JP2018056025A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which is superior in high output property and high-temperature resistance.SOLUTION: A lithium ion secondary battery (1) comprises: a positive electrode (5) including a positive electrode active material consisting of a transition metal oxide capable of occluding and releasing a lithium ion; a carbon material-containing negative electrode (6); a separator (7); and a nonaqueous electrolyte containing lithium ions. The carbon material-containing negative electrode (6) forms an interlayer compound with lithium and one or more kinds of alkali metal and/or alkali earth metal, which are larger than lithium in atomic radius.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium ion secondary battery or an alkali metal ion secondary battery.

In recent years, from the viewpoint of the conservation of the global environment and the effective use of energy aimed at saving resources, wind power generation smoothing system or midnight power storage system, home-use distributed storage system based on solar power generation technology, storage for electric vehicles The system is drawing attention.
The first requirement for batteries used in these power storage systems is high energy density. As a promising candidate for a high energy density battery capable of meeting such demands, development of a lithium ion secondary battery has been vigorously advanced.
The second requirement is high output characteristics. For example, in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle), high output discharge characteristics in the power storage system are required during acceleration. Yes.
The third requirement is that deterioration due to storage or use is small. For example, in a hybrid electric vehicle, the power storage system is placed in a high temperature environment due to operation of the internal combustion engine or the like. In a lithium ion secondary battery, an electrode and / or an electrolytic solution deteriorate at a high temperature, thereby causing characteristic deterioration. Therefore, suppression of deterioration of the lithium ion secondary battery at a high temperature can be said to be a big problem.

Research on the suppression of deterioration of lithium ion secondary batteries has been conducted for a long time, and generally a method of adding an additive to the electrolyte that can form a good solid electrolyte on the negative electrode by reductive decomposition is adopted. ing. For example, in Patent Documents 1 and 2, an attempt is made to prevent decomposition of the electrolytic solution that occurs in a high temperature environment by adding an additive typified by vinylene carbonate to the electrolytic solution. In Patent Document 3, 3-propane sultone is added to the electrolytic solution and reacted on the negative electrode surface to form a high-quality solid electrolyte, suppressing gas generation during high-temperature storage, and improving cycle characteristics. It is described.
However, in the methods described in Patent Documents 1 to 3, there is room for further improvement in terms of gas generation due to electrolytic solution decomposition on the surface of the positive electrode and a decrease in output due to formation of a solid electrolyte on the electrode.

JP 7-328278 A JP 2001-167767 A JP 2012-174437 A

  In view of the above situation, the problem to be solved by the present invention is to provide a lithium ion secondary battery excellent in high output characteristics and high temperature durability.

As a result of intensive studies to solve the above-mentioned problems and repeated experiments, the present inventors have found that the carbon material-containing negative electrode is lithium and one or more alkali metals and alkaline earth metals having a larger atomic radius than lithium. And the formation of an intercalation compound found that the output characteristics were improved and that the decomposition of the electrolyte solution on the surface of the positive electrode could be suppressed to ensure high temperature durability, thereby completing the present invention.
That is, the present invention is as follows:
[1]
A positive electrode having a positive electrode active material layer including a positive electrode active material made of a transition metal oxide capable of occluding and releasing lithium ions;
Carbon material-containing negative electrode;
A separator; and a non-aqueous electrolyte containing the lithium ion;
A lithium ion secondary battery comprising
The carbon material-containing negative electrode forms an interlayer compound with lithium and one or more alkali metals and / or alkaline earth metals having a larger atomic radius than lithium,
The lithium ion secondary battery.
[2]
The carbon material-containing negative electrode is measured by inductively coupled plasma (ICP) emission spectroscopic analysis, and the one or more types of alkali metals and / or alkaline earth metals are detected in total of 100 ppm or more, according to [1]. Lithium ion secondary battery.
[3]
The positive electrode active material layer has the following formulas (1) to (3):
^{M 1 X 1 -OR 1 O-} X 2 M 2 ······ (1)
{In the formula (1), are each ^{M 1} and ^{M 2} independently is an element selected Li, Na, K, Rb, Cs, Mg, Ca, Sr, or from Ba, ^{R 1} is 1 to the number of carbon atoms 4 alkylene group or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
^{M 1 X 1 -OR 1 O-} X 2 R 2 ······ (2)
{In Formula (2), M ¹ is an element selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, or Ba, and R ¹ is an alkylene group having 1 to 4 carbon atoms, or A halogenated alkylene group having 1 to 4 carbon atoms, R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, A mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
^{R 2 X 1 -OR 1 O-} X 2 R 3 ······ (3)
{In Formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 to 10 carbon atoms. An alkyl group, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or An aryl group, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
At least one compound selected from the group consisting of 3.8 × 10 ⁻⁹ mol / g to 3.0 × 10 ⁻² mol / g per unit mass of the positive electrode active material layer [1] Or the lithium ion secondary battery as described in [2].
[4]
In the X-ray diffraction (XRD) measurement (CuKα ray) of the carbon material-containing negative electrode, the lithium ion ion according to any one of [1] to [3], which has a peak of (004) at 2θ ≦ 23 °. Next battery.
[5]
A positive electrode having a positive electrode active material layer containing a transition metal oxide capable of inserting and extracting lithium ions and one or more alkali metal compounds and / or alkaline earth metal compounds;
Carbon material-containing negative electrode;
A separator; and a non-aqueous electrolyte containing the lithium ion;
An alkali metal ion secondary battery containing
The carbon material-containing negative electrode forms an interlayer compound with lithium and one or more alkali metals and / or alkaline earth metals having a larger atomic radius than lithium,
The alkali metal ion secondary battery.
[6]
The alkali metal ion secondary battery according to [5], wherein the alkali metal compound and / or alkaline earth metal compound is at least one selected from the group consisting of carbonates, hydroxides, and oxides.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion secondary battery excellent in the high output characteristic and high temperature durability can be provided.

It is a top view which shows roughly an example of the lithium ion secondary battery which concerns on this embodiment. It is the sectional view on the AA line of the lithium ion secondary battery shown by FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention.
In general, a lithium ion secondary battery mainly includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an outer package.

<1. Overall configuration of lithium ion secondary battery>
As a lithium ion secondary battery of this embodiment, for example,
A lithium ion comprising: a positive electrode containing a positive electrode material capable of inserting and extracting lithium ions as a positive electrode active material; and a negative electrode comprising a carbon material capable of inserting and extracting lithium ions as a negative electrode active material. A secondary battery is mentioned.

Specifically, the lithium ion secondary battery of the present embodiment may be the lithium ion secondary battery illustrated in FIGS. 1 and 2. Here, FIG. 1 is a plan view schematically showing a lithium ion secondary battery, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
The lithium ion secondary battery 1 includes a laminated electrode body formed by laminating a positive electrode 5 and a negative electrode 6 with a separator 7 in a battery exterior 2 constituted by two aluminum laminate films (8), and non-aqueous electrolysis. Liquid (not shown). The battery exterior 2 is sealed by heat-sealing the upper and lower aluminum laminate films (8) at the outer periphery thereof. The laminate in which the positive electrode 5, the separator 7, and the negative electrode 6 are sequentially laminated is impregnated with a nonaqueous electrolytic solution. However, in FIG. 2, each layer constituting the battery exterior 2 and each layer of the positive electrode 5 and the negative electrode 6 are not shown separately in order to prevent the drawing from becoming complicated.

  The aluminum laminate film (8) constituting the battery exterior 2 is preferably one in which both surfaces of an aluminum foil are coated with a polyolefin resin.

  The positive electrode 5 is connected to the positive electrode external terminal 3 through the lead body in the battery 1. Although not shown, the negative electrode 6 is also connected to the negative electrode external terminal 4 through the lead body in the battery 1. Each of the positive electrode external terminal 3 and the negative electrode external terminal 4 is drawn out to the outside of the battery exterior 2 so that it can be connected to an external device or the like, and the resin part fused to them is a battery exterior. It is heat-sealed together with one side of 2.

  In the lithium ion secondary battery 1 shown in FIGS. 1 and 2, the positive electrode 5 and the positive electrode 6 each have one laminated electrode body, but the number of the positive electrodes 5 and the negative electrodes 6 can be increased depending on the capacity design. It can be increased as appropriate. In the case of a laminated electrode body having a plurality of positive electrodes 5 and negative electrodes 6, tabs having the same polarity may be joined by welding or the like, and then joined to one lead body by welding or the like and taken out of the battery. Examples of the same type of tab include an aspect constituted by an exposed portion of the current collector, an aspect constituted by welding a metal piece to the exposed portion of the current collector, and the like.

The positive electrode 5 includes a positive electrode active material layer made from a positive electrode mixture and a positive electrode current collector. The negative electrode 6 includes a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The positive electrode 5 and the negative electrode 6 are disposed so that the positive electrode active material layer and the negative electrode active material layer face each other with the separator 7 interposed therebetween.
Hereinafter, the positive electrode and the negative electrode are also abbreviated as “electrode”, the positive electrode active material layer and the negative electrode active material layer are collectively referred to as “electrode active material layer”, and the positive electrode mixture and the negative electrode mixture are also abbreviated as “electrode mixture”.
As each of these members, a material provided in a conventional lithium ion secondary battery can be used as long as each requirement in the present embodiment is satisfied, and a material described later may be used. Hereinafter, each member of the lithium ion secondary battery will be described in detail.

<2. Positive electrode>
The positive electrode 5 shown in FIG. 2 includes a positive electrode active material layer made from a positive electrode mixture and a positive electrode current collector. It is preferable that the positive electrode 5 contains one or more types of alkali metal compounds and / or alkaline earth metal compounds as a positive electrode precursor before assembling the power storage element. As will be described later, in the present embodiment, in the step of assembling the electricity storage element, it is preferable to pre-dope the negative electrode with one or more kinds of alkali metal and / or alkaline earth metal. As a pre-doping method in the present embodiment, a storage element was assembled using a positive electrode precursor containing one or more alkali metal compounds and / or alkaline earth metal compounds, a negative electrode, a separator, and a non-aqueous electrolyte solution. Later, it is preferable to apply a voltage between the positive electrode precursor and the negative electrode. The alkali metal and / or alkaline earth metal compound is preferably contained in the positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor.

The positive electrode active material layer contains a positive electrode active material and optionally further contains a conductive additive and a binder.
In the present specification, the positive electrode before the lithium doping step is defined as “positive electrode precursor”, and the positive electrode after the lithium doping step is defined as “positive electrode”.

The positive electrode active material layer preferably contains a material capable of inserting and extracting lithium ions as the positive electrode active material. It is preferable that a positive electrode active material layer contains a conductive support agent and a binder as needed with a positive electrode active material.
The positive electrode active material layer of the positive electrode precursor preferably contains one or more alkali metal compounds and alkaline earth metal compounds having an atomic radius larger than that of lithium. In the present specification, an alkali metal compound and an alkaline earth metal compound are an alkali metal-containing compound and an alkaline earth deposited in a positive electrode active material layer using a decomposition reaction of an active material and a positive electrode precursor described later. This refers to alkali metal compounds and alkaline earth metal compounds other than metal compounds.

Examples of the positive electrode active material include the following general formulas (3a) and (3b):
Li _x MO ₂ (3a)
Li _y M ₂ O ₄ (3b)
{In the formula, M represents one or more metal elements including at least one transition metal element, x represents a number from 0 to 1.1, and y represents a number from 0 to 2. }, A lithium-containing compound represented by each of the above and other lithium-containing compounds.

Examples of the lithium-containing compound represented by each of the general formulas (3a) and (3b) include lithium cobalt oxides typified by LiCoO ₂ ; LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O ₄ . Lithium manganese oxide typified; Lithium nickel oxide typified by LiNiO ₂ ; Li _z MO ₂ (wherein M contains at least one transition metal element selected from Ni, Mn, and Co, and 2 or more metal elements selected from the group consisting of Ni, Mn, Co, Al, and Mg, and z represents a number greater than 0.9 and less than 1.2. Thing etc. are mentioned.

The lithium-containing compound other than the lithium-containing compound represented by each of the general formulas (3a) and (3b) is not particularly limited as long as it contains lithium. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, a metal chalcogenide containing lithium, a metal phosphate compound containing lithium and a transition metal element, and lithium and a transition metal element. Silicic acid metal compounds (for example, Li _t M _u SiO ₄ , where M is as defined in the general formula (3a), t is a number from 0 to 1, and u is a number from 0 to 2. )).
From the viewpoint of obtaining a higher voltage, as the lithium-containing compound, in particular,
With lithium,
Selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), vanadium (V), and titanium (Ti) At least one transition metal element,
The composite oxide containing and a metal phosphate compound are preferable.

More specifically, the lithium-containing compound is more preferably a composite oxide containing lithium and a transition metal element or a metal chalcogenide having lithium and a transition metal element, and a metal phosphate compound containing lithium, for example, The following general formulas (4a) and (4b):
^{_{Li v M I D 2 (4a}} )
Li _w M ^II PO ₄ (4b)
{Wherein D represents oxygen or a chalcogen element, M ^I and M ^II each represent one or more transition metal elements, and the values of v and w differ depending on the charge / discharge state of the battery, and v is 0.05 Represents a number of ˜1.10, and w represents a number of 0.05 to 1.10. }, Compounds represented by each of the above.

  The lithium-containing compound represented by the above general formula (4a) has a layered structure, and the compound represented by the above general formula (4b) has an olivine structure. These lithium-containing compounds are obtained by substituting a part of the transition metal element with Al, Mg, or other transition metal elements for the purpose of stabilizing the structure, and include these metal elements in the grain boundaries. It is also possible that the oxygen atom is partially substituted with a fluorine atom or the like, or at least a part of the surface of the positive electrode active material is coated with another positive electrode active material.

As the positive electrode active material in the present embodiment, only the lithium-containing compound as described above may be used, or other positive electrode active material may be used in combination with the lithium-containing compound.
Examples of other positive electrode active materials include metal oxides or metal chalcogenides having a tunnel structure and a layered structure; sulfur (S); a conductive polymer.
Examples of the metal oxide or metal chalcogenide having a tunnel structure and a layered structure include MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ , and NbSe _2. And oxides, sulfides, selenides, and the like of metals other than lithium.
Examples of the conductive polymer include conductive polymers represented by polyaniline, polythiophene, polyacetylene, and polypyrrole.
The other positive electrode active materials described above can be used singly or in combination of two or more. Since lithium ions can be occluded and released reversibly and at a high energy density, the positive electrode active material layer contains at least one transition metal element selected from Ni, Mn, and Co. It is preferable to contain.
When a lithium-containing compound and another positive electrode active material are used in combination as the positive electrode active material, the use ratio of both is preferably 80% by mass or more, and 85% by mass as the use ratio of the lithium-containing compound to the entire positive electrode active material. % Or more is more preferable.

  Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 10 parts by mass or less, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber. It is preferable that the content rate of a binder is 6 mass parts or less with respect to 100 mass parts of positive electrode active materials, More preferably, it is 0.5-4 mass parts.

  The positive electrode active material layer is formed by applying a positive electrode mixture-containing slurry, in which a positive electrode mixture obtained by mixing a positive electrode active material and, if necessary, a conductive additive and a binder in a solvent, is applied to a positive electrode current collector and dried (solvent removal) And is formed by pressing as necessary. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. Examples of the solvent include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like.

  The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode current collector may have a surface coated with a carbon coat or may be processed into a mesh shape. The thickness of the positive electrode current collector is preferably 5 to 40 μm, more preferably 7 to 35 μm, and still more preferably 9 to 30 μm.

As the alkali metal compound and alkaline earth metal compound in the present embodiment, one or more selected from carbonates, oxides, and hydroxides capable of adsorbing fluorine ions in the electrolytic solution are preferable. Used for. Among these, carbonates are preferably used from the viewpoint that they can be handled in air and have low hygroscopicity.
The alkali metal compound and the alkaline earth metal compound are preferably in the form of particles. The average particle diameter of the particulate alkali metal compound and alkaline earth metal compound is preferably 0.1 μm or more and 100 μm or less. The upper limit of the average particle diameter of the alkali metal compound and the alkaline earth metal compound is more preferably 50 μm or less, and still more preferably 10 μm or less.
If the average particle size of the alkali metal compound and the alkaline earth metal compound is 0.1 μm or more, the volume of pores remaining after the oxidation reaction of the alkali metal compound and the alkaline earth metal compound in the positive electrode holds the electrolytic solution. Therefore, the high load charge / discharge characteristics are improved.
If the average particle size of the alkali metal compound and alkaline earth metal compound is 100 μm or less, the surface area of the alkali metal compound and alkaline earth metal compound will not be excessively reduced. The rate of reaction can be ensured. If the average particle diameter of the alkali metal compound and the alkaline earth metal compound is 50 μm or less or 10 μm or less, the surface area of the alkali metal compound and the alkaline earth metal compound is increased, and the oxidation rate can be further improved.
Various methods can be used for forming fine particles of the alkali metal compound and the alkaline earth metal compound. For example, a pulverizer such as a ball mill, a bead mill, a ring mill, a jet mill, or a rod view can be used.

  The content ratio of the alkali metal compound and the alkaline earth metal compound in the positive electrode precursor is preferably 1% by mass or more and 60% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor. More preferably, it is 50 mass% or less. By setting the content ratio in this range, it is possible to provide a lithium ion secondary battery that can exhibit a suitable function as a dopant source for the negative electrode and is excellent in charge and discharge efficiency, and thus is preferable. Further, it is more preferable because the positive electrode precursor contains one or more alkali metal compounds and / or alkaline earth metal compounds having an atomic radius larger than that of lithium, so that the output of the lithium ion secondary battery can be increased. .

From the viewpoint of high temperature durability of the lithium ion secondary battery, the positive electrode active material layer has the following formulas (1) to (3) separately from the positive electrode active material, alkali metal compound, and alkaline earth metal compound described above. :
^{M 1 X 1 -OR 1 O-} X 2 M 2 ······ (1)
{In the formula (1), are each ^{M 1} and ^{M 2} independently is an element selected Li, Na, K, Rb, Cs, Mg, Ca, Sr, or from Ba, ^{R 1} is 1 to the number of carbon atoms 4 alkylene group or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
^{M 1 X 1 -OR 1 O-} X 2 R 2 ······ (2)
{In Formula (2), M ¹ is an element selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, or Ba, and R ¹ is an alkylene group having 1 to 4 carbon atoms, or A halogenated alkylene group having 1 to 4 carbon atoms, R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, A mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
^{R 2 X 1 -OR 1 O-} X 2 R 3 ······ (3)
{In Formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 to 10 carbon atoms. An alkyl group, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or An aryl group, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
It is preferable that at least 1 type of compound represented by these is included.
Content of the compound represented by Formula (1)-(3) in a positive electrode active material layer is 3.8 * 10 < ^-9 > mol / g-3.0 * 10 ^<-2 > per unit mass of a positive electrode active material layer. It is preferably mol / g.
The compounds represented by the formulas (1) to (3) are included in the active material layer, for example, by being deposited on the positive electrode active material layer during the pre-doping step of the negative electrode or during charge / discharge of the battery.

<3. Negative electrode>
The negative electrode 6 shown in FIG. 2 includes a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The negative electrode 6 is not particularly limited as long as it functions as a negative electrode of a lithium ion secondary battery, and may be a known one. Generally, a negative electrode contains negative electrode active materials, such as a carbon material mentioned later. In this specification, a negative electrode including a carbon material as a negative electrode active material is referred to as a carbon material-containing negative electrode.

The negative electrode active material layer preferably includes a carbon material that can form an interlayer compound with an alkali metal and / or an alkaline earth metal. In this specification, an intercalation compound refers to a compound in which an alkali metal and / or an alkaline earth metal is inserted between layers of a carbon hexagonal network. It is preferable that a negative electrode active material layer contains a conductive support agent and a binder as needed with a negative electrode active material.
In the negative electrode active material layer according to the present embodiment, as long as there is an intercalation compound derived from a carbon material, lithium, and one or more types of alkali metal and / or alkaline earth metal having an atomic radius larger than that of lithium, The confirmation method of an interlayer compound shall not be ask | required. For example, in the X-ray diffraction (XRD) measurement of the carbon material-containing negative electrode using CuKα rays, the fact that there is a (004) peak at 2θ ≦ 23 ° indirectly confirms the intercalation compound. XRD measurement of a carbon material-containing negative electrode using CuKα rays is performed by the method described in the following examples.

Examples of the negative electrode active material include amorphous carbon (hard carbon), graphite represented by artificial graphite or natural graphite, pyrolytic carbon, coke, glassy carbon, a fired body of an organic polymer compound, mesocarbon microbeads, carbon Examples thereof include carbon materials represented by fibers, activated carbon, carbon colloid, and carbon black.
A negative electrode active material is used individually by 1 type or in combination of 2 or more types.

In addition to lithium ions, the negative electrode active material is preferably doped with one or more alkali metals and / or alkaline earth metals having a larger atomic radius than lithium. In the present specification, the one or more alkali metals and alkaline earth metals doped in the negative electrode active material mainly include three forms.
The first form is one or more alkali metals and alkaline earth metals that are previously occluded in the negative electrode active material as a design value before producing a lithium ion secondary battery.
The second form is one or more alkali metals and alkaline earth metals occluded in the negative electrode active material when a lithium ion secondary battery is manufactured and shipped.
As 3rd form, it is 1 or more types of alkali metal and alkaline-earth metal occluded by the negative electrode active material after using a lithium ion secondary battery as a device.
By doping the negative electrode active material with one or more alkali metals and alkaline earth metals having an atomic radius larger than that of lithium, the operating voltage and output characteristics of the obtained lithium ion secondary battery can be improved. It becomes possible.

  Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 20 parts by mass or less, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 10 parts by mass or less, more preferably 0.5 to 6 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  The negative electrode active material layer is prepared by applying a negative electrode mixture-containing slurry in which a negative electrode mixture obtained by mixing a negative electrode active material and, if necessary, a conductive additive and a binder in a solvent is applied to a negative electrode current collector and drying (solvent removal) And is formed by pressing as necessary. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. Examples of the solvent include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like.

  The negative electrode current collector is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode current collector may have a carbon coating on the surface or may be processed into a mesh shape. The thickness of the negative electrode current collector is preferably 5 to 40 μm, more preferably 6 to 35 μm, and still more preferably 7 to 30 μm.

The doping amount of one or more alkali metals and / or alkaline earth metals having a larger atomic radius than lithium and lithium per unit mass of the carbon material-containing negative electrode is 200 mAh / g to 2,000 mAh / g, preferably 250 mAh / g to 1,800 mAh / g, more preferably 300 mAh / g to 1,700 mAh / g.
When the doping amount of lithium and one or more alkali metals and / or alkaline earth metals having an atomic radius larger than that of lithium is 200 mAh / g or more, lithium and one or more alkali metals and alkaline earth in the carbon material-containing negative electrode An irreversible site that cannot be desorbed once it is inserted is well doped, and the carbon material-containing negative electrode with respect to the amount of desired lithium and one or more alkali metals and / or alkaline earth metals can be reduced. Therefore, the negative electrode film thickness can be reduced, and a high energy density can be obtained. As the doping amount of lithium and one or more alkali metals and alkaline earth metals increases, the irreversible capacity of the negative electrode is consumed, and the input / output characteristics, energy density, and high temperature durability are improved.
On the other hand, when the doping amount of one or more alkali metals and alkaline earth metals having an atomic radius larger than that of lithium and lithium is 2,000 mAh / g or less, side effects such as precipitation of alkali metals and alkali metals occur. There is no fear.

  From the viewpoint of achieving both high output characteristics and high temperature durability of a lithium ion secondary battery, when the carbon material-containing negative electrode is measured by inductively coupled plasma (ICP) emission spectroscopic analysis, one or more alkali metals and / or 1 It is preferable that 100 or more ppm of alkaline earth metals are detected in total. ICP emission spectroscopic analysis is performed by the method described in the following examples.

<4. Production of positive electrode precursor and negative electrode>
Each of the positive electrode precursor and the negative electrode has a positive electrode active material layer on one side or both sides of the positive electrode current collector, and a negative electrode active material layer on one side or both sides of the negative electrode current collector. Typically, the positive electrode active material layer is fixed on one surface or both surfaces of the positive electrode current collector, and the negative electrode active material layer is fixed on one surface or both surfaces of the negative electrode current collector.
The positive electrode precursor and the negative electrode can be manufactured by an electrode manufacturing technique in a known lithium ion secondary battery, electric double layer capacitor, or the like. For example, various materials including a positive electrode active material or a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare slurry-like positive electrode coating solution and negative electrode coating solution, respectively. By coating these positive electrode coating liquid and negative electrode coating liquid on one side or both sides of the positive electrode current collector and the negative electrode current collector, respectively, a coating film is formed, and this is dried, whereby the positive electrode A precursor and a negative electrode can be obtained. You may press the obtained positive electrode precursor and / or negative electrode, and may adjust the film thickness, bulk density, etc. of a positive electrode active material layer and / or a negative electrode active material layer. Alternatively, various materials including a positive electrode active material or a negative electrode active material are mixed by a dry method without using a solvent, and the resulting mixture is press-molded, and then a positive electrode current collector or a negative electrode current collector using a conductive adhesive. A method of attaching to an electric body is also possible.

  The positive electrode coating liquid and the negative electrode coating liquid are prepared by dry blending a part or all of the positive electrode active material or various material powders containing the negative electrode active material, and then water or an organic solvent and / or a binder or A liquid or slurry substance in which a dispersion stabilizer is dissolved or dispersed may be additionally prepared. Also, a coating liquid is prepared by adding various material powders containing a positive electrode active material or a negative electrode active material to a liquid or slurry substance in which a binder or dispersion stabilizer is dissolved or dispersed in water or an organic solvent. May be.

  As a method of dry blending part or all of the various material powders including the positive electrode active material, for example, using a ball mill, the positive electrode active material and the alkali metal compound and / or alkaline earth metal compound, and if necessary, conductive A conductive filler may be premixed and premixing may be performed in which a conductive material is coated on an alkali metal compound and / or an alkaline earth metal compound having low conductivity. This makes it easier for the alkali metal compound and / or alkaline earth metal compound to decompose in the positive electrode precursor in the doping step described later. When water is used as the solvent for the positive electrode coating solution, the coating solution may become alkaline by adding an alkali metal compound and / or an alkaline earth metal compound. May be added.

The dissolving or dispersing method is not particularly limited, and preferably a homodisper or a multiaxial dispersing machine, a planetary mixer, a thin film swirl type high speed mixer, or the like can be used. In order to obtain a coating liquid in a good dispersion state, it is preferable to disperse at a peripheral speed of 1 m / s to 50 m / s. A peripheral speed of 1 m / s or more is preferable because various materials can be dissolved or dispersed satisfactorily. A peripheral speed of 50 m / s or less is preferable because various materials are not easily broken by heat or shear force due to dispersion, and reaggregation is reduced.
Regarding the degree of dispersion of the coating liquid, the particle size measured with a particle gauge is preferably 0.1 μm or more and 100 μm or less. As the upper limit of the degree of dispersion, the particle size is more preferably 80 μm or less, and further preferably the particle size is 50 μm or less. A particle size of 0.1 μm or more means that various material powders including the positive electrode active material are not excessively crushed during the preparation of the coating liquid. In addition, when the particle size is 100 μm or less, the coating can be stably performed with less clogging or streaking of the coating film when the coating liquid is discharged.

The viscosity (ηb) of the coating solution is preferably 1,000 mPa · s or more and 20,000 mPa · s or less, more preferably 1,500 mPa · s or more and 10,000 mPa · s or less, and further preferably 1,700 mPa · s or more. 5,000 mPa · s or less. When the viscosity (ηb) of the coating liquid is 1,000 mPa · s or more, dripping during coating film formation is suppressed, and the coating film width and thickness can be controlled well. If the viscosity (ηb) of the coating liquid is 20,000 mPa · s or less, the coating liquid can be stably applied with little pressure loss in the flow path of the coating liquid when a coating machine is used, and the desired coating thickness The following can be controlled.
The TI value (thixotropic index value) of the coating solution is preferably 1.1 or more, more preferably 1.2 or more, and still more preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and thickness can be favorably controlled.

  The method for forming the coating film is not particularly limited, but a coating machine such as a die coater or a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by single layer coating or may be formed by multilayer coating. In the case of multilayer coating of the positive electrode precursor, the coating solution composition may be adjusted so that the lithium compound content in each layer of the coating film is different. The coating speed is preferably 0.1 m / min to 100 m / min, more preferably 0.5 m / min to 70 m / min, and further preferably 1 m / min to 50 m / min. If the coating speed is 0.1 m / min or more, the coating can be performed stably, and if it is 100 m / min or less, sufficient coating accuracy can be secured.

  The method for drying the coating film is not particularly limited, but a drying method such as hot air drying or infrared (IR) drying can be preferably used. The coating film may be dried at a single temperature or may be dried by changing the temperature in multiple stages. Moreover, you may dry combining several drying methods. The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower, and further preferably 50 ° C. or higher and 160 ° C. or lower. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. If the drying temperature is 200 ° C. or less, the coating film cracks due to rapid volatilization of the solvent, the binder is unevenly distributed due to migration, the positive electrode current collector or the negative electrode current collector is oxidized, or the positive electrode active material layer or the negative electrode active Oxidation of the material layer can be suppressed.

The method for pressing the positive electrode precursor and the negative electrode is not particularly limited, but a press such as a hydraulic press or a vacuum press can be preferably used. The film thickness, bulk density, and electrode strength of the positive electrode active material layer and the negative electrode active material layer can be adjusted by the press pressure, the gap, and the surface temperature of the press part described later.
The pressing pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and further preferably 2 kN / cm or more and 7 kN / cm or less. If the pressing pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. When the pressing pressure is 20 kN / cm or less, the positive electrode precursor and the negative electrode are unlikely to bend or wrinkle, and can be easily adjusted to a desired film thickness or bulk density.
The gap between the press rolls can be set to an arbitrary value according to the film thickness after drying so as to have a desired film thickness and bulk density.
The press speed can be set to any speed so that deflection or wrinkles are reduced.
The surface temperature of the press part may be room temperature, or the surface of the press part may be heated if necessary. The lower limit of the surface temperature of the press part when heating is preferably the melting point of the binder used minus 60 ° C. or more, more preferably the melting point of the binder minus 45 ° C. or more, and more preferably the melting point of the binder minus 30. It is above ℃. The upper limit of the surface temperature of the press portion when heating is preferably the melting point of the binder used plus 50 ° C. or less, more preferably the melting point of the binder plus 30 ° C. or less, and more preferably the melting point of the binder plus 20 It is below ℃. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, it is preferably pressed at 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, and further preferably 120 ° C. or higher and 170 ° C. or lower. Heat the surface of the part. When a styrene-butadiene copolymer (melting point 100 ° C.) is used as the binder, it is preferably pressed at 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower, and further preferably 70 ° C. or higher and 120 ° C. or lower. Warm the surface of the part.
The melting point of the binder can be determined at the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter “DSC7” manufactured by PerkinElmer Co., Ltd., 10 mg of sample resin is set in a measurement cell, and the temperature is increased from 30 ° C. to 250 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen gas atmosphere. The temperature is raised, and the endothermic peak temperature in the temperature raising process becomes the melting point.
You may press several times, changing conditions of press pressure, a crevice, speed, and surface temperature of a press part.

  The thickness of the positive electrode active material layer is preferably 20 μm or more and 200 μm or less per side of the positive electrode current collector. The thickness of the positive electrode active material layer is more preferably 25 μm or more and 150 μm or less, more preferably 30 μm or more and 100 μm or less per side. If the thickness of the positive electrode active material layer is 20 μm or more, sufficient charge / discharge capacity can be exhibited. If the thickness of the positive electrode active material layer is 200 μm or less, the ion diffusion resistance in the electrode can be kept low. Therefore, if the thickness of the positive electrode current collector layer is 20 μm or more and 200 μm or less, sufficient output characteristics can be obtained, the cell volume can be reduced, and therefore the energy density can be increased. The thickness of the positive electrode active material layer in the case where the positive electrode current collector has through-holes or irregularities is the thickness of the positive electrode active material layer per side in the portion of the positive electrode current collector that does not have through-holes or irregularities. The average value of

  The thickness of the negative electrode active material layer is preferably 5 μm or more and 150 μm or less per side of the negative electrode current collector. The lower limit of the thickness of the negative electrode active material layer is more preferably 7 μm or more, and further preferably 10 μm or more. The upper limit of the thickness of the negative electrode active material layer is more preferably 130 μm or less, and even more preferably 120 μm or less. When the thickness of the negative electrode active material layer is 5 μm or more, streaks or the like hardly occur when the negative electrode active material layer is applied, and the coating property is excellent. When the thickness of the negative electrode active material layer is 150 μm or less, a high energy density can be expressed by reducing the cell volume. Note that the thickness of the negative electrode active material layer in the case where the negative electrode current collector has unevenness means an average value of the thickness of the negative electrode active material layer per one surface in a portion where the negative electrode current collector does not have unevenness.

The bulk density of the negative electrode active material layer is preferably 0.30 g / cm ³ or more and 2.0 g / cm ³ or less, more preferably 0.40 g / cm ³ or more and 1.8 g / cm ³ or less, and further preferably 0.5 g. / Cm ³ or more and 1.7 g / cm ³ or less. When the bulk density of the negative electrode active material layer is 0.30 g / cm ³ or more, sufficient strength can be maintained and sufficient conductivity between the negative electrode active materials can be exhibited. If the bulk density of the negative electrode active material layer is 1.8 g / cm ³ or less, vacancies capable of sufficiently diffusing ions in the negative electrode active material layer can be secured.

<5. Electrolyte>
The electrolytic solution in the present embodiment is a non-aqueous electrolytic solution. That is, the electrolytic solution contains a nonaqueous solvent described later. The non-aqueous electrolyte solution preferably contains 0.5 mol / L or more of alkali metal salt and / or alkaline earth metal salt based on the total amount of the non-aqueous electrolyte solution. That is, the nonaqueous electrolytic solution contains alkali metal ions and / or alkaline earth metal ions as an electrolyte.

It is preferable that lithium ions and one or more alkali metal ions and / or alkaline earth metal ions having an atomic radius larger than that of lithium are contained in the electrolyte solution of the non-aqueous alkali metal storage element. At the time of charge / discharge of the lithium ion secondary battery, an insertion / extraction reaction of lithium ions proceeds between the layers of the carbon material negative electrode. At this time, when one or more kinds of alkali metal ions and / or alkaline earth metal ions having an atomic radius larger than that of lithium are present in the electrolyte, the alkali metal ions and / or alkaline earth metal ions having a large ion radius are By extending the distance between the carbon hexagonal network surfaces of the carbon material-containing negative electrode, lithium ions having a small ion radius can efficiently perform insertion / desorption reaction, and high output characteristics are improved.
From the above viewpoint, the substance amount ratio of lithium ions in the non-aqueous electrolyte is 1% or more and 99% or less, and the substance amount ratio of the second alkali metal ion and alkaline earth metal ion other than lithium ions is 0.01. It is preferable that the material amount ratio of the third and fourth alkali metal ions and alkaline earth metal ions other than lithium ions is 0% or more and 50% or less. More preferably, the material amount ratio of lithium ions in the non-aqueous electrolyte is 10% or more and 99% or less, and the material amount ratio of the second alkali metal ions and alkaline earth metal ions is 0.05% or more and 50%. The substance amount ratio of the third and fourth alkali metal ions and alkaline earth metal ions is 0% or more and 40% or less. More preferably, the material amount ratio of lithium ions in the non-aqueous electrolyte is 15% or more and 99% or less, and the material amount ratio of the second alkali metal ions and alkaline earth metal ions is 0.1% or more and 40%. The ratio of the amount of the third and fourth alkali metal ions is 0% or more and 30% or less.
The alkali metal ions and alkaline earth metal ions having a larger atomic radius than lithium present in the electrolytic solution may be at least one kind, and may contain two or more kinds of alkali metal ions and alkaline earth metal ions. .

  The method for containing an alkali metal ion and / or alkaline earth metal ion having an atomic radius larger than that of lithium in the electrolytic solution is not particularly limited, and one or more alkali metal salts and / or alkaline earth metal salts are electrolyzed. An alkali metal salt that can be dissolved in a liquid, or can be redox-decomposed by containing one or more alkali metal compounds and / or alkaline earth metal salts in a positive electrode or a negative electrode, or dissolved in an electrolyte In addition, an alkaline earth metal salt and an alkali metal compound that is contained in the positive electrode or the negative electrode and undergoes oxidation-reduction decomposition and / or a substance composed of different cations can be used for the alkaline earth metal compound. The method of adding one or more alkali metal compounds and / or alkaline earth metal compounds having an atomic radius larger than that of lithium to the positive electrode precursor and performing oxidation-reduction decomposition can form a good film on the positive electrode. Therefore, it is particularly preferable.

The nonaqueous electrolytic solution in the present embodiment preferably contains an alkali metal salt and / or an alkaline earth metal salt. For example, as alkali metal salts, MN (SO ₂ F) ₂ , MN (SO ₂ CF ₃ ) ₂ , MN (SO ₂ C ₂ F ₅ ) ₂ , MN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₅ ) , MN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₄ H), MC (SO ₂ F) ₃ , MC (SO ₂ CF ₃ ) ₃ , MC (SO ₂ C ₂ F ₅ ) ₃ , MCF ₃ SO ₃ MC ₄ F ₉ SO ₃ , MPF ₆ , MBF _{4 and the} like (wherein M is an alkali metal independently selected from Li, Na, K, Rb, or Cs), M (N (SO ₂ F) ₂ ) ₂ , M (N (SO ₂ CF ₃ ) ₂ ) ₂ , M (N (SO ₂ C ₂ F ₅ ) ₂ ) ₂ , M (N (SO ₂ CF ₃ )) ₂ (SO ₂ C ₂ F ₅ )) ₂ , M (N (SO ₂ CF ₃ ) (SO _{2 C 2 F 4 H)) 2} , M (C (SO 2 F) 3) 2, M (C (SO 2 CF 3) 3) 2, M (C (SO 2 C 2 F 5) 3) 2, M (CF ₃ SO ₃ ) ₂ , M (C ₄ F ₉ SO ₃ ) ₂ , M (PF ₆ ) ₂ , M (BF ₄ ) _{2 and the} like (wherein, M is independently Mg, Ca, Sr, or Ba) Can be used alone, or two or more of them may be used in combination. Since high conductivity can be expressed, MPF _6, M (PF ₆ ) ₂ and / or MN (SO ₂ F) ₂ , M (N (SO ₂ F) ₂ ) ₂ (wherein M is defined above) It is preferred that the

  The alkali metal salt and alkaline earth metal salt concentration in the non-aqueous electrolyte is preferably 0.5 mol / L or more, and more preferably in the range of 0.5 to 2.0 mol / L. When the alkali metal salt concentration is 0.5 mol / L or more, anions are sufficiently present, so that the capacity of the energy storage device can be sufficiently increased. Further, when the alkali metal salt and alkaline earth metal salt concentration is 2.0 mol / L or less, undissolved alkali metal salt and alkaline earth metal salt are precipitated in the non-aqueous electrolyte solution, and the electrolyte solution It is preferable because the viscosity can be prevented from becoming too high, the conductivity is not lowered, and the output characteristics are not lowered.

  The nonaqueous electrolytic solution in the present embodiment preferably contains a cyclic carbonate and a chain carbonate as a nonaqueous solvent. It is advantageous that the non-aqueous electrolytic solution contains a cyclic carbonate and a chain carbonate in terms of dissolving a desired concentration of alkali metal salt and alkaline earth metal salt and expressing high alkali metal ion conductivity. . Examples of the cyclic carbonate include alkylene carbonate compounds represented by ethylene carbonate, propylene carbonate, butylene carbonate, and the like. The alkylene carbonate compound is typically unsubstituted. Examples of the chain carbonate include dialkyl carbonate compounds represented by dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. The dialkyl carbonate compound is typically unsubstituted.

  The total content of the cyclic carbonate and the chain carbonate is preferably 50% by mass or more, more preferably 65% by mass or more, preferably 95% by mass or less, more preferably 90% by mass, based on the total amount of the non-aqueous electrolyte solution. % Or less. When the total content is 50% by mass or more, a desired concentration of alkali metal salt and alkaline earth metal salt can be dissolved, and high ionic conductivity can be expressed. If the said total concentration is 95 mass% or less, electrolyte solution can further contain the additive mentioned later.

  The non-aqueous electrolyte solution in the present embodiment may further contain an additive. Although it does not restrict | limit especially as an additive, For example, a sultone compound, cyclic phosphazene, acyclic fluorine-containing ether, a phosphoric acid compound, a fluorine-containing cyclic carbonate, cyclic carbonate, cyclic carboxylic acid ester, cyclic acid anhydride, etc. are individual. In addition, two or more kinds may be mixed and used.

  In the present embodiment, as a saturated cyclic sultone compound, 1,3-propane sultone, from the viewpoint of less adverse effects on resistance and the suppression of gas generation by suppressing decomposition of the non-aqueous electrolyte at high temperature, 2,4-butane sultone, 1,4-butane sultone, 1,3-butane sultone or 2,4-pentane sultone is preferred, and the unsaturated cyclic sultone compound is preferably 1,3-propene sultone or 1,4-butene sultone, Other sultone compounds include methylene bis (benzene sulfonic acid), methylene bis (phenylmethane sulfonic acid), methylene bis (ethane sulfonic acid), methylene bis (2,4,6, trimethylbenzene sulfonic acid), and methylene bis (2-trifluoro). Methylbenzenesulfonic acid) It is preferable to select at least one or more selected from these.

  The total content of sultone compounds in the non-aqueous electrolyte solution of the lithium ion secondary battery in the present embodiment is preferably 0.01% by mass to 10% by mass based on the total amount of the non-aqueous electrolyte solution. If the total content of sultone compounds in the non-aqueous electrolyte solution is 0.01% by mass or more, it is possible to suppress gas generation by suppressing decomposition of the electrolyte solution at a high temperature. On the other hand, if the total content is 10% by mass or less, a decrease in the ionic conductivity of the electrolytic solution can be suppressed, and high input / output characteristics can be maintained. Further, the content of the sultone compound present in the non-aqueous electrolyte of the lithium ion secondary battery is more preferably 0.1% by mass or more and 10% by mass or less from the viewpoint of achieving both high input / output characteristics and durability. More preferably, it is 0.1 mass% or more and 5 mass% or less.

Examples of the cyclic phosphazene include ethoxypentafluorocyclotriphosphazene, diethoxytetrafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and the like, and one or more selected from these are preferable.
The content of cyclic phosphazene in the non-aqueous electrolyte is preferably 0.5% by mass to 20% by mass based on the total amount of the non-aqueous electrolyte. When this value is 0.5% by weight or more, it is possible to suppress gas generation by suppressing decomposition of the electrolytic solution at a high temperature. On the other hand, if this value is 20% by mass or less, a decrease in the ionic conductivity of the electrolytic solution can be suppressed, and high input / output characteristics can be maintained. For the above reasons, the content of cyclic phosphazene is more preferably 2% by mass or more and 15% by mass or less, and further preferably 4% by mass or more and 12% by mass or less.
These cyclic phosphazenes may be used alone or in combination of two or more.

Examples of the acyclic fluorine-containing ether include HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CFHCF _{3 and the} like are mentioned, and among them, HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H is preferable from the viewpoint of electrochemical stability.
The content of the non-cyclic fluorine-containing ether is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the non-cyclic fluorine-containing ether is 0.5% by mass or more, the stability of the non-aqueous electrolyte solution against oxidative decomposition is enhanced, and a lithium ion secondary battery having high durability at high temperatures can be obtained. On the other hand, if the content of the non-cyclic fluorine-containing ether is 15% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. It is possible to develop input / output characteristics.
The acyclic fluorine-containing ether may be used alone or in combination of two or more.

Examples of the phosphoric acid compound include triallyl phosphate, tributyl phosphate, trimethyl phosphate, trimethylsilyl phosphate, and the like. Among them, triallyl phosphate is preferable because a good film can be formed on the positive electrode and the negative electrode.
The content of the phosphoric acid compound is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. When the content of the phosphoric acid compound is 0.05% by mass or more, the stability of the non-aqueous electrolyte solution against oxidative decomposition is increased, and a lithium ion secondary battery having high durability at high temperatures can be obtained. On the other hand, if the phosphoric acid compound is 10% by mass or less, a decrease in the ionic conductivity of the nonaqueous electrolytic solution can be suppressed, and high input / output characteristics can be maintained.

The fluorine-containing cyclic carbonate is preferably selected from fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) from the viewpoint of compatibility with other nonaqueous solvents.
The content of the fluorine-containing cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the nonaqueous electrolytic solution. If the content of the fluorine-containing cyclic carbonate is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolyte solution on the negative electrode, durability at high temperatures can be achieved. A high power storage element can be obtained. On the other hand, if the content of the cyclic carbonate containing a fluorine atom is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. It is possible to develop advanced input / output characteristics.
The cyclic carbonate containing a fluorine atom may be used alone or in combination of two or more.

For the cyclic carbonate, vinylene carbonate is preferred.
The content of the cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the nonaqueous electrolytic solution. If the content of the cyclic carbonate is 0.5% by mass or more, a good-quality film on the negative electrode can be formed, and by suppressing the reductive decomposition of the electrolyte solution on the negative electrode, durability at high temperatures can be achieved. A high power storage element can be obtained. On the other hand, if the content of the cyclic carbonate is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high, so that high input / output characteristics can be obtained. Can be expressed.

Examples of the cyclic carboxylic acid ester include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like, and it is preferable to use one or more selected from these. Of these, gamma-butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of dissociation of alkali metal ions.
The content of the cyclic carboxylic acid ester is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total amount of the nonaqueous electrolytic solution. If the content of the cyclic carboxylic acid ester is 0.5% by mass or more, a high-quality film on the negative electrode can be formed, and by suppressing the reductive decomposition of the electrolyte solution on the negative electrode, durability at high temperatures is achieved. Can be obtained. On the other hand, if the content of the cyclic carboxylic acid ester is 15% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high, so that a high degree of input / output can be achieved. It becomes possible to express characteristics.
In addition, the said cyclic carboxylic acid ester may be used individually, or 2 or more types may be mixed and used for it.

The cyclic acid anhydride is preferably at least one selected from succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride. Among them, it is preferable to select from succinic anhydride and maleic anhydride from the viewpoint that the production cost of the electrolytic solution can be suppressed due to industrial availability and that the electrolytic solution can be easily dissolved in the non-aqueous electrolytic solution.
The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total amount of the nonaqueous electrolytic solution. If the content of the cyclic acid anhydride is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the electrolyte solution on the negative electrode, durability at high temperatures can be achieved. A high power storage element can be obtained. On the other hand, if the content of the cyclic acid anhydride is 15% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte can be kept high. It becomes possible to express characteristics.
In addition, the said cyclic acid anhydride may be used individually, or 2 or more types may be mixed and used for it.

<6. Separator>
The lithium ion secondary battery 1 shown in FIGS. 1 and 2 includes a separator 7 between the positive electrode 5 and the negative electrode 6 from the viewpoint of providing safety such as prevention of short circuit between the positive electrode 5 and the negative electrode 6 and shutdown. The separator 7 may be the same as that provided in a known lithium ion secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator 7 include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable.

  As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is suitably used. Examples of the nonwoven fabric include a porous film made of a heat resistant resin such as glass, ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, and aramid.

  The separator 7 may have a configuration in which one type of microporous membrane is laminated or a plurality of microporous membranes may be laminated, or two or more types of microporous membranes may be laminated. The separator 7 may be configured to be laminated in a single layer or a plurality of layers using a mixed resin material obtained by melting and kneading two or more kinds of resin materials.

<7. Battery exterior>
1 and 2, the battery exterior 2 is composed of two laminate films 8. However, the configuration of the battery exterior of the lithium ion secondary battery in the present embodiment is not particularly limited. For example, the battery can and the laminate film exterior Any battery sheath of the body can be used. As the battery can, for example, a metal can made of steel or aluminum can be used. As the laminate film outer package, for example, a laminate film having a three-layer structure of hot melt resin / metal film / resin can be used.

  Laminate film exterior is in a state where two sheets are stacked with the hot-melt resin side facing inward, or folded so that the hot-melt resin side faces inward, and the end is sealed by heat sealing It can be used as an exterior body. When using the laminate film outer package, as shown in FIGS. 1 and 2, the positive electrode external terminal 3 (or the lead tab connected to the positive electrode terminal and the positive electrode terminal) is connected to the positive electrode current collector, and the negative electrode external is connected to the negative electrode current collector. You may connect the terminal 4 (or the lead tab connected with a negative electrode terminal and a negative electrode terminal). In this case, the laminate film exterior body is sealed with the end portions of the positive external terminal 3 and the negative external terminal 4 (or lead tabs connected to the positive terminal and the negative terminal) pulled out to the exterior body. Also good.

<8. Manufacturing method of battery>
As shown in FIG. 2, the lithium ion secondary battery 1 in the present embodiment includes the above-described non-aqueous electrolyte, the positive electrode 5 having a positive electrode active material layer on one side or both sides of the current collector, one side of the current collector, or A negative electrode 6 having a negative electrode active material layer on both sides, a battery casing 2 and, if necessary, a separator 7 are used to produce the negative electrode active material layer by a known method.
First, the laminated body which consists of the positive electrode 5 and the positive electrode 6, and the separator 7 as needed is formed.
For example:
A mode in which the long positive electrode 5 and the negative electrode 6 are wound in a laminated state in which a long separator is interposed between the positive electrode 5 and the negative electrode 6 to form a laminate having a wound structure;
A mode of forming a laminate having a laminated structure in which a positive electrode sheet and a negative electrode sheet obtained by cutting the positive electrode 5 and the negative electrode 6 into a plurality of sheets having a certain area and shape are alternately laminated via a separator sheet. ;
A mode of forming a laminated body having a laminated structure in which a long separator is folded in a zigzag manner, and a positive electrode sheet and a negative electrode sheet are alternately inserted between the zipped separators;
Etc. are possible.

  Next, the above-described laminate is accommodated in the battery casing 2 (battery case), the electrolytic solution according to the present embodiment is injected into the battery case, and after the injection step is further impregnated, the positive electrode It is desirable to sufficiently immerse the negative electrode and the separator with a non-aqueous electrolyte. In the state in which the electrolyte solution is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, the doping proceeds in a non-uniform manner in an alkali metal and / or alkaline earth metal doping step, which will be described later. The resistance of the secondary battery increases or the high duty cycle durability decreases. The impregnation method is not particularly limited. For example, a lithium ion secondary battery after injection is placed in a decompression chamber with the exterior material opened, and the interior of the chamber is decompressed using a vacuum pump. A method of returning the pressure to atmospheric pressure again can be used. After completion of the impregnation step, the lithium ion secondary battery with the exterior material opened is sealed while being decompressed.

  In the alkali metal and / or alkaline earth metal doping step, by applying a voltage between the positive electrode precursor and the negative electrode to decompose the alkali metal compound and / or alkaline earth metal compound, The alkali metal compound and / or alkaline earth metal compound is decomposed to release alkali metal ions and / or alkaline earth metal ions, and carbon is obtained by reducing the alkali metal ions and / or alkaline earth metal ions at the negative electrode. The material-containing negative electrode is preferably pre-doped with alkali metal and / or alkaline earth metal. With this method, for example, alkali metal and / or alkaline earth metal can be pre-doped on the negative electrode without using metallic sodium or metallic potassium that ignites in air, and a good film can be formed on the positive electrode. This is preferable because it is possible.

In the alkali metal and / or alkaline earth metal doping step, a gas such as CO ₂ is generated with the oxidative decomposition of the alkali metal compound and / or alkaline earth metal compound in the positive electrode precursor. Therefore, in order to apply a voltage, it is preferable to take a means for releasing the generated gas to the outside of the exterior body. As this means, for example, a method of applying a voltage in a state in which a part of the exterior body is opened; a state in which an appropriate gas releasing means such as a gas vent valve or a gas permeable film is previously installed in a part of the exterior body And a method of applying a voltage;
Alternatively, an electrolyte membrane in a gel state is prepared in advance by impregnating a base material made of a polymer material with an electrolytic solution, and a sheet-like positive electrode, a negative electrode, an electrolyte membrane, and, if necessary, a separator After forming the laminated body of a laminated structure using, it can accommodate in a battery exterior and a lithium ion secondary battery can be produced.
The shape of the lithium ion secondary battery in the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminated shape, and the like are suitably employed.

  If the lithium ion secondary battery in this embodiment can function as a battery by the first charge, there is no particular limitation on the method of the first charge. Considering that the lithium ion secondary battery is stabilized by decomposition of a part of the electrolytic solution at the time of the first charge, in order to effectively express this stabilization effect, the first charge is 0.001-1. / 3C is preferable, 0.002 to 0.25C is more preferable, and 0.003 to 0.2C is more preferable. It is also preferable that the initial charging is performed via constant voltage charging in the middle. The constant current for discharging the rated capacity in 1 hour is 1C. SEI (Solid Electrolyte Interface) is formed on the electrode surface by setting the voltage range in which the lithium salt is involved in the electrochemical reaction, thereby suppressing the increase in internal resistance including the positive electrode. In addition, the reaction product is not firmly fixed only to the negative electrode, and a favorable effect is given to members other than the negative electrode (for example, the positive electrode 5, the separator 7, etc.) in an arbitrary manner. Therefore, it is very effective to perform the initial charge in consideration of the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte.

  The lithium ion secondary battery in this embodiment can also be used as a battery pack in which a plurality of lithium ion secondary batteries are connected in series or in parallel. From the viewpoint of managing the charge / discharge state of the battery pack, the operating voltage range per unit is preferably 2 to 5 V, more preferably 2.5 to 5 V, and 2.75 V to 5 V. Particularly preferred.

<9. Alkali metal ion secondary battery>
A positive electrode having a positive electrode active material layer containing a transition metal oxide capable of inserting and extracting lithium ions and one or more alkali metal compounds and / or alkaline earth metal compounds;
Carbon material-containing negative electrode;
A separator; and a non-aqueous electrolyte containing lithium ions;
An alkali metal ion secondary battery (not shown) including is also an embodiment of the present invention.
An alkali metal ion secondary battery which is one embodiment of the present invention can be formed using the battery components and manufacturing methods already described above.
In the alkali metal ion secondary battery which is one embodiment of the present invention, the carbon material included in the negative electrode is described above as lithium and one or more kinds of alkali metal and alkaline earth metal having an atomic radius larger than that of lithium. An intercalation compound is formed.
In one embodiment of the present invention, alkali metal ions other than lithium ions can move from the positive electrode precursor or the positive electrode into the electrolytic solution. Therefore, the non-aqueous energy storage element is formed as an alkali metal ion type rather than a lithium ion type. To drive.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
Production of various constituent members and power storage elements and various evaluations were performed as follows.

(1) Production of positive electrode 86.5 parts by weight of a composite oxide (LiNi _0.5 Mn _0.2 Co _0.3 O ₂ ) of lithium, nickel, manganese and cobalt as a positive electrode active material, and acetylene as a conductive additive Black powder is mixed with 5.0 parts by weight, polyvinylidene fluoride (PVdF) as a binder is mixed with 5.0 parts by weight, and the corresponding alkali metal compound and / or alkaline earth metal compound is mixed with 3.5 parts by weight. Got. Table 1 shows the composition of the corresponding alkali metal compound and / or alkaline earth metal compound. N-methyl-2-pyrrolidone as a solvent was added to the obtained positive electrode mixture and further mixed to prepare a positive electrode mixture-containing slurry. The positive electrode mixture-containing slurry was applied to one surface of an aluminum foil while adjusting the basis weight to about 95.0 g / m ² on an aluminum foil having a thickness of 15 μm serving as a positive electrode current collector. When applying the positive electrode mixture-containing slurry to the aluminum foil, an uncoated region was formed so that a part of the aluminum foil was exposed. Then, the positive electrode which consists of a positive electrode active material layer and a positive electrode collector was obtained by rolling so that the density of a positive electrode active material layer might be 1.90 g / cm < ³ > with a roll press.
Next, this positive electrode is cut so that the positive electrode mixture layer has an area of 30 mm × 50 mm and includes an exposed portion of the aluminum foil, and an aluminum lead piece for taking out an electric current is welded to the exposed portion of the aluminum foil. And the positive electrode with a lead was obtained by performing vacuum drying at 120 degreeC for 12 hours.

(2) Preparation of negative electrode After mixing graphite as negative electrode active material, carboxymethyl cellulose as binder and styrene butadiene latex at a mass ratio of 100: 1.1: 1.5, and further adding an appropriate amount of water. The mixture was thoroughly mixed to prepare a negative electrode mixture-containing slurry. This slurry was applied to one side of the copper foil with a constant thickness on one side of the copper foil having a thickness of 10 μm. When applying the negative electrode mixture-containing slurry to the copper foil, an uncoated region was formed so that a part of the copper foil was exposed. Then, the negative electrode which consists of a negative electrode active material layer and a negative electrode collector was obtained by rolling so that the density of a negative electrode active material layer might be 1.20 g / cm < ³ > with a roll press.
Next, the negative electrode is cut so that the negative electrode mixture layer has an area of 32 mm × 52 mm and includes an exposed portion of the copper foil, and further, a nickel lead piece for taking out an electric current from the exposed portion of the copper foil Were welded and vacuum-dried at 80 ° C. for 12 hours to obtain a negative electrode with leads.

(3) Preparation of electrolyte solution As an organic solvent, a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 33: 67 (volume ratio) was used, and LiN (SO ₂ F) _{2 with} respect to the total electrolyte solution. Each electrolyte salt is dissolved so that the concentration ratio of LiPF ₆ is 75:25 (molar ratio) and the sum of the concentrations of LiN (SO ₂ F) ₂ and LiPF ₆ is 1.2 mol / L. The obtained solution was used as a non-aqueous electrolyte solution.

(4) Assembly of single layer laminated battery The positive electrode with lead and the negative electrode with lead after cutting are superposed via a polyethylene microporous membrane separator (thickness 21 μm) to form a laminated electrode body. The aluminum laminate sheet of 90 mm × 80 mm was housed in a package and vacuum dried at 80 ° C. for 5 hours in order to remove moisture. Subsequently, after injecting the above-described non-aqueous electrolyte into the exterior body, the exterior body is sealed, and the single-layer laminated lithium ion secondary battery (hereinafter referred to as the cross-sectional structure shown in FIG. Simply referred to as “single-layer laminate battery”). This single-layer laminated battery has a rated current value of 23 mAh and a rated voltage value of 4.2V.

(5) Evaluation of single-layer laminated battery For the single-layer laminated battery obtained as described above, first, a first charge / discharge treatment was performed according to the following procedure (5-1). Next, degassing is performed according to the following procedure (5-2), and the output characteristics are measured according to the following procedure (5-3). The amount of gas generated during storage was evaluated. Charging / discharging was performed using charging / discharging apparatus ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-73S (trade name) manufactured by Futaba Kagaku Co., Ltd.
Here, 1C means a current value at which a fully charged battery is discharged at a constant current and is expected to be discharged in 1 hour. In the following, it means a current value that is expected to discharge from a fully charged state of 4.2 V to 3.0 V at a constant current and finish discharging in 1 hour.

(5-1) First charge / discharge treatment of laminated battery Until the ambient temperature of the laminated battery is set to 45 ° C. and charged at a constant current of 1.125 mA corresponding to 0.05 C, the battery voltage reaches 4.5V. After charging, the battery was charged with a constant current of 4.5 V for a total of 72 hours. Thereafter, the battery was discharged to 3.0 V at a constant current of 7.5 mA corresponding to 0.3 C in a 25 ° C. environment.

(5-2) Degassing step For the lithium ion secondary battery after the initial charge / discharge treatment, a part of the aluminum laminate packaging material was opened in an Ar environment at a temperature of 25 ° C and a dew point of -60 ° C. Subsequently, a lithium ion secondary battery is placed in the decompression chamber, and the pressure is reduced from atmospheric pressure to −80 kPa over 3 minutes using a diaphragm pump (manufactured by KNF, N816.3KT.45.18). The process of returning to atmospheric pressure over 3 times was repeated a total of 3 times. Then, after putting a non-aqueous lithium-type electrical storage element in a pressure reduction sealing machine and reducing the pressure to −85 kPa, the aluminum laminate packaging material was sealed by sealing at 200 ° C. for 10 seconds with a pressure of 0.1 MPa.

(5-3) Output characteristics (discharge capacity maintenance rate)
About each laminated battery obtained by the Example and the comparative example, at 25 degreeC, after performing the constant current charge to 4.2V with the electric current value of 1 / 3C, the constant voltage charge was performed at 4.2V for 1 hour. About each laminated battery after charge, it discharged by the constant current until it became 3.0V with each current value of 1 / 3C, 10C, and the discharge capacity in each current value was measured.
The value obtained by dividing the 1 / 3C discharge capacity by the 10C discharge capacity was defined as the discharge capacity maintenance rate, expressed as a percentage, and summarized in Table 1.

(5-4) Storage test at 4.2 ° C. at 60 ° C. The lithium ion secondary battery obtained in the above step is constant until it reaches 4.2 V at a current value of 1/3 C in a thermostat set at 25 ° C. Current charging was performed, followed by constant voltage charging in which a constant voltage of 4.2 V was applied for a total of 2 hours. Thereafter, the cell was stored in a 60 ° C. environment, taken out from the 60 ° C. environment every two weeks, charged with a cell voltage of 4.2 V in the same charging step, and then stored again in the 60 ° C. environment. . This process was repeated for 2 months, and the cell volume Va before the start of the storage test and the cell volume Vb after 2 months of the storage test were measured by Archimedes method. Table 1 summarizes the gas generation amounts obtained by dividing (Vb-Va) by the 1 / 3C capacity measured in the procedure of (5-3) above.

(5-5) X-ray diffraction (XRD) analysis The lithium ion secondary battery in which the step (5-3) is performed is 4.2 V at a current value of 1/3 C in a thermostat set at 25 ° C. The battery was charged with a constant current until it reached the value, followed by a constant voltage charge of applying a constant voltage of 4.2 V for a total of 2 hours. After that, it was disassembled in an argon (Ar) box controlled at a dew point of −60 ° C. or less and an oxygen concentration of 1 ppm or less installed in a room at 23 ° C., and the negative electrode was taken out. The taken out negative electrode was immersed in dimethyl carbonate (DMC) After cleaning, in an air non-exposed state, vacuum drying was performed in a side box, and XRD (CuKα ray) was measured. In the example, the analysis result of the (004) peak position (assuming 2θ) obtained by this measurement is used, and in Comparative Example 1 and Comparative Example 2, the analysis result of the (001) peak position (assuming 2θ) is used. The results are summarized in Table 1.

(5-6) Inductively Coupled Plasma (ICP) Emission Spectroscopic Analysis The lithium ion secondary battery in which the above step (5-3) was performed was 4 at a current value of 1/3 C in a thermostat set at 25 ° C. The battery was charged with a constant current until it reached 2 V, and then a constant voltage charge was applied for 2 hours in total by applying a constant voltage of 4.2 V. After that, the negative electrode was taken out by disassembling under an Ar atmosphere, and the taken-out positive electrode was immersed and washed with dimethyl carbonate (DMC), and then vacuum-dried in a side box in a state of being not exposed to the atmosphere. (Analyte Jena, TOPwave (trade name)) was subjected to acid decomposition, and alkali metal and alkaline earth metal were detected by ICP emission spectroscopic analysis (Perkin Elmer, Optima 8300). Table 1 summarizes the analysis results, assuming that the total amount of alkali metal and alkaline earth metal excluding lithium is 100 ppm or more, “good (good)”, and less than 100 ppm, “x (bad)”.

(5-7) Quantification of compounds of formulas (1) to (3) contained in the positive electrode active material layer After adjusting the lithium ion secondary battery in which the step (5-3) was performed to 2.9 V, The positive electrode was taken out by disassembling in an argon (Ar) box controlled at a dew point of −60 ° C. or lower and an oxygen concentration of 1 ppm or lower installed in a 23 ° C. room. The positive electrode taken out was immersed and washed with dimethyl carbonate (DMC), and then vacuum-dried in a side box in a state in which exposure to the atmosphere was not maintained.
The positive electrode after drying was transferred from the side box to the Ar box in a state where exposure to air was not performed, and immersion extraction was performed with heavy water to obtain a positive electrode extract. The analysis of the extract was performed by (i) IC and (ii) ¹ H-NMR. The concentration A (mol / ml) of each compound in the obtained positive electrode extract and the volume B (ml of heavy water used for extraction). ) And the mass C (g) of the positive electrode active material layer used for extraction, the following formula 2:
Abundance per unit mass (mol / g) = A × B ÷ C (Formula 2)
Thus, the abundance (mol / g) of each compound deposited on the positive electrode per unit mass of the positive electrode active material layer was determined.

  The mass of the positive electrode active material layer used for extraction was determined by the following method. The mixture (positive electrode active material layer) was peeled off from the current collector of the positive electrode remaining after the heavy water extraction, and the peeled mixture was washed with water and then vacuum dried. The mixture obtained by vacuum drying was washed with NMP or DMF. Subsequently, the obtained positive electrode active material layer was vacuum-dried again and weighed to examine the mass of the positive electrode active material layer used for extraction.

The positive electrode extract was put in a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and a 5 mmφ NMR tube containing deuterated chloroform containing 1,2,4,5-tetrafluorobenzene (N-5 manufactured by Japan Precision Science Co., Ltd.). ) And ¹ H NMR measurement was performed by a double tube method. Normalization was performed with a signal of 1,2,4,5-tetrafluorobenzene of 7.1 ppm (m, 2H), and an integral value of each observed compound was determined.

In addition, deuterated chloroform containing dimethyl sulfoxide of known concentration is put into a 3 mmφ NMR tube (PN-002 manufactured by Shigemi Co., Ltd.), and the same deuterated chloroform containing 1,2,4,5-tetrafluorobenzene as above. Was inserted into a 5 mmφ NMR tube (N-5 manufactured by Japan Precision Science Co., Ltd.), and ¹ H NMR measurement was performed by a double tube method. In the same manner as described above, the signal was normalized with 7.1 ppm (m, 2H) of 1,2,4,5-tetrafluorobenzene, and the integral value of 2.6 ppm (s, 6H) of dimethyl sulfoxide was obtained. From the relationship between the concentration of dimethyl sulfoxide used and the integral value, the concentration A of each compound in the positive electrode extract was determined.

Assignment of ¹ H NMR spectrum is as follows.
[About XOCH ₂ CH ₂ OX]
XOCH ₂ CH ₂ OX CH ₂ : 3.7 ppm (s, 4H)
CH ₃ OX: 3.3 ppm (s, 3H)
CH ₃ CH ₂ OX CH ₃ : 1.2 ppm (t, 3H)
CH ₃ CH ₂ OX of _{CH 2 O: 3.7ppm (q,} 2H)
As described _above, the signal (3.7 ppm) is XOCH 2 _CH 2 OX of CH _2, since the overlaps with CH 3 _CH 2 OX of CH ₂ O signals (3.7 _ppm), the CH 3 _CH 2 OX except for the CH ₂ O equivalent of _CH 3 _CH 2 OX calculated from CH ₃ signal (1.2 ppm), was calculated an amount of a compound of formula (1) to (3).
In the above, each X is — (COO) _n M or — (COO) _n R ¹ (where n is 0 or 1 and R ¹ is an alkyl group having 1 to 4 carbon atoms, or A halogenated alkyl group having 1 to 4 carbon atoms, and M is an element selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, or Ba).

  The formula contained in the positive electrode active material layer from the concentration of each compound obtained by the analysis of (i) and (ii) above, the volume of heavy water used for extraction, and the active material mass of the positive electrode used for extraction The amounts of the compounds (1) to (3) were measured and summarized in Table 1.

<Examples 1 to 9 and Comparative Examples 1 and 2>
Batteries were prepared and evaluated by the method described above using Compound 1 and / or Compound 2 at the compounding ratio shown in Table 1 below. In Comparative Examples 1 and 2, a compound containing an alkali metal or alkaline earth metal having an atomic radius larger than that of lithium is not incorporated in the positive electrode precursor.

  From the above results, in the lithium ion secondary battery using the electrolytic solution of the present embodiment, one or more alkali metal and / or alkaline earth metal having a larger atomic radius than lithium and the carbon material-containing negative electrode are intercalation compounds. In order to achieve high output characteristics and to contain one or more compounds selected from the above formulas (1) to (3) in the positive electrode active material layer, excellent high temperature durability can be obtained. Realized to be realized.

  The lithium ion secondary battery of the present invention is, for example, a portable device such as a mobile phone, a portable audio device, a personal computer, an IC (Integrated Circuit) tag; a rechargeable battery for a vehicle such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle; It can be applied to a residential power storage system.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Battery exterior 3 Positive electrode external terminal 4 Negative electrode external terminal 5 Positive electrode 6 Negative electrode 7 Separator 8 Laminate film

Claims (6)

A positive electrode having a positive electrode active material layer including a positive electrode active material made of a transition metal oxide capable of occluding and releasing lithium ions;
Carbon material-containing negative electrode;
A separator; and a non-aqueous electrolyte containing the lithium ion;
A lithium ion secondary battery comprising
The carbon material-containing negative electrode forms an interlayer compound with lithium and one or more alkali metals and / or alkaline earth metals having a larger atomic radius than lithium,
The lithium ion secondary battery.   The carbon material-containing negative electrode is measured by inductively coupled plasma (ICP) emission spectrometry, and the one or more types of alkali metal and / or alkaline earth metal are detected in a total of 100 ppm or more. Lithium ion secondary battery. The positive electrode active material layer has the following formulas (1) to (3):
^{M 1 X 1 -OR 1 O-} X 2 M 2 ······ (1)
{In the formula (1), are each ^{M 1} and ^{M 2} independently is an element selected Li, Na, K, Rb, Cs, Mg, Ca, Sr, or from Ba, ^{R 1} is 1 to the number of carbon atoms 4 alkylene group or a halogenated alkylene group having 1 to 4 carbon atoms, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
^{M 1 X 1 -OR 1 O-} X 2 R 2 ······ (2)
{In Formula (2), M ¹ is an element selected from Li, Na, K, Rb, Cs, Mg, Ca, Sr, or Ba, and R ¹ is an alkylene group having 1 to 4 carbon atoms, or A halogenated alkylene group having 1 to 4 carbon atoms, R ² is hydrogen, an alkyl group having 1 to 10 carbon atoms, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, A mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
^{R 2 X 1 -OR 1 O-} X 2 R 3 ······ (3)
{In Formula (3), R ¹ is an alkylene group having 1 to 4 carbon atoms or a halogenated alkylene group having 1 to 4 carbon atoms, and R ² and R ³ are independently hydrogen and 1 to 10 carbon atoms. An alkyl group, a mono- or polyhydroxyalkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a mono- or polyhydroxyalkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or An aryl group, and X ¹ and X ² are each independently — (COO) _n (where n is 0 or 1). }
The compound of 3.8 × 10 ⁻⁹ mol / g to 3.0 × 10 ⁻² mol / g per unit mass of the positive electrode active material layer is contained at least one compound selected from the group consisting of Or the lithium ion secondary battery of 2.   4. The lithium ion secondary battery according to claim 1, which has a (004) peak at 2θ ≦ 23 ° in X-ray diffraction (XRD) measurement (CuKα ray) of the carbon material-containing negative electrode. 5. . A positive electrode having a positive electrode active material layer containing a transition metal oxide capable of inserting and extracting lithium ions and one or more alkali metal compounds and / or alkaline earth metal compounds;
Carbon material-containing negative electrode;
A separator; and a non-aqueous electrolyte containing the lithium ion;
An alkali metal ion secondary battery containing
The carbon material-containing negative electrode forms an interlayer compound with lithium and one or more alkali metals and / or alkaline earth metals having a larger atomic radius than lithium,
The alkali metal ion secondary battery.   The alkali metal ion secondary battery according to claim 5, wherein the alkali metal compound and / or alkaline earth metal compound is at least one selected from the group consisting of carbonates, hydroxides and oxides.

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