JP2001015172A - Nonaqueous secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery having a high capacity. SOLUTION: In this nonaqueous secondary battery having a positive electrode sheet 1 containing a positive electrode active material having a transition metal composite oxide containing lithium as a main ingredient, and a negative electrode sheet 2 containing a carbon material capable of storing and releasing lithium, and a nonaqueous electrolyte containing lithium salt, a negative electrode sheet formed by metal foil containing lithium as a main ingredient affixed in advance through an auxiliary layer and a nonaquesous electrolyte containing an aromatic compound as an additive are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high capacity non-aqueous secondary battery using a material in which lithium is previously supported on a carbon anode material.

[0002]

2. Description of the Related Art In recent years, with the spread of portable personal computers and mobile phones, demands for higher capacity secondary batteries have increased.
Lithium-ion nonaqueous secondary batteries that use a lithium-containing transition metal composite oxide as the positive electrode and a carbon material that can store and release lithium as the negative electrode are small secondary batteries because of their high voltage, light weight, and high energy density. Has occupied the leading role. With the growing demand for batteries, users are demanding higher energy densities,
Active material development is being actively pursued with a view to increasing the energy density of consumer batteries and powering electric vehicles in the future.

[0003] In particular, the development of carbon materials used for the negative electrode has been active, and recently, L is considered to be the theoretical limit of lithium occlusion.
High-capacity carbon materials exceeding iC ₆ (372 mAh / g) have also been found, and “the formation of lithium ion clusters in voids in carbon”, “the formation of lithium graphite intercalation compounds having a LiC 2 composition”, Occlusion mechanisms such as "covalent bond of lithium" and "formation of ion complex composed of aromatic molecule and lithium ion" have been proposed.

[0004] To increase the capacity of a secondary battery, it is extremely important to increase the initial charge and discharge efficiency of the carbon material as well as to increase the capacity of the carbon material. That is, if the initial charge / discharge efficiency of the carbon material is low and part of the lithium stored in the negative electrode during the charging process causes a plurality of irreversible side reactions and lithium does not return to the positive electrode during the discharging process, the consumed amount may be reduced. In order to compensate for the lithium, it is necessary to additionally incorporate a lithium-containing metal oxide, which is a positive electrode active material, in the secondary battery in advance. The optimization of the raw materials and firing conditions of the carbon material, the configuration of the electrode sheet, the configuration of the electrolyte solution, the battery manufacturing process, and the like have been energetically advanced, and the initial charge / discharge efficiency has been improved, but has not yet reached 100%. And
A graphite-based carbon material having a relatively good initial charge / discharge efficiency has a disadvantage that the initial charge / discharge efficiency is reduced when propylene carbonate is used as a solvent for the electrolytic solution.

As a technique for improving the initial charge / discharge efficiency of a carbon material, it has been proposed that lithium is already supported on the carbon material in advance to compensate for the charge / discharge loss, thereby improving the initial charge / discharge efficiency. Japanese Patent Application Laid-Open No. 5-28,985 proposes that lithium is preliminarily supported on a carbon material having a polyacene-like structure obtained by calcining a phenol resin in an inert atmosphere to compensate for charge / discharge loss. ing. The method for supporting lithium is described as being appropriately selected from known methods such as an electrolysis method, a gas phase method, a liquid phase method, and an ion implantation method, and no specific examples are disclosed. JP-A-5-28,986, JP-A-5-28,987, and 5-2
Nos. 9,023, 5-159,805, 5-15
9,806, 5-159,806, 5-32
5,965, 5-325,972, 6-20,
Similarly, no specific disclosure is given for the proposals of Nos. 722 and 6-203,833.

[0006] Japanese Patent Application Laid-Open No. 7-808,852 (WO95 /
08852) discloses a specific method for preliminarily supporting lithium on a carbon material. Lithium is preliminarily doped with lithium by applying a potential lower than the lithium metal potential using an electrochemical cell having lithium metal as a counter electrode. There are two methods: assembling the rear battery and assembling the battery after attaching lithium metal to the negative electrode sheet.If lithium is doped in advance by both methods, the carbon negative electrode sheet has a very high reaction activity, so the Even when processing is performed in a high-precision dehydration atmosphere, deterioration is large and it is difficult to secure a high energy density as expected. Further, in a doped carbon negative electrode sheet, the bending strength is remarkably reduced, and in particular, in a cylindrical battery, winding of the negative electrode sheet is difficult, and an increase in internal resistance due to peeling of the electrode layer from the current collector frequently occurs. As described above, the method of preliminarily inserting lithium into a carbon material is not preferable because there is a major obstacle in the production of cylindrical batteries and prismatic batteries used in portable personal computers and cellular phones. Further, Japanese Patent Application Laid-Open Nos. 8-64,247 and 8-6
4,248, 8-64,249, 8-64,2
No. 50, No. 8-64, 251 and No. 8-64, 252
And the methods described in JP-A Nos. 8-162159 and 162-159 are also not preferable because they have substantially the same difficulty.

Japanese Patent Application Laid-Open No. 8-64,247 discloses a method for preparing a negative electrode sheet in which a lithium metal foil is directly adhered to both upper and lower outer peripheral surfaces of a negative electrode sheet containing a carbon material, and then preparing a battery. The material reacts with the lithium metal foil with heat generation, which increases the internal resistance, which is not preferable.

Japanese Patent Application Laid-Open No. 8-162161 discloses a method of placing lithium discs at the bottom of a battery can and electrochemically doping lithium into a carbon material by utilizing contact with the end of a negative electrode current collector. Is not preferable because it is difficult to make the lithium doping concentration uniform in the negative electrode sheet and it takes a long time for doping. Further, the processing load is undesirably increased.

Further, Japanese Patent Application Laid-Open No. 8-255,633,
The method of compensating the lithium reduction of the positive electrode sheet transferred to the carbon negative electrode material by the charging of -255,634 and 8-255,635 from the lithium metal installed in the battery via a resistor in the battery is as follows. , Increase in parts and processing steps,
Non-uniformity of the lithium concentration in the positive electrode sheet is a limitation in manufacturing. Further, in a method of assembling a battery by sandwiching a lithium unit formed by embedding a lithium metal foil in a copper expanded metal with a roller in a copper expanded metal disclosed in JP-A-9-102,328 between negative electrodes, it is difficult to prepare a lithium unit. It is not preferable because there are restrictions such as difficulty in layering.

Further, in a lithium ion secondary battery using graphite as a negative electrode active material proposed in JP-A-8-255,633, the irreversible capacity is reduced by using an electrolyte containing a carbonate having an aromatic ring. In this method, the first cycle efficiency remains at 70 to 80%.

[0011] Many of these proposals have a high need to increase the capacity of a non-aqueous secondary battery by preliminarily supporting lithium on a carbon material and compensating for the charge / discharge loss to improve the initial charge / discharge efficiency. Is simply shown.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the initial charge / discharge efficiency by preliminarily supporting lithium on a carbon material to compensate for the charge / discharge loss, and to improve the productivity. It is to provide a capacity non-aqueous secondary battery.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a positive electrode sheet containing a positive electrode active material mainly composed of a lithium-containing transition metal composite oxide, a negative electrode sheet containing a carbon material capable of occluding and releasing lithium, and In a non-aqueous secondary battery having a non-aqueous electrolyte containing a lithium salt, the negative electrode sheet has a configuration in which a metal foil mainly composed of lithium is previously bonded via an auxiliary layer, and the non-aqueous electrolyte has at least one kind of This has been achieved by a non-aqueous secondary battery characterized by containing a hydrazine derivative and / or an aromatic compound.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a non-aqueous secondary battery of the present invention will be described in detail. The non-aqueous secondary battery having a high energy density that is the object of the present invention is a metal foil mainly composed of lithium, after creating a negative electrode sheet containing a carbon material provided via an auxiliary layer, a positive electrode sheet, a separator And a non-aqueous secondary battery is assembled together, an electrolyte containing at least one hydrazine derivative and / or an aromatic compound is injected, and then aging is performed, thereby substantially preliminarily supporting lithium on the carbon material. You. The preferable amount of preliminarily supported lithium is appropriately selected based on the amount of irreversible side reaction with lithium of the negative electrode material, that is, the charge and discharge efficiency in the initial cycle.

Aging is carried out at a temperature between 0 ° C. and 80 ° C. for 1 day to 2 days.
0 days is preferred, but 4-20 days between 20-60 ° C.
Days are particularly preferred.

The portion to which the metal foil mainly composed of lithium is pressed may be at any position as long as it is on the negative electrode sheet. The overlapping pattern is preferably such that a metal foil having a constant thickness is overlapped on the entire surface of the negative electrode sheet. However, it is also possible to use not only the entire surface of the negative electrode sheet but also partial overlapping such as stripe (vertical / horizontal) or frame-like. The interval of the overlapping of the stripes is preferably constant, but need not be constant. Also, a lattice-like pattern combining the vertical direction and the horizontal direction can be used. A roll transfer method or a board transfer method is used as a method of laminating a metal foil mainly composed of lithium on a negative electrode material.

The roll transfer method is a method in which a metal foil cut to an arbitrary size is once adhered to a roll, and then continuously adhered to a negative electrode sheet while performing a calendar press. It is preferable to use a twin roller for improving the sticking property. The roll may have any size, but preferably has a diameter of 0.5 to 100 cm, more preferably 1 to 50 cm. The roll material is preferably a material that does not easily react with lithium, and is preferably a polymer such as polyolefin (polyethylene, polypropylene, etc.), polyimide, polycarbonate, or the like, or a metal, such as stainless steel or molybdenum. The board transfer method is a method in which a metal foil cut to an arbitrary size is once stuck on a flat surface, and then stuck on a negative electrode sheet while pressing. The material of the board is preferably the same as the material of the roll.

Preferred examples of the metal foil mainly composed of lithium include, for example, Li-Al, Li-Al-Mn, and L-Al.
i-Al-Mg, Li-Al-Sn, Li-Al-I
n, Li-Al-Cd and the like, and preferable metals that can be alloyed with lithium include, for example, Al, Al-M
n, Al-Mg, Al-Sn, Al-In and the like.
The lithium content of the metal foil is preferably at least 90%, most preferably at least 98%. The thickness of the lithium foil is important from the viewpoint of uniformity, and is 1 to 100 μm.
Is preferably 5 to 50 μm or less, more preferably about 10 to 40 μm.

The lithium-based metal foil contains at least another layer of water-insoluble particles on the mixture layer and contains no negative electrode material in order to avoid a rapid reaction accompanied by heat generation with the negative electrode material. A layer is provided and crimped thereon.

In the present invention, the auxiliary layer provided on the negative electrode sheet is composed of at least one layer, and may be composed of a plurality of layers of the same type or different types. These auxiliary layers may be insulating layers having substantially no electron conductivity or conductive layers. Further, a form in which a conductive layer and an insulating layer are stacked may be employed. The thickness of the auxiliary layer is preferably from 0.2 μm to 40 μm,
It is more preferably from 20 μm to 20 μm. The auxiliary layer is composed of water-insoluble insulating particles, water-insoluble conductive particles, and an organic polymer material. Examples of the water-insoluble insulating particles of the present invention include inorganic particles and organic particles.

Examples of the inorganic particles include metal and nonmetal chalcogenites (for example, sulfides and oxides), carbides, silicides, and nitrides. For chalcogenite, an oxide is preferable, and an oxide that is hardly reduced is preferable.

These oxides include, for example, Al ₂
O ₃ , As ₄ O ₆ , B ₂ O ₃ , BaO, BeO, CaO, L
i ₂ O, K ₂ O, Na ₂ O, In ₂ O ₃ , MgO, Sb
₂ O ₅ , SiO ₂ , SrO, ZrO ₄ are mentioned. Among them, Al ₂ O ₃ , BaO, BeO, CaO, K ₂ O,
Na ₂ O, MgO, SiO ₂ , SrO, ZrO ₄ are particularly preferred. These oxides may be used alone or as a composite oxide. Preferred compounds as the composite oxide include mullite (3Al ₂ O ₃ .2SiO ₂ ), steatite (MgO.SiO ₂ ), and forsterite (2M
gO.SiO ₂ ), cordierite (2MgO.2Al ₂₎
O ₃ · 5SiO ₂ ). Among carbides, silicides, and nitrides, SiC, aluminum nitride (AlN), BN, and BP are preferable because they have high insulation properties and are chemically stable. Particularly, SiC using BeO, Be, or BN as a sintering aid is preferred. Particularly preferred. These insulative inorganic compound particles are produced by controlling the production conditions or by grinding.
0.1 μm or more and 20 μm or less, particularly preferably 0.2 μm
It is used as particles having a size of not less than μm and not more than 15 μm.

The organic particles are preferably a crosslinked latex or a powder of a fluororesin, and those which do not decompose or form a film at 300 ° C. or lower are preferable. More preferred is a fine powder of Teflon.

Examples of the water-insoluble conductive particles include metals, metal oxides, and metal fibers.

The metal powder is preferably copper, nickel, iron, molybdenum, titanium, tungsten, or tantalum, which has low reactivity with lithium and hardly forms an alloy. The shape of these metal powders may be any of a needle shape, a column shape, a plate shape, and a lump shape, and the maximum diameter is preferably 0.02 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm or less. It is preferable that the surface of these metal powders is not excessively oxidized. When the surfaces are oxidized, it is preferable to perform heat treatment in a reducing atmosphere.

The ratio of the conductive particles contained in the auxiliary layer is as follows:
5 wt% or more and 96 wt% or less, preferably 5 wt% or more and 95 wt% or less, more preferably 10 wt% or more,
Particularly preferred is 93% by weight or less.

As the organic polymer material used in the auxiliary layer of the present invention together with the particles having substantially no conductivity and / or with the conductive particles, a binder used when forming an electrode mixture described later is used. Can be mentioned. The ratio of the particles to the organic polymer is such that the particles are 40% of the total weight of both.
It is preferably at least 50% by weight and at most 96% by weight, more preferably at least 50% by weight and at most 94% by weight.

The auxiliary layer is applied by applying a mixture mainly composed of a metal or a semi-metal oxide, which is a material capable of reversibly storing and releasing lithium, on the current collector. A sequential coating method in which the layers are sequentially coated or a simultaneous coating method in which the mixture layer and the auxiliary layer are simultaneously coated may be used.

In order to improve the initial charge / discharge efficiency of the carbon material, the battery of the present invention has at least one hydrazine derivative and / or aromatic compound as an additive in addition to the negative electrode sheet prepared by the above-described method. Is used.

The hydrazine derivative added to the electrolyte is
A nitrogen-substituted or unsubstituted alkyl group, aryl group,
It is preferably substituted by a heterocyclic group, an acyl group, an oxycarbonyl group, and a sulfonyl group.
Preferred substituted or unsubstituted alkyl groups have a total carbon number of 1
To 12, for example, methyl, ethyl, isopropyl, t-butyl, allyl, cyclohexyl, benzyl and the like. Preferred substituted or unsubstituted aryl groups have 6 to 20 carbon atoms, and include, for example, phenyl and naphthyl. Preferred substituted or unsubstituted heterocyclic groups have a total of 1 to 12 carbon atoms and include, for example, pyridyl, pyrazyl, quinolyl, furyl, thienyl, benzimidazolyl, indazolyl and the like. Preferred substituted or unsubstituted acyl groups have 1 to 12 carbon atoms in total, and include, for example, formyl, acetyl, pivaloyl, benzoyl and the like. Preferred substituted or unsubstituted oxycarbonyl groups have 1 to 12 carbon atoms in total, and include, for example, methoxycarbonyl, t-butoxycarbonyl, benzyloxycarbonyl, phenoxycarbonyl and the like. Preferred sulfonyl groups include, for example, methylsulfonyl, phenylsulfonyl,
p-Toluenesulfonyl and the like. Specific examples of the hydrazine derivative added to the electrolyte include 1,2-
Bis (methoxycarbonyl) -1,2-dimethylhydrazine, 1,2-bis (ethoxycarbonyl) -1,2-
Dimethylhydrazine, 1,2-bis (t-butoxycarbonyl) -1,2-dimethylhydrazine, 1,2-bis (ethoxycarbonyl) -1-methyl-2-phenylhydrazine, 1,2-bis (ethoxycarbonyl) -1,
2-diphenylhydrazine and the like can be mentioned.

Specific examples of the aromatic compound to be added to the electrolyte include a monocyclic aromatic compound such as benzene / furan / thiophene / pyridine; acenes having the same cyclic structure such as naphthalene / anthracene; and indene / fluorene. Such as hydrocarbon-based aromatic compounds having different types of cyclic structures, aromatic compounds having an oxygen-containing cyclic structure derived from dioxybenzene, dioxynaphthalene, dioxyanthracene, such as catechol carbonate, benzofuran, dibenzofuran, etc. Aromatic compounds having an oxygen-containing aromatic ring, aromatic compounds having a sulfur-containing aromatic ring such as thiophene / benzothiophene / dibenzothiophene, aromatic compounds having a nitrogen-containing aromatic ring such as pyridine / quinoline / acridine / indole / carbazole, And this Substitution products of the like.

The amount of hydrazine and / or aromatic compound added to the electrolyte can be arbitrarily selected, but is preferably 0.01 to 10% by weight, particularly preferably 0.1 to 10% by weight, based on the whole electrolyte. 0.5 to 5% by weight.

Further, other compounds may be added to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, ethylene glycol dialkyl ether, quaternary ammonium salt, polyethylene glycol,
Pyrrole, 2-methoxyethanol, AlCl ₃ , triethylene phosphoramide, trialkylphosphine, morpholine, aryl compound having a carbonyl group, 12
Crown ethers such as -crown-4, hexamethylphosphoric triamide and 4-alkylmorpholine, bicyclic tertiary amines, oils, quaternary phosphonium salts, tertiary sulfonium salts and the like.

Further, in order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolyte. In addition, carbon dioxide gas can be included in the electrolytic solution in order to provide suitability for high-temperature storage.

Solvents usable in the present invention include propylene
Lencarbonate, ethylene carbonate, butyleneca
-Carbonate, dimethyl carbonate, diethyl carbonate
, Methyl ethyl carbonate, γ-butyrolact
, Methyl formate, methyl acetate, 1,2-dimethoxyethane
, Tetrahydrofuran, 2-methyltetrahydrofuran
Dimethylsulfoxide, 1,3-dioxolane, e
Lumamide, dimethylformamide, dioxolan, di
Oxane, acetonitrile, nitromethane, ethyl mono
Grime, phosphoric acid triester, trimethoxymethane,
Dioxolane derivative, sulfolane, 3-methyl-2-o
Xazolidinone, propylene carbonate derivative, tet
Lahydrofuran derivative, ethyl ether, 1,3-pro
List aprotic organic solvents such as pansaltone
Can be used alone or in combination of two or more.
You. Of these, carbonate solvents are preferred.
And a mixture of cyclic carbonate and non-cyclic carbonate
It is particularly preferred to use them. As cyclic carbonates
Tylene carbonate and propylene carbonate are preferred
No. In addition, as the acyclic carbonate, diethyl carbonate
Carbonate, dimethyl carbonate, methyl ethyl carbonate
Nates are preferred. As an electrolyte that can be used in the present invention
Is ethylene carbonate, propylene carbonate,
1,2-dimethoxyethane, dimethyl carbonate
Or lithium electrolyte in an electrolyte
CF_ThreeSO_Three, LiClO_Four, LiBF_FourAnd / or L
iPF₆An electrolytic solution containing Especially propylene car
At least one of carbonate and ethylene carbonate
And dimethyl carbonate or diethyl carbonate
LiCF in at least one of the mixed solvents_ThreeSO_Three, L
iCLO_FourOr LiBF_FourSelected from among
And a kind of salt and LiPF ₆An electrolytic solution containing This
The amount of these electrolytes added to the battery is not particularly limited.
Depending on the amount of electrode and anode materials and the size of the battery,
Can be.

The entire amount of the electrolyte may be injected once, but it is preferable to inject the electrolyte in two or more portions. In the case of injecting two or more times, each liquid may have the same composition but different compositions (for example, after injecting a non-aqueous solvent or a solution in which a lithium salt is dissolved in a non-aqueous solvent, a non-aqueous solution having a higher viscosity than the solvent may be used). A solution in which a lithium salt is dissolved in a solvent or a non-aqueous solvent is injected). Further, in order to shorten the injection time of the electrolyte solution, the pressure of the battery can may be reduced, or a centrifugal force or an ultrasonic wave may be applied to the battery can.

Preferred carbon materials used for the negative electrode of the present invention are a non-graphitizable carbon material and a graphite-based carbon material, and carbon materials having a specified interplanar spacing, density and crystallite size (JP-A-62-122). , 066, JP-A-2-66,856.
Nos. 3-245,473), a mixture of natural graphite and artificial graphite (JP-A-5-290,844), and a vapor-grown carbon material (JP-A-63-24,555, 63-13). 2
No. 82, 63-58, 763, JP-A-6-212,
No. 617), a mesophase carbon material synthesized by pitch firing (JP-A-5-307,957 and JP-A-5-30).
7,958, 7-85,862, 8-315,
No. 820), graphite having a coating layer (JP-A-6-84,5).
No. 16).

Further, as a carbon material, a carbon material obtained by calcining furfuryl alcohol resin (PFA) alone or together with a phosphorus compound / boron compound in an inert atmosphere (Mio Nishi: Journal of the Japan Energetic Society, Vol. 71, 828)
P. 1992), a non-graphitizable carbon material obtained by firing coal tar pitch to which para-xylylene glycol is added in an inert atmosphere, and a polyacene-like structure obtained by firing a phenol resin in an inert atmosphere. A non-graphitizable carbon material having a carbonaceous material (JR Dahn et al., Carbon, 34, 1501, 1996) and mesocarbon microbeads (MCMB) under an inert atmosphere under a 100
Amorphous carbon material obtained by firing at 0 ° C. or less (Journal of Electrochemical Society, 142
Vol. 1041, 1995), an amorphous carbon material obtained by firing polyparaphenylene at 1000 ° C. or lower in an inert atmosphere (Morino Endo et al., Carbon, 155, 315)
Pp. 1992).

Further, in combination with the carbon material, a non-oxide material such as silicon, germanium, tin or lead, an inorganic oxide or an inorganic chalcogenide capable of forming an intermetallic compound in which lithium and lithium are ionized is used. It is also possible.

The positive electrode active material used in the present invention is a lithium-containing transition metal composite oxide capable of reversibly inserting and releasing lithium ions.

Preferred lithium-containing transition metal composite oxides include lithium, Ti, V, Cr,
Oxide containing at least one element selected from Mn, Fe, Co, Ni, Cu, Mo and W
138, 131, 58-220, 362, 62
-256,371, 62-90,863, 62
-264,560, 63-114,065, 6
Nos. 3-121,258, 63-211,565 and 62-176,054). Alkali metals other than lithium (first (IA) of the periodic table)
Group, element of group II (IIA)) and / or Al,
Ga, In, Ge, Sn, Pb, Sb, Bi, Si,
P, B, etc. may be contained. The mixing amount is preferably 0 to 30 mol% based on the transition metal.

Further preferred as the lithium-containing transition metal composite oxide positive electrode active material used in the present invention is L.
_{i x MO 2 (M = Co} , Ni, at least one atom selected from Fe and Mn, x = 0.02 to 1.2) material or LiyMn ₂ O ₄ containing (y = 0.02 or more 2 This is a material having a spinel structure represented by the following formula: The former is specifically Li _x CoO ₂ , Li _x NiO ₂ ,
Li _x MnO ₂ , Li _x Co _j Ni _1-j O ₂ (where x =
0.02 to 1.2, j = 0.1 to 0.9). Here, the above-mentioned x value is a value before the start of charge / discharge, and increases / decreases due to charge / discharge.

The electrode mixture of the present invention contains a conductive agent, a binder, and a filler in addition to the active material. The conductive agent may be any electronic conductive material that does not cause a chemical change in the configured battery. Usually, natural graphite (flaky graphite, flaky graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black,
Carbon fibers, metal powders (copper, nickel, aluminum, silver, etc. (JP-A-63-148554)), metal fibers or polyphenylene derivatives (JP-A-59-20,97)
No. 1) or a mixture thereof. A combination of graphite and acetylene black is particularly preferred. The addition amount is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight. For carbon and graphite, 2 to 15% by weight is particularly preferred.

In the present invention, an aprotic organic solvent and a lithium salt are used as a binder for holding the electrode mixture, but a fluororubber and an ethylene-propylene-dientene which have an affinity for an electrolytic solution are used. Polymers such as polymer (EPDM), polyvinylpyrrolidone, ethylene-propylene-diene terpolymer (EPDM), styrene-butadiene rubber, polybutadiene and the like can be used alone or as a mixture thereof. The addition amount of the binder is preferably 1 to 30% by weight, particularly preferably 2 to 10% by weight.

As the filler, any fibrous material that does not cause a chemical change in the constructed battery can be used. Usually, fibers such as olefin-based polymers such as polypropylene and polyethylene, glass, and carbon are used. Although the amount of the filler is not particularly limited,
~ 30% by weight is preferred.

As the positive / negative current collector, an electron conductor which does not cause a chemical change in the constructed battery is used. As the current collector of the positive electrode, in addition to aluminum, stainless steel, nickel, titanium, and the like, those obtained by treating the surface of aluminum or stainless steel with carbon, nickel, titanium, or silver are preferable, and aluminum and aluminum alloys are particularly preferable. It is. As the current collector of the negative electrode, copper, stainless steel, nickel, titanium is preferable,
Particularly preferred is copper or a copper alloy.

The shape of the current collector is usually a film sheet, but a net, a punched material, a lath, a porous material, a foam, a molded product of a fiber group and the like can also be used. . The thickness is not particularly limited, but is 1 to 500
μm. It is also desirable that the surface of the current collector be made uneven by surface treatment.

Examples of the coating method include a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. Among them, a blade method, a knife method and an extrusion method are preferred. The coating is preferably performed at a speed of 0.1 to 100 m / min. At this time, by selecting the above coating method in accordance with the solution physical properties and drying properties of the mixture, a good surface state of the coated layer can be obtained.
The coating may be performed on one side at a time or on both sides simultaneously.

The coating may be continuous, intermittent, or striped. The thickness, length and width of the coating layer are determined by the shape and size of the battery, but the thickness of the coating layer on one side is
In a compressed state after drying, the thickness is preferably 1 to 2000 μm.

The method for drying and dehydrating the electrode sheet coating material is as follows.
Hot air, vacuum, infrared rays, far-infrared rays, electron beams and low-humidity air can be used alone or in combination. The drying temperature is preferably in the range of 80 to 350 ° C, particularly 100 to 350 ° C.
A range of 250 ° C. is preferred. The water content is 20
It is preferably at most 00 ppm, and more preferably at most 500 ppm for each of the positive electrode mixture, the negative electrode mixture and the electrolyte. As a method for pressing the sheet, a method generally used can be used, but a calendar press method is particularly preferable. The pressing pressure is not particularly limited, but is 0.2 to 3 t.
/ Cm ² is preferred. The press speed of the calender press method is preferably 0.1 to 50 m / min, and the press temperature is room temperature to
200 ° C. is preferred. The ratio of the negative electrode sheet width to the positive electrode sheet is preferably 0.9 to 1.1, and more preferably 0.95 to 1.0.
Is particularly preferred. The content ratio between the positive electrode active material and the negative electrode material is
It depends on the compound type and the mixture formulation.

The separator of the present invention needs to have a function of closing the above-mentioned gap at 80 ° C. or higher to increase the resistance and cut off the electric current in order to ensure safety.
The temperature is preferably from 0 ° C to 180 ° C.

The shape of the pores of the separator is usually circular or elliptical, and the size is 0.05 μm to 30 μm.
1 μm to 20 μm is preferred. Further, as in the case of making by a stretching method or a phase separation method, the holes may be rod-shaped or amorphous. The ratio occupied by these gaps, that is, the porosity is 20
% To 90%, preferably 35% to 80%. These separators may be a single material such as polyethylene or polypropylene, or a composite material of two or more. In particular, those obtained by laminating two or more kinds of microporous films having different pore diameters, porosity, and pore closing temperatures are particularly preferable.

The battery can and the battery lid which can be used in the present invention are made of nickel-plated iron steel plate or stainless steel plate (SUS304, SUS304L, SUS304).
N, SUS316, SUS316L, SUS430, S
US444, etc.), nickel-plated stainless steel plate (same as above), aluminum or its alloy, nickel,
They are titanium and copper, and have a shape of a perfect circular cylinder, an elliptical cylinder, a square cylinder, or a rectangular cylinder. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel plate or a nickel-plated iron steel plate is preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel plate, aluminum or an alloy thereof is preferable. The shape of the battery can may be any of buttons, coins, sheets, cylinders, corners, and the like.

In order to prevent an internal pressure rise or a runaway reaction due to an abnormal reaction in the battery, it is preferable to incorporate a valve element and a current cutoff element. In particular, it is more preferable to incorporate a valve body that opens the internal pressure by breaking the valve due to an increase in the internal pressure and a current cutoff switch that operates in response to the displacement of the valve body in the sealing part. These pressure-sensitive valve bodies and current cutoff switches are disclosed in JP-A-2-112151,
JP-A-288063, JP-A-6-215760, and JP-A-9-92334 can be used. In addition, various conventionally known safety elements (for example, fuse, bimetal,
PTC element).

For the lead plate used in the present invention, a metal having electrical conductivity (for example, iron, nickel, titanium, chromium, molybdenum, copper, aluminum, etc.) or an alloy thereof can be used. Battery lid, battery can, electrode sheet,
As a method for welding the lead plate, a known method (eg, DC or AC electric welding, laser welding, ultrasonic welding) can be used. A conventionally known compound or mixture such as asphalt can be used as the sealing agent for sealing.

For the can or the lead plate, a metal or alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum or alloys thereof are used.

The gaskets usable in the present invention are olefin polymers, fluorine polymers, cellulose polymers, polyimides and polyamides, and olefin polymers are preferred from the viewpoint of organic solvent resistance and low moisture permeability. Propylene-based polymers are preferred. Further, it is preferably a block copolymer of propylene and ethylene.

The application of the non-aqueous secondary battery of the present invention is not particularly limited. For example, when the non-aqueous secondary battery is mounted on an electronic device, it is used in a notebook computer, pen input personal computer, mobile personal computer, electronic book player, mobile phone, cordless phone handset. ,
Pager, handy terminal, mobile fax,
Portable copy, portable printer, headphone stereo,
Video movies, LCD TVs, handy cleaners,
Portable CD, mini disk, electric shaver, transceiver, electronic organizer, calculator, memory card, portable tape recorder, radio, backup power supply, memory card, and the like. Other consumer products include motors, lighting equipment, toys, game machines, road conditioners, watches, strobes, cameras, medical equipment (pacemakers, hearing aids, shoulder massagers, etc.). Furthermore, it can be combined with a solar cell.

[0059]

The present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the examples unless it exceeds the gist of the invention.

[Preparation Example of Multilayer Negative Electrode Sheet Attached with Li Foil-1]
190 g of natural graphite (C-1), 30 g of artificial graphite as a conductive agent, and 9 g of polyvinylidene fluoride as a binder N-
The mixture was kneaded with 500 ml of methylpyrrolidone as a medium to obtain a negative electrode mixture slurry. Next, α-alumina 45 parts by weight, graphite 7 parts by weight, polyvinylidene fluoride 3 parts by weight, N
-Methylpyrrolidone was mixed at a ratio of 100 parts by weight to obtain an auxiliary layer slurry. The negative electrode mixture slurry is applied as a lower layer and the auxiliary layer slurry is applied as an upper layer on both sides of a copper foil having a thickness of 18 μm using a blade coater. A negative electrode sheet precursor was prepared. This was cut into a length of 540 mm, and a nickel lead plate was welded to the end, and then heat-treated at 230 ° C. in dry air having a dew point of −40 ° C. or less using a far-infrared heater for 1 hour. A 35 μm-thick striped lithium foil (purity 99.8) cut to 4 mm width × 52 mm length on both surfaces of the negative electrode sheet precursor after the heat treatment.
%) Were adhered at 90 mm intervals at right angles to the length of the negative electrode sheet precursor to prepare a negative electrode sheet ANL-1 shown in Table 1.

[Example of preparing a multilayer negative electrode sheet with Li foil attached-2]
Japanese Patent Application Laid-Open No. 5-182,66 instead of natural graphite (C-1)
No. 4 (C-2), JP-A-7-85,8
No. 62, a microfiber material obtained by firing a mesoface pitch (C-3), and a vapor-grown carbon (C-4) described in JP-A-63-58,763, using a Li foil laminated multilayer. Similarly to the negative electrode sheet preparation example-1, a negative electrode sheet precursor was prepared, and similarly, a nickel lead plate was welded to an end portion, and a lithium foil (purity: 99.8%) was added to the negative electrode sheet precursor. Then, negative electrodes ANL-2, ANL-3, and A-4 shown in Table 1 were prepared by pasting the films in a stripe shape at right angles.

[Preparation Example of Multilayer Negative Electrode Sheet without Bonding Li Foil] Further, a negative electrode sheet AN- for a battery of a comparative example described later.
1, 2, 3, and 4 were prepared. That is, a thickness of 136 μm, which was compression-molded in Li foil-attached multilayer negative electrode sheet preparation examples-1 and 2.
After cutting a negative electrode sheet precursor of mx 55 mm in width to 540 mm in length, and welding a lead plate made of nickel to the end, the dew point-
Heat treatment was performed for 1 hour at 230 ° C. using a far-infrared heater in dry air of 40 ° C. or less to obtain negative sheets AN-1, 2, 3, and 4 shown in Table 1 without attaching a lithium foil.

[0063]

[Table 1]

[Positive electrode sheet preparation example-1] Positive electrode active material Li
200 g of CoO ₂ and 10 g of acetylene black were mixed with a homogenizer, followed by 5 g of polyvinylidene fluoride as a binder, and N-methyl 2-pyrrolidone 500 g was mixed.
The mixture was kneaded and mixed to prepare a positive electrode mixture paste.
The positive electrode mixture paste was applied to both surfaces of a 30-μm-thick aluminum foil current collector with a blade coater, dried at 150 ° C., compression-molded with a roller press, and cut into a predetermined size to form a belt-shaped positive electrode sheet. Furthermore, in a dry box (dew point; dry air of -50 ° C or less), dehydration and drying are sufficiently performed using a far-infrared heater, and this is cut into a length of 495 mm, and an aluminum lead plate is welded to an end portion to a thickness of 165 μm.
m, a positive electrode sheet having a width of 53.5 mm and a length of 495 mm was prepared (CA-1).

[Electrolyte Preparation Example-1] Next, a 65.3 cc polypropylene container was placed in an argon atmosphere at 65.3.
g of diethyl carbonate.
22.2 g of ethylene carbonate were dissolved little by little, taking care not to exceed. Next, 0.8 g of 1,2-bis (ethoxycarbonyl) -1,2-dimethylhydrazine is dissolved, and then 0.4 g of LiBF ₄ , 1
A small amount of 2.1 g of LiPF ₆ was sequentially dissolved in the above-mentioned polypropylene container, respectively, while taking care that the liquid temperature did not exceed 30 ° C. The obtained electrolyte had a specific gravity of 1.135.
Was a colorless and transparent liquid (Table 2: S11). 1 water
8 ppm (measured using a Karl Fischer moisture analyzer, trade name: MKC-210, manufactured by Kyoto Electronics Co.), the free acid content is 24 pp
m (bromthymol blue as indicator, 0.1N
(measured by neutralization titration using an aOH aqueous solution).

[Electrolyte Preparation Example-2] The following seven types of electrolytes S12 and S1 shown in Table 2 were prepared in the same procedure as in Electrolyte Preparation Example-1.
3, 14, 15, 16, 17, and 18 were produced.

[Examples of Preparation of Electrolyte Solution for Comparative Example] Further, three types of electrolyte solutions S21, 25, and 28 (Table 2) containing no additive of the present invention were prepared as electrolyte solutions for a comparative example described later.

[0068]

[Table 2]

Example 1 A method of manufacturing a cylindrical battery will be described with reference to FIG. The Li foil-laminated multilayer negative electrode sheet and positive electrode sheet were each dehydrated and dried at 230 ° C. for 30 minutes in dry air having a dew point of −40 ° C. or less. In a dry atmosphere, a dehydrated and dried positive electrode sheet (CA-1) (1),
Microporous polyethylene film separator (3), dehydrated and dried Li foil-laminated multilayer negative electrode sheet (ANL-1)
(2) The separator (3) was further laminated in this order, and this was spirally wound. The wound electrode group was housed in a nickel-plated iron bottomed cylindrical battery can (4) also serving as a negative electrode terminal. Further, the electrolyte solution (S11) prepared in the electrolyte solution preparation example was injected into the battery can. The battery lid having the positive electrode terminal was swaged via the gasket (6) to produce a cylindrical battery (B-1). The battery cover (5) serving as the positive electrode terminal was connected to the positive electrode sheet (1), and the battery can (4) was connected to the negative electrode sheet (2) by a lead terminal in advance. still,
(7) is a safety valve. Then, after leaving at 40 ° C. for 7 days, the following performance evaluation was performed.

The manufactured cylindrical battery (B-1) is charged at 1.2 A at normal temperature. In this case, charging is performed at a constant current up to 4.2 V, and the charging current is controlled so as to keep the voltage constant at 4.2 V until 2.5 hours have elapsed from the start of charging. The discharge was performed at a constant current up to 2.8 V at 1.2 A. The ratio of the charge capacity to the discharge capacity at this time is defined as Coulomb efficiency.
Thereafter, under the same charge / discharge conditions, the charge end voltage was 4.2 V,
The battery is charged and discharged at a discharge end voltage of 2.8 V and 1.2 A, and the value of the fifth cycle at that time is defined as the discharge capacity. In addition, the capacity maintenance ratio is defined as the capacity maintenance ratio at the 200th cycle in which charging and discharging are repeated. Table 3 shows the results of the Coulomb efficiency, the discharge capacity, and the capacity retention rate at the 200th cycle.

Example 2 As in Example 1, Li
Cylindrical batteries B-2 to 12 were prepared by combining the foil-attached multilayer negative electrode sheet, positive electrode sheet, and electrolyte as shown in Table 3, and the results of Coulomb efficiency, discharge capacity, and capacity retention at the 200th cycle were shown in Table 3. Show.

[0072]

[Table 3]

[Comparative Example 1] Using a negative electrode sheet (AN-1), a microporous polyethylene film separator and a positive electrode sheet having a width of 53.5 mm and a length of 495 mm in a dry atmosphere in the same manner as in Example 1. Table 4 shows the results of evaluating the coulomb efficiency, the discharge capacity, and the capacity retention at the 200th cycle under the same conditions as in Example 1 after preparing the cylindrical battery BR-1 in which the electrolytic solution (S21) was combined.

Comparative Example 2 Using a negative electrode sheet AN-1, similarly to Example 1, a microporous polyethylene film separator, 53.5 mm in width × 4 in length in a dry atmosphere
Table 4 shows the results of evaluating cylindrical batteries BR-2 to BR-7 obtained by combining a 95 mm positive electrode sheet and an electrolytic solution as shown in Table 4, and evaluating the Coulomb efficiency, the discharge capacity, and the capacity retention at the 200th cycle.

[0075]

[Table 4]

The battery (B-1) of Example 1 using the multilayered negative electrode sheet with Li foil of the present invention and an electrolyte containing at least one hydrazine derivative and / or aromatic compound as an additive is a comparative example. Comparing the performance of the battery No. 1 (BR-1), the coulomb efficiency was improved and the discharge capacity was 10%.
It has improved. Battery of Example 2 (B-2 to B-1
As for 2), when the performances of the batteries (BR-2, 3) of Comparative Example 2 are compared, improvements in coulomb efficiency and discharge capacity are similarly observed.

Except for using S21 in which the electrolyte does not contain a hydrazine derivative and / or an aromatic compound, the battery BR-6 of Comparative Example-2, which has the same configuration as Example-1 of the present invention, , The coulomb efficiency and the discharge capacity are better than those of BR-1, 2, and 3 of Comparative Example 2, but the battery of Example 1 (B
In order to improve the discharge capacity, the combined use of the Li foil-laminated multilayer negative electrode sheet and an electrolyte containing at least one hydrazine derivative and / or an aromatic compound as an additive is not sufficient. It indicates that it is necessary.

In order to improve the low-temperature characteristics of the battery, the electrolytes S15 to S1 were obtained by partially replacing ethylene carbonate used as the electrolyte solvent with propylene carbonate.
8, S25 and 28, the batteries (B-9 to 12) of Experimental Example 2 did not show significant reductions in Coulomb efficiency and discharge capacity, whereas the batteries of Comparative Example 2 (BR-4,
In 5, 5), Coulomb efficiency and discharge capacity were significantly reduced (charge and discharge became impossible by the 200th cycle).
The effect of the electrolyte additive of a non-aqueous secondary battery in which propylene carbonate is contained in the electrolyte and the negative electrode material is natural graphite is shown.

The positive electrode active material LiCoO ₂ is converted to LiNiO ₂ or L
Similar effects were obtained by changing to iMn ₂ O ₄ .

[0080]

According to the present invention, a high-capacity nonaqueous secondary battery in which lithium is previously supported on a carbon anode material can be provided.

[Brief description of the drawings]

FIG. 1 shows a conceptual diagram of a cylindrical battery used in Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode sheet 2 Negative electrode sheet 3 Separator 4 Battery can 5 Battery lid 6 Gasket 7 Safety valve

Continued on front page F-term (reference) CJ22 DJ01 DJ04 DJ09 DJ16 DJ17 EJ13 HJ02

Claims (11)

[Claims] 1. A non-aqueous electrolyte comprising a positive electrode sheet containing a positive electrode active material mainly composed of a lithium-containing transition metal composite oxide, a negative electrode sheet containing a carbon material capable of inserting and extracting lithium, and a non-aqueous electrolyte containing a lithium salt. In the water secondary battery, the negative electrode sheet has an auxiliary layer, a metal foil mainly composed of lithium is preliminarily attached to the negative electrode sheet through the auxiliary layer, and at least a non-aqueous electrolyte is used as an additive. A non-aqueous secondary battery comprising one kind of hydrazine derivative and / or aromatic compound. 2. The method according to claim 1, wherein the auxiliary layer includes water-insoluble particles, and the water-insoluble particles are a mixture of conductive particles and particles having substantially no conductivity. Non-aqueous secondary battery. 3. The non-aqueous secondary according to claim 1, wherein the carbon material used for the negative electrode sheet contains at least one of a non-graphitizable carbon material and a graphite-based carbon material. battery. 4. The hydrazine derivative contained in the non-aqueous electrolyte is substituted with an alkyl group, an aryl group, a heterocyclic group, an acyl group, an oxycarbonyl group, or a sulfonyl group. 4. The non-aqueous secondary battery according to any one of claims 1 to 3. 5. The aromatic compound additive contained in the non-aqueous electrolyte has a cyclic structure containing at least one atom selected from O, N and S. The non-aqueous secondary battery according to any one of the above. 6. The additive for an aromatic compound contained in the non-aqueous electrolyte has an aromatic ring containing at least one atom selected from O, N and S or an aromatic ring containing a cyclic carbonate. The non-aqueous secondary battery according to claim 1. 7. The non-aqueous electrolyte contains propylene carbonate as a solvent.
7. The non-aqueous secondary battery according to any one of 6. 8. The method according to claim 1, wherein the positive electrode active material is Li _x MO ₂ (M = C
a material containing at least one atom selected from o, Ni, Fe and Mn, x = 0.02 or more and 1.2 or less, and Li _y Mn ₂ O ₄ (y = 0.02 or more and 2 or less) At least one selected from materials having a spinel structure
The non-aqueous secondary battery according to claim 1, wherein a seed is used. 9. A method for producing a non-aqueous secondary battery comprising a negative electrode sheet, a positive electrode sheet, a non-aqueous electrolyte containing a lithium salt and a separator including a layer mainly composed of a carbon material capable of occluding and releasing lithium, a) the negative electrode sheet has at least one auxiliary layer containing water-insoluble particles, and a lithium-based metal material is superimposed on the auxiliary layer; b) at least one non-aqueous electrolyte as an additive A) a hydrazine derivative and / or an aromatic compound, and c) after aging after assembling the battery,
A method for producing a non-aqueous secondary battery, wherein lithium is inserted into a negative electrode sheet. 10. The non-aqueous non-aqueous battery according to claim 9, wherein the pattern in which the lithium-based metal material is superimposed is at least one of a stripe pattern, a frame pattern, and a disc pattern on the entire surface of the negative electrode sheet. Manufacturing method of secondary battery. 11. The method for manufacturing a non-aqueous secondary battery according to claim 9, wherein the auxiliary layer contains water-insoluble conductive particles.