Secondary battery, battery pack, vehicle, and stationary power supply

Abstract

To provide a secondary battery excellent in cycle life performance, a battery pack including the secondary battery, a vehicle, and a stationary power supply.SOLUTION: According to one embodiment, there is provided a secondary battery including an electrolyte containing water and a lithium salt, a positive electrode 5, and a negative electrode 3. The positive electrode 5 includes: a positive electrode active material-containing layer 5b; a positive electrode current collector 5a that supports the positive electrode active material-containing layer 5b, and that contains at least one of aluminum or an aluminum alloy; and a nitrogen-containing substance that presents at least a part of a surface of the positive electrode current collector 5a.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present invention relates to a secondary battery, a battery pack, a vehicle, and a stationary power source. [Background technology]

[0002] Non-aqueous electrolyte batteries, particularly lithium secondary batteries, using a carbon material or lithium titanium oxide as the negative electrode active material and a layered oxide containing nickel, cobalt, manganese, etc. as the positive electrode active material have already been put to practical use as power sources in a wide range of fields. Unlike nickel-hydrogen batteries or lead-acid batteries, the electrolyte of these lithium secondary batteries uses a non-aqueous organic solvent containing ethylene carbonate, methyl ethyl carbonate, etc. The electrolyte using these solvents has high oxidation resistance and reduction resistance, and is less susceptible to electrolysis of the solvent.

[0003] On the other hand, since many organic solvents are flammable substances, the safety of secondary batteries using organic solvents is, in principle, likely to be inferior to that of nickel-metal hydride batteries or lead-acid batteries. Although lithium secondary batteries with an aqueous electrolyte are safer than secondary batteries using organic solvents, they have a problem of corroding the aluminum positive electrode collector used in lithium secondary batteries. When the positive electrode collector corrodes, the charge / discharge efficiency or cycle life of the secondary battery decreases. In secondary batteries with an aqueous electrolyte, it is necessary to suppress the corrosion of the positive electrode collector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-293716 A [Patent Document 2] JP 2010-135316 A Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved is to provide a secondary battery having excellent cycle life performance, and a battery pack, a vehicle, and a stationary power source each including this secondary battery. [Means for solving the problem]

[0006] According to an embodiment, a secondary battery is provided that includes an electrolyte containing water and a lithium salt, a positive electrode, and a negative electrode. The positive electrode includes a positive electrode active material-containing layer, a positive electrode current collector on which the positive electrode active material-containing layer is supported and which contains at least one of aluminum and an aluminum alloy, and a nitrogen-containing substance present on at least a portion of the surface of the positive electrode current collector.

[0007] According to the embodiment, a battery pack including the secondary battery of the embodiment is provided.

[0008] According to the embodiment, a vehicle including the secondary battery of the embodiment is provided.

[0009] Furthermore, according to the embodiment, there is provided a stationary power source including the secondary battery of the embodiment. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a secondary battery according to an embodiment. [Diagram 2] 2 is a schematic cross-sectional view taken along line II-II of the secondary battery shown in FIG. 1. [Diagram 3] FIG. 4 is a partially cutaway perspective view illustrating a secondary battery according to another embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion E of the secondary battery shown in FIG. [Diagram 5] FIG. 1 is a perspective view illustrating an example of a battery pack according to an embodiment. [Figure 6] FIG. 13 is an exploded perspective view illustrating a battery pack according to another embodiment of the present invention. [Figure 7] 7 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG. 6. [Figure 8]FIG. 1 is a partially see-through view illustrating an example of a vehicle according to an embodiment. [Figure 9] FIG. 1 is a block diagram showing an example of a system including a stationary power supply according to an embodiment. [Figure 10] FIG. 2 is a schematic diagram showing a first example of a positive electrode of the secondary battery according to the embodiment. [Figure 11] FIG. 4 is a schematic diagram showing a second example of a positive electrode of the secondary battery according to the embodiment. [Figure 12] FIG. 4 is a schematic diagram showing a third example of a positive electrode of the secondary battery according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (First embodiment) According to an embodiment, there is provided a secondary battery including an electrolyte containing water and a lithium salt, a positive electrode, and a negative electrode. The positive electrode includes a positive electrode active material-containing layer, a positive electrode current collector on which the positive electrode active material-containing layer is supported and which contains at least one of aluminum and an aluminum alloy, and a nitrogen-containing substance present on at least a portion of the surface of the positive electrode current collector.

[0012] In secondary batteries with electrolytes containing water, in order to suppress corrosion of the positive electrode current collector, it has been considered to form the positive electrode current collector from a metal that is less susceptible to corrosion (e.g., Ti), to increase the concentration of the electrolyte and to reduce the water content, etc. However, not only are these methods insufficient in suppressing corrosion, but they also increase resistance.

[0013] The present inventors have found for the first time that in a secondary battery having an electrolyte containing water and a lithium salt, a nitrogen-containing substance is stably present on the surface of a positive electrode current collector containing at least one of aluminum and an aluminum alloy, thereby suppressing the reaction between the positive electrode current collector and the electrolyte and suppressing corrosion of the positive electrode current collector, thereby improving the charge-discharge cycle performance of the secondary battery having an electrolyte containing water.

[0014] The positive electrode, the negative electrode, and the electrolyte of the secondary battery of the embodiment will be described below.

[0015] <Positive electrode> The positive electrode includes a positive electrode current collector containing at least one of aluminum and an aluminum alloy, and a positive electrode active material-containing layer.

[0016] The positive electrode current collector has, for example, a sheet shape. The positive electrode current collector has, for example, a first surface intersecting the thickness direction of the positive electrode current collector and a second surface intersecting the thickness direction of the positive electrode current collector and positioned away from the first surface. The second surface is positioned on the opposite side to the first surface.

[0017] The positive electrode current collector may be substantially made of at least one of aluminum and an aluminum alloy, or may contain other materials. Examples of the positive electrode current collector include aluminum foil and aluminum alloy foil. The purity of the aluminum foil can be 99.99% by mass or more. The aluminum alloy can be an alloy containing at least one element selected from the group consisting of magnesium, zinc, and silicon. The positive electrode current collector can contain a transition metal such as iron, copper, nickel, or chromium. The transition metal content of the positive electrode current collector can be 100 ppm by mass or less.

[0018] The positive electrode current collector has a nitrogen-containing substance on the entire surface including the first surface and the second surface or on a part of the surface. The nitrogen-containing substance may be, for example, a substance that is deposited or accumulated on the surface of the positive electrode current collector by an electrochemical reaction or the like. The nitrogen-containing substance may be, for example, a nitrogen-containing coating or a nitrogen-containing layer. Examples of the nitrogen-containing substance include a nitrogen-containing compound, a nitrogen-containing inorganic substance, and a nitrogen-containing organic substance. Examples of the nitrogen-containing inorganic substance include metal nitrides such as Li3N and AlN. The nitrogen-containing inorganic substance can suppress corrosion of the positive electrode current collector without impairing the lithium ion conductivity of the positive electrode. The type of nitrogen-containing substance present on the surface of the positive electrode current collector can be one or more types.

[0019] The thickness of the positive electrode current collector is preferably 5 μm or more and 50 μm or less. A current collector having such a thickness can achieve a good balance between the strength and weight reduction of the electrode.

[0020] The positive electrode active material-containing layer contains a positive electrode active material. The positive electrode active material-containing layer can be supported (or formed or laminated) on at least a part of the first surface of the positive electrode current collector, at least a part of the second surface, or at least a part of each of the first surface and the second surface. The part of the positive electrode current collector on which the positive electrode active material-containing layer is not supported can function as a positive electrode current collector tab or a positive electrode current collector lead.

[0021] The nitrogen-containing substance may be present in the positive electrode active material-containing layer. The nitrogen-containing substance may be present on at least a part of the surface of the positive electrode active material-containing layer. This can increase the oxygen overvoltage, suppress the oxidative decomposition of water, and improve the charge / discharge efficiency of the secondary battery. The nitrogen-containing material may be present between the positive electrode current collector and the positive electrode active material-containing layer. The nitrogen-containing material may also be present on the surface of the positive electrode current collector on which the positive electrode active material-containing layer is not supported. The surface of the positive electrode current collector on which the positive electrode active material-containing layer is not supported may include a portion that can function as a positive electrode current collector tab or a positive electrode current collector lead.

[0022] The positive electrode active material-containing layer may further contain a conductive agent, a binder, or both. The conductive agent is mixed as necessary to improve current collection performance and reduce contact resistance between the active material and the current collector. The binder can bind the active material, the conductive agent, and the current collector.

[0023] The positive electrode active material has a lithium ion absorption and release potential of 3V (vs. Li / Li) based on metallic lithium. + ) or more and 5.5V or less (vs.Li / Li + The positive electrode may contain one type of positive electrode active material, or may contain two or more types of positive electrode active materials.

[0024] Examples of the positive electrode active material include lithium manganese composite oxides (e.g., Li x Mn2O4(0 <x≦1)、Li xMnO2 (0 < x ≤ 1)), lithium nickel composite oxide, lithium nickel manganese composite oxide (e.g., Li x Mn 2-y Ni y O4 (0 < x ≤ 1, 0 < y < 2) such as spinel type), lithium cobalt aluminum composite oxide, lithium nickel cobalt manganese composite oxide (e.g., Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2 (0 < x ≤ 1, 0 < y < 1)), lithium iron oxide, lithium fluorinated iron sulfate (e.g., Li x FeSO4F (0 < x ≤ 1)), phosphate compounds with olivine crystal structure (e.g., Li x FePO4 (0 < x ≤ 1), Li x MnPO4 (0 < x ≤ 1), Li x CoPO4 (0 < x ≤ 1)), lithium cobalt composite oxide (e.g., Li x CoO2 (0 < x ≤ 1)), lithium manganese iron composite oxide (e.g., Li x Fe 1-y Mn y PO4 (0 < x ≤ 1, 0 < y ≤ 1)), lithium nickel aluminum composite oxide (e.g., Li x Ni 1-y Al y O2 (0 < x ≤ 1, 0 < y < 1)), lithium manganese aluminum composite oxide (e.g., Li x Mn 2-y Al y O4; 0 < x ≤ 1, 0 < y ≤ 0.5), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y―z Co y Mn z O2 (0 < x ≤ 1, 0 < y < 1, 0 ≤ z < 1)) and the like are included. Phosphate compounds with olivine crystal structure are excellent in thermal stability.

[0025] At least one selected from the group consisting of lithium nickel cobalt manganese composite oxide, lithium nickel manganese composite oxide, lithium cobalt composite oxide, and lithium manganese iron composite oxide has a high positive electrode potential and can provide a high energy density.

[0026] The positive electrode active material is contained in the positive electrode in the form of particles, for example. The positive electrode active material particles may be single primary particles, secondary particles which are aggregates of primary particles, or a mixture of primary particles and secondary particles. The shape of the particles is not particularly limited, and may be, for example, spherical, elliptical, flat, or fibrous.

[0027] The average particle size (diameter) of the primary particles of the positive electrode active material is preferably 10 μm or less, more preferably 0.1 μm or more and 5 μm or less, and the average particle size (diameter) of the secondary particles of the positive electrode active material is preferably 100 μm or less, more preferably 10 μm or more and 50 μm or less.

[0028] The binder can fill the gaps in the positive electrode active material and can bind the positive electrode active material and the positive electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0029] The conductive agent can improve the current collecting performance and can suppress the contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. The conductive agent may also be omitted.

[0030] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably mixed in an amount of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

[0031] By making the amount of binder 2% by mass or more, sufficient electrode strength can be obtained. In addition, the binder can function as an insulator. Therefore, by making the amount of binder 20% by mass or less, the amount of insulator contained in the electrode is reduced, and the internal resistance can be reduced.

[0032] When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are preferably mixed in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively.

[0033] By making the amount of the conductive agent 3% by mass or more, the above-mentioned effects can be achieved. Also, by making the amount of the conductive agent 15% by mass or less, the ratio of the conductive agent in contact with the electrolyte can be reduced. If this ratio is low, decomposition of the electrolyte during high-temperature storage can be reduced.

[0034] For example, the positive electrode is prepared by suspending a positive electrode active material, a conductive agent, and a binder in a solvent to prepare a slurry. This slurry is applied to one or both sides (at least one of the first and second sides) of a current collector. The applied slurry is then dried to obtain a laminate of an active material-containing layer and a current collector. Then, this laminate is pressed. In this manner, a positive electrode is produced. Alternatively, the positive electrode may be produced by the following method. First, the active material, the conductive agent, and the binder are mixed to obtain a mixture. Then, the mixture is formed into pellets. Then, these pellets are placed on a current collector to obtain a positive electrode. <Negative electrode> The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer supported (or formed or laminated) on one surface (one main surface) or both surfaces (both main surfaces of the front and back sides) of the negative electrode current collector. The negative electrode active material-containing layer contains a negative electrode active material.

[0035] The negative electrode may contain a nitrogen-containing substance. The nitrogen-containing substance may be present, for example, in at least one of the negative electrode active material-containing layer and the negative electrode current collector. Details of the nitrogen-containing substance are as described for the positive electrode.

[0036] The negative electrode current collector may be formed of a material that is electrochemically stable at a potential at which lithium (Li) is inserted and removed from the active material. Examples of the negative electrode current collector include a conductive sheet containing a conductive material and a polymeric material, a conductive sheet containing at least one metal element selected from the group consisting of Pb, Bi, Zn, Sb, and Sn, a metal foil such as copper, nickel, stainless steel, or aluminum, and an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. Examples of the polymeric material of the conductive sheet include polyethylene, polypropylene, polyethylene terephthalate, polyacrylonitrile, polymethyl methacrylate, and polyvinylidene fluoride. The conductive material is preferably a conductive filler such as a carbonaceous material. Examples of the carbonaceous material include carbon black, ketjen black, graphite, fibrous carbon, and carbon nanotubes. The conductive material and the polymeric material may each be one or more types.

[0037] The thickness of the negative electrode current collector is preferably 5 μm or more and 50 μm or less. A current collector having such a thickness can achieve a good balance between the strength and weight reduction of the electrode.

[0038] The negative electrode current collector may include a portion on the surface of which no active material-containing layer is formed, and this portion may function as a current collecting tab or a current collecting lead.

[0039] Examples of the negative electrode active material include carbon (carbon-based material), titanium-containing oxide, Li metal, and Li alloy. The type of the negative electrode active material can be one or more. Examples of carbon (carbon-based material) include graphite, carbon body, etc. Examples of Li alloys include alloys such as Li-Al, Li-Si, Li-Zn, and Li-Mg.

[0040] The negative electrode active material contains a titanium-containing oxide. The titanium-containing oxide contains, for example, lithium ions (Li +The titanium-containing oxide may be a titanium-containing oxide that is capable of being changed into a titanium-containing oxide containing Li by an absorption / release reaction of Li or a charge / discharge reaction of Li. Therefore, the titanium-containing oxide may be a titanium-containing oxide that does not contain Li. The titanium-containing oxide that does not contain Li includes a titanium-containing oxide that does not substantially contain Li.

[0041] Examples of the titanium-containing oxide include niobium titanium-containing oxide, titanium oxide, and lithium titanium-containing oxide.

[0042] Examples of niobium titanium-containing oxides include monoclinic niobium titanium-containing oxides. Examples of monoclinic niobium titanium-containing oxides include Nb2TiO7, Nb2Ti2O9, Nb 10 Ti2O 29 , Nb 14 TiO 37 , Nb 24 TiO 62 The niobium titanium-containing oxide may be a substituted niobium titanium composite oxide in which at least a part of Nb and / or Ti is substituted with a different element. Examples of the substituted element include Na, K, Ca, Co, Ni, Si, P, V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Pb, and Al. The substituted niobium titanium composite oxide may contain one type of substituted element, or may contain two or more types of substituted elements. The active material particles may contain one type of niobium titanium-containing oxide, or may contain multiple types of niobium titanium-containing oxide. The niobium titanium-containing oxide preferably contains Nb2TiO7 having a monoclinic structure. In this case, an electrode having excellent capacity and rate performance can be obtained.

[0043] Examples of monoclinic niobium titanium oxides include Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δHere, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0044] Other examples of monoclinic niobium titanium oxides include Ti 1-y M3 y+z Nb 2-z O 7-δ Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0045] Another example of a monoclinic niobium titanium oxide is Li a TiM b Nb 2±β O 7±σ (0≦a≦5, 0≦b≦0.3, 0≦β≦0.3, 0≦σ≦0.3, M is at least one element selected from the group consisting of Fe, V, Mo and Ta).

[0046] Titanium oxide includes, for example, titanium oxide with a monoclinic structure, titanium oxide with a rutile structure, and titanium oxide with anatase structure. Titanium oxide with each crystal structure has a composition of TiO2 before charging and a composition of LiO2 after charging. x It can be expressed as TiO2 (x is 0≦x≦1). The structure of titanium oxide with a monoclinic crystal structure before charging can be expressed as TiO2(B).

[0047] The lithium titanium-containing oxide is, for example, a lithium titanium oxide having a spinel structure (e.g., a lithium titanium oxide having the general formula Li 4+x Ti5O 12 where -1≦x≦3), lithium titanium oxides with the ramsdellite structure (e.g., Li 2+x Ti3O7 (-1≦x≦3), Li 1+xA compound represented by Ti2O4 where 0 ≦ x ≦ 1, Li 1.1+x Ti 1.8 A compound represented by O4 where 0 ≦ x ≦ 1, Li 1.07+x Ti 1.86 A compound represented by O4 where 0 ≦ x ≦ 1, Li x It includes compounds represented by TiO2 where 0 < x ≦ 1, etc. Further, the lithium titanium-containing oxide may be a lithium titanium composite oxide into which a different element is introduced.

[0048] The type of the negative electrode active material can be one type or two or more types.

[0049] A negative electrode containing at least one selected from the group consisting of a niobium titanium-containing oxide, a titanium oxide, and a lithium titanium-containing oxide, when combined with a positive electrode containing at least one selected from the group consisting of a lithium nickel cobalt manganese composite oxide, a lithium nickel manganese composite oxide, a lithium cobalt composite oxide, and a lithium manganese iron composite oxide, can obtain a secondary battery having a high voltage and energy density.

[0050] The negative electrode active material is contained in the negative electrode active material-containing layer in the form of particles, for example. The negative electrode active material particles can be primary particles, secondary particles that are aggregates of primary particles, or a mixture of single primary particles and secondary particles. The shape of the particles is not particularly limited and can be, for example, spherical, elliptical, flat, and fibrous.

[0051] The average particle diameter (diameter) of the primary particles of the negative electrode active material is preferably 3 μm or less, more preferably 0.01 μm or more and 1 μm or less. The average particle diameter (diameter) of the secondary particles of the negative electrode active material is preferably 30 μm or less, more preferably 5 μm or more and 20 μm or less.

[0052] The negative electrode active material-containing layer may contain a binder. The binder can fill the gaps in the active material and can bind the active material to the negative electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber (SBR), polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0053] The negative electrode active material-containing layer may contain a conductive agent, which is mixed as necessary in order to improve current-collecting performance and reduce contact resistance between the active material and the current collector.

[0054] Examples of the conductive agent include carbonaceous materials such as acetylene black, ketjen black, graphite, and coke. The conductive agent may be used alone or in combination of two or more kinds.

[0055] The mixing ratio of the negative electrode active material, the conductive agent, and the binder is preferably in the range of 70% by mass or more and 95% by mass or less of the negative electrode active material, 3% by mass or more and 20% by mass or less of the conductive agent, and 0.6% by mass or more and 10% by mass or less of the binder. When the mixing ratio of the conductive agent is 3% by mass or more, the current collection performance of the negative electrode active material-containing layer can be improved. When the mixing ratio of the binder is 2% by mass or more, sufficient electrode strength can be obtained. The binder can function as an insulator. Therefore, when the mixing ratio of the binder is 10% by mass or less, the insulating part in the electrode can be reduced.

[0056] The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in an aqueous solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. Then, this laminate is pressed. In this manner, a negative electrode is produced. <Electrolytes> The electrolyte includes water and a lithium salt.

[0057] The electrolyte includes an aqueous solvent and a lithium salt dissolved in the aqueous solvent. The electrolyte may be liquid or gel. The liquid electrolyte is, for example, an aqueous solution prepared by dissolving a lithium salt as a solute in an aqueous solvent. The gel electrolyte is, for example, prepared by mixing a liquid electrolyte with a polymer compound to form a composite. Examples of the polymer compound include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO). When an electrolyte is held in both the negative electrode active material-containing layer and the positive electrode active material-containing layer, the types of these electrolytes may be the same or different.

[0058] As the aqueous solvent, a solution containing water can be used. The solution containing water may be pure water or a mixed solvent of water and an organic solvent. Examples of the solvent (organic solvent) include phosphoric acid esters such as trimethyl phosphate (TMP), cyclic carbonates such as ethylene carbonate (EC), and chain carbonates.

[0059] The water content in the electrolyte can be 150 ppm by mass or more and 100,000 ppm by mass or less. By making the water content 150 ppm by mass or more, the safety of the electrolyte can be increased. Furthermore, by making the water content 100,000 ppm by mass or less, the generation of gas due to the electrolysis of water can be suppressed. The water content can be 200 ppm by mass or more. This increases the solubility of N-containing compounds (e.g., nitric acid compounds) in the electrolyte, thereby promoting the generation of nitrogen-containing substances in the positive electrode. Furthermore, the safety of the electrolyte can be further increased.

[0060] As the electrolyte salt, for example, a lithium salt can be used. The type of lithium salt can be one or more.

[0061] Examples of lithium salts that can be used include lithium chloride (LiCl), lithium bromide (LiBr), lithium hydroxide (LiOH), lithium sulfate (Li2SO4), lithium acetate (CH3COOLi), lithium oxalate (Li2C2O4), lithium carbonate (Li2CO3), lithium difluorooxalatoborate (LiDFOB, C2BF2LiO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI; LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiFSI; LiN(FSO2)2), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI; LiN(SO2C2F5)2), lithium bisoxalatoborate (LiBOB: LiB[(OCO)2]2), and lithium triflate (LiOtF; LiCF3SO3, also known as lithium trifluoromethylsulfonate).

[0062] The lithium salt may include a lithium salt having an imide bond. Examples of preferred lithium salts having an imide bond include LiTFSI (LiN(CF3SO2)2) and LiBETI (LiN(SO2C2F5)2). LiTFSI is highly stable in water, so it is difficult to be hydrolyzed and gas generation can be suppressed. On the other hand, the nitrogen-containing material can suppress the reaction between the electrolyte containing LiTFSI and the positive electrode current collector. Therefore, by combining the nitrogen-containing material with the electrolyte containing LiTFSI, it is possible to realize a secondary battery in which hydrolysis of the lithium salt is suppressed, gas generation is suppressed, and corrosion of the positive electrode current collector is suppressed.

[0063] The concentration of the lithium salt in the electrolyte can be in the range of 1.2 mol / kg to 3.8 mol / kg. By setting the concentration of the lithium salt in the above range, the ionic conductivity of the electrolyte can be increased. A more preferable range of the concentration of the lithium salt is 1.8 mol / kg to 3.5 mol / kg. The concentration was calculated by dividing the number of moles of the lithium salt by the weight of the solvent, in mol / kg.

[0064] The electrolyte preferably contains at least one nitric acid compound selected from the group consisting of lithium nitrate (LiNO3), sodium nitrate (NaNO3), potassium nitrate (KNO3), magnesium nitrate (Mg(NO3)2), calcium nitrate (Ca(NO3)2), lithium nitrite (LiNO2), sodium nitrite (NaNO2), potassium nitrite (KNO2), magnesium nitrite (Mg(NO2)2), and calcium nitrite (Ca(NO2)2). The nitric acid compound can form a nitrogen-containing substance on the surface of the positive electrode current collector under certain conditions (an example will be described later). As a result, the corrosion of the positive electrode current collector can be suppressed, and the charge / discharge cycle life of the secondary battery can be improved.

[0065] The electrolyte may contain an N-containing compound, but may not contain one. The N-containing compound may be, for example, a raw material for the nitrogen-containing material present in the positive electrode. Examples of the N-containing compound include nitric acid compounds and organic compounds having a nitrile group. The type of N-containing compound may be one or more types. The content of the N-containing compound in the electrolyte may be 0.3% by mass or more and 4% by mass or less. By making the content of the N-containing compound 0.3% by mass or more, the corrosion inhibition effect of the positive electrode current collector can be increased. By making the content of the N-containing compound 4% by mass or less, the amount of nitrogen-containing material produced can be appropriate, so that the resistance increase can be suppressed. A more preferable range of the content of the N-containing compound is 0.3% by mass or more and 1% by mass or less.

[0066] The electrolyte contains chloride ions (Cl) as an anion species. - ), hydroxide ion (OH - ), sulfate ion (SO4 2- ), nitrate ion (NO3 - ) may contain at least one selected from the following.

[0067] The electrolyte may contain a surfactant. Examples of the surfactant include non-ionic surfactants such as polyoxyalkylene alkyl ether, polyethylene glycol, polyvinyl alcohol, thiourea, disodium 3,3'-dithiobis(1-propanephosphoric acid), dimercaptothiadiazole, boric acid, oxalic acid, malonic acid, saccharin, sodium naphthalenesulfonate, gelatin, potassium nitrate, aromatic aldehyde, and heterocyclic aldehyde. The surfactant may be used alone or in combination of two or more.

[0068] The battery of the embodiment may further include at least one of a separator or an exterior member. The positive electrode, the negative electrode, and the separator may constitute an electrode group. The electrolyte may be held in the electrode group.

[0069] <separator> The separator is disposed, for example, between the positive electrode and the negative electrode. The separator may include a separator that covers only one of the positive electrode or the negative electrode.

[0070] The separator can have a porous structure. Examples of the porous separator include nonwoven fabric, film, and paper. Examples of the constituent materials of the porous separator that constitutes the nonwoven fabric, film, and paper include polyolefins such as polyethylene and polypropylene, and cellulose. Examples of preferred porous separators include nonwoven fabrics containing cellulose fibers and porous films containing polyolefin fibers.

[0071] The porosity of the porous separator is preferably 60% or more. The fiber diameter is preferably 10 μm or less. By making the fiber diameter 10 μm or less, the affinity of the porous separator to the electrolyte is improved, so that the battery resistance can be reduced. The fiber diameter is more preferably in the range of 3 μm or less. A cellulose fiber-containing nonwoven fabric with a porosity of 60% or more has good electrolyte impregnation and can provide high output performance from low to high temperatures. The porosity is more preferably in the range of 62% to 80%.

[0072] The porous separator has a thickness of 20 μm to 100 μm and a density of 0.2 g / cm 3 More than 0.9g / cm 3 Within this range, a balance between mechanical strength and reduced battery resistance can be achieved, and a secondary battery with high output and suppressed internal short circuit can be provided. In addition, the separator undergoes little thermal shrinkage in a high-temperature environment, and good high-temperature storage performance can be achieved.

[0073] The separator may be a composite separator including a porous separator and a layer containing inorganic particles formed on one or both sides of the porous separator. Examples of inorganic particles include aluminum oxide and silicon oxide.

[0074] A solid electrolyte layer may be used as the separator. The solid electrolyte layer may include solid electrolyte particles and a polymer component. The solid electrolyte layer may be composed of only solid electrolyte particles. The solid electrolyte layer may include one type of solid electrolyte particles, or may include multiple types of solid electrolyte particles. The solid electrolyte layer may include at least one selected from the group consisting of a plasticizer and an electrolyte salt. When the solid electrolyte layer includes an electrolyte salt, for example, the alkali metal ion conductivity of the solid electrolyte layer can be further increased. The form of the polymer material may be, for example, granular or fibrous.

[0075] The solid electrolyte layer is preferably in a sheet shape and has few or no pores such as pinholes. The thickness of the solid electrolyte layer is not particularly limited, but is, for example, 150 μm or less, and preferably in the range of 20 μm to 50 μm.

[0076] The polymer component used in the solid electrolyte layer is preferably a polymer component insoluble in an aqueous solvent. Examples of polymer components that satisfy this condition include polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), and fluorine-containing polymer components. By using a fluorine-containing polymer component, water repellency can be imparted to the separator. In addition, inorganic solid electrolytes have high stability against water and excellent lithium ion conductivity. By forming a composite of a lithium ion conductive inorganic solid electrolyte and a fluorine-containing polymer component, a flexible solid electrolyte layer with alkali metal ion conductivity can be realized. A separator made of this solid electrolyte layer can reduce resistance, thereby improving the large current performance of a secondary battery.

[0077] Examples of the fluorine-containing polymer component include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride (PVdF), etc. The type of the fluorine-containing polymer component can be one or more types.

[0078] When the solid electrolyte layer contains a polymer component, the content of the polymer component in the solid electrolyte layer is preferably 1% by mass or more and 20% by mass or less. In this range, when the thickness of the solid electrolyte layer is set in the range of 10 to 100 μm, high mechanical strength can be obtained and resistance can be reduced. Furthermore, there is little risk that the solid electrolyte will become a factor that inhibits lithium ion conductivity. A more preferable range of this content is 3% by mass or more and 10% by mass or less.

[0079] As the solid electrolyte, it is preferable to use an inorganic solid electrolyte. The inorganic solid electrolyte is a solid substance having Li-ion conductivity. Here, having Li-ion conductivity is 1×10 -6 It means that the inorganic solid electrolyte has a lithium ion conductivity of 1.0 S / cm or more. Examples of the inorganic solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of the inorganic solid electrolyte are as follows.

[0080] The oxide-based solid electrolyte has a NASICON (Sodium (Na) Super Ionic Conductor) type structure and is represented by the general formula Li 1+x It is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. In the above general formula, Mα is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0≦x≦2.

[0081] A specific example of a lithium phosphate solid electrolyte having a NASICON structure is Li 1+x Al x Ti 2-x LATP compound represented by (PO4)3, where 0.1≦x≦0.5; Li 1+x Al y Mβ 2-y A compound represented by the formula (PO4)3, in which Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca, and 0≦x≦1 and 0≦y≦1; Li 1+x Al x Ge2-x A compound represented by (PO4)3 where 0 ≦ x ≦ 2; and Li 1+x Al x Zr 2-x A compound represented by (PO4)3 where 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 A compound represented by where Mγ is one or more selected from the group consisting of Ti and Ge and 0 < x ≦ 2, 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x Examples of the compound represented by (PO4)3 where 0 ≦ x < 1 can be given.

[0082] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, Li x PO y N z An amorphous LIPON compound represented by where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46 ); A garnet-type structure La 5+x A x La 3-x Mδ2O 12 A compound represented by where A is one or more selected from the group consisting of Ca, Sr, and Ba and Mδ is one or more selected from the group consisting of Nb and Ta and 0 ≦ x ≦ 0.5; Li3Mδ 2-x L2O 12 A compound represented by where Mδ is one or more selected from the group consisting of Nb and Ta and L may contain Zr and 0 ≦ x ≦ 0.5; Li 7-3x Al x La3Zr3O 12 A compound represented by where 0 ≦ x ≦ 0.5; Li 5+x La3Mδ 2-x Zr x O 12 A compound represented by where Mδ is one or more selected from the group consisting of Nb and Ta and 0 ≦ x ≦ 2, an LLZ compound (for example, Li7La3Zr2O 12 ); And having a perovskite-type structure La2 / 3-x Li x Examples of such compounds include those represented by TiO3, where x is 0.3≦x≦0.7.

[0083] One or more of the above compounds can be used as the solid electrolyte. Two or more of the above solid electrolytes can also be used.

[0084] <Exterior materials> The exterior member contains at least a positive electrode, a negative electrode, a separator, and an electrolyte. For example, a metal container, a laminated film container, or a resin container can be used as the exterior member. For the metal container, a metal can made of nickel, iron, stainless steel, or the like, having a rectangular or cylindrical shape can be used. For the resin container, a container made of polyethylene, polypropylene, or the like can be used.

[0085] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0086] The laminate film is a multi-layer film including a plurality of resin layers and a metal layer interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of the exterior member by sealing it by heat fusion.

[0087] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0088] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of the transition metals is preferably 100 ppm by mass or less.

[0089] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin, or button. The exterior member can be appropriately selected depending on the battery dimensions and the application of the battery.

[0090] The secondary battery according to the embodiment can be used in various forms such as a square, cylindrical, flat, thin, coin type, etc. The secondary battery may be a secondary battery having a bipolar structure. For example, the electrode group may have a bipolar structure in which a positive electrode active material-containing layer is provided on one side of a single current collector and a negative electrode active material-containing layer is provided on the other side. In this case, there is an advantage that a plurality of cells connected in series can be produced from a single cell.

[0091] The methods for checking the positive electrode active material, negative electrode active material, nitrogen-containing material, and electrolyte are described below.

[0092] If the battery contains positive and negative electrodes, disassemble the battery, remove the positive or negative electrode, and clean it with dimethyl carbonate (DMC). The cleaning method is explained below. Immerse the electrode (positive or negative) in DMC for 5 minutes and remove the electrode. Repeat this three times, dry the electrode, and then subject it to measurement. When repeating the immersion, use new DMC solution each time.

[0093] To extract the electrolyte from a battery, the battery is disassembled, and if the electrolyte is present outside the electrodes, the electrolyte that is not impregnated in the electrodes is extracted. If the electrolyte cannot be extracted from outside the electrodes, the group of electrodes is placed in a centrifuge and the electrolyte is extracted by centrifugation. <Cathode active material> The crystal structure and elemental composition of the positive electrode active material can be confirmed by powder X-ray diffraction (XRD) measurement and inductively coupled plasma (ICP) optical emission spectrometry. <Negative electrode active material> The crystal structure and elemental composition of the negative electrode active material can be confirmed by powder X-ray diffraction (XRD) measurement and inductively coupled plasma (ICP) optical emission spectrometry. <XPS analysis> Whether nitrogen-containing substances are present on the surface of the positive electrode and the surface of the positive electrode current collector can be determined by XPS analysis under the conditions described below.

[0094] As the XPS apparatus, Quantera SXM manufactured by ULVAC-PHI, Inc., or an apparatus having equivalent functions can be used. As the excitation X-ray source, single crystal monochromatic Al-Kα rays (1486.6 eV) are used. The X-ray output is 4 kW (13 kV × 310 mA), the photoelectron detection angle is 45°, and the analysis area is about 4 mm × 0.2 mm. The scan is performed at 0.10 eV / step. <Electrolyte> That the electrolyte contains an N-containing compound (for example, a nitric acid-based compound), a lithium salt, and water can be confirmed by GC-MS (gas chromatography - mass spectrometry) measurement. Further, the water content in the electrolyte can be measured, for example, by evaporating the water in the electrolyte and measuring the weight ratio between the electrolyte and the residue. Weigh a prescribed amount of the electrolyte and evaporate the electrolyte in an inert atmosphere. The water content can be calculated from the weight ratio to the residue. It can also be measured by Karl Fischer measurement (coulometric titration method).

[0095] The content of N-containing compounds (e.g., nitric acid compounds) in the electrolyte and the lithium salt concentration can be measured, for example, by ICP (Inductively Coupled Plasma) emission spectrometry. The molar concentration (mol / kg) can be calculated by weighing a specified amount of electrolyte and calculating the salt concentration. Also, the number of moles of solute and solvent can be calculated by measuring the specific gravity of the electrolyte.

[0096] An example in which the battery of the embodiment is applied to a secondary battery will be described with reference to FIGS.

[0097] The secondary battery 1 includes an electrode group 2 and an exterior member 20 in which the electrode group 2 is housed. The electrode group 2 is housed in the exterior member 20 made of a rectangular cylindrical metal container. The electrode group 2 includes a negative electrode 3, a separator 4, and a positive electrode 5. The electrode group 2 has a structure in which the separator 4 is interposed between the positive electrode 5 and the negative electrode 3 and wound in a spiral shape to form a flat shape. An electrolyte (not shown) is held in the electrode group 2. As shown in FIG. 2, a strip-shaped negative electrode lead 16 is electrically connected to each of a plurality of points on the end of the negative electrode 3 located on the end face of the electrode group 2. In addition, a strip-shaped positive electrode lead 17 is electrically connected to each of a plurality of points on the end of the positive electrode 5 located on this end face. The plurality of negative electrode leads 16 are connected to the negative electrode terminal 6 in a bundled state as shown in FIG. 2. In addition, although not shown, the positive electrode lead 17 is also electrically connected to the positive electrode terminal 7 in a bundled state.

[0098] The metal sealing plate 21 is fixed to an opening of the metal exterior member 20 by welding or the like. The negative electrode terminal 6 and the positive electrode terminal 7 are each drawn out to the outside through an extraction hole provided in the sealing plate 21. A negative electrode gasket 8 and a positive electrode gasket 9 are disposed on the inner circumferential surface of each extraction hole of the sealing plate 21 to prevent a short circuit due to contact with the negative electrode terminal 6 and the positive electrode terminal 7, respectively. By disposing the negative electrode gasket 8 and the positive electrode gasket 9, the airtightness of the secondary battery 100 can be maintained.

[0099] A control valve 22 (safety valve) is disposed on the sealing plate 21. When the internal pressure of the battery cell increases due to gas generated in the exterior member 20, the generated gas can be released to the outside from the control valve 22. The control valve 22 may be of a reset type that operates when the internal pressure exceeds a set value and functions as a sealing plug when the internal pressure decreases. Alternatively, a non-reset type control valve that does not recover its function as a sealing plug once it is activated may be used. In FIG. 1, the control valve 22 is disposed in the center of the sealing plate 21, but the control valve 22 may be located at the end of the sealing plate 21. The control valve 22 may be omitted.

[0100] Further, the sealing plate 21 is provided with a liquid inlet 23. The electrolyte can be injected through this liquid inlet 23. After the electrolyte is injected, the liquid inlet 23 can be closed by a sealing plug 24. The liquid inlet 23 and the sealing plug 24 may be omitted.

[0101] Another example of the secondary battery will be described with reference to Figures 3 and 4. Figures 3 and 4 show an example of a secondary battery 1 that uses an exterior member made of a laminate film as a container.

[0102] The secondary battery 1 shown in Figures 3 and 4 includes an electrode group 2 shown in Figures 3 and 4, an exterior member 20 shown in Figure 3, and an electrolyte (not shown). The electrode group 2 and the electrolyte are housed in the exterior member 20. The electrolyte is held in the electrode group 2.

[0103] The exterior member 20 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0104] The electrode group 2 is a laminated type electrode group, as shown in Fig. 4. The laminated type electrode group 2 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0105] The electrode group 2 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides (e.g., both main surfaces) of the negative electrode current collector 3a. The electrode group 2 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides (e.g., the first and second surfaces) of the positive electrode current collector 5a.

[0106] The negative electrode current collector 3a of each negative electrode 3 includes a portion 3c on one side of which the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c serves as a negative electrode current collector tab. As shown in FIG. 4, the portion 3c serving as the negative electrode current collector tab does not overlap with the positive electrode 5. The multiple negative electrode current collector tabs (portions 3c) are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is pulled out to the outside of the exterior member 20.

[0107] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion serves as a positive electrode current collector tab. The positive electrode current collector tab does not overlap with the negative electrode 3, similar to the negative electrode current collector tab (portion 3c). The positive electrode current collector tab is located on the opposite side of the electrode group 2 to the negative electrode current collector tab (portion 3c). The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side to the negative electrode terminal 6, and is drawn out to the outside of the exterior member 20.

[0108] An example of the positive electrode 5 of the secondary battery is shown in Figs. 10 to 12. In Figs. 10 to 12, the same reference numerals are used for common members, and the description thereof is omitted. The positive electrode 5 shown in each of Figs. 10 to 12 includes a positive electrode current collector 5a, a positive electrode active material-containing layer 5b, and a positive electrode current collector tab. In each of the figures, the positive electrode current collector tab and the positive electrode active material-containing layer 5b provided on the other surface of the positive electrode current collector 5a are omitted. In addition, the positive electrode active material-containing layer 5b includes positive electrode active material particles 500, but in each of the figures, components other than the positive electrode active material particles 500 are omitted. In each of Figs. 10 to 12, the direction parallel to the thickness direction of the positive electrode 5 is shown as the z-axis direction. The first surface 502 and the second surface 503 of the positive electrode current collector 5a are parallel to a plane defined by the x-axis direction and the y-axis direction.

[0109] 10, nitrogen-containing material 501 is present between a part of first surface 502 of positive electrode current collector 5a and positive electrode active material-containing layer 5b. According to one example, nitrogen-containing material 501 has a layer or film shape.

[0110] 11, a nitrogen-containing material 501 is present between a portion of a first surface 502 of a positive electrode current collector 5a facing the positive electrode active material-containing layer 5b and the positive electrode active material-containing layer 5b. According to one example, the nitrogen-containing material 501 is in the form of a layer or a film.

[0111] 10 and 11 show an example in which the nitrogen-containing substance 501 is present on the surface of the positive electrode current collector 5a, but the present invention is not limited thereto, and the nitrogen-containing substance 501 may also be present on a part of the surface of the positive electrode active material-containing layer 5b, as shown in, for example, FIG. 12. In the example of FIG. 12, the nitrogen-containing substance 501 is present on a part of the surface of the positive electrode current collector 5a, but the nitrogen-containing substance 501 may be present on the entire part of the first surface 502 of the positive electrode current collector 5a that faces the positive electrode active material-containing layer 5b, as shown in, for example, FIG. 11. The nitrogen-containing substance 501 is, for example, in the form of a layer or a film.

[0112] <Manufacturing method> The secondary battery according to the embodiment can be manufactured, for example, as follows.

[0113] The method for producing the secondary battery includes preparing an anode, preparing a cathode, preparing an electrolyte containing water, a lithium salt, and a nitric acid-based compound, preparing an exterior member, housing the anode and cathode in the exterior member, injecting the electrolyte into the exterior member, sealing the exterior member to obtain a battery precursor, aging the battery precursor at 45°C to 80°C for 5 minutes to 120 minutes, and charging at room temperature (e.g., 25°C) at a current rate of 0.05C to 2C until the state of charge (SOC) is 30% to 100%. By aging at 45°C to 80°C for 5 minutes to 120 minutes, the electrolyte (e.g., electrolyte solution) can be sufficiently wetted into the positive electrode layer including the positive electrode current collector. Thereafter, a current is applied to the battery to charge it, thereby forming a coating containing nitrogen. This method allows the nitric acid compound to be decomposed on the positive electrode current collector, so that a nitrogen-containing coating can be formed as a nitrogen-containing substance on at least a part of the surface of the positive electrode current collector. After charging and discharging, the generated gas can be removed from the battery as appropriate.

[0114] The negative electrode and the positive electrode can be prepared, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, this laminate is pressed. In this manner, each electrode is prepared. A negative electrode active material is used as the active material for preparing a negative electrode, and a positive electrode active material is used as the active material for preparing a positive electrode.

[0115] Alternatively, each electrode may be prepared by the following method: first, the active material, the conductive agent, and the binder are mixed to obtain a mixture, then the mixture is formed into pellets, and then the pellets are placed on a current collector to obtain an electrode.

[0116] The electrolyte can be prepared, for example, by dissolving a lithium salt and a nitric acid compound in an aqueous solvent to prepare a solution.

[0117] In the above manufacturing method, the N-containing compound contained in the electrolyte is not limited to a nitric acid compound. For example, an organic compound having a nitrile group (e.g., adiponitrile) may be contained as the N-containing compound. In this case, a nitrogen-containing coating can be formed as a nitrogen-containing material on at least a part of the surface of the positive electrode current collector.

[0118] Alternatively, instead of adding an N-containing compound (e.g., a nitric acid-based compound, an organic compound having a nitrile group) as a nitrogen source to the electrolyte, a nitrogen-containing coating can be formed as a nitrogen-containing material on at least a part of the surface of the positive electrode current collector by performing a plasma nitriding treatment on an aluminum foil or an aluminum alloy foil that is a positive electrode current collector. Then, an active material-containing slurry is applied to one side or both sides of the positive electrode current collector, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector, and then the laminate is pressed. A positive electrode may be produced by this method. When a secondary battery is produced using the obtained positive electrode, aging and charging do not need to be performed under the above conditions, and aging or charging can be omitted.

[0119] The secondary battery of the embodiment described above includes a positive electrode, a negative electrode, and an electrolyte containing water and a lithium salt. The positive electrode includes a positive electrode active material-containing layer, a positive electrode current collector on which the positive electrode active material-containing layer is supported and which contains at least one of aluminum and an aluminum alloy, and a nitrogen-containing substance present on at least a part of the surface of the positive electrode current collector. The secondary battery of the embodiment can suppress corrosion of the positive electrode current collector, thereby improving the charge-discharge cycle performance.

[0120] Second embodiment According to a second embodiment, there is provided a battery pack including a plurality of secondary batteries according to the embodiment.

[0121] In the battery pack according to this embodiment, the individual cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0122] Next, an example of a battery pack will be described with reference to the drawings.

[0123] 5 includes five cells 100a to 100e, four bus bars 201, a positive electrode lead 207, and a negative electrode lead 206. Each of the five cells 100a to 100e is a secondary battery according to the embodiment.

[0124] The bus bar 201 connects, for example, the negative electrode terminal 6 of one cell 100a and the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by the four bus bars 201. That is, the battery pack 200 in FIG. 5 is a five-series battery pack. Although no example is shown, in a battery pack including a plurality of cells electrically connected in parallel, for example, the plurality of negative electrode terminals are connected to each other by a bus bar and the plurality of positive electrode terminals are connected to each other by a bus bar, thereby electrically connecting the plurality of cells.

[0125] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to a positive electrode lead 207 for external connection. In addition, the negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to a negative electrode lead 206 for external connection.

[0126] The battery pack according to the embodiment includes the secondary battery according to the embodiment, and therefore the battery pack can have excellent life performance.

[0127] [Third embodiment] According to a third embodiment, a battery pack including a secondary battery according to the embodiment is provided. The battery pack may include the battery assembly according to the embodiment. The battery pack may include a single battery instead of the battery assembly according to the embodiment.

[0128] Such a battery pack may further include a protection circuit. The protection circuit has a function of controlling charging and discharging of the secondary battery. Alternatively, a circuit included in a device (e.g., electronic device, automobile, etc.) that uses the battery pack as a power source may be used as the protection circuit for the battery pack.

[0129] The battery pack may further include an external terminal for current flow. The external terminal for current flow is for outputting current from the secondary battery to the outside and / or inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for current flow. When the battery pack is charged, a charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminal for current flow.

[0130] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0131] The battery pack 300 shown in Figs. 6 and 7 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0132] 6 is a bottomed, square container having a rectangular bottom. The container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31 to accommodate the battery pack 200 and the like. Although not shown, the container 31 and the lid 32 are provided with openings or connection terminals for connection to an external device or the like.

[0133] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 207, a negative electrode lead 206, and an adhesive tape .

[0134] At least one of the plurality of unit cells 100 is a secondary battery according to the embodiment. Each of the plurality of unit cells 100 is electrically connected in series as shown in FIG. 7. The plurality of unit cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of unit cells 100 are connected in parallel, the battery capacity is increased compared to when they are connected in series.

[0135] The adhesive tape 36 fastens the plurality of unit cells 100. The plurality of unit cells 100 may be fixed using heat shrink tape instead of the adhesive tape 36. In this case, the protective sheets 33 are disposed on both side surfaces of the battery pack 200, the heat shrink tape is wrapped around the battery pack 200, and the heat shrink tape is then thermally shrunk to bind the plurality of unit cells 100 together.

[0136] One end of the positive electrode lead 207 is connected to the battery pack 200. One end of the positive electrode lead 207 is electrically connected to the positive electrode of one or more of the cells 100. One end of the negative electrode lead 206 is connected to the battery pack 200. One end of the negative electrode lead 206 is electrically connected to the negative electrode of one or more of the cells 100.

[0137] The printed wiring board 34 is disposed along one of the short side surfaces of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for supplying electricity, a positive wiring (positive wiring) 348a, and a negative wiring (negative wiring) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0138] The other end 207a of the positive electrode lead 207 is electrically connected to the positive electrode connector 342. The other end 206a of the negative electrode lead 206 is electrically connected to the negative electrode connector 343.

[0139] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100, and transmits a detection signal to the protection circuit 346.

[0140] The external terminal 350 for current supply is fixed to the other main surface of the printed wiring board 34. The external terminal 350 for current supply is electrically connected to a device present outside the battery pack 300. The external terminal 350 for current supply includes a positive terminal 352 and a negative terminal 353.

[0141] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive electrode connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative electrode connector 343 via a wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

[0142] The protective sheet 33 is disposed on both inner surfaces in the long side direction of the container 31 and on the inner surface in the short side direction that faces the printed wiring board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0143] The protection circuit 346 controls charging and discharging of the multiple cells 100. In addition, the protection circuit 346 cuts off electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345, or a detection signal transmitted from each of the cells 100 or the battery pack 200.

[0144] An example of the detection signal transmitted from the thermistor 345 is a signal that detects that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal that detects overcharging, overdischarging, and overcurrent of the cell 100. When detecting overcharging or the like for each cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 100.

[0145] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0146] As described above, the battery pack 300 includes the external terminal 350 for current supply. Therefore, the battery pack 300 can output a current from the assembled battery 200 to an external device and input a current from the external device to the assembled battery 200 via the external terminal 350 for current supply. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 350 for current supply. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 through the external terminal 350 for current supply. When the battery pack 300 is used as an in-vehicle battery, regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0147] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 207 and the negative electrode lead 206 may be used as the positive and negative terminals of the external terminals for current supply, respectively.

[0148] Such a battery pack is used in applications that require excellent cycle performance, for example, when a large current is drawn. Specifically, the battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. An example of the electronic device is a digital camera. The battery pack is particularly suitable for use as an on-board battery.

[0149] The battery pack according to the third embodiment includes the secondary battery according to the embodiment or the battery assembly according to the embodiment, and therefore has excellent life performance.

[0150] [Fourth embodiment] According to a fourth embodiment, a vehicle including a battery pack according to an embodiment is provided.

[0151] In such a vehicle, the battery pack, for example, recovers regenerative energy of the vehicle's motive power. The vehicle may include a mechanism (regenerator) that converts the kinetic energy of the vehicle into regenerative energy.

[0152] Examples of vehicles according to the embodiment include two-wheeled to four-wheeled hybrid electric vehicles, two-wheeled to four-wheeled electric vehicles, power-assisted bicycles, and rail vehicles.

[0153] The mounting position of the battery pack in the vehicle according to the embodiment is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0154] The vehicle according to the embodiment may be equipped with a plurality of battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, electrically connected in parallel, or electrically connected by a combination of series and parallel connections. For example, when each battery pack includes a battery pack, the battery packs may be electrically connected in series, electrically connected in parallel, or electrically connected by a combination of series and parallel connections. Alternatively, when each battery pack includes a single battery, the batteries may be electrically connected in series, electrically connected in parallel, or electrically connected by a combination of series and parallel connections.

[0155] Next, an example of a vehicle according to an embodiment will be described with reference to the drawings.

[0156] A vehicle 400 shown in Fig. 8 includes a vehicle body 40 and a battery pack 300 according to the embodiment. In the example shown in Fig. 8, the vehicle 400 is a four-wheeled automobile.

[0157] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (e.g., single cells or assembled batteries) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0158] 8 illustrates an example in which the battery pack 300 is mounted in an engine room located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, in the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for the motive power of the vehicle 400.

[0159] The vehicle according to the fourth embodiment is equipped with the battery pack according to the embodiment, and therefore the vehicle can exhibit high performance and is highly reliable.

[0160] [Fifth embodiment] According to a fifth embodiment, there is provided a stationary power source including a battery pack according to an embodiment.

[0161] Such a stationary power source may be equipped with a battery pack according to an embodiment or a battery according to an embodiment instead of the battery pack according to an embodiment. Such a stationary power source can exhibit a long life.

[0162] FIG. 9 is a diagram showing an application example to stationary power sources 112 and 123 as an example of use of the battery packs 300A and 300B according to the embodiment. In the example shown in FIG. 9, a system 110 in which the stationary power sources 112 and 123 are used is shown. The system 110 includes a power plant 111, a stationary power source 112, a consumer-side power system 113, and an energy management system (EMS) 115. A power grid 116 and a communication network 117 are also formed in the system 110, and the power plant 111, the stationary power source 112, the consumer-side power system 113, and the EMS 115 are connected via the power grid 116 and the communication network 117. The EMS 115 utilizes the power grid 116 and the communication network 117 to perform control to stabilize the entire system 110.

[0163] The power plant 111 generates a large amount of power using fuel sources such as thermal power and atomic power. Power is supplied from the power plant 111 through a power grid 116 or the like. A battery pack 300A is mounted on the stationary power source 112. The battery pack 300A can store the power supplied from the power plant 111. The stationary power source 112 can supply the power stored in the battery pack 300A through the power grid 116 or the like. The system 110 is provided with a power conversion device 118. The power conversion device 118 includes a converter, an inverter, a transformer, and the like. Thus, the power conversion device 118 can perform conversion between direct current and alternating current, conversion between alternating currents having different frequencies, and voltage transformation (boosting and bucking), and the like. Thus, the power conversion device 118 can convert the power from the power plant 111 into power that can be stored in the battery pack 300A.

[0164] The consumer-side power system 113 includes a power system for a factory, a power system for a building, a power system for a home, etc. The consumer-side power system 113 includes a consumer-side EMS 121, a power conversion device 122, and a stationary power source 123. The stationary power source 123 is equipped with a battery pack 300B. The consumer-side EMS 121 performs control to stabilize the consumer-side power system 113.

[0165] The consumer-side power system 113 is supplied with power from the power plant 111 and power from the battery pack 300A through the power grid 116. The battery pack 300B can store the power supplied to the consumer-side power system 113. Similarly to the power conversion device 118, the power conversion device 122 includes a converter, an inverter, a transformer, and the like. Therefore, the power conversion device 122 can perform conversion between DC and AC, conversion between ACs with different frequencies, and voltage transformation (boost and step-down), etc. Therefore, the power conversion device 122 can convert the power supplied to the consumer-side power system 113 into power that can be stored in the battery pack 300B.

[0166] The power stored in the battery pack 300B can be used, for example, to charge a vehicle such as an electric car. The system 110 may also be provided with a natural energy source. In this case, the natural energy source generates power using natural energy such as wind power and solar power. Power is supplied from the natural energy source in addition to the power plant 111 through the power grid 116. EXAMPLES

[0167] The above embodiment will be specifically described below using examples, but the present invention is not limited to the following examples as long as they do not deviate from the gist of the present invention. Example 1 <Preparation of negative electrode> As the negative electrode active material, particles of a monoclinic niobium titanium-containing oxide having a composition represented by the formula Nb2TiO7 were prepared. This monoclinic niobium titanium-containing oxide has a high solubility in Li aIt has a composition represented by Nb2TiO7 (0≦a≦5). In addition, acetylene black as a conductive agent, and carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR) as binders were prepared. These were mixed in pure water so that the mass ratio (mass%) of negative electrode active material: acetylene black: carboxymethylcellulose: styrene butadiene rubber was 95: 4.2: 0.4: 0.4 to obtain a slurry. This slurry was applied to both sides of a current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Thus, a composite including a current collector and a negative electrode active material-containing layer formed on the current collector was obtained. Next, the obtained composite was pressed, and the composite was further dried to obtain a negative electrode.

[0168] <Preparation of positive electrode> The positive electrode active material is LiNi 0.33 Mn 0.33 Co 0.33 Particles of lithium nickel cobalt manganese composite oxide represented by O2 (referred to as NMC111) were prepared. In addition, acetylene black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder were prepared. These were mixed so that the mass ratio (mass%) of the positive electrode active material: conductive agent: binder was 90:5:5 to obtain a mixture. Next, the obtained mixture was dispersed in n-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry was applied onto a current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Thus, a composite including a current collector and a positive electrode active material-containing layer formed on both sides of the current collector was obtained. Next, the obtained composite was pressed and further dried to obtain a positive electrode.

[0169] The positive and negative electrodes were each cut out so that the area where the active material-containing layer was formed was 3 cm wide and 5 cm high. One negative electrode and one positive electrode were attached to each other via a 30 μm thick cellulose separator to produce an electrode laminate as an electrode group. In addition, aluminum tabs with a thickness of 0.2 mm were attached to the negative and positive electrodes to collect current. The produced electrode laminate was housed in an exterior member made of a laminate film, and after pouring in a liquid electrolyte, it was sealed to obtain a secondary battery.

[0170] The liquid electrolyte had a composition of 48.5 mass% LiN(CF3SO2)2 (LiTFSI), 50.4 mass% ethylene carbonate (EC), 1.0 mass% lithium nitrate (LiNO3), and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 3.3 mol / kg.

[0171] After the electrolyte was injected, the battery was aged by being kept in a constant temperature bath at 60°C for 30 minutes, and then charged to SOC100% at a current rate of 0.05C at 25°C, and then discharged to SOC0% at a current rate of 0.1C. The battery was then opened, the generated gas was removed, and the battery was again vacuum sealed, and a charge-discharge cycle test was performed at 25°C. At 25°C, the battery was charged to 2.9V at 0.2C, and then discharged to 1.8V at 0.2C. This charge-discharge cycle was repeated 50 times, and the retention rate (%) of the discharge capacity at the 50th cycle relative to the discharge capacity at the 1st cycle was calculated, and is shown in Table 2 as the capacity retention rate during the charge-discharge cycle. Example 2 A secondary battery was produced in the same manner as in Example 1, except that the negative electrode active material was TiO2(B), and a charge-discharge cycle test was carried out. Example 3 The negative electrode active material is Li4Ti5O 12 A negative electrode was produced in the same manner as in Example 1, except that acetylene black was used as a conductive agent, and polyvinylidene fluoride (PVdF) was used as a binder, and these were mixed so that the mass ratio (mass%) of negative electrode active material:conductive agent:binder was 90:5:5. A secondary battery was produced in the same manner as in Example 1, except that the obtained negative electrode was used, and a charge-discharge cycle test was performed. Example 4 The negative electrode active material is Nb 10 Ti2O 29 Except for the above, a secondary battery was produced in the same manner as in Example 1, and a charge-discharge cycle test was carried out. Example 5 The positive electrode active material is LiAl 0.2 Mn 1.8A positive electrode was prepared in the same manner as in Example 1, except that O4 (LMO) was used. In addition, the liquid electrolyte used had a composition consisting of 36.4 mass% LiN(CF3SO2)2 (LiTFSI), 2.4 mass% LiN(F2SO2)2 (LiFSI), 60.1 mass% trimethyl phosphate (TMP), 1.0 mass% lithium nitrate, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.3 mol / kg. The lithium salt concentration shown in Table 1 is the total value of the LiTFSI concentration and the LiFSI concentration. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained positive electrode and liquid electrolyte were used, and a charge-discharge cycle test was performed. Example 6 The positive electrode active material is LiMn 0.7 Fe 0.3 A positive electrode was prepared in the same manner as in Example 1, except that PO4 (LMFP) was used. In addition, the liquid electrolyte used had a composition consisting of 36.3 mass% LiN(CF3SO2)2 (LiTFSI), 2.5 mass% LiB(C2O4)2 (LiBOB), 60.1 mass% trimethyl phosphate (TMP), 1.0 mass% lithium nitrate, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.3 mol / kg. The lithium salt concentration shown in Table 1 is the sum of the LiTFSI concentration and the LiBOB concentration. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained positive electrode and liquid electrolyte were used, and a charge-discharge cycle test was performed. Example 7 The positive electrode active material is LiNi 0.5 Mn 1.5 A positive electrode was prepared in the same manner as in Example 1, except that O4 (LNMO) was used. In addition, the liquid electrolyte used had a composition consisting of 37.3 mass% LiN(CF3SO2)2 (LiTFSI), 61.6 mass% trimethyl phosphate (TMP), 1.0 mass% lithium nitrate, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained positive electrode and liquid electrolyte were used, and a charge-discharge cycle test was performed. Example 8 The liquid electrolyte used had a composition of 37.5 mass% LiN(CF3SO2)2(LiTFSI), 61.9 mass% trimethyl phosphate (TMP), 0.5 mass% sodium nitrate, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. Example 9 The liquid electrolyte used had a composition of 37.5 mass% LiN(CF3SO2)2(LiTFSI), 61.9 mass% trimethyl phosphate (TMP), 0.5 mass% lithium nitrite, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. Example 10 The liquid electrolyte used had a composition of 37.5 mass% LiN(CF3SO2)2(LiTFSI), 61.9 mass% trimethyl phosphate (TMP), 0.5 mass% sodium nitrite, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. Example 11 The liquid electrolyte used had a composition of 37.3 mass% LiN(CF3SO2)2(LiTFSI), 61.684 mass% trimethyl phosphate (TMP), lithium nitrate, and 0.016 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. Example 12 The liquid electrolyte used had a composition of 37.1 mass% LiN(CF3SO2)2(LiTFSI), 61.35 mass% trimethyl phosphate (TMP), 1.0 mass% lithium nitrate, and 0.55 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. (Example 13) The liquid electrolyte used had a composition of 37.1 mass% LiN(CF3SO2)2(LiTFSI), 52.4 mass% trimethyl phosphate (TMP), 1.0 mass% lithium nitrate, and 9.5 mass% H2O. The lithium salt concentration of the liquid electrolyte was 2.0 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. Example 14 A positive electrode was produced in the same manner as in Example 1, except that an aluminum foil that had been subjected to plasma nitriding treatment was used as the positive electrode current collector. A secondary battery was produced in the same manner as in Example 1, except that the obtained positive electrode was used, and a charge-discharge cycle test was performed. Example 15 The liquid electrolyte used had a composition of 48.5 mass% LiN(CF3SO2)2(LiTFSI), 50.4 mass% ethylene carbonate (EC), 1.0 mass% adiponitrile, and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 3.3 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed. Comparative Example 1 The liquid electrolyte used had a composition of 49.0 mass% LiN(CF3SO2)2(LiTFSI), 50.9 mass% ethylene carbonate (EC), and 0.1 mass% H2O. The lithium salt concentration of the liquid electrolyte was 3.3 mol / kg. A secondary battery was manufactured in the same manner as in Example 1, except that the obtained liquid electrolyte was used, and a charge-discharge cycle test was performed.

[0172] Table 1 shows the negative electrode active material composition, positive electrode active material composition, type of N-containing compound, concentration of N-containing compound in the electrolyte (mass%), water concentration (water content) in the electrolyte (ppm by mass), type of lithium salt and type of solvent other than water contained in the electrolyte, and lithium salt concentration in the electrolyte (moL / kg) for the examples and comparative examples.

[0173] The surface state of the positive electrode current collector and the positive electrode active material-containing layer of the secondary batteries of Examples 1 to 15 was confirmed by the above-mentioned XPS analysis. For Examples 1 to 13, it was confirmed that Li3N and AlN were present on the surface of the positive electrode current collector in contact with the positive electrode active material-containing layer and on the surface of the positive electrode active material-containing layer. For example, an N1S peak was observed near 397 eV, an Li1S peak was observed near 56 eV, and an Al2P peak was observed near 73 eV. These are considered to be derived from compounds such as Li-N and Al-N, and can be said to be the presence of Li3N and AlN. In Example 14, it was confirmed that an oxide in which part of oxygen was nitrided was present on the surface of the positive electrode collector in contact with the positive electrode active material-containing layer. It is presumed that the oxide in which part of oxygen was nitrided was generated by nitriding the Al passive film on the surface of the positive electrode collector. In addition, in Example 15, it was confirmed that an organic compound having a C-N bond was present on both the surface of the positive electrode collector in contact with the positive electrode active material-containing layer and the surface of the positive electrode active material-containing layer.

[0174] On the other hand, when the surface states of the positive electrode current collector and the positive electrode active material-containing layer of the secondary battery of Comparative Example 1 were confirmed by the above-mentioned XPS analysis, no nitrogen-containing substances were found.

[0175] [Table 1]

[0176] [Table 2]

[0177] As is clear from Tables 1 to 3, the secondary batteries of Examples 1 to 15 have higher capacity retention rates during charge / discharge cycles than the secondary battery of Comparative Example 1. In the secondary battery of Comparative Example 1, corrosion of the positive electrode current collector was more advanced than in the secondary batteries of Examples 1 to 15.

[0178] The secondary batteries of Examples 1 to 13, in which the nitrogen-containing material contained a metal nitride, had a higher capacity retention rate during charge-discharge cycles than the secondary battery of Example 14, which used a nitrogen-containing material containing an oxide in which part of oxygen is nitrided, and the secondary battery of Example 15, which used a nitrogen-containing material containing an organic compound having a C-N bond.

[0179] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0180] The following describes the embodiments of the invention. <1> an electrolyte comprising water and a lithium salt; a positive electrode including a positive electrode active material-containing layer, a positive electrode current collector on which the positive electrode active material-containing layer is supported and which contains at least one of aluminum and an aluminum alloy, and a nitrogen-containing substance present on at least a portion of a surface of the positive electrode current collector; a negative electrode. <2> The positive electrode active material-containing layer further includes a nitrogen-containing substance present on at least a portion of a surface thereof. <1> The secondary battery according to claim 1. <3> The electrolyte includes at least one selected from the group consisting of lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, lithium nitrite, sodium nitrite, potassium nitrite, magnesium nitrite, and calcium nitrite. <1> or <2> The secondary battery according to claim 1. <4> The water content in the electrolyte is 150 ppm or more and 100,000 ppm or less. <1> ~ <3> 13. The secondary battery according to claim 12, <5> The positive electrode active material contained in the positive electrode active material-containing layer includes at least one selected from the group consisting of lithium nickel cobalt manganese composite oxide, lithium nickel manganese composite oxide, lithium cobalt composite oxide, and lithium manganese iron composite oxide. <1> ~ <4> 13. The secondary battery according to claim 12, <6> The negative electrode contains at least one selected from the group consisting of niobium titanium-containing oxide, titanium oxide, lithium titanium-containing oxide, and carbon. <1> ~ <5> 13. The secondary battery according to claim 12, <7> The negative electrode is a mixture of a niobium titanium-containing oxide having a monoclinic structure, TiO2(B), and Li 4+x Ti5O 12 (-1≦x≦3), <1> ~ <6> 13. The secondary battery according to claim 12, <8> <1> ~ <7> 13. A battery pack comprising the secondary battery according to claim 12. <9> Further including an external terminal for current supply and a protection circuit. <8> The battery pack according to claim 1 . <10> The battery includes a plurality of the secondary batteries, the secondary batteries being electrically connected in series, in parallel, or in a combination of series and parallel. <8> or <9> The battery pack according to claim 1 . <11> <8> from <10> A vehicle equipped with a battery pack according to any one of claims 1 to 5. <12> A mechanism for converting the kinetic energy of the vehicle into regenerative energy. <11> A vehicle as described in. <13> <8> from <10> A stationary power source comprising the battery pack according to any one of claims 1 to 5. [Explanation of symbols]

[0181] 1...battery, 2...electrode group, 3...negative electrode, 3a...negative electrode current collector, 3b...negative electrode composite layer (negative electrode active material-containing layer), 4...separator, 5...positive electrode, 5a...positive electrode current collector, 5b...positive electrode composite layer (positive electrode active material-containing layer), 6...negative electrode terminal, 7...positive electrode terminal, 8...negative electrode gasket, 9...positive electrode gasket, 16...negative electrode lead, 17...positive electrode lead, 20...exterior member, 21...sealing plate, 22...control valve, 23...filling port, 24...sealing plug, 31...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 36...adhesive tape, 40...vehicle body, 100...secondary battery, 110...system, 111...power plant, 112...stationary power source, 113...consumer side Power system, 115...energy management system, 116...power grid, 117...communication network, 118...power conversion device, 121...demand side EMS, 122...power conversion device, 123...stationary power source, 200...battery pack, 201...bus bar, 206...negative side lead, 207...positive side lead, 300...battery pack, 300A...battery pack, 300B...battery pack, 342...positive side connector, 342a...wiring, 343...negative side connector, 343a...wiring, 345...thermistor, 346...protection circuit, 348a...positive side wiring, 348b...negative side wiring, 350...external terminal for energization, 352...positive side terminal, 353...negative side terminal, 400...vehicle.

Claims

1. an electrolyte comprising water and a lithium salt; a positive electrode including a positive electrode active material-containing layer, a positive electrode current collector on which the positive electrode active material-containing layer is supported and which contains at least one of aluminum and an aluminum alloy, and a nitrogen-containing substance present on at least a portion of a surface of the positive electrode current collector; a negative electrode.

2. The secondary battery according to claim 1 , further comprising a nitrogen-containing substance present on at least a portion of a surface of the positive electrode active material-containing layer.

3. 2. The secondary battery according to claim 1, wherein the electrolyte contains at least one selected from the group consisting of lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrite, lithium nitrite, sodium nitrite, potassium nitrite, magnesium nitrite, and calcium nitrite.

4. 2. The secondary battery according to claim 1, wherein the water content in the electrolyte is 150 ppm or more and 100,000 ppm or less.

5. 2. The secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode active material-containing layer includes at least one selected from the group consisting of lithium nickel cobalt manganese composite oxide, lithium nickel manganese composite oxide, lithium cobalt composite oxide, and lithium manganese iron composite oxide.

6. 2. The secondary battery according to claim 1, wherein the negative electrode contains at least one selected from the group consisting of niobium titanium-containing oxide, titanium oxide, lithium titanium-containing oxide, and carbon.

7. The negative electrode is made of a niobium titanium-containing oxide, TiO 2 (B), and Li 4+x Ti 5 O 12 The secondary battery according to claim 1, comprising at least one selected from the group consisting of (-1≦x≦3).

8. A battery pack comprising the secondary battery according to any one of claims 1 to 7.

9. 9. The battery pack according to claim 8, further comprising an external terminal for current flow and a protection circuit.

10. 10. The battery pack according to claim 9, comprising a plurality of the secondary batteries, the secondary batteries being electrically connected in series, in parallel, or in a combination of series and parallel.

11. A vehicle comprising the battery pack according to claim 8.

12. The vehicle of claim 11 including a mechanism for converting kinetic energy of the vehicle into regenerative energy.

13. A stationary power source comprising the battery pack according to claim 8.

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