JP2021015769A - Electrode for non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide an electrode for non-aqueous electrolyte secondary battery capable of exhibiting excellent output characteristics and fast charge characteristics.SOLUTION: An electrode for non-aqueous electrolyte secondary battery has a collector, and an electrode active material layer, i.e., a non-bonded body placed on the surface of the collector. The electrode active material layer contains an electrode active material, a gel formative polymer and electrolyte, where the gel formative polymer is at least one kind selected from a group consisting of polyvinylidene fluoride-hexafluoropropylene (PVDF-HEP), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethyleneglycol (PEG), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene glycol dimetacrylate, polyethylene glycol diacrylate, polypropylene glycol dimetacrylate and polypropylene glycol diacrylate, and their copolymers. In the electrode active material layer, when the content of the gel formative polymer is x (mass%) by solid content conversion, and the viscosity of non-aqueous solvent composing the electrolyte is y (mPa s) at 25°C, following relationship is satisfied; x2y≤22.8.SELECTED DRAWING: None

Description

The present invention relates to electrodes for non-aqueous electrolyte secondary batteries.

In recent years, various electric vehicles are expected to become widespread in order to solve environmental and energy problems. Secondary batteries are being enthusiastically developed as in-vehicle power sources such as motor drive power sources that hold the key to the spread of these electric vehicles. As a secondary battery, a non-aqueous electrolyte secondary battery, which is expected to have high energy density and high output, is attracting attention.

As a technique for obtaining a battery having a high energy density and a high output, Patent Document 1 discloses an electrode using a gelling agent as a binder for a carbon-based active material.

Japanese Unexamined Patent Publication No. 2004-281162

However, as a result of studies by the present inventors, it has been found that sufficient output characteristics cannot be obtained in the case of a battery using the technique described in Patent Document 1.

On the other hand, in addition to improving the output characteristics, it is required to be able to cope with quick charging.

Therefore, an object of the present invention is to provide an electrode for a non-aqueous electrolyte secondary battery capable of exhibiting excellent output characteristics and quick charging characteristics.

The present inventors have conducted diligent studies to solve the above problems. As a result, it was found that it is effective to control the content of the gel-forming polymer and the viscosity of the non-aqueous solvent constituting the electrolytic solution in the electrode active material layer constituting the electrode so as to satisfy a predetermined relationship. , The present invention has been completed.

That is, the electrode for a non-aqueous electrolyte secondary battery according to the present invention has a current collector and an electrode active material layer which is a non-binding body arranged on the surface of the current collector. Here, the electrode active material layer contains an electrode active material, a gel-forming polymer and an electrolytic solution, and the gel-forming polymer is polyvinylidene fluoride-hexafluoropropylene (PVDF-HEP), polyethylene oxide (PEO), and the like. Polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate and polypropylene glycol diacrylate, and their co-weights. It is at least one selected from the group consisting of coalescence, and the content of the gel-forming polymer in the electrode active material layer is x [mass%] in terms of solid content, and constitutes the electrolytic solution at 25 ° C. when the viscosity of the nonaqueous solvent was set to y [mPa · s], and satisfies a ^{x 2} y ≦ 22.8.

According to the electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention, excellent output characteristics and quick charging characteristics can be exhibited.

It is sectional drawing which represented typically the bipolar type secondary battery which is one Embodiment of this invention. It is sectional drawing which shows the basic structure of the laminated type (flat type) non-bipolar type (internal parallel connection type) non-aqueous electrolyte secondary battery which is one Embodiment of this invention. It is a perspective view which showed the appearance of the flat lithium ion secondary battery which is a typical embodiment of a secondary battery.

One embodiment of the present invention is an electrode for a non-aqueous electrolyte secondary battery having a current collector and an electrode active material layer which is a non-binding body arranged on the surface of the current collector. Here, the electrode active material layer contains an electrode active material, a gel-forming polymer and an electrolytic solution, and the gel-forming polymer is polyvinylidene fluoride-hexafluoropropylene (PVDF-HEP), polyethylene oxide (PEO), and the like. Polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate and polypropylene glycol diacrylate, and their co-weights. It is at least one selected from the group consisting of coalescence, and the content of the gel-forming polymer in the electrode active material layer is x [mass%] in terms of solid content, and constitutes the electrolytic solution at 25 ° C. when the viscosity of the nonaqueous solvent was set to y [mPa · s], and satisfies a ^{x 2} y ≦ 22.8. According to the electrode for a non-aqueous electrolyte secondary battery of this embodiment, excellent output characteristics and quick charging characteristics can be exhibited by reducing the internal resistance of the battery.

The detailed mechanism that exerts the above effect is unknown, but it is presumed as follows. The technical scope of the present invention is not limited to the following mechanism.

In this embodiment, the electrode active material and the gel-forming polymer are structured, and the gel-forming polymer absorbs the electrolytic solution and takes charge of ionic conduction, so that it can be used as a reaction field. Thereby, the reaction resistance at the interface can be reduced. Further, when the value of x ² y is controlled to 22.8 or less, it is possible to suppress a decrease in effective ionic conductivity in the electrode due to excessive coating of the electrode active material by the gel-forming polymer, and in addition, the viscosity is appropriate. The effective ionic conductivity in the electrode can be improved by using a non-aqueous solvent. Therefore, by controlling the content of the gel-forming polymer and the viscosity of the non-aqueous electrolyte within a predetermined range, it is considered that the internal resistance can be reduced and excellent output characteristics and quick charging characteristics can be exhibited.

Hereinafter, the above-described embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the claims and is not limited to the following embodiments. .. Hereinafter, the present invention will be described by taking a bipolar lithium ion secondary battery, which is a form of a non-aqueous electrolyte secondary battery, as an example. The dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios. In the present specification, "X to Y" indicating a range means "X or more and Y or less". Unless otherwise specified, operations and physical properties are measured under the conditions of room temperature (20 to 25 ° C.) and relative humidity of 40 to 50% RH.

In the present specification, the bipolar lithium ion secondary battery may be simply referred to as a "bipolar secondary battery", and the electrode for a bipolar lithium ion secondary battery may be simply referred to as a "bipolar electrode".

<Bipolar secondary battery>
FIG. 1 is a cross-sectional view schematically showing a bipolar secondary battery according to an embodiment of the present invention. The bipolar secondary battery 10a shown in FIG. 1 has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminated film 29 which is a battery exterior.

As shown in FIG. 1, in the power generation element 21 of the bipolar secondary battery 10a of the present embodiment, a positive electrode active material layer 13 electrically bonded to one surface of the current collector 11 is formed, and the current collector 11 has a positive electrode active material layer 13. It has a plurality of bipolar electrodes 23 having an electrically coupled negative electrode active material layer 15 formed on the opposite surface. Each bipolar electrode 23 is laminated via an electrolyte layer 17 to form a power generation element 21. At this time, the positive electrode active material layer 13 of the one bipolar electrode 23 and the negative electrode active material layer 15 of the other bipolar electrode 23 adjacent to the one bipolar electrode 23 face each other via the electrolyte layer 17. The bipolar electrodes 23 and the electrolyte layers 17 are alternately laminated. That is, the electrolyte layer 17 is sandwiched between the positive electrode active material layer 13 of the one bipolar electrode 23 and the negative electrode active material layer 15 of the other bipolar electrode 23 adjacent to the one bipolar electrode 23. ing.

The adjacent positive electrode active material layer 13, the electrolyte layer 17, and the negative electrode active material layer 15 constitute one cell cell layer 19. Therefore, it can be said that the bipolar secondary battery 10a has a configuration in which the cell cell layers 19 are laminated. Further, a seal portion (insulating layer) 31 is arranged on the outer peripheral portion of the cell cell layer 19. As a result, liquid leakage due to leakage of the electrolytic solution from the electrolyte layer 17 is prevented, adjacent current collectors 11 in the battery come into contact with each other, and the ends of the cell layer 19 in the power generation element 21 are slightly uneven. It prevents short circuits caused by the above. The positive electrode active material layer 13 is formed on only one side of the outermost layer current collector 11a on the positive electrode side located in the outermost layer of the power generation element 21. Further, the negative electrode active material layer 15 is formed on only one side of the outermost layer current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21.

Further, in the bipolar secondary battery 10a shown in FIG. 1, a positive electrode current collector plate (positive electrode tab) 25 is arranged so as to be adjacent to the outermost layer current collector 11a on the positive electrode side, and this is extended to form a battery exterior. It is derived from the laminated film 29. On the other hand, the negative electrode current collector plate (negative electrode tab) 27 is arranged so as to be adjacent to the outermost layer current collector 11b on the negative electrode side, and is similarly extended and led out from the laminated film 29.

The number of times the cell cell layer 19 is laminated is adjusted according to a desired voltage. Further, in the bipolar secondary battery 10, the number of times the single battery layer 19 is laminated may be reduced as long as sufficient output can be secured even if the thickness of the battery is made as thin as possible. Even in the bipolar secondary battery 10a, in order to prevent external impact and environmental deterioration during use, the power generation element 21 is vacuum-sealed in the laminated film 29 which is the battery exterior, and the positive electrode current collector plate 25 and the negative electrode current collector are collected. It is preferable to have a structure in which the electric plate 27 is taken out from the laminated film 29. Although the embodiment of the present invention has been described here by taking a bipolar secondary battery as an example, the type of non-aqueous electrolyte battery to which the electrode of this embodiment can be applied is not particularly limited, and a single battery is used as a power generation element. It can be applied to any conventionally known non-aqueous electrolyte secondary battery such as a so-called parallel laminated battery in which layers are connected in parallel.

FIG. 2 illustrates the overall structure of a flat (laminated) non-bipolar (internal parallel connection type) secondary battery (hereinafter, also simply referred to as “laminated secondary battery”) according to an embodiment of the present invention. It is a cross-sectional schematic diagram represented by the above.

As shown in FIG. 2, the laminated secondary battery 10b of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which the charge / discharge reaction actually proceeds is sealed inside the laminated film 29. Here, the power generation element 21 is provided on both surfaces of the positive electrode in which the positive electrode active material layers 13 are arranged on both sides of the positive electrode current collector 11', the electrolyte layer 17 composed of a separator containing an electrolytic solution, and the negative electrode current collector 12. It has a structure in which a negative electrode on which the negative electrode active material layer 15 is arranged is laminated. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 interposed therebetween. ..

As a result, the adjacent positive electrode, electrolyte layer, and negative electrode form one cell cell layer 19. Therefore, it can be said that the laminated secondary battery 10b shown in FIG. 2 has a configuration in which a plurality of single battery layers 19 are laminated and electrically connected in parallel. The positive electrode current collectors in the outermost layers located in both outermost layers of the power generation element 21 have the positive electrode active material layer 13 arranged on only one side, but active material layers may be provided on both sides. .. That is, instead of using a current collector dedicated to the outermost layer in which the active material layer is provided on only one side, a current collector having active material layers on both sides may be used as it is as the current collector in the outermost layer. Further, by reversing the arrangement of the positive electrode and the negative electrode as in FIG. 2, the negative electrode current collector of the outermost layer is located on both outermost layers of the power generation element 21, and one side of the negative electrode current collector of the outermost layer or Negative electrode active material layers may be arranged on both sides.

A positive electrode current collector plate 25 and a negative electrode current collector plate 27, which are conductive to each electrode (positive electrode and negative electrode), are attached to the positive electrode current collector 11'and the negative electrode current collector 12, respectively, and are sandwiched between the ends of the laminate film 29. It has a structure that is led out to the outside of the laminated film 29. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are attached to the positive electrode current collector 11'and the negative electrode current collector 12 of each electrode via the positive electrode terminal lead and the negative electrode terminal lead (not shown), respectively, as necessary. It may be attached by ultrasonic welding, resistance welding, or the like.

One embodiment of the present invention provides a non-aqueous electrolyte secondary battery having the electrode for the non-aqueous electrolyte secondary battery. When the non-aqueous electrolyte secondary battery has the electrode of this embodiment, excellent output characteristics and quick charging characteristics can be exhibited.

Hereinafter, the main components of the above-mentioned bipolar secondary battery will be described.

[electrode]
The electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention has a current collector and an electrode active material layer which is a non-binding body arranged on the surface of the current collector. The electrode of this embodiment may be used as a positive electrode or a negative electrode. When the electrode of this embodiment is used as the positive electrode, a known electrode can be used as the negative electrode as the negative electrode. Further, when the electrode of this embodiment is used as a negative electrode, a known electrode can be used as the positive electrode as the positive electrode.

[Current collector]
The current collector has a function of mediating the movement of electrons from one surface in contact with the positive electrode active material layer to the other surface in contact with the negative electrode active material layer. The material constituting the current collector is not particularly limited, and for example, a metal or a resin having conductivity can be adopted.

Specific examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Further, the foil may be a metal surface coated with aluminum, or a carbon-coated aluminum foil. Of these, aluminum, stainless steel, copper, and nickel are preferable from the viewpoint of electron conductivity and battery operating potential.

Further, examples of the latter resin having conductivity include a conductive polymer material or a resin in which a conductive filler is added to a non-conductive polymer material as needed. Examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, polyoxadiazole and the like. Since such a conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in terms of facilitating the manufacturing process or reducing the weight of the current collector.

Examples of the non-conductive polymer material include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), and polyimide. (PI), Polyethyleneimide (PAI), Polyethylene (PA), Polytetrafluoroethylene (PTFE), Styrene-butadiene rubber (SBR), Polyacrylonitrile (PAN), Polymethylacrylate (PMA), Polymethylmethacrylate (PMMA) , Polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), polystyrene (PS) and the like. Such non-conductive polymer materials can have excellent potential resistance or solvent resistance.

A conductive filler may be added to the above-mentioned conductive polymer material or non-conductive polymer material, if necessary. In particular, when the resin used as the base material of the current collector is composed of only a non-conductive polymer, a conductive filler is inevitably indispensable in order to impart conductivity to the resin.

The conductive filler can be used without particular limitation as long as it is a conductive substance. For example, a material having excellent conductivity, potential resistance, or lithium ion blocking property includes metals and conductive carbon. The metal is not particularly limited, but is at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb, and K, or a metal thereof. It is preferable to contain an alloy containing, or a metal oxide. Further, the conductive carbon is not particularly limited. Preferably, it is selected from the group consisting of acetylene black, vulcan (registered trademark), black pearl (registered trademark), carbon nanofiber, Ketjen black (registered trademark), carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. It contains at least one species.

The amount of the conductive filler added is not particularly limited as long as it can impart sufficient conductivity to the current collector, and is generally about 5 to 80% by mass.

The current collector may have a single-layer structure made of a single material, or may have a laminated structure in which layers made of these materials are appropriately combined. From the viewpoint of reducing the weight of the current collector, it is preferable to include a conductive resin layer made of at least a conductive resin. Further, from the viewpoint of blocking the movement of lithium ions between the cell layers, a metal layer may be provided as a part of the current collector.

[Electrode active material layer]
The electrode active material layer is a non-binding body that is arranged on the surface of the current collector and contains an electrode active material, a gel-forming polymer, and an electrolytic solution. "A non-binding body containing an electrode active material, a gel-forming polymer, and an electrolytic solution" means that the electrode active materials are not fixed to each other by a binder (also referred to as a binder). means.

The binder content in the electrode active material layer is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.5% by mass or less, based on 100% by mass of the total solid content contained in the negative electrode active material layer. It is preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

Further, in the present specification, whether or not the active material layer is a non-bonded body of the electrode active material is whether or not the active material layer collapses when the active material layer is completely impregnated in the electrolytic solution. It can be confirmed by observing. When the active material layer is composed of a binder containing an electrode active material, the shape can be maintained for one minute or more, but when the active material layer is a non-bonded body containing an electrode active material, the shape can be maintained. Shape collapse occurs in less than a minute.

As described above, in the electrode active material layer according to the present embodiment, the content x [mass%] (solid content equivalent) of the gel-forming polymer and the viscosity y [mPa · s] of the non-aqueous solvent constituting the electrolytic solution at 25 ° C. ] and satisfies ^{x 2} y ≦ 22.8. Therefore, the gel-forming polymer according to this embodiment does not bring the electrode active materials into a state in which their positions are fixed to each other. Therefore, the gel-forming polymer according to this embodiment is not included in the definition of binder.

(Positive electrode active material)
Examples of the positive electrode active material include lithium-, such as LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni-Mn-Co) O _2, and a part of these transition metals substituted with other elements. Examples thereof include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more kinds of positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. More preferably, a composite oxide containing lithium and nickel is used. More preferably, Li (Ni-Mn-Co) O ₂ and a part of these transition metals are substituted with other elements (hereinafter, also simply referred to as "NMC composite oxide"), or lithium-nickel-cobalt. -Aluminum composite oxide (hereinafter, also simply referred to as "NCA composite oxide") or the like is used. The NMC composite oxide has a layered crystal structure in which a lithium atomic layer and a transition metal (Mn, Ni, and Co are arranged in an orderly manner) atomic layer are alternately stacked via an oxygen atomic layer. Then, one Li atom is contained in each atom of the transition metal M, and the amount of Li that can be taken out is twice that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, and a high capacity can be obtained.

As described above, the NMC composite oxide also includes a composite oxide in which a part of the transition metal element is replaced with another metal element. Other elements in that case include Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, V, Cu. , Ag, Zn and the like, preferably Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, and more preferably Ti, Zr, P, Al, Mg, It is Cr, and more preferably Ti, Zr, Al, Mg, and Cr from the viewpoint of improving cycle characteristics.

NMC composite oxide, since the theoretical discharge capacity is high, preferably the general formula _{(1): Li a Ni b} Mn c Co d M x O 2 ( In the formula, a, b, c, d, x Satisfies 0.9 ≦ a ≦ 1.2, 0 <b <1, 0 ≦ c ≦ 0.5, 0 <d ≦ 0.5, 0 ≦ x ≦ 0.3, b + c + d = 1. It has a composition represented by (at least one kind of element selected from Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr). Here, a represents the atomic ratio of Li, b represents the atomic ratio of Ni, c represents the atomic ratio of Mn, d represents the atomic ratio of Co, and x represents the atomic ratio of M. Represents. From the viewpoint of cycle characteristics, it is preferable that 0.4 ≦ b ≦ 0.6 in the general formula (1). The composition of each element can be measured by, for example, inductively coupled plasma (ICP) emission spectrometry.

In general, nickel (Ni), cobalt (Co) and manganese (Mn) are known to contribute to capacitance and output characteristics from the viewpoint of improving the purity of the material and the electron conductivity. Ti and the like partially replace the transition metal in the crystal lattice. From the viewpoint of cycle characteristics, it is preferable that a part of the transition element is substituted with another metal element, and it is particularly preferable that 0 <x ≦ 0.3 in the general formula (1). The crystal structure is stabilized by solid solution of at least one selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr and Cr. As a result, it is considered that the capacity of the battery can be prevented from decreasing even if charging and discharging are repeated, and excellent cycle characteristics can be realized.

As a more preferable embodiment, in the general formula (1), b, c and d are 0.44 ≦ b ≦ 0.51, 0.27 ≦ c ≦ 0.31 and 0.19 ≦ d ≦ 0.26. Is preferable from the viewpoint of improving the balance between capacity and life characteristics. For example, LiNi _0.5 Mn _0.3 Co _0.2 O ₂ includes LiCo O ₂ , LiMn ₂ O ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O _2, etc., which have been proven in general consumer batteries. Compared with, the capacity per unit mass is large. This has the advantage that the energy density can be improved and a compact and high-capacity battery can be manufactured, which is preferable from the viewpoint of cruising distance.

Further, as a more preferable embodiment, LiNi _0.8 Co _0.1 Al _0.1 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ are preferable from the viewpoint of larger capacity.

The average particle size of the positive electrode active material is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of increasing the output. In the present specification, the average particle size is measured by a particle size distribution measuring device of a laser diffraction / scattering method.

(Negative electrode active material)
Examples of the negative electrode active material include carbon materials such as graphite (graphite), soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials (tin, silicon), and silicon. Examples thereof include alloy-based negative electrode materials (for example, Si ₆₀ Sn ₁₀ Ti ₃₀ ) and lithium alloy-based negative electrode materials (for example, lithium-tin alloy, lithium-silicon alloy, lithium-aluminum alloy, lithium-aluminum-manganese alloy, etc.). .. In some cases, two or more kinds of negative electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a silicon-containing alloy-based negative electrode material, a carbon material, a lithium-transition metal composite oxide, and a lithium alloy-based negative electrode material are preferably used as the negative electrode active material. Needless to say, a negative electrode active material other than the above may be used.

The average particle size of the negative electrode active material is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of increasing the output.

(Gel-forming polymer)
The gel-forming polymer is an ionic conductive polymer and can form a structure together with the electrode active material to play a role of ionic conduction. Gel-forming polymers include polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVdF-HEP), polymethylmethacrylate (PMMA), It is at least one selected from the group consisting of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, polypropylene glycol diacrylate and polymethyl methacrylate, and copolymers thereof.

From the viewpoint of further enhancing the output characteristics, the gel-forming polymer is preferably polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene ( It is selected from PVdF-HEP) and polymethylmethacrylate (PMMA), more preferably polyvinylidene fluoride-hexafluoropropylene (PVdF-HEP).

(Electrolytic solution)
The electrolytic solution has a function as a carrier of lithium ions. The electrolytic solution has a form in which a lithium salt is dissolved in a non-aqueous solvent.

Non-aqueous solvent, can be in accordance with the amount of gel forming polymer used is appropriately selected non-aqueous solvent satisfying x 2 ^y ≦ 22.8. For the viscosity of the non-aqueous solvent at 25 ° C., a value measured using an SVM3001 viscometer (manufactured by Antonio par) is adopted.

Non-aqueous solvents include, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), methyl formate (MF). ), 4-Methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), propylene carbonate (PC), butylene carbonate (BC), dimethyl sulfoxide (DMSO). ), And γ-butylollactone (GBL) and the like. Among them, the non-aqueous solvent is preferably a chain carbonate, more preferably diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) from the viewpoint of further improving the quick charging property and the output property. ) Is selected from the group consisting of at least one, and more preferably selected from ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

The viscosity of the non-aqueous solvent is preferably 1.99 mPa · s or less, more preferably 1.75 mPa · s or less at 25 ° C., and further preferably 1.75 mPa · s or less, from the viewpoint that the quick charging characteristics and the output characteristics can be further improved. Is 0.75 mPa · s or less, and particularly preferably 0.65 mPa · s or less.

Lithium salts include Li (FSO ₂ ) ₂ N (lithium bis (fluorosulfonyl) imide; LiFSI), Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like can be mentioned. Among them, lithium salt, from the viewpoint of battery output and charge-discharge cycle characteristics, it is preferably Li _{(FSO 2)} 2 N.

The concentration of the lithium salt in the electrolytic solution is preferably 0.1 to 3.0 mol / L, more preferably 0.8 to 2.2 mol / L.

The electrolytic solution may further contain additives other than the above-mentioned components. Specific examples of such compounds include, for example, ethylene carbonate, vinylene carbonate, methylvinylene carbonate, dimethylvinylene carbonate, phenylvinylene carbonate, diphenylvinylene carbonate, ethylvinylene carbonate, diethylvinylene carbonate, vinylethylene carbonate, 1,2-. Divinylethylene carbonate, 1-methyl-1-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-1-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, vinylvinylene carbonate, allylethylene Carbonate, vinyloxymethylethylene carbonate, allyloxymethylethylene carbonate, acrylicoxymethylethylene carbonate, methacryloxymethylethylene carbonate, ethynylethylene carbonate, propargylethylene carbonate, ethynyloxymethylethylene carbonate, propargyloxyethylene carbonate, methyleneethylene carbonate, 1 , 1-Dimethyl-2-methyleneethylene carbonate and the like. Only one of these additives may be used alone, or two or more of these additives may be used in combination. In addition, the amount of the additive used in the electrolytic solution can be adjusted as appropriate. When the additive is used in the electrolytic solution, the viscosity of the non-aqueous solvent is the viscosity of the non-aqueous solvent itself that does not contain the additive.

(Conductive aid)
The electrode active material layer can further contain a conductive additive.

The conductive auxiliary agent has a function of forming an electron conduction path (conductive path) in the electrode active material layer. When such an electron conduction path is formed in the electrode active material layer, the internal resistance of the battery is reduced, which can contribute to the improvement of the output characteristics at a high rate. In particular, at least a part of the conductive auxiliary agent forms a conductive passage that electrically connects the two main surfaces of the electrode active material layer (in the present embodiment, it contacts the electrolyte layer side of the electrode active material layer). It is preferable to form a conductive passage that electrically connects the first main surface to the second main surface in contact with the current collector side). By having such a form, the electron transfer resistance in the thickness direction in the electrode active material layer is further reduced, so that the output characteristics at a high rate of the battery can be further improved. At least a part of the conductive auxiliary agent forms a conductive passage that electrically connects the two main surfaces of the electrode active material layer (in the present embodiment, it contacts the electrolyte layer side of the electrode active material layer). Whether or not a conductive passage is formed that electrically connects the first main surface to the second main surface in contact with the current collector side) is determined by using an SEM or an optical microscope to determine the cross section of the electrode active material layer. It can be confirmed by observing.

From the viewpoint of reliably forming such a conductive passage, the conductive auxiliary agent is preferably a conductive fiber having a fibrous form. Specifically, carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers in which a metal having good conductivity or graphite is uniformly dispersed in synthetic fibers, and a metal such as stainless steel are used as fibers. Examples thereof include carbonized metal fibers, conductive fibers in which the surface of organic fibers is coated with metal, and conductive fibers in which the surface of organic fibers is coated with a resin containing a conductive substance. Of these, carbon fiber is preferable because it has excellent conductivity and is lightweight.

However, of course, a conductive auxiliary agent that does not have a fibrous form may be used. For example, a conductive auxiliary agent having a particulate (for example, spherical) morphology can be used. When the conductive auxiliary agent is in the form of particles, the shape of the particles is not particularly limited, and may be any shape such as powder, sphere, plate, columnar, indefinite shape, flaky shape, and spindle shape. The average particle size (primary particle size) when the conductive auxiliary agent is in the form of particles is not particularly limited, but is preferably about 0.01 to 10 μm from the viewpoint of the electrical characteristics of the battery. In addition, in this specification, a "particle diameter" means the maximum distance L among the distances between arbitrary two points on the contour line of a conductive auxiliary agent. The value of the "average particle size" is the average value of the particle size of the particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

Conductive aids having a particulate (eg, spherical) morphology include, for example, metals such as aluminum, stainless steel (SUS), silver, gold, copper, titanium, alloys or metal oxides containing these metals; graphite, Examples thereof include carbon such as carbon nanotubes (CNT) and carbon black (specifically, acetylene black, Ketjen black (registered trademark), furnace black, channel black, thermal lamp black, etc.), but are not limited thereto. Further, a particulate ceramic material or a resin material coated with the above metal material by plating or the like can also be used as a conductive auxiliary agent. Among these conductive auxiliaries, from the viewpoint of electrical stability, it is preferable to contain at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon, and aluminum, stainless steel. It is more preferable to contain at least one selected from the group consisting of silver, gold, and carbon, and it is further preferable to contain at least one carbon. Only one kind of these conductive auxiliaries may be used alone, or two or more kinds thereof may be used in combination.

The content of the conductive auxiliary agent in the electrode active material layer is preferably 1 to 8% by mass with respect to 100% by mass of the total solid content of the electrode active material layer (the total solid content of all the members). More preferably, it is 2 to 4% by mass. When the content of the conductive auxiliary agent is in the above range, there is an advantage that the electron conduction path can be satisfactorily formed in the electrode active material layer and the decrease in the energy density of the battery can be suppressed.

(Structure consisting of electrode active material, gel-forming polymer and conductive additive)
In one embodiment of the invention, the electrode active material layer comprises a structure consisting of an electrode active material, a gel-forming polymer and a conductive additive. As a result, the electrode active material can be in good contact with the conductive auxiliary agent, and the electrode active material is in an active state, so that the electron conductivity can be further improved. Further, by structuring the conductive auxiliary agent around the electrode active material, excellent conductivity can be ensured, so that the output and the capacity can be improved. Further, by structuring the conductive auxiliary agent around the electrode active material, percolation in the pores is formed. Therefore, the effective ionic conductivity can be further improved. In addition, by forming such a structure, the electrode active material layer can be made into a self-supporting film, and the strength of the electrode can be further increased.

The content of the electrode active material (in terms of solid content) in the electrode active material layer is preferably 60 to 95% by mass, and more preferably 80 to 95% by mass from the viewpoint of output characteristics.

The content of the gel forming polymer of the electrode active material layer is not particularly limited, can be appropriately adjusted so as to satisfy the x ^{2 y} ≦ 22.8 to suit the viscosity of the nonaqueous solvent used. The content of the gel-forming polymer (in terms of solid content) is preferably 3 to 5% by mass from the viewpoint of further improving the quick charging characteristics and the output characteristics.

The thickness of the electrode active material layer is preferably 10 to 1500 μm for the positive electrode active material layer. The thickness of the negative electrode active material layer is preferably 100 to 1500 μm. When the thickness of the electrode active material layer is at least the above-mentioned lower limit value, the energy density of the battery can be sufficiently increased. On the other hand, if the thickness of the electrode active material layer is not more than the above-mentioned upper limit value, the structure of the electrode active material layer can be easily maintained.

The porosity of the electrode active material layer is preferably 35 to 50%, more preferably 35 to 45% for the positive electrode active material layer. The porosity of the negative electrode active material layer is preferably 30 to 60%, more preferably 35 to 50%. If the porosity of the electrode active material layer is equal to or higher than the above-mentioned lower limit value, it is necessary to increase the pressing pressure when pressing the coating film after applying the electrode active material slurry at the time of forming the electrode active material layer. Absent. As a result, the electrode active material layer having a desired thickness and area can be suitably formed. On the other hand, if the void ratio of the electrode active material layer is equal to or less than the above-mentioned upper limit value, sufficient contact between the electron conductive materials (conductive auxiliary agent, electrode active material, etc.) in the electrode active material layer should be maintained. It is possible to prevent an increase in electron transfer resistance. As a result, the charge / discharge reaction can proceed uniformly over the entire electrode active material layer (particularly in the thickness direction). The porosity of the electrode active material layer is determined by measuring the weight per unit area of the electrode active material layer, measuring the thickness of the electrode active material layer using a micrometer, and measuring the porosity from the density of each material. The volume can be calculated and obtained.

The density of the electrode active material layer is preferably 2.10 to 3.00 g / cm ³ , more preferably 2.15 to 2.85 g / cm ³ , and further preferably 2 for the positive electrode active material layer. It is .20 to 2.80 g / cm ³ . The density of the negative electrode active material layer is preferably 0.60 to 1.30 g / cm ³ , more preferably 0.70 to 1.20 g / cm ³ , and even more preferably 0.80 to 1. It is 10 g / cm ³ . When the density of the electrode active material layer is at least the above-mentioned lower limit value, a battery having a sufficient energy density can be obtained. On the other hand, when the density of the electrode active material layer is not more than the above-mentioned upper limit value, a sufficient electrolytic solution is secured to fill the voids, and an increase in ion transfer resistance in the electrode active material layer can be prevented. In this specification, the density of the electrode active material layer shall be measured by the following method.

The density of the electrode active material layer is calculated according to the following formula.
Electrode active material layer density (g / cm ³ ) = solid material weight (g) ÷ electrode active material layer volume (cm ³ ).

The weight of the solid material is calculated by adding only the weight of the solid material to the weight of each material in the electrode active material layer. The volume of the electrode active material layer is calculated from the thickness of the electrode and the coating area.

[Content of gel-forming polymer and viscosity of non-aqueous solvent]
In the electrode for a non-aqueous electrolyte secondary battery according to this embodiment, the content of the gel-forming polymer is x [mass%] in terms of solid content, and the viscosity of the non-aqueous solvent constituting the electrolytic solution at 25 ° C. is y [mPa. · S], it is characterized in that x ² y ≦ 22.8 is satisfied. The present inventors have found that there is an appropriate range between the content of the gel-forming polymer in the electrode active material layer and the viscosity of the non-aqueous solvent constituting the electrolytic solution, and the findings are based on the above relational expression. It was quantified.

In this embodiment, the electrode active material and the gel-forming polymer are structured, and the gel-forming polymer absorbs the electrolytic solution and takes charge of ionic conduction, so that it can be used as a reaction field. Thereby, the reaction resistance at the interface can be reduced. Further, by controlling the value of x ² y to 22.8 or less, it is possible to suppress a decrease in ionic conductivity due to excessive coating of the electrode active material by the gel-forming polymer, and in addition, non-aqueous with an appropriate viscosity. Ion conductivity can be improved by using a solvent. Therefore, by controlling the content of the gel-forming polymer and the viscosity of the non-aqueous electrolyte within a predetermined range, it is considered that the internal resistance can be reduced and excellent output characteristics and quick charging characteristics can be exhibited.

The above x and y preferably satisfy x ² y ≦ 17.9, more preferably x ² y <6.8, and particularly preferably x, from the viewpoint that the quick charging characteristics and the output characteristics can be further improved. ² y ≦ 5.9 is satisfied. The lower limit of x ² y is not particularly limited as long as it exceeds 0, but is, for example, 2.8 ≦ x ² y, preferably 5.0 ≦ x ² y.

The method for manufacturing the electrode for the non-aqueous electrolyte secondary battery according to this embodiment will be described in the method for manufacturing the non-aqueous electrolyte secondary battery described later.

<Components other than electrodes>
Although the electrodes have been described in detail among the components of the bipolar secondary battery according to the preferred embodiment of the present invention, conventionally known findings can be appropriately referred to for other components.

[Electrolyte layer]
The electrolyte layer according to this embodiment is preferably arranged between the electrodes and has a structure in which the separator is impregnated with the electrolytic solution.

As the electrolytic solution constituting the electrolyte layer, the one described in the above section (electrolyte solution) is used. From the viewpoint of exhibiting the effects of the present invention, it is preferable to use the same non-aqueous solvent that constitutes the electrolytic solution as the non-aqueous solvent that constitutes the electrolytic solution.

The separator constituting the electrolyte layer has a function of holding the electrolyte and ensuring lithium ion conductivity between the positive electrode and the negative electrode, and a function as a partition wall between the positive electrode and the negative electrode.

Examples of the form of the separator include a porous sheet separator made of a polymer or fiber that absorbs and retains the electrolytic solution, a non-woven fabric separator, and the like.

As the separator of the porous sheet made of polymer or fiber, for example, microporous (microporous membrane) can be used. Specific forms of the porous sheet made of the polymer or fiber include, for example, a polyolefin such as polyethylene (PE) and polypropylene (PP); a laminate in which a plurality of these are laminated (for example, three layers of PP / PE / PP). Examples thereof include a microporous (microporous film) separator made of a laminated body having a structure), a hydrocarbon resin such as polyethylene, aramid, polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), and glass fiber.

The thickness of the microporous (microporous membrane) separator cannot be uniquely specified because it differs depending on the intended use. To give an example, in applications such as a secondary battery for driving a motor such as an electric vehicle (EV), a hybrid electric vehicle (HEV), and a fuel cell vehicle (FCV), the length is 4 to 60 μm in a single layer or a multilayer. Is desirable. It is desirable that the fine pore size of the microporous (microporous membrane) separator is 1 μm or less (usually, the pore size is about several tens of nm) at the maximum.

As the non-woven fabric separator, conventionally known ones such as cotton, rayon, acetate, nylon, polyester; polyolefin such as PP and PE; polyimide and aramid are used alone or in combination. Further, the bulk density of the non-woven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. Further, the thickness of the non-woven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.

Further, the separator is preferably a separator in which a heat-resistant insulating layer is laminated on a porous substrate (separator with a heat-resistant insulating layer). The heat-resistant insulating layer is a ceramic layer containing inorganic particles and a binder. As the separator with a heat-resistant insulating layer, a separator having a melting point or a thermal softening point of 150 ° C. or higher, preferably 200 ° C. or higher, having high heat resistance is used. By having the heat-resistant insulating layer, the internal stress of the separator, which increases when the temperature rises, is relaxed, so that the effect of suppressing heat shrinkage can be obtained. As a result, it is possible to prevent the induction of a short circuit between the electrodes of the battery, so that the battery configuration is less likely to cause performance deterioration due to a temperature rise. Further, by having the heat-resistant insulating layer, the mechanical strength of the separator with the heat-resistant insulating layer is improved, and the film breakage of the separator is less likely to occur. Further, due to the heat shrinkage suppressing effect and high mechanical strength, the separator is less likely to curl in the battery manufacturing process.

The inorganic particles in the heat-resistant insulating layer contribute to the mechanical strength of the heat-resistant insulating layer and the effect of suppressing heat shrinkage. The material used as the inorganic particles is not particularly limited. Examples include silicon, aluminum, zirconium, titanium oxides (SiO ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ ), hydroxides, and nitrides, and composites thereof. These inorganic particles may be derived from mineral resources such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, or may be artificially produced. Further, only one of these inorganic particles may be used alone, or two or more of these inorganic particles may be used in combination. Of these, from the viewpoint of cost, it is preferable to use silica (SiO ₂ ) or alumina (Al ₂ O ₃ ), and it is more preferable to use alumina (Al ₂ O ₃ ).

The basis weight of the heat-resistant particles is not particularly limited, but is preferably 5 to 15 g / m ² . Within this range, sufficient ionic conductivity can be obtained, and heat resistance is preferably maintained.

The binder in the heat-resistant insulating layer has a role of adhering the inorganic particles to each other and the inorganic particles and the resin porous base layer. The binder stably forms the heat-resistant insulating layer and prevents peeling between the porous substrate layer and the heat-resistant insulating layer.

The binder used for the heat-resistant insulating layer is not particularly limited, and is, for example, carboxymethyl cellulose (CMC), polyacrylonitrile, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), isoprene rubber. , Butadiene rubber, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), methyl acrylate and the like can be used as binders. Of these, carboxymethyl cellulose (CMC), methyl acrylate, or polyvinylidene fluoride (PVDF) is preferably used. Only one of these compounds may be used alone, or two or more of these compounds may be used in combination.

The content of the binder in the heat-resistant insulating layer is preferably 2 to 20% by mass with respect to 100% by mass of the heat-resistant insulating layer. When the binder content is 2% by mass or more, the peel strength between the heat-resistant insulating layer and the porous substrate layer can be increased, and the vibration resistance of the separator can be improved. On the other hand, when the binder content is 20% by mass or less, the gaps between the inorganic particles are appropriately maintained, so that sufficient lithium ion conductivity can be ensured.

The heat shrinkage of the separator with a heat-resistant insulating layer is preferably 10% or less for both MD and TD after holding for 1 hour under the conditions of 150 ° C. and ² gf / cm ² . By using such a material having high heat resistance, it is possible to effectively prevent the separator from shrinking even when the heat generation amount becomes high and the battery internal temperature reaches 150 ° C. As a result, it is possible to prevent the induction of a short circuit between the electrodes of the battery, so that the battery configuration is less likely to cause performance deterioration due to a temperature rise.

[Positive current collector plate and negative electrode current collector plate]
The material constituting the current collector plates (25, 27) is not particularly limited, and a known highly conductive material conventionally used as a current collector plate for a lithium ion secondary battery can be used. As the constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. The same material may be used or different materials may be used for the positive electrode current collector plate 25 and the negative electrode current collector plate 27.

[Positive lead and negative electrode lead]
Further, although not shown, the current collector 11 and the current collector plates (25, 27) may be electrically connected via a positive electrode lead or a negative electrode lead. As the constituent materials of the positive electrode and the negative electrode leads, materials used in known lithium ion secondary batteries can be similarly adopted. It should be noted that the part taken out from the exterior is heat-shrinkable with heat-resistant insulation so that it does not come into contact with peripheral devices or wiring and cause electric leakage and affect the product (for example, automobile parts, especially electronic devices). It is preferable to cover with a tube or the like.

[Seal part]
The seal portion (insulating layer) 31 has a function of preventing contact between current collectors and a short circuit at the end of the cell cell layer. As the material constituting the sealing portion, if it has insulating property, sealing property against falling off of solid electrolyte, sealing property against moisture permeation from the outside (sealing property), heat resistance under battery operating temperature, etc. Good. For example, acrylic resin, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber (ethylene-propylene-diene rubber: EPDM), and the like can be used. Further, an isocyanate-based adhesive, an acrylic resin-based adhesive, a cyanoacrylate-based adhesive, or the like may be used, or a hot melt adhesive (urethane resin, polyamide resin, polyolefin resin) or the like may be used. Among them, polyethylene resin and polypropylene resin are preferably used as constituent materials of the insulating layer from the viewpoints of corrosion resistance, chemical resistance, ease of production (film formation), economy, etc., and mainly non-crystalline polypropylene resin. It is preferable to use a resin obtained by copolymerizing ethylene, propylene, and butene as components.

[Battery exterior]
As the battery exterior, a known metal can case can be used, or a bag-shaped case using a laminated film 29 containing aluminum, which can cover the power generation element as shown in FIG. 1, can be used. As the laminate film, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used, but the laminate film is not limited thereto. A laminated film is desirable from the viewpoint of high output and excellent cooling performance, and can be suitably used for batteries for large equipment for EVs and HEVs. Further, the exterior body is more preferably an aluminate laminate because the group pressure applied to the power generation element from the outside can be easily adjusted and the thickness of the electrolytic solution layer can be easily adjusted.

The bipolar secondary battery of this embodiment can exhibit excellent output characteristics. Therefore, the bipolar secondary battery of this embodiment is suitably used as a power source for driving EVs and HEVs.

[Manufacturing method of non-aqueous electrolyte secondary battery]
The method for producing the non-aqueous electrolyte secondary battery according to the present embodiment is not particularly limited, but a coating film is formed by preparing an electrode active material slurry and applying the electrode active material slurry to the surface of the current collector. A method involving the above is preferred.

Hereinafter, an example of a preferable manufacturing method of the non-aqueous electrolyte secondary battery according to this embodiment will be described.

First, the above-mentioned electrode active material, gel-forming polymer and conductive auxiliary agent are mixed with a solvent to prepare an electrode active material slurry.

The solvent is not particularly limited, and N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide, cyclohexane, hexane, water and the like can be used.

The method for preparing the electrode active material slurry by mixing the electrode active material, the gel-forming polymer, the conductive auxiliary agent and the solvent is not particularly limited, and conventionally known findings such as the order of adding members and the mixing method are appropriately referred to. ..

The concentration of the electrode active material slurry is not particularly limited. However, from the viewpoint of facilitating the application of the slurry described later, the concentration of the total solid content with respect to 100% by mass of the electrode active material slurry is preferably 35 to 75% by mass, and more preferably 40 to 70% by mass. When the concentration is within the above range, an electrode active material layer having a sufficient thickness can be easily formed by coating.

Next, the electrode active material slurry is applied onto the current collector and dried. After coating, pressing may be performed if necessary. As described above, by mixing the electrode active material, the gel-forming polymer, and the conductive auxiliary agent at the time of preparing the electrode active material slurry, the electrode active having a structure composed of the electrode active material, the gel-forming polymer, and the conductive auxiliary agent. A material layer can be formed.

The method for applying the electrode active material slurry to the current collector is not particularly limited, and examples thereof include a screen printing method, a spray coating method, an electrostatic spray coating method, an inkjet method, and a doctor blade method.

The coating thickness of the electrode active material slurry is appropriately set in consideration of the thickness of the electrode active material layer to be formed. The coating thickness of the electrode active material slurry is preferably 200 to 2000 μm, and more preferably 400 to 1000 μm.

The drying method after applying the electrode active material slurry on the current collector is not particularly limited, and at least a part of the solvent may be removed. Examples of the drying method include heating. The drying conditions (drying time, drying temperature, etc.) can be appropriately set according to the volatilization rate of the solvent contained in the electrode active material slurry to be applied, the coating amount of the electrode active material slurry, and the like.

When pressing is performed, the pressing means is not particularly limited, and for example, a calendar roll, a flat plate press, or the like can be used.

In this way, an electrode precursor (positive electrode precursor or negative electrode precursor) can be obtained.

After producing the electrode precursor as described above, the electrode precursor and the separator are laminated to produce a power generation element. The method for producing the power generation element is not particularly limited, and conventionally known findings are appropriately referred to. As an example, the positive electrode precursor and the negative electrode precursor are laminated so as to face each other with the separator interposed therebetween to prepare a cell cell layer. A power generation element can be obtained by laminating the cell cell layers to a desired number.

The positive electrode tab and the negative electrode tab are joined to the obtained power generation element by welding. If necessary, it is desirable to remove excess tabs and the like by trimming after welding. The bonding method is not particularly limited, but the ultrasonic welding machine does not generate heat (heating) at the time of bonding and can be bonded in an extremely short time. Therefore, the electrode active material layer (negative electrode active material) by heat is used. It is excellent in that it can prevent deterioration of the layer and the positive electrode active material layer). At this time, the positive electrode tab and the negative electrode tab can be arranged so as to face (oppose) on the same side (same extraction side). As a result, the positive electrode tabs of each positive electrode can be bundled into one and taken out from the exterior body as one positive electrode current collector plate. Similarly, the negative electrode tabs of each negative electrode can be bundled into one and taken out from the exterior body as one negative electrode current collector plate. Further, the positive electrode current collector plate (positive electrode current collector tab) and the negative electrode current collector plate (negative electrode current collector tab) may be arranged so as to be opposite sides (different extraction sides).

The obtained power generation element is covered with an exterior body. The method of covering the power generation element with the exterior body is not limited, and conventionally known findings are appropriately referred to. As an example, a laminated film that uses a power generation element for the battery exterior can be used so that the positive electrode current collector plate (positive electrode current collector tab) and the negative electrode current collector plate (negative electrode current collector tab) can be taken out of the battery exterior from above and below. And sandwich it.

Next, three sides of the outer peripheral portions (sealing portions) of the upper and lower laminated films are thermocompression bonded to seal them. A three-sided seal is obtained by thermocompression-bonding three sides of the outer peripheral portion to seal the outer peripheral portion. At this time, it is preferable to seal the heat-sealed portion on the side where the positive electrode current collecting plate (positive electrode current collecting tab) and the negative electrode current collecting plate (negative electrode current collecting tab) are taken out. This is because if these positive electrode current collector plates and negative electrode current collector plates are in the openings during subsequent liquid injection, the electrolytic solution may scatter during liquid injection.

In the above description, the battery having a laminated structure has been described, but the battery is not limited to the laminated type, and various shapes such as a square type, a paper type, a cylindrical type, and a coin type can be adopted as the battery configuration. it can.

Next, the electrolytic solution is injected into the inside of the three-sided sealer through the opening on the remaining one side of the three-sided sealer by the liquid injection device. As a result, an electrolyte layer in which the separator is impregnated with an electrolyte is formed. At this time, the three-sided sealant may be housed in a vacuum box connected to a vacuum pump so that the electrolyte can impregnate the laminate inside the three-sided sealant, particularly the separator and the electrode active material layer, as soon as possible. preferable. Further, it is desirable to perform injection in a state where the pressure is reduced and the inside is in a high vacuum state. After the injection, the three-sided seal is taken out from the vacuum box, and the remaining one side of the three-sided seal is temporarily sealed. In this way, it is possible to obtain a laminated type (laminated structure) non-aqueous electrolyte secondary battery in which a single battery layer in which a positive electrode and a negative electrode are laminated so as to face each other via a separator is laminated.

[Cell size]
FIG. 3 is a perspective view showing the appearance of a flat lithium ion secondary battery, which is a typical embodiment of the secondary battery.

As shown in FIG. 3, the flat lithium ion secondary battery 50 has a rectangular flat shape, and positive electrode tabs 58 and negative electrode tabs 59 for extracting electric power are pulled out from both side portions thereof. There is. The power generation element 57 is wrapped by a battery exterior (laminate film 52) of the lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element 57 pulls out the positive electrode tab 58 and the negative electrode tab 59 to the outside. It is sealed in a closed state. Here, the power generation element 57 corresponds to the power generation element 21 of the bipolar secondary battery 10a shown in FIG. 1 or the laminated secondary battery 10b shown in FIG. 2 described above. The power generation element 57 is formed by stacking a plurality of bipolar electrodes 23 via an electrolyte layer 17.

The lithium ion secondary battery is not limited to a laminated flat battery. The wound lithium-ion secondary battery may have a cylindrical shape, or may be formed by deforming such a cylindrical shape into a rectangular flat shape. There are no particular restrictions. The cylindrical shape is not particularly limited, for example, a laminated film may be used for the exterior body, or a conventional cylindrical can (metal can) may be used. Preferably, the power generation element is exteriorized with an aluminum laminate film. By this form, weight reduction can be achieved.

Further, the removal of the tabs (58, 59) shown in FIG. 3 is not particularly limited. The positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of each and taken out from each side, as shown in FIG. It is not limited to. Further, in the winding type lithium ion battery, the terminal may be formed by using, for example, a cylindrical can (metal can) instead of the tab.

In a general electric vehicle, the battery storage space is about 170 L. Since the cell and auxiliary equipment such as charge / discharge control equipment are stored in this space, the storage space efficiency of the normal cell is about 50%. The loading efficiency of cells in this space is a factor that controls the cruising range of electric vehicles. If the size of the single cell becomes small, the loading efficiency is impaired, so that the cruising range cannot be secured.

Therefore, in the present invention, it is preferable that the battery structure in which the power generation element is covered with the exterior body is large. Specifically, the length of the short side of the laminated cell battery is preferably 100 mm or more. Such large batteries can be used in vehicle applications. Here, the length of the short side of the laminated cell battery refers to the side having the shortest side. The upper limit of the length of the short side is not particularly limited, but is usually 400 mm or less.

[Volume energy density and rated discharge capacity]
In a general electric vehicle, how to lengthen the mileage (cruising distance) by one charge is an important development goal. Considering these points, the volumetric energy density of the battery is preferably 157 Wh / L or more, and the rated capacity is preferably 20 Wh or more.

Further, from the viewpoint of a large-sized battery, which is different from the viewpoint of the physical size of the electrode, it is possible to specify the size of the battery from the viewpoint of the battery area and the battery capacity. For example, in the case of a flat laminated laminated battery, the value of the ratio of the battery area (projected area of the battery including the battery exterior) to the rated capacity is 5 cm ² / Ah or more, and the rated capacity is 3 Ah or more. It is preferable that the present invention is applied to a certain battery. Further, the aspect ratio of the rectangular electrode is preferably 1 to 3, more preferably 1 to 2. The aspect ratio of the electrode is defined as the aspect ratio of the rectangular positive electrode active material layer. By setting the aspect ratio within such a range, there is an advantage that both vehicle required performance and mounting space can be achieved.

[Battery set]
An assembled battery is formed by connecting a plurality of batteries. More specifically, it is composed of serialization, parallelization, or both by using at least two or more. By serializing and parallelizing, the capacitance and voltage can be adjusted freely.

It is also possible to connect a plurality of batteries in series or in parallel to form a small assembled battery that can be attached / detached. Then, by connecting a plurality of these detachable small assembled batteries in series or in parallel, a large capacity and a large capacity suitable for a vehicle driving power source or an auxiliary power source that require a high volume energy density and a high volume output density. It is also possible to form an assembled battery having an output. How many batteries are connected to make an assembled battery, and how many stages of small assembled batteries are stacked to make a large-capacity assembled battery depends on the battery capacity of the vehicle (electric vehicle) to be installed. It may be decided according to the output.

[Transport equipment]
The non-aqueous electrolyte secondary battery of this embodiment maintains the discharge capacity even after long-term use and has good cycle characteristics. In addition, the volumetric energy density is high. In vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles, higher capacity and larger size are required and longer life is required compared to electric and portable electronic device applications. .. In addition, it is required to support quick charging. Therefore, the non-aqueous electrolyte secondary battery can be mounted on a transportation device. In particular, the non-aqueous electrolyte secondary battery can be suitably used as a power source for a vehicle, for example, a vehicle drive power source or an auxiliary power source. Therefore, one embodiment of the present invention provides a transportation device equipped with the above-mentioned non-aqueous electrolyte secondary battery.

Specifically, a battery or an assembled battery formed by combining a plurality of batteries can be mounted on the vehicle. In the present invention, since a long-life battery having excellent long-term reliability and output characteristics can be configured, a plug-in hybrid electric vehicle having a long EV mileage and an electric vehicle having a long one-charge mileage can be configured by mounting such a battery. .. For example, in the case of automobiles, hybrid cars, fuel cell cars, electric cars (all are four-wheeled cars (passenger cars, trucks, commercial cars such as buses, light cars, etc.)) This is because it becomes a highly reliable automobile with a long life by using it for two-wheeled vehicles (including motorcycles) and three-wheeled vehicles. However, the application is not limited to automobiles, and can be applied to various power sources of other vehicles, for example, moving objects such as trains, and power supplies for mounting such as uninterruptible power supplies. It is also possible to use it as.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Manufacturing example]
<Preparation of negative electrode precursor>
Si ₆₀ Sn ₁₀ Ti ₃₀ (average particle size: 5.7 μm) as a negative electrode active material and fibrous carbon B (carbon nanotube, fiber diameter: 150 nm, fiber length: 10 μm, specific surface area: 13 m ² ) as a conductive auxiliary agent. / G), polyimide, and N-methyl-2-pyrrolidone as a solvent are mixed so as to have a mass ratio of 85: 5: 10: 90 (mass ratio), respectively, and the planetary stirring type mixing and kneading device "Awatori Rentaro" (ARE-310, manufactured by Shinky Co., Ltd.) was mixed at 2000 rpm for 6 minutes to prepare a negative electrode slurry. The negative electrode slurry was uniformly applied onto the Cu foil placed on the smoothing board using a doctor blade so that the thickness of the negative electrode active material layer was 25 μm. Then, it was dried on a hot plate heated to 80 ° C. for 2 hours to obtain a negative electrode precursor having a negative electrode active material mass (a amount of the negative electrode active material) of 5.4 mg / cm ² . The porosity of the negative electrode active material layer was 38%.

[Example 1]
<Preparation of positive electrode precursor>
LiNi _0.8 Mn _0.1 Co _0.1 O ₂ (average particle size: 9 μm) as a positive electrode active material, graphite (KS6, manufactured by TIMCAL) and furnace black (Super-P, TIMCAL) as a conductive auxiliary agent. ,, Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a gel-forming polymer (Kyner Flex 2501-10, manufactured by Archema), and N-methyl-2-pyrrolidone as a solvent, respectively 95: 1. Mix in a ratio of 1: 3: 60 (mass ratio), mix at 2000 rpm for 6 minutes using a planetary stirring type mixing and kneading device "Awatori Rentaro" (ARE-310, manufactured by Shinky Co., Ltd.), and positive electrode. A slurry was prepared. The positive electrode slurry was uniformly applied onto the Al foil placed on the smoothing board using a doctor blade so that the thickness of the positive electrode active material layer was 90 μm. Then, it was dried on a hot plate heated to 80 ° C. for 2 hours to obtain a positive electrode precursor having a mass of positive electrode active material (amount of the positive electrode active material) of 30 mg / cm ² . The porosity of the positive electrode active material layer was 38%.

<Making lithium-ion batteries>
12cm ² The obtained positive electrode precursor was cut negative electrode precursor such that 12.4 cm ^2. In the positive electrode precursor, an aluminum foil with an Al terminal was cut and laminated on the current collecting foil side of the positive electrode precursor. In the negative electrode precursor, a copper foil with a Ni terminal was laminated on the current collecting foil side of the cut negative electrode precursor. A separator (manufactured by Cellguard, manufactured by Cellguard (registered trademark) 3501 PP) was inserted into the electrode side of the positive electrode precursor and the negative electrode precursor to form a laminated body. This laminate is sandwiched between heat-sealing aluminum laminate films, and Li (FSO ₂ ) ₂ N (lithium bis) is mixed with dimethyl carbonate (DMC) (volume ratio 3: 7) in which ethylene carbonate (EC) is dissolved as a non-aqueous solvent. A non-aqueous electrolytic solution obtained by dissolving 2 mol / L of (fluorosulfonyl) imide; LiFSI was injected and then vacuum-sealed. In this way, a pouch-type lithium ion battery in which the positive electrode and the negative electrode are laminated so as to face each other via a separator is produced.

[Example 2]
A lithium ion battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to ethyl methyl carbonate (EMC) in the production of the lithium ion battery.

[Example 3]
A lithium ion battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to diethyl carbonate (DEC) in the production of the lithium ion battery.

[Example 4]
Example 2 except that the compounding ratio of the members was changed from 95: 1: 1: 3: 60 (mass ratio) to 95: 1: 1: 4: 60 (mass ratio) in the preparation of the positive electrode precursor. A lithium ion battery was produced in the same manner as in the above.

[Example 5]
A lithium ion battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to gamma-butyrolactone (γ-GBL) in the production of the lithium ion battery.

[Example 6]
Example 2 except that the compounding ratio of the members was changed from 95: 1: 1: 3: 60 (mass ratio) to 95: 1: 1: 5: 60 (mass ratio) in the preparation of the positive electrode precursor. A lithium ion battery was produced in the same manner as in the above.

[Example 7]
A lithium ion battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to dimethyl sulfoxide (DMSO) in the production of the lithium ion battery.

[Example 8]
A lithium ion battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to propylene carbonate (PC) in the production of the lithium ion battery.

[Comparative Example 1]
Example 2 except that the compounding ratio of the members was changed from 95: 1: 1: 3: 60 (mass ratio) to 92: 1: 1: 6: 60 (mass ratio) in the preparation of the positive electrode precursor. A lithium ion battery was produced in the same manner as in the above.

[Comparative Example 2]
A lithium ion battery was prepared in the same manner as in Example 1 except that polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was changed to polyvinylidene fluoride (PVDF) in the preparation of the positive electrode precursor.

[Comparative Example 3]
A lithium ion battery was produced in the same manner as in Comparative Example 2 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to ethyl methyl carbonate (EMC) in the production of the lithium ion battery.

[Comparative Example 4]
A lithium ion battery was produced in the same manner as in Comparative Example 2 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to diethyl carbonate (DEC) in the production of the lithium ion battery.

[Comparative Example 5]
A lithium ion battery was produced in the same manner as in Comparative Example 2 except that the non-aqueous electrolyte solution dimethyl carbonate (DMC) was changed to propylene carbonate (PC) in the production of the lithium ion battery.

[Output characteristic evaluation]
The output characteristic evaluation was carried out by installing the lithium ion secondary battery produced above in a constant temperature bath (ARSF-0250-10, manufactured by ESPEC CORPORATION) set at 45 ° C. The lithium ion secondary battery produced above was sandwiched between a urethane rubber having a thickness of 5 mm and a silicone sponge sheet, and evaluated in a state of being restrained at 6 points using a metal plate having a thickness of 10 mm and an M6 screw. First, as a capacity confirmation at a low rate, the capacity obtained by performing charge / discharge evaluation twice at a cell voltage range of 4.2 to 2.5 V and a current value of 0.05 C rate was used as a reference capacity. The C rate was calculated based on the cell capacity obtained with the 2.5 V cutoff. Next, after charging to 4.2 V at 0.05 C, discharging was performed at a 1.5 C rate or a 3 C rate under the condition of a cell voltage of 2.5 V. The obtained 1.5C effective capacity / reference capacity × 100 was defined as a 1.5C effective capacity ratio (%), and the obtained 3C effective capacity / reference capacity × 100 was defined as a 3C effective capacity ratio (%). The results are shown in Table 1.

[Measurement of area resistance value]
With respect to the lithium ion secondary battery produced above, the area resistance value of the battery was measured under the temperature condition of 25 ° C. by the following method.

First, the battery was completely discharged and then charged, and the voltage was confirmed and adjusted to SOC 50%. Then, it was discharged at 0.1C for 10 seconds. The DC resistance value was measured from the current value I0.1C corresponding to 0.1C and the voltage change ΔV0.1C between the voltage after charging and the voltage after discharging. Then, the resistance value (Ω) was calculated from the measurement result of the DC resistance value according to Ohm's law. The area resistance value (Ω · cm ² ) was calculated by multiplying this by the electrode area (the area of the positive electrode active material layer). The results are shown in Table 1.

From the above results, the non-aqueous electrolyte secondary battery using the positive electrode of the example according to the present invention has lower internal resistance (area resistance) than the battery of the comparative example, so that the output characteristics and the quick charging characteristics are improved. It can be seen that there is a significant improvement.

10a Bipolar secondary battery,
10b Stacked secondary battery 11 current collector,
11a Outermost layer current collector on the positive electrode side,
11b Outermost layer current collector on the negative electrode side,
11'Positive Current Collector 12 Negative Electrode Current Collector 13 Positive Electrode Active Material Layer,
15 Negative electrode active material layer,
17 Electrolyte layer,
19 Single battery layer,
21,57 Power generation elements,
23 Bipolar electrode,
25 Positive electrode current collector plate (positive electrode tab),
27 Negative electrode current collector plate (negative electrode tab),
29, 52 Laminated film,
31 Seal part,
50 Lithium-ion secondary battery,
58 Positive tab,
59 Negative electrode tab.

Claims (7)

It has a current collector and an electrode active material layer which is a non-binding body arranged on the surface of the current collector.
The electrode active material layer contains an electrode active material, a gel-forming polymer, and an electrolytic solution.
The gel-forming polymer is polyvinylidene fluoride-hexafluoropropylene (PVDF-HEP), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA). , Polyethylene Glycol Dimethacrylate, Polyethylene Glycol Diacrylate, Polypropylene Glycol Dimethacrylate and Polypropylene Glycol Diacrylate, and at least one selected from the group consisting of copolymers thereof.
In the electrode active material layer, the content of the gel-forming polymer was defined as x [mass%] in terms of solid content, and the viscosity of the non-aqueous solvent constituting the electrolytic solution at 25 ° C. was defined as y [mPa · s]. when, satisfy ^{x 2} y ≦ 22.8, the non-aqueous electrolyte secondary battery. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the gel-forming polymer is 3 to 5% by mass in terms of solid content. The electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein in the electrode active material layer, the gel-forming polymer is polyvinylidene fluoride-hexafluoropropylene (PVDF-HEP). The electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the viscosity of the non-aqueous solvent at 25 ° C. is 1.99 mPa · s or less. The electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the non-aqueous solvent is a chain carbonate. The non-aqueous electrolyte secondary battery according to claim 5, wherein the chain carbonate is at least one selected from the group consisting of diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC). electrode. A non-aqueous electrolyte secondary battery having the electrode for the non-aqueous electrolyte secondary battery according to any one of claims 1 to 6.