JPWO2019151501A1 - Lithium ion secondary battery - Google Patents

Abstract

A positive electrode containing a positive electrode active material, an electrolyte layer, and a negative electrode containing a negative electrode active material are provided, and the electrolyte layer includes an ionic liquid, at least one of a glyme represented by the following general formula (1), a lithium salt, and the like. Disclosed is a lithium ion secondary battery in which the negative electrode active material has an operating potential nobler than 1 V with respect to the metallic lithium potential, and the capacity of the negative electrode is larger than the capacity of the positive electrode. R1O- (CH2CH2O) m-R2 (1) [In formula (1), R1 and R2 each independently represent an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 6. ]

Description

The present invention relates to a lithium ion secondary battery.

In recent years, the development of lithium-ion secondary batteries has been actively promoted. For example, Patent Document 1 describes insertion / desorption of olivine-based lithium iron phosphate (LiFePO ₄ ) having an operating voltage of 4 V (vs. Li / Li ⁺ ) or less as a positive electrode active material and Li ions as a negative electrode active material. Using lithium titanate (Li ₄ Ti ₅ O ₁₂ ) performed near 1.4 to 1.7 V (vs. Li / Li ⁺ ), lithium ions containing an ether compound and an ionic conductive salt as a non-aqueous electrolytic solution. Secondary batteries are disclosed. In a lithium ion secondary battery using such a non-aqueous electrolyte solution, the temperature of the battery may suddenly rise in an abnormal situation, the non-aqueous electrolyte solution may vaporize, the internal pressure rises, and the battery may explode. Therefore, attempts have been made to solidify the components used in the non-aqueous electrolyte solution.

Japanese Unexamined Patent Publication No. 2010-277958

However, according to the study by the present inventors, in a lithium ion secondary battery in which a component used in a non-aqueous electrolyte solution is solidified, the component (particularly, an ether compound) is reduced and decomposed on the negative electrode side at the end of charging. It may occur and the charge / discharge characteristics may deteriorate.

The present invention has been made in view of such circumstances, and provides a lithium ion secondary battery having excellent charge / discharge characteristics when the components used in the non-aqueous electrolytic solution are solidified. The purpose.

As a result of diligent studies by the present inventors, they have found that the above problems can be solved by adjusting the capacity of the positive electrode and the capacity of the negative electrode in a lithium ion secondary battery having a specific configuration, and have completed the present invention. It was.

The present invention provides the lithium ion secondary batteries shown in the following [1] to [4].

[1] A positive electrode containing a positive electrode active material, an electrolyte layer, and a negative electrode containing a negative electrode active material are provided, and the electrolyte layer includes at least one of an ionic liquid and a glyme represented by the following general formula (1), and lithium. A lithium ion secondary battery in which the negative electrode active material contains a salt and has an operating potential noble than 1 V with respect to the metallic lithium potential, and the capacity of the negative electrode is larger than the capacity of the positive electrode.
R ¹ O- (CH ₂ CH ₂ O) _m- R ² (1)
[In the formula (1), R ¹ and R ² each independently represent an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 6. ]
[2] The lithium ion secondary battery according to [1], wherein the negative electrode active material contains a spinel-type lithium titanate represented by the composition formula Li ₄ Ti ₅ O ₁₂ .
[3] The lithium ion secondary battery according to [1] or [2], wherein the electrolyte layer contains tetraethylene glycol dimethyl ether and lithium bis (trifluoromethanesulfonyl) imide.
[4] The lithium ion secondary battery according to any one of [1] to [3], wherein the anion of the ionic liquid is a bis (trifluoromethanesulfonyl) imide anion.

According to the present invention, there is provided a lithium ion secondary battery having excellent charge / discharge characteristics when the components used in the non-aqueous electrolytic solution are solidified.

It is a schematic cross-sectional view which shows the lithium ion secondary battery which concerns on one Embodiment. It is a schematic cross-sectional view which shows the lithium ion secondary battery which concerns on other embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including steps and the like) are not essential unless otherwise specified. The sizes of the components in each figure are conceptual, and the relative size relationships between the components are not limited to those shown in each figure.

The same applies to the numerical values and their ranges in the present specification, and does not limit the present invention. In the present specification, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Good. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

In the present specification, a lithium ion secondary battery will be described as an example of the all-solid secondary battery, but the technical idea of the present invention is that the lithium ion secondary battery, the sodium ion secondary battery, and the magnesium ion secondary battery are used as an example. It can also be applied to batteries, aluminum ion secondary batteries, and the like.

[Lithium-ion secondary battery]
FIG. 1 is a schematic cross-sectional view showing an embodiment of a lithium ion secondary battery. The lithium ion secondary battery 100 includes a positive electrode 70 including a positive electrode current collector 10 and a positive electrode mixture layer 40 provided on the positive electrode current collector 10, an electrolyte layer 50, a negative electrode current collector 20, and a negative electrode current collector. A negative electrode 80 including a negative electrode mixture layer 60 provided on the 20 is provided. Further, the lithium ion secondary battery 100 may further include an exterior body 30 that houses a positive electrode 70, an electrolyte layer 50, and a negative electrode 80.

[Positive electrode]
The positive electrode 70 includes a positive electrode current collector 10 and a positive electrode mixture layer 40. The positive electrode mixture layer 40 includes a positive electrode active material, a positive electrode conductive material for imparting conductivity, and a positive electrode binder for binding these.

The capacity of the positive electrode 70 is not particularly limited as long as it is smaller than the capacity of the negative electrode 80, and can be appropriately adjusted according to the design of the battery to be manufactured. The capacity of the positive electrode 70 can be adjusted, for example, by measuring the capacity (mAh / g) per mass of the positive electrode active material in advance and increasing or decreasing the charged mass of the positive electrode active material. The capacity (mAh / g) per mass of the positive electrode active material can be determined by a unipolar test or the like using a lithium metal as the counter electrode.

The capacity of the positive electrode 70 can be lowered or increased according to the design of the battery to be manufactured, and can be appropriately adjusted in the range of, for example, 0.01 mAh to 100 Ah. The capacity of the positive electrode 70 may be 0.1 mAh or more, 0.5 mAh or more, or 1 mAh or more, 90 Ah or less, 80 Ah or less, 60 Ah or less, 40 Ah or less, 20 Ah or less, 10 Ah or less, 5 Ah or less, 1 Ah or less, or It may be 0.1 Ah or less.

<Positive current collector>
The positive electrode current collector 10 is not particularly limited, and a positive electrode current collector generally used in a secondary battery can be used. The positive electrode current collector 10 is preferably a low resistance conductor having heat resistance that can withstand heating during the secondary battery manufacturing process and the operating temperature of the secondary battery. Examples of such a positive current collector 10 include a metal foil (thickness 10 to 100 μm), a perforated metal foil (thickness 10 to 100 μm, pore diameter 0.1 to 10 mm), an expanded metal, a foamed metal plate, and a glassy carbon plate. And so on. Examples of the metal type include aluminum, stainless steel, titanium, precious metals (for example, gold, silver, platinum) and the like.

<Positive electrode mixture layer>
The positive electrode mixture layer 40 transfers the positive electrode mixture slurry obtained by mixing the positive electrode active material, the positive electrode conductive material, the positive electrode binder, the dispersion medium, etc. to the positive electrode current collector 10 by a doctor blade method, a dipping method, a spray method, or the like. After coating, the dispersion medium is dried and can be produced by pressure molding with a roll press. Further, the positive electrode mixture layer 40 can be laminated on the positive electrode current collector 10 by performing the steps from application to drying a plurality of times. The single-sided coating amount of the positive electrode mixture layer 40 on the positive electrode current collector 10 is applied to the negative electrode current collector 20 of the negative electrode mixture layer 60 so as to satisfy the relationship between the capacity of the negative electrode 80 and the capacity of the positive electrode 70, which will be described later. It can be appropriately adjusted according to the amount of one-sided coating.

(Positive electrode active material)
The positive electrode active material may be, for example, a lithium composite oxide containing a transition metal. Examples of the lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , Li ₄ Mn ₅ O ₁₂ , Li ₂ Mn ₃ MO ₈ (M = Fe, Co). , Ni, Cu, Zn), Li _1-x M _x Mn ₂ O ₄ (M = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, x = 0.01 to 0.1), LiMn _2-x M _x O ₂ (M = Co, Ni, Fe, Cr, Zn, Ta, x = 0.01 to 0.2), LiCo _1-x M _x O ₂ (M = Ni, Fe, Mn) , X = 0.01 to 0.2), LiNi _1-x M _x O ₂ (M = Mn, Fe, Co, Al, Ga, Ca, Mg, x = 0.01 to 0.2), LiNi _{1 -x-y Mn x Co y O} 2 (x = 0.1~0.8, y = 0.1~0.8, x + y = 0.1~0.9), LiFeO 2, LiFePO 4, LiMnPO 4 And so on.

(Positive electrode conductive material)
Positive positive conductive materials are manufactured from acrylic fibers and fibers produced by carbonizing conductive fibers (for example, by-products such as vapor-grown carbon, carbon nanotubes, and pitch (by-products of petroleum, coal, coal tar, etc.)) at high temperatures. It may be carbon fiber, etc.). Further, the positive electrode conductive material preferably has a lower electrical resistivity than the positive electrode active material and is difficult to oxidize and dissolve at the positive electrode charge / discharge potential (usually 2.5 to 4.5 V). As such a material, for example, corrosion resistant metal (titanium, gold, etc.), carbides (SiC, WC, etc.), nitrides _{(Si 3} N 4, BN, etc.) and the like. Further, the positive electrode conductive material may be a carbon material having a high specific surface area (for example, carbon black, activated carbon, etc.).

(Positive binder)
Examples of the positive electrode binder include styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride (PVDF); and a mixture thereof.

(Dispersion medium)
Examples of the dispersion medium include water, 1-methyl-2-pyrrolidone and the like.

[Negative electrode]
The negative electrode 80 includes a negative electrode current collector 20 and a negative electrode mixture layer 60. The negative electrode mixture layer 60 includes a negative electrode active material, a negative electrode conductive material for imparting conductivity, and a negative electrode binder for binding these.

The capacity of the negative electrode 80 is not particularly limited as long as it is larger than the capacity of the positive electrode 70, and can be appropriately adjusted according to the design of the battery to be manufactured. The capacity of the negative electrode 80 can be adjusted, for example, by measuring the capacity per mass (mAh / g) of the negative electrode active material in advance and increasing or decreasing the charged mass of the negative electrode active material, as in the case of the positive electrode 70. .. The capacity (mAh / g) per mass of the negative electrode active material can be determined by a unipolar test or the like using a lithium metal as the counter electrode.

Regarding the relationship between the capacity of the negative electrode 80 and the capacity of the positive electrode 70, when the capacity of the negative electrode 80 is N (mAh) and the capacity of the positive electrode 70 is P (mAh), N / P exceeds 1.00. The N / P may be 1.05 or more, 1.10 or more, or 1.20 or more, and the N / P may be 2.00 or less, 1.80 or less, or 1.50 or less. By making the capacity of the negative electrode 80 larger than the capacity of the positive electrode 70, the lithium ion secondary battery has excellent charge / discharge characteristics. The reason for this is not necessarily clear, but it is considered that the reduction decomposition of the grime or ionic liquid contained in the electrolyte layer described later is suppressed.

<Negative electrode current collector>
The negative electrode current collector 20 is not particularly limited, and a negative electrode current collector generally used in a secondary battery can be used. Like the positive electrode current collector 10, the negative electrode current collector 20 is preferably a low resistance conductor having heat resistance that can withstand heating during the secondary battery manufacturing process and the operating temperature of the secondary battery. Examples of such a negative electrode current collector 20 include a metal foil (thickness 10 to 100 μm), a perforated metal foil (thickness 10 to 100 μm, pore diameter 0.1 to 10 mm), an expanded metal, a foamed metal plate, and a glassy carbon plate. And so on. Examples of the metal type include aluminum, stainless steel, titanium, precious metals (for example, gold, silver, platinum) and the like.

<Negative electrode mixture layer>
The negative electrode mixture layer 60 transfers a negative electrode mixture slurry obtained by mixing a negative electrode active material, a negative electrode conductive material, a negative electrode binder, a dispersion medium, etc. to the negative electrode current collector 20 by a doctor blade method, a dipping method, a spray method, or the like. After coating, the dispersion medium is dried and can be produced by pressure molding with a roll press. Further, the negative electrode mixture layer 60 can be laminated on the negative electrode current collector 20 by performing the steps from coating to drying a plurality of times. The amount of the negative electrode mixture layer 60 applied to the negative electrode current collector 20 on one side is 10 to 225 g / m ² or 50 to 200 g / m as the solid content of the negative electrode mixture layer 60 from the viewpoint of energy density and input / output characteristics. ^2, or a 80~160g / ^{m 2.}

(Negative electrode active material)
The negative electrode active material has an operating potential noble than 1 V with respect to the metallic lithium potential. Such negative electrode active material, for _{example, CuO, Cu 2 O, Ag} 2 O, CuS, 11 metal compounds such as _{CuSO 4, TiS 2, SiO 2} , 4 or 14 metal compounds of SnO etc., _{V 2} Group 5 metal compounds such as O ₅ , V ₆ O ₁₂ , VO _x , Nb ₂ O ₅ , Bi ₂ O ₃ , Sb ₂ O ₃ , CrO ₃ , Cr ₂ O ₃ , MoO ₃ , MoS ₂ , WO ₃ , SeO group 6 metal compounds such as _{2, MnO 2, Mn 2 O} 7 group metal compounds such as _{3, Fe 2 O 3, FeO} , Fe 3 O 4, Ni 2 O 3, NiO, CoO 3, 8-10 of CoO etc. Group metal compounds, lithium titanate (0 ≦ y ≦ 1) represented by the composition formulas Li _y TiO ₂ , Li _{4 + y} Ti ₅ O ₁₂ , Li _{4 + y} Ti ₁₁ O ₂₀ , and conductive polymer materials (eg, polyacene, poly Paraphenylene, polyaniline, polyacetylene), pseudo-graphite structural carbon material and the like. Among these, the negative electrode active material has a flat potential of 1.4 to 1.6 V with respect to the metallic lithium potential, and can occlude most of lithium at 1.2 V or more with respect to the lithium potential. Therefore, it is preferable to contain a spinel-type lithium titanate represented by the composition formula Li ₄ Ti ₅ O ₁₂ .

(Negative electrode conductive material)
As the negative electrode conductive material, the same material as those exemplified for the positive electrode conductive material can be used.

(Negative electrode binder)
As the negative electrode binder, the same one as illustrated in the positive electrode binder can be used.

(Dispersion medium)
Examples of the dispersion medium include water, 1-methyl-2-pyrrolidone and the like.

[Electrolyte layer]
The electrolyte layer 50 contains an electrolyte component and an electrolyte binder. The electrolyte layer 50 can be produced, for example, by adding an electrolyte binder to the electrolyte components and mixing them. The electrolyte layer 50 can also be produced by preparing a solution obtained by mixing an electrolyte component and an electrolyte binder with a dispersion medium and distilling off the dispersion medium.

<Electrolyte component>
The electrolyte component is composed of inorganic particles and an ionic conductive material. The ionic conductive material may be supported on inorganic particles. As the electrolyte component, for example, inorganic particles and an ionic conductive material are mixed at a specific volume ratio, and a dispersion medium such as methanol is added and mixed to prepare an electrolyte component slurry. After that, the slurry can be dropped onto a petri dish and the dispersion medium is distilled off to obtain an electrolyte component.

(Inorganic particles)
From the viewpoint of electrochemical stability, the inorganic particles are preferably insulating particles and are insoluble in grime represented by the general formula (1) described later or a molten salt having a melting point of 250 ° C. or lower. Such inorganic particles may be, for example, silica (SiO ₂ ) particles, γ-alumina (Al ₂ O ₃ ) particles, ceria (CeO ₂ ) particles, or zirconia (ZrO ₂ ) particles. Further, the inorganic particles may be other known metal oxide particles.

The holding amount of the ionic conductive material is considered to be proportional to the specific surface area of the inorganic particles. The average particle size of the primary particles of the inorganic particles may be 1 nm to 10 μm. When the average particle size is 10 μm or less, the inorganic particles can hold a sufficient amount of the ionic conductive material, and tend to easily form an electrolyte layer. When the average particle size is 1 nm or more, the intersurface force between the particles becomes too large to prevent the particles from agglutinating with each other, and the electrolyte layer tends to be easily formed. Further, the average particle size of the primary particles of the metal oxide particles may be 1 to 50 nm or 1 to 10 nm. The average particle size of the primary particles can be determined by using a known particle size distribution measuring device using a laser scattering method.

When SiO ₂ particles (average particle size: 7 nm, zeta potential: about -20 mV) are used as the inorganic particles, a highly heat-resistant electrolyte layer tends to be obtained.

When γ-Al ₂ O ₃ particles (average particle size: 5 nm, zeta potential: about -5 mV) are used as the inorganic particles, it tends to be possible to extend the number of charge / discharge cycles of the secondary battery. The reason why such an effect is exerted is not clear, but it is considered that the use of alumina particles having high reduction resistance can suppress the precipitation of lithium dendrite on the negative electrode side during the charge / discharge cycle.

When CeO ₂ particles (zeta potential: about 30 mV) or ZrO ₂ particles (zeta potential: about 40 mV) are used as the inorganic particles, a highly ionic conductive electrolyte layer tends to be obtained. It is considered that when particles having a high zeta potential are used as the inorganic particles, the adsorption of the ionic conductive material on the particle surface is weakened, and the ionic conductive material can move relatively freely. As a result, it is predicted that lithium ions will easily move from the ionic conductive material and lithium ion conduction will be promoted.

As the inorganic particles, by using an inorganic substance having lithium ion conductivity, an electrolyte layer having more excellent ion conductivity tends to be obtained. Examples of such an inorganic substance include Li _{5 + X} La ₃ (Zr _X , A _2-X ) O ₁₂ (in the formula, A is Sc, Ti, C, Y, Nb, Hf, Ta, Al, Si, Ga. , Ge, Sn One or more elements selected from the group, 1.4 ≤ X ≤ 2), Li _{1 + Y} Al _Y Ti _2-Y (PO ₄ ) ₃ (0 ≤ Y ≤ 1), Li _3Z La _{2 / 3-Z} TiO ₃ (0 ≦ Z ≦ 2/3) and the like can be mentioned. They tend to have high ionic conductivity at room temperature and high electrochemical stability.

(Ion conductive material)
The ionic conductive material contains an ionic liquid, a grime represented by the following general formula (1), and a lithium salt.
R ¹ O- (CH ₂ CH ₂ O) _m- R ² (1)

In formula (1), R ¹ and R ² each independently represent an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 6. The alkyl group as R ¹ and R ² may be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group and the like. Among these, the alkyl group is preferably a methyl group or an ethyl group.

The ionic liquid is not particularly limited, and known ionic liquids can be used. The anion of the ionic liquid is preferably a bis (trifluoromethanesulfonyl) imide anion from the viewpoint of ionic conductivity (conductivity). The ionic liquid is N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium-bis (trifluoromethanesulfonyl) imide (also referred to as "DEME-TFSI") or 1-butyl-3-3. Methylimidazolium bis (trifluoromethanesulfonyl) imide (also referred to as "BMI-TFSI") is preferred.

From the viewpoint of ionic conductivity (conductivity), ethylene glycol dimethyl ether (also referred to as "monoglyme"), diethylene glycol dimethyl ether (also referred to as "diglyme"), triethylene glycol dimethyl ether (also referred to as "triglime"), It may be tetraethylene glycol dimethyl ether (also referred to as "tetraglyme"), pentaethylene glycol dimethyl ether (also referred to as "pentaglyce"), hexaethylene glycol dimethyl ether (also referred to as "hexaglyme") or the like. Among these, the grime is preferably triglime or tetraglime, and more preferably tetraglime.

Examples of the lithium _{salt, LiPF 6, LiBF 4, LiClO} 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, lithium bis oxalate borate (LiBOB), lithium imide salt (e.g., lithium bis (Fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI)) and the like can be mentioned. These lithium salts may be used individually by 1 type or in combination of 2 or more type. Among these, the lithium salt is preferably LiFSI or LiTFSI, and more preferably LiTFSI.

<Electrolyte binder>
A fluorine-based resin is preferably used as the electrolyte binder. Examples of the fluorine-based resin include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). By using PVDF or PTFE, the adhesion between the electrolyte layer and the electrode current collector is improved, so that the battery performance tends to be improved.

[Exterior body]
The exterior body 30 is a battery case that can accommodate the positive electrode 70, the electrolyte layer 50, and the negative electrode 80. The material of the exterior body is preferably one having corrosion resistance such as aluminum, stainless steel, and nickel-plated steel.

FIG. 2 is a schematic cross-sectional view showing another embodiment of the lithium ion secondary battery. The lithium ion secondary battery 200 includes a positive electrode 70, an electrolyte layer 50, a negative electrode mixture layer 60, an interconnector 90, a positive electrode mixture layer 40, an electrolyte layer 50, a negative electrode mixture layer 60, and an interconnector. 90, a positive electrode mixture layer 40, an electrolyte layer 50, and a negative electrode are provided in this order. As shown in FIG. 2, the lithium ion secondary battery 200 has an electrode group having a positive electrode mixture layer 40, an electrolyte layer 50, and a negative electrode mixture layer 60 in this order via an interconnector 90, and a negative electrode mixture layer. A plurality of the 60 and the positive electrode mixture layer 40 are provided so as to be adjacent to each other. Of the plurality of electrode groups, the outermost positive electrode mixture layer 40 is connected to the positive electrode current collector 10, and the outermost negative electrode mixture layer 60 is connected to the negative electrode current collector 20.

[Interconnector]
The interconnector 90 is required to have high electron conductivity, no ionic conductivity, and the surfaces in contact with the negative electrode mixture layer 60 and the positive electrode mixture layer 40 do not exhibit a redox reaction depending on their respective potentials. .. The interconnector 90 may be used as the positive electrode current collector 10 and the negative electrode current collector 20, and may be an aluminum foil or a SUS foil.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited thereto.

(Example 1)
<Preparation of positive electrode>
LiFePO ₄ was used as the positive electrode active material. LiFePO ₄ powder and Ketjen black (positive electrode conductive material) were mixed, and polyvinylidene fluoride (positive electrode binder) was added thereto. This mixture was put into N-methyl-2-pyrrolidone (dispersion medium), and the viscosity was adjusted to obtain a positive electrode mixture slurry. The mass ratio of each component was positive electrode active material: positive electrode conductive material: positive electrode binder = 90: 5: 5. A positive electrode mixture slurry is applied onto an aluminum foil (positive electrode current collector), subjected to heat treatment at 80 ° C. for 2 hours, and then punched at φ13 mm to obtain a positive electrode having a positive electrode mixture layer on the positive electrode current collector. It was. The capacity of the obtained positive electrode was evaluated as a single electrode and found to be 2.0 mAh.

<Manufacturing of negative electrode>
As the negative electrode active material, spinel-type lithium titanate represented by the composition formula Li ₄ Ti ₅ O ₁₂ was used. The operating potential of Li ₄ Ti ₅ O ₁₂ is 1.4 to 1.7 V (vs. Li / Li ⁺ ). Li ₄ Ti ₅ O ₁₂ powder and Ketjen black (negative electrode conductive material) were mixed, and polyvinylidene fluoride (negative electrode binder) was added thereto. This mixture was put into N-methyl-2-pyrrolidone (dispersion medium), and the viscosity was adjusted to obtain a negative electrode mixture slurry. Each component had a mass ratio of negative electrode active material: negative electrode conductive material: negative electrode binder = 88: 5: 7. A negative electrode mixture slurry was applied onto the negative electrode current collector of copper foil, subjected to heat treatment at 80 ° C. for 2 hours, and then punched at φ13 mm to obtain a negative electrode having a negative electrode mixture layer on the negative electrode current collector. .. The capacity of the obtained negative electrode was evaluated as a single electrode and found to be 2.7 mAh.

<Preparation of sheet for electrolyte layer>
Tetra grime (grime) and LiTFSI (lithium salt) were mixed and stirred at room temperature for 30 minutes or more using a stirrer to prepare an ionic conductive material. Next, SiO ₂ particles (inorganic particles) were mixed with the prepared ionic conductive material. At this time, the volume ratio of tetraglime and SiO ₂ particles was set to 8: 2. Next, the obtained electrolyte component slurry was transferred onto a petri dish, and methanol was distilled off on a hot plate at 60 ° C. to obtain an electrolyte component as a white powder. Polytetrafluoroethylene (PTFE, electrolyte binder) was added so as to be 5% by mass with respect to the prepared electrolyte component, and mixed in an agate mortar to obtain a translucent sheet for an electrolyte layer.

<Battery production>
The prepared positive electrode, negative electrode, and electrolyte layer sheet were dried at 100 ° C. for 2 hours or more, and then transferred into a glove box filled with argon. A coin cell battery was produced by stacking a negative electrode, an electrolyte layer sheet, and a positive electrode in this order, covering them with a coin-shaped cell member (exterior body), and sealing them.

<Evaluation of charge / discharge characteristics>
Using the produced coin cell battery, the discharge capacity and the Coulomb efficiency were measured under the conditions of a charge / discharge rate of 0.05 C, an upper limit voltage of 2.8 V, and a lower limit voltage of 1.0 V, and the charge / discharge characteristics were evaluated. The results are shown in Table 1.

(Example 2)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 2.6 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 2.4 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 4)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 2.2 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 2.1 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
A coin cell battery was produced in the same manner as in Example 1 except that the tetraglime was changed to DEME-TFSI (ionic liquid). The capacity of the positive electrode was 2 mAh, and the capacity of the negative electrode was 2.7 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 7)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 2.6 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 8)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 2.4 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 9)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 2.2 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 10)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 2.1 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Example 11)
A coin cell battery was produced in the same manner as in Example 1 except that the tetraglime was changed to BMI-TFSI (ionic liquid). The capacity of the positive electrode was 2 mAh, and the capacity of the negative electrode was 2.7 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Example 12)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 2.6 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Example 13)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 2.4 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Example 14)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 2.2 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Example 15)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 2.1 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 1)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 1.9 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 1.8 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 1.7 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 4)
A coin cell battery was produced in the same manner as in Example 1 except that the negative electrode was changed to a negative electrode having a capacity of 1.6 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 5)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 1.9 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 6)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 1.8 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 7)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 1.7 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 8)
A coin cell battery was produced in the same manner as in Example 6 except that the negative electrode was changed to a negative electrode having a capacity of 1.6 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 9)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 1.9 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 10)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 1.8 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 11)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 1.7 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

(Comparative Example 12)
A coin cell battery was produced in the same manner as in Example 11 except that the negative electrode was changed to a negative electrode having a capacity of 1.6 mAh. The charge / discharge characteristics of the obtained coin cell battery were evaluated in the same manner as in Example 1. The results are shown in Table 3.

The lithium ion secondary batteries of Examples 1 to 15 in which the capacity of the negative electrode is larger than the capacity of the positive electrode have a higher discharge than the lithium ion secondary batteries of Comparative Examples 1 to 12 in which the capacity of the negative electrode is smaller than the capacity of the positive electrode. The capacity and Coulomb efficiency were shown. It is considered that this is because the negative electrode capacity is made larger than the positive electrode capacity, so that the negative electrode potential is kept constant at the end of charging and the reductive decomposition of the grime or the ionic liquid is suppressed. From these results, it was confirmed that the lithium ion secondary battery of the present invention has excellent charge / discharge characteristics even when no electrolytic solution is used.

10 ... Positive electrode current collector, 20 ... Negative electrode current collector, 30 ... Exterior body, 40 ... Positive electrode mixture layer, 50 ... Electrolyte layer, 60 ... Negative electrode mixture layer, 70 ... Positive electrode, 80 ... Negative electrode, 90 ... Interconnector , 100, 200 ... Lithium ion secondary battery.

Claims (4)

A positive electrode containing a positive electrode active material, an electrolyte layer, and a negative electrode containing a negative electrode active material are provided.
The electrolyte layer contains an ionic liquid, at least one of grime represented by the following general formula (1), and a lithium salt.
The negative electrode active material has an operating potential nobler than 1 V with respect to the metallic lithium potential.
A lithium ion secondary battery in which the capacity of the negative electrode is larger than the capacity of the positive electrode.
R ¹ O- (CH ₂ CH ₂ O) _m- R ² (1)
[In the formula (1), R ¹ and R ² each independently represent an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 6. ] The lithium ion secondary battery according to claim 1, wherein the negative electrode active material contains a spinel-type lithium titanate represented by the composition formula Li ₄ Ti ₅ O ₁₂ . The lithium ion secondary battery according to claim 1 or 2, wherein the electrolyte layer contains tetraethylene glycol dimethyl ether and lithium bis (trifluoromethanesulfonyl) imide. The lithium ion secondary battery according to any one of claims 1 to 3, wherein the anion of the ionic liquid is a bis (trifluoromethanesulfonyl) imide anion.

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