JPH09120818A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct light a secondary battery with a nonaqueous electrolyte using a lightweight current collector by forming the collectors of the positive and the negative electrode from a conductive film of resin where a conductive metal is provided as the surface layer. SOLUTION: A nonaqueous electrolyte secondary battery concerned is composed of a positive electrode made of Lix MO2 (M is one of the elements Ni, Co, Fe, and Mn) and a negative electrode made of lithium metal, lithium alloy, or a carbonic substance capable of doping and dedoping the lithium. If a conductive film of resin having a conductive metal as the surface layer is used for the current collector of both or either of the positive and negative electrodes, the collector can be made light in weight, which should lead to a lightweight construction of the resultant secondary battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery suitable for use as a power source for small electronic devices such as mobile phones, headphone stereos, CD players and personal computers.

[0002]

2. Description of the Related Art Recently, mobile phones, headphone stereos, and Cs.
The development of small electronic devices such as D players and personal computers has been remarkable, and there is an increasing demand for a small-sized and large-capacity power source used for these purposes. For these applications, lead batteries, NiCd batteries, NiMH batteries having a larger capacity, and lithium ion batteries have been put to practical use.

In particular, lithium ion secondary batteries are the most promising batteries that can be adapted to small and lightweight batteries. LiC on the positive electrode
oO ₂ or LiNiO ₂ , LiMn ₂ O ₄ ,
In order to improve the performance of non-aqueous electrolyte secondary batteries in non-aqueous electrolyte secondary batteries in which metallic lithium or carbon capable of doping / dedoping lithium is used for the negative electrode, thin electrodes with a large electrode area are used. ing.

As a method for producing this thin electrode, an electrode in which a positive electrode or negative electrode active material mixture is applied to a metal foil has been used in recent years in addition to a conventional electrode in which a positive electrode active material mixture is applied to a metal net.

The metal net type electrode has been mainly used for a spiral type battery of a primary battery. On the other hand, the metal foil type electrode has been mainly used for spiral type batteries of non-aqueous batteries.

All of them contributed to the improvement of the discharge performance and storage performance of the non-aqueous electrolyte battery, and exhibited the feature of improving the efficiency of electrode production.

[0007]

However, as the performance of small batteries has been improved in recent years, there has been a demand for weight reduction and increase in discharge capacity of batteries. The weight of a battery using an electrode using a metal net or a metal foil increases, and there is a limit to weight reduction.

[0008] In particular, when the development is promoted from a small battery to a large battery, the volume / weight ratio of the current collector and the metal lead body in the battery increases, and the energy density of the battery decreases. I will end up. In particular, when the battery is upsized, the volume / weight from the current collecting portion to the terminal lead portion increases.

Up to now, these points have not been so seriously concerned, and they have not been taken into consideration in stationary batteries and the like as batteries. It can be said that it will be an extremely important point when developing a mobile power source as a new application.

The present invention has been made in view of the above problems, and an object thereof is to provide a non-aqueous electrolyte secondary battery capable of improving the weight energy density.

[0011]

In the non-aqueous electrolyte secondary battery of the present invention, the positive electrode is Li _x MO ₂ (M = Ni, Co, Fe,
(Selected from Mn) and a lithium metal or a lithium alloy, or a carbon material capable of being doped / dedoped with lithium in the negative electrode, in a non-aqueous electrolyte secondary battery, both positive electrode and / or negative electrode. As the current collector of (1), a conductive thin film having a conductive metal as a surface layer is used for the resin sheet film.

Further, the non-aqueous electrolyte secondary battery of the present invention is a battery having the above-mentioned constitution in which the resin sheet-like film is made of polyester, polyether ether ketone, polyimide or polyolefin.

The non-aqueous electrolyte secondary battery of the present invention is a battery having the above-mentioned structure in which the thickness of the resin sheet film is in the range of 5 to 20 μm.

Further, the non-aqueous electrolyte secondary battery of the present invention is a battery having the above-mentioned structure in which the conductive metal is copper, nickel or aluminum.

Further, the non-aqueous electrolyte secondary battery of the present invention has the above-mentioned structure in which the thickness of the conductive metal is in the range of 0.05 to 2 μm.

According to the non-aqueous electrolyte secondary battery of the present invention, a conductive thin film having a resin sheet-like film and a conductive metal as a surface layer is used as a current collector for both the positive electrode and / or the negative electrode. As a result, the weight of the battery can be reduced, and in particular, compared with a battery using a metal copper foil / net as a current collector, only 1/4 to 1/6 of the current collector portion is compared.
The weight of the current collector can be reduced to some extent.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the non-aqueous electrolyte secondary battery of the present invention will be described below with reference to FIGS. 1 and 2. First, specific contents of Examples 1 to 11 and Comparative Examples 1 to 4 will be described.

Example 1 As a resin sheet-like conductive film, a conductive sheet was produced by forming a film of polyethylene terephthalate (PET) having a thickness of 14 μm for a positive electrode on the both surfaces of which aluminum was formed to a thickness of 500 angstrom by vacuum deposition.

Polyethylene terephthalate (P
ET) A conductive sheet was prepared by forming nickel on a film having a thickness of 14 μm with a thickness of 500 angstroms on both sides by a vacuum deposition method.

As the positive electrode material, a predetermined amount of lithium carbonate and cobalt carbonate were weighed so that the molar ratio of lithium and cobalt was 1: 1 and thoroughly mixed in a mortar, and then 90% in air.
After firing at 0 ° C. for 8 hours, cooling to room temperature, and pulverization, an active material having an average particle diameter of 20 μm was obtained. This active material was a material having a diffraction peak corresponding to LiCoO ₂ by a powder X-ray diffraction method.

91% by weight of this LiCoO ₂ , 6% by weight of graphite as a conductive material, and 3% by weight of polyvinylidene fluoride (PVDF) as a binder were mixed, and N-methyl-2pyrrolidone was added as a dispersion solvent to prepare a positive electrode mixture. It was a paste.

This positive electrode material mixture paste was uniformly applied to both surfaces of the above-mentioned Al vapor-deposited conductive PET sheet and dried to obtain a positive electrode material.

This positive electrode material was pressure-molded with a roller press machine and cut into a predetermined size of width 54 mm and length 470 mm, and one end was made of aluminum and had a thickness of 50 μm and was 4 mm ×.
A 100 mm lead material was bent in two and fixed using a pressurizer having an uneven surface to obtain a positive electrode.

For the negative electrode, petroleum pitch was used as a raw material, and 10 to 20% of a functional group containing oxygen was introduced into this (so-called oxygen cross-linking), followed by heat treatment at 1000 ° C. in an inert gas atmosphere to form glassy carbon. A carbon material with similar properties was obtained. As a result of X-ray diffraction measurement of this material, d (00
The interplanar spacing between the 2) planes was 3.76 angstroms.
This material was crushed to obtain a carbon material powder having an average particle diameter of 20 μm.

The carbon material powder thus obtained was used as a negative electrode active material, and 90% by weight of this powder was mixed with 10% by weight of polyvinylidene fluoride (PVDF) as a binder to prepare a negative electrode mixture. Was dispersed in a dispersion solvent N-methyl-2pyrrolidone to obtain a negative electrode mixture paste.

This negative electrode mixture paste was uniformly applied to both surfaces of the above-mentioned nickel-deposited conductive PET sheet and dried to obtain a negative electrode material. This negative electrode material is pressure-molded by a roller press machine, cut into a predetermined size of width 57 mm and length 510 mm, and one end has a thickness of 100 μm and 4 mm × 100 mm.
The nickel lead material of No. 2 was bent into two and fixed by using a pressurizer having an uneven surface to obtain a negative electrode.

After using a polypropylene microporous film as the positive electrode, the negative electrode, and the separator, the positive electrode / separator / negative electrode / separator were laminated in this order, and after being wound many times so as to enter a cylindrical battery can having a diameter of 18 mm. The wound body was fixed to the outer circumference using a tape.

As shown in FIG. 1, the wound body is inserted into a battery can 5 having a diameter of 18 mm by inserting an insulating plate 4 into the upper and lower parts, the negative electrode lead 12 is welded and fixed to the battery can 5, and the positive electrode lead 13 is connected to a safety valve. Welded to device 8.

Here, as the electrolytic solution, an electrolytic solution prepared by dissolving LiPF6 in a mixed solution of propylene carbonate and diethyl carbonate is poured, and then a PTC element (positive temperature coefficient element)
9 and the battery lid 7 are placed, caulked, and sealed to have a diameter of 18 mm,
The battery was 65 mm in height. The assembled battery weighed 36.8 g.

Example 2 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum into a film having a thickness of 1000 angstroms on both surfaces of a polyethylene terephthalate (PET) film having a thickness of 14 μm for a positive electrode by a vacuum deposition method.

Polyethylene terephthalate (P
ET) Nickel was formed on both surfaces of a film having a thickness of 14 μm by a vacuum deposition method to a thickness of 1000 Å,
A conductive sheet was produced.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 36.8 g.

Example 3 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum into a film having a thickness of 2000 angstroms on both surfaces of a polyethylene terephthalate (PET) film having a thickness of 18 μm for a positive electrode by a vacuum deposition method.

Polyethylene terephthalate (P
ET) Nickel was formed on both sides of a film having a thickness of 2000 μm to a thickness of 2000 μm by a vacuum deposition method on a film having a thickness of 20 μm.
A conductive sheet was produced.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 36.8 g.

Example 4 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum in a thickness of 500 angstroms on both surfaces of a polyethylene naphthalate (PEN) film having a thickness of 14 μm for a positive electrode by a vacuum deposition method. .

Polyethylene naphthalate (P
EN) Copper is deposited on a 14 μm thick film by vacuum deposition.
A conductive sheet having a thickness of 00 angstrom and formed on both sides was prepared.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 36.8 g.

Example 5 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum on a double-sided film of polyethylene terephthalate (PET) with a thickness of 20 μm for a positive electrode by vacuum vapor deposition to a thickness of 1000 Å.

For the negative electrode, a polyethylene terephthalate (PET) film having a thickness of 14 μm was formed on both sides of nickel to a thickness of 500 Å by vacuum deposition to prepare a conductive sheet.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral battery was assembled in the same manner as in Example 1. The assembled battery weighed 37.0 g.

Example 6 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum into a film having a thickness of 1000 angstroms on both surfaces of a polybutylene terephthalate T (PBT) film having a thickness of 15 μm for a positive electrode by a vacuum deposition method. It was made.

Polybutylene terephthalate (P
BT) Nickel was formed on both sides of a film having a thickness of 15 μm by a vacuum deposition method to a thickness of 1000 Å,
A conductive sheet was produced.

A positive electrode and a negative electrode were manufactured in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 36.8 g.

Example 7 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum on a surface of polyethylene terephthalate (PET) having a thickness of 14 μm for a positive electrode by vacuum vapor deposition to have a thickness of 2000 angstroms on both sides.

Polyethylene terephthalate (P
ET) 50 μm copper on a 14 μm thick film by vacuum deposition
A conductive sheet was formed by molding both surfaces to a thickness of 0 angstrom and then molding copper to a thickness of 1 μm on both surfaces by an electroless plating method.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 37.3 g.

Example 8 As a resin sheet-like conductive film, a conductive sheet was prepared by forming aluminum into a film having a thickness of 5000 angstroms on both surfaces of a polyethylene terephthalate (PET) film having a thickness of 14 μm for a positive electrode by a vacuum deposition method.

Polyethylene terephthalate (P
ET) 50 μm copper on a 14 μm thick film by vacuum deposition
A 0 angstrom-molded and electroless plating method was applied to both sides to form a conductive sheet having a thickness of 2 μm.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 37.9 g.

Example 9 As a resin sheet conductive film, polyethylene terephthalate (PET) film for a positive electrode was formed into a film having a thickness of 10 μm, 500 angstrom of aluminum was formed by a vacuum deposition method, and aluminum was formed on both sides by an electrolytic plating method to a thickness of 1 μm. Then, a conductive sheet was prepared.

Polyethylene terephthalate (P
ET) Nickel was formed on both sides of a film having a thickness of 2000 μm by a vacuum deposition method on a film having a thickness of 14 μm.
A conductive sheet was produced.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral battery was assembled in the same manner as in Example 1. The assembled battery weighed 37.0 g.

Example 10 As a resin sheet-like conductive film, polyethylene terephthalate (PET) film for a positive electrode was formed into a film having a thickness of 14 μm, 500 angstrom of aluminum was formed by a vacuum deposition method, and aluminum was formed to a thickness of 2 μm by electrolytic plating on both surfaces. A molded conductive sheet was produced.

Polyethylene terephthalate (P
ET) 50 μm copper on a 14 μm thick film by vacuum deposition
Molded to 0 angstrom and made copper less than 0.1 by electroless plating.
A conductive sheet having a thickness of 5 μm and formed on both sides was produced.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 37.2 g.

Example 11 Polyethylene terephthalate (P
ET) 14 μm thick aluminum by vacuum evaporation method 10
An electrode was produced using a current collector molded on both sides of 00 angstrom, and an electrode was produced using a current collector of 10 μm copper foil for the negative electrode.

A positive electrode and a negative electrode were manufactured in the same manner as in Example 1 using the above conductive sheet, and a spiral wound battery was prepared in Example 1.
Assembled as. The assembled battery weighs 3
It was 9.2 g

Comparative Example 1 An electrode was prepared using a 20 μm thick aluminum current collector for the positive electrode and a 10 μm thick copper foil current collector for the negative electrode.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 40.0 g

Comparative Example 2 An electrode was prepared by using a nickel foil 20 μm thick current collector for a positive electrode as a current collector, and a nickel foil 10 μm for a negative electrode.
An electrode was produced using the current collector of.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 41.9 g.

Comparative Example 3 An electrode was prepared by using an aluminum foil having a thickness of 20 μm for the positive electrode as a current collector and a stainless 304 foil having a thickness of 10 μm for the negative electrode.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and a spiral wound battery was assembled in the same manner as in Example 1. The assembled battery weighed 39.2 g.

Comparative Example 4 As a resin sheet-like conductive film, a conductive sheet was prepared by forming a film of polyethylene terephthalate (PET) having a thickness of 14 μm for a positive electrode on the both surfaces of which aluminum was formed to a thickness of 500 angstrom by the vacuum deposition method.

Polyethylene terephthalate (P
ET) 20 μm copper on a 14 μm thick film by vacuum deposition
A conductive sheet having a thickness of 0 angstrom and formed on both sides was produced.

A positive electrode and a negative electrode were prepared in the same manner as in Example 1 using the above conductive sheet, and a spiral wound battery was prepared in Example 1.
Assembled as. The assembled battery weighs 3
It was 6.7 g

The above Examples 1 to 11 and Comparative Examples 1 to 1
Table 1 summarizes the material and thickness of the positive electrode current collecting layer, the material and thickness of the negative electrode current collecting layer, and the battery weight for No. 4.

[0069]

[Table 1]

Next, using the batteries of Examples 1 to 11 and Comparative Examples 1 to 4 shown in Table 1, 3.5 hours was charged at a charging current of 0.5 A and an upper limit voltage of 4.20 V, and then 6Ω. A cycle of discharging up to 2.5 V was performed using the resistance element of. With respect to the batteries of Examples 1 to 11 and Comparative Examples 1 to 4, the internal resistance value, the 5th cycle discharge capacity, the 10th cycle discharge capacity, the weight energy density, the 100th cycle discharge capacity, and the 2A load discharge capacity were measured. Result is,
It is as shown in Table 2.

[0071]

[Table 2]

As described above, the charging / discharging cycle performances are almost the same, and the charging / discharging can be practically used. On the other hand, the fact that the weight of the battery can be reduced does not use a metallic current collector. Therefore, it has an advantageous effect and is very effective when the battery is applied in a portable manner. The above results also show that the weight energy density is improved, the effect is great even when the battery is newly enlarged, and it is effective when the battery is lightweight and has a large output.

Further, by using the resin sheet for the sheet-like film of the current collector, the impact at the time of dropping is dispersed to both the separator and the current collecting sheet. Since the resin sheet has elasticity. Unlike a metal body, it does not concentrate in one place and deforms the surroundings, so excessive stress concentration does not occur.

Since it is a resin, it does not undergo linear breakage, which is seen in metal, against some force, and the sheet itself breaks as it stretches. Therefore, simultaneous breakage of the entire current collector occurs. It does not do so, but takes the form of gradually destroying.

From the above, according to the present example, it is possible to reduce the weight of the battery by using the thin film body of the resin sheet having the conductive metal on the surface as the current collector of the electrode. The use of a conductive sheet within the scope of the present invention is extremely effective in that it has the same thickness as the conventionally used metal foil due to the layer thickness.

Regarding the thickness of the resin sheet used as the conductive current collector sheet, in order to practically apply the positive and negative mix, it is necessary to have the strength of the sheet to a certain extent or more. In order to withstand the above, a breaking strength of 3 kgf / cm or more is required. In particular, it is desirable to use a sheet of 4 kgf / cm in order to maintain the uniformity of the coating film.

The thickness of the conductive thin film is preferably 5 μm or more in order to prevent the production of the conductive thin film from becoming difficult. Further, it is preferably 20 μm or less from the viewpoint of film strength, electrode moldability, and battery weight.

It is desirable that the conductive film is thinner in order to reduce the weight of the battery, and it is preferable that the conductive film is in the range of 0.05 to 2 μm on one side (see FIG. 2). Further, in order to ensure electrical continuity with the active material, the thickness of the conductive film is preferably about 0.02 μm or more.

The present invention is not necessarily limited to the above embodiment. That is, as the resin sheet film, polyester such as PET, PBT, or PEN, as well as other polyester, polyether ether ketone, polyimide, polypropylene, or the like can be used.

As the conductive metal for the surface layer of the sheet-shaped film, when used as a positive electrode, nickel platinum, titanium, zinc or the like can be used in addition to aluminum or nickel. When used as the negative electrode, in addition to copper, nickel, or SUS, palladium, silver, titanium, or the like can be used.

As the method for forming the surface conductive film, a vacuum deposition method or an electroless plating method, a pressure bonding method for electrolytically plated foil (2 μm or less), a metal sprayed thin film forming method, or the like can be used. .

The method of manufacturing the electrode can also be realized by methods other than the method described in this embodiment. Above all,
Various active materials can be used for the electrodes, and any non-aqueous electrolyte battery can be applied.

For example, as the positive electrode active material, LiCoO ₂
In addition to LiNiO ₂ , LiCo _x Ni _1-x O ₂ , Li
Mn ₂ O ₄ , LiMnO ₂ , LiFeO ₂ , MoO ₂ ,
MoO ₃ , MoS ₂ , TiS ₂ , LiTiO ₂ , V ₂ O
Various materials such as ₅ , V ₃ O ₆ , Li _x VO _y , and MnO ₂ can be used. In addition to carbon materials close to glassy carbon as the negative electrode active material, lithium alloys and lithium alloys and lithium are doped / Other dedopable carbon and lithium metal compounds can be used.

The shape of the battery is not limited to the cylindrical shape, but may be a flat plate shape, a rectangular parallelepiped shape, or the like.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0086]

As described above, according to the conventional method, it is difficult to obtain a battery which has a large energy density, is lightweight and can be applied to a large battery, and it is difficult to achieve performance / weight reduction for various batteries. By using the method of the present invention,
Batteries with higher performance can be manufactured.

The current collector of the present invention, that is, a battery in which a positive electrode or a negative electrode active material mixture electrode is applied to a conductive thin film having a conductive metal on the surface of a resin sheet film as a battery, is light in weight. In particular, compared with a battery using a metal copper foil / net as a current collector, the current collector can be reduced in weight by about 1/4 to 1/6 in comparison with only the current collector portion.

When polyester, polyetheretherketone, or polyimide is used for the resin sheet, the binding force with the binder can be expected to increase, and the effect of preventing the active material from peeling or falling off from the conductive portion can be expected together.

Polyvinylidene fluoride, polytetrafluoroethylene, etc., as well as polyester resin, polyethylene, etc. can be used as the binder of the active material, which facilitates the production of electrodes and is effective in reducing the cost.

Furthermore, shock absorption at the conductive film portion can be expected, and shock of vibration can be alleviated.

When the battery is abnormally heated, or when the electrode current collecting mechanism or the current collecting mechanism is a resin sheet-shaped film when the battery is locally heated, melting can occur and the conductivity can be expected to stop.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a diagram showing a relationship between a conductive film thickness and a weight energy density.

[Explanation of symbols]

 1 Negative electrode 2 Positive electrode 3 Separator 4 Insulating plate 5 Battery can 6 Sealing gasket 7 Battery lid 8 Safety valve device 9 PTC element 10 Negative electrode current collector 11 Positive electrode current collector 12 Negative electrode lead 13 Positive electrode lead 14 Center pin

Claims (5)

[Claims] 1. A positive electrode having Li _x MO ₂ (M = Ni, Co,
Fe or Mn), and the negative electrode is doped with lithium metal or a lithium alloy, or lithium.
In a non-aqueous electrolyte secondary battery using a carbon material that can be dedoped, use a conductive thin film having a conductive metal on the resin sheet film as the current collector for the positive electrode and / or the negative electrode. The non-aqueous electrolyte secondary battery characterized in that 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the resin sheet film is made of polyester, polyetheretherketone, polyimide, or polyolefin. 3. The resin sheet film has a thickness of 5 to 20.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is in the range of μm. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the conductive metal is copper, nickel, or aluminum. 5. The conductive metal has a thickness of 0.05 to 2
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is in the range of μm.