JP2002042891A - Thin-type lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-type lithium secondary battery improved in the performance of a utilization factor or the like by uniformly dispersing a nonaqueous electrolyte filled in a power generating element. SOLUTION: This thin-type lithium secondary battery is provided with the power generating element comprising a positive electrode, a negative electrode and a separator. The positive and negative electrodes and the separator contain at least the nonaqueous electrolyte and a polymer with a function of holding the electrolyte. When the power generating element is swollen containing the nonaqueous electrolyte, the area (mm2) of the power generating element/the thickness (mm) of the power generating element is 250-15,000. The nonaqueous electrolyte contains 0.01-1,0 mass% of at least one surface active agent selected out of an anionic surface active agent with a perfluoroalkyl group, and a nonionic surface active agent with a perfluoroalkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thin lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a non-aqueous electrolyte secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. Such a secondary battery includes a negative electrode using lithium or a lithium alloy as an active material, a positive electrode containing an oxide, sulfide, or selenide such as molybdenum, vanadium, titanium, or niobium as an active material, and a nonaqueous electrolyte. There is known a lithium secondary battery including:

In recent years, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, such as coke, graphite, carbon fiber, a resin fired body, and pyrolytic gas phase carbon, has been used as a negative electrode. The development and commercialization of lithium ion secondary batteries using lithium and lithium manganese oxide-containing batteries are being actively pursued.

Meanwhile, in order to further reduce the weight and size of the secondary battery, for example, US Pat.
As disclosed in US Patent No. 6,318, a polymer lithium secondary battery has been developed. The polymer lithium secondary battery (thin lithium secondary battery) includes a positive electrode having a structure in which a positive electrode layer including an active material, a nonaqueous electrolyte, and a polymer holding the electrolyte is supported on a current collector; A negative electrode having a structure in which a negative electrode layer containing a non-aqueous electrolyte and a polymer holding the electrolyte is supported on a current collector; and a non-aqueous electrolyte and a polymer holding the electrolyte disposed between the positive and negative electrodes. And a separator made of an electrolyte sheet containing: This polymer lithium secondary battery contains substantially no liquid component because the non-aqueous electrolyte is held by the polymer, and since the positive and negative electrodes and the separator are integrated, the exterior material is like a laminate film. Simple simple ones can be used. For this reason, the secondary battery is thin, lightweight,
It has the feature of being excellent in safety. Further, in the polymer lithium secondary battery, a non-aqueous electrolyte unimpregnated separator is disposed between the non-aqueous electrolyte unimpregnated positive and negative electrodes, and these are integrated by heating and pressurizing to form a laminate. After removing the plasticizer contained in the laminate, the laminate is impregnated with a non-aqueous electrolytic solution, and the obtained power generation element is sealed with an exterior material.

[0005]

In such a thin lithium secondary battery, in order to increase the reactivity, a positive electrode layer,
The negative electrode layer is thin. In addition, since a metal foil is used as the current collector, the liquid is mainly absorbed from the end face without passing through the nonaqueous electrolyte. However, since the thin lithium secondary battery has a large area to thickness ratio and a high swelling property of the separator with the non-aqueous electrolyte, when a required amount of the electrolyte is injected into the power generation element, the electrolyte is partially electrolyzed. There is a possibility that a portion where the liquid is insufficient may occur, and the charge / discharge cycle characteristics may deteriorate.

An object of the present invention is to provide a thin lithium secondary battery in which a nonaqueous electrolyte injected into a power generation element is uniformly dispersed to improve the performance such as the utilization factor.

[0007]

A thin lithium secondary battery according to the present invention includes a power generating element comprising a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, wherein the positive and negative electrodes and the separator are at least provided. When the power generation element contains a non-aqueous electrolyte and a polymer having a function of holding the electrolyte, and the power generation element swells with the non-aqueous electrolyte, the area of the power generation element (mm ² ) / the thickness of the power generation element (Mm) is 25
A thin lithium secondary battery that is 0 to 15000,
The non-aqueous electrolyte contains 0.01 to 1.0% by mass of at least one surfactant selected from an anionic surfactant having a perfluoroalkyl group and a nonionic surfactant having a perfluoroalkyl group. It is characterized by doing.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thin lithium secondary battery according to the present invention will be described below with reference to FIGS.

FIG. 1 is a plan view showing an example of the thin lithium secondary battery according to the present invention, and FIG. 2 is a sectional view showing the thin lithium secondary battery of FIG.

This thin lithium secondary battery comprises a positive electrode 1,
A power generating element mainly comprising an integrated negative electrode 2 and a separator 3 disposed between the positive electrode 1 and the negative electrode 2 is provided. When the power generation element contains a non-aqueous electrolyte and swells, assuming that the area of the power generation element is S (mm ² ) and its thickness is t (mm), S / t = 250 to 15000;
Preferably, S / t = 500 to 10,000 is satisfied.

The positive electrode 1 comprises a porous current collector 4 and a positive electrode layer 5 adhered to both surfaces of the current collector 4. The negative electrode 2 includes a porous current collector 6 and a negative electrode layer 7 bonded to both surfaces of the current collector 6.

A strip-shaped positive electrode terminal 8 is connected to the current collector 4 of each of the positive electrodes 1 and extends out of the positive electrodes 1.
The strip-shaped negative electrode terminal 9 is connected to the current collector 6 of the negative electrode 2 and extends outside the negative electrode 2. For example, a positive electrode lead 10 made of a strip-shaped aluminum plate is connected to the two positive electrode terminals 8. For example, a negative electrode lead 11 made of a strip-shaped copper plate is connected to the negative electrode terminal 9. The power generating element having such a configuration is housed and sealed in an exterior material 12 having a barrier function against moisture so that the positive electrode lead 10 and the negative electrode lead 11 extend outside from the exterior material 12. .

As the positive electrode 1, the negative electrode 2, the separator 3, and the exterior material 12 of the thin lithium secondary battery, for example,
Those described below can be used.

(1) Positive Electrode 1 The positive electrode 1 includes a porous current collector 4, a positive electrode active material, a non-aqueous electrolyte, and a polymer holding the electrolyte, which are adhered to both surfaces of the current collector 4. And a positive electrode layer 5.

Examples of the positive electrode active material include various oxides (eg, lithium manganese composite oxide such as LiMn ₂ O ₄ , manganese dioxide, lithium-containing nickel oxide such as LiNiO _2, and lithium-containing cobalt oxide such as LiCoO _2). Oxide, lithium-containing nickel-cobalt oxide, lithium-containing amorphous vanadium pentoxide and the like, and chalcogen compounds (for example, titanium disulfide and molybdenum disulfide). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.

Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and dimethyl carbonate (D
MC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ-
BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. The non-aqueous solvents may be used alone or as a mixture of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium hexafluorophosphate (L
iPF _6), boric tetrafluoride lithium (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium salts such as lithium trifluoromethane sulfonate (LiCF ₃ SO ₃₎ may be mentioned.

The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.2 mol / l to 2 mol / l.

The polymer has, for example, a physical gel or a chemically crosslinked structure, and has a binding function in addition to a function of holding a nonaqueous electrolyte. Such polymers include, for example,
It is possible to use a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, polytetrafluoropropylene, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), polyvinylidene fluoride (PVdF), or the like. it can. Above all, a resin containing VdF is preferable.

The positive electrode is allowed to contain a conductive material from the viewpoint of improving conductivity. Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like.

As the porous current collector, for example, a foil, a mesh, an expanded metal, a punched metal, or the like made of aluminum or an aluminum alloy can be used.

(2) Negative Electrode 2 This negative electrode 2 has a porous current collector 6 and a negative electrode which is laminated on both sides of the current collector 6 and contains an active material, a non-aqueous electrolyte and a polymer holding the electrolyte. And a layer 7.

Examples of the negative electrode active material include carbonaceous materials that occlude and release lithium ions. Such carbonaceous materials include, for example, those obtained by firing organic polymer compounds (eg, phenolic resin, polyacrylonitrile, cellulose, etc.), those obtained by firing coke and mesophase pitch, and those made by artificial graphite. And carbonaceous materials represented by natural graphite and the like. Among them, it is preferable to use a carbonaceous material obtained by firing the mesophase pitch at a temperature of 500 ° C. to 3000 ° C. in an inert gas atmosphere such as an argon gas or a nitrogen gas under normal pressure or reduced pressure.

As the non-aqueous electrolyte, those similar to those described above for the positive electrode are used.

It is desirable that the polymer has a binding function in addition to the function of holding the non-aqueous electrolyte. As such a polymer, a polymer of the same type as that described for the above-described positive electrode can be used, and among them, a resin containing VdF is preferable.

As the porous current collector, for example, a foil, mesh, expanded metal, punched metal, or the like made of copper or a copper alloy can be used.

(3) Separator 3 The separator 3 contains a non-aqueous electrolyte and a polymer having a function of holding the electrolyte.

Examples of the nonaqueous electrolyte include the same ones as described for the positive electrode.

The polymer desirably has a binding function in addition to the function of holding the non-aqueous electrolyte. As such a polymer, the same type of polymer as that described for the above-described positive electrode can be used.
HFP copolymers are preferred.

From the viewpoint of further improving the strength, the separator is allowed to further contain an organic filler or an inorganic filler such as silicon oxide powder.

(4) Exterior Material 12 The exterior material 12 is made of, for example, a laminated film in which a heat-fusible resin is disposed at least in a sealing portion and a metal thin film such as aluminum (Al) is interposed inside. Preferably, Specifically, a laminated film of acid-modified polypropylene (PP) / polyethylene terephthalate (PET) / Al foil / PET laminated from the sealing portion side to the outer surface; acid-modified PE / nylon / Al foil / PET
Laminated film; ionomer / Ni foil / PE /
A laminate film of PET; a laminate film of ethylene vinyl acetate (EVA) / PE / Al foil / PET; a laminate film of ionomer / PET / Al foil / PET can be used. Here, the film other than the acid-modified PE, the acid-modified PP, the ionomer, and the EVA on the sealing portion has moisture resistance, gas permeability, and chemical resistance.

The nonaqueous electrolyte in the positive and negative electrodes and the separator constituting the power generating element is at least one selected from an anionic surfactant having a perfluoroalkyl group and a nonionic surfactant having a perfluoroalkyl group. The surfactant is contained in an amount of 0.01 to 1.0% by mass. As the anionic surfactant having a perfluoroalkyl group, for example, lithium perfluorooctanesulfonate is used, and as the nonionic surfactant having the perfluoroalkyl group, for example, a perfluoroalkylethylene oxide adduct is used. be able to. When the content (addition amount) of such a surfactant is less than 0.01% by mass relative to the non-aqueous electrolyte, the non-aqueous electrolyte is uniformly dispersed in the positive and negative electrodes (the positive electrode layer and the negative electrode layer) and the separator. It becomes difficult to make it. On the other hand, when the content (addition amount) of the surfactant exceeds 1.0% by mass with respect to the non-aqueous electrolyte, the utilization may decrease. More preferably, the content (addition amount) of the surfactant with respect to the non-aqueous electrolyte is 0.
05 to 0.5% by mass.

Although an example in which a current collector having a porous structure is used as the negative electrode current collector has been described with reference to FIG. 1, a metal foil such as a copper foil may be used. Further, in the positive electrode of FIG. 1 described above, the positive electrode layer is supported on both surfaces of the porous current collector, but the positive electrode layer may be supported on only one surface of the porous current collector.

In FIG. 1, the positive electrode, the electrolyte layer, the negative electrode, the electrolyte layer and the positive electrode are stacked in this order.
Although the example in which the power generation element having the layer structure is used has been described, the power generation element is not limited to this, and a power generation element having a three-layer structure including a positive electrode, an electrolyte layer, and a negative electrode may be used. A power generating element having a three-layer structure includes a positive electrode having a structure in which a positive electrode layer is supported on both surfaces of a porous current collector;
A negative electrode having a structure in which a negative electrode layer is supported on both surfaces of a porous current collector, and a structure including an electrolyte layer disposed between the positive and negative electrodes, or a positive electrode on one surface of a metal foil such as an aluminum foil A positive electrode having a structure in which a layer is supported, a negative electrode having a structure in which a negative electrode layer is supported on one side of a metal foil such as a copper foil, and a structure including an electrolyte layer disposed between the positive and negative electrode layers Can be.

According to the present invention described above, when the power generating element composed of the positive and negative electrodes and the separator swells by containing the non-aqueous electrolyte, the area of the power generating element (mm ² ) / the thickness of the power generating element (mm) Is a large area structure of 250 to 15000, at least one selected from an anionic surfactant having a perfluoroalkyl group and a nonionic surfactant having a perfluoroalkyl group in the non-aqueous electrolyte in the power generating element. By containing the surfactant in an amount of 0.01 to 1.0% by mass, the nonaqueous electrolyte can be uniformly dispersed throughout the positive and negative electrodes (the positive electrode layer and the negative electrode layer) and the entire separator. As a result, a thin lithium secondary battery with low resistance and high utilization can be obtained.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

Example 1 <Preparation of Positive Electrode Not Impregnated with Nonaqueous Electrolyte> 90% by mass of a lithium-cobalt composite oxide having a composition formula of LiCoO ₂ as an active material, 6% by mass of graphite, and polyvinylidene 4% by mass of fluoride (PVdF) and N-methyl-2
-A slurry was prepared by mixing in pyrrolidone (NMP). This slurry was applied on an aluminum foil and dried to prepare a 200 g / m ² non-aqueous electrolyte non-impregnated positive electrode.

<Preparation of Negative Electrode Impregnated with Non-Aqueous Electrolyte> 90% by weight of mesophase pitch carbon fiber and 10% by weight of polyvinylidene fluoride (PVdF) were N-methyl-2-
A slurry was prepared by mixing in pyrrolidone (NMP). The slurry was applied on a copper foil and dried to prepare a non-aqueous electrolyte non-impregnated negative electrode of 100 g / m ² .

<Preparation of Separator> First, polyvinylidene fluoride (PVdF) was dissolved in N-methyl-2-pyrrolidone (NMP), and polyacrylonitrile (PAN) powder was dispersed in this solution. After applying this slurry on a glass plate, it was immersed in pure water and dried to produce a separator precursor sheet. Subsequently, this sheet was further immersed in an aqueous dispersion of an ethylene-vinyl acetate copolymer, and dried to produce a non-aqueous electrolyte non-impregnated separator.

<Preparation of Non-Aqueous Electrolyte> A non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (MEC) were mixed at a volume ratio of 1: 2 was mixed with LiPF ₆ as an electrolyte at a concentration of 1 mol. / L and further added 0.1% by mass of lithium perfluorooctanesulfonate (anionic surfactant) to prepare a non-aqueous electrolyte.

<Assembly of Battery> The positive electrode not impregnated with the nonaqueous electrolyte was 50 mm × 50 mm, and the negative electrode not impregnated with the nonaqueous electrolyte was 55 mm.
mm × 55 mm, the non-aqueous electrolyte unimpregnated separator
Each was cut into a size of 0 mm × 60 mm, and these were laminated with a non-aqueous electrolyte non-impregnated positive electrode, a non-aqueous electrolyte non-impregnated separator, and a non-aqueous electrolyte non-impregnated negative electrode. Subsequently, after the aluminum lead and the copper lead were welded to the positive electrode and the negative electrode, respectively, the respective leads were placed in a laminated film laminated in the order of polyethylene terephthalate (PET) film, aluminum foil and polyethylene (PE) from the outermost layer. It was arranged so as to extend to the outside, and the three sides excluding the injection port of the non-aqueous electrolyte were heat-sealed and housed in the exterior material made of the laminate film. Thereafter, 0.3 g of the non-aqueous electrolyte was injected through the injection port of the exterior material, and the injection section was heat-sealed and sealed to assemble a thin lithium secondary battery. At this time, the ratio of the area (mm ² ) / thickness (mm) of the power generating element including the positive and negative electrodes and the separator swollen by the impregnation with the nonaqueous electrolyte was 7000.

Example 2 A thin lithium secondary battery similar to that of Example 1 was used except that a non-aqueous electrolyte to which lithium perfluorooctanesulfonate (anionic surfactant) was added in an amount of 0.05% by mass was used. Battery was assembled.

Example 3 A thin lithium secondary battery similar to that of Example 1 was used except that 0.01% by mass of lithium perfluorooctanesulfonate (anionic surfactant) was added as a nonaqueous electrolyte. Battery was assembled.

Example 4 A thin lithium secondary battery similar to that of Example 1 was used except that lithium perfluorooctanesulfonate (anionic surfactant) was added in an amount of 0.5% by mass as a non-aqueous electrolyte. Battery was assembled.

Example 5 A thin lithium secondary battery similar to that of Example 1 was used except that lithium perfluorooctanesulfonate (anionic surfactant) to which 1.0% by mass was added was used as the nonaqueous electrolyte. Battery was assembled.

Comparative Example 1 A thin lithium secondary battery similar to that of Example 1 was assembled except that a non-aqueous electrolyte solution without a surfactant was used.

Comparative Example 2 A thin lithium secondary battery similar to that of Example 1 was used except that 2.0% by mass of lithium perfluorooctanesulfonate (anionic surfactant) was added as a non-aqueous electrolyte. Battery was assembled.

(Embodiment 6) Area of power generating element (mm ² ) /
A thin lithium secondary battery similar to that of Example 1 was assembled except that the thickness (mm) ratio was changed to 2800.

(Embodiment 7) Area of power generating element (mm ² ) /
A thin lithium secondary battery similar to that of Example 1 was assembled except that the thickness (mm) ratio was 350.

(Embodiment 8) Area of power generating element (mm ² ) /
A thin lithium secondary battery similar to that of Example 1 was assembled except that the thickness (mm) ratio was changed to 3500.

Comparative Example 3 Area of Power Generating Element (mm ² ) /
A thin lithium secondary battery similar to that of Example 1 was assembled except that the thickness (mm) ratio was changed to 18,000.

Example 9 The same thin lithium secondary battery as in Example 1 was used except that a perfluoroalkylethylene oxide adduct (nonionic surfactant) to which 0.1% by mass was added was used as the nonaqueous electrolyte. Battery was assembled.

Comparative Example 4 A thin lithium secondary battery similar to that in Example 1 was used except that a perfluoroalkyltrimethylammonium salt (cationic surfactant) to which 0.1% by mass was added was used as the nonaqueous electrolyte. Battery was assembled.

Comparative Example 5 A thin lithium secondary battery similar to that of Example 1 was used except that a perfluoroalkylaminosulfonic acid salt (amphoteric surfactant) to which 0.1% by mass was added was used as the nonaqueous electrolyte. Battery was assembled.

The obtained Examples 1 to 9 and Comparative Examples 1 to 5
After injecting the non-aqueous electrolyte into the exterior material, elapse of 1 hour, 6 hours, 12 hours, and 24 hours, and then measuring the resistance value by the AC method, the power generating element The distribution state of the non-aqueous electrolyte in the sample was examined. The results are shown in Table 1 below.

After the elapse of 24 hours, charging is performed by a constant current constant voltage method with a final voltage of 4.2 V corresponding to 0.2 C.
Discharge is performed by a constant current method of 0.2 C, a cycle of charge-discharge-charge-discharge-charge is performed, and further discharge is performed at 1.0 C, and capacity at the second discharge (100%)
The volume ratio (%) with respect to was measured. The resistance value after the discharge was measured by an AC method. Further, after the discharge, the battery was disassembled and the distribution of the non-aqueous electrolyte on the electrode surface was visually inspected.

The results are shown in Table 2 below.

[0059]

[Table 1]

[0060]

[Table 2]

As is clear from Table 1, the secondary batteries of Examples 1 to 9 having the non-aqueous electrolyte solution to which the anionic and nonionic surfactants were added have a high permeability of the non-aqueous electrolyte solution. , Because the non-aqueous electrolyte penetrates the entire power generation element,
It can be seen that the resistance value is lower than that of the secondary battery of Comparative Example 1 having a non-aqueous electrolyte without a surfactant. Also, it can be seen that the higher the area / thickness ratio of the power generating element, the lower the permeability of the electrolyte.

As is clear from Table 2, the secondary batteries of Examples 1 to 9 having a non-aqueous electrolyte containing 0.01 to 1.0% by mass of an anionic and nonionic surfactant were added. It turns out that it has a high utilization rate of 89%.

On the other hand, the secondary battery of Comparative Example 1 having a non-aqueous electrolyte solution without a surfactant has a high resistance value and a low utilization factor. This is due to the fact that the non-aqueous electrolyte did not sufficiently penetrate into the entire power generation element as a result of decomposition after discharge and visual inspection.

The secondary battery of Comparative Example 2 having a non-aqueous electrolyte containing 2.0% by mass of an anionic surfactant which is larger than the upper limit (1.0% by mass) of the present invention has a high resistance value. And the usage rate is low. This is because the non-aqueous electrolyte has sufficiently penetrated the entire power generating element by decomposition and visual inspection after discharge, but the utilization rate has been reduced due to the inhibition of the electrode reaction due to the increased amount of surfactant added. It is expected to be.

The utilization rates of the secondary batteries of Comparative Examples 4 and 5 each having a non-aqueous electrolyte containing 0.1% by mass of a cationic or amphoteric surfactant as a surfactant are low.

From the above results, it can be seen that the thin lithium secondary battery according to the present invention (where the area / thickness ratio of the power generating element is 250 to 1).
In (5000), the surfactants to be added to the non-aqueous electrolyte are not all applicable, and specific surfactants, that is, anionic and nonionic surfactants, are used, and the addition amount is 0.01 to 1. By specifying the amount to be 0% by mass, it is possible to reduce the internal resistance and achieve an improvement in the utilization factor.

[0067]

As described above in detail, according to the present invention, it is possible to provide a thin lithium secondary battery in which the nonaqueous electrolyte injected into the power generating element is uniformly dispersed to improve the performance such as the utilization factor. it can.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a thin lithium secondary battery according to the present invention.

FIG. 2 is a sectional view showing the thin lithium secondary battery of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Separator, 4 ... Positive electrode collector, 5 ... Positive electrode layer, 6 ... Negative electrode current collector, 7 ... Negative electrode layer, 12 ... Exterior material.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiji Hibino 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 5H021 EE02 EE10 EE33 EE34 HH01 5H029 AJ03 AK03 AL06 AL07 AL08 AM03 AM04 AM05 AM07 BJ04 DJ04 DJ09 HJ01 HJ04 HJ07

Claims (2)

[Claims] 1. A polymer having a power generating element comprising a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, wherein the positive and negative electrodes and the separator have at least a non-aqueous electrolyte and a polymer having a function of holding the electrolyte. And when the power generation element swells with the non-aqueous electrolyte, the area of the power generation element (mm ² ) / the thickness of the power generation element (mm) is 25
0 to 15,000, wherein the non-aqueous electrolyte is at least one selected from an anionic surfactant having a perfluoroalkyl group and a nonionic surfactant having a perfluoroalkyl group. A thin lithium secondary battery comprising 0.01 to 1.0% by mass of a surfactant. 2. The thin lithium secondary battery according to claim 1, wherein the separator holds the non-aqueous electrolyte with a polymer having a physical gel or a chemically crosslinked structure.