JP2001283911A - Polymer battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer battery in which discharge capacity is superior and cycle characteristics is superior. SOLUTION: The polymer battery 1 has a structure, in which an electrode body unit which is comprised of a positive electrode plate 20 and a negative electrode plate 30 having been piled via a polyolefin group porous membrane 40, is housed in an outer package 10 molded into an envelope shape by pasting a sheet body. The porous membrane 40 contains a polymer electrolyte. This polymer electrolyte is a gel polymer electrolyte, in which nonaqueous electrolyte is held in a polymer structure, which is made by setting a polymer precursor containing vinylenecarbonate derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polymer battery, and more particularly, to a polymer battery in which a positive electrode and a negative electrode are arranged via a polymer electrolyte.

[0002]

2. Description of the Related Art In recent years, demands for portable devices such as portable telephones, AV equipment, digital cameras, personal digital assistants (PDAs), etc. have been rapidly increasing, and demands for thin, lightweight, high-capacity batteries have rapidly increased. On the other hand, a polymer battery is extremely thin and can be made lightweight, so that it is also suitable for being mounted on a portable device, and is expected to meet such a demand.

[0003] A polymer battery has a structure in which a membrane made of a polymer electrolyte is interposed between a positive electrode plate and a negative electrode plate.
It has the feature that the electrolyte does not leak unlike the solution type battery.

As a positive electrode material of a polymer battery, a lithium-containing composite oxide is frequently used. In addition, although lithium metal and aluminum / lithium alloys have been used as the negative electrode material, carbon materials capable of occluding and releasing lithium ions have been frequently used in recent years because dendrites easily grow with charge and discharge. .

[0005] A polymer electrolyte is one in which an electrolyte is dissolved in a polymer, and a solid electrolyte using an alkylene oxide or the like for the polymer has been conventionally known.
Since this solid electrolyte has low ionic conductivity, it is difficult to obtain a high rate discharge capacity.

On the other hand, a polymer battery in which a polymer electrolyte is formed in a gel state using a polyalkylene glycol diacrylate or the like as a polymer precursor has been developed. Since the gel polymer electrolyte has higher ionic conductivity than the solid electrolyte, the polymer battery using this is
A relatively high high rate discharge capacity can be obtained.

Further, in a polymer battery of a type using a gel polymer electrolyte, mechanical strength is improved by interposing a gel polymer electrolyte held on a polyolefin-based porous membrane between a positive electrode and a negative electrode. Polymer batteries have also been developed.

[0008]

However, in such a polymer battery using a gel polymer electrolyte, the battery capacity is reduced during repeated charging and discharging, so that a sufficient battery life cannot be obtained. There's a problem.

The present invention has been made in view of the above problems, and has as its object to provide a polymer battery having excellent discharge capacity and excellent cycle characteristics.

[0010]

In order to achieve the above object, the present invention provides a polymer battery in which a positive electrode and a negative electrode are disposed via a gel-like polymer electrolyte. A polymer electrolyte was formed by curing a pregel solution comprising a polymer precursor containing the derivative (hereinafter referred to as "vinylene carbonates") and an electrolyte.

A polymer battery using a gel polymer electrolyte has a relatively large discharge capacity.

[0012] Conventionally, as a gel-like polymer electrolyte, one obtained by curing a pre-gel solution in which a polymer precursor such as polyalkylene glycol diacrylate or polyalkylene glycol dimethacrylate and an electrolytic solution are mixed is generally used. However, in this case, as described above, the battery capacity tends to decrease as charging and discharging are repeated. This is probably because the portion of the polymer electrolyte present on the surface of the negative electrode is unstable with respect to charge and discharge, and is decomposed with repeated charge and discharge.

On the other hand, when vinylene carbonate is contained in the polymer precursor as in the present invention, the polymer electrolyte formed by curing the pregel solution is stable even on the surface of the negative electrode. In addition, the battery has excellent cycle characteristics.

In order to exhibit such effects, the content of vinylene carbonate relative to the polymer precursor is set to 0.1.
It is preferable that the content be 5 wt% or more. If the content is too large, a decomposition reaction occurs on the positive electrode during charge and discharge, and CO ₂ is generated. Therefore, the content is preferably set to 10 wt% or less.

Specifically, based on polyalkylene glycol diacrylate or polyalkylene glycol dimethacrylate conventionally used as a polymer precursor, vinylene carbonates are mixed with the polymer precursor to form the polymer precursor. It has been confirmed that a good effect can be obtained if it is formed.

Incidentally, in a polymer battery using an exterior body such as an aluminum laminate film to which a sheet body is attached, the exterior body is likely to swell when the pressure inside the battery increases. Therefore, in such a type of polymer battery, the practical value of improving the cycle characteristics is particularly large.

[0017]

FIG. 1 is an external perspective view of a thin polymer battery according to the present embodiment, and FIG. 2 is a sectional view taken along line AA 'in FIG.

The polymer battery 1 has a positive electrode plate 2 inside an outer package 10 formed by attaching sheets to form an envelope.
0 and the negative electrode plate 30 are made of a polyolefin-based porous film 40.
In this structure, a rectangular electrode body unit, which is superimposed via a through hole, is housed, and the porous membrane 40 is impregnated with a gel polymer electrolyte. In this electrode unit, a positive electrode current collector plate 21 and a negative electrode plate 3
A negative electrode current collector 31 is provided on the surface on the 0 side, and the lead terminals 21 a of the positive electrode current collector 21 and the lead terminals 31 a of the negative electrode current collector 31 project outside from the upper edge 11 of the exterior body 10. External terminals are formed.

The package 10 is formed by molding a sheet made of an aluminum laminated film (a film in which an aluminum foil is covered with a PP layer or a PE layer) into an envelope. This aluminum laminate film has the features of being lightweight and having high tensile strength.

The positive electrode plate 20 is made of a lithium-containing salt as a positive electrode active material (specific examples: LiCoO ₂ , LiNiO ₂ , LiM
nO _2, LiFeO ₂₎ and carbon powder as a conductive agent (example: graphite powder, and mixing the coke powder) and a binder is obtained by forming a rectangular plate shape.

The negative electrode plate 30 is obtained by mixing graphite powder as a negative electrode active material with a binder and forming the mixture into a rectangular plate shape.

The porous film 40 is made of a polyolefin-based porous film, and the porous film 40 is formed to have a size slightly larger than that of the positive electrode plate 20 or the negative electrode plate 30.
It extends outside the end of the positive electrode plate 20 and the negative electrode plate 30,
The two plates do not touch each other.

A portion of the porous film 40 sandwiched between the positive electrode plate 20 and the negative electrode plate 30 is filled with a polymer electrolyte so that ion conduction is sufficiently performed between the positive electrode plate 20 and the negative electrode plate 30. I have.

(Structure and Effect of Polymer Electrolyte) This polymer electrolyte is a gel polymer electrolyte in which a non-aqueous electrolyte is dissolved in a polymer obtained by curing a polymer precursor containing vinylene carbonates.

As the solvent of the non-aqueous electrolyte, for example, an organic solvent such as ethylene carbonate or propylene carbonate, or a mixture thereof with dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxy A mixed solvent with a low boiling point solvent such as methoxyethane may be mentioned, and solutes of the non-aqueous electrolyte include LiPF ₆ , LiClO ₄ and LICF ₃ SO ₃ .

The polymer precursor used in the present embodiment is a polyalkylene glycol diacrylate (specific examples: polyethylene glycol diacrylate, polypropylene glycol diacrylate) or polyalkylene glycol dimethacrylate (specific examples) which have been conventionally used. : Polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate), to which vinylene carbonates are added.

The following effects are exhibited by the inclusion of vinylene carbonates in the polymer precursor.

As the polymer electrolyte, when a pregel solution obtained by mixing a polymer precursor such as polyalkylene glycol diacrylate or polyalkylene glycol dimethacrylate and an electrolytic solution without using vinylene carbonates is used, the polymer electrolyte may be charged. As the discharge is repeated, the battery capacity tends to decrease. This is considered to be because the portion of the polymer electrolyte existing on the surface of the negative electrode plate 30 was unstable during charge and discharge.

That is, the polymer skeleton formed by the polymerization of the polymer precursor is decomposed on the surface of the negative electrode plate 30 as charging and discharging are repeated, and the carbon skeleton as the negative electrode active material is decomposed as the decomposition proceeds. This is probably because the material is deactivated and the ionic conductivity itself of the polymer electrolyte is also lost.

On the other hand, when vinylene carbonate is contained in the polymer precursor, when the pregel solution is cured to form a gel-like polymer electrolyte, when the polymer precursor is polymerized, vinylene carbonate is contained. Is incorporated into the polymer backbone. Since the polymer skeleton in which vinylene carbonates are incorporated is hardly decomposed on the negative electrode during charge and discharge, the polymer electrolyte having such a polymer skeleton becomes stable on the surface of the negative electrode plate 30. Therefore, the deactivation of the negative electrode active material during charge and discharge is small, and the cycle characteristics of the battery are excellent.

In order to achieve such an effect, the content of vinylene carbonate relative to the polymer precursor is set to 0.1.
It is preferable to set it to 5 wt% or more.

If the content is too large, a decomposition reaction occurs on the positive electrode plate 20 during charging and discharging, and CO ₂ tends to be generated. Therefore, the content is preferably set to 10 wt% or less.

In a solution-based nonaqueous electrolyte battery,
When vinylene carbonates are added, the added vinylene carbonates tend to decompose on the positive electrode during charge / discharge and generate gas, but in the case of a polymer battery, the added vinylene carbonates are as described above. Since it is incorporated into the polymer skeleton, vinylene carbonates do not decompose on the positive electrode during charge and discharge.

(Regarding Method of Manufacturing Polymer Battery 1) The polymer battery 1 can be manufactured as follows. (1) Production of Electrode Unit The positive current collector 21 and the negative current collector 31 are produced by cutting a conductive metal foil into a predetermined shape.

The positive electrode plate 20 is manufactured by mixing a positive electrode active material, a conductive agent, and a binder and applying the mixture to the surface of a positive electrode current collector plate 21.

The negative electrode plate 30 is manufactured by mixing a negative electrode active material and a binder and applying the mixture to the surface of the negative electrode current collector plate 31.

The porous film 40 is produced by cutting a polyolefin porous film into a predetermined shape.

The electrode unit is manufactured by stacking the positive electrode plate 20, the porous film 40, and the negative electrode plate 30.

(2) Solution Impregnation and Curing A polyalkylene glycol diacrylate or a polyalkylene glycol dimethacrylate as a polymer precursor is prepared by adding a non-aqueous electrolyte and a polymerization initiator to an impregnation solution.

Then, the porous membrane 40 is impregnated with the impregnating solution and heated to polymerize the polymer precursor. As a result, the impregnating solution hardens and becomes a gel-like polymer electrolyte.

(3) Forming of the exterior body After that, the exterior body 10 is formed by molding the sheet made of the aluminum laminated film into an envelope shape while storing it inside. When sealing the upper edge portion 11, the sealing is performed with the lead terminal 21a and the lead terminal 31a sandwiched therebetween.

The impregnation and curing step (2) is
This may be performed before the porous film 40 is overlapped with the positive electrode plate 20 and the negative electrode plate 30 or after the porous film 40 is overlapped with the positive electrode plate 20 and the negative electrode plate 30 to form the electrode unit. Good.

According to the above manufacturing method, the polymer battery 1
Can be produced.

[0044]

EXAMPLES (Examples) Based on the above embodiment, a polymer battery having a battery capacity of 150 mAh was manufactured according to the following specifications.

[0045]

[Table 1]

Table 1 shows the types and contents of vinylene carbonates used in each of the polymer batteries of the examples.

That is, in the polymer battery of the present embodiment, hydrogen (H), methyl group (CH ₃ ), ethyl group (C ₂ H ₅ ), phenyl group (C ₆ H
₅ ) Vinylene carbonates selected from the group consisting of chlorine (Cl), fluorine (F) and bromine (Br) are added.

Aluminum foil was used for the positive electrode current collector plate 21, and copper foil was used for the negative electrode current collector plate 31.

The positive electrode plate 20 is made of LiC as a positive electrode active material.
oO ₂ powder, carbon powder (Ketjen black) as a conductive agent, and PVdF powder as a binder were mixed at a weight ratio of 9
The mixture was mixed at a ratio of 0: 3: 2: 5, the mixture was slurried, applied to the surface of the positive electrode current collector plate 21, and subjected to vacuum heat treatment. The area of the positive electrode plate 20 is 52
cm 2 and its thickness was 80 μm.

The negative electrode plate 30 is prepared by mixing graphite powder as a negative electrode active material and a fluororesin as a binder at a weight ratio of 95: 5, and slurrying the mixture to form a negative electrode current collector plate 3.
1 was applied to the surface and subjected to a vacuum heat treatment. The area of the negative electrode plate 30 was 58 cm ² , and its thickness was 65 μm.

As the porous film 40, a porous film made of polyethylene was used.

Then, the positive electrode plate 20, the porous film 40, and the negative electrode plate 30 were overlapped to produce an electrode unit.

The polymer precursor is polypropylene glycol diacrylate (PPGDA, molecular weight: 1000)
Was used as a base.

As the non-aqueous electrolyte, a solution in which 1 mol / L of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 5: 5 was used. Then, PPGDA and the non-aqueous electrolyte were mixed at a weight ratio of 1:10, and vinylene carbonates described in Table 1 were added thereto as a polymer precursor, and t-hexylpa as a polymerization initiator was further added. The impregnation solution was prepared by adding 5000 ppm of oxidopivalate.

The content of vinylene carbonate relative to the total amount of the polymer precursor is 0.3%, 0.5%
%, 5%, 10%, and 13%.

Then, the aluminum laminate film in which the aluminum foil is coated with PP or PE is folded so as to sandwich the electrode body unit, and three sides (upper edge 11 and both side edges 12) are heat-sealed to form an exterior body. 10
And 3 ml of the above impregnation solution were injected.
When sealing the upper edge portion 11, the lead terminals 2
Sealing was performed with the lead 1a and the lead terminal 31a interposed therebetween.

This was heated at 60 ° C. for 3 hours to cure the impregnating solution, thereby preparing a polymer battery of the example.

Comparative Example 1 Comparative Example 1 was carried out in the same manner as in the above example except that vinylene carbonates were not added.
Was produced.

Comparative Example 2 A non-aqueous electrolytic solution to which vinylene carbonate (as used for battery 1-1 in Table 1) was added as a polymer precursor was used as an impregnation solution without using PPGDA. In the same manner as in the above embodiment,
A polymer battery of Comparative Example 2 was produced.

[Cycle Test] Each of the polymer batteries of the Examples and Comparative Examples was charged and discharged for 500 cycles, and the ratio (%) of the battery capacity after 500 cycles of charging and discharging to the battery capacity before the start of the charging and discharging cycles was measured. .

[High-Temperature Storage Test] Each of the polymer batteries of the example and the comparative example was charged to a charged state (4.2 V), and
Stored at 0 ° C. for 4 days. Then, the swelling amount (m
m) was examined.

[Test Results and Discussion] The results of the above cycle test and high temperature storage test are as shown in Table 1.

Table 1 shows the following.

* Compared with the polymer battery of Comparative Example 1, the polymer battery of the example has a considerably improved capacity retention during cycling. This indicates that the addition of vinylene carbonate to the polymer precursor improves the cycle characteristics.

* In each of the polymer batteries of Examples, the capacity retention during cycling is particularly good when the content of vinylene carbonates is 0.5 wt% or more.

* Compared to the polymer battery of Comparative Example 1, the polymer battery of the example has a larger swelling after charging and storage. However,
When the content of vinylene carbonate is in the range of 10 wt% or less, the swelling after charging and storage is relatively small, while when the content of vinylene carbonate is 13 wt%, the swelling after charging and storage is large.

Accordingly, the content of vinylene carbonates is preferably set to 10% by weight or less.

* In the polymer battery of Comparative Example 2, the capacity retention rate during cycling was low, and the swelling after charge storage was large. This indicates that the effect of improving the cycle characteristics by the addition of vinylene carbonate is peculiar to the polymer battery, and that in a solution-type battery, the internal pressure of the battery tends to increase rather than by the addition of vinylene carbonate.

(Other Matters) In the above embodiment,
Regarding R 1 and R 2 in the above formula 1, only CH ₃ and C ₂ H ₅ are shown as alkyl groups, but C ₃
The same effect can be expected by using H ₇ , C ₄ H ₉ or the like.

R1 and R2 are alkyl derivatives (C
In the case of H ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H _9, etc., in which hydrogen is substituted by a substituent), the effect is the same as that of the alkyl group, although not shown in the examples. Can be expected,
Although the case where R1 and R2 are phenyl derivatives (in which hydrogen of C ₆ H ₅ is substituted with a substituent) is not shown in Examples, the same effect as in the case of phenyl group can be expected.

In the above embodiment, an example in which a carbon material is used as the negative electrode active material has been described. However, the present invention can be similarly applied to a polymer battery using a lithium alloy as the negative electrode active material.

In the above embodiment, an example is shown in which a sheet formed by laminating a sheet such as an aluminum laminate is used as an outer package. However, in a polymer battery using a metal outer can as the outer package, Can be similarly implemented.

In the above-described embodiment, the polymer battery in which only one electrode unit in which the flat positive electrode plate, the porous film, and the negative electrode plate are stacked is housed in the outer package is described. The present invention can be similarly applied to a polymer battery in which a plurality of electrode unit units are bundled and housed in an exterior body, and the same effect can be obtained.

Further, the present invention can be similarly applied to a polymer battery in which a spiral electrode unit formed by winding a long positive electrode plate and a negative electrode plate through a porous film is housed in an outer package. Has the same effect.

Further, in the above-described embodiment, an example in which a porous film containing a gel polymer electrolyte is interposed between a positive electrode and a negative electrode has been described. Although effective in obtaining strength, it is not necessary in the present invention.

As described above, the present invention can be applied to any polymer battery including a power generating element in which the positive electrode and the negative electrode are arranged via the gel polymer electrolyte.

[0077]

As described above, the present invention relates to a polymer battery in which a positive electrode and a negative electrode are disposed via a gel-like polymer electrolyte, and a polymer precursor containing vinylene carbonate represented by the above formula (1). A polymer electrolyte was formed by curing a pregel solution comprising a body and an electrolytic solution, thereby making it possible to realize a polymer battery having excellent discharge capacity and excellent cycle characteristics.

The present invention is particularly effective for a thin polymer battery in which a sheet body such as an aluminum laminated film is bonded to an outer package.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a thin polymer battery according to an embodiment.

FIG. 2 is a sectional view taken along line A-A 'in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polymer battery 10 Outer body 20 Positive electrode plate 30 Negative electrode plate 40 Porous film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ02 AJ03 AJ05 AK03 AL07 AM03 AM04 AM05 AM07 AM16 BJ04 BJ12 CJ02 CJ05 CJ06 DJ02 EJ12 HJ01

Claims (6)

[Claims] 1. A polymer battery comprising a power generating element in which a positive electrode and a negative electrode are arranged via a gel polymer electrolyte, wherein the polymer electrolyte is at least one selected from a compound group represented by the following formula 1. A polymer battery formed by curing a pregel solution comprising a polymer precursor containing one kind of compound and an electrolytic solution. Embedded image In the above formula, R1 and R2 represent any of hydrogen, an alkyl group, an alkyl derivative, a phenyl group, a phenyl derivative and halogen. 2. The polymer battery according to claim 1, wherein the polymer precursor contains at least one of polyalkylene glycol diacrylate and polyalkylene glycol dimethacrylate. 3. The polymer battery according to claim 1, wherein the polymer precursor represented by Chemical Formula 1 is contained in an amount of 0.5 to 10 wt% based on the pregel solution. 4. The polymer battery according to claim 1, wherein the pregel solution has a property of being polymerized and cured by heat. 5. The polymer battery according to claim 1, wherein the power generating element is housed in an exterior body formed by bonding sheet bodies. 6. The polymer battery according to claim 5, wherein the sheet is an aluminum laminated film.