JP3002123B2 - Organic electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic electrolyte battery having a high capacity and a high voltage.

[0002]

2. Description of the Related Art In recent years, a secondary battery using a conductive polymer, a transition metal oxide or the like as a positive electrode and a lithium metal or a lithium alloy as a negative electrode has a high energy density. Has been proposed as an alternative to lead batteries.

[0003]

However, this secondary battery has a practical problem that the charge or discharge is repeatedly performed to deteriorate the positive electrode or the negative electrode, and the capacity is greatly reduced. In particular, the deterioration of the negative electrode is accompanied by the formation of moss-like lithium crystals called dentite, and the repetition of charge and discharge eventually causes the dentite to penetrate the separator and cause a short circuit inside the battery, and in some cases, the battery Explosion and other safety issues occurred.

In recent years, in order to solve the above-mentioned problems, a battery using a carbon material such as graphite for a negative electrode and using a lithium-containing metal oxide such as LiCoO _{2 for} a positive electrode has been proposed. This battery is a so-called rocking chair type battery in which lithium is supplied from the lithium-containing metal oxide of the positive electrode to the negative electrode by charging after the battery is assembled, and the negative electrode lithium is returned to the positive electrode in discharging. However, although this battery has a high voltage and a high capacity, its capacity is about 80 to 90 mAh / cc at the maximum (based on the total volume of the electrodes, separators, and current collectors), which is a characteristic of lithium batteries. Energy density has not been obtained.

On the other hand, a heat-treated product of an aromatic condensed polymer having a hydrogen atom / carbon atom ratio of 0.50 to 0.0
The insoluble and infusible substrate having a polyacene-based skeleton structure of No. 5 is capable of doping lithium in a larger amount than a general carbon material. When the rocking chair type battery is assembled by using the insoluble and infusible substrate as a negative electrode and a lithium-containing oxide for a positive electrode, a battery having a higher capacity than that using a carbon material can be obtained. However, the capacity was unsatisfactory.

In order to solve such a problem, the same applicant as the present application has filed Japanese Patent Application No. 5-259403.
An organic electrolyte battery filed under the application No. has been developed.
That is, this organic electrolyte battery is a positive electrode, a negative electrode and an organic electrolyte battery provided with an aprotic organic solvent solution of a lithium salt as an electrolytic solution, wherein the positive electrode contains a metal oxide,
The negative electrode is a heat-treated product of an aromatic condensed polymer and is an insoluble infusible substrate having a polyacene skeleton structure in which the atomic ratio of hydrogen atoms / carbon atoms is 0.50 to 0.05; An organic electrolyte battery characterized in that the total amount of lithium contained in the battery is not less than 500 mAh / g and the amount of lithium derived from the negative electrode is not less than 100 mAh / g with respect to the conductive substrate. However, although this battery has a high capacity, it has a problem that the negative electrode PAS has no practical and simple method for supporting lithium derived from the negative electrode. For example, it is possible to experimentally reduce the thickness of a lithium metal foil.
In the case where such a lithium foil is adhered to and supported on an electrode, the thickness of the negative electrode becomes large, and for example, there is a disadvantage that it is difficult to assemble a wound-type battery. Naturally, even in the case of assembling a battery in which the electrode is not wound, if the electrode thickness is too large, it is inevitable that a problem is left in the speed characteristics and the like.

In view of the above problems, the present inventors have made intensive studies and completed the present invention. The present invention provides a secondary battery having a high capacity and a high voltage and easy to manufacture. An object of the present invention is to provide a battery, and further to provide a secondary battery having a low internal resistance.

[0008]

In order to achieve the above object, the present invention has the following arrangement. That is, a positive electrode, a negative electrode and an organic electrolyte battery provided with an aprotic organic solvent solution of a lithium salt as an electrolytic solution, at least the negative electrode comprises an electrode group in which a plurality of electrodes are stacked,
The negative electrode current collector has a hole penetrating the front and back surfaces,
An organic electrolyte battery having an overall porosity of 10% or more. Further, it is preferable that the total amount of lithium contained in the battery is not less than 500 mAh / g and the amount of lithium derived from the negative electrode is not less than 100 mAh / g with respect to the negative electrode active material. It is particularly preferable that the heat-treated product is a insoluble infusible substrate having a polyacene skeleton structure in which the atomic ratio of hydrogen atoms / carbon atoms is 0.50 to 0.05. Also,
Preferably, the positive electrode comprises an electrode group in which a plurality of electrodes are superimposed, the positive electrode current collector includes holes penetrating the front and back surfaces, and the entire porosity is 10% or more. If the metal oxide is contained, a high-capacity, high-voltage battery is obtained, which is particularly preferable. When lithium metal is interposed between the negative electrode groups, a battery with low internal resistance is obtained, which is preferable.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of a basic configuration of a battery according to the present invention. In this figure, (1), (1 ′)
(1 '') is a single negative electrode, and two or more (three in the figure) are stacked to form a negative electrode group.
(2) and (2 ′) are a positive electrode group or a positive electrode group including a plurality of positive electrodes. The positive electrode or the positive electrode group and the negative electrode group face each other via a separator (3) impregnated with an electrolyte. I have. The separator (3) is a porous body that is durable with respect to an electrolytic solution or an electrode active material, has continuous air holes, and has no electron conductivity.
A cloth, nonwoven fabric or porous body made of polyethylene or polypropylene is used. The thickness of the separator (3) is preferably thin in order to reduce the internal resistance of the battery, but can be appropriately set in consideration of the amount of retained electrolyte, flowability, strength, and the like. The electrolyte is usually a liquid, but may be used in the form of a gel or a solid. The positive and negative electrodes (1) and (2) and the separator (3) are fixed in the battery case (4) so as not to cause a practical problem. The shape and size of the electrodes are appropriately set according to the shape and performance of the intended battery.

[0010] (5) is a negative electrode current collector having holes penetrating the front and back surfaces, and having a porosity of 10% or more as a whole. Examples of the shape of the current collector (5) include an expanded metal shape, a punched shape, a mesh (net) shape, a foamed shape, and the like. In any case, the current collector (5) has a hole penetrating the front and back surfaces. In addition, the porosity is required to be 10% or more. That is, if the porosity is 10% or less, the internal resistance of the battery becomes too large. The porosity of the current collector is obtained by converting the ratio of (current collector weight / true specific gravity) / (apparent volume) into a percentage.

(6) and (6 ') are negative electrode current collectors or lead terminals for taking out current to the outside. The lead terminals (6) and (6') include, for example, carbon, Platinum, nickel, stainless steel, copper, etc. can be used,
By forming a single electrode on both sides or one side of the current collector, it can be used as a current collector integrated electrode. Although the thickness of the electrode is not particularly limited, the total thickness of the electrode group is 200
When the thickness is not less than μm, more preferably not less than 300 μm, for example, the effect is increased when a winding type battery configuration is adopted, which is preferable.

The negative electrode of the present invention preferably has a discharge capacity of at least 400 mAh / cc with respect to the volume of the negative electrode active material, and is a heat-treated aromatic condensed polymer having an atomic ratio of hydrogen atoms / carbon atoms of 0. Insoluble and infusible substrate having a polyacene-based skeleton structure of 50 to 0.05 (hereinafter referred to as PA)
When S is used, a secondary battery having a high discharge capacity of 400 mAh / cc or more with respect to the volume of the negative electrode active material is obtained, which is preferable. The aromatic condensation polymer is a condensation product of an aromatic hydrocarbon compound and an aldehyde. As the aromatic hydrocarbon compound, it is preferable to use so-called phenols such as phenol, cresol and xylenol. For example,

Embedded image (Where x and y are each independently 0, 1 or 2
Methylene bisphenols represented by the formula: or hydroxy biphenyls or hydroxynaphthalenes. Of these, phenols, particularly phenol, are practically preferred.

Further, as the aromatic condensation polymer,
A modified aromatic condensation polymer in which a part of the above aromatic hydrocarbon compound having a phenolic hydroxyl group is substituted with an aromatic hydrocarbon compound having no phenolic hydroxyl group, for example, xylene, toluene, aniline, etc., for example, phenol and xylene And formaldehyde, and a modified aromatic polymer substituted with melamine or urea. Further, a furan resin can also be suitably used. Further, as the aldehyde, aldehydes such as formaldehyde, acetaldehyde, and furfural can be used, and among them, formaldehyde is particularly preferable. Further, the phenol formaldehyde condensate may be any of a novolak type, a resol type or a mixture thereof.

[0014] The PAS is an aromatic condensed polymer.
Is obtained by heat-treating
And PAS having a polyacene-based skeleton structure described in Japanese Patent Publication No. 3-24024 and the like can be used, and can be produced, for example, as follows. That is, the aromatic condensed polymer is gradually heated in a non-oxidizing atmosphere (including vacuum) to an appropriate temperature in the range of 400 to 800 ° C., so that the hydrogen atom / carbon atom ratio ( H / C) is 0.50 to 0.
05, preferably 0.35 to 0.10. Further, a PAS having a specific surface area of 600 m ² / g or more by a BET method can also be obtained by a method described in Japanese Patent Publication No. 3-24024. That is, a solution containing an initial condensate of an aromatic condensed polymer and an inorganic salt such as zinc chloride is prepared, and the solution is heated and cured in a mold. The cured product thus obtained is gradually heated in a non-oxidizing atmosphere (including vacuum) to a temperature of 350 to 800 ° C, preferably to an appropriate temperature in the range of 400 to 750 ° C, and then water or By sufficiently washing with dilute hydrochloric acid or the like, the above-mentioned H / C is obtained, and
PA having a specific surface area of 0 m ² / g or more by the BET method
S can also be obtained.

The PAS thus obtained is
According to X-ray diffraction (CuKα), the position of the main peak is present at 24 ° or less in 2θ, and in addition to this main peak, another broad peak is present between 41 and 46 °. It exists. This PAS has a polyacene skeleton structure in which an aromatic polycyclic structure is appropriately developed,
In addition, it is suggested to have an amorphous structure, and is useful as a battery active material because lithium can be stably doped.

When the above H / C exceeds 0.50,
Since the aromatic polycyclic structure is not sufficiently developed, doping and undoping of lithium are not smoothly performed.
It is not preferable because the charging / discharging efficiency when the battery is assembled is reduced. On the other hand, when H / C is 0.05 or less, the capacity of the battery is undesirably reduced.

The negative electrode of the organic electrolyte battery according to the present invention is made of, for example, the above-mentioned PAS, and is formed by molding a PAS having a shape such as a powder, a granule, and a short fiber which is easy to mold with a binder. As the binder, a fluorinated resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene can be used.
More preferably, a fluorine-based binder having an atomic ratio of fluorine atoms / carbon atoms (hereinafter, referred to as F / C) of 0.75 or more and less than 1.50, particularly fluorine of 0.75 or more and less than 1.30 A system binder is preferred. As the fluorine-based binder, for example, polyvinylidene fluoride, vinylidene fluoride-3 ethylene copolymer, ethylene-4
Examples thereof include a fluorinated ethylene copolymer and a propylene-tetrafluoroethylene copolymer, and a fluorinated polymer in which hydrogen in the main chain is substituted with an alkyl group can also be used.
In the case of the above polyvinylidene fluoride, F / C is 1,
In the case of vinylidene fluoride-3fluoroethylene copolymer,
When the molar fraction of vinylidene fluoride is 50% and 80%, the respective F / Cs are 1.25 and 1.10.
Further, in the case of a propylene-tetrafluoroethylene copolymer, the F / C when the mole fraction of propylene is 50% is 0.75.
Becomes Among them, polyvinylidene fluoride and a vinylidene fluoride-3fluoroethylene copolymer having a molar fraction of vinylidene fluoride of 50% or more are preferable, and polyvinylidene fluoride is practically preferable. Thus, when these binders are used, the lithium doping ability (capacity) of PAS can be sufficiently utilized.

Further, as the positive electrode of the organic electrolyte battery of the present invention, the effect of the present invention is large in a high capacity battery system,
For example, Li _X CoO _2, Li _X NiO _2, Li _X Mn
O _2, Li _X FeO _2, etc. Li _X M _y O _Z (M is a metal,
A lithium-containing metal oxide which can be electrochemically doped or undoped, or a transition metal oxide such as cobalt, manganese or nickel. It is preferable to use a lithium-containing oxide having a voltage of 4 V or more with respect to lithium metal. The positive electrode is formed by adding a positive electrode active material and, if necessary, a conductive material and a binder.
The composition and the like may be set as appropriate. That is, the type of the conductive agent may be metal powder such as metal nickel, but it is particularly preferable that the conductive agent is a carbon-based material such as activated carbon, carbon black, acetylene black, and graphite. The mixing ratio varies depending on the electric conductivity of the active material, the electrode shape, and the like, but it is appropriate to add 2 to 40% to the active material. The binder may be any one that is insoluble in the electrolyte solution described below, and is, for example, a rubber-based binder such as SBR, a fluorinated resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene. Resins are preferably used, and the mixing ratio is preferably 20% or less.

The positive and negative electrode shapes are as follows:
Depending on the intended battery, various shapes such as a plate shape, a film shape, a column shape, or a metal foil shape can be adopted. Among them, those formed into a metal foil shape are particularly useful as a current collector integrated electrode that can be applied to various batteries.

The capacity of the organic electrolyte battery according to the present invention can be improved by appropriately controlling the amount of lithium contained in the battery. When the amount of lithium is 500 mAh /
g or more and lithium derived from the negative electrode is 100 mAh
/ G or more. Here, the total amount of lithium in the battery means the total of lithium derived from the positive electrode, lithium derived from the electrolyte, and lithium derived from the negative electrode. The lithium derived from the positive electrode is lithium contained in the positive electrode at the time of assembling the battery, and a part or all of the lithium is subjected to an operation of passing current from an external circuit (eg, charging)
Is supplied to the negative electrode. Further, the lithium derived from the electrolyte is lithium in the electrolyte contained in the separator, the positive electrode, the negative electrode, and the like, and the lithium derived from the negative electrode is lithium supported on the negative electrode, And lithium other than lithium derived from the electrolyte. The method of supporting lithium on the negative electrode is not particularly limited as long as lithium can be supported on the negative electrode before assembling the battery. A method can be adopted in which the metal is conducted, and lithium is doped to the negative electrode in the battery. In this case, a lithium metal is interposed between the single electrodes in the electrode group of the present invention, and further, a current collector having a porosity of 10% or more and penetrating the front and back surfaces used as the negative electrode current collector of the present invention It is also possible to obtain a battery with low internal resistance by attaching lithium metal to the metal or sandwiching it between embedded single electrodes.

An aprotic organic solvent is used as a solvent constituting the electrolytic solution used in the organic electrolyte battery of the present invention. Examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolan, methylene chloride, sulfolane, and the like. Further, a mixture of two or more of these aprotic organic solvents can also be used. The electrolyte mixed or dissolved in a single solvent may be any electrolyte capable of generating lithium ions. Such electrolytes include, for example, LiI, LiClO ₄ , LiAs
F ₆ , LiBF ₄ , LiPF ₆ , LiHF _{2 and the} like. The electrolyte and the solvent are mixed in a sufficiently dehydrated state to form an electrolyte. The concentration of the electrolyte in the electrolyte is at least 0.1 mol in order to reduce the internal resistance due to the electrolyte. / L or more, more preferably 0.2 to 1.5 mol / l.

The shape of the organic electrolyte battery of the present invention is as follows.
The shape is not limited to a cylindrical shape, and may be any shape such as a square shape and a box shape.

[0023]

According to the organic electrolyte battery of the present invention, the negative electrode is composed of an electrode group in which a plurality of electrodes are overlapped, and the negative electrode current collector has holes penetrating the front and back surfaces and has an overall porosity of 10%. % Or more, so that winding can be performed regardless of the thickness of the electrode. In addition, since lithium can be previously supported on the negative electrode by using, for example, metal lithium having a size of 70 μm or more, it is possible to obtain a high-capacity, high-voltage battery that is easy to manufacture. Furthermore, since the negative electrode has a structure in which a plurality of electrodes are overlapped, metallic lithium can be sandwiched between the electrode groups, and lithium can be supported on the negative electrode in advance, so that a battery with low internal resistance can be obtained. Becomes

[0024]

【Example】

Example 1 A phenolic resin molded plate having a thickness of 0.5 mm was placed in a siliconite electric furnace at 10 ° C. /
The temperature was raised at the rate of time and heat-treated to 650 ° C. to synthesize PAS. The thus obtained PAS plate was pulverized with a disk mill to obtain a PAS powder having an average particle size of about 8 μm. This H / C was 0.22. Next, the obtained P
AS powder 100 parts by weight, polyvinylidene fluoride powder 10
By weight, N-methylpyrrolidone was mixed to obtain a slurry, and this slurry was used to have a thickness of 50 μm and a porosity of 72.
% Of the copper expanded metal was formed on both surfaces to obtain a negative electrode having a thickness of 100 μm. Also, LiCoO ₂ 100
Parts, 5 parts of graphite, and 5 parts by weight of polytetrafluoroethylene powder were sufficiently kneaded to obtain a mixture having a thickness of 300 μm.
An electrode layer was formed on both surfaces of a stainless steel (SUS444) expanded metal having a porosity of 82% to obtain a positive electrode having a thickness of 800 μm. Thus, the negative electrode is formed by stacking five negative electrodes to form a negative electrode group.
When wound together with the above-mentioned positive electrode through a microporous polypropylene separator having a thickness of 25 μm, both electrodes could be easily wound with almost no cracks or the like.

[Comparative Example 1]
When a 00 μm electrode was obtained and the positive electrode and the negative electrode were rolled in in the same manner as in Example 1, the negative electrode was cracked and could not be rolled smoothly.

Example 2 A double-sided electrode having a thickness of 250 μm was obtained using the slurry of Example 1 and copper expanded metal. Further, using the same mixture as in Example 1, a thickness of 250
An electrode layer is formed on both surfaces of a stainless steel (SUS444) expanded metal having a porosity of 85% and a porosity of 85%, and a thickness of 400 μm.
m of the positive electrode were obtained. 80μm thick lithium metal foil with thickness 5
A copper expanded metal having a porosity of 0 μm and a porosity of 72% was filled with a roller to a thickness of 100 μm (lithium unit), sandwiched between negative electrodes, and assembled into a battery as shown in FIG. That is, in FIG.
(1 ″) is a negative electrode single electrode, (2) and (2 ′) are positive electrodes, and (8) is a lithium unit. At this time, the size of the electrode was 1.5 × 3 cm ² , and a 25 μm microporous polypropylene separator was used as the separator (3). In addition, 1 M / l LiPF
₆ was dissolved in propylene carbonate.
The lithium derived from the negative electrode is 360 m from the negative electrode active material PAS.
Ah / g, and the total lithium content in the battery is 1400 mAh
/ G. After leaving it for 5 days, the internal resistance was measured and found to be 10Ω. This battery is supplied with a current density of 0.5
After the battery was charged at mA / cm ² until the battery voltage reached 4.2 V, the battery voltage was 2.0 mA at a current density of 0.5 mA / cm ^2.
Discharged until V was reached. The capacity was 101 mAh. [Comparative Example 2] The slurry of Example 1 was used to a thickness of 20 μm.
m double-sided electrode (single side 490)
μm). This is the electrode thickness required to supply the same amount of lithium from the negative electrode as in Example 2 using a mass-producable 80 μm thick lithium metal foil. An electrode layer was formed on both surfaces of a stainless steel (SUS444) expanded metal having a thickness of 500 μm and a porosity of 85% using the same mixture as in Example 1 to obtain a negative electrode having a thickness of 800 μm, as shown in FIG. Battery assembled. In this figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.
In this comparative example, a lithium unit (8) having a thickness of 80 μm and a thickness of 100 μm embedded in a copper expanded metal having a thickness of 50 μm and a porosity of 72% using a roller was attached to the electrode surface. Other than the above, a battery was assembled in the same manner as in Example 2. After standing for 5 days, the internal resistance of the battery was 30Ω, which was higher than that of the example. When charging and discharging were performed in the same manner as in Example 2, the capacity was 170 mA.
h. However, in this case, the thickness of the electrode is twice as large as that of the second embodiment, and corresponds to 85 mAh in the second embodiment.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of an organic electrolyte battery according to the present invention.

FIG. 2 is an explanatory diagram of a basic configuration of an organic electrolyte battery according to an example of the present invention.

FIG. 3 is an explanatory diagram of a basic configuration of an organic electrolyte battery according to a comparative example of the present invention.

[Description of Signs] 1 negative electrode single electrode 1 'negative electrode single electrode 1' 'negative electrode single electrode 2 positive electrode 3 separator 4 battery case 5 negative electrode current collector 6 lead terminal (negative electrode) 6' lead terminal (positive electrode ) 7 Positive electrode current collector 8 Lithium unit

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shizukuni Yada 2-6-113 Miyanishi, Harima-cho, Kako-gun, Hyogo Examiner Mitsuji Uemae (56) References JP-A-7-254416 (JP, A) JP-A-63-259965 (JP, A) JP-A-5-325792 (JP, A) JP-A-3-233860 (JP, A) JP-A-6-203833 (JP, A) JP-A-6-20679 (JP JP, A) JP-A-3-129670 (JP, A) JP-A-58-38466 (JP, A) JP-A-58-18883 (JP, A) JP-A-7-111150 (JP, A) Hei 6-349481 (JP, A) Japanese Utility Model Showa 57-194260 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40 H01M 4/02 H01M 4/70

Claims (6)

(57) [Claims] An organic electrolyte battery comprising a positive electrode, a negative electrode, and a solution of a lithium salt in an aprotic organic solvent as an electrolytic solution, wherein at least the negative electrode comprises an electrode group in which a plurality of electrodes are stacked, and a negative electrode current collector An organic electrolyte battery comprising: a hole penetrating the front and back surfaces; and a porosity of 10% or more. 2. The organic electrolyte battery according to claim 1, wherein the total amount of lithium contained in the battery with respect to the negative electrode active material is 500 mAh / g or more, and lithium derived from the negative electrode is 100 mAh / g or more. 3. The negative electrode is a heat-treated aromatic condensed polymer having an atomic ratio of hydrogen atom / carbon atom of 0.50-0.
The organic electrolyte battery according to claim 1, which is an insoluble infusible substrate having a polyacene-based skeleton structure of No. 05. 4. The positive electrode comprises an electrode group in which a plurality of electrodes are overlapped with each other, wherein the positive electrode current collector has holes penetrating through the front and back surfaces, and has a total porosity of 10% or more. 4. The organic electrolyte battery according to any one of 3. 5. The organic electrolyte battery according to claim 1, wherein the positive electrode is a lithium-containing metal oxide. 6. The organic electrolyte battery according to claim 1, wherein lithium metal is interposed between the negative electrode group.