non-graphitable carbon particles contains a hydroxy group, the aggregation of the non-graphitable carbon particles is similarly suppressed, and the particles are more sufficient. As a result, the positive electrode active material layer 42 having a good dispersed state can be formed.

In the present embodiment, the hydrophilized non-graphitable carbon preferably has a physical property such that the amount of hydrophilic functional groups per unit mass of the non-graphitable carbon based on neutralization titration is 100 μmol / g or more. By blending such hydrophilized non-graphite carbon into the positive electrode active material layer 42, the positive electrode active materials can be made stronger with each other through the hydrophilized non-graphitable carbon without using a binder. Can be tied. From the viewpoint of binding more firmly, the amount of the hydrophilic functional group is preferably 200 μmol / g or more, more preferably 300 μmol / g or more, still more preferably 400 μmol / g or more. .. In some embodiments, the amount of the above hydrophilic functional groups may be 500 μmol / g or more, or 800 μmol / g or more (eg, 1000 μmol / g or more). The upper limit of the amount of the above hydrophilic functional groups is not particularly limited. From the viewpoint of ease of production, handleability at the time of producing the positive electrode active material layer 42, and the like, the upper limit of the amount of the above hydrophilic functional groups is preferably 2000 μmol / g or less, preferably 1800 μmol / g. It is g or less, more preferably 1500 μmol / g or less. In some embodiments, the amount of the above hydrophilic functional groups may be 1300 μmol / g or less, or 1200 μmol / g or less.

The above neutralization titration is carried out as follows. Specifically, a predetermined amount (for example, 2 g) of hydrophilized non-graphic carbon is dispersed in an aqueous solution of sodium hydrogen carbonate (for example, 0.5 L of an aqueous solution of sodium hydrogen carbonate having a concentration of 0.976 mol / L). After shaking the dispersion for 6 hours, the hydrophilized non-graphitic carbon is separated by filtration. The filtrate is neutralized and titrated with an aqueous solution of sodium hydroxide (for example, an aqueous solution of sodium hydroxide having a concentration of 0.05 mol / L), and based on the titration up to the neutralization point near pH 8, the hydrophilized non-gelatinous carbon The amount of hydrophilic functional groups (μmol / g) per unit mass can be calculated.

In the present embodiment, the hydrophilized non-graphitic carbon preferably has a physical property value determined by the following measuring method. Specifically, 50 mg of non-graphitic carbon is dispersed in ion-exchanged water (for example, an amount of 15 mL) to prepare a slurry. The pH of the slurry is measured at room temperature (for example, 25 ° C.) with a commercially available pH meter (for example, product name “D-23” manufactured by HORIBA, Ltd.). The measured value is preferably 2.0 or more and 7.5 or less. The pH of the slurry is preferably 2.2 or more and 7.2 or less, more preferably 2 from the viewpoint of further exerting the effect of suppressing a decrease in the output of the power storage element 1 after being left at a high temperature. It is 5.5 or more and 7.0 or less, and more preferably 2.8 or more and 6.6 or less.

The shape of the hydrophilized non-graphite carbon is not particularly limited. Examples of the shape include a spherical shape, a deformed spherical shape, a lump shape, a flaky shape, a fibrous shape, and an irregular shape. The average particle size D2 (average primary particle size) of such non-graphitic carbon particles is preferably 30 nm or more. From the viewpoint of suppressing aggregation of non-graphitic carbon particles, the average particle size D2 is preferably 50 μm or more, more preferably 80 μm or more, and further preferably 100 μm or more. It is appropriate that the upper limit of the average particle size D2 is 300 nm or less. From the viewpoint of more exerting the function as a binder, the average particle size D2 is preferably 200 nm or less, more preferably 150 nm or less, and further preferably 120 nm or less. The above average particle size D2 can be measured, for example, by observation with an electron microscope. Specifically, the cut surface in the thickness direction of the positive electrode active material layer 42 is observed with an electron microscope, and the particle diameters of at least 100 particles (for example, a predetermined number of 100 to 1000 particles) are measured and averaged. The above average particle size D2 is measured. The particle diameter is the diameter of the smallest circle (perfect circle) circumscribing so as to surround each particle in the observation image.

In a preferred embodiment, at least a portion of the hydrophilized non-graphite carbon particles is in contact with at least a portion of the positive electrode active material particles. In other words, at least a portion of the surface of the plurality of positive electrode active material particles is each coated with hydrophilic non-graphitable carbon particles. One non-graphite carbon particle may be in contact with one positive electrode active material particle, or a plurality of non-graphite carbon particles may be in contact with each other. Based on the above observation results by an electron microscope, as an average value in the positive electrode active material layer 42, 20% or more of the surface of the positive electrode active material particles is covered with hydrophilic non-graphitable carbon particles. preferable. The coverage, which is the ratio of the area covered with the hydrophilic non-graphitable carbon particles to the total surface area of the positive electrode active material particles, is preferably 30% or more, more preferably 40% or more, still more preferably 50%. That is all. In this way, more of the surface of the positive electrode active material particles is coated with the hydrophilized non-graphic carbon particles, so that the positive electrode active material particles pass through the hydrophilized non-graphic carbon particles. Can be more firmly bound to each other, and the positive electrode active material particles can be firmly bound to each other by the positive electrode base material 41.

In a preferred embodiment, in the positive electrode active material layer 42, the mass ratio of the hydrophilized non-graphitic carbon to the positive electrode active material may be, for example, 0.01 or more and 0.20 or less. Such a mass ratio is preferably 0.03 or more, and more preferably 0.05 or more. Further, such a mass ratio is preferably 0.15 or less, and more preferably 0.10 or less. When the mass ratio is in the above numerical range, the above-mentioned effect that the positive electrode active material particles can be firmly bonded to each other via the hydrophilized non-graphitable carbon can be more sufficiently exhibited. ..

The relationship between the average particle size D1 of the positive electrode active material particles and the average particle size D2 of the hydrophilized non-graphic carbon particles from the viewpoint of more fully exerting the above-mentioned effect of binding the positive electrode active material particles. However, it is preferable that 0.01 ≦ (D2 / D1) ≦ 0.05 is satisfied. By using the positive electrode active material particles in combination with the hydrophilic non-graphitable carbon particles at a specific particle size ratio satisfying the above relationship, the positive electrode active material via the above-mentioned non-graphitable carbon particles is used. A positive electrode 40 in which the particles are strongly bonded to each other and the positive electrode active material layer 42 is not easily peeled off from the positive electrode base material 41 can be realized without blending a binder. The relationship between the average particle size D1 of the positive electrode active material particles and the average particle size D2 of the non-graphic carbon particles is preferably 0.015 ≦ (D2 / D1) ≦ 0.04, and more preferably 0. 02 ≦ (D2 / D1) ≦ 0.035, more preferably 0.025 ≦ (D2 / D1) ≦ 0.03.

The hydrophilized non-graphitic carbon can be produced as follows. The hydrophilic treatment for increasing the hydrophilicity of the non-graphitic carbon is not particularly limited, but typically a conventionally known hydrophilic treatment such as a hydrophilic treatment for introducing a hydrophilic functional group into the particle surface is adopted. Examples of the hydrophilization treatment method include a method of oxidizing non-graphitable carbon with an acidic solution (a solution containing an acid and an oxidizing agent), a method of plasma-treating non-graphitable carbon, and the like. The method for plasma-treating non-graphic carbon is, for example, a chemical species containing oxygen (for example, oxygen gas (O ₂ ), ozone (O ₃ ), oxide ion (O ^2- ), oxygen radical, oxygen plasma, etc.). May be a treatment method for supplying non-polar carbon.
As the hydrophilized non-graphitic carbon, a commercially available product can also be used.

The content of the hydrophilized non-graphitic carbon in the positive electrode active material layer 42 is not particularly limited, but may be more than 4% by mass, may be 4.5% by mass or more, and may be 4.7. It may be mass% or more. In some embodiments, the non-graphitable carbon content may be, for example, 6% by weight or more, or 8% by weight or more. Such a content may be 20% by mass or less, or may be 15% by mass or less. In some embodiments, the non-graphitable carbon content may be, for example, 12% by weight or less, or 10% by weight or less.
Since the content of the hydrophilized non-graphitic carbon is more than 4% by mass, a binderless positive electrode containing no binder in the positive electrode active material layer 42 can be suitably realized, and the storage capacity after being left at a high temperature is stored. The decrease in the output of the element 1 can be further suppressed.

The positive electrode active material layer 42 may further contain a conductive agent other than the hydrophilized non-graphitic carbon (hereinafter, also referred to as another conductive agent).
The other conductive agent is not particularly limited as long as it is a conductive material. Examples of such a conductive agent include specific carbonaceous materials, metals, conductive ceramics and the like. Examples of the carbonaceous material include graphite, non-graphitic carbon that has not been hydrophilized, graphene-based carbon, and the like. Examples of the 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 fullerenes. Examples of the shape of the conductive agent include a spherical shape and a fibrous shape. As the conductive agent, one of these materials may be used alone, or two or more thereof may be mixed and used. Further, these materials may be combined and used. For example, a material in which CNT and non-hydrophilic carbon black are combined may be used. Among these, as the other conductive agent, carbon black which is not hydrophilized is preferable, and acetylene black which is not hydrophilized is preferable, from the viewpoint of electron conductivity and coatability.

The content of the other conductive agent in the positive electrode active material layer 42 (total amount of the conductive agent excluding the hydrophilized non-graphitic carbon) is preferably 10% by mass or less, more preferably 9% by mass or less. When the content of the other conductive agent is in the above range, the energy density of the secondary battery can be further increased. An embodiment in which the positive electrode active material layer 42 does not contain a conductive agent other than hydrophilized non-graphitable carbon is preferable in the present embodiment.

Examples of the thickener that can be blended in the positive electrode active material layer 42 include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, this functional group may be inactivated by methylation or the like in advance. When a thickener is used, the content of the thickener in the positive electrode active material layer 42 is preferably 8% by mass or less, more preferably 5% by mass or less. The technique disclosed herein can be preferably carried out in a manner in which the positive electrode active material layer 42 does not contain the thickener.

The filler that can be blended in the positive electrode active material layer 42 is not particularly limited. Fillers include polyolefins such as polypropylene and polyethylene, silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, inorganic oxides such as aluminosilicate, magnesium hydroxide, calcium hydroxide, and hydroxide. Hydroxides such as aluminum, carbonates such as calcium carbonate, sparingly soluble ion crystals such as calcium fluoride, barium fluoride, barium sulfate, nitrides such as aluminum nitride and silicon nitride, talc, montmorillonite, boehmite, zeolite, etc. Examples include mineral resource-derived substances such as apatite, kaolin, mulite, spinel, olivine, sericite, bentonite, and mica, or man-made products thereof. When a filler is used, the content of the filler in the positive electrode active material layer 42 is preferably 8% by mass or less, more preferably 5% by mass or less. The technique disclosed herein can be preferably carried out in a manner in which the positive electrode active material layer 42 does not contain the above filler.

The positive electrode active material layer 42 contains substances containing typical non-metal elements such as B, N, P, F, Cl, Br, and I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, and the like. A substance containing a typical metal element such as Sr and Ba, or a substance containing a transition metal element such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb and W is used as a positive electrode. It may be contained as a component other than an active material, a conductive agent, a thickener, and a filler.

The density of the positive electrode active material layer 42 is not particularly limited, but is preferably 1.5 g / cm ³ or more and 5.0 g / cm ³ or less, preferably 1.8 g / cm ³ or more and 4.0 g / cm. It is ³ or less, more preferably 2.0 g / cm ³ or more and 3.5 g / cm ³ or less. In some embodiments, the density of the positive electrode active material layer 42 may be 2.4 g / cm ³ or more and 3.2 g / cm ³ or less, 2.7 g / cm ³ or more and 3.0 g / cm ³ or less. There may be. A power storage element 1 having a positive electrode active material layer 42 having a density within such a range can more sufficiently suppress a decrease in output after being left at a high temperature.

Thickness of the positive electrode active material layer 42 (when the positive electrode active material layer is formed on both sides of the positive electrode base material 41, the thickness of only the positive electrode active material layer 42 arranged on one side of the positive electrode base material 41) Is not particularly limited, but is preferably 15 μm or more and 200 μm or less, preferably 20 μm or more and 150 μm or less, and more preferably 25 μm or more and 100 μm or less. In some embodiments, the thickness of the positive electrode active material layer 42 may be 28 μm or more and 80 μm or less, or 30 μm or more and 50 μm or less. A power storage element 1 having a positive electrode active material layer 42 having a thickness within such a range can more sufficiently suppress a decrease in output after being left at a high temperature.

(Negative electrode)
The negative electrode 50 has a negative electrode base material 51 and a negative electrode active material layer 52 arranged directly on the negative electrode base material 51 or via an intermediate layer (not shown). The configuration of the intermediate layer is not particularly limited, and can be selected from, for example, the configurations exemplified by the positive electrode 40. In the present embodiment, the negative electrode active material layers 52 are laminated on both surfaces of the negative electrode base material 51.

The negative electrode base material 51 has conductivity. As the material of the negative electrode base material 51, metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof are used. Among these, copper or a copper alloy is preferable. Examples of the negative electrode base material 51 include a foil and a vapor-deposited film, and the foil is preferable from the viewpoint of cost. Therefore, a copper foil or a copper alloy foil is preferable as the negative electrode base material 51. Examples of the copper foil include rolled copper foil, electrolytic copper foil and the like.

The average thickness of the negative electrode base material 51 is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, further 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 base material 51 in the above range, it is possible to increase the strength of the negative electrode base material 51 and the energy density per volume of the secondary battery.

The negative electrode active material layer 52 contains a negative electrode active material. The negative electrode active material layer 52 contains optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary. Optional components such as a conductive agent, a thickener, and a filler can be selected from the materials exemplified by the positive electrode 40. Further, in the present embodiment, the negative electrode active material layer 52 may contain the negative electrode active material and the conductive agent. In this case, the conductive agent may contain at least hydrophilized non-graphitic carbon, and the negative electrode active material layer 52 may not contain a binder.

Examples of the binder that can be contained in the negative electrode active material layer 52 include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and thermoplastic resins such as polyimide; ethylene. -Ethylene propylene-diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber and other elastomers; polysaccharide polymers and the like can be mentioned.

When the binder is blended in the negative electrode active material layer 52, it is preferable to use an aqueous binder such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, and styrene-butadiene rubber (SBR). The binder content in the negative electrode active material layer 52 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. By setting the binder content within the above range, the active substance can be stably retained.

When a thickener is used in the negative electrode active material layer 52, the content of the thickener in the negative electrode active material layer 52 is preferably 0.5% by mass or more and 8% by mass or less, preferably 1% by mass or more and 5% by mass or less. More preferred. When a conductive agent is used, the content of the conductive agent in the negative electrode active material layer 52 is preferably 8% by mass or less, more preferably 5% by mass or less. The technique disclosed herein can be preferably carried out in a manner in which the negative electrode active material layer 52 does not contain the above-mentioned conductive agent. When a filler is used, the content of the filler in the negative electrode active material layer 52 is preferably 8% by mass or less, more preferably 5% by mass or less. The technique disclosed herein can be preferably carried out in a manner in which the negative electrode active material layer 52 does not contain the above filler.

The negative electrode active material layer 52 includes typical non-metal elements such as B, N, P, F, Cl, Br, and I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba. , Etc., transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W, etc. , May be contained as a component other than a thickener and a filler.

The negative electrode active material can be appropriately selected from known negative electrode active materials. As the negative electrode active material for a lithium ion secondary battery, a material capable of storing and releasing lithium ions is usually used. Examples of the negative electrode active material include metal Li; metal or semi-metal such as Si and Sn; metal oxide or semi-metal oxide such as Si oxide, Ti oxide and Sn oxide; Li ₄ Ti _{5 O12} , Titanium-containing oxides such as _{LiTIO 2} and TiNb ₂ O7; polyphosphate compounds; silicon carbide; carbonaceous materials such as graphite (graphite) and non-graphitable carbon (easy graphitable carbon or non-graphitizable carbon) Can be mentioned. Among these materials, graphite and non-graphitic carbon are preferable. In the negative electrode active material layer 52, one of these materials may be used alone, or two or more of them may be mixed and used.

"Graphite" refers to a carbonaceous material having an average lattice spacing (d ₀₀₂ ) of (002) planes 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. .. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferable from the viewpoint that a material having stable physical properties can be obtained.

"Non-graphitic carbon" is a carbonaceous 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 0.34 nm or more and 0.42 nm or less. To say. Examples of non-graphitizable carbon include non-graphitizable carbon and easily graphitizable carbon. Examples of the non-graphitic carbon include a resin-derived material, a petroleum pitch-derived material, a petroleum coke or a petroleum coke-derived material, a plant-derived material, an alcohol-derived material, and the like.

Here, the "discharged state" means a state in which the open circuit voltage is 0.7 V or more in a single-pole battery using a negative electrode containing a carbonaceous material as a negative electrode active material as a working electrode and metal Li as a counter electrode. .. Since the potential of the metal Li counter electrode in the open circuit state is almost equal to the redox potential of Li, the open circuit voltage in the single pole battery is almost the same as the potential of the negative electrode containing the carbonaceous material with respect to the redox potential of Li. be. That is, the fact that the open circuit voltage in the single-pole battery is 0.7 V or more means that lithium ions that can be occluded and discharged are sufficiently released from the carbonaceous material that is the negative electrode active material. do.

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

The “graphitizable carbon” refers to a carbonaceous material in which _d002 is 0.34 nm or more and less than 0.36 nm.

The negative electrode active material is usually in the form of particles (powder containing particles). 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 carbonaceous material, a titanium-containing oxide or a polyphosphate compound, the average particle size thereof 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 thereof may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or higher than the above lower limit, the production or handling of the negative electrode active material becomes easy. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electron conductivity of the active material layer is improved. A crusher, a classifier, or the like is used to obtain a powder containing particles having a predetermined particle size. The pulverization method and the powder grade method can be selected from, for example, the methods exemplified for the positive electrode 40. When the negative electrode active material is a metal such as metal Li, the negative electrode active material may be in the form of a foil.

The content of the negative electrode active material in the negative electrode active material layer 52 is preferably 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. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and ease of manufacture of the negative electrode active material layer 52.

(Separator)
The separator 60 can be appropriately selected from known separators. As the separator 60, for example, a separator composed of only a base material layer, a separator having a heat-resistant layer containing heat-resistant particles and a binder formed on one surface or both surfaces of the base material layer can be used. Examples of the form of the base material layer of the separator 60 include woven fabrics, non-woven fabrics, and porous resin films. Among these, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of liquid retention of a non-aqueous electrolyte. As the material of the base material layer of the separator 60, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of shutdown function, and polyimide and aramid are preferable from the viewpoint of oxidative decomposition resistance. As the base material layer of the separator 60, a material in which these resins are combined may be used.

The heat-resistant particles contained in the heat-resistant layer preferably have a mass loss of 5% or less when heated from room temperature to 500 ° C. in an air atmosphere of 1 atm, and are heated from room temperature to 800 ° C. in an air atmosphere of 1 atm. It is more preferable that the mass reduction is 5% or less. Inorganic compounds can be mentioned as materials whose mass reduction is less than or equal to a predetermined value. Examples of the inorganic compound include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide and aluminosilicate; magnesium hydroxide and water. Hydroxides such as calcium oxide and aluminum hydroxide; Nitridees such as aluminum nitride and silicon nitride; Carbonates such as calcium carbonate; Sulfates such as barium sulfate; Slowly soluble ion crystals such as calcium fluoride and barium fluoride Covalently bonded crystals such as silicon and diamond; talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mulite, spinel, olivine, sericite, bentonite, mica and other mineral resource-derived substances or man-made products thereof. .. As the inorganic compound, a simple substance or a complex of these substances may be used alone, or two or more kinds thereof may be mixed and used. Among these inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate is preferable from the viewpoint of safety of the power storage element 1.

The porosity of the separator 60 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" is a volume-based value and means a measured value with a mercury porosity meter.

As the separator 60, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyvinylidene fluoride and the like. The use of polymer gel has the effect of suppressing liquid leakage. As the separator 60, a polymer gel may be used in combination with the porous resin film or non-woven fabric as described above.

(Non-water electrolyte)
As the non-aqueous electrolyte, a known non-aqueous electrolyte can be appropriately selected. A non-aqueous electrolyte solution may be used as the non-aqueous electrolyte. The non-aqueous electrolyte solution contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

As the non-aqueous solvent, a known non-aqueous solvent can be appropriately selected. Examples of the non-aqueous solvent 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, a solvent in which some of the hydrogen atoms contained in these compounds are replaced with halogen may be used.

Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), and difluoroethylene carbonate. (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate and the like can be mentioned. Among these, PC is preferable.

Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diphenyl carbonate, trifluoroethylmethyl carbonate, bis (trifluoroethyl) carbonate and the like. Among these, DMC and EMC are preferable.

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

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

Lithium salts include inorganic lithium salts such as LiPF ₆ , LiPO ₂ F ₂ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ F) ₂ , LiSO ₃ CF ₃ , 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 ), LiC (SO ₂ CF ₃ ) ₃ , LiC (SO ₂ C ₂ F ₅ ) ₃ and other halogenated hydrocarbon groups Examples thereof include lithium salts having. Among these, an inorganic lithium salt is preferable, and LiPF ₆ is more preferable.

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

The non-aqueous electrolyte solution may contain additives in addition to the non-aqueous solvent and the electrolyte salt. Examples of the additive include halogenated carbonate esters such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC); lithium bis (oxalate) borate (LiBOB), lithium difluorooxalate borate (LiFOB), and lithium bis (oxalate). ) Sulfonic acid ester such as difluorophosphate (LiFOP); imide salt such as lithium bis (fluorosulfonyl) imide (LiFSI); biphenyl, alkylbiphenyl, terphenyl, partially hydride of terphenyl, cyclohexylbenzene, t-butylbenzene , T-Amilbenzene, diphenyl ether, dibenzofuran and other aromatic compounds; partial halides of the aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2 , 5-Difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and other halogenated anisole compounds; vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, anhydrous. Citraconic acid, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic acid anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sulton, propensulton, butane sulton, methyl methanesulphonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, sulfate Ester, Sulfonide, Dimethyl Sulfonide, Diethyl Sulfonide, Dimethyl Sulfoxide, Diethyl Sulfoxide, Tetramethylene Sulfoxide, Diphenyl Sulfate, 4,4'-Bis (2,2-Dioxo-1,3,2-Dioxathiolane), 4-Methylsulfonyloxy Methyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyldisulfide, dipyridinium disulfide, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetrakistrimethylsilyl titanate, lithium monofluorophosphate , Lithium difluorophosphate and the like. These additives may be used alone or in combination of two or more.

The content of the additive contained in the non-aqueous electrolytic solution is preferably 0.01% by mass or more and 10% by mass or less, and is 0.1% by mass or more and 7% by mass or less with respect to the total mass of the non-aqueous electrolytic solution. It is more preferable to have it, 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 in the above range, it is possible to improve the capacity maintenance performance or charge / discharge cycle performance after high temperature storage, and further improve the safety.

As the non-aqueous electrolyte, a solid electrolyte may be used, or a non-aqueous electrolyte solution and a solid electrolyte may be used in combination.

The solid electrolyte can be selected from any material having ionic conductivity such as lithium, sodium and calcium and being solid at room temperature (for example, 15 ° C to 25 ° C). Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, polymer solid electrolytes and the like.

Examples of the lithium ion secondary battery include Li ₂ SP ₂ S _{5, Li I-Li 2 SP 2 S 5 , Li 10 Ge} -P ₂ S ₁₂ and the like as the sulfide solid electrolyte.

The shape of the power storage element 1 of the present embodiment is not particularly limited, and examples thereof include a cylindrical battery, a square battery, a flat battery, a coin battery, and a button battery.
FIG. 1 shows a power storage element 1 as an example of a square battery. The figure is a perspective view of the inside of the case 3. The electrode body 2 having the positive electrode 40 and the negative electrode 50 wound around the separator 60 is housed in the square case 3. The positive electrode 40 is electrically connected to the positive electrode terminal 4 via the positive electrode lead 45. The negative electrode 50 is electrically connected to the negative electrode terminal 5 via the negative electrode lead 55.

<Structure of non-aqueous electrolyte power storage device>
The power storage element 1 of the present embodiment is used as a power source for automobiles such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV), a power source for electronic devices such as a personal computer and a communication terminal, or a power storage device. It can be mounted on a power source or the like as a power storage unit 10 (battery module) composed of a plurality of power storage elements 1 assembled together. In this case, the technique of the present invention may be applied to at least one power storage element 1 included in the power storage device.
FIG. 3 shows an example of a power storage device 100 in which a power storage unit 10 in which two or more electrically connected power storage elements 1 are assembled is further assembled. The power storage device 100 may include a bus bar (not shown) for electrically connecting two or more power storage elements 1, a bus bar (not shown) for electrically connecting two or more power storage units 10. The power storage unit 10 or the power storage device 100 may include a state monitoring device (not shown) for monitoring the state of one or more power storage elements 1.

<Manufacturing method of power storage element>
The method for manufacturing the power storage element 1 of the present embodiment can be appropriately selected from known methods. The manufacturing method includes, for example, preparing an electrode body 2, preparing an electrolyte, and accommodating the electrode body 2 and the electrolyte in a case 3 to assemble a power storage element. To prepare the electrode body 2, the positive electrode 40 is manufactured, the negative electrode 50 is manufactured, the positive electrode 40 and the negative electrode 50 are laminated via the separator 60, and the electrode body 2 is further wound as necessary. To prepare for forming.

In the preparation of the electrode body 2, in preparing the positive electrode 40, water, a positive electrode active material, and hydrophilized non-graphular carbon are preferably used by using a water-containing solvent containing water (preferably water). To prepare a positive electrode mixture composition containing. No binder is added to this positive electrode mixture composition. The prepared positive electrode mixture composition is applied to the positive electrode base material 41 and the solvent (water or the like) is volatilized to form the positive electrode active material layer 42 to prepare the positive electrode 40.
The hydrophilized non-graphitic carbon is easily dispersed in a water-containing solvent because it is hydrophilized. In particular, the hydrophilized non-graphitic carbon in which the above-mentioned hydrophilic functional groups (acidic functional groups, etc.) are present on the surface is more likely to be dispersed in a water-containing solvent. Therefore, as described above, the aggregation of the hydrophilized non-graphitable carbon particles is suppressed, the particles are more sufficiently dispersed, and as a result, the positive electrode active material layer 42 having a good dispersed state can be formed. In particular, when the positive electrode active material containing the nickel-containing lithium transition metal composite oxide described above is blended in the positive electrode mixture composition, the positive electrode mixture composition tends to be more alkaline, and thus is better as described above. The positive electrode active material layer 42 in a dispersed state can be formed.
The above-mentioned solvent volatilization method may be a natural drying method, a heat drying method, or the like. The method for volatilizing the solvent is preferably a hot air drying method using a hot air drying furnace. By rapidly volatilizing the solvent by the hot air drying method, the aggregation of the hydrophilized non-graphitable carbon particles is more sufficiently suppressed, and the positive electrode active material layer 42 in a more uniform dispersed state can be formed.

Further, in producing the positive electrode 40, the above-mentioned hydrophilic functional groups (acidic functional groups, etc.) existing on the surface of the hydrophilized non-graphic carbon and the functional groups such as hydroxyl groups existing on the surface of the positive electrode active material are used. However, as described above, it can be dehydrated and condensed to be bonded. This bond can occur more when the positive electrode active material layer 42 is formed with the positive electrode mixture composition containing a relatively large amount of water. As a result, the positive electrode active materials and the positive electrode active material and the positive electrode base material 41 can be more firmly bonded to each other via the non-graphitable carbon without using a binder.

In the preparation of the electrode body 2, in the preparation of the negative electrode 50, a negative electrode mixture composition is prepared using a solvent containing water (preferably water) as a solvent in the same manner as in the preparation of the positive electrode 40, and the negative electrode active material layer is prepared. 52 may be formed. On the other hand, a negative electrode mixture composition may be prepared using an organic solvent as the solvent to form the negative electrode active material layer 52.

In the preparation of the electrode body 2, by forming the electrode body 2, a laminated type electrode body, a wound type electrode body, or the like can be produced by a general method.

In the preparation of the non-aqueous electrolyte, for example, a plurality of types of non-aqueous solvents and one or a plurality of types of electrolyte salts are mixed to prepare a non-aqueous electrolyte solution (non-aqueous electrolyte).

In assembling the power storage element, the non-aqueous electrolyte is housed in the case 3 by a general method appropriately selected from known methods. For example, when a non-aqueous electrolyte is used as the non-aqueous electrolyte, the electrode body 2 is housed in the case 3, the non-aqueous electrolyte is injected from the injection port formed in the case 3, and then the injection port is sealed. Just do it.

<Other embodiments>
The power storage element of the present invention is not limited to the above embodiment, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a well-known technique. In addition, some of the configurations of certain embodiments can be deleted. Further, a well-known technique can be added to the configuration of a certain embodiment.

In the above embodiment, the case where the power storage element 1 is used as a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) capable of charging and discharging has been described, but the type, shape, dimensions, capacity, etc. of the power storage element are arbitrary. be. The present invention can also be applied to capacitors such as various secondary batteries, electric double layer capacitors and lithium ion capacitors.

In the above embodiment, the power storage element 1 in which the positive electrode 40 contains hydrophilized non-graphitable carbon and does not contain a binder has been described in detail, but in the power storage element of another embodiment, the negative electrode is not hydrophilized. It may contain graphitic carbon and may not contain binders.

In the above embodiment, the electrode body 2 in which the positive electrode 40 and the negative electrode 50 are laminated via the separator 60 has been described, but the electrode body may not include the separator 60. For example, the positive electrode and the negative electrode may be in direct contact with each other in a state where a non-conductive layer is formed on the active material layer of the positive electrode or the negative electrode.

Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

A non-aqueous electrolyte secondary battery (lithium ion secondary battery) was manufactured as shown below.

(1) Preparation of positive electrode (Example 1)
[raw materials]
First, a positive electrode active material and a conductive agent were prepared.
・ Positive electrode active material (powder containing active material particles)
Nickel-containing lithium transition metal composite oxide LiNi _1/3 Co _1/3 Mn _1/3 O ₂
Particle size D50 of secondary particles in which primary particles are condensed with each other: 4 μm (average particle size D1)
-Conducting agent (hydrophilic dispersion slurry liquid containing hydrophilized non-graphitable carbon)
Hydrophilized carbon black water-dispersed slurry liquid Product name "Aqua-Black162" (manufactured by Tokai Carbon Co., Ltd.)
Solid content: 19.2% by mass
Average primary particle size of hydrophilized carbon black (average particle size D2): 110 nm
A large number of carboxy groups are present on the surface of the hydrophilized carbon black particles. Amount of hydrophilic functional groups determined by the above-mentioned neutralization titration: 780 [μmol / g]
Slurry pH measured by the method described above: 6.5
(D2 / D1) = 0.03
Particulate positive electrode active material was added to the aqueous dispersion slurry liquid containing the hydrophilized non-graphitic carbon, and mixed and kneaded. Then, the water was removed by hot air drying and vacuum drying to prepare a mixture of the conductive agent and the positive electrode active material.
The positive electrode mixture composition was prepared by mixing and kneading the mixture prepared in this manner with water. The mixing ratios of the solid content of the positive electrode active material and the conductive agent were as shown in Table 1, respectively.
The prepared positive electrode mixture composition is applied to one side of an aluminum foil (thickness 15 μm) as a positive electrode base material so that the coating amount (weight) after drying is 8.6 mg / cm ² , and after drying. , Roll pressed. Then, it was vacuum dried to volatilize and remove water and the like to form a positive electrode active material layer.
The thickness of the positive electrode active material layer (for one layer) was 31 μm. The density of the positive electrode active material layer was 2.8 g / cm ³ .

(Example 2)
A positive electrode mixture composition was prepared in the same manner as in Example 1 except that the blending ratios of the positive electrode active material and the conductive agent were changed to the values shown in Table 1.
The prepared positive electrode mixture composition was applied to one side of an aluminum foil (thickness 15 μm) as a positive electrode base material so that the coating amount (weight) after drying was 8.2 mg / cm ² , and after drying. , Roll pressed. Then, it was vacuum dried to volatilize and remove water and the like to form a positive electrode active material layer.
The thickness of the positive electrode active material layer (for one layer) was 29 μm. The density of the positive electrode active material layer was 2.8 g / cm ³ .

(Example 3)
A positive electrode mixture composition was prepared in the same manner as in Example 1 except that LiFePO ₄ (particle size D50: 7 μm) was used as the positive electrode active material. Moreover, the compounding ratio of the solid content of the positive electrode active material and the conductive agent was the same as in Example 1.
The prepared mixture composition for a positive electrode was applied to one side of an aluminum foil (thickness 15 μm) as a positive electrode base material so that the applied amount (weight) after drying was 8.3 mg / cm ² . After drying, a roll press was performed. Then, it was vacuum dried to volatilize and remove water and the like to form a positive electrode active material layer.
The thickness of the positive electrode active material layer (for one layer) was 38 μm. The density of the positive electrode active material layer was 2.2 g / cm ³ .

(Comparative Example 1)
N-methyl-2-pyrrolidone (NMP), conductive agent (carbon black [acetylene black] without hydrophilization treatment), binder (PVdF), positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 ) A positive electrode mixture composition was prepared by mixing and kneading O ₂ (particle size D50: 4 μm) of the secondary particles in which the primary particles were condensed with each other.
The compounding ratios of the solid content of the positive electrode active material, the conductive agent, and the binder were as shown in Table 1, respectively.
The prepared positive electrode mixture composition is applied to one side of an aluminum foil (thickness 15 μm) as a positive electrode base material so that the coating amount (weight) after drying is 8.6 mg / cm ² , and after drying. , Roll pressed. Then, it was vacuum dried to volatilize and remove water and the like to form a positive electrode active material layer.
The thickness of the positive electrode active material layer (for one layer) was 32 μm. The density of the positive electrode active material layer was 2.7 g / cm ³ .

(Comparative Example 2)
The positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) was mixed with the hydrophilized carbon black slurry liquid used in Example 1 and kneaded. Then, the water was removed by hot air drying and vacuum drying to prepare a mixture of the conductive agent and the positive electrode active material.
The positive electrode mixture composition was prepared by mixing and kneading the mixture prepared in this manner, N-methyl-2-pyrrolidone (NMP), and binder (PVdF).
The compounding ratios of the solid content of the positive electrode active material, the conductive agent, and the binder were as shown in Table 1, respectively.
A positive electrode active material layer was formed in the same manner as in Comparative Example 1 except that the above positive electrode mixture composition was used.
The basis weight, thickness (for one layer), and density of the positive electrode active material layer were the same as in Comparative Example 1.

(Comparative Example 3)
N-Methyl-2-pyrrolidone (NMP), a conductive agent (carbon black [acetylene black] not subjected to hydrophilization treatment), a binder (PVdF), and a positive electrode active material (LiFePO ₄ used in Example 3) are mixed. , A positive electrode mixture composition was prepared by kneading.
The compounding ratios of the solid content of the positive electrode active material, the conductive agent, and the binder were as shown in Table 1, respectively.
The prepared positive electrode mixture composition is applied to one side of an aluminum foil (thickness 15 μm) as a positive electrode base material so that the coating amount (weight) after drying is 8.3 mg / cm ² , and after drying. , Roll pressed. Then, it was vacuum dried to volatilize and remove water and the like to form a positive electrode active material layer.
The thickness of the positive electrode active material layer (for one layer) was 38 μm. The density of the positive electrode active material layer was 2.2 g / cm ³ (same as in Example 3).

(2) Preparation of negative electrode In all the examples and comparative examples, the same negative electrode was prepared and used for the battery.
As the negative electrode active material, particulate non-graphitable carbon (non-graphitizable carbon) having an average particle diameter of 3.3 μm was used. Moreover, PVdF was used as a binder.
The negative electrode mixture composition was prepared by mixing and kneading NMP, a binder, and an active material as solvents. The binder and the active substance were blended so that the solid content was 7% by mass and 93% by mass, respectively.
The prepared negative electrode mixture composition was applied to one side of a copper foil (thickness 8 μm) as a negative electrode base material so that the coating amount (weight) after drying was 3.95 mg / cm ² . After drying, a roll press was performed and vacuum drying was performed to remove water and the like to form a negative electrode active material layer.
The thickness of the negative electrode active material layer (for one layer) was 35 μm. The density of the negative electrode active material layer was 1.13 g / cm ³ .

(3) Preparation of separator In all the examples and comparative examples, the same separator was used for the battery.
A separator (inorganic coating separator) having an inorganic coating layer (heat resistant layer) having a thickness of 6 μm coated on one side of a polyethylene microporous membrane (separator base material) having a thickness of 15 μm was prepared. The air permeability of this separator was about 100 seconds / 100 cc, and the total thickness was 21 μm.

(4) Preparation of non-aqueous electrolyte solution In all Examples and Comparative Examples, the same non-aqueous electrolyte solution was used for the battery.
A non-aqueous solvent was prepared by mixing 1 part by volume of propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. LiPF ₆ was dissolved in this non-aqueous solvent so that the salt concentration was 1 mol / L to prepare a non-aqueous electrolytic solution.

(5) Preparation of evaluation cell (non-aqueous electrolyte secondary battery) (5-1)
An evaluation cell using LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the positive electrode active material was prepared by the following method.
The positive electrode, the negative electrode, and the separator were laminated to prepare an electrode body. The positive electrode and the negative electrode were arranged so that the respective active material layers faced each other via the separator, and the separator was arranged so that the inorganic coating layer faced the positive electrode active material layer. Then, this electrode body was housed in a case made of a metal resin composite film, and after injecting a non-aqueous electrolytic solution, the electrode body was sealed by heat welding to prepare an evaluation cell.
The prepared evaluation cell is charged with a constant current (charging current 3.5 mA, charging time 1 hour, charging temperature 25 ° C), allowed to stand at 25 ° C for 12 hours, and then charged with a constant current up to 4.2 V (charging current 3. 5mA, charging temperature 25 ° C), then constant voltage charging (charging time 3 hours, charging temperature 25 ° C) at 4.2V, then constant current discharge to 2.4V (discharge current 7mA, discharge temperature 25 ° C). Was done.
Next, a constant current charge (charging current 3.5 mA, charging temperature 25 ° C.) is performed with an amount of electricity of 80% SOC, and the mixture is allowed to stand at 45 ° C. for 15 hours, and then at 25 ° C. for 4 hours or more. A constant current discharge (discharge current 7 mA, discharge temperature 25 ° C.) was performed up to 2.4 V.
Then, the electric quantity of 20% SOC was charged with a constant current (charging current 3.5 mA, charging temperature 25 ° C.), and allowed to stand at 25 ° C. for 10 days.
(5-2)
An evaluation cell using LiFePO ₄ as the positive electrode active material was prepared by the following method.
An evaluation cell was prepared in the same manner as in (5-1) above.
The prepared evaluation cell is charged with a constant current (charging current 3.5 mA, charging time 1 hour, charging temperature 25 ° C), allowed to stand at 25 ° C for 12 hours, and then charged with a constant current to 3.55 V (charging current 3. 5mA, charging temperature 25 ° C), then constant voltage charging (charging time 3 hours, charging temperature 25 ° C) at 3.55V, then constant current discharge to 2.0V (discharge current 7mA, discharge temperature 25 ° C). Was done.
Next, a constant current charge (charging current 3.5 mA, charging temperature 25 ° C.) is performed with an amount of electricity of 80% SOC, and the mixture is allowed to stand at 45 ° C. for 15 hours, and then at 25 ° C. for 4 hours or more. A constant current discharge (discharge current 7 mA, discharge temperature 25 ° C.) was performed up to 2.0 V.
Then, the electric quantity of 20% SOC was charged with a constant current (charging current 3.5 mA, charging temperature 25 ° C.), and allowed to stand at 25 ° C. for 10 days.

<Evaluation of output performance after leaving at high temperature>
1. 1. Capacity confirmation 1-1. Cell using LiNi _1/3 Co _1/3 Mn _{1/3 O2} as the positive electrode active material In a constant temperature bath at 25 ° C, constant current charge to 4.2 V (charging current 3.5 mA), and then at 4.2 V. After constant voltage charging (charging time 3 hours), constant current discharge (discharge current 7 mA) was performed up to 2.4 V.
1-2. A cell using LiFePO ₄ as a positive electrode active material is charged with a constant current up to 3.55 V (charging current 3.5 mA) in a constant temperature bath at 25 ° C., and then charged with a constant voltage at 3.55 V (charging time 3 hours). A constant current discharge (discharge time 7 mA) was performed up to 2.0 V.
2. 2. Output confirmation test 2-1. Cell using LiNi _1/3 Co _1/3 Mn _{1/3 O2} as positive electrode active material Cell adjusted to SOC 50% (open circuit voltage 3.65V) in a constant temperature bath at 25 ° C with a current value of 14mA. After discharging for 10 seconds and resting for 60 seconds, the same amount of electricity as the discharged amount of electricity was charged at a current value of 3.5 mA.
After a pause of 300 seconds, the discharge test was carried out under the same conditions except that the discharge current values were changed to 28 mA, 42 mA, 56 mA, and 70 mA.
Then, each discharge current value was plotted on the horizontal axis, and the voltage 1 second after the start of discharge at each current value was plotted on the vertical axis, and these were linearly and linearly approximated by the least squares method. The slope of the straight line was taken as the resistance R of the cell.
Based on the calculated R, the cell output P was calculated by the following formula.
P [W] = 2.5 × (3.65-2.4) / R
2-2. Cell using LiFePO ₄ as positive electrode active material In a constant temperature bath at 25 ° C, a cell adjusted to SOC 50% (open circuit voltage 3.18 V) was discharged at a current value of 14 mA for 10 seconds, and after a pause of 60 seconds, 3 The same amount of electricity as the amount of discharged electricity was charged with a current value of .5 mA.
After a pause of 300 seconds, the discharge test was carried out under the same conditions except that the discharge current values were changed to 28 mA, 42 mA, 56 mA, and 70 mA.
Then, each discharge current value was plotted on the horizontal axis, and the voltage 1 second after the start of discharge at each current value was plotted on the vertical axis, and these were linearly and linearly approximated by the least squares method. The slope of the straight line was taken as the resistance R of the cell.
Based on the calculated R, the cell output P was calculated by the following formula.
P [W] = 2.0 × (3.18-2.0) / R
3. 3. High temperature standing test A cell adjusted to SOC 85% in a constant temperature bath at 25 ° C. was allowed to stand in a constant temperature bath at 65 ° C. for 15 days.
After that, the mixture was allowed to stand in a constant temperature bath at 25 ° C. for 4 hours or more, the above output confirmation test was carried out, and the output 15 days after the start of the test was calculated.
Similarly, by repeating the above-mentioned standing in a constant temperature bath at 65 ° C. for 15 days and the above-mentioned output confirmation test, the outputs 30 days and 45 days after the start of the high-temperature standing test were calculated. The output before the high temperature standing test was P1 and the output after 45 days was P2, and the output deterioration rate was calculated by the following formula.
Output reduction rate [%] = 100-[(P2 / P1) x 100]
It should be noted that the smaller the output reduction rate [%] is, the more sufficiently the reduction in output is suppressed.

Table 1 shows the evaluation results of the evaluation cells of Examples 1 to 3 and Comparative Examples 1 to 3. In Table 1, carbon black is referred to as "CB".

As can be seen from Table 1, in the power storage element of the example, the decrease in output after being left at a high temperature was suppressed. On the other hand, in the power storage element of the comparative example, the decrease in output after being left at a high temperature was not always suppressed.
From the comparison between Example 1 and Example 2, in the power storage device of Example, the positive electrode active material layer contains more than 4% by mass of hydrophilized non-graphitable carbon, so that the output is reduced after being left at a high temperature. Was sufficiently suppressed.
From the comparison between Example 1 and Comparative Example 1 and from the comparison between Example 3 and Comparative Example 3, in the power storage element of the example, the positive electrode active material layer is made of hydrophilic non-graphicular carbon and nickel. It can be said that the inclusion of the contained lithium transition metal composite oxide (positive electrode active material) significantly suppressed the decrease in output after being left at a high temperature.

1: Power storage element (non-aqueous electrolyte secondary battery),
2: Electrode body,
3: Case, 31: Case body, 32: Cover body,
4: Positive electrode terminal, 5: Negative electrode terminal,
40: Positive electrode,
41: Positive electrode base material, 42: Positive electrode active material layer,
50: Negative electrode,
51: Negative electrode base material, 52: Negative electrode active material layer,
45: Positive electrode lead, 55: Negative electrode lead,
60: Separator,
10: Power storage unit, 100: Power storage device.

Claims (3)

With an electrode having an active material layer containing active material particles,
The active material layer is a power storage element containing hydrophilic non-graphitic carbon and containing no binder. The power storage device according to claim 1, wherein the content of the hydrophilized non-graphitic carbon in the active material layer is more than 4% by mass. The power storage element according to claim 1 or 2, wherein the active material layer contains particles of a nickel-containing lithium transition metal composite oxide as the active material particles.

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