JP2001185152A - Electrode additive and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode additive capable of absorbing the volume change of the electrode material, and a secondary battery using the same. SOLUTION: The electrode additive comprises an elastic structure 1 having a hollow portion 1a and a content 2 stored in the hollow portion 1a. The elastic structure 1 is formed of an elastic body such as a polymeric material, with the hollow portion 1a giving higher elasticity thereto. With the electrode additive contained in an electrode, the volume change of an electrode material when charged and discharged can be absorbed and the change of the physical formation of the electrode can be inhibited if charging and discharging are repeated, therefore improving the characteristics of charging and discharging cycles. It is acceptable that the content 2 contains a dewatering agent, a radical trapping agent, a flame retardant agent or hydrogen halide trapping agent, which easily offers effective operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode additive having elasticity and a secondary battery.

[0002]

2. Description of the Related Art A secondary battery is used as a power source that stores DC power by charging and can supply DC power to the outside as needed. Like the primary battery, this secondary battery is required to have a large retained energy density, that is, an electromotive force, a large amount of electricity that can be extracted per unit weight or unit volume, and a small self-discharge. It is also required that the decrease in energy density due to repeated charging and discharging is small. Further, in recent years, demands for higher energy density have been increasing along with miniaturization, weight reduction and higher performance of electronic devices.

[0003] A lithium ion secondary battery has been proposed and put into practical use to satisfy such demands. This lithium ion secondary battery is essentially different from conventional lead batteries, nickel-cadmium batteries, and the like in its reaction type, and utilizes lithium ion intercalation or doping phenomena to layered compounds and the like. for that reason,
In addition to features such as a memory effect and less self-discharge, a decrease in energy density due to repetition of charge and discharge is smaller than that of a conventional secondary battery, and excellent cycle characteristics can be obtained.

[0004]

However, in a lithium ion secondary battery or the like utilizing such an intercalation or doping phenomenon, a substance that absorbs and desorbs lithium ions during charging and discharging expands and contracts. There is a problem that the physical shape of the electrode changes before and after the discharge. Such a change in the physical shape of the electrode causes an increase in the contact resistance between the electrode constituting materials, and an increase in the internal resistance of the battery, which is one of the causes of a decrease in energy density. Therefore, in the present age in which further improvement in cycle characteristics is required, early solution of this problem has been desired. For example, conventionally, improvements have been made by using a polymer material having large elasticity as a binder, but a satisfactory result has not yet been obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrode additive capable of absorbing a change in volume of an electrode material and a secondary battery using the same.

[0006]

The electrode additive according to the present invention has an elastic structure having a hollow portion.

A secondary battery according to the present invention has a positive electrode and a negative electrode, and at least one of the positive electrode and the negative electrode contains an electrode additive having an elastic structure having a hollow portion.

The electrode additive according to the present invention has a hollow portion, so that greater elasticity can be obtained.

In the secondary battery according to the present invention, since at least one of the positive electrode and the negative electrode contains the electrode additive of the present invention, a change in physical shape of the positive electrode or the negative electrode due to charge and discharge is suppressed. Therefore, an increase in contact resistance at the positive electrode or the negative electrode is suppressed, and cycle characteristics are improved.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 3 show a sectional structure of an electrode additive according to an embodiment of the present invention. The electrode additive includes an elastic structure 1 having a hollow portion 1a and a content 2 stored in the hollow portion 1a. The elastic structure 1 is made of an elastic body such as a polymer material, and has a higher elasticity by having the hollow portion 1a. The material forming the elastic structure 1 needs to be stable in the potential range of the electrode using the electrode additive.

For example, when used for a positive electrode of a lithium ion secondary battery or the like, the material constituting the elastic structure 1 may be polytetrafluoroethylene, a copolymer containing tetrafluoroethylene units, polyvinylidene fluoro A copolymer containing a vinylidene fluoride unit, a copolymer containing a hexafluoropropylene unit, a copolymer containing a chlorotrifluoroethylene unit,
Copolymers containing perfluoro (alkyl vinyl) ether units, polyacrylonitrile, copolymers containing acrylonitrile units, polystyrene, copolymers containing styrene units, polyimides, copolymers containing imide units, copolymers containing amide imide units Polymers, polyesters, polyurethanes or polyolefins are preferred.

For example, when the elastic structure 1 is used for a negative electrode of a lithium ion secondary battery or the like, the material constituting the elastic structure 1 may be polyolefin, polystyrene, or the like.
Styrene-butadiene rubber, polyvinylidene fluoride, a copolymer containing vinylidene fluoride units,
Copolymers containing hexafluoropropylene units, copolymers containing chlorotrifluoroethylene units, copolymers containing perfluoro (alkyl vinyl) ether units, chloroprene rubber, isoprene rubber, butadiene rubber, silicone rubber, polyimide, imide A copolymer containing units,
A copolymer containing an amide imide unit, an alginic acid compound,
A carboxymethyl cellulose compound, polyester or polyurethane is preferred.

Among the above materials, those containing styrene-butadiene, chloroprene, or vinylidenefluoride units, acrylonitrile units or imide units have high binding properties, and are therefore bound to the electrode additive material. It is preferable to have a function as an agent.
When the content 2 contains a flame retardant as described later, the elastic structure 1 is made of a material having a low melting point, and can be dissolved when the temperature rises to release the flame retardant to the outside of the elastic structure 1. You may do so. Examples of such a material include polyolefin, styrene-butadiene rubber, a copolymer containing vinylidene fluoride units, a copolymer containing hexafluoropropylene units, chloroprene rubber and isoprene rubber.

The elastic structure 1 may not have micropores or permeability and the hollow portion 1a may be hermetically closed. However, the elastic structure 1 has micropores or permeability and the hollow portion 1a is closed to the outside. It may be connected. In particular, when the content 2 contains a dehydrating agent as described later, it is preferable that the hollow portion 1a is communicated with the outside. This is for making the function of the contents 2 work effectively. The size of the elastic structure 1 is preferably, for example, equal to or smaller than that of another material forming the electrode, specifically, a material whose volume changes during operation. In order to absorb the volume change of other materials,
This is because it is sufficient if the volume is approximately the same as the volume of the volume change material. If the volume is too large, the amount of the electrode material contributing to the electrode reaction decreases, and the capacity of the battery decreases.

The shape of the elastic structure 1 may be any shape, and may be not only the granular shape as shown in FIG. 1 but also a columnar shape. As shown in FIG. Shape may be sufficient. The shape of the hollow portion 1a may be any shape, and may be any number. For example, FIGS. 2 and 3
As shown in the above, a plurality of hollow portions 1a may be provided.

The contents 2 may be in any form of gas, liquid, solid or a mixture thereof. However, when it is composed of only a solid, it is preferably composed of a rubber-based polymer material having high elasticity. The contents 2 may be configured to have at least one of a dehydrating agent, a radical scavenger, a flame retardant, and a hydrogen halide scavenger to have their functions. In conventional batteries, it is common to add these functional substances to the electrolyte for the purpose of improving battery characteristics or safety. Of these functional substances, the potentials that can be taken by both the positive electrode and the negative electrode Few were stable in the range, and effective materials were used at the expense of other properties. Therefore, if these functional substances are included in the contents 2 as in the present invention, they can be used without worrying about the potential, the range of material selection can be widened, and higher effects can be obtained. It is preferable because it is possible.

As the dehydrating agent, for example, anhydrous zinc bromide (ZnBr ₂ ), anhydrous zinc chloride (ZnCl ₂ ), diphosphorus pentoxide (P ₂ O ₅ ), anhydrous calcium chloride (CaC
l ₂ ), sodium chloride (NaCl), calcium oxide (CaO), calcium hydroxide (Ca (OH) ₂ ), sodium hydroxide (NaOH), potassium hydroxide (KO)
H), or a sulfate represented by sodium sulfate (Na ₂ SO ₄ ) or potassium sulfate (K ₂ SO ₄ ), or represented by sodium carbonate (Na ₂ CO ₃ ) or potassium carbonate (K ₂ CO ₃ ) Examples thereof include carbonates and organic anhydrides represented by oxalic anhydride.

Examples of the radical scavenger include an antioxidant, a hindered amine light stabilizer, an ultraviolet absorber, hydroquinone or a hydroquinone derivative.
Examples of the antioxidant include butylhydroxytoluene, phenyl-β-naphthylamine, and distearylthiodipropionate. The ultraviolet absorber may be any of salicylic acid, benzophenone, benzotriazole, and cyanoacrylate.

Examples of the flame retardant include phosphoric acid esters, phosphoric acid esters containing halogen, organic flame retardants such as aromatic halogens, antimony trioxide (Sb ₂ O ₃ ), barium metaborate (Ba (BO) ₂ )
₂ ) or aluminum hydroxide (Al (OH) ₃ )
And inorganic flame retardants. Examples of the hydrogen halide scavenger include an alkaline compound and an organic compound having an epoxy ring.

Such an electrode additive can be manufactured by various methods. For example, particles obtained by copolymerizing an unsaturated carboxylic acid are prepared, a base is added thereto, heated, and then neutralized by adding an acid. By this treatment, the particles expand and the carboxyl group precipitates on the surface, but at the same time, small holes are formed inside due to the strain, and eventually a plurality of independent hollow portions 1a are formed.
Thereby, an elastic structure having the hollow portion 1a is obtained.
Also, for example, the seed particles having thermal expansion properties are covered with a coating film made of a polymer material or the like, and the coating film is expanded by heating to expand the seed particles, and the seed particles are reduced by cooling. Thus, the elastic structure 1 having the hollow portion 1a may be manufactured. Furthermore, contents 2
May be dispersed in a polymer material to form the elastic structure 1 so as to surround the contents 2.

Such an electrode additive is preferably used, for example, in a secondary battery containing an electrode material whose volume changes with charge and discharge. An example will be described below.

FIG. 4 shows a sectional structure of a secondary battery using the electrode additive according to the present embodiment. The one shown in FIG. 4 is a so-called coin type. In this secondary battery, a disc-shaped negative electrode 12 housed in an outer cup 11 and a disc-shaped positive electrode 14 housed in an outer can 13 are laminated with a separator 15 interposed therebetween. The interiors of the outer cup 11 and the outer can 13 are filled with the electrolytic solution 16, and the periphery of the outer cup 11 and the outer can 13 are sealed by being caulked via an insulating gasket 17.

The negative electrode 12 is, for example, a negative electrode mixture layer 12a.
And a negative electrode current collector layer 12b made of metal foil or the like provided on the exterior cup 11 side of the negative electrode mixture layer 12a. The negative electrode mixture layer 12a includes, for example, a negative electrode material capable of inserting and extracting lithium ions, the electrode additive according to the present embodiment, and, if necessary, a binder. Thus, in this secondary battery, the electrode additive plays the role of a spacer, and the high elasticity of the electrode additive can be used to absorb a change in the volume of the negative electrode material in a charge / discharge cycle.

Examples of the negative electrode material capable of inserting and extracting lithium ions include metals and semiconductors capable of forming alloys and compounds with lithium, and alloys and compounds thereof. This alloy or compound is represented, for example, by the chemical formula M _Ix M _IIy Li _z . In this formula, M _I represents at least one of lithium and alloys and compounds capable of forming metal elements and semiconductor elements, M _II is at least one of metal elements other than lithium and M _I and the semiconductor element Represents The values of x, y and z are x> 0, y ≧ 0, and z ≧ 0, respectively.

Examples of such metals or semiconductors, or alloys or compounds thereof, include magnesium (Mg), boron (B), aluminum (Al),
Gallium (Ga), indium (In), silicon (S
i), germanium (Ge), tin (Sn), lead (P
b), arsenic (As), antimony (Sb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Z
n), hafnium (Hf), zirconium (Zr) or yttrium (Y), or alloys or compounds thereof. Specific examples of these alloys or compounds include LiAl and LiAlM _III.
(However, M _III is at least one of metal elements and semiconductor elements of Group 2A, 3B and 4B), AlSb and CuMgSb.

Among them, as a metal element or a semiconductor element capable of forming an alloy or a compound with lithium, 4
Group B metal elements or semiconductor elements are preferred, particularly preferably silicon or tin, and most preferably silicon. These alloys or compounds are also preferred,
Specifically, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂
Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi
₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ S
i, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaS
i ₂ , VSi ₂ , WSi ₂ or ZnSi ₂ .

Other examples of the negative electrode material capable of inserting and extracting lithium ions include at least one nonmetallic element and at least one kind of 4B excluding carbon (C).
And a compound containing a group element. Note that this compound may include at least one of a metal element other than Group 4B including lithium and a semiconductor element. Such compounds include, for example, SiC, Si ₃ N ₄ ,
Si ₂ N ₂ O, Ge ₂ N ₂ O, SiO _x (0 <x ≦
2), SnO _x (0 <x ≦ 2), LiSiO or L
iSnO.

Further, as a negative electrode material capable of inserting and extracting lithium ions, a low-crystalline carbon material obtained at a relatively low temperature of 2000 ° C. or lower, or a raw material which is easily crystallized, is treated at a high temperature of about 3000 ° C. And highly crystalline carbon materials. Examples of such carbon materials include pyrolytic carbons, cokes, artificial graphites,
Examples include natural graphites, glassy carbons, organic compound fired bodies, carbon fibers and activated carbon. Among them, cokes include pitch coke, needle coke and petroleum coke. The organic compound fired body is obtained by firing a furan resin or the like at an appropriate temperature and carbonizing it.

The negative electrode 12 may contain any one of the above-described materials as a negative electrode material capable of inserting and extracting lithium ions, or may contain a mixture of two or more thereof. Is also good.

The positive electrode 14 is made of, for example, a positive electrode mixture layer 14a.
And a positive electrode current collector layer 14b made of a metal foil or the like provided on the outer can 13 side of the positive electrode mixture layer 14a. The positive electrode mixture layer 14a includes, for example, a positive electrode material, the electrode additive according to the present embodiment, and, if necessary, a binder and a conductive agent. That is, as in the case of the negative electrode 12, the electrode additive can absorb a change in volume of the positive electrode material in a charge / discharge cycle.

As the positive electrode material, for example, TiS ₂ , M
oS ₂ , NbSe ₂ , V ₂ O _{5 and} other lithium-free metal sulfides or metal oxides, or lithium-containing lithium composite sulfides or lithium composite oxides. They may be used as a mixture. In particular, to increase the energy density, Li
preferably contains a lithium composite oxide mainly composed of _x M _IV O _2. Note that M _IV is preferably one or more transition metal elements, specifically, at least one of cobalt (Co), nickel (Ni), and manganese (Mn). Further, x is usually 0.05 ≦ x ≦
It is a value within the range of 1.10. Specific examples of such a lithium composite oxide include LiCoO ₂ and LiNi.
O ₂ , Li _x Ni _y Co _{1 -y} O ₂ (however, the values of x and y vary depending on the charge / discharge state of the battery, and usually 0 <x <
1, 0.7 <y <1.02) or a lithium manganese composite oxide having a spinel structure.

The separator 15 separates the negative electrode 12 and the positive electrode 14 from each other, and prevents a current short circuit by contact between the two electrodes.
It allows lithium ions to pass through and is made of, for example, a porous film made of polypropylene.

The electrolytic solution 16 is obtained by dissolving an electrolyte salt in a non-aqueous solvent. As the non-aqueous solvent, for example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3- Dioxolan, 4-methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, acetate or propionate are suitable, and two or more of these are used in combination. You may.

As the electrolyte salt, for example, LiCl
O ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB
(C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ L
i, LiCl or LiBr is suitable, and two or more of these may be used in combination.

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

First, a positive electrode material such as a lithium composite oxide, the electrode additive according to the present embodiment, and a conductive agent and a binder are mixed as necessary to prepare a positive electrode mixture, and the solvent is used as a solvent. Disperse into a paste-like positive electrode mixture slurry. The positive electrode mixture slurry is applied to the positive electrode current collector layer 14b, dried, and then compression molded by a roller press or the like to form the positive electrode mixture layer 14a, and the positive electrode 14 is manufactured.

Next, a negative electrode material capable of inserting and extracting lithium, an electrode additive according to the present embodiment,
If necessary, a binder is mixed to prepare a negative electrode mixture, and the mixture is dispersed in a solvent to form a paste-like negative electrode mixture slurry. The negative electrode mixture slurry is applied to the negative electrode current collector layer 12b and dried, and then compression-molded by a roller press or the like to form the negative electrode mixture layer 12a, thereby producing the negative electrode 12.

Subsequently, the positive electrode 14, the separator 15, the negative electrode 12, and the outer cup 11 are laminated in this order inside the outer can 13, and the electrolytic solution 16 is injected into the outer can 11, and then the insulating gasket 17 is interposed. The outer can 11 is swaged. Thereby, the secondary battery shown in FIG. 4 is obtained.

This secondary battery operates as follows.

In this secondary battery, when charged, the positive electrode 1
Lithium ions are desorbed from 4, pass through the separator 15 via the electrolytic solution 16, and are occluded in the negative electrode 12. Thereafter, when discharging is performed, lithium ions are desorbed from the negative electrode 12, pass through the separator 15 via the electrolytic solution 16, and return to the positive electrode 14. At that time, since the positive electrode 14 and the negative electrode 12 contain the electrode additive according to the present embodiment, even if the positive electrode material and the negative electrode material expand and contract by absorbing and releasing lithium ions, the Absorbs the change in volume, and the physical shapes of the positive electrode 14 and the negative electrode 12 are maintained.

As described above, according to the electrode additive according to the present embodiment, since the elastic structure 1 having the hollow portion 1a is provided, higher elasticity can be obtained. Therefore, if the positive electrode 14 or the negative electrode 12 of the secondary battery is configured using this electrode additive, a change in volume of the electrode material during the charge / discharge cycle can be absorbed, and the physical shape of the electrode is maintained. be able to. Therefore, even if the charge and discharge cycle is repeated, a decrease in the energy density can be suppressed, and high charge and discharge cycle characteristics can be obtained.

If the content 2 contains a dehydrating agent, a radical scavenger, a flame retardant, a hydrogen halide scavenger, or the like, the action thereof can enhance the battery characteristics or safety. In addition, since the contents 2 are covered with the elastic structure 1, the material can be selected without concern for the potentials of the positive electrode 14 and the negative electrode 12, and the range of material selection is widened, and higher effects are obtained. be able to. However, the material used for the elastic structure 1 must be electrochemically stable at the potential of the electrode to be added.

Furthermore, if the elastic structure 1 is made of a material which melts at the temperature at which the flame retardant is to function while the flame retardant is contained in the contents 2, if the temperature rises, a dangerous state may occur. Only the flame retardant can function. Therefore, the battery characteristics are not deteriorated by the flame retardant, the range of choice of the flame retardant is widened, and the flame retardant can function more effectively.

[0045]

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

In Example 1, unsaturated polyester particles were first synthesized by a polycondensation reaction of maleic acid, fumaric acid and diethylene glycol, and the resulting mixture was treated with a 0.2% aqueous sodium hydroxide (NaOH) solution at 60 ° C. for 24 hours. A base treatment with heating was performed. The particles are then reduced to 0.1%
After neutralization with an aqueous solution of hydrogen chloride (HCl), filtration, vacuum drying, and an electrode additive material having an average particle diameter of 1.2 μm having a gas as a content 2 in the hollow portion 1a of the elastic structure 1 made of unsaturated polyester I got

Using this electrode additive, a secondary battery as shown in FIG. 4 was manufactured. Here, the description will be made using the same reference numerals as those shown in FIG. First, oxygen cross-linking is performed by introducing 10 to 20% of a functional group containing oxygen into petroleum pitch, followed by baking at 1000 ° C. in an inert gas.
A low crystalline carbon material having properties close to glassy carbon was obtained. X-ray diffraction measurement of this low-crystalline carbon material revealed that the (002) plane spacing was 0.376 nm, and the true density was determined according to “True density by butanol method” to be 1.58 g / cm. ^{Was 3} .

Next, the low-crystalline carbon material is pulverized into a powder having an average particle diameter of 50 μm.
0 parts by weight and a silicon compound (Mg ₂ S) having an average particle size of 5 μm.
i) 35 parts by weight of powder and chloroprene as a binder
5 parts by weight and 0.5 parts by weight of the electrode additive were mixed to prepare a negative electrode mixture. Subsequently, the negative electrode mixture was dispersed in cyclohexanone as a solvent to form a negative electrode mixture slurry, and then uniformly applied to one surface of a negative electrode current collector layer 12b made of a copper foil having a thickness of 10 μm, dried, and dried. The negative electrode mixture layer 12a was formed by compression molding using a press. Thereafter, this was punched out to produce a disc-shaped negative electrode 12 having a diameter of 15.5 cm.

Further, lithium carbonate (Li ₂ CO ₃ ) and nickel carbonate (NiCO ₃ ) are combined with Li ₂ CO ₃ : NiC
O ₃ was mixed at a ratio of 0.5: 1 (molar ratio) and calcined in air at 900 ° C. for 5 hours to obtain a lithium nickel composite oxide (LiNiO ₂ ). Next, 90 parts by weight of the lithium nickel composite oxide and graphite 6 as a conductive agent were added.
Parts by weight, carboxymethylcellulose 0.7 part by weight as a thickener, and 3 parts by weight of an aqueous dispersion of polyvinylidene fluoride as an adhesive in solid content,
0.3 part by weight of the electrode additive was mixed to prepare a positive electrode mixture. Subsequently, the positive electrode mixture was dispersed in ion-exchanged water to form a positive electrode mixture slurry, which was then uniformly applied to one surface of a positive electrode current collector layer 14b made of an aluminum foil having a thickness of 20 μm, dried, and subjected to roller pressing. The positive electrode mixture layer 14a was formed by compression molding with a machine. Thereafter, this was punched out to produce a disk-shaped positive electrode 14 having a diameter of 15.2 cm.

After producing the positive electrode 14 and the negative electrode 12, respectively, the positive electrode 14, 25 μm thick
1 made of a microporous polypropylene film
5 and the negative electrode 12 were laminated while the electrolytic solution 16 was dropped. The electrolytic solution 16 contains 50% by volume of propylene carbonate.
And a non-aqueous solvent mixed with 50% by volume of diethyl carbonate,
LiPF ₆ dissolved at 1.0 mol / dm ³ was used. Thereafter, the exterior cup 11 was placed on the negative electrode 12, and the periphery of the exterior can 11 was caulked via the insulating gasket 17 to obtain a secondary battery.

In Example 2, 150 ml of a 10% aqueous alginate solution and 30 ml of a flame retardant, triphenyl phosphite, were dispersed with high-speed stirring and sprayed into a 10% aqueous calcium chloride solution to form an elastic gel comprising a calcium alginate gel. An electrode additive material having triphenyl phosphite in the hollow portion 1a of the structure 1 and having an average particle diameter of 2.0 μm was obtained. Using this electrode additive, a secondary battery was fabricated in the same manner as in Example 1.

As a comparative example with respect to Examples 1 and 2, a secondary battery was manufactured in the same manner as in Example 1 except that the electrode additive was replaced with a binder for each of the negative electrode and the positive electrode.

The obtained secondary batteries according to Examples 1 and 2 and Comparative Example were subjected to cycle characteristic evaluation and heating test, respectively. In the cycle characteristic evaluation, charge / discharge was repeated up to 100 cycles under certain conditions, and the ratio of the volume energy density for each cycle based on the volume energy density of the second cycle, that is, the capacity retention ratio was determined.
At this time, the charging was performed at a constant current of 1 mA and the battery voltage was reduced to 2.5 V at a constant current of 1 mA until the battery voltage reached 4.2 V.
V was reached. The results are shown in FIG. As can be seen from FIG. 5, Examples 1 and 2 are 1 more than the comparative example.
At the time of 00 cycles, the capacity retention ratio was improved by about 20%. That is, it was found that the cycle characteristics could be improved by using the electrode additive of this example.

In the heating test, the battery voltage was 4.2 V
, And placed on a hot plate heated to 160 ° C. to check for ignition. As a result, ignition was observed in the secondary batteries of Example 1 and the comparative example, whereas the secondary battery of Example 2 did not. That is, it was found that a flame retardant effect was obtained when the hollow portion 1a of the elastic structure 1 contained a flame retardant as the content 2.

Although not specifically described here,
Even when the content 2 contains a dehydrating agent, a radical scavenger or a hydrogen halide scavenger, those effects can be similarly obtained.

As described above, the present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and can be variously modified. For example, in the above embodiment, the case where the entire hollow portion 1a is covered by the elastic structure 1 has been described, but an opening for opening the hollow portion may be formed in a part of the elastic structure. .

In the above embodiment, the negative electrode 1
Although the case where the electrode additive material is included in both the positive electrode 2 and the positive electrode 14 has been described, only one of them may be included. Further, in the above-described embodiment, the material forming the negative electrode 12 and the material forming the positive electrode 14 are specifically described. However, the material may be formed from other materials.

In addition, in the above-described embodiment, the secondary battery using the electrolytic solution which is a liquid electrolyte has been described. However, in the present invention, the non-aqueous solvent in which the electrolyte salt is dissolved is held in the polymer compound. Other electrolytes such as a gelled electrolyte, a solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, or an electrolyte in which an electrolyte salt is held in a solid inorganic conductor. The present invention can be applied to the used secondary battery.

Furthermore, in the above embodiment, the secondary battery using lithium ions as the electrode reactive species has been described, but the present invention can be widely applied to other secondary batteries. For example, sodium (Na)
Alternatively, a secondary battery using ions of another alkali metal such as potassium (K), an alkaline earth metal such as magnesium (Mg) or calcium (Ca), or another light metal such as aluminum (Al) as an electrode reactive species Can also be applied. Furthermore, the present invention can be applied to a primary battery.

In addition, in the above embodiment,
Although the coin type secondary battery has been described, the present invention can be similarly applied to a battery having a shape such as a button type, a paper type, a square type, or a cylindrical type having a spiral structure.

[0061]

As described above, according to the electrode additive according to any one of the first to third aspects, since the elastic structure having the hollow portion is provided, higher elasticity can be obtained. This has the effect that it can be obtained.

In particular, according to the electrode additive according to the third aspect, the contents have at least one of a dehydration function, a radical scavenging function and a hydrogen halide scavenging function. The effect that characteristics or safety can be improved is produced. In addition, since the contents are covered with the elastic structure, there is no need to consider potential when selecting a material, and the selection range of a dehydrating agent, a radical scavenger, a flame retardant, or a hydrogen halide scavenger is expanded, and more. It also has an effect that a high effect can be obtained.

According to the secondary battery of any one of claims 4 to 6, at least one of the positive electrode and the negative electrode contains the electrode additive of the present invention, so that charging and discharging are performed. The change in volume of the electrode material during the cycle can be absorbed, and the physical shape of the electrode can be maintained. Therefore, even if the charge / discharge cycle is repeated, a decrease in the energy density can be suppressed, and an effect that high charge / discharge cycle characteristics can be obtained is achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an electrode additive according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a modification of the electrode additive shown in FIG.

FIG. 3 is a cross-sectional view for explaining a modification of the electrode additive shown in FIG.

FIG. 4 is a cross-sectional view illustrating a configuration of a secondary battery using an electrode additive according to one embodiment of the present invention.

FIG. 5 is a characteristic diagram showing cycle characteristics of the secondary battery according to the example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Elastic structure, 1a ... Hollow part, 2 ... Contents, 11 ... Exterior cup, 12 ... Negative electrode, 12a ... Negative electrode mixture layer, 12b ...
Negative electrode current collector layer, 13: outer can, 14: positive electrode, 14a: positive electrode mixture layer, 14b: positive electrode current collector layer, 15: separator,
16 ... electrolyte, 17 ... insulating gasket

Claims (6)

[Claims] 1. An electrode additive comprising an elastic structure having a hollow portion. 2. The electrode additive according to claim 1, wherein a content is provided in a hollow portion of the elastic structure. 3. The electrode additive according to claim 2, wherein the content has at least one of a dehydration function, a radical trapping function, a flame retardant function, and a hydrogen halide trapping function. 4. A secondary battery provided with a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode includes an electrode additive having an elastic structure having a hollow portion. Rechargeable battery. 5. The secondary battery according to claim 4, wherein the positive electrode contains a lithium-containing oxide. 6. The secondary battery according to claim 4, wherein the negative electrode includes a negative electrode material capable of inserting and extracting lithium ions.