JPH1126025A - Cylindrical nonaqueous battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery having superior charging/discharging characteristics after being left standing as it is at a high temperature by providing a polymer layer, swelled or wetted by an electrolytic solution between a positive electrode and a negative electrode and forming the polymer layer with a porous lithium ion conductive polymer. SOLUTION: A porous PVdF film is provided between a positive electrode and a negative electrode, and they are wound and inserted into a cylindrical stainless steel case to assemble a cylindrical battery. An electrolytic solution mixed with ethylene carbonate EC and diethyl carbonate DEC and dissolved with LiPF6 is added into the battery by vacuum injection, and the porous PVdF film is swelled by the electrolyte to form a polymer layer swelled or wetted by the electrolytic solution. An electric charging discharging can be conducted after the battery is left standing as it is at a high temperature. Passages for ions to be quickly diffused are secured by the electrolytic solution in the fine holes of a porous polymer electrolyte, and the high-rate electric charging/ discharging becomes satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylindrical non-aqueous battery.

[0002]

2. Description of the Related Art A cylindrical nonaqueous battery is manufactured by combining a positive electrode and a negative electrode prepared in advance with a separator interposed therebetween, and then winding the resultant rigidly. Therefore, since the interval between the positive electrode and the negative electrode is kept uniform, the current distribution becomes uniform,
Excellent discharge characteristics at high rate and low temperature. However,
Since the electrode group is wound stiffly, it is not possible to supply the electrolyte sufficiently to the inside of the hole of the separator or the hole of the electrode active material layer even if the electrolyte is injected after assembly. Therefore, when the battery was left at a high temperature, the electrolyte between the positive electrode and the negative electrode was depleted, and the subsequent discharge capacity was significantly reduced.

[0003]

The cylindrical non-aqueous battery has a problem that when left at a high temperature, the electrolyte between the positive electrode and the negative electrode is depleted, and the subsequent discharge capacity is greatly reduced. The present invention has been made in view of the above problems, and by providing a polymer layer that swells or wets with an electrolytic solution between a positive electrode and a negative electrode, excellent charge / discharge characteristics even after being left at a high temperature. And a cylindrical non-aqueous battery.

[0004]

The cylindrical nonaqueous battery according to the present invention is characterized in that a polymer layer which swells or wets with an electrolyte is provided between a positive electrode and a negative electrode. Further, the polymer layer has a porous lithium ion conductive polymer, and the porosity of the polymer layer swelled or wetted by the electrolytic solution having the porous lithium ion conductive polymer is 10% to 80%.
%, The polymer layer contains polyvinylidene fluoride, polyvinyl chloride, or polyacrylonitrile or a copolymer containing these as a main component. The polymer layer swells or swells in the pores of the active material layer of the positive electrode and / or the negative electrode by the electrolytic solution. It is characterized by comprising a wetting polymer.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional cylindrical non-aqueous battery, a porous polymer membrane such as polypropylene or polyethylene is used as a separator, and an electrolyte is held in the pores. In this case, the separator is an insulator in ion conduction, and has no ability to hold the electrolytic solution. In the battery according to the present invention, by having a polymer layer that swells or wets with the electrolyte between the positive electrode and the negative electrode, the electrolyte is retained in the polymer layer even after being left at a high temperature. Charging / discharging becomes possible as compared with a cylindrical nonaqueous battery. Furthermore, in the battery according to the present invention, when the polymer layer is a porous lithium ion conductive polymer, the electrolyte in the pores secures a path through which ions are rapidly diffused. The charge / discharge at a higher rate is better than that of the cylindrical nonaqueous battery.

Further, by providing a polymer layer which swells or wets with an electrolytic solution in pores of an active material layer of a positive electrode and / or a negative electrode, an interface between an electrode and an electrolyte is formed by a porous lithium ion conductive polymer. When covered with a high-voltage battery, oxidation and reduction of the organic electrolyte by the positive electrode and the negative electrode, which are problematic for a high-voltage battery, can be reduced, and the charge storage characteristics can be improved and the battery safety can be improved. improves. Also in this case, charge / discharge at a high rate becomes possible because the lithium ion conductive polymer is porous. Further, when a porous polymer is present in the pores of the active material layer, the amount of the electrolyte contained in the pores of the active material layer can be significantly reduced, so that the safety is also improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments.

(Example 1) Lithium cobaltate (LiC)
A mixture of 70 wt% of oO ₂ ), 6 wt% of acetylene black, 9 wt% of polyvinylidene fluoride (PVdF), and 15 wt% of n-methyl-2-pyrrolidone (NMP) is applied on an aluminum foil having a thickness of 20 μm.
Dry at <RTIgt; C </ RTI> to evaporate the NMP. After the above operation was performed on both surfaces of the aluminum foil, it was pressed to obtain a positive electrode plate. The thickness of the positive electrode plate after pressing was 170 μm.

Next, graphite 81% by weight, PVd
A mixture of 9 wt% of F9 and 15 wt% of NMP is coated on a 14 μm-thick copper foil, dried at 150 ° C., and dried.
Was evaporated. After performing the above operation on both surfaces of the copper foil, it was pressed to obtain a negative electrode plate. The thickness of the negative electrode after pressing was 190 μm.

Further, a microporous PVdF film was produced as a polymer layer which swells or wets with an electrolytic solution as follows. 12 g of PVdF powder having an average molecular weight of 60,000
Dissolved in 8 g of NMP. The NMP was washed away by immersing this solution in water and the porosity was 10%, 20%,
30%, 40%, 50%, 60%, 70% and 80%
Of a microporous PVdF membrane having a thickness of 25 μm.

A microporous PVdF film is wound between the positive electrode plate and the negative electrode plate prepared as described above,
The cylindrical battery was assembled by inserting it into a cylindrical stainless case having a diameter of 6.5 mm and a diameter of 6.5 mm. Inside this battery,
Ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 1 and 1 mol / l
3.0 g of an electrolytic solution in which LiPF ₆ was dissolved was added by vacuum injection, and the microporous PVdF membrane was swelled with the electrolytic solution to form a polymer layer which swelled or wetted with the electrolytic solution. Thus, the nominal capacity of 1400 mAh
A battery (A) of Example 1 according to the present invention was manufactured.

Example 2 In Example 2, 12 g of PVdF powder having an average molecular weight of 60,000 was replaced by a polymer layer which swells or wets with an electrolyte instead of a microporous PVdF membrane.
Is dissolved in 88 g of NMP, and this solution is porosity 40%,
After being applied to a polypropylene film having a thickness of 25 μm, the NMP was washed away by immersion in water to give a total thickness of 35 μm.
porosity of 10%, 20%, 30%, 4%
0%, 50%, 60%, 70% and 80% microporous P
Except that the VdF film was formed on a polypropylene film, a nominal capacity of 1400 mAh
A battery (B) of Example 1 according to the present invention was manufactured.

Comparative Example 1 As Comparative Example 1, microporous PV
A conventionally known battery (a) having a nominal capacity of 1400 mAh and having the same configuration as that of Example 1 except that a polypropylene film having a thickness of 25 μm and a different porosity was used instead of the dF film was manufactured. .

These batteries (A), (B) and (a)
The battery was charged to 4.1 V at a current of 1 CA at 25 ° C., then charged at a constant voltage of 4.1 V for 3 hours, and left at 60 ° C. for 30 days in the charged state. After standing, the battery was discharged at 2.degree. C. to 2.75 V with a current of 1 CA.

FIG. 1 is a diagram showing the relationship between the discharge capacity after leaving these batteries at 60 ° C. for 30 days and the porosity of the polymer electrolyte layer or separator of the used lithium ion battery. From the figure, it can be seen that the batteries (A) and (B) according to the present invention show that a conventionally known battery using a polypropylene membrane has a porosity of 10% to 80% even after being left at a high temperature. It is understood that the discharge capacity is superior to that of (a).

FIG. 2 shows a battery (A) of Example 1 having a porosity of 40%, a battery (B) of Example 2 having a porosity of 40%, and a comparative example 1 having a porosity of 40%. This is a comparison of the discharge characteristics after standing when the same experiment as in FIG. 1 was performed using the battery (a). By the figure,
It is understood that the batteries (A) and (B) according to the present invention show superior discharge characteristics after being left as compared with the conventionally known battery (a).

Example 3 LiCoO as a positive electrode active material
_A positive electrode plate was manufactured in the same manner as in Example 1 except that lithium nickelate (LiNiO ₂ ) was used instead of ₂ . The negative electrode plate was manufactured in the same manner as in Example 1.

Next, a polymer layer which swells or wets with the electrolytic solution was produced as follows. First, an average molecular weight of 6
12 g of 000 PVdF powder was dissolved in 88 g of NMP. The solution is applied to the holes of the active material layer by applying the solution on the above-prepared positive electrode plate and negative electrode plate prepared in advance under reduced pressure under vacuum, and the NMP is washed away by immersion in water. The pores of the active material layer were filled with a microporous PVdF layer having a porosity of 40%.

The porosity between the positive electrode plate and the negative electrode plate coated with the microporous PVdF layer prepared as described above is 40%.
And wound with a conventionally known polyethylene separator having a thickness of 25 μm and a length of 180 mm and a diameter of 6.
It was inserted into a 5 mm cylindrical stainless steel case to assemble a cylindrical battery. Inside the battery, EC and DEC were mixed at a volume ratio of 1: 1 and 1 mol / l of LiPF ₆ was mixed.
Was added by vacuum injection of 3.0 g of an electrolytic solution in which
Example 2 according to the invention in which the microporous PVdF layer in the electrode holes was swollen by the electrolyte and had a nominal capacity of 1400 mAh.
Battery (D) was manufactured.

Comparative Example 2 As Comparative Example 2, a conventionally known battery having a nominal capacity of 1400 mAh has the same configuration as that of Example 3 except that a microporous PVdF layer is not formed in the hole of the electrode. (B) was manufactured.

Using these batteries (D) and (b), the battery was charged to 4.1 V at a current of 1 CA at 25 ° C., and then charged at a constant voltage of 4.1 V for 3 hours. It was left at 60 ° C. for 30 days. 25 ℃ after standing
Was discharged to 2.75 V at a current of 1 CA. FIG.
Fig. 9 compares the discharge characteristics when the above experiment was performed using the battery (D) of Example 3 and the battery (b) of Comparative Example 2 having a porosity of 40%. By the figure,
The battery (D) according to the present invention comprises a conventionally known battery (b)
It is understood that the battery exhibits excellent discharge characteristics after being left as compared with the case of FIG.

The battery (D) of Example 3 according to the present invention
Using the battery (b) of Comparative Example 2 and a conventionally known battery, the following safety comparison test was performed. The difference between these batteries is that in the battery (D), the pores of the positive and negative electrode active material layers are filled with the microporous polymer, whereas in the battery (b), the pores of the active material layer are filled. Is not filled with the microporous polymer, and only the active material layer contains a large amount of the organic electrolyte. The batteries (D) and (b) were charged at room temperature to 4.1 V with a current of 1 CA, and subsequently charged at a constant voltage of 4.1 V for 2 hours, and then a nail having a diameter of 3 mm was inserted into the batteries. Penetrated. As a result, in the battery (D) according to the present invention, the safety valve was only activated and no smoke was generated, whereas in the conventionally known battery (b), the safety valve was activated and smoke was generated.

From these results, it can be said that the battery (D) according to the present invention is a battery excellent in both low-temperature discharge characteristics and safety.

In the above embodiment, as a method for producing a microporous polymer membrane, NMP is removed by immersing a solution of a polymer in NMP in water, but the solvent for dissolving the polymer is limited to NMP. What is necessary is just what melt | dissolves a polymer instead of what is performed. Further, the liquid in which the solution in which the polymer is dissolved is immersed is not limited to water, and any liquid that does not dissolve the polymer and is compatible with the solvent in which the polymer is dissolved may be used. When the solvent is removed from the polymer solution using such a combination of the polymer, the solvent for dissolving the polymer, and the liquid for immersing the solution in which the polymer is dissolved, the portion where the removed solvent was present is reduced. The microporous polymer film can be manufactured as a hole.

As a method for producing a porous polymer for producing a porous polymer electrolyte, in addition to the above-mentioned method (wet method), a drawing method, a method for removing fine particles from a polymer to which fine particles are added, a high-temperature method, We tried a method of solidifying the polymer by cooling the polymer solution to remove the liquid, and a method of physically drilling through holes using a stainless fine needle after fabricating a nonporous polymer film. Among these, batteries manufactured by a method using fine needles of stainless steel exhibited excellent charge / discharge characteristics as in the case of using a wet method, but sufficient porosity was not obtained by other methods. Was.

The polymer used for the porous polymer electrolyte may be polyvinyl chloride (PVD) in addition to the above-mentioned PVdF.
C), using polyacrylonitrile (PAN), polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene imine, polybutadiene, polystyrene and polyisoprene. Attempts were made to produce porous polymer electrolytes and batteries using them, but PVDF, PVC and PAN
Was especially excellent.

In the above embodiment, polyvinylidene fluoride is used as the polymer which swells or wets with the electrolytic solution. However, the present invention is not limited to this, and polyethers such as polyvinyl chloride, polyethylene oxide and polypropylene oxide are used. , Polyacrylonitrile, polyvinylidene fluoride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethylene imine, polybutadiene, polystyrene, polyisoprene, or derivatives thereof. May be used alone or as a mixture. Further, a polymer obtained by copolymerizing various monomers constituting the polymer may be used.

In the above embodiment, a mixed solution of EC and DEC is used as the electrolytic solution to be contained in the polymer. However, the present invention is not limited to this, and ethylene carbonate, propylene carbonate, dimethyl Carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide,
A polar solvent such as 1,2 dimethoxyethane, 1,2 diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

Further, in the above embodiment, the electrolyte
LiPF as lithium salt to be contained₆Using
But, in addition, LiBF_Four, LiAsF₆, LiClO
_Four, LiSCN, LiI, LiCF_ThreeSO_Three, LiC
1, LiBr, LiCF_ThreeCO _Two, Li (CF_ThreeS
O_Two)_TwoLithium salt such as N, or a mixture thereof
May be used.

Further, in the above embodiment, LiCoO ₂ was used as the positive electrode active material, but the present invention is not limited to this. Besides this, as the inorganic compound, composition formula LixMO ₂ or LiyM ₂ O _4, (although, M is a transition metal, 0 ≦ x ≦ 1,0 ≦ y ≦ 2) represented by the composite oxide, the tunnel An oxide having a vacancy and a metal chalcogenide having a layered structure can be used. Specific examples thereof include LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O
₄ , Li ₂ Mn ₂ O ₄ , MnO ₂ , FeO ₂ , V
Examples include ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , and TiS ₂ . Examples of the organic compound include a conductive polymer such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, in the above embodiment, graphite is used as the negative electrode active material.
alloys of lithium with l, Si, Pb, Sn, Zn, Cd, etc., transition metal composite oxides such as LiFe ₂ O ₃ , WO ₂ ,
A transition metal oxide such as MoO _{2, a} carbonaceous material such as graphite and carbon, a lithium nitride such as Li ₅ (Li ₃ N), a metal lithium foil, or a mixture thereof may be used.

In the present invention, a part or the whole of the interface between the positive electrode and the negative electrode and the electrolyte is covered with a porous lithium ion conductive polymer, so that the organic material formed by the positive electrode and the negative electrode, which is a problem for a high-voltage battery, is formed. The oxidation and reduction of the electrolyte could be reduced, and the charge storage characteristics could be improved. Also in this case, charge / discharge at a high rate became possible because the lithium ion conductive polymer was porous.

[0033]

As described above, in the battery according to the present invention, since the polymer layer which swells or wets with the electrolytic solution is provided between the positive electrode and the negative electrode, the electrolytic solution remains in the polymer even after being left at a high temperature. And charge / discharge becomes possible even after being left at a high temperature as compared with a conventional cylindrical nonaqueous battery. Also, in the battery according to the present invention, the electrolyte in the pores of the porous polymer electrolyte secures a passage through which ions diffuse rapidly, so that the battery has a higher efficiency than the conventional cylindrical nonaqueous battery. Good charge / discharge is achieved.

Further, when an interface between the electrode and the electrolyte is covered with a porous lithium ion conductive polymer by providing a polymer layer which swells or wets with the electrolyte in the pores of the active material layer of the positive electrode or the negative electrode. In this method, the oxidation and reduction of the organic electrolyte by the positive electrode and the negative electrode, which are problems due to the high voltage battery, can be reduced, and the charge storage characteristics can be improved, and the safety of the battery can be improved. Also in this case, charge / discharge at a high rate becomes possible because the lithium ion conductive polymer is porous. Further, when a porous polymer is present in the pores of the active material layer, the amount of the electrolyte contained in the pores of the active material layer can be significantly reduced, so that the safety is also improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing discharge characteristics of batteries (A) and (B) according to the present invention and battery (a) of Comparative Example 2 after being left.

FIG. 2 is a diagram showing a discharge curve of the batteries (A) and (B) according to the present invention and the battery (a) of Comparative Example 2 after being left.

FIG. 3 is a diagram showing a discharge curve of the battery (D) according to the present invention and the battery (b) of Comparative Example 2 after being left.

Claims (5)

[Claims] 1. A cylindrical non-aqueous battery comprising a polymer layer which swells or wets with an electrolytic solution between a positive electrode and a negative electrode. 2. The cylindrical non-aqueous battery according to claim 1, wherein the polymer layer which swells or wets with the electrolytic solution has a porous lithium ion conductive polymer. 3. The cylindrical non-aqueous battery according to claim 1, wherein the porosity of the polymer layer swelled or wetted by the electrolyte containing the porous lithium ion conductive polymer is 10% to 80%. 4. The polymer layer swelled or wetted by the electrolyte contains polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile or a copolymer containing these as a main component. Cylindrical non-aqueous battery. 5. The cylindrical non-aqueous solution according to claim 1, wherein a polymer which swells or wets with an electrolytic solution is provided in pores of the active material layer of the positive electrode and / or the negative electrode. battery.