JPH10261437A - Polymer electrolyte and lithium polymer battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the occurrence of lithium dendrite by using the gel electrolyte of a polymer alloy, and to provide a highly reliable battery having enhanced safety. SOLUTION: A polymer alloy film comprises a slightly soluble polymer and a soluble polymer in an organic electrolysis solution. A gelled polymer electrolyte comprises an organic electrolysis solution. In this case, the phase separation size of the alloy film is restricted to less than 100nm. This polymer alloy gel restrains the occurrence of lithium dendrite so that a lithium polymer battery introducing the polymer alloy gel functions as a highly reliable battery having enhanced safety.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte and a lithium polymer battery using the same.

[0002]

_2. Description of the Related Art A lithium ion secondary battery is composed of, for example, an organic electrolyte based on LiCoO _{2 for} a positive electrode, natural graphite and ethylene carbonate for a negative electrode, and has a feature of high energy density. Taking advantage of this feature, it is widely used in portable personal computers and telephone power supplies. In order to further increase the energy density of this battery, the introduction of a lithium metal anode is effective.

[0003] A lithium metal anode has a high discharge capacity,
Compared to a natural graphite negative electrode, its theoretical capacity is about 10 times per weight and about 2.5 times per volume. However, although the capacity is superior, the lithium metal anode has a serious problem. This is a change in the shape of the negative electrode accompanying the charge / discharge cycle, and the generation of dendritic lithium (hereinafter abbreviated as dendrite).

[0004] Dendrite is easily desorbed from the substrate, and the desorbed dendrite loses electrical contact with the substrate and is not used for the charge / discharge reaction. In addition, since lithium is a strong reducing agent, it reacts with the electrolytic solution to form a film. For this reason, when the surface area is increased by dendrites, the volume of the coating increases, and the amount of lithium that can be charged and discharged decreases. For these reasons, the generation of dendrites significantly reduces the cycle efficiency of the negative electrode. In order to maintain a long cycle number, a large excess amount of lithium must be filled with respect to the positive electrode capacity, resulting in a decrease in the energy density of the battery.

[0005] Also, a significant increase in lithium surface area can lead to battery heat generation, if used or stored at high temperatures. Procee
dings of Seventh International Meeting on Lithium
According to a report described in Batteries, P.12 (1994), when the negative electrode changes into a dendrite shape due to charge and discharge and the lithium surface area increases significantly, the self-heating rate sharply increases,
In extreme cases, thermal runaway is caused by reaction with the electrolyte.

Furthermore, dendrites penetrate through a porous separator made of polypropylene or polyethylene, causing an internal short circuit in the battery, or reducing cycle efficiency and safety.

In order to suppress the generation of the dendrite, research and development of a solid electrolyte that replaces the conventional organic electrolyte is being promoted. Above all, polymer electrolytes have attracted attention because they are flexible in shape and easy to form thin films. This electrolyte is a solid solution of a lithium salt in a polymer. 255 (199
As shown in 1), the effect of suppressing dendrite precipitation has also been confirmed. However, the ionic conductivity of the polymer electrolyte is
Polyethylene oxide (hereinafter referred to as PEO) -LiCl
In the case of the O ₄ composite, it is about 10 ⁻⁷ S / cm. This value is 10 for the organic electrolyte ^- extremely low as compared with ^{3 ~10 -2} S / cm. Therefore, when incorporating the above electrolyte into the battery,
Since the internal resistance increases, the discharge capacity of the battery is significantly impaired.

Therefore, in order to ensure the same ionic conductivity as the electrolyte, a gel electrolyte in which the electrolyte is impregnated in a polymer matrix has been developed. The polymer used for the gel is mainly soluble in the electrolyte such as PEO. Since the ionic conduction of the gel is carried out through the liquid phase contained therein, a high ionic conductivity at the level of the electrolyte can be obtained. However, since the polymer dissolves in the electrolytic solution and its mechanical strength is weakened, the function as a solid is lost. Therefore, when the gel is incorporated in the battery, dendrite growth cannot be completely suppressed, thereby causing an internal short circuit. Therefore, the problem is to improve the mechanical strength of the gel.

As a means for improving the mechanical strength of the gel electrolyte, for example, a mixture of a photocrosslinkable monomer and an electrolytic solution is irradiated with an electron beam or ultraviolet ray as disclosed in JP-A-5-109310 to form a crosslinkable gel electrolyte. However, a large improvement in mechanical strength has not been obtained. Further, the crosslinkable gel electrolyte is unstable with respect to a 4V-class positive electrode such as LiCoO ₂ , and the gel electrolyte may be decomposed or denatured in a short period of time.

Therefore, for example, Japanese Patent Application Laid-Open No. 61-183253
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. HEI 9-205, a method of coexisting a gel electrolyte and a porous polypropylene membrane has been developed.
However, the use of a porous polypropylene membrane does not provide an essential solution, and causes an internal short circuit due to lithium dendrite as in the case where the porous separator is used alone as described above.

[0011]

As described above, the gel electrolyte is required to have sufficient ionic conductivity for practical use, mechanical strength for preventing internal short circuit due to lithium dendrite, and stability for 4V class active materials. ing.

An object of the present invention is to provide a novel gel electrolyte which satisfies the above-mentioned various characteristics required for a gel electrolyte, and a battery using the same.

[0013]

In order to solve the above-mentioned problems, a gel polymer alloy electrolyte of the present invention comprises a polymer alloy film comprising a polymer which is hardly soluble in an organic electrolyte and a polymer which is soluble in an organic electrolyte. The size of the microphase separation was set to less than 100 nm. Since this value is smaller than the diameter of the dendrite, precipitation of dendrite does not occur.

Further, polymers that are hardly soluble in the electrolyte include P
VDF or vinylidene fluoride copolymer is used.
Soluble polymers include polymethyl methacrylate (PM
MA).

Further, the lithium polymer battery of the present invention comprises:
The gel polymer alloy electrolyte is disposed between a negative electrode and a positive electrode. By using the electrolyte of the present invention, a dendrite does not precipitate, so that a battery having high cycle efficiency and safety without causing internal short circuit can be realized.

Further, the negative electrode uses at least one selected from the group consisting of lithium metal, a lithium alloy, an inorganic compound capable of storing and releasing lithium, and a carbon material capable of storing and releasing lithium. Further, a lithium-containing transition metal oxide is used as the positive electrode active material.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The gel-like polymer alloy electrolyte of the present invention comprises a polymer alloy film comprising a polymer which is hardly soluble in an organic electrolyte and a polymer which is soluble in the organic electrolyte, and at least a soluble polymer alloy film which is phase-separated. It is a gelled polymer electrolyte in which the size of the polymer phase separation is less than 100 nm. By controlling the size of the phase separation of the polymer alloy film, the generation of lithium dendrite is suppressed.

Further, the lithium polymer battery of the present invention comprises:
1 is a lithium polymer battery including a gel polymer alloy electrolyte of the present invention disposed between a negative electrode and a positive electrode. By using the electrolyte of the present invention, a battery having high cycle efficiency and high safety without causing internal short circuit can be realized.

Further, there is provided a lithium polymer battery containing the polymer electrolyte of the present invention in at least one of a positive electrode and a negative electrode. By mixing the polymer electrolyte of the present invention in the electrode, it is possible to smoothly supply lithium ions or the electrolyte to the active material.

The polymer which is hardly soluble in the organic electrolyte is preferably at least one selected from the group consisting of polyvinylidene fluoride and a copolymer of vinylidene fluoride.

As the polymer soluble in the organic electrolyte, polymethyl methacrylate (hereinafter referred to as PMMA) is 100%.
Preferred for phase separation to a size less than nm.

Further, at least one selected from the group consisting of polyvinylidene fluoride and a copolymer of vinylidene fluoride.
A preferred combination is a polymer alloy film in which two polymers and polymethyl methacrylate are mixed or compatible with each other, and a gel polymer electrolyte made of an organic electrolyte.

Further, as the negative electrode, metallic lithium, a lithium alloy, an inorganic compound capable of occluding and releasing lithium,
At least one selected from the group of carbon materials capable of inserting and extracting lithium is used.

As a positive electrode active material, a lithium-containing transition metal oxide is used. The gelled polymer alloy electrolyte of the present invention suppresses the generation of lithium dendrite by controlling the size of the phase separation of the polymer alloy film.

The structure of the polymer alloy depends on the combination of the polymers, but includes a sea-island structure in which islands of the B polymer are scattered in the sea of the A polymer, and a modulation structure in which the A and B polymers are continuously intertwined. In any case, A polymer rich phase and B
It has a structure in which a micro phase is separated into a polymer rich phase, and its size is several μm or less.

The above-mentioned phase-separated structure is a factor for maintaining both the mechanical strength of the polymer alloy gel and the high ionic conductivity. When the polymer alloy film is immersed in the electrolytic solution, the electrolytic solution penetrates into the polymer soluble in the electrolytic solution to form a gel. However, since the poorly soluble polymer is micro-entangled, the soluble polymer is immobilized and does not flow. Therefore, it functions as a gel having high mechanical strength and high ion conductivity.

On the other hand, lithium dendrite has a thickness of 100 nm.
It has the above diameter. This size is the basis for designing a polymer alloy. Since the ionic conduction of the present electrolyte is performed through a polymer phase soluble in the organic electrolyte, lithium deposition is performed at the interface between this phase and the lithium negative electrode.

At this time, if the phase separation size of the soluble polymer of the polymer alloy is 100 nm or more, dendrite grows through the polymer phase. However, when the phase separation size is small and is equal to or less than the diameter of the dendrite, lithium cannot be deposited in a dendrite shape and grows flat.

Therefore, by using the electrolyte of the present invention, a battery having high cycle efficiency and high safety without causing internal short circuit can be realized.

The polymer which is preferably hardly soluble in the organic electrolyte to make the size of the phase separation smaller than 100 nm is at least one selected from the group consisting of polyvinylidene fluoride and a copolymer of vinylidene fluoride. Polymethyl methacrylate.

Further, since both polyvinylidene fluoride and PMMA are stable with respect to a 4V-class positive electrode active material such as LiCoO _2, it is difficult to realize a 4V-class lithium secondary battery which has been difficult to realize with the above-mentioned crosslinkable gel electrolyte. Applicable.

In particular, the effect is large when lithium metal on which dendrite is liable to precipitate is used as the negative electrode. However, the generation and growth of dendrites are improved compared to metallic lithium.For example, even when a lithium alloy, an inorganic compound capable of inserting and extracting lithium, and carbon are used, the safety and various properties can be improved by using the electrolyte of the present invention. Characteristics can be improved.

[0033]

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

Example 1 In this example, a gel electrolyte of a polymer alloy film obtained by making PVDF, which is a polymer hardly soluble in an organic solvent, and PMMA, which is a soluble polymer, compatible with each other was produced.

The method for producing the polymer alloy film is described below. First, N-methyl-2-pyrrolidinone (hereinafter NM)
P), 1 to 10% by weight of PVDF and 1 of PMMA
A polymer liquid in which 10% by weight was dissolved was mixed and adjusted at a weight ratio of 50:50. Next, the obtained solution was applied to a smooth metal plate or a glass plate, and the solvent was removed by evaporation in a dryer at 80 ° C. to obtain a thin polymer alloy film.
The amount of the solution applied was adjusted so that the film thickness became 20 μm. The obtained film was further vacuum-dried at 80 ° C. to sufficiently remove the residual solvent and moisture.

When the obtained polymer alloy film was observed with a transmission electron microscope, no clear phase separation structure was observed. If a phase separation structure of 100 nm or more exists, it can be sufficiently confirmed by a transmission electron microscope, and it can be concluded that the polymer alloy film of the present invention has a phase separation structure of less than 100 nm.

The gel electrolyte was obtained by immersing the polymer alloy film in a bath of an organic electrolyte. As the organic electrolyte, a solution prepared by dissolving 1.5 mol / l of LiPF ₆ as a solute in a 25:75 volume mixed solvent of ethylene carbonate and ethyl methyl carbonate was used.

The above gel electrolyte was punched out to a diameter of 17 mm, sandwiched between two pieces of metallic lithium foil having a diameter of 15 mm, placed in a coin-type battery case, and sealed to prepare a cell for ion conductivity measurement. As a result of measuring the ionic conductivity by the AC impedance method, the ionic conductivity was σ = 1.2 × 1
It was 0 ^-3 S · cm ^-1 .

Further, the above gel electrolyte was used for a 15 mm diameter.
The coin-shaped battery shown in FIG. The positive electrode layer 4 is made of a mixture of LiCoO _{2 as an} active material, an aqueous dispersion of carbon flux as a conductive material, and an aqueous dispersion of polytetrafluoroethylene as a binder at a weight ratio of 100: 3: 10. After being coated on the current collector 5, dried and rolled, it was punched out to a diameter of 12.5 mm. The negative electrode layer 2 was produced by directly pressing metal lithium having a diameter of 14 mm to the lid 3 of the coin-type battery case.
The above positive electrode, polymer alloy gel electrolyte 1, and negative electrode were laminated, placed in a coin-type battery case 6, and sealed with a gasket 7 to produce a battery of Example 1.

(Comparative Example 1) As the electrolyte, a gel electrolyte obtained by gelling polyvinylidene fluoride with an electrolytic solution and inserting it into the porous portion of a polypropylene porous membrane was used, and an ion conductor having the same structure as in Example 1 was used. A cell for measuring the degree and a coin-type battery were produced.

The cell for measuring ionic conductivity is as follows.
Produced. Ethylene carbonate and ethyl methyl carbonate
Lithium as a solute in a 25:75 volumetric mixed solvent
PF ₆7. A solution prepared by dissolving 1.5 mol / L
1.5 g of PVDF powder was added to 5 g and sufficiently dispersed.
The PVDF dispersion was mixed with polypropylene having a diameter of 17 mm.
After coating on a porous membrane separator (porosity 38%),
Between two pieces of metallic lithium foil having a diameter of 15 mm.
Installed in a coin-type battery case, sealed and measured for ion conductivity
A regular cell was prepared. 90 ° C 5
Heating for a minute to completely gel the PVDF dispersion
A more desired polymer gel electrolyte was prepared. After heating,
Cool coin cell to room temperature and use AC impedance method
Was used to measure the ionic conductivity of the gel electrolyte. The result
Result, σ = 8.1 × 10^-FourS ・ cm ^-1Met.

A coin-type battery was constructed in the same manner as in Example 1, and manufactured in the same manner as the cell for measuring ion conductivity.
This is referred to as a battery of Comparative Example 1.

(Comparative Example 2) A coin-type battery having the same configuration as that of Example 1 was manufactured using a crosslinkable gel electrolyte as the gel electrolyte.

The coin-type battery was manufactured as follows.
An electrolyte obtained by dissolving 1 mol / L of LiPF ₆ in an equal volume mixture of polyethylene glycol diacrylate, a photocrosslinkable polymer, photopolymerization initiator benzyl dimethyl ketal, propylene carbonate and ethylene carbonate, at a weight ratio of 20: 0.1: 80. To prepare a mixed solution. This solution was applied on the negative electrode metal lithium in a thickness of 50 μm, and this was irradiated with ultraviolet rays having a maximum output wavelength of 365 nm for 3 minutes. As a result, the monomer is polymerized and hardened, and a gel electrolyte containing a non-aqueous electrolyte is formed on the negative electrode metal lithium. The same positive electrode as in Example 1 was stacked thereon and placed in a battery case to obtain a battery of Comparative Example 2.

FIG. 2 shows charge / discharge curves of the batteries of Example 1 and Comparative Examples 1 and 2 in the first cycle. Battery test is 0.5
It is performed by a constant current method of 6 mA / cm ² , and is from 4.2 V to 3.0 V.
The measurement was performed at room temperature in a voltage range of V.

As shown in FIG. 2, the discharge capacity of the lithium polymer batteries of Example 1 and Comparative Example 1 is 2.0 mA / cm ² or more, and has sufficient performance as a normal temperature operation type battery. . On the other hand, the battery of Comparative Example 2 became flat when the battery voltage at the time of charging was around 4.1 V, and could not be charged to 4.2 V. This is considered to be because the crosslinkable gel electrolyte was decomposed by LiCoO _{2 having} a strong oxidizing effect.

Next, the batteries of Example 1 and Comparative Example 1 were charged.
Current 0.2C (0.56 mA / cm ^Two) And discharge current
0.2C (0.56mA / cm^Two), 0.5C (1.4
mA / cm^Two), 1.0 C (2.8 mA / cm^Two), 2.
0C (5.6 mA / cm^TwoTest under each condition of
Was measured for discharge capacity. The result is shown in FIG.

FIG. 3 shows that Example 1 is different from Comparative Example 1 in that
Excellent discharge characteristics at all discharge currents. This is because the gel electrolyte of the battery of Example 1 is made of only a substantially homogeneous polymer electrolyte because PVDF and PMMA are compatible with each other, and ion transfer is easily performed in the entire separator. On the other hand, Comparative Example 1 has a structure in which the porosity of the polypropylene porous membrane is as low as 38% and the gel electrolyte is packed in the pores of the porous membrane, so that ion transfer is not easily performed in the entire separator. This is because the process is partially performed only at the hole portion. As can be seen from FIG. 3, this difference becomes more pronounced as the discharge current value becomes higher and the discharge rate becomes higher.

FIG. 4 shows the cycle characteristics of the batteries of Example 1 and Comparative Example 1. The batteries of Example 1 and Comparative Example 1 were 3
It was charged and discharged stably until 00 cycles. When the battery of Example 1 was disassembled and observed at the end of the 300th cycle, dendrites were slightly deposited at the interface between the lithium negative electrode and the electrolyte, but no penetration of dendrites was observed. Similarly, when the battery of Comparative Example 1 was disassembled and observed, no penetration of dendrite was observed, but the battery was formed by the gel electrolyte in the pores of the polypropylene porous membrane. This proved that the battery of Example 1 suppressed the growth of lithium dendrite and functioned as a lithium secondary battery having high safety and high reliability.

Example 2 A polymer secondary battery was prepared in which the polymer alloy gel electrolyte of the present invention was also incorporated into a positive electrode and a negative electrode.

The positive electrode was made of 5 g of lithium cobaltate, 0.15 g of carbon black, and an N-methyl-2-pyrrolidinone (hereinafter referred to as NMP) solution of polyvinylidene fluoride (1).
2% by weight) and an NMP solution of polymethyl methacrylate (1
(2% by weight) was mixed, and the paste obtained was applied on an aluminum current collector, dried and rolled to obtain a paste having a diameter of 1%.
Punched to a size of 5 mm. Next, the obtained positive electrode was immersed in the same electrolytic solution as in Example 1, and the pressure was reduced to −50 cmHg and injected.

The negative electrode was made of 10 g of spherical graphite, 0.5 g of carbon fiber.
3g, NMP solution of polyvinylidene fluoride (12% by weight) and NMP solution of polymethyl methacrylate (12% by weight)
%), A paste prepared by mixing 8.4 g of a mixed solution of NMP, 4.2 g of NMP, and 4.2 g of acetonitrile was applied onto a copper current collector, dried, rolled, and punched to a size of 15 mm in diameter. Next, the obtained negative electrode was immersed in the same electrolytic solution as in Example 1, and the pressure was reduced to −50 cmHg and injected.

A polymer alloy gel electrolyte was prepared in the same manner as in Example 1, and was punched into a size having a diameter of 16 mm.

The above positive electrode, gel electrolyte, and negative electrode were laminated, placed in a coin-type battery case, and sealed. The obtained battery was set to a charge current of 0.2 C (0.56 mA / cm ² ), a discharge current of 0.2 C (0.56 mA / cm ² ), and 0.5 C
(1.4 mA / cm ² ), 1.0 C (2.8 mA / c)
m ² ) and 2.0 C (5.6 mA / cm ² ), and the discharge capacity was measured. The result is shown in FIG.

As is apparent from FIG. 3, the battery in which the gel electrolyte of the present invention is blended in the positive electrode and the negative electrode shows very good discharge characteristics even at high rate discharge. This can be attributed to two factors. The first is that the carbon anode has an overwhelmingly larger reaction area than the lithium metal anode. The second factor is that in the electrode plates of Example 1 and Comparative Example 1, the movement of lithium ions and the electrolyte during charge / discharge is hindered to some extent because the active materials are closely packed by rolling. On the other hand, the electrode plate of Example 2 blended in the electrode has the polymer alloy of the present invention around the active material, so that even when the rolled electrode is injected, this polymer alloy absorbs the electrolytic solution, and Lithium ions and electrolyte can be supplied smoothly. Therefore, it is considered that the battery of Example 2 can exhibit good characteristics even in high-rate discharge.

In this embodiment, PVDF is used as the polymer which is hardly soluble in the electrolytic solution. However, it may be a copolymer of vinylidene fluoride or another polymer.

In this embodiment, PMMA is used as the polymer soluble in the electrolytic solution. However, other polymers such as polymethyl acrylate and polyethyl methacrylate may be used.

In this embodiment, PVDF is used as the polymer which is hardly soluble in the organic electrolyte, and PMM is used as the polymer which is soluble in the organic electrolyte.
Although the appropriate compounding ratio when A was used was shown, the compounding ratio at which the function as a high ion conductive electrolyte having a small phase separation size and a high mechanical strength differs depending on the substance.

In the present embodiment, LiPF ₆ was used as a solute of the organic electrolyte, but this was made of LiCF ₃ SO ₃ , L
Other lithium salts such as iClO ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiAsF ₆ or LiBF ₄ may be used.

In this embodiment, an equal volume mixed solvent of propylene carbonate and ethylene carbonate is used as the solvent for the organic electrolyte. However, this may be another organic solvent or a mixed solvent.

In this embodiment, metallic lithium is used for the negative electrode. However, the present invention is also effective for a lithium ion battery system, and uses a lithium alloy, an inorganic compound capable of occluding and releasing lithium, or occluding and releasing lithium. A possible carbon material may be used.

In this embodiment, the positive electrode active material is LiC
Although oO ₂ was used, it may be another lithium transition metal oxide such as LiNiO ₂ , LiMn ₂ O _4, or LiMnO ₂ , and lithium-free MnO ₂ or V ₂ O ₅
And the like.

[0063]

As described above, according to the present invention, at least the soluble polymer of the polymer alloy film has a thickness of 100 nm.
By using a gel-like polymer alloy electrolyte that is phase-separated on a scale smaller than that, generation of lithium dendrite can be suppressed. Also, by arranging this between the negative electrode and the positive electrode for the lithium battery,
A battery with good battery characteristics and high safety and reliability was obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a coin-type lithium battery using a gel electrolyte of the present invention.

FIG. 2 is a diagram showing charge / discharge curves of lithium batteries using the gel electrolyte of the present invention and a comparative gel electrolyte.

FIG. 3 is a diagram showing discharge characteristics of lithium batteries using the gel electrolyte of the present invention and a comparative gel electrolyte.

FIG. 4 is a diagram showing cycle characteristics of lithium batteries using the gel electrolyte of the present invention and a comparative gel electrolyte.

[Explanation of symbols]

 Reference Signs List 1 gel electrolyte 2 negative electrode layer 3 lid 4 positive electrode layer 5 positive electrode current collector 6 battery case 7 gasket

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Akiko Ishida 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A polymer alloy film comprising a polymer which is hardly soluble in an organic electrolyte and a polymer soluble therein, and a gel polymer electrolyte comprising an organic electrolyte, wherein at least a polymer phase of the polymer alloy film which is phase-separated is soluble. A polymer electrolyte having a separation size of less than 100 nm. 2. The polymer electrolyte according to claim 1, wherein the polymer that is hardly soluble in the organic electrolyte is at least one selected from the group consisting of polyvinylidene fluoride and a copolymer of vinylidene fluoride. 3. The polymer electrolyte according to claim 1, wherein the polymer soluble in the organic electrolyte is polymethyl methacrylate. 4. A gel polymer electrolyte comprising a polymer alloy film in which at least one polymer selected from the group consisting of polyvinylidene fluoride or a copolymer of vinylidene fluoride and polymethyl methacrylate is mixed or dissolved, and an organic electrolyte solution. 2. The polymer electrolyte according to claim 1, wherein at least the soluble polymer of the phase-separated polymer alloy film has a phase separation size of less than 100 nm. 5. A lithium battery having a structure in which a polymer electrolyte is disposed between a negative electrode and a positive electrode, wherein the polymer electrolyte is a polymer alloy film comprising a polymer which is hardly soluble in an organic electrolyte and a polymer which is soluble in the organic electrolyte, and a gel comprising the organic electrolyte. A lithium polymer battery which is a solid polymer electrolyte and wherein the size of at least the soluble polymer phase separation of the phase separated polymer alloy film is less than 100 nm. 6. The lithium polymer battery according to claim 5, wherein the polymer electrolyte is contained in a negative electrode or a positive electrode. 7. The negative electrode according to claim 5, wherein the negative electrode is at least one selected from the group consisting of lithium metal, a lithium alloy, an inorganic compound capable of storing and releasing lithium, and a carbon material capable of storing and releasing lithium. Lithium polymer battery. 8. The lithium polymer battery according to claim 5, wherein the positive electrode active material is a lithium-containing transition metal oxide. 9. The polymer insoluble in an organic electrolyte is at least one selected from the group consisting of polyvinylidene fluoride and a copolymer of vinylidene fluoride.
4. The lithium polymer battery according to 1. 10. The lithium polymer battery according to claim 5, wherein the polymer soluble in the organic electrolyte is polymethyl methacrylate.