JP2003187864A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery which is capable of improving its characteristics such as a discharge capacity and a charge-discharge cycle characteristic by improving a chemical stability of an electrolyte. <P>SOLUTION: This battery comprises wound electrode bodies 20 in which adjacent electrodes of a positive one 21 and a negative one 22 are wound with the separator 23 sandwiched in between. And the negative electrode 22 is made to extract a lithium metal while being charged and its volume is represented by addition of a volume constituent induced by occlusion and separation and a volume constituent induced by extraction and dissolution. Further, the separator 23 is impregnated with an electrolyte in whose solvent lithium base is dissolved, and as the electrolyte is added with a crown ether group or a grime group, stable coatings of an ether family are formed on the surfaces of the negative electrodes. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery provided with an electrolyte together with a positive electrode and a negative electrode, and in particular, the capacity of the negative electrode is the sum of a capacity component due to occlusion and release of light metal and a capacity component due to precipitation and dissolution of light metal. With respect to the battery represented by.

[0002]

2. Description of the Related Art Recently, mobile phones, PDAs (personal digs)
Ital assistants (personal portable information terminal devices) or portable electronic devices typified by notebook computers are being actively reduced in size and weight. It is strongly desired to improve the energy density of secondary batteries.

As a secondary battery capable of obtaining a high energy density, for example, there is a lithium ion secondary battery using a material such as a carbon material capable of inserting and extracting lithium (Li) in a negative electrode. In a lithium ion secondary battery, since the lithium occluded in the negative electrode material is designed to always be in the ionic state, the energy density greatly depends on the number of lithium ions that can be occluded in the negative electrode material. Therefore, in the lithium ion secondary battery, it is considered that the energy density can be further improved by increasing the storage amount of lithium ions.
However, the storage capacity of graphite, which is currently considered to be the material capable of storing and releasing lithium ions most efficiently, has a theoretical limit of 372 mAh in terms of the amount of electricity per gram, and recently it has been energetic. It is being raised to the limit by development activities.

As a secondary battery capable of obtaining a high energy density, there is also a lithium secondary battery which uses lithium metal for the negative electrode and utilizes only the precipitation and dissolution reaction of lithium metal for the negative electrode reaction. The lithium secondary battery has a theoretical electrochemical equivalent of lithium metal of 2054 mAh / cm ^3.
Since it corresponds to 2.5 times that of graphite used in a lithium ion secondary battery, it is expected to obtain a higher energy density than that of a lithium ion secondary battery. Until now, many researchers have conducted research and development on practical application of lithium secondary batteries (eg, Lithium Batteries, edited by Jean-Paul Gabano, Academic
Press, 1983, London, New York).

However, the lithium secondary battery has a problem that it is difficult to put it into practical use because the discharge capacity thereof is largely deteriorated when charging and discharging are repeated. This capacity deterioration is based on the fact that the lithium secondary battery utilizes the precipitation / dissolution reaction of lithium metal in the negative electrode, and the volume of the negative electrode corresponds to the lithium ions that move between the positive and negative electrodes as they are charged and discharged. Is greatly increased or decreased by the amount of the capacity, so that the volume of the negative electrode is largely changed, and the dissolution reaction and recrystallization reaction of the lithium metal crystal are difficult to reversibly proceed. Moreover, the volume change of the negative electrode becomes large as the high energy density is achieved, and the capacity deterioration becomes more remarkable.

Therefore, the present inventors newly developed a secondary battery in which the capacity of the negative electrode is represented by the sum of the capacity component due to occlusion and desorption of lithium and the capacity component due to precipitation and dissolution of lithium (International Publication See WO 01/22519 A1 pamphlet). This is one in which a carbon material capable of inserting and extracting lithium is used for the negative electrode, and lithium is deposited on the surface of the carbon material during charging. According to this secondary battery, it is expected that the cycle characteristics are improved while achieving high energy density.

[0007]

However, in order to put this secondary battery into practical use, it is necessary to further improve and stabilize its characteristics.
R & D on electrolytes is also essential. In particular, if a side reaction occurs between the electrolyte and the electrode and the side reaction product is deposited on the surface of the electrode, the internal resistance of the battery increases, and the cycle characteristics deteriorate significantly. Further, if lithium is consumed at that time, it may cause deterioration of capacity. That is, the chemical stability of the electrolyte is a very important issue.

The present invention has been made in view of the above problems, and an object thereof is to provide a battery capable of improving the chemical stability of an electrolyte and improving battery characteristics such as discharge capacity and cycle characteristics. Especially.

[0009]

A battery according to the present invention comprises a positive electrode, a negative electrode and an electrolyte, and the capacity of the negative electrode is a capacity component due to occlusion and release of light metal,
It is represented by the sum of the light metal deposited and dissolved by the capacitive component, and the electrolyte contains at least one member selected from the group consisting of crown ethers and glymes.

In the battery according to the present invention, since the electrolyte contains at least one member selected from the group consisting of crown ethers and glymes, these are adsorbed on the surface of the negative electrode, and the solvent is charged into the negative electrode. Turcaration is suppressed and the reaction between the precipitated light metal and the solvent is prevented. Therefore, the chemical stability of the electrolyte is high, a high discharge capacity is obtained, and the cycle characteristics and the like are improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
2 shows a cross-sectional structure of the secondary battery according to the embodiment of FIG. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a strip-shaped positive electrode 21 and a negative electrode 22 are wound via a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 is arranged so as to sandwich the spirally wound electrode body 20 perpendicularly to the spirally wound peripheral surface.

A battery lid 14 is provided at the open end of the battery can 11.
And a safety valve mechanism 15 provided inside the battery lid 14.
And PTC (Positive Temperature Coefficie)
nt; PTC element) 16 is attached by being caulked via a gasket 17,
The inside of is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the PTC element 16, and the disk plate 15a is inverted when the internal pressure of the battery exceeds a certain level due to an internal short circuit or heating from the outside. Then, the electrical connection between the battery lid 14 and the spirally wound electrode body 20 is cut off. PTC element 1
When the temperature rises, the resistance 6 increases the resistance value to limit the current and prevent abnormal heat generation due to a large current, and is made of, for example, barium titanate-based semiconductor ceramics. The gasket 17 is made of, for example, an insulating material, and its surface is coated with asphalt.

The wound electrode body 20 is wound around a center pin 24, for example. Positive electrode 2 of wound electrode body 20
1 is a positive electrode lead 2 made of aluminum (Al) or the like
5 is connected, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded and electrically connected to the battery can 11.

FIG. 2 is an enlarged view of a part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode mixture layer 21b is provided on both surfaces of a positive electrode current collector 21a having a pair of opposing surfaces. Although not shown, the positive electrode mixture layer 21b may be provided only on one surface of the positive electrode current collector 21a. Positive electrode current collector 21a
Has a thickness of, for example, about 5 μm to 50 μm and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode mixture layer 21b has, for example, a thickness of 80 μm to 250 μm, and is configured to include a positive electrode material capable of inserting and extracting lithium which is a light metal. The thickness of the positive electrode mixture layer 21b is the total thickness of the positive electrode mixture layer 21b when the positive electrode mixture layer 21b is provided on both surfaces of the positive electrode current collector 21a.

Capable of inserting and extracting lithium
Examples of positive electrode materials include lithium oxide and lithium
Lithium sulfide or intercalation compounds containing lithium
Umium-containing compounds are suitable, and two or more of these are mixed.
You may use it. Especially for increasing the energy density
Is the general formula Li_xMO₂Lithium composite oxide represented by
Alternatively, an intercalation compound containing lithium is preferable. Na
Note that M is preferably one or more kinds of transition metals, specifically
Is cobalt (Co), nickel, manganese (Mn),
Iron (Fe), aluminum, vanadium (V) and chi
At least one of tan (Ti) is preferable. x
Depends on the charge / discharge state of the battery and is usually 0.05
It is a value within the range of ≦ x ≦ 1.10. In addition,
LiMn having a pinel type crystal structure₂O_FourOr
LiFePO having a Livin type crystal structure _FourAnd so on
It is preferable because the energy density can be obtained.

Such a positive electrode material includes, for example, lithium carbonate, nitrate, oxide or hydroxide;
Prepared by mixing transition metal carbonates, nitrates, oxides or hydroxides so as to have a desired composition, pulverizing, and then firing in an oxygen atmosphere at a temperature in the range of 600 ° C to 1000 ° C. To be done.

The positive electrode mixture layer 21b also contains, for example, a conductive agent, and may further contain a binder if necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black and Ketjen black, and one kind or a mixture of two or more kinds thereof is used. In addition to the carbon material, a metal material, a conductive polymer material, or the like may be used as long as the material has conductivity. Examples of the binder include synthetic rubbers such as styrene-butadiene rubber, fluorine-based rubber or ethylene propylene diene rubber, and polymer materials such as polyvinylidene fluoride. One or more of them are mixed. Used. For example, in the case where the positive electrode 21 and the negative electrode 22 are wound as shown in FIG. 1, it is preferable to use styrene-butadiene rubber or fluorine rubber having a high flexibility as a binder.

The negative electrode 22 has, for example, a structure in which a negative electrode mixture layer 22b is provided on both surfaces of a negative electrode current collector 22a having a pair of opposing surfaces. Although not shown, the negative electrode mixture layer 22b may be provided only on one surface of the negative electrode current collector 22a. The negative electrode current collector 22a is composed of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil having good electrochemical stability, electrical conductivity and mechanical strength. In particular, copper foil is most preferable because it has high electrical conductivity. The thickness of the negative electrode current collector 22a is preferably, for example, about 6 μm to 40 μm. 6μ
This is because if it is thinner than m, the mechanical strength is lowered, the negative electrode current collector 22a is easily broken in the manufacturing process, and the production efficiency is lowered. If it is thicker than 40 μm, the negative electrode current collector 22a in the battery is The volume ratio becomes larger than necessary,
This is because it becomes difficult to increase the energy density.

The negative electrode mixture layer 22b is composed of one or more negative electrode materials capable of inserting and extracting lithium, which is a light metal, and may include, for example, a positive electrode mixture as necessary. The same binder as that of the agent layer 21b may be included. The thickness of the negative electrode mixture layer 22b is, for example, 8
It is 0 μm to 250 μm. This thickness is the negative electrode mixture layer 2
When 2b is provided on both surfaces of the negative electrode current collector 22a, it is the total thickness thereof.

In the present specification, occlusion / desorption of light metal means that light metal ion is electrochemically occluded / desorbed without losing its ionicity. This includes not only the case where the occluded light metal exists in a perfect ionic state, but also the case where it exists in a state that cannot be said to be a perfect ionic state. Examples of cases corresponding to these include storage of light metal ions with respect to graphite by an electrochemical intercalation reaction. Further, occlusion of a light metal in an alloy containing an intermetallic compound, or occlusion of a light metal by forming an alloy can be mentioned.

Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. These carbon materials are preferable because the change in the crystal structure that occurs during charging / discharging is very small, a high charge / discharge capacity can be obtained, and good cycle characteristics can be obtained. Particularly, graphite is preferable because it has a large electrochemical equivalent and can obtain a high energy density.

As the graphite, for example, the true density is 2.10.
It is preferably g / cm ³ or more, 2.18 g / cm ³
The above is more preferable. In order to obtain such a true density, the C-axis crystallite thickness of the (002) plane is 1
It needs to be 4.0 nm or more. In addition, (00
2) The surface spacing is preferably less than 0.340 nm, and more preferably 0.335 nm or more and 0.337 nm or less.

The graphite may be natural graphite or artificial graphite.
The artificial graphite can be obtained, for example, by carbonizing an organic material, subjecting it to high-temperature heat treatment, and crushing and classifying. The high temperature heat treatment, for example, carbonizes at 300 ° C. to 700 ° C. in an inert gas stream such as nitrogen (N ₂ ) if necessary,
The temperature is raised from 900 ° C. to 1500 ° C. at a rate of 1 ° C. to 100 ° C. per minute, and this temperature is maintained for about 0 to 30 hours for calcination, and at the same time, heated to 2000 ° C. or higher, preferably 2500 ° C. or higher It is performed by maintaining the temperature for an appropriate time.

As an organic material as a starting material, coal or pitch can be used. For pitch, for example, tars and asphalt obtained by pyrolyzing coal tar, ethylene bottom oil or crude oil at high temperature are distilled (vacuum distillation, atmospheric distillation or steam distillation), thermal polycondensation, extraction, There are those obtained by chemical polycondensation, those produced when wood is refluxed, polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate or 3,5-dimethylphenol resin.
These coals or pitches have a maximum of 400 during carbonization.
It exists as a liquid at about ℃, and when it is held at that temperature, the aromatic rings are condensed and polycyclic, and become in a laminated orientation state, and then become a solid carbon precursor, that is, semi-coke at about 500 ℃ or more. (Liquid phase carbonization process).

Examples of the organic material include condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphene and pentacene, or derivatives thereof (for example, carboxylic acid and carboxylic acid anhydride of the above compounds). , Carboxylic acid imide), or a mixture thereof. Further, condensed heterocyclic compounds such as acenaphthylene, indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine and phenanthridine, or derivatives thereof,
Alternatively, a mixture thereof can be used.

The crushing may be carried out either before or after carbonization or calcination, or during the heating process before graphitization. In these cases, the heat treatment for graphitization is finally performed in the powder state. However, in order to obtain a graphite powder having high bulk density and high fracture strength, the raw material is molded and then heat treated,
It is preferable to pulverize and classify the obtained graphitized molded body.

For example, in the case of producing a graphitized molded body, coke serving as a filler and binder pitch serving as a molding agent or a sintering agent are mixed and molded, and then the molded body is cooled to a temperature of 1000 ° C. or lower. After repeating the firing process of heat-treating and the pitch impregnation process of impregnating the fired body with the melted binder pitch several times, heat treatment is performed at high temperature. The impregnated binder pitch is carbonized and graphitized in the above heat treatment process. By the way, in this case,
Since filler (coke) and binder pitch are used as raw materials, they are graphitized as a polycrystalline body, and since sulfur and nitrogen contained in the raw materials are generated as a gas during heat treatment, minute holes are formed in the passage. It is formed. Therefore, the vacancy facilitates the lithium occlusion / desorption reaction and has the advantage of industrially high treatment efficiency. In addition, as a raw material of the molded body, the moldability itself,
A sinterable filler may be used. In this case, the use of binder pitch is unnecessary.

The non-graphitizable carbon has a (002) plane spacing of 0.37 nm or more and a true density of 1.70 g / cm 3.
A differential thermal analysis in air (differen of less than ³
Those that do not show an exothermic peak at 700 ° C. or higher in tialthermal analysis (DTA) are preferable.

Such non-graphitizable carbon can be obtained, for example, by subjecting an organic material to a heat treatment at about 1200 ° C., pulverizing and classifying. The heat treatment is, for example, 3 times as required.
After carbonization at 00 ° C to 700 ° C (solid phase carbonization process),
The temperature is raised from 900 ° C to 1300 ° C at a rate of 1 ° C to 100 ° C per minute, and the temperature is maintained for about 0 to 30 hours. The pulverization may be performed before or after carbonization or during the temperature rising process.

As the organic material as a starting material, for example, furfuryl alcohol or furfural polymer or copolymer, or furan resin which is a copolymer of these polymers and other resins can be used. . Also,
Phenolic resin, acrylic resin, vinyl halide resin, polyimide resin, polyamideimide resin, polyamide resin, conjugated resin such as polyacetylene or polyparaphenylene, cellulose or its derivatives, coffee beans, bamboo, shells containing chitosan, bacteria It is also possible to use biocelluloses utilizing Furthermore, the atomic number ratio H / H of hydrogen atoms (H) and carbon atoms (C)
It is also possible to use a compound in which a functional group containing oxygen (O) is introduced (so-called oxygen bridge) into petroleum pitch having C of, for example, 0.6 to 0.8.

The oxygen content in this compound is preferably 3% or more, and more preferably 5% or more (see JP-A-3-252053). The oxygen content affects the crystal structure of the carbon material, and at a content higher than this, the physical properties of the non-graphitizable carbon can be increased,
This is because the capacity of the negative electrode 22 can be improved.
Incidentally, petroleum pitch is, for example, tars obtained by pyrolyzing coal tar, ethylene bottom oil or crude oil at high temperature, or asphalt,
It can be obtained by distillation (vacuum distillation, atmospheric distillation or steam distillation), thermal polycondensation, extraction or chemical polycondensation. Further, as a method for forming oxidative cross-links, for example, nitric acid,
Wet method of reacting aqueous solution of sulfuric acid, hypochlorous acid or mixed acid thereof with petroleum pitch, dry method of reacting oxidizing gas such as air or oxygen with petroleum pitch, or sulfur, ammonium nitrate, ammonium persulfate, A method of reacting a solid reagent such as ferric chloride with petroleum pitch can be used.

The organic material used as the starting material is not limited to these, and any other organic material may be used as long as it is an organic material that can become non-graphitizable carbon through a solid phase carbonization process such as oxygen crosslinking treatment.

As the non-graphitizable carbon, in addition to those produced by using the above-mentioned organic material as a starting material, Japanese Patent Laid-Open No. 3-1
The compound containing phosphorus (P), oxygen and carbon as main components, which is described in Japanese Patent No. 37010, is preferable because it exhibits the above-mentioned physical property parameters.

As the negative electrode material capable of inserting and extracting lithium, a simple substance, an alloy or a compound of a metal element or a semi-metal element capable of forming an alloy with lithium can be mentioned. These are preferable because they can obtain a high energy density, and particularly when used together with a carbon material, it is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. In the present specification, the alloy includes not only an alloy composed of two or more kinds of metal elements but also an alloy composed of one or more kinds of metal elements and one or more kinds of metalloid elements. The texture may be a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a coexistence of two or more of them.

Examples of such metal elements or metalloid elements are tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi). ), Cadmium (C
d), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y)
Alternatively, hafnium (Hf) may be used. As these alloys or compounds, for example, chemical formulas Ma _s Mb _t
Examples include Li _u and those represented by the chemical formula Map _p Mc _q Md _r . In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and Mb represents lithium and Ma.
At least one of metal elements and metalloid elements other than
Represents a species, Mc represents at least one kind of non-metal element,
Md represents at least one of a metal element other than Ma and a metalloid element. The values of s, t, u, p, q and r are s> 0, t ≧ 0, u ≧ 0, p> 0 and q, respectively.
> 0 and r ≧ 0.

Among them, simple substances, alloys or compounds of 4B group metal elements or metalloid elements are preferable, and particularly preferable are silicon or tin, or alloys or compounds thereof. These may be crystalline or amorphous.

For such alloys or compounds
Physically, for example, LiAl, AlSb, CuMgS
b, SiB_Four, SiB₆, Mg₂Si, Mg₂Sn, N
i₂Si, TiSi₂, MoSi₂, CoSi₂, Ni
Si₂, CaSi₂, CrSi₂, Cu_FiveSi, FeS
i₂, MnSi₂, NbSi₂, TaSi₂, VS
i ₂, WSi₂, ZnSi₂, SiC, Si₃N_Four, S
i₂N₂O, SiO_v(0 <v ≦ 2), SnO_w(0 <
w ≦ 2), SnSiO₃, LiSiO or LiSn
There is O etc.

As the negative electrode material capable of inserting and extracting lithium, other metal compounds or polymer materials can be further cited. Other metal compounds include oxides such as iron oxide, ruthenium oxide and molybdenum oxide, LiN _{3 and the} like, and polymer materials include polyacetylene, polyaniline, polypyrrole and the like.

Further, in this secondary battery, lithium metal begins to deposit on the negative electrode 22 at the time when the open circuit voltage (ie, battery voltage) is lower than the overcharge voltage in the course of charging. That is, lithium metal is deposited on the negative electrode 22 in a state where the open circuit voltage is lower than the overcharge voltage, and the capacity of the negative electrode 22 is the capacity component due to occlusion / desorption of lithium and the capacity component due to precipitation / dissolution of lithium metal. It is expressed as the sum of. Therefore, in this secondary battery, both the negative electrode material capable of absorbing and desorbing lithium and the lithium metal function as a negative electrode active material, and the negative electrode material capable of absorbing and desorbing lithium is a base material when lithium metal is deposited. Has become.

The overcharge voltage refers to an open circuit voltage when the battery is in an overcharged state and is one of the guidelines set by the Japan Storage Battery Industry Association (Battery Industry Association), for example, "lithium". Secondary Battery Safety Evaluation Standard Guidelines "(S
"Full charge" as described and defined in BAG 1101)
Refers to a voltage higher than the open circuit voltage of the battery. In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, the standard charging method, or the recommended charging method used when the nominal capacity of each battery is obtained. Specifically, in this secondary battery, for example, a negative electrode that is fully charged when the open circuit voltage is 4.2 V and is capable of occluding and releasing lithium in a part within the range of the open circuit voltage of 0 V or more and 4.2 V or less. Lithium metal is deposited on the surface of the material.

As a result, in this secondary battery, a high energy density can be obtained, and at the same time, cycle characteristics and quick charge characteristics can be improved. This is similar to a conventional lithium secondary battery using lithium metal or a lithium alloy for the negative electrode in that lithium metal is deposited on the negative electrode 22, but lithium metal is deposited on the negative electrode material capable of inserting and extracting lithium. It is considered that this is because the following advantages are brought about by doing so.

First, in the conventional lithium secondary battery, it was difficult to deposit lithium metal uniformly, which caused deterioration of cycle characteristics. However, negative electrode materials capable of inserting and extracting lithium are generally used. Since the surface area is relatively large, lithium metal can be uniformly deposited in this secondary battery. Secondly, in the conventional lithium secondary battery, the volume change caused by the precipitation and dissolution of lithium metal was large, which also caused the deterioration of cycle characteristics. However, this secondary battery can store and release lithium. The lithium metal is also deposited in the gaps between the particles of the negative electrode material, so that the volume change is small. Thirdly, in the conventional lithium secondary battery, the larger the amount of deposited / dissolved lithium metal, the greater the above problem becomes. However, in this secondary battery, the lithium storage / desorption negative electrode material can absorb and absorb lithium. Since the detachment also contributes to the charge / discharge capacity, the amount of lithium metal deposited / dissolved is small in spite of the large battery capacity. Fourthly, in the conventional lithium secondary battery, when the rapid charging is performed, the lithium metal is more unevenly deposited, which further deteriorates the cycle characteristics. However, in this secondary battery, lithium is occluded in the initial stage of charging. -Since lithium is occluded in the detachable negative electrode material, rapid charging is possible.

In order to obtain these advantages more effectively, for example, the maximum deposition capacity of lithium metal deposited on the negative electrode 22 at the maximum voltage before the open circuit voltage becomes the overcharge voltage is such that lithium is absorbed or absorbed. It is preferable that the charge capacity of the removable negative electrode material is 0.05 times or more and 3.0 times or less. This is because if the amount of lithium metal deposited is too large, the same problem as in the conventional lithium secondary battery occurs, and if it is too small, the charge / discharge capacity cannot be sufficiently increased. Further, for example, the discharge capacity of the negative electrode material capable of inserting and extracting lithium is preferably 150 mAh / g or more. This is because the amount of lithium metal deposited is relatively smaller as the lithium occlusion / release capacity is larger. The charge capacity of the negative electrode material can be obtained, for example, from the amount of electricity when a negative electrode using lithium metal as a counter electrode and this negative electrode material as a negative electrode active material is charged to 0 V by a constant current / constant voltage method. The discharge capacity of the negative electrode material can be obtained, for example, from the amount of electricity when it is discharged to 2.5 V by a constant current method for 10 hours or more.

The separator 23 is composed of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene or polyethylene, or a porous film made of ceramic, and two or more kinds of these porous films are laminated. It may have a structure. Among them, a porous film made of polyolefin is preferable because it has an excellent short-circuit preventing effect and can improve battery safety by a shutdown effect. Especially, polyethylene is 100
Since the shutdown effect can be obtained in the range of ℃ or higher and 160 ℃ or lower, and the electrochemical stability is also excellent, it is preferable as a material forming the separator 23. Polypropylene is also preferable, and other resins having chemical stability can be used by copolymerizing with polyethylene or polypropylene or by blending.

This polyolefin porous film is prepared, for example, by kneading a molten polyolefin composition with a liquid low-volatile solvent in a molten state to form a uniform high-concentration solution of the polyolefin composition, and then dicing it. Molded by
It is obtained by cooling to a gel-like sheet and stretching.

As the low volatile solvent, for example, nonane,
Low volatile aliphatic or cyclic hydrocarbons such as decane, decalin, p-xylene, undecane or liquid paraffin can be used. The blending ratio of the polyolefin composition and the low volatile solvent is 100% by mass in total of both.
As the polyolefin composition, it is preferably 10% by mass or more and 80% by mass or less, more preferably 15% by mass or more and 70% by mass or less. This is because if the polyolefin composition is too small, swelling or neck-in will increase at the die outlet during molding, making it difficult to form a sheet. on the other hand,
This is because it is difficult to prepare a uniform solution when the amount of the polyolefin composition is too large.

When a high-concentration solution of the polyolefin composition is molded by a die, in the case of a sheet die, the gap is preferably 0.1 mm or more and 5 mm or less. Further, the extrusion temperature is preferably 140 ° C. or higher and 250 ° C. or lower, and the extrusion speed is preferably 2 cm / min or higher and 30 cm / min or lower.

Cooling is performed at least up to the gelation temperature. As a cooling method, a method of directly contacting with cold air, cooling water, or other cooling medium, a method of contacting with a roll cooled with a refrigerant, or the like can be used. The high-concentration solution of the polyolefin composition extruded from the die may be taken up at a take-up ratio of 1 or more and 10 or less, preferably 1 or more and 5 or less before or during cooling. This is because if the take-up ratio is too large, neck-in becomes large, and breakage easily occurs during stretching, which is not preferable.

The stretching of the gel-like sheet is preferably carried out, for example, by heating the gel-like sheet and biaxially stretching it by a tenter method, a roll method, a rolling method or a combination thereof. At that time, either vertical or horizontal simultaneous stretching or sequential stretching may be used, but simultaneous secondary stretching is particularly preferable.
The stretching temperature is preferably equal to or lower than the temperature obtained by adding 10 ° C. to the melting point of the polyolefin composition, more preferably equal to or higher than the crystal dispersion temperature and lower than the melting point. This is because if the stretching temperature is too high, it is not preferable because effective molecular chain orientation due to stretching cannot be performed due to melting of the resin, and if the stretching temperature is too low, the softening of the resin becomes insufficient and film breakage occurs during stretching. This is because it is easy and cannot be stretched at a high magnification.

After stretching the gel-like sheet, it is preferable to wash the stretched film with a volatile solvent to remove the residual low-volatile solvent. After washing, the stretched film is dried by heating or blowing air to evaporate the washing solvent. As the cleaning solvent, for example, pentane, hexane,
A hydrocarbon such as heptane, a chlorinated hydrocarbon such as methylene chloride or carbon tetrachloride, a fluorocarbon such as ethane trifluoride, or an easily volatile one such as an ether such as diethyl ether or dioxane is used. The cleaning solvent is selected according to the low-volatile solvent used and may be used alone or in combination. The washing can be performed by a method of dipping in a volatile solvent for extraction, a method of sprinkling a volatile solvent, or a method of combining these methods. This washing is performed until the residual low volatility solvent in the stretched film is less than 1 part by mass based on 100 parts by mass of the polyolefin composition.

The separator 23 is impregnated with an electrolytic solution which is a liquid electrolyte. This electrolyte is a liquid solvent,
For example, it contains a non-aqueous solvent such as an organic solvent and a lithium salt which is an electrolyte salt dissolved in the non-aqueous solvent. The liquid non-aqueous solvent is, for example, a non-aqueous compound,
It has a viscosity of 10.0 mPa · s or less at 25 ° C. The intrinsic viscosity in a state in which the electrolyte salt is dissolved may be 10.0 mPa · s or less, and when a plurality of types of non-aqueous compounds are mixed to form a solvent, the intrinsic viscosity in the mixed state is It may be 10.0 mPa · s or less.

As such a non-aqueous solvent, various conventionally used non-aqueous solvents can be used. Specifically, cyclic carbonic acid esters such as propylene carbonate or ethylene carbonate, chain esters such as diethyl carbonate, dimethyl carbonate or ethylmethyl carbonate, or ethers such as γ-butyrolactone, sulfolane, 2-methyltetrahydrofuran or dimethoxyethane. Is mentioned. In particular, from the viewpoint of oxidation stability, it is preferable to use a carbonic acid ester as a mixture.

As the lithium salt, for example, LiAsF
₆, LiPF₆, LiBF_Four, LiClO_Four, LiB
(C₆H_Five)_Four, LiCH₃SO₃, LiCF₃S
O₃, LiN (CF₃SO₂)₂, LiN (C₂F_FiveS
O₂)₂, LiN (C_FourF₉SO₂) (CF₃S
O₂), LiC (CF₃SO₂)₃, LiAlCl_Four,
LiSiF ₆, LiCl or LiBr,
Using any one of these or a mixture of two or more
Good.

Among them, LiPF ₆ is preferable because it can obtain high conductivity and is excellent in oxidative stability.
LiBF ₄ is preferable because it is excellent in thermal stability and oxidation stability. LiCF ₃ SO ₃ is preferable because it has high thermal stability, and LiClO ₄ is preferable because it can obtain high conductivity. In addition, LiN (CF ₃ SO ₂ ) ₂ ,
_{LiN (C 2 F 5 SO 2} ) 2, LiC (CF 3 SO 2)
₃ and _{LiN (C 4 F 9 SO 2} ) (CF 3 SO 2)
Is preferable because it can obtain a relatively high electric conductivity and has high thermal stability. Furthermore, at least two of these
It is more preferable to mix and use the seeds because these effects can be obtained together.

The content (concentration) of these lithium salts is preferably in the range of 0.5 mol / kg to 3.0 mol / kg with respect to the solvent. This is because outside this range, sufficient battery characteristics may not be obtained due to the extreme decrease in ionic conductivity.

This electrolytic solution also contains, as an additive, at least one member selected from the group consisting of crown ethers and glymes. As a result, in this secondary battery, it is possible to suppress the co-intercalation of the solvent at the time of charging and to prevent the reaction between the deposited lithium metal and the solvent at the time of depositing lithium. That is, the chemical stability of the electrolytic solution is high, a high discharge capacity can be obtained, and the cycle characteristics and the like can be improved.
Although the crown ethers and glymes may function as a solvent, they are described as additives in the present specification by paying attention to the above-mentioned functions. Of course, at least a part of the added compound may contribute to the reaction as described above, and the compound that does not contribute to the reaction may function as a solvent.

As the crown ethers, for example, 1
2-crown-4,15-crown-5,18-crown-6,14-crown-4 or 17-crown-
5 is mentioned. Further, as the grime, for example,
Examples include monoglyme (1,2-dimethoxyethane), diglyme, triglyme or tetraglyme. Above all, it is preferable to contain 12-crown-4 or monoglyme because a higher effect can be obtained.

When the content of these crown ethers and glymes is two or more, the total content thereof is 0.005% by mass or more and 1 with respect to the total of the solvent and the electrolyte salt.
It is preferably within the range of 5% by mass or less. 0.00
This is because if it is less than 5% by mass, a sufficient effect cannot be obtained, and if it exceeds 15% by mass, the battery may deteriorate during storage.

This secondary battery can be manufactured, for example, as follows.

First, for example, a positive electrode material capable of occluding / releasing lithium, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and this positive electrode mixture is mixed with N-methyl-2-pyrrolidone or the like. To form a paste-like positive electrode mixture slurry. The positive electrode mixture slurry is applied to the positive electrode current collector 21a, the solvent is dried, and then compression molding is performed using a roll press or the like to form the positive electrode mixture layer 21b, and the positive electrode 21 is manufactured.

Next, for example, a negative electrode material capable of inserting and extracting lithium and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone. To obtain a paste-like negative electrode mixture slurry.
The negative electrode mixture slurry is applied to the negative electrode current collector 22a, the solvent is dried, and then compression molding is performed by a roll press machine or the like to form the negative electrode mixture layer 22b, whereby the negative electrode 22 is manufactured.

Subsequently, the positive electrode lead 2 is attached to the positive electrode current collector 21a.
5 is attached by welding or the like, and the negative electrode current collector 22
The negative electrode lead 26 is attached to a by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound via the separator 23, the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the end of the negative electrode lead 26 is welded to the battery can 11 to be wound. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and housed inside the battery can 11. After housing the positive electrode 21 and the negative electrode 22 inside the battery can 11, the electrolytic solution is injected into the battery can 11, and the separator 2
Impregnate 3 After that, the battery lid 14, the safety valve mechanism 15, and the PTC device 16 are fixed to the open end of the battery can 11 by caulking with a gasket 17. As a result, the secondary battery shown in FIGS. 1 and 2 is formed.

This secondary battery operates as follows.

In this secondary battery, when charged, lithium ions are released from the positive electrode mixture layer 21b, and the separator 2
First, through the electrolytic solution impregnated in 3, the negative electrode mixture layer 22
The lithium contained in b is stored in the negative electrode material capable of storing and releasing. When charging is further continued, the charge capacity exceeds the charge capacity of the negative electrode material capable of occluding / releasing lithium on the surface of the negative electrode material capable of occluding / releasing lithium when the open circuit voltage is lower than the overcharge voltage. Lithium metal begins to precipitate. After that, lithium metal continues to deposit on the negative electrode 22 until the charging is completed. As a result, the appearance of the negative electrode mixture layer 22b changes from black to golden color and further to white silver color when graphite is used as the negative electrode material capable of inserting and extracting lithium.

Next, when discharging is performed, first, the lithium metal deposited on the negative electrode 22 is eluted as ions, and the positive electrode mixture layer 21 is evacuated through the electrolytic solution impregnated in the separator 23.
It is stored in b. When the discharge is further continued, the negative electrode mixture layer 22
The lithium ions stored in the negative electrode material capable of storing and releasing lithium in b are released and are stored in the positive electrode mixture layer 21b via the electrolytic solution. Therefore, with this secondary battery, the characteristics of both the conventional so-called lithium secondary battery and lithium-ion secondary battery, that is, high energy density and good cycle characteristics can be obtained.

Particularly in the present embodiment, since at least one member selected from the group consisting of crown ethers and glymes is contained, charging is performed by selectively coordinating the crown ethers or glymes with lithium ions. Sometimes it is adsorbed on the surface of the negative electrode 22. This prevents co-intercalation of the solvent into the negative electrode material and forms a stable ether-based film on the surface of the negative electrode 22. Therefore, the lithium metal is deposited under this coating, and at the time of lithium deposition, the reaction between the deposited lithium metal and the solvent is prevented.

As described above, according to the present embodiment, since at least one member selected from the group consisting of crown ethers and glymes is contained, crown ethers or glymes are selectively distributed to lithium ions. It can be adsorbed on the surface of the negative electrode 22 at the time of charging, and co-intercalation of the solvent into the negative electrode material can be prevented. Further, a stable ether-based coating can be formed on the surface of the negative electrode 22, and when lithium is deposited,
Lithium metal can be deposited under this coating to prevent reaction between the deposited lithium metal and the solvent. Therefore, the chemical stability of the electrolytic solution can be improved, and the battery characteristics such as discharge capacity and cycle characteristics can be improved.

Particularly, if the total content of crown ethers and glymes is 0.005 mass% or more and 15 mass% or less with respect to the total of the solvent and the electrolyte salt, a higher effect can be obtained. .

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention.
2 is an exploded view of the configuration of the secondary battery according to the embodiment of FIG. In this secondary battery, a spirally wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is sealed inside film-shaped exterior members 40a and 40b. The positive electrode lead 31 and the negative electrode lead 32 are made of a material that is electrochemically and chemically stable and can conduct electricity, for example, a metal material such as aluminum, copper, or nickel.

The exterior members 40a and 40b are made of, for example, a rectangular laminated film obtained by laminating a nylon film, an aluminum foil and a polyethylene film in this order. The exterior members 40a and 40b are
For example, the polyethylene film side and the spirally wound electrode body 30 are arranged so as to face each other, and the respective outer edge portions are adhered to each other by fusion or an adhesive. Exterior member 40
a, 40b, positive electrode lead wire 31, and negative electrode lead wire 32
An adhesion film 41 for preventing the invasion of the outside air is inserted between and. The adhesion film 41 is made of a material having adhesion to the positive electrode lead wire 31 and the negative electrode lead wire 32. For example, when the positive electrode lead wire 31 and the negative electrode lead wire 32 are made of the above-mentioned metal material, It is preferably composed of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene or modified polypropylene.

The exterior members 40a, 40b may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-mentioned laminated film.

FIG. 4 is an enlarged view of a part of the sectional structure of the spirally wound electrode body 30 shown in FIG. Winding electrode body 30
Is obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte 36 in between. Positive electrode 33
The configurations of (the positive electrode current collector layer 33a and the positive electrode mixture layer 33b), the negative electrode 35 (the negative electrode current collector layer 34a and the negative electrode mixture layer 34b) and the separator 35 are the same as those in the first embodiment.

The electrolyte 36 is a so-called gel in which an electrolytic solution is dispersed or held in a holder, and the separator 35 is used.
Positive electrode side electrolyte layer 36a located on the positive electrode 33 side through
And a negative electrode side electrolyte layer 36b located on the negative electrode 34 side. The ionic conductivity of the electrolyte layer 36 is 1 at room temperature.
It is preferably mS / cm or more.

The holder is made of, for example, a polymer material and has a positive electrode side electrolyte layer 36a and a negative electrode side electrolyte layer 36.
They may be the same as or different from b. Examples of the polymer material include polyvinylidene fluoride and a copolymer of polyvinylidene fluoride, and examples of the copolymer monomer include hexafluoropropylene and tetrafluoroethylene. These polyvinylidene fluoride and its copolymers are preferable because high battery characteristics can be obtained, and among them, the copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable.

In addition, as the polymer material, for example, polyacrylonitrile and a copolymer of polyacrylonitrile can be used. As the copolymer monomer, for example, vinyl monomers, vinyl acetate, methyl methacrylate and methacrylic acid can be used. Butyl, methyl acrylate, butyl acrylate, itaconic acid, hydrogenated methyl acrylate,
Examples thereof include hydrogenated ethyl acrylate, acrylamide, vinyl chloride, vinylidene fluoride or vinylidene chloride. In addition, acrylonitrile butadiene rubber, acrylonitrile butadiene styrene resin, acrylonitrile chloride polyethylene propylene diene styrene resin, acrylonitrile chloride polyethylene propylene diene styrene resin, acrylonitrile vinyl chloride resin,
Acrylonitrile methacrylate resin or acrylonitrile acrylate resin may be used.

As the polymer material, for example, polyethylene oxide or a copolymer of polyethylene oxide may be used, and as the copolymerization monomer, polypropylene oxide, methyl methacrylate, butyl methacrylate, methyl acrylate or acrylic acid may be used. Butyl acid and the like can be mentioned. In addition, polyether-modified siloxane and its copolymer may be used.

The content of the holder is preferably in the range of 5% by mass to 50% by mass with respect to the electrolytic solution in order to obtain a good gel state.

The electrolytic solution is the same as in the first embodiment,
It contains a liquid solvent, an electrolyte salt, and at least one selected from the group consisting of crown ethers and glymes. The electrolyte solution may be the same or different in the positive electrode side electrolyte layer 36a and the negative electrode side electrolyte layer 36b, but it is preferable that the contents of crown ethers and glymes are different. Specifically, the content in the negative electrode side electrolyte layer 36b is preferably larger than the content in the positive electrode side electrolyte layer 36a. This is because the crown ethers and glymes have a function of particularly improving the battery characteristics in the negative electrode 34. In the present specification, the content is different or the content is large includes a case where the content is zero, and when a plurality of kinds are mixed and included, a concept that a part of the content is different is also included. Is.

This secondary battery can be manufactured, for example, as follows.

First, similarly to the first embodiment, the positive electrode 33 and the negative electrode 34 are manufactured, and the positive electrode lead 31 and the negative electrode lead 32 are attached. Then, the positive electrode mixture layer 33
The positive electrode side electrolyte layer 36a is formed on b, and the negative electrode side electrolyte layer 36b is formed on the negative electrode mixture layer 34b.
At that time, it is preferable that the crown ethers and the glymes are not added to the positive electrode side electrolyte layer 36a, and the crown ethers and the glymes are added only to the negative electrode side electrolyte layer 36b. Then, for example, the separator 35, the positive electrode 33, the separator 35, and the negative electrode 34 are laminated in this order and wound to form the wound electrode body 30.

After that, the wound electrode body 30 is attached to the exterior member 40.
It is sandwiched between a and 40b, and the outer edge portions of the exterior members 40a and 40b are sealed by heat fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior members 40a and 40b. As a result, the secondary battery shown in FIGS. 3 and 4 is completed.

This secondary battery operates in the same manner as in the first embodiment, and the same effect can be obtained.

[0084]

EXAMPLES Further, specific examples of the present invention will be described in detail.

(Examples 1-1 to 1-3) FIGS. 1 and 2
The secondary battery shown in was produced. Here, description will be given using the reference numerals shown in FIGS. 1 and 2 with reference to FIGS. 1 and 2.

First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) were mixed with Li ₂ CO ₃ : CoC.
O ₃ = 0.5: 1 (molar ratio) was mixed, and the mixture was baked in air at 900 ° C. for 5 hours to obtain a lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode material.
Next, 91 parts by mass of this lithium-cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Then, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone which is a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of a positive electrode current collector 21a made of a strip-shaped aluminum foil having a thickness of 20 μm and dried. Then, the positive electrode mixture layer 21b is formed by compression molding with a roll press to form the positive electrode 2
1 was produced. After that, the positive electrode lead 25 made of aluminum was attached to one end of the positive electrode current collector 21a.

Further, petroleum pitch was used as a starting material, 10% to 20% of a functional group containing oxygen was introduced into this to effect oxygen crosslinking, and the mixture was fired at 1000 ° C. in an inert gas stream to obtain glassy carbon. Non-graphitizable carbon having properties close to those of the above was obtained as a negative electrode material. When X-ray diffraction measurement was performed on the obtained non-graphitizable carbon, the spacing between (002) planes was 0.3.
It was 76 nm and the true density was 1.58 g / cm ³ . Next, this non-graphitizable carbon is pulverized to have an average particle size of 1
A powder of 0 μm was prepared, and 90 parts by mass of this non-graphitizable carbon and 10 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. Subsequently, this negative electrode mixture is dispersed in N-methyl-2-pyrrolidone which is a solvent to form a slurry, which is then uniformly applied to both surfaces of a negative electrode current collector 22a made of a strip-shaped copper foil having a thickness of 10 μm and dried. Then, the negative electrode mixture layer 22b was formed by compression molding with a roll press machine to fabricate the negative electrode 22. After that, the negative electrode lead 26 made of nickel was attached to one end of the negative electrode current collector 22a.

When producing the positive electrode 21 and the negative electrode 22, the area density ratio between the positive electrode 21 and the negative electrode 22 is adjusted,
The capacity of the negative electrode 22 is represented by the sum of the capacity component due to occlusion / desorption of lithium and the capacity component due to precipitation / dissolution of lithium.

After each of the positive electrode 21 and the negative electrode 22 is prepared, a separator 23 made of a microporous polypropylene film having a thickness of 25 μm is prepared, and the negative electrode 22, the separator 23, the positive electrode 21 and the separator 23 are laminated in this order to form this laminate. A spirally wound electrode body 20 was manufactured by winding the spiral electrode member a number of times.

After the wound electrode body 20 is manufactured, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, and the negative electrode lead 2 is formed.
6 was welded to the battery can 11, the positive electrode lead 25 was welded to the safety valve mechanism 15, and the wound electrode body 20 was housed inside the nickel-plated iron battery can 11. After that, the electrolytic solution was injected into the battery can 11 by a reduced pressure method. The electrolytic solution was prepared by mixing 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate in a solvent and adding L as an electrolyte salt.
iPF ₆ dissolved in a content of 1 mol / l,
The crown ethers added were used at a content of 1% by mass based on the total amount of the solvent and the electrolyte salt. The type of crown ethers was changed as shown in Table 1 in Examples 1-1 to 1-3.

[0091]

[Table 1]

After injecting the electrolytic solution into the battery can 11, the battery lid 14 is caulked to the battery can 11 via the gasket 17 having the surface coated with asphalt. Diameter 14mm, height 65m
A cylindrical secondary battery of m was obtained.

Further, as Comparative Example 1-1 to this example, a secondary battery was manufactured in the same manner as in this example except that 12-crown-4 was not added to the electrolytic solution. Further, as Comparative Examples 1-2 and 1-3 with respect to the present example, except that the area density ratio of the positive electrode and the negative electrode was adjusted so that the capacity of the negative electrode was represented by occlusion / desorption of lithium,
A so-called lithium-ion secondary battery was produced in the same manner as in this example. At that time, in Comparative Example 2, 12-crown-4 was added to the electrolytic solution at a content of 1% by mass with respect to the total amount of the solvent and the electrolyte salt as in Example 1, and in Comparative Example 1-3, the electrolytic solution was added. No 12-crown-4 was added to the.

A charging / discharging test was conducted on the obtained secondary batteries of Examples 1-1 to 1-3 and Comparative examples 1-1 to 1-3, and the discharge capacity at the first cycle, that is, the initial discharge capacity, The discharge capacity at the 100th cycle was determined. that time,
Charging was performed at a constant current of 600 mA until the battery voltage reached 4.2 V, and then at a constant voltage of 4.2 V, the current was 1 mA.
The discharge was performed at a constant current of 400 mA until the battery voltage reached 3.0 V. By the way, if charging and discharging are performed under the conditions shown here, a fully charged state and a completely discharged state are obtained. The results obtained are shown in Table 1. In Table 1, the initial discharge capacities of Examples 1-1 to 1-3 are Comparative Example 1
It is a relative value when the initial discharge capacity of -1 is 100,
The discharge capacities at the 100th cycle of Examples 1-1 to 1-3 are relative values when the discharge capacity at the 100th cycle of Comparative Example 1-1 is 100. The initial discharge capacity of Comparative Example 1-2 is a relative value when the initial discharge capacity of Comparative Example 1-3 is 100, and the discharge capacity at the 100th cycle of Comparative Example 1-2 is Comparative Example 1-3. Discharge capacity at 100th cycle of 1
This is a relative value when 00 is set.

Regarding the secondary batteries of Examples 1-1 to 1-3 and Comparative examples 1-1 to 1-3, 1
After the cycle charge and discharge, the one that was completely charged again was disassembled, and it was examined visually and by ⁷ Li nuclear magnetic resonance spectroscopy whether or not lithium metal was deposited on the negative electrode mixture layer 22b. Further, charging / discharging was performed for 2 cycles under the above-mentioned conditions, the completely discharged one was disassembled, and it was examined in the same manner whether lithium metal was deposited on the negative electrode mixture layer 22b.

As a result, in the secondary batteries of Examples 1-1 to 1-3 and Comparative example 1-1, the presence of lithium metal was observed in the negative electrode mixture layer 22b in the fully charged state, and in the completely discharged state. The presence of lithium metal was not recognized. That is, it was confirmed that the capacity of the negative electrode 22 is represented by the sum of the capacity component due to precipitation / dissolution of lithium metal and the capacity component due to occlusion / release of lithium. Table 1
As a result, it was described that lithium metal was precipitated.

On the other hand, in the secondary batteries of Comparative Examples 1-2 and 1-3, the presence of lithium metal was not recognized in both the fully charged state and the completely discharged state, and only the presence of lithium ions was recognized. It was In addition, the peak attributed to lithium ions observed in the completely discharged state was extremely small. That is, it was confirmed that the capacity of the negative electrode is represented by the capacity component due to insertion and extraction of lithium. As a result, it is described in Table 1 that there is no precipitation of lithium metal.

As can be seen from Table 1, according to Examples 1-1 to 1-3 in which crown ethers were added, crown ethers were not added for both the initial discharge capacity and the discharge capacity at the 100th cycle. Comparative Example 1-1
Higher values were obtained. On the other hand, in Comparative Examples 1-2 and 1-3, which are lithium-ion secondary batteries, Comparative Example 1-2 in which crown ethers were added was compared to Comparative Example 1-3 in which the crown ethers were not added. Although a slightly high value was obtained for both the discharge capacity and the discharge capacity at the 100th cycle, the effect was small.

That is, in the secondary battery in which the capacity of the negative electrode 22 is represented by the sum of the capacity component due to occlusion and desorption of light metal and the capacity component due to precipitation and dissolution of light metal, the electrolytic solution contains crown ethers. By doing so, it was found that the discharge capacity and the cycle characteristics can be improved.

Example 2-1 The secondary battery shown in FIGS. 3 and 4 was manufactured as follows. Here, FIG.
4 and FIG. 4 will be described using the reference numerals shown in FIGS.

First, the positive electrode 33 and the negative electrode 34 were used in Example 1.
It was produced in the same manner as in -1. At that time, occlude lithium
Artificial graphite powder was used in place of non-graphitizable carbon as the removable negative electrode material, and the thickness of the negative electrode current collector 34a was 15 μm.
The strip-shaped copper foil of was used. Next, the positive electrode lead 31 made of aluminum was attached to one end of the positive electrode current collector 33a, and the negative electrode lead 32 made of nickel was attached to one end of the negative electrode current collector 34a.

Subsequently, a positive electrode side electrolyte layer 36a was formed on both surfaces of the positive electrode 33, and a negative electrode side electrolyte layer 36b was formed on both surfaces of the negative electrode 34. For the positive electrode side electrolyte layer 36a and the negative electrode side electrolyte layer 36b, a polymer obtained by block-copolymerizing vinylidene fluoride and hexafluoropropylene as a polymer material and holding an electrolytic solution was used.
The electrolytic solution was prepared by dissolving LiPF ₆ as an electrolyte salt at a content of 0.6 mol / l in a solvent prepared by mixing ethylene carbonate and propylene carbonate at a mass ratio of ethylene carbonate: propylene carbonate = 1: 1. -Crown-4 was used in a content of 1% by mass based on the total amount of the solvent and the electrolyte salt.

After forming the positive electrode side electrolyte layer 36a and the negative electrode side electrolyte layer 36b, a separator 35 made of a microporous polyethylene film is prepared, and the positive electrode 33, the separator 35, the negative electrode 34 and the separator 35 are laminated in this order to form a spiral shape. The wound electrode body 30 was manufactured by winding a large number of turns. After that, while winding out the positive electrode lead 31 and the negative electrode lead 32 to the outside, the spirally wound electrode body 30 was vacuum-sealed in the exterior members 40a and 40b made of a laminate film, and Example 2-1 is shown in FIGS. I got a secondary battery.

As Comparative Example 2-1 with respect to this Example, 12-crown-type was used for the positive electrode side electrolyte layer and the negative electrode side electrolyte layer.
A secondary battery was made in the same manner as in this example except that 4 was not added. In addition, Comparative Example 2 with respect to this example
-2, 2-3, so-called lithium ion was prepared in the same manner as in this example, except that the area density ratio of the positive electrode and the negative electrode was adjusted so that the capacity of the negative electrode was represented by occlusion / desorption of lithium. A secondary battery was produced. At that time, Comparative Example 2
-2, 12-crown-4 was added to both the positive electrode side electrolyte layer and the negative electrode side electrolyte layer as in Example 2-1. In Comparative Example 2-3, the positive electrode side electrolyte layer was added as in Comparative Example 2-1. 12-crown-4 was not added to both the negative electrode electrolyte layer and the negative electrode side electrolyte layer. Furthermore, Comparative Examples 2-4 and 2 to this Example
As -5, a so-called lithium secondary battery was produced in the same manner as in this example, except that rolled lithium metal was used for the negative electrode and the capacity of the negative electrode was represented by precipitation / dissolution of lithium. At that time, in Comparative Example 2-4, 12-crown-4 was added to both the positive electrode side electrolyte layer and the negative electrode side electrolyte layer as in Example 2-1, and in Comparative Example 2-5, as Comparative Example 2-1. Similarly, 12-crown-4 was not added to both the positive electrode side electrolyte layer and the negative electrode side electrolyte layer.

Obtained Example 2-1 and Comparative Example 2-1
The secondary batteries of Nos. 2 to 5 were subjected to a charge / discharge test, and the initial discharge capacity and the discharge capacity at the 30th cycle were examined. The initial discharge capacity is the discharge capacity obtained in the charge / discharge of the first cycle. The charge / discharge is performed at 23 ° C. with a constant current constant voltage charge of 1 A up to an upper limit of 4.2 V, and then the constant current discharge of 200 mA is stopped. The voltage was increased to 3.0V. The discharge capacity at the 30th cycle is the discharge capacity obtained at the 29th cycle (that is, the 30th cycle as a whole) after 29 cycles of charging and discharging after obtaining the initial discharge capacity. The charge and discharge at that time was carried out at a constant current and constant voltage of 1 A at 23 ° C. up to an upper limit of 4.2 V, and then 500
A constant current discharge of mA was performed up to a final voltage of 3.0V. The obtained results are shown in Table 2.

[0106]

[Table 2]

In Table 2, the value of Example 2-1 is a relative value when the initial discharge capacity of Comparative Example 2-1 and the discharge capacity at the 30th cycle are 100, and the value of Comparative Example 2-2. Is a relative value when the initial discharge capacity of Comparative Example 2-3 and the discharge capacity of the 30th cycle are 100, and the value of Comparative Example 2-4 is the initial discharge capacity of Comparative Example 2-5 and the 30th cycle. It is a relative value when the discharge capacity of is 100.

The discharge curves at 30th cycle of Example 2-1 and Comparative Example 2-1 are shown in FIGS. 5 and 6. FIG. 5 shows the discharge capacity at the 30th cycle of Comparative Example 2-1 as 10
FIG. 7 is a comparison diagram of Example 2-1 and Comparative Example 2-1 when it is set to 0, and FIG. 6 shows the discharge capacity at 30th cycle in Example 2-1 and Comparative Example 2-1 as 100. It is a comparison diagram of Example 2-1 at the time and Comparative Example 2-1.

Furthermore, Example 2-1 and Comparative Examples 2-1 to 2-1
Regarding the secondary battery of 2-3, the presence or absence of lithium metal deposition in the fully charged state and the completely discharged state was examined in the same manner as in Example 1-1. The results are also shown in Table 2.
In addition, with respect to the secondary batteries of Comparative Examples 2-4 and 2-5, since lithium metal was used for the negative electrode, it was not examined whether or not lithium metal was deposited, but in Table 2, lithium metal was deposited. It was described.

As can be seen from Table 2 and FIG. 5, according to Example 2-1 in which crown ethers were added, crown ethers were not added for both the initial discharge capacity and the discharge capacity at the 30th cycle. Comparative Example 2-1
Higher values were obtained. On the other hand, in Comparative Examples 2-2 and 2-3, which are lithium-ion secondary batteries, Comparative Example 2-2 in which crown ethers were added was the first time compared to Comparative Example 2-3 in which no crown ethers were added. Although a slightly higher discharge capacity was obtained, the discharge capacity at the 30th cycle was the same. In addition, Comparative Example 2 which is a lithium secondary battery
In Comparative Examples 4 and 2-5, Comparative Example 2-4 to which crown ethers were added was slightly higher in both the initial discharge capacity and the 30th cycle discharge capacity than Comparative Example 2-5 to which no crown ether was added. Was obtained, but the effect was small.

That is, also in a secondary battery using a gel electrolyte instead of the electrolytic solution, the capacity of the negative electrode 34 depends on the sum of the capacity component due to occlusion and release of light metal and the capacity component due to precipitation and dissolution of light metal. It has been found that in the secondary battery shown, the discharge capacity and the cycle characteristics can be improved by including crown ethers in the electrolyte.

As can be seen from FIGS. 5 and 6,
In Example 2-1 and Comparative Example 2-1, in the discharge curve, a region A corresponding to the precipitation / dissolution reaction of lithium and a region B corresponding to the absorption / desorption reaction of lithium were observed,
The region A corresponding to the precipitation / dissolution reaction of lithium was larger in Example 2-1 than in Comparative Example 2-1. That is, it was found that the addition of crown ethers greatly contributes to the increase in discharge capacity due to the precipitation / dissolution reaction of lithium.

(Examples 2-2 to 2-5) Glymes are added to the negative electrode side electrolyte layer 36b instead of crown ethers, and neither crown ethers nor glymes are added to the positive electrode side electrolyte layer 36a. A secondary battery was produced in the same manner as in Example 2-1 except for the above. The type of grime was changed as shown in Table 3 in Examples 2-2 to 2-5.

[0114]

[Table 3]

Further, as Comparative Example 2-6 with respect to this example, except that the area density ratio of the positive electrode and the negative electrode was adjusted so that the capacity of the negative electrode was represented by occlusion / release of lithium, A so-called lithium-ion secondary battery was produced in the same manner as in Example 2-2. Further, as Comparative Example 2-7 with respect to this Example, other than Example 2-2, except that rolled negative electrode lithium metal was used and the capacity of the negative electrode was represented by precipitation / dissolution of lithium. Similarly, a so-called lithium secondary battery was produced.

Regarding the obtained secondary batteries of Examples 2-2 to 2-5 and Comparative examples 2-6 and 2-7, the initial discharge capacity and the discharge capacity at the 30th cycle were the same as in Example 2-1. ,
The presence or absence of lithium metal deposition in the fully charged state and the completely discharged state was examined. The results are shown in Comparative Example 2-
It is shown in Table 3 together with the results of 1, 2, 3 and 2-5. In Table 3, the secondary batteries of Comparative Example 2-7 are described as having lithium metal deposited, as in Comparative Examples 2-4 and 2-5.

As can be seen from Table 3, according to Examples 2-2 to 2-5 in which the glymes were added, both the initial discharge capacity and the discharge capacity at the 30th cycle were compared without adding the glymes. Higher values were obtained than in Example 2-1. On the other hand, in Comparative Examples 2-6 and 2-3 which are lithium ion secondary batteries and Comparative Examples 2-7 and 2-5 which are lithium secondary batteries, the one to which the glymes were added was not added. Although the values for the initial discharge capacity and the discharge capacity at the 30th cycle were slightly higher than those of the above, the effect was small.

That is, in the secondary battery in which the capacity of the negative electrode 34 is represented by the sum of the capacity component due to occlusion and release of the light metal and the capacity component due to precipitation and dissolution of the light metal, it is necessary to include glymes in the electrolyte. It has been found that the discharge capacity and cycle characteristics can be improved. It was also found that at least the glymes should be added to the negative electrode side electrolyte layer 36b.

Although the crown ethers or glymes have been specifically described in the above examples, similar results can be obtained by using other crown ethers or other glymes. it can.

Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made. For example, in the above embodiments and examples, the case where lithium is used as the light metal has been described. However, other alkali metal such as sodium (Na) or potassium (K), or magnesium or calcium (C
The present invention can be applied to the case of using an alkaline earth metal such as a) or other light metal such as aluminum, or lithium or an alloy thereof.
The same effect can be obtained. At that time, a negative electrode material, a positive electrode material, a non-aqueous solvent, an electrolyte salt or the like capable of inserting and extracting a light metal is selected according to the light metal. However, it is preferable to use lithium or an alloy containing lithium as the light metal because the voltage compatibility with the lithium ion secondary batteries currently in practical use is high. When using an alloy containing lithium as a light metal, there is a substance capable of forming an alloy with lithium in the electrolyte, and an alloy may be formed during precipitation,
There may be a substance capable of forming an alloy with lithium in the negative electrode, and the alloy may be formed during precipitation.

In the second embodiment and Examples 2-1 to 2-5 described above, the case of using a so-called gel electrolyte is described, but the present invention includes a holder and an electrolytic solution. It can also be applied to the case of using another electrolyte. Examples of the other electrolyte include a polymer solid electrolyte obtained by swelling an electrolyte solution in a polymer material that is a holder. At that time, as the polymer material, for example, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, or the like is used. Further, the second embodiment and the example 2-1 to
In 2-5, a polymer material is used as the holder for explanation, but lithium nitride, lithium iodide or lithium hydroxide polycrystal, a mixture of lithium iodide and dichromium trioxide, or lithium iodide is used. An inorganic conductor such as a mixture of thylium sulfide and diphosphorus disulfide may be used as a holding body, or a polymer material and an inorganic conductor may be mixed and used.

In addition, in the above-described embodiments and examples, a cylindrical secondary battery having a wound structure, or
Although a laminate type secondary battery has been described, the present invention is also applicable to an elliptical or polygonal type secondary battery having a wound structure, or a secondary battery having a structure in which a positive electrode and a negative electrode are folded or stacked. Can be applied to. In addition, so-called coin type, button type,
It can also be applied to rectangular or large secondary batteries. Further, not only the secondary battery but also the primary battery can be applied.

[0123]

As described above, in the battery according to any one of claims 1 to 10, the electrolyte contains at least one member selected from the group consisting of crown ethers and glymes. Therefore, crown ethers or glymes can be adsorbed on the surface of the negative electrode to prevent co-intercalation of the electrolyte into the negative electrode. In addition, a stable ether-based coating can be formed on the surface of the negative electrode, light metal can be deposited under this coating, and the reaction between the deposited light metal and the electrolyte can be prevented. Therefore, the chemical stability of the electrolyte can be improved, and the battery characteristics such as discharge capacity and cycle characteristics can be improved.

In particular, according to the battery of claim 2, the total content of the crown ethers and the glymes is 0.005% by mass or more and 1 with respect to the total of the solvent and the electrolyte salt.
Since the amount is 5% by mass or less, a higher effect can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a secondary battery according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an enlarged part of a wound electrode body in the secondary battery shown in FIG.

FIG. 3 is an exploded perspective view showing an exploded secondary battery according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an enlarged part of a wound electrode body in the secondary battery shown in FIG.

FIG. 5 is a characteristic diagram showing a discharge curve at the 30th cycle according to Example 2-1 of the present invention in comparison with Comparative example 2-1.

FIG. 6 is a characteristic diagram showing a discharge curve at the 30th cycle according to Example 2-1 of the present invention in comparison with Comparative example 2-1.

[Explanation of symbols]

11 ... Battery can, 12, 13 ... Insulation plate, 14 ... Battery lid, 1
5 ... Safety valve mechanism, 15a ... Disk plate, 16 ... PTC element, 17 ... Gasket, 20, 30 ... Winding electrode body, 2
1, 33 ... Positive electrode, 21a, 33a ... Positive electrode current collector, 21
b, 33b ... Positive electrode mixture layer, 22, 34 ... Negative electrode, 22a,
34a ... Negative electrode collector, 22b, 34b ... Negative electrode mixture layer, 2
3, 35 ... Separator, 24 ... Center pin, 25, 3
DESCRIPTION OF SYMBOLS 1 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte, 36a ... Positive electrode side electrolyte layer, 36b ... Negative electrode side electrolyte layer, 40a, 40b ... Exterior member, 41 ... Adhesive film

Continued front page    F term (reference) 5H029 AJ03 AJ05 AK03 AL06 AL07                       AL08 AL11 AM03 AM04 AM05                       AM07 BJ02 BJ14 DJ09 HJ01                 5H050 AA07 AA08 BA17 CA07 CA08                       CA09 CB07 CB08 CB09 CB11                       DA13 HA01

Claims (10)

[Claims] 1. A battery provided with an electrolyte together with a positive electrode and a negative electrode, wherein the capacity of the negative electrode is represented by a sum of a capacity component due to occlusion and desorption of light metal and a capacity component due to precipitation and dissolution of light metal, A battery, wherein the electrolyte contains at least one member selected from the group consisting of crown ethers and glymes. 2. The electrolyte contains a solvent and an electrolyte salt, and the total content of crown ethers and glymes is 0.005% by mass or more and 15% by mass or less. battery. 3. The negative electrode contains a negative electrode material capable of inserting and extracting a light metal.
Battery described. 4. The battery according to claim 3, wherein the negative electrode contains a carbon material. 5. The battery according to claim 4, wherein the negative electrode contains at least one selected from the group consisting of graphite, graphitizable carbon, and non-graphitizable carbon. 6. The battery according to claim 5, wherein the negative electrode contains graphite. 7. The negative electrode according to claim 3, wherein the negative electrode contains at least one selected from the group consisting of a simple substance, an alloy and a compound of a metal element or a metalloid element capable of forming an alloy with the light metal. battery. 8. The negative electrode comprises tin (Sn), lead (Pn)
b), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium ( Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (H).
The battery according to claim 7, comprising at least one selected from the group consisting of simple substances, alloys, and compounds of f). 9. The battery according to claim 1, wherein the electrolyte includes a holder. 10. The battery according to claim 9, wherein the content of crown ethers and glymes is higher on the negative electrode side than on the positive electrode side.