WO2022050101A1

WO2022050101A1 - Positive electrode active material, positive electrode, nonaqueous electrolyte power storage element, power storage device, method for producing positive electrode active material, method for producing positive electrode, and method for producing nonaqueous electrolyte power storage element

Info

Publication number: WO2022050101A1
Application number: PCT/JP2021/030751
Authority: WO
Inventors: 祐介水野; 祐一池田; 克弥西井; 周二人見; 茂樹山手; 智人福原
Original assignee: 株式会社Ｇｓユアサ
Priority date: 2020-09-01
Filing date: 2021-08-23
Publication date: 2022-03-10

Abstract

One embodiment of the present invention provides a positive electrode active material which contains lithium, oxygen, a first element and an element A, while having an anti-fluorite crystal structure, wherein: the first element is composed of at least one element that is selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper; and the element A is composed of at least one element that is selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine.

Description

Positive electrode active material, positive electrode, non-aqueous electrolyte power storage element, power storage device, positive electrode active material manufacturing method, positive electrode manufacturing method, and non-aqueous electrolyte power storage element manufacturing method

The present invention relates to a positive electrode active material, a positive electrode, a non-aqueous electrolyte power storage element, a power storage device, a method for manufacturing a positive electrode active material, a method for manufacturing a positive electrode, and a method for manufacturing a non-aqueous electrolyte power storage element.

Non-aqueous electrolyte secondary batteries represented by lithium-ion secondary batteries are widely used in personal computers, electronic devices such as communication terminals, automobiles, etc. due to their high energy density. The non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically separated by a separator and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between the two electrodes. It is configured to charge and discharge. In addition, 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.

Various active materials are used for the positive electrode and the negative electrode of the non-aqueous electrolyte power storage element, and various composite oxides are widely used as the positive electrode active material. As one of the positive electrode active materials, a transition metal solid solution lithium oxide in which a transition metal element such as Co is dissolved in Li ₂ O has been developed (see Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2019-003907 International Publication No. 2017/183653

A positive electrode active material (Li _2O -based positive electrode active material) in which one or more kinds of elements are solidly dissolved in Li ₂ O and Li ₂ O is theoretically expected as a positive electrode active material having a large discharge capacity. However, the conventional Li _2O -based positive electrode active material has the disadvantage of low charge / discharge cycle performance. That is, in the case of the conventional Li _2O -based positive electrode active material, since the discharge capacity is greatly reduced with the charge / discharge cycle, it is difficult to repeatedly charge / discharge with a sufficient amount of electricity many times.

The present invention has been made based on the above circumstances, and an object thereof is a positive electrode active material having a large discharge capacity even after a charge / discharge cycle, a positive electrode containing such a positive electrode active material, and a non-aqueous electrolyte storage. It is an object to provide an element and a power storage device, and a method for manufacturing these.

One aspect of the present invention contains lithium, oxygen, the first element and element A, and has an inverted fluorite-type crystal structure, and the first element is composed of chromium, manganese, iron, cobalt, nickel and copper. The element A is a positive electrode active material which is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine.

Another aspect of the present invention is a positive electrode for a non-aqueous electrolyte power storage element containing a positive electrode active material according to one aspect of the present invention.

Another aspect of the present invention is a non-aqueous electrolyte power storage element provided with a positive electrode according to one aspect of the present invention.

Another aspect of the present invention is a power storage device including a plurality of non-aqueous electrolyte power storage elements and one or more non-water electrolyte power storage elements according to one aspect of the present invention.

Another aspect of the present invention comprises treating a material containing lithium, oxygen, the first element and element A by a mechanochemical method, wherein the first element is chromium, manganese, iron, cobalt, nickel and copper. It is a method for producing a positive electrode active material which is at least one selected from the group consisting of, and the element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine.

Another aspect of the present invention comprises producing a positive electrode using the positive electrode active material according to one aspect of the present invention or the positive electrode active material obtained by the method for producing a positive electrode active material according to one aspect of the present invention. This is a method for manufacturing a positive electrode for a non-aqueous electrolyte power storage element.

Another aspect of the present invention is a method for manufacturing a non-aqueous electrolyte power storage element, which comprises a method for manufacturing a positive electrode according to one aspect of the present invention.

According to any aspect of the present invention, a positive electrode active material having a large discharge capacity even after a charge / discharge cycle, a positive electrode containing such a positive electrode active material, a non-aqueous electrolyte power storage element and a power storage device, and a method for manufacturing these are used. Can be provided.

FIG. 1 is an external perspective view showing a non-aqueous electrolyte power storage element according to an embodiment of the present invention. FIG. 2 is a schematic view showing a power storage device configured by assembling a plurality of non-aqueous electrolyte power storage elements according to an embodiment of the present invention. FIG. 3 is an X-ray diffraction diagram using CuKα rays of each positive electrode active material of Examples 2-1 to 2-3 and Comparative Example 2-1. FIG. 4 is a graph showing the amount of oxygen gas generated with respect to the amount of electricity charged during charging of the non-aqueous electrolyte power storage element including the positive electrode active materials of Examples 2-1 to 2-3 and Comparative Example 2-1. FIG. 5 is a graph showing the amount of electric discharge for each charge / discharge cycle in the non-aqueous electrolyte power storage device including the positive electrode active materials of Examples 2-1 to 2-3 and Comparative Example 2-1.

First, an outline of a positive electrode active material, a positive electrode, a non-aqueous electrolyte power storage element, a power storage device, a positive electrode active material manufacturing method, a positive electrode manufacturing method, and a non-aqueous electrolyte power storage element manufacturing method disclosed in the present specification will be described. do.

The positive electrode active material according to one aspect of the present invention contains lithium, oxygen, a first element and an element A, and has an inverted fluorite-type crystal structure, and the first element is chromium, manganese, iron, cobalt. , At least one selected from the group consisting of nickel and copper, and the element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine (α). ).

The positive electrode active material (α) according to one aspect of the present invention has a large discharge capacity after a charge / discharge cycle, and can be charged / discharged many times with a sufficient amount of electricity. The reason for this is not clear, but the following reasons are presumed. One of the causes of the low charge / discharge cycle performance of the conventional Li _2O -based positive electrode active material is that oxygen is desorbed from the positive electrode active material with repeated charging / discharging. On the other hand, the positive electrode active material (α) according to one aspect of the present invention is a conventional Li ₂ O-based positive electrode active material in which a transition metal element is solid-dissolved in Li ₂ O having an inverted fluorite-type crystal structure. On the other hand, it has a structure in which a part of oxygen is further substituted with the element A. Since the element A is contained in the positive electrode active material (α) in this way, desorption of oxygen from the positive electrode active material due to repeated charging and discharging is suppressed, and the crystal structure of the positive electrode active material is maintained. As a result, it is presumed that the state where the discharge capacity is large is maintained even after the charge / discharge cycle.

In the positive electrode active material (α) according to one aspect of the present invention, the molar ratio of the content of the element A to the content of oxygen is preferably more than 0.00 and 0.2 or less, preferably 0.1. It is more preferably less than or equal to, more preferably 0.05 or less, and sometimes 0.02 or less. Even in such a case, it can be said that the positive electrode active material contains an appropriate amount of element A, and the discharge capacity of the positive electrode active material (α) after the charge / discharge cycle becomes larger.

In the positive electrode active material (α) according to one aspect of the present invention, the first element is preferably cobalt. In such a case, the discharge capacity of the positive electrode active material after the charge / discharge cycle becomes larger.

According to the technique disclosed herein, it contains lithium, oxygen, the first element, and element A, and has an inverted fluorite-type crystal structure, and the first element is chromium, manganese, iron, cobalt, nickel. The positive electrode active material (α), which is at least one selected from the group consisting of copper and copper, and the element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine. Provided.
The positive electrode active material (α) further contains a second element, and even if the second element is at least one selected from the group consisting of group 13 elements, group 14 elements, phosphorus, antimony, bismuth and tellurium. good.
In the positive electrode active material (α), the element A may be nitrogen.
The positive electrode active material (α) may be a positive electrode active material represented by the following formula 1.
Li _a M ¹ _b M ² _c ON _d ... 1
Here, in Equation 1, M ¹ is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni and Cu. M ² is at least one selected from the group consisting of Group 13 elements, Group 14 elements, P, Sb, Bi and Te. a, b, c and d are 1.0 <a <2.0, 0.000 <b <0.5, 0.000 <c <0.2, 0.000 <d <0.2, respectively. Meet.
In the X-ray diffraction diagram using CuKα rays, the positive electrode active material (α) has a ratio of the integrated intensity of the diffraction peak having a diffraction angle 2θ near 44 ° to the integrated intensity of the diffraction peak having a diffraction angle 2θ near 33 °. It may be more than 0.00 and 2 or less.

The positive electrode active material according to another aspect of the present invention contains lithium, oxygen, a first element, a second element and an element A, has an inverted fluorite-type crystal structure, and the first element is chromium. , Manganese, iron, cobalt, nickel and at least one selected from the group consisting of copper, and the second element is at least selected from the group consisting of group 13 element, group 14 element, phosphorus, antimony, bismuth and tellurium. It is one kind, and is a positive electrode active material (β) in which the element A is nitrogen.

When the positive electrode active material (β) is used for a non-aqueous electrolyte power storage element, in addition to the above-mentioned effect that the discharge capacity is large even after the charge / discharge cycle, oxygen gas is generated during charging even when the amount of charging electricity is increased. It is suppressed. That is, the amount of charging electricity leading to the generation of oxygen gas can be increased. The reason for this is not clear, but the following reasons are presumed. Generally, in a Li ₂ O positive electrode active material, oxygen gas is generated by excessive oxidation of oxygen atoms in Li ₂ O as shown in the following formula.
2Li ₂ O
→ Li ₂ O ₂ + 2Li ⁺ + 2e ^－
→ LiO ₂ + 3Li ⁺ + ^3e-
→ O ₂ + 4Li ⁺ + ^4e-
On the other hand, in the positive electrode active material (β), nitrogen is contained as the element A together with the first element, so that it is considered that an M1 ^- ON mixed orbital is formed. At the time of charging, electrons are provided from this hybrid orbital (valence band), that is, electrons are provided from nitrogen atoms in addition to oxygen atoms and the like. Therefore, when the positive electrode active material (β) is charged to the same extent as the Li _2O -based positive electrode active material that does not contain a nitrogen atom, the number of electrons provided from the oxygen atom when the state is reached is reduced. That is, it is presumed that the generation of oxygen gas is less likely to occur because the oxidation number of oxygen atoms is small. Further, since the positive electrode active material (β) suppresses the generation of oxygen gas even when the amount of charging electricity is increased, the effective amount of electricity of the non-aqueous electrolyte power storage element can be increased, and as a result, the energy density. Can be enhanced.
Further, the positive electrode active material (β) has a sufficiently large discharge capacity that is maintained even after repeated charge / discharge cycles, and has a sufficient charge / discharge cycle life even when the amount of charging electricity is increased. The reason for this effect is not clear, but even when the amount of electricity charged is increased, the generation of oxygen gas during charging is suppressed, and the presence of nitrogen atoms improves electron conductivity. It is guessed that.

The positive electrode active material according to another aspect of the present invention is a positive electrode active material (γ) represented by the following formula 1.
Li _a M ¹ _b M ² _c ON _d ... 1
In formula 1, M ¹ is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni and Cu. M ² is at least one selected from the group consisting of Group 13 elements, Group 14 elements, P, Sb, Bi and Te. a, b, c and d are 1.0 <a <2.0, 0.000 <b <0.5, 0.000 <c <0.2, 0.000 <d <0.2, respectively. Meet.

When the positive electrode active material (γ) is used in a non-aqueous electrolyte power storage element, in addition to the above-mentioned effect that the discharge capacity is large even after the charge / discharge cycle, oxygen gas is generated during charging even when the amount of charging electricity is increased. It is suppressed. That is, the amount of charging electricity leading to the generation of oxygen gas can be increased. Therefore, the positive electrode active material (γ) can increase the effective electric amount of the non-aqueous electrolyte power storage element, and as a result, the energy density can be increased even when the charging electric amount is increased. Further, the positive electrode active material (γ) has a sufficient charge / discharge cycle life. Although these reasons are not clear, the same reasons as the above-mentioned positive electrode active material (β) are presumed.

The composition ratio of the positive electrode active material in the present specification refers to the composition ratio of the positive electrode active material that has not been charged and discharged, or the positive electrode active material that has been completely discharged by the following method. First, the non-aqueous electrolyte power storage element is constantly charged with a current of 0.05 C until the charge end voltage at the time of normal use is reached, and the state is fully charged. After a 30-minute pause, a constant current discharge is performed with a current of 0.05 C to the lower limit voltage during normal use. Disassemble, take out the positive electrode, assemble a half-cell with a metal lithium electrode as the counter electrode, and perform constant current discharge with a current of 10 mA per 1 g of the positive electrode mixture until the terminal voltage becomes 1.5 V, and the positive electrode is in a completely discharged state. Adjust to. Re-disassemble and take out the positive electrode. The components (non-aqueous electrolyte, etc.) adhering to the removed positive electrode are thoroughly washed with dimethyl carbonate, dried under reduced pressure at room temperature for 24 hours, and then the positive electrode active material is collected. The collected positive electrode active material is used for measurement. The work from disassembling the non-aqueous electrolyte power storage element to preparing the sample to be measured is performed in an argon atmosphere having a dew point of −76 ° C. or lower. Here, the normal use is a case where the non-aqueous electrolyte storage element is used by adopting the charge / discharge conditions recommended or specified for the non-aqueous electrolyte storage element, and the non-aqueous electrolyte power storage element is used. When a charger for this purpose is prepared, it means a case where the charger is applied to use the non-aqueous electrolyte power storage element.

In the X-ray diffraction diagram using the CuKα rays of the positive electrode active material (β) and the positive electrode active material (γ), the diffraction peak having a diffraction angle 2θ near 44 ° with respect to the integrated intensity of the diffraction peak near the diffraction angle 2θ of 33 °. The ratio of the integrated intensities of is preferably more than 0.00 and 2 or less.

The diffraction peak in which the diffraction angle 2θ is around 44 ° is caused by the inclusion of nitrogen, and its integrated intensity increases as the nitrogen content increases. Therefore, the ratio of the integrated intensity of the diffraction peak with the diffraction angle 2θ near 44 ° to the integrated intensity of the diffraction peak with the diffraction angle 2θ around 33 °, which is characteristic of the Li _2O positive electrode active material, is more than 0.00 and 2 or less. The configuration of being means that the nitrogen content in the positive electrode active material (β) and the positive electrode active material (γ) is in a suitable range, and when used in a non-aqueous electrolyte power storage element, oxygen during charging is used. It is possible to further suppress the generation of gas and extend the charge / discharge cycle life. The diffraction peak in which the diffraction angle 2θ is around 44 ° refers to the peak having the strongest diffraction intensity in the range of the diffraction angle 2θ of 42 ° to 46 °.

The positive electrode active material according to one aspect of the present invention preferably satisfies the following formula 2.
1.000 <a ₁ / a ₂ <1.005 ・・・ 2
In Equation 2, a ₁ is the lattice constant of the positive electrode active material. a ₂ is a lattice constant of a compound having a composition in which all the elements A in the positive electrode active material are replaced with oxygen and having an inverted fluorite-type crystal structure.

In a positive electrode active material in which the first element is solid-solved in Li ₂ O having an inverted fluorite-type crystal structure, when a part of oxygen is replaced with element A, the substitution amount (content) of this element A ), The inventors confirmed that the lattice constant increased. That is, when the above formula 2 is satisfied, it means that the positive electrode active material contains an appropriate amount of element A, and the discharge capacity of the positive electrode active material after the charge / discharge cycle becomes larger.

In addition, "a compound having a composition in which all the element A in the positive electrode active material is replaced with oxygen and having an inverted fluorite-type crystal structure" is simply a compound in which the element A is replaced with the same number of oxygen. It means that the number of positive charges and the number of negative charges do not change before and after the replacement. For example, in the case of the positive electrode active material represented by "Li _1.58 Co _0.157 O _0.992 F _0.0157 ", since two Fs are replaced with one O, "Li ₁ " is used. The compound having a composition in which the element A (fluorine) in _.58 Co _0.157 O _0.992 F _0.0157 is completely replaced with oxygen is "Li _1.58 Co _0.157 O".

In the X-ray diffraction diagram using CuKα rays of the positive electrode active material, it is preferable that the half width of the diffraction peak near the diffraction angle 2θ of 33 ° is 0.3 ° or more.

According to such a configuration, when used in a non-aqueous electrolyte power storage element, generation of oxygen gas during charging is suppressed, and a Li _2O -based positive electrode active material having a sufficient charge / discharge cycle life is provided with high certainty. can do. The diffraction peak in which the diffraction angle 2θ is around 33 ° refers to the peak having the strongest diffraction intensity in the range of the diffraction angle 2θ of 30 ° to 35 °.

The X-ray diffraction measurement of the positive electrode active material is performed by powder X-ray diffraction measurement using an X-ray diffractometer (manufactured by Rigaku, product name: MiniFlex II) with a CuKα ray as the radiation source, a tube voltage of 30 kV, and a tube current of 15 mA. At this time, the diffracted X-rays pass through a Kβ filter having a thickness of 30 μm and are detected by a high-speed one-dimensional detector (D / teX Ultra 2). The sampling width is 0.02 °, the scan speed is 5 ° / min, the divergent slit width is 0.625 °, the light receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm. The X-ray diffraction pattern obtained by the above-mentioned X-ray diffraction measurement is automatically analyzed using analysis software (manufactured by Rigaku, product name: PDXL). Here, "precision background" and "automatic" are selected in the work window of the analysis software, and the strength error between the measured pattern and the calculated pattern is refined to 1000 or less. Background processing is performed by this refinement, and the value of the peak intensity of each diffraction line, the value of the half width, and the like are obtained as the values obtained by subtracting the baseline.

The lattice constant a (nm) of the positive electrode active material is obtained up to the fourth decimal place, and when evaluating up to the third decimal place, the following processing is performed based on the X-ray diffraction pattern refined by the above analysis software. Can be obtained by The data of "ICDD PDF 00-012-0254" is extracted from the "card information reading" column of the flow bar of the above analysis software, moved to the "crystal phase candidate" column, and "confirmed". Next, select "Lattice constant refinement" of the flow bar, select "lithia" as the phase to be analyzed, and check the "No." columns of 33 ° and 56 °. By selecting "No correction" in "Angle correction" and "Refining", the value of the lattice constant is output.

However, when the ratio of the lattice constants (a ₁ / a ₂ ) is obtained from the above lattice constants a ₁ and a ₂ (nm), the lattice constants a ₁ and a ₂ (nm) are obtained up to the fifth decimal place, and the decimal point is the fifth. Evaluate up to 4th place. In this case, the lattice constants a ₁ and a ₂ refer to those obtained based on the results of X-ray diffraction measurement carried out by the following method. Specifically, the powder X-ray diffraction beamline of the large-scale radiation facility "SPring-8" is used for the X-ray diffraction measurement. The measurement sample is previously filled in a mark tube made of Lindemann glass having an inner diameter of 0.6 mm in a glove box having an argon atmosphere and sealed. This mark tube is attached to the measurement holder, the 2θ range is set to 2 ° to 78 °, and the exposure time of synchrotron radiation is set to 5 minutes for measurement.
In the case of X-ray diffraction measurement with "SPring-8", even if the wavelength of the X-ray is set to the same set value, the wavelength is slightly different depending on the measurement date, and CeO ₂ is used as a standard sample to use the X-ray on each measurement day. The wavelength has been calculated. Therefore, "the lattice constant a ₁ of the positive electrode active material" and "the lattice constant of the compound having a composition in which all the elements A in the positive electrode active material are replaced with oxygen and having an inverted fluorite-type crystal structure". “A ₂ ” is determined based on the result of X-ray diffraction measurement measured on the same day. Specifically, first, the composition of the positive electrode active material P to be measured is analyzed, and the compound Q having a composition in which all the elements A of the positive electrode active material P are replaced with oxygen and having an inverted fluorite-type crystal structure. To synthesize. X-ray diffraction measurement is performed on the positive electrode active material P and the compound Q with "SPring-8" on the same day.
In the obtained X-ray diffraction diagram, the diffraction angle corresponding to the diffraction index 111 in the space group Fm _- 3m of the inverted fluorite type crystal structure is read, and the values of the lattice constants a1 and _a2 are calculated.

The positive electrode according to one aspect of the present invention is a positive electrode for a non-aqueous electrolyte power storage element containing a positive electrode active material according to one aspect of the present invention. Since the positive electrode contains the positive electrode active material according to one aspect of the present invention, the discharge capacity of the non-aqueous electrolyte power storage element provided with the positive electrode after the charge / discharge cycle is increased, and the positive electrode is charged and discharged many times with a sufficient amount of electricity. Is possible.

The non-aqueous electrolyte power storage element according to one aspect of the present invention is a non-aqueous electrolyte power storage element having a positive electrode according to one aspect of the present invention (hereinafter, may be simply referred to as “storage element”). The power storage element has a large discharge capacity after a charge / discharge cycle, and can be charged / discharged many times with a sufficient amount of electricity.

The power storage device according to one aspect of the present invention is a power storage device including a plurality of non-aqueous electrolyte power storage elements and one or more non-water electrolyte power storage elements according to one aspect of the present invention.

Since the power storage device includes one or more non-aqueous electrolyte power storage elements, the discharge capacity after the charge / discharge cycle is large, and it is possible to charge / discharge a large number of times with a sufficient amount of electricity.

The method for producing a positive electrode active material according to one aspect of the present invention comprises treating a material containing lithium, oxygen, a first element and element A by a mechanochemical method, wherein the first element is chromium, manganese and iron. , Cobalt, nickel and copper, and the element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine. It is a manufacturing method of.

The method for producing a positive electrode active material according to another aspect of the present invention comprises treating a material containing lithium, oxygen, a first element, a second element and an element A by a mechanochemical method, wherein the first element is used. , Chromium, manganese, iron, cobalt, nickel and copper, and the second element is selected from the group consisting of group 13 elements, group 14 elements, phosphorus, antimony, bismuth and tellurium. This is a method for producing a positive electrode active material in which the element A is nitrogen.

According to the method for producing a positive electrode active material, it is possible to produce a positive electrode active material having a large discharge capacity after a charge / discharge cycle and capable of being charged / discharged many times with a sufficient amount of electricity.

In the method for producing a positive electrode according to one aspect of the present invention, a positive electrode is produced using the positive electrode active material according to one aspect of the present invention or the positive electrode active material obtained by the method for producing a positive electrode active material according to one aspect of the present invention. It is a method of manufacturing a positive electrode for a non-aqueous electrolyte power storage element.

According to the positive electrode manufacturing method, it is possible to manufacture a positive electrode having a large discharge capacity after a charge / discharge cycle and capable of being charged / discharged many times with a sufficient amount of electricity.

The method for manufacturing a non-aqueous electrolyte power storage element according to one aspect of the present invention is a method for manufacturing a non-aqueous electrolyte power storage element including the method for manufacturing a positive electrode according to one aspect of the present invention.

According to the method for manufacturing the non-aqueous electrolyte power storage element, it is possible to manufacture a non-water electrolyte power storage element having a large discharge capacity after a charge / discharge cycle and capable of being charged / discharged many times with a sufficient amount of electricity.

Hereinafter, the positive electrode active material, the method for manufacturing the positive electrode active material, the positive electrode, the method for manufacturing the positive electrode, the non-aqueous electrolyte power storage element, the method for manufacturing the non-aqueous electrolyte power storage element, and the power storage device according to the embodiment of the present invention will be described in order. ..

<Positive electrode active material>
The positive electrode active material (α) according to the embodiment of the present invention contains lithium, oxygen, a first element and an element A. The first element is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper. The element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine. The positive electrode active material (α) has an inverted fluorite-type crystal structure.

The element A is an element that can take a negative oxidation number. Among the elements A, nitrogen and fluorine having an atomic radius close to oxygen are preferable from the viewpoint of stability of the crystal structure of the positive electrode active material.

The molar ratio (A / O) of the content of element A to the content of oxygen in the positive electrode active material (α) may be, for example, more than 0.00 and 0.2 or less, but more than 0.00 and 0.05. The following is preferable, more than 0.00 and 0.02 or less, more preferably 0.001 or more and 0.012 or less, and even more preferably 0.003 or more and 0.010 or less. When the molar ratio (A / O) is at least the above lower limit, the effect of containing the element A is remarkable. On the other hand, when the molar ratio (A / O) is not more than the above upper limit, the crystal structure of the positive electrode active material is maintained, and the discharge capacity of the positive electrode active material after the charge / discharge cycle becomes larger.

The molar ratio of the content of element A to the content of the first element in the positive electrode active material (α) (for example, A / Co when the first element is cobalt) is, for example, more than 0.00 and 0.5 or less. However, it is preferably more than 0.00 and 0.3 or less, more preferably 0.01 or more and 0.2 or less, further preferably 0.02 or more and 0.10 or less, and 0.03 or more and 0.08 or less. It may be even more preferable. When the molar ratio (for example, when the first element is cobalt, A / Co) is at least the above lower limit, the effect of containing the element A is remarkable. On the other hand, when the molar ratio (for example, A / Co when the first element is cobalt) is not more than the above upper limit, the crystal structure of the positive electrode active material is maintained, and the positive electrode active material is discharged after the charge / discharge cycle. The capacity becomes larger.

The molar ratio of the content of the first element to the total content of lithium and the first element in the positive electrode active material (α) (for example, when the first element is cobalt, Co / (Li + Co)) is, for example. It is preferably 0.01 or more and 0.3 or less, more preferably 0.03 or more and 0.2 or less, and further preferably 0.05 or more and 0.15 or less. The molar ratio (for example, when the first element is cobalt, Co / (Li + Co)) serves as a guide for the amount of the first element dissolved in Li _2O , and the molar ratio (for example, when the first element is cobalt) is a guideline. When Co / (Li + Co)) is in the above range, the discharge capacity of the positive electrode active material after the charge / discharge cycle becomes larger.

The oxygen content in the positive electrode active material (α) is not particularly limited, and is usually determined from the composition ratio of lithium, the first element, the element A, and the like, the valence of these elements, and the like. However, stoichiometrically, it may be in a state of oxygen deficiency or oxygen excess. Further, the lithium content in the positive electrode active material (α) is not particularly limited, and the composition may be in a state where the lithium content is stoichiometrically excessive or insufficient. Each element constituting the positive electrode active material (α) can be appropriately adjusted as long as it can have an inverted fluorite-type crystal structure.

The positive electrode active material (α) may contain lithium, oxygen, the first element, and other elements other than the element A. However, the molar ratio of the contents of the other elements to the total content of all the elements constituting the positive electrode active material (α) is preferably 0.5 or less, preferably 0.3 or less, 0.1 or less, or 0. In some cases, 01 or less is more preferable. The positive electrode active material (α) may be substantially composed of lithium, oxygen, the first element and the element A.

The composition formula of the positive electrode active material (α) is preferably represented by the following formula 3.
Li _a M ¹ _b O _c _Ad ... 3
In the above formula 3, M ¹ is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni and Cu. A is at least one selected from the group consisting of N, S, Se, F, Cl, Br and I. a, b, c and d satisfy 0 <a <2, 0 <b <0.5, 0 <c <1 and 0 <d <0.2, respectively.

The lower limit of a in the above formula 3 is preferably 1, more preferably 1.4, and even more preferably 1.5. The upper limit of a is preferably 1.9, more preferably 1.8, and even more preferably 1.7.

The lower limit of b in the above formula 3 is preferably 0.01, more preferably 0.05, further preferably 0.1, and even more preferably 0.14. The upper limit of b is preferably 0.4, more preferably 0.3, and even more preferably 0.2.

The lower limit of c in the above formula 3 is preferably 0.5, more preferably 0.7, even more preferably 0.9, and even more preferably 0.96. The upper limit of c is preferably 0.999, more preferably 0.99.

The lower limit of d in the above formula 3 is preferably 0.001, more preferably 0.003, and even more preferably 0.005. The upper limit of d is preferably 0.1, more preferably 0.05, still more preferably 0.02, and even more preferably 0.01.

It is presumed that the positive electrode active material (α) has a structure in which a part of Li is substituted with the first element and a part of O is substituted with the element A with respect to Li ₂ O. Therefore, when the first element is Co, when the average valence of Co is + m, the relationship of a + mb = 2 may be established with respect to a and b in the above formula 3. In the positive electrode active material (α), Co usually exists in a state of valence of +2 or +3, and Co having different valences may coexist. Therefore, the average valence of Co in the positive electrode active material (α) is usually in the range of +2 to +3. Further, when the oxidation number of A (element A) in the above formula 3 is "-n", the relationship of c + (n / 2) d = 1 may be established with respect to the relationship of c and d.

The positive electrode active material (β) according to another embodiment of the present invention contains lithium, oxygen, a first element, a second element and an element A, has an inverted fluorite-type crystal structure, and has the above-mentioned first element. The element is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper, and the second element is a group consisting of group 13 elements, group 14 elements, phosphorus, antimony, bismuth and tellurium. The element A is nitrogen, which is at least one selected from the above.

The positive electrode active material (β) is typically the first element (M ¹ ), the second element (M ² ), and the element A (N) with respect to Li ₂ O having an inverted fluorite-type crystal structure. ) Is a solid-dissolved composite oxide. Here, for example, the charge / discharge reaction (oxidation-reduction reaction) in a conventional composite oxide in which Co is dissolved in Li ₂ O is said to be electron transfer in a Co3d—O2p hybrid orbital. Similarly, when the first element other than Co is dissolved, it is said that a redox reaction occurs by electron transfer in the M 13d ^- O2p hybrid orbital. That is, the first element is an element for activating the redox reaction of oxygen atoms. The second element is a p-block element that can be a cation and can be dissolved in Li ₂ O. When the second element is dissolved in Li ₂ O, it is presumed that the oxygen atom forms an sp hybrid orbital of M ² sp-O2p, and the bond of this M ² sp-O2p by the sp hybrid orbital is very strong. Will be. That is, the second element is an element for enhancing the stability of the crystal structure. As described above, nitrogen, which is an element A, is an element that suppresses the generation of oxygen gas due to excessive oxidation of oxygen atoms, and has the effect of increasing electron conductivity and extending the charge / discharge cycle life. ..

The positive electrode active material (β) is usually composed of one or more kinds of oxides. The positive electrode active material (β) may have at least a part having an inverted fluorite-type crystal structure, and has a crystal structure other than the inverted fluorite-type crystal structure or an amorphous portion. May be good. The positive electrode active material (β) preferably has an inverted fluorite-type crystal structure as a main phase. Having an inverted fluorite-type crystal structure as the main phase means that the diffraction intensity of the peak derived from the inverted fluorite-type crystal structure is observed most strongly. In such a positive electrode active material, in an X-ray diffraction diagram using CuKα rays, a peak having the strongest diffraction intensity is observed in the range where the diffraction angle 2θ is in the range of 10 ° to 80 ° and the diffraction angle 2θ is around 33 °. When the positive electrode active material (β) is composed of a plurality of types of oxides, it contains an oxide that does not contain one or more of lithium, a first element, a second element, and an element A. It may be. The positive electrode active material (β) may contain a compound or the like other than an oxide.

The first element preferably contains cobalt, more preferably cobalt. The first element may consist of only one kind or may consist of two or more kinds.

Examples of the Group 13 element in the second element include boron, aluminum, gallium, indium, and thallium. Examples of the Group 14 element include carbon, silicon, germanium, tin, lead and the like. As the second element, a group 13 element and a group 14 element are preferable, a group 14 element is more preferable, and silicon is further preferable. The second element may consist of only one kind or may consist of two or more kinds.

The molar ratio of the content of the second element (M ² ) to the total content of the first element (M ¹ ) and the second element (M ² ) in the positive electrode active material (β) (M ² / (M ¹ ). + M ² )) is not particularly limited, but is, for example, 0.01 or more and 0.8 or less, preferably 0.05 or more and 0.6 or less, more preferably 0.1 or more and 0.5 or less, and 0.15 or more and 0. In some cases, 0.4 or less is further preferable, and in some cases, 0.2 or more and 0.3 or less is even more preferable. By setting the molar ratio (M ² / (M ¹ + M ² )) in the above range, the stability of the crystal structure and the like can be improved.

The first element (M ¹ ) and the second element (M ² ) with respect to the total content of lithium (Li), the first element (M ¹ ) and the second element (M ² ) in the positive electrode active material (β). The molar ratio of the total content with and ((M ¹ + M ² ) / (Li + M ¹ + M ² )) is not particularly limited, but for example, it is preferably 0.05 or more and 0.3 or less, and 0.1 or more and 0.2 or less. More preferably, it is more preferably 0.13 or more and 0.16 or less. The above-mentioned molar ratio ((M ¹ + M ² ) / (Li + M ¹ + M ² )) is a guideline for the substitution amount (content) of the first element and the second element with respect to Li, which is a cation of Li ₂ O. By setting the molar ratio ((M ¹ + M ² ) / (Li + M ¹ + M ² )) in the above range, the charge / discharge performance and the like can be improved.

The molar ratio (N / M ¹ ) of the content of the element A (N) to the content of the first element (M ¹ ) in the positive electrode active material (β) is not particularly limited, and is, for example, more than 0.00 1. It may be less than 0, but is preferably 0.01 or more and 0.8 or less, more preferably 0.02 or more and 0.5 or less, further preferably 0.03 or more and 0.3 or less, and 0.05 or more and 0. 15 or less is even more preferable. By setting the molar ratio (N / M ¹ ) of the content of the element A (N) to the content of the first element (M ¹ ) in the above range, when it is used for a non-aqueous electrolyte power storage element, it is charged. It is possible to further suppress the generation of oxygen gas and extend the charge / discharge cycle life. Further, by setting the molar ratio (N / M ¹ ) to the upper limit or less, the initial discharge capacity tends to increase. When used in a non-aqueous electrolyte power storage element, the molar ratio (N / M ¹ ) may be more preferably 0.10 or less from the viewpoint of further suppressing the generation of oxygen gas during charging. From the viewpoint of extending the charge / discharge cycle life, the molar ratio (N / M ¹ ) may be more preferably 0.10 or more.

The molar ratio (N / O) of the content of the element A (N) to the content of oxygen (O) in the positive electrode active material (β) is not particularly limited, and is, for example, more than 0.000 and less than 0.2. However, 0.002 or more and 0.1 or less are preferable, 0.004 or more and 0.08 or less are more preferable, 0.006 or more and 0.05 or less are further preferable, and 0.01 or more and 0.03 or less are more preferable. More preferred. By setting the molar ratio (N / O) of the content of element A (N) to the content of oxygen (O) in the above range, oxygen gas is generated during charging when used in a non-aqueous electrolyte power storage element. Can be further suppressed and the charge / discharge cycle life can be extended. Further, by setting the molar ratio (N / O) to be equal to or lower than the upper limit, the initial discharge capacity tends to increase. When used in a non-aqueous electrolyte power storage element, the molar ratio (N / O) may be more preferably 0.02 or less from the viewpoint of further suppressing the generation of oxygen gas during charging. From the viewpoint of extending the charge / discharge cycle life, the molar ratio (N / O) may be more preferably 0.02 or more.

The positive electrode active material (β) may contain lithium, oxygen, a first element, a second element, and other elements other than element A. However, the molar ratio of the contents of the other elements to the total content of all the elements constituting the positive electrode active material (β) is preferably 0.1 or less, more preferably 0.01 or less. The positive electrode active material (β) may be substantially composed of lithium, oxygen, a first element, a second element and an element A. Since the positive electrode active material (β) is substantially composed of lithium, oxygen, a first element, a second element, and an element A, when used in a non-aqueous electrolyte power storage element, oxygen gas during charging can be used. The generation can be further suppressed and the charge / discharge cycle life can be extended.

The oxygen content in the positive electrode active material (β) is not particularly limited, and is usually determined from the composition ratio of lithium, the first element, the second element, the element A, and the like, and the valence of these elements. However, it may be an oxide with insufficient oxygen or excess oxygen in the stoichiometric ratio.

As an example of a preferable composition formula of the positive electrode active material (β), the composition formula of the following formula 1 described later can be mentioned.

The positive electrode active material (γ) according to another embodiment of the present invention is represented by the following formula 1. When the positive electrode active material (γ) is composed of one kind of oxide, the composition formula of the following formula 1 represents the composition of the oxide. When the positive electrode active material (γ) is composed of a plurality of types of oxides, the composition formula of the following formula 1 represents the overall composition of the plurality of types of oxides.
Li _a M ¹ _b M ² _c ON _d ... 1
In formula 1, M ¹ is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni and Cu. M ² is at least one selected from the group consisting of Group 13 elements, Group 14 elements, P, Sb, Bi and Te. a, b, c and d are 1.0 <a <2.0, 0.000 <b <0.5, 0.000 <c <0.2, 0.000 <d <0.2, respectively. Meet.

The a in the above formula 1 is preferably 1.1 or more and 1.9 or less, more preferably 1.2 or more and 1.8 or less, further preferably 1.3 or more and 1.7 or less, and 1.4 or more and 1.6. The following is even more preferable, and 1.5 or less is even more preferable.

B in the above formula 1 is preferably 0.05 or more and 0.4 or less, more preferably 0.1 or more and 0.3 or less, and further preferably 0.15 or more and 0.25 or less.

The c in the above formula 1 is preferably 0.01 or more and 0.15 or less, more preferably 0.02 or more and 0.10 or less, and further preferably 0.03 or more and 0.08 or less.

The d in the above formula 1 is preferably 0.002 or more and 0.1 or less, more preferably 0.004 or more and 0.08 or less, further preferably 0.006 or more and 0.05 or less, and 0.01 or more and 0.03. The following are even more preferred. Further, d may be more preferably 0.02 or less, and may be further preferably 0.02 or more.

By setting each of the above a to d within the above range, it is possible to further suppress the generation of oxygen gas during charging and extend the charge / discharge cycle life when used in a non-aqueous electrolyte power storage element.

It is preferable that M ¹ in the above formula 1 contains Co, and Co is more preferable.

As M ² in the above formula 1, Group 13 elements and Group 14 elements are preferable, Group 14 elements are more preferable, and Si is even more preferable.

The positive electrode active material (γ) may or may not have a crystal structure, but preferably has a crystal structure, and may have an inverted fluorite-type crystal structure. More preferred.

In the X-ray diffraction diagram using CuKα rays of the positive electrode active material (β) and the positive electrode active material (γ) according to the embodiment of the present invention, the diffraction angle 2θ is the diffraction angle 2θ with respect to the integrated intensity of the diffraction peak near 33 °. The ratio of the integrated intensities of the diffraction peaks near 44 ° is preferably more than 0.00 and 2 or less, more preferably 0.05 or more and 1.6 or less, and further preferably 0.1 or more and 1.0 or less. By setting the ratio of the integrated strengths in the above range, when used in a non-aqueous electrolyte power storage element, the generation of oxygen gas during charging can be further suppressed, and the charge / discharge cycle life can be further extended. Further, by setting the ratio of the integrated strength to the upper limit or less, the initial discharge capacity of the positive electrode active material tends to increase. When used in a non-aqueous electrolyte power storage element, the ratio of the integrated strengths may be more preferably 0.5 or less from the viewpoint of further suppressing the generation of oxygen gas during charging. From the viewpoint of extending the charge / discharge cycle life, the ratio of the integrated strengths may be more preferably 0.5 or more.

The lattice constant a of the positive electrode active material (β) and the positive electrode active material (γ) according to the embodiment of the present invention is preferably 0.460 nm or more and 0.465 nm or less, more preferably 0.461 nm or more and 0.464 nm or less. It is more preferably 0.462 nm or more and 0.463 nm or less. When the lattice constant a is in the above range, it is presumed that the contents of the first element, the second element and the element A are in an appropriate range, and when used in a non-aqueous electrolyte power storage element, oxygen gas is generated during charging. Can be further suppressed and the charge / discharge cycle life can be extended.

The volume resistivity of the positive electrode active material (β) and the positive electrode active material (γ) according to the embodiment of the present invention is preferably 25 Ω · cm or less, more preferably 20 Ω · cm or less, and more preferably 15 Ω · cm. It is more preferably cm or less. Although the positive electrode active material (β) and the positive electrode active material (γ) are Li _2O -based positive electrode active materials, they may have a sufficiently low volume resistance because they contain nitrogen, which is an element A. When the volume resistivity of the positive electrode active material (β) and the positive electrode active material (γ) is not more than the above upper limit, the cycle life can be extended, and the input / output performance of the non-aqueous electrolyte power storage element can be improved. .. The volume resistivity of the positive electrode active material (β) and the positive electrode active material (γ) may be, for example, 1 Ω · cm or more, or 5 Ω · cm or more.
The volume resistivity of the positive electrode active material is measured by using a tablet molding machine with an inner wall surface of 11.25 mmφ, which has an inner wall surface coated with insulation, in a glove box with an argon atmosphere, and is pressed at a pressure of 30 MPa with a hydraulic press machine. In this state, the resistance value is measured with a resistance meter (AC four-terminal method, measurement frequency 1 kHz). First, the measurement is performed without putting the sample in the tablet molder, and the resistance value is defined as the blank resistance. Next, 130 mg of the positive electrode active material powder, which is a sample, is put into the tablet molder, and the resistance value is measured. The volume resistivity is calculated from the resistance value obtained by subtracting the blank resistance from the measured resistance value and the thickness of the sample after pressing measured with a caliper.

The lattice constant of the positive electrode active material according to the embodiment of the present invention is a ₁ , the lattice constant of the compound having a composition in which all the elements A in the positive electrode active material are replaced with oxygen and having an inverted fluorite-type crystal structure. When is a ₂ , the ratio a ₁ / a ₂ may be, for example, more than 1.00000, preferably more than 1.0000, and may be more than 1.00005 or more than 1.00010. .. On the other hand, the ratio a ₁ / a ₂ may be 1.001 or less, preferably less than 1.0005, more preferably less than 1.0003, and even more preferably less than 1.0002.

When the ratio a ₁ / a ₂ of the lattice constant is in the above range, it means that a sufficient amount of element A is contained within a range in which the stability of the crystal structure is not significantly impaired. The discharge capacity of the positive electrode active material after the charge / discharge cycle becomes larger.

The positive electrode active material according to the embodiment of the present invention preferably satisfies the following formula 2.
1.000 <a ₁ / a ₂ <1.005 ・・・ 2
In Equation 2, a ₁ is the lattice constant of the positive electrode active material. _a2 is a lattice constant of a compound having a composition in which all the elements A in the positive electrode active material are replaced with oxygen and having an inverted fluorite-type crystal structure.

When the above formula 2 is satisfied, it means that the positive electrode active material contains an appropriate amount of element A, and the discharge capacity of the positive electrode active material after the charge / discharge cycle becomes larger.

In the X-ray diffraction diagram using CuKα rays of the positive electrode active material according to the embodiment of the present invention, the half width of the diffraction peak near the diffraction angle 2θ of 33 ° is preferably 0.3 ° or more, preferably 0.5 ° or more. More preferably, 1.0 ° or more is further preferable. When the half-value width of the diffraction peak near the diffraction angle 2θ is 33 ° or more is equal to or greater than the above lower limit, the generation of oxygen gas during charging is further suppressed when used in a non-aqueous electrolyte power storage element, and a more sufficient charge / discharge cycle life is achieved. It can be a positive electrode active material having. By manufacturing the positive electrode active material by a manufacturing method that is treated by the mechanochemical method described later, the half-value width of such a diffraction peak tends to be large. The half width of the diffraction peak in which the diffraction angle 2θ is around 33 ° may be, for example, 5 ° or less, 3 ° or less, or 2 ° or less.

The positive electrode active material according to one embodiment of the present invention is usually particles (powder). The average particle size of the positive electrode active material is preferably, for example, 0.01 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material to the above lower limit or more, the production or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to be equal to or less than the above upper limit, the electron conductivity when the positive electrode active material layer is formed is improved. When a complex of a positive electrode active material and another material is used, the average particle size of the complex is taken as the average particle size of the positive electrode active material. The "average particle size" means the average value of the particle size measured by extracting 1000 particles from a scanning electron microscope (SEM) image while avoiding extremely large particles and extremely small particles. The particle size of each particle in the measurement from this SEM image is obtained as follows. The shortest diameter passing through the center of the minimum circumscribed circle of each particle is defined as the minor diameter, and the diameter passing through the center and orthogonal to the minor diameter is defined as the major diameter. The average value of the major axis and the minor axis is taken as the particle size of each particle. When there are two or more shortest diameters, the one with the longest orthogonal diameter is the shortest diameter.

A crusher, a classifier, etc. are used to obtain powder with 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 a non-aqueous solvent (dimethyl carbonate or the like) used for the non-aqueous electrolyte described later or an organic solvent such as N-methylpyrrolidone 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 and wet types.

<Manufacturing method of positive electrode active material>
The positive electrode active material according to the embodiment of the present invention can be produced, for example, by the following production method. That is, the method for producing a positive electrode active material according to an embodiment of the present invention comprises treating a material containing lithium, oxygen, a first element and element A by a mechanochemical method, wherein the first element is chromium or manganese. , At least one selected from the group consisting of iron, cobalt, nickel and copper, and the element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine.

The method for producing a positive electrode active material according to another embodiment of the present invention comprises treating a material containing lithium, oxygen, a first element, a second element and an element A by a mechanochemical method, and the first element is described above. Is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper, and the second element is from the group consisting of group 13 element, group 14 element, phosphorus, antimony, bismuth and tellurium. It is at least one selected, and the element A is nitrogen.

Specific examples and suitable examples of the positive electrode active material produced by the production method are the same as the specific examples and suitable examples of the positive electrode active material according to the embodiment of the present invention.

The mechanochemical method (also referred to as mechanochemical treatment) is a synthetic method using a mechanochemical reaction. The mechanochemical reaction refers to a chemical reaction such as a crystallization reaction, a solid solution reaction, or a phase transition reaction that utilizes high energy locally generated by mechanical energy such as friction and compression in the crushing process of a solid substance. In this production method, it is presumed that the treatment by the mechanochemical method causes a reaction in which the first element and element A or the first element, the second element and the element A are solid-dissolved in the crystal structure of Li _2O . Will be done. Examples of the apparatus for processing by the mechanochemical method include crushing / dispersing machines such as ball mills, bead mills, vibration mills, turbo mills, mechanofusions, and disc mills. Of these, a ball mill is preferable. As the balls and mill containers used in the ball mill, those made of tungsten carbide (WC), those made of zirconium oxide (ZrO ₂ ), and the like can be preferably used.

When processing with a ball mill, the mill rotation speed during processing can be, for example, 100 rpm or more and 1,000 rpm or less. The processing time can be, for example, 0.1 hour or more and 100 hours or less. Further, this treatment can be carried out in an atmosphere of an inert gas such as argon or an atmosphere of an active gas such as air, but it is preferably carried out in an atmosphere of an inert gas. Here, the inert gas refers to a gas that is inert to the material to be subjected to the ball mill treatment and the obtained positive electrode active material.

The positive electrode active material obtained by the production method preferably has an inverted fluorite-type crystal structure. The positive electrode active material obtained by treating with the mechanochemical method as in the production method has a half-value width of a diffraction peak near 33 ° in the diffraction angle 2θ in an X-ray diffraction diagram using CuKα rays, which is 0.3 °. It tends to be larger than the above.

The material to be treated by the mechanochemical method is usually composed of one kind or two or more kinds of compounds. In a material composed of one kind or two or more kinds of compounds, lithium, oxygen, the first element and element A or lithium, oxygen, the first element, the second element are used as the elements constituting these compounds. And element A may be contained.

The compound and the like constituting the above material may be an oxide, a compound other than the oxide, or a simple substance. Further, these compounds and the like may be crystalline or amorphous. Specific examples of the compounds constituting the above materials include lithium oxides such as Li _2O .
Lithium-first element composite oxides such as Li ₆ CoO ₄ , Li ₅ CrO ₄ , Li ₅ FeO ₄ , Li ₆ NiO ₄ , Li ₆ CuO ₄ , Li ₆ MnO ₄ , etc.
Li ₅ AlO ₄ , Li ₅ GaO ₄ , Li ₅ InO ₄ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , Li ₄ SnO ₄ , Li ₃ BO ₃ , Li ₅ _SbO ₅ , Li ₅ _BiO ₆ etc. Lithium and second element composite oxide,
Li _5.5 Co _0.5 Al _0.5 O ₄ , Li _5.8 Co _0.8 Al _0.2 O ₄ , LiCo _0.5 B _0.5 O ₂ , LiCo _0.8 B _0.2 O ₂ , Li _5.5 Co _0.5 B _0.5 O ₄ , Li _5.8 Co _0.8 B _0.2 O ₄ , Li _5.8 Co _0.8 Si _0.2 O ₄ and other lithium Composite oxide of the first element and the second element,
Oxides of the first element such as CoO, Co ₃ O ₄ , Fe ₂ O ₃ , MnO ₂ , NiO, Cu ₂ O, Cu O, etc.
Oxides of second elements such as B ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , GeO ₂ , SnO ₂ , etc.
Li ₃ N, Li _3-x Co _x N (Li _2.6 Co _0.4 N, etc.), CoN _x , CoF ₂ , CoCl ₂ , CoS, CoS ₂ , CoSe, CoTe, CoBr, CoI ₂ , Li ₂ S , Li ₂ Se, LiF, LiCl, LiBr and LiI, Si _{3N 4} _, BN and other compounds containing element A.
In addition, at least one of a compound of a first element and a second element, lithium, a first element, a second element and an element A, and an element other than lithium, oxygen, the first element, the second element and the element A. Compounds and the like may be used.

<Positive electrode>
The positive electrode according to the embodiment of the present invention is a positive electrode for a non-aqueous electrolyte power storage element containing the positive electrode active material according to the above-mentioned embodiment of the present invention. The positive electrode has a positive electrode base material and a positive electrode active material layer arranged directly on the positive electrode base material or via an intermediate layer.

The positive electrode base material has conductivity. Having "conductive" means that the volume resistivity measured according to JIS-H-0505 (1975) is ¹⁰⁷ Ω · cm or less, and "non-conductive" means. It means that the volume resistivity is more than ¹⁰⁷ Ω · cm. As the material of the positive electrode base material, metals such as aluminum, titanium, tantalum, and stainless steel or alloys thereof are used. Among these, aluminum and aluminum alloys are preferable from the viewpoint of the balance between potential resistance, high conductivity and cost. Further, examples of the formation form of the positive electrode base material include foil, a vapor-deposited film, and the like, and foil is preferable from the viewpoint of cost. That is, aluminum foil or aluminum alloy foil is preferable as the positive electrode base material. Examples of aluminum or aluminum alloy include A1085P and A3003P specified in JIS-H-4000 (2014).

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, 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 in the above range, it is possible to increase the strength of the positive electrode base material and the energy density per volume of the power storage element. The "average thickness" of the positive electrode base material and the negative electrode base material described later means a value obtained by dividing the punched mass when punching a base material having a predetermined area by the true density and the punched area of the base material.

The intermediate layer is a coating layer on the surface of the positive electrode base material, and contains a conductive agent such as carbon particles to reduce the contact resistance between the positive electrode base material 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 is formed from a so-called positive electrode mixture containing a positive electrode active material. Further, the positive electrode mixture forming the positive electrode active material layer contains optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary.

The positive electrode active material includes the positive electrode active material according to the embodiment of the present invention described above. The positive electrode active material may contain a known positive electrode active material other than the positive electrode active material according to the embodiment of the present invention. The content of the positive electrode active material according to the embodiment of the present invention in the positive electrode active material layer is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and 70% by mass or more. Especially preferable. As described above, by increasing the content ratio of the positive electrode active material in the positive electrode active material layer, the effect of using the positive electrode active material is particularly sufficiently exhibited. On the other hand, the content of the positive electrode active material according to the embodiment of the present invention in the positive electrode active material layer may be 99% by mass or less, 98% by mass or less, 90% by mass or less, or 80% by mass or less.

The conductive agent is not particularly limited as long as it is a conductive material. Examples of such a conductive agent include carbonaceous materials; metals; conductive ceramics and the like. Examples of carbonaceous materials include graphite and carbon black. Examples of the type of carbon black include furnace black, acetylene black, and ketjen black. Among these, carbonaceous materials are preferable from the viewpoint of conductivity and coatability. Of these, acetylene black and ketjen black are preferable. Examples of the shape of the conductive agent include powder, sheet, and fibrous.

The positive electrode active material and the conductive agent may be combined. Examples of the method of compositing include a method of mechanically milling a mixture containing a positive electrode active material and a conductive agent, which will be described later.

The content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 40% by mass or less, more preferably 3% by mass or more and 30% by mass or less, and further preferably 5% by mass or more or 10% by mass or more. .. By setting the content of the conductive agent in the above range, the energy density of the power storage element can be increased.

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

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, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the binder in the above range, the positive electrode active material can be stably held.

Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium, it is preferable to inactivate this functional group by methylation or the like in advance.

The above filler is not particularly limited. Fillers include polyolefins such as polypropylene and polyethylene, silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, inorganic oxides such as aluminosilicate, magnesium hydroxide, calcium hydroxide, and water. Hydroxides such as aluminum oxide, 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 and zeolite. , Apatite, Kaolin, Murite, Spinel, Olivin, Sericite, Bentonite, Mica and other mineral resource-derived substances or man-made products thereof.

The positive electrode active material layer is a typical non-metal element such as B, N, P, F, Cl, Br, I, Li, Na, Mg, Al, Si, K, Ca, Zn, Ga, Ge, Sn, Sr, Typical metal elements such as Ba and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb and W are used as positive electrode active materials, conductive agents, binders and thickeners. , May be contained as a component other than the filler.

<Manufacturing method of positive electrode>
The positive electrode according to the embodiment of the present invention can be manufactured by, for example, the following method. That is, the method for producing the positive electrode according to the embodiment of the present invention is the positive electrode active material obtained by the method for producing the positive electrode active material according to the embodiment of the present invention or the positive electrode active material according to the embodiment of the present invention. Provided to be used to make a positive electrode.

The positive electrode can be produced, for example, by applying the positive electrode mixture paste directly to the positive electrode base material or via an intermediate layer and drying it to form a positive electrode active material layer. The positive electrode mixture paste contains each component constituting the positive electrode mixture, such as a positive electrode active material and optional components such as a conductive agent and a binder. The positive electrode mixture paste may further contain a dispersion medium. Further, the positive electrode active material layer may be formed by molding a positive electrode mixture containing no dispersion medium.

In the production of the positive electrode, when the positive electrode active material and the conductive agent are mixed, it is preferable to mechanically mill the mixture containing the positive electrode active material and the conductive agent. As described above, when the positive electrode active material according to the embodiment of the present invention is used, sufficient charge / discharge performance and the like are provided by performing the mechanical milling treatment in the state of a mixture containing the positive electrode active material and the conductive agent. A positive electrode that can be used as a non-aqueous electrolyte power storage element can be manufactured with high certainty.

Here, the mechanical milling process refers to a process of pulverizing, mixing, or compounding by applying mechanical energy such as impact, shear stress, and friction. Examples of the device for performing the mechanical milling process include crushing / dispersing machines such as ball mills, bead mills, vibration mills, turbo mills, mechanofusions, and disc mills. Of these, a ball mill is preferable. As the balls and mill containers used in the ball mill, those made of tungsten carbide (WC), those made of zirconium oxide (ZrO ₂ ), and the like can be preferably used. The mechanical milling treatment referred to here does not need to be accompanied by a mechanochemical reaction. It is presumed that such mechanical milling treatment composites the positive electrode active material and the conductive agent, and improves the conductivity.

When processing with a ball mill, the mill rotation speed during processing can be, for example, 100 rpm or more and 1,000 rpm or less. The processing time can be, for example, 0.1 hour or more and 100 hours or less. Further, this treatment can be carried out in an inert gas atmosphere such as argon or in an active gas atmosphere, but it is preferably carried out in an inert gas atmosphere.

<Non-water electrolyte power storage element>
The non-aqueous electrolyte power storage element according to the embodiment of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. Hereinafter, as an example of the non-aqueous electrolyte power storage element, a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as “secondary battery”) will be described. The positive electrode and the negative electrode usually form an electrode body that is alternately superposed by laminating or winding through a separator. The electrode body is housed in a container, and the container is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. Further, as the container, a known metal container, resin container, or the like usually used as a container for a secondary battery can be used.

(Positive electrode)
The positive electrode provided in the secondary battery is the positive electrode according to the above-described embodiment of the present invention.

(Negative electrode)
The negative electrode has a negative electrode base material and a negative electrode active material layer arranged directly on the negative electrode base material or via an intermediate layer. The intermediate layer may have the same structure as the intermediate layer of the positive electrode.

The negative electrode base material may have the same configuration as the positive electrode base material, but as the material, a metal such as copper, nickel, stainless steel, nickel-plated steel or an alloy thereof is used, and copper or a copper alloy is used. preferable. That is, a copper foil or a copper alloy foil is preferable as the negative electrode base material. Examples of the 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, 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 in the above range, it is possible to increase the energy density per volume and mass of the non-aqueous electrolyte power storage element while increasing the strength of the negative electrode base material.

The negative electrode active material layer is generally formed of a so-called negative electrode mixture containing a negative electrode active material. Further, the negative electrode mixture forming the negative electrode active material layer contains optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary. As any component such as a conductive agent, a binder, a thickener, and a filler, the same one as that of the positive electrode active material layer can be used. The negative electrode active material layer may be a layer substantially composed of only a negative electrode active material such as metallic Li.

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

The negative electrode active material can be appropriately selected from known negative electrode active materials. For example, as a negative electrode active material for a lithium ion secondary battery, a material capable of occluding 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 O ₁₂ ; Titanium-containing oxides such as LiTIO _{2 and} TiNb _2O ₇ ; polyphosphate compounds; silicon carbide; carbon materials such as graphite (graphite) and non-graphitric carbon (easy graphitable carbon or non-graphitizable carbon) can be mentioned. Be done. Among these materials, graphite and non-graphitic carbon are preferable. In the negative electrode active material layer, one of these materials may be used alone, or two or more thereof may be mixed and used.

“Graphite” refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of (002) planes determined by X-ray diffraction method 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" refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane determined by the X-ray diffraction method before charging / discharging or in a discharged state of 0.34 nm or more and 0.42 nm or less. .. Examples of non-graphitizable carbon include non-graphitizable carbon and easily graphitizable carbon. Examples of the non-planar carbon include a resin-derived material, a petroleum pitch or 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 "discharge state" of the carbon material is a state in which the open circuit voltage is 0.7 V or more in a half cell using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and a metal Li as a counter electrode. say. Since the potential of the metal Li counter electrode in the open circuit state is substantially equal to the redox potential of Li, the open circuit voltage in the single pole battery is substantially the same as the potential of the negative electrode containing the carbon material with respect to the redox potential of Li. .. That is, the fact that the open circuit voltage in the single-pole battery is 0.7 V or more means that the carbon material, which is the negative electrode active material, sufficiently releases lithium ions that can be occluded and discharged by charging and discharging. ..

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

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

When the form of the negative electrode active material is 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, for example, a carbon material, the average particle size thereof may be preferably 1 μm or more and 100 μm or less. When the negative electrode active material is a metal, a metalloid, a metal oxide, a metalloid oxide, a titanium-containing oxide, a polyphosphate compound or the like, the average particle size thereof may be preferably 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 having a predetermined particle size. When the negative electrode active material is metallic Li, the form may be foil-shaped or plate-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, for example, when the negative electrode active material layer is formed of a negative electrode mixture. preferable. 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. When the negative electrode active material is metallic Li, the content of the negative electrode active material in the negative electrode active material layer may be 99% by mass or more, or may be 100% by mass.

(Separator)
The separator can be appropriately selected from known separators. As the separator, 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 include woven fabrics, non-woven fabrics, and porous resin films. Among these forms, 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, 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, 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 the atmosphere, and a mass loss of 5% when heated from room temperature to 800 ° C. in the atmosphere. The following are more preferable. Examples of the material of the heat-resistant particles include inorganic compounds. Examples of the inorganic compound include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide and aluminosilicate; magnesium hydroxide, calcium hydroxide and water. Hydroxides such as aluminum oxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ion crystals such as calcium fluoride, barium fluoride and barium titanate 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 device.

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" is a volume-based value and means a measured value with a mercury porosity meter.

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

The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, 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, EC 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.

It is preferable to use at least one of the cyclic carbonate and the chain carbonate as the non-aqueous solvent, and it is more preferable to use the cyclic carbonate and the 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.

Lithium salt is used as the electrolyte salt. Sodium salt, potassium salt, magnesium salt, onium salt and the like may be used in combination.

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, and more preferably 0.3 mol / dm ³ or more and 2.0 mol / dm ³ or less. , 0.5 mol / dm ³ or more and 1.7 mol / dm ³ or less is more preferable, and 0.7 mol / dm ³ or more and 1.5 mol / dm ³ or less is particularly preferable. 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 electrolytic solution may contain an additive. Examples of the additive include aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, and partially hydrides of turphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; 2-fluorobiphenyl, o. -Partial halides of the above aromatic compounds such as cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like. Halogenized anisole compounds; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic acid anhydride; ethylene sulfone, propylene sulfite, dimethyl sulfite, dimethyl sulfate, ethylene sulfate, Sulfone, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis (2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl- Examples thereof include 2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyldisulfide, dipyridinium disulfide, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetrakistrimethylsilyl titanate 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 more preferably 0.1% by mass or more and 7% by mass or less with respect to the total mass of the non-aqueous electrolytic solution. , 0.2% by mass or more and 5% by mass or less is more preferable, and 0.3% by mass or more and 3% by mass or less is particularly preferable. 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 lithium ion conductivity and being solid at room temperature (for example, 15 ° C to 25 ° C). The solid electrolyte may further have ionic conductivity such as sodium and potassium. Examples of the solid electrolyte include a sulfide solid electrolyte, an oxide solid electrolyte, an oxynitride solid electrolyte, a polymer solid electrolyte and the like.

Examples of the lithium ion secondary battery include Li ₂ SP ₂ S ₅ , LiI-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 non-aqueous electrolyte power storage element 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 non-aqueous electrolyte power storage element 1 as an example of a square battery. The figure is a perspective view of the inside of the container. The electrode body 2 having the positive electrode and the negative electrode wound around the separator is housed in the square container 3. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 41. The negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 51.

<Power storage device>
The non-aqueous electrolyte power storage element of the present embodiment is 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 source. It can be mounted on a storage power source or the like as a power storage unit (battery module) composed of a plurality of non-aqueous electrolyte power storage elements 1 assembled together. In this case, the technique according to the embodiment of the present invention may be applied to at least one non-aqueous electrolyte power storage element included in the power storage unit.

The power storage device according to an embodiment of the present invention is a power storage device including a plurality of non-aqueous electrolyte power storage elements and one or more non-water electrolyte power storage elements according to one aspect of the present invention. 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 includes a bus bar (not shown) for electrically connecting two or more non-aqueous electrolyte power storage elements 1, a bus bar (not shown) for electrically connecting two or more power storage units 20 and the like. May be good. The power storage unit 20 or the power storage device 30 may include a condition monitoring device (not shown) for monitoring the state of one or more non-aqueous electrolyte power storage elements.

<Manufacturing method of non-aqueous electrolyte power storage element>
The non-aqueous electrolyte power storage device according to the embodiment of the present invention can be manufactured by using the positive electrode according to the embodiment of the present invention. The method for manufacturing a non-aqueous electrolyte power storage element according to an embodiment of the present invention includes a method for manufacturing a positive electrode according to an embodiment of the present invention.

For example, the method for manufacturing the non-aqueous electrolyte power storage element includes producing the above-mentioned positive electrode, producing a negative electrode, preparing a non-aqueous electrolyte, and laminating or winding a positive electrode and a negative electrode via a separator. It comprises forming the electrode bodies alternately superimposed, accommodating the positive electrode body and the negative electrode body (electrode body) in a container, and injecting the non-aqueous electrolyte into the container. After the injection, the non-aqueous electrolyte power storage element can be obtained by sealing the injection port.

<Other embodiments>
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 non-aqueous electrolyte storage element is used as a chargeable / dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) has been described. The capacity etc. are arbitrary. The non-aqueous electrolyte power storage element of the present invention can also be applied to capacitors such as various non-aqueous electrolyte secondary batteries, electric double layer capacitors and lithium ion capacitors.

In the above embodiment, the electrode body in which the positive electrode and the negative electrode are laminated via the separator has been described, but the electrode body does not have to be provided with the separator. 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, but the present invention is not limited to the following examples.

[Example 1]
[Example 1-1]
In an argon atmosphere, Li ₂ O, Co ₃ O ₄ and Li ₃ N were mixed at a molar ratio of 4.98: 0.33: 0.05, and an internal volume containing 250 g of a tungsten carbide ball having a diameter of 5 mm was contained. It was placed in an 80 mL tungsten carbide mill container and covered. This was set in a planetary ball mill device (“pulveristte 6” manufactured by FRITSCH), and dried at a revolution speed of 500 rpm for 12 hours. By such treatment by the mechanochemical method, the positive electrode active material (Li _1.58 Co _0.157 O _0.988 N _0.0078 ) of Example 1-1 was obtained.

[Examples 1-2 to 1-5 and Comparative Example 1-1]
Examples 1-2 to 1-5 and Comparative Example 1 are the same as in Example 1-1 except that the types of materials used and the mixing amount ratio (molar ratio) thereof are as shown in Tables 1 and 2. Each positive electrode active material of -1 was obtained. Tables 1 and 2 also show the composition formulas and the like of the obtained positive electrode active material.

(X-ray diffraction measurement of positive electrode active material)
For each positive electrode active material obtained in the above Examples and Comparative Examples, X-ray diffraction measurement was performed by the method using the above-mentioned SPring-8 powder X-ray diffraction beamline. It was confirmed that all of them had the same crystal structure (reverse fluorite type crystal structure) as Li ₂ O as the main phase. Tables ₁ and 2 show the lattice constants a1 of the positive electrode active materials of the above-mentioned Examples and the above-mentioned Comparative Examples. Further, for each positive electrode active material of the above-mentioned example, a compound having a composition in which element A (nitrogen or fluorine) is completely replaced with oxygen and having an inverted fluorite-type crystal structure (that is, the positive electrode activity of Comparative Example 1-1). The ratio (a ₁ / a ₂ ) of the substance) to the lattice constant a ₂ is also shown in Tables 1 and 2. The lattice constants of the positive electrode active materials of Examples and Comparative Examples in Table 1 were obtained based on the X-ray diffraction pattern measured on the same day, and the lattice constants of the positive electrode active materials of Examples and Comparative Examples in Table 2 were obtained. The constants were also obtained based on the X-ray diffraction pattern measured on the same day, but the lattice constants of the positive electrode active materials of Examples and Comparative Examples in Table 1 and the positive electrode active materials of Examples and Comparative Examples in Table 2 were obtained. Each lattice constant is obtained based on an X-ray diffractogram measured on another day. Therefore, as described above, the values of the lattice constants are different even for the positive electrode active materials of Comparative Example 1-1 having the same composition, for example. As shown in Tables 1 and 2, it can be confirmed that the lattice constant ratio (a ₁ / a ₂ ) increases as the content of the element A (nitrogen or fluorine) increases.

(Preparation of positive electrode)
Under an argon atmosphere, the positive electrode active material obtained in each Example and Comparative Example, Ketchen Black, and PTFE are mixed using a mortar at a mass ratio of 75:20: 5, and molded to form a positive electrode having a diameter of 6 mm. A mixture sheet was prepared. This positive electrode mixture sheet was pressure-bonded to mesh-shaped aluminum as a positive electrode base material to obtain a positive electrode.

(Manufacturing of non-aqueous electrolyte power storage element (evaluation cell))
LiPF ₆ was dissolved in a non-aqueous solvent in which EC and EMC were mixed at a volume ratio of 30:70 at a concentration of 1 mol / dm ³ to prepare a non-aqueous electrolyte. Further, a metallic lithium having a diameter of 15 mm was prepared as a negative electrode, and a polypropylene microporous film was prepared as a separator. Using these, a non-aqueous electrolyte power storage device (evaluation cell) was manufactured. All the operations from the production of the positive electrode to the production of the evaluation cell were performed in an argon atmosphere. In addition, two non-aqueous electrolyte power storage elements (evaluation cells) using the positive electrode active material of Comparative Example 1-1 were produced.

(Charging / discharging test)
The evaluation cells obtained using the positive electrode active materials of Examples 1-1 to 1-3 and Comparative Example 1-1 were subjected to a charge / discharge test in a glove box under an argon atmosphere in an environment of 25 ° C. rice field. The current density was 30 mA / g per mass of the positive electrode active material contained in the positive electrode, and constant current (CC) charging / discharging was performed. The charging was started, and the charging was terminated when the upper limit electric amount of 300 mAh / g per mass of the positive electrode active material was reached. The discharge was terminated when the lower limit voltage of 1.5 V was reached. This charge / discharge cycle was repeated 20 cycles. Table 1 shows the discharge capacity at the 20th cycle.

The evaluation cells obtained using the positive electrode active materials of Examples 1-4 and Comparative Example 1-1 were subjected to a charge / discharge test in a glove box under an argon atmosphere in an environment of 25 ° C. The current density was 100 mA / g per mass of the positive electrode active material contained in the positive electrode, and constant current (CC) charging / discharging was performed. The charging was started, and the charging was terminated when the upper limit electric amount of 300 mAh / g per mass of the positive electrode active material was reached. The discharge was terminated when the lower limit voltage of 1.5 V was reached. This charge / discharge cycle was repeated 20 cycles. Table 2 shows the discharge capacity at the 20th cycle.

As shown in Tables 1 and 2, in the non-aqueous electrolyte power storage element using each positive electrode active material of Examples 1-1 to 1-4 containing the element A (nitrogen or fluorine), the element A is contained. It was confirmed that the discharge capacity after the charge / discharge cycle was larger than that of the non-aqueous electrolyte power storage element using the positive electrode active material of Comparative Example 1-1, which was not used.

[Example 2]
[Synthesis Example 1] Synthesis of Li ₆ CoO ₄ Li ₂ O and CoO were mixed at a molar ratio of 3: 1 and then fired at 900 ° C. for 20 hours under a nitrogen atmosphere to synthesize Li ₆ CoO ₄ .

[Synthesis Example 2] Synthesis of Li ₄ SiO ₄ Li ₂ O and SiO ₂ were mixed at a molar ratio of 2: 1 and then calcined at 900 ° C. for 20 hours under a nitrogen atmosphere to obtain Li ₄ SiO ₄ .

[Example 2-1]
After mixing the obtained Li ₆ CoO ₄ (1.6351 g), the obtained Li ₄ SiO ₄ (0.3402 g) and Li ₃ N (0.0247 g), it is made of tungsten carbide (WC) under an argon atmosphere. It was put into a WC mill container together with a ball, and treated with a planetary ball mill device (“pulveristte 5” manufactured by FRITSCH) at a rotation speed of 400 rpm for 2 hours. By such treatment by the mechanochemical method, the positive electrode active material of Example 2-1 (Li _1.431 Co _0.194 Si _0.056 ON _0.014 ) was obtained.

[Examples 2-2, 2-3, Comparative Example 2-1]
The positive electrode active materials of Examples 2-2, 2-3 and Comparative Example 2-1 were obtained in the same manner as in Example 2-1 except that the materials used were as shown in Table 3. Table 3 also shows the composition formulas of the obtained positive electrode active material.

(X-ray diffraction measurement of positive electrode active material)
X-ray diffraction measurements using CuKα rays were performed on each of the positive electrode active materials of Examples 2-1 to 2-3 and Comparative Example 2-1. Using an airtight sample holder for X-ray diffraction measurement, a powder sample of each positive electrode active material was filled under an argon atmosphere. The X-ray diffractometer used, the measurement conditions, and the data processing method were as described above. It was confirmed that all of them had the same crystal structure (inverted fluorite type crystal structure) as Li ₂ O as the main phase. FIG. 3 shows an X-ray diffraction diagram of each positive electrode active material. Further, the diffraction angle 2θ of each positive electrode active material obtained from the X-ray diffraction measurement is the half-value width of the diffraction peak near 33 °, and the diffraction angle 2θ is the diffraction around 44 ° with respect to the integrated intensity of the diffraction peak near 33 °. Table 3 shows the ratio of the integrated intensity of the peaks and the lattice constant a.

(Measurement of volume resistivity of positive electrode active material)
By the above method, the volume resistivity of each positive electrode active material of Example 2-2 and Comparative Example 2-1 was measured. The volume resistivity of the positive electrode active material of Example 2-2 was 9.5 Ω · cm, and the volume resistivity of Comparative Example 2-1 was 32.3 Ω · cm. It was confirmed that the electron conductivity of the positive electrode active material was improved by containing nitrogen.

(Oxygen gas generation test during charging)
An oxygen gas generation test during charging was performed using each of the positive electrode active materials of Examples 2-1 to 2-3 and Comparative Example 2-1.
First, a positive electrode was produced by the following procedure. Under an argon atmosphere, 1.125 g of the positive electrode active material and 0.300 g of Ketjen black were mixed, placed in a WC mill container having an internal volume of 80 mL containing 250 g of WC balls having a diameter of 5 mm, and covered. This was set in the same planetary ball mill device as above, and dried and mixed at a revolution speed of 200 rpm for 30 minutes to prepare a mixed powder of the positive electrode active material and Ketjen black. 95 parts by mass of each of the above mixed powders and 5 parts by mass of polytetrafluoroethylene powder were kneaded in an agate mortar and molded into a sheet. This sheet was punched into a disk shape having a diameter of 12 mmφ to prepare a positive electrode sheet having a mass of about 0.01 g. Each of the above positive electrode sheets was pressure-bonded to one side of a positive electrode base material (diameter 21 mmφ) made of aluminum mesh to obtain a positive electrode.
Next, a non-aqueous electrolyte power storage element for an oxygen gas generation test during charging was manufactured. In a glove box with an argon atmosphere, the positive electrode and a 25 mm square metal lithium negative electrode are laminated via a polypropylene microporous film separator, stored in an exterior body made of a metal resin composite film, and filled with 300 μL of non-aqueous electrolyte. did. The non-aqueous electrolyte used was prepared by dissolving LiPF ₆ at a concentration of 1 mol / dm ³ in a non-aqueous solvent in which EC, DMC and EMC were mixed at a volume ratio of 30:35:35. The exterior body made of a metal resin composite film is provided with an opening at the upper part so that the non-aqueous electrolyte does not leak, and the non-water container is provided with a gas inlet and a gas discharge port and has an internal volume of 0.5 dm ³ . The entire electrolyte storage element was enclosed, and the inside of the container was sufficiently replaced with He gas. He gas was introduced from the gas inlet at a flow rate of 5 × 10 ^-3 dm ³ / min, and the outflow gas from the gas outlet was introduced into the gas chromatograph mass spectrometry (GC-MS) apparatus from the sample inlet. The capillary column used in the gas chromatograph (GC) section of the GC-MS apparatus was a dummy column having no gas component separation function, and the column temperature was 80 ° C. With such a configuration, the outflow gas, which may be a state in which a plurality of gas components are mixed, is introduced into the mass spectrometer (MS) section with the component composition as it is, and the plurality of gas components are simultaneously present in real time in the MS section. Be analyzed.
Each of the obtained non-aqueous electrolyte power storage elements was charged with a constant current (CC) at a current density of 50 mA / g per mass of the positive electrode active material contained in the positive electrode under an environment of 25 ° C. For the outflow gas during charging, the intensity of m / z = 32 caused by oxygen gas was continuously measured by the MS unit. The time when the intensity of m / z = 32 began to increase remarkably was defined as the time when the generation of oxygen gas was confirmed, and the amount of electricity charged at that time was defined as the "starting point of oxygen gas generation". The above charging was continued until the oxygen gas generation start point could be determined. FIG. 4 shows a graph showing a change in intensity (O ₂ gas evolution) of m / z = 32 with respect to the amount of electricity charged during charging of each non-aqueous electrolyte power storage element. Table 3 shows the amount of charging electricity (oxygen gas generation start point) at the time when the generation of oxygen gas is confirmed in each non-aqueous electrolyte power storage element.

(Charge / discharge cycle test)
A charge / discharge cycle test was performed using the positive electrode active materials of Examples 2-1 to 2-3 and Comparative Example 2-1.
First, a positive electrode was prepared by the same procedure as the above-mentioned oxygen gas generation test during charging. Using the obtained positive electrode, metallic lithium having a diameter of 22 mmφ was used as a negative electrode, laminated via a polypropylene microporous membrane separator and stored in a container, and 300 μL of non-aqueous electrolyte was injected to prepare a non-aqueous electrolyte power storage element. The non-aqueous electrolyte power storage element was manufactured in a glove box having an argon atmosphere. As the non-aqueous electrolyte, the one having the same composition as that used in the oxygen gas generation test during charging was prepared and used.
The following charge / discharge cycle test was performed on each of the obtained non-aqueous electrolyte power storage elements in a glove box having an argon atmosphere in an environment of 25 ° C. For the charging current and the discharging current, a current density of 50 mA / g per mass of the positive electrode active material contained in the positive electrode was adopted. The charge / discharge test started from charging, and charging was premised on constant current constant voltage (CCCV) charging with a charging upper limit voltage of 3.4 V. However, the charge termination condition is when the amount of charge electricity per mass of the positive electrode active material reaches 500 mAh / g during the constant current (CC) mode, or when 10 hours have passed after the transition to the constant voltage (CV) mode. did. The discharge was a constant current (CC) discharge, and the discharge termination condition was the time when the amount of electricity discharged per mass of the positive electrode active material reached 500 mAh / g or the lower limit voltage of the discharge reached 1.5 V. FIG. 5 shows a graph showing the amount of discharge electricity for each charge / discharge cycle in each non-aqueous electrolyte power storage element. Table 3 shows the number of charge / discharge cycles in which the discharge electricity amount of 200 mAh / g or more was maintained in the non-aqueous electrolyte power storage elements of each Example and Comparative Example as “cycle life”.

As shown in Table 3 and FIG. 4, each of the positive electrode active materials of Examples 2-1 to 2-3 containing oxygen as an element A together with cobalt as a first element and silicon as a second element was used. The water electrolyte storage element had a large amount of charging electricity (oxygen gas generation starting point) at the time when the generation of oxygen gas was confirmed, and the generation of oxygen gas was suppressed even when the amount of charging electricity was increased. Further, as shown in Table 3 and FIG. 5, the non-aqueous electrolyte power storage element using each positive electrode active material of Examples 2-1 to 2-3 is charged with a discharge electricity amount of 200 mAh / g or more maintained. It had a large number of discharge cycles and had a sufficient charge / discharge cycle life. Further, as shown in Table 3, depending on the content of nitrogen as an element A, the integrated intensity of the diffraction peak having a diffraction angle 2θ near 44 ° with respect to the integral intensity of the diffraction peak near 33 °. It was confirmed that the ratio and the lattice constant a became large.

The present invention can be applied to electronic devices such as personal computers and communication terminals, non-aqueous electrolyte power storage elements used as power sources for automobiles, and positive electrodes and positive electrode active materials provided therein.

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

Claims

It contains lithium, oxygen, the first element, and element A, and has an inverted fluorite-type crystal structure.
The first element is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper.
A positive electrode active material in which the element A is at least one selected from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine.
The positive electrode active material according to claim 1, wherein the molar ratio of the content of the element A to the oxygen content is more than 0.00 and 0.2 or less.
The positive electrode active material according to claim 1 or 2, wherein the first element is cobalt.
It contains lithium, oxygen, first element, second element and element A, and has an inverted fluorite-type crystal structure.
The first element is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper.
The second element is at least one selected from the group consisting of Group 13 elements, Group 14 elements, phosphorus, antimony, bismuth and tellurium.
A positive electrode active material in which the element A is nitrogen.
Positive electrode active material represented by the following formula 1.
Li a M 1 b M 2 c ON d ... 1
In formula 1, M 1 is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni and Cu. M 2 is at least one selected from the group consisting of Group 13 elements, Group 14 elements, P, Sb, Bi and Te.
a, b, c and d are 1.0 <a <2.0, 0.000 <b <0.5, 0.000 <c <0.2, 0.000 <d <0.2, respectively. Meet.
In the X-ray diffraction diagram using CuKα rays, the ratio of the integrated intensity of the diffraction peak having a diffraction angle 2θ of 44 ° to the integrated intensity of the diffraction peak having a diffraction angle 2θ of 33 ° is more than 0.00 and 2 or less. Item 4 or the positive electrode active material according to claim 5.
The positive electrode active material according to any one of claims 1 to 6, which satisfies the following formula 2.
1.000 <a 1 / a 2 <1.005 ・・・ 2
In Equation 2, a 1 is the lattice constant of the positive electrode active material. a2 is a lattice constant of a compound having a composition in which all the elements A in the positive electrode active material are replaced with oxygen and having an inverted fluorite-type crystal structure.
The positive electrode active material according to any one of claims 1 to 7, wherein in the X-ray diffraction diagram using CuKα rays, the half width of the diffraction peak near the diffraction angle 2θ of 33 ° is 0.3 ° or more.
A positive electrode for a non-aqueous electrolyte power storage element containing the positive electrode active material according to any one of claims 1 to 8.
A non-aqueous electrolyte power storage element provided with the positive electrode according to claim 9.
A power storage device including a plurality of non-aqueous electrolyte power storage elements and one or more of the non-water electrolyte power storage elements according to claim 10.
It comprises treating materials containing lithium, oxygen, the first element and element A by the mechanochemical method.
The first element is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper, and the element A is from the group consisting of nitrogen, sulfur, selenium, fluorine, chlorine, bromine and iodine. A method for producing a positive electrode active material, which is at least one selected.
It comprises treating materials containing lithium, oxygen, first element, second element and element A by the mechanochemical method.
The first element is at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel and copper.
The second element is at least one selected from the group consisting of Group 13 elements, Group 14 elements, phosphorus, antimony, bismuth and tellurium.
A method for producing a positive electrode active material in which the element A is nitrogen.
A positive electrode is produced using the positive electrode active material according to any one of claims 1 to 9 or the positive electrode active material obtained by the method for producing a positive electrode active material according to claim 12 or 13. A method for manufacturing a positive electrode for a non-aqueous electrolyte power storage element.
A method for manufacturing a non-aqueous electrolyte power storage element according to claim 14, wherein the method for manufacturing a positive electrode is provided.