JPH1145738A - Lithium secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery which excels in cycle characteristics and is free from characteristic deterioration even if a pressure is imposed thereon or it is bent. SOLUTION: This battery consists of a positive electrode and a negative electrode, both of which can store/discharge lithium ions, as well as a polymer electrolyte. In this event, an active material layer including a compound capable of storing/releasing positive and negative lithium ions, being provided on a current collector and a polymer electrolyte layer being provided on the active material layer, an Rp value (average line height) of a surface of the active material layer is adapted to be 0.1 μm to 20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a lithium secondary battery. More specifically, instead of the conventional liquid electrolyte,
The present invention relates to a lithium secondary battery using a polymer electrolyte (including one in which an electrolyte is impregnated or held in a polymer), and relates to an excellent lithium secondary battery that has excellent cycle characteristics and can withstand external pressure and bending.

[0002]

2. Description of the Related Art In recent years, various devices such as a camera-integrated VTR device, an audio device, a portable computer, and a cellular phone have been reduced in size and weight, and there has been a demand for higher performance of a battery as a power supply for these devices. Is growing. Above all, development of lithium secondary batteries capable of achieving high voltage, high energy density and excellent cycle characteristics as batteries as power sources for electric vehicles has been active.

A lithium secondary battery generally comprises a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution. For example, an electrode containing lithium cobalt oxide for the positive electrode, an electrode containing a carbon material for the negative electrode, And in the case of a secondary battery using an electrolyte solution, lithium ions are occluded in the negative electrode through the electrolyte solution during charging while the lithium ions are released from the negative electrode through the electrolyte solution during discharge and the positive electrode is discharged through the electrolyte solution. It is to be absorbed inside. As a characteristic required for this electrode, the ability to occlude and release lithium ions to and from the electrode is large, and it is necessary to suppress a decrease in each ability due to the repetition (cycle) of occlusion and release.

The characteristics required for the positive electrode of such an excellent lithium secondary battery include conductivity in the positive electrode layer. Compounds that can store and release lithium ions used for the positive electrode often use oxides with little conductivity,
Since this alone does not function as a positive electrode, it is generally used as a positive electrode by imparting conductivity using a conductive substance such as carbon. Conventionally, non-aqueous electrolytes have been used to obtain high voltage. On the other hand, when a non-aqueous electrolyte is used, the filtrate is in a liquid state and therefore has a danger of ignition accompanying it.In recent years, a non-aqueous electrolyte has been used to improve safety. For example, a so-called polymer electrolyte in which a gel polymer is impregnated or held or a polymer itself functions as an electrolyte has been developed.

In particular, in a lithium secondary battery, heat generation and ignition due to an internal short circuit due to lithium dendrite deposition when an electrolyte solution is used poses a problem, and development and application of an excellent polymer electrolyte have been desired. . Further, since the above-mentioned polymer electrolyte itself can serve as a substitute for a separator used in a secondary battery system, a positive electrode and a negative electrode can be sandwiched between the polymer electrolyte without using a separator as in the related art. A battery can be formed by joining. By using a polymer electrolyte in this way, the weight and shape flexibility are improved, so that, for example, a thin film such as a sheet can be formed, and there is an advantage that a lightweight and space-saving battery can be manufactured. Also, the polymer electrolyte is
To reduce the internal resistance of the battery and improve the energy density, it is desired that the battery be as thin as possible without causing an internal short circuit.

[0006]

The polymer electrolyte is provided on the active material layer of the electrode. In this case, the polymer electrolyte may be impregnated in the active material layer or may be formed independently. When using a polymer electrolyte having low mechanical strength such as gel, especially when the polymer electrolyte is thinned, if the surface of the active material layer of the positive electrode or the negative electrode in contact with the polymer electrolyte layer is rough, a small amount of Even at a high pressure, internal short-circuiting between the positive and negative electrodes may occur, or the concentration of current may cause the generation of dendrite, deteriorating the cycle characteristics. Further, if the surface of the active material is completely flattened, there is a problem that the adhesiveness to the polymer electrolyte layer is reduced, the separation is easily caused, and the characteristic flexibility of the polymer battery is impaired.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above situation, and as a result of intensive studies to obtain a lithium secondary battery having excellent cycle characteristics, it has been found that the surface of the active material layer of the positive electrode and the negative electrode has By setting the roughness to a specific range, and furthermore, by setting the surface roughness of the polymer electrolyte layer to a specific range, an internal short circuit is hard to occur, and a lithium secondary battery having excellent cycle characteristics and excellent flexibility is provided. It is found that it can be obtained and is completed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The surface roughness referred to in the present invention can be calculated by any method. For example, it can be determined from a roughness curve measured using a non-contact or contact type surface roughness meter. Also,
For example, the surface roughness of the contact surface between the polymer electrolyte layer and the active material layer may be measured by measuring the surface roughness by peeling off the interface or by observing the cut surface with a microscope such as an SEM. A curve may be obtained and calculated. As for Rp and Rv, for example, an average line is obtained from the roughness curves obtained by the above-described method using the least square method. The Rp value (average line height) is the distance between the average line and the highest peak of the roughness curve,
The Rv value (average line depth) is the distance between the average line and the deepest valley bottom.

In the present invention, the Rp value of the active material surface of the positive and negative electrodes is preferably 0.1 μm to 20 μm, and the Rv value is preferably 0.1 μm to 50 μm. The Rp value is particularly preferably 1 to 10 μm. When the Rp value exceeds 20 μm, the battery may easily cause an internal short circuit, the cycle characteristics may be deteriorated due to local current concentration, or dendrite may be generated. Also,
If the thickness is less than 0.1 μm, the adhesion to the polymer electrolyte may be reduced, and the flexibility of the battery may be impaired. Further, the Rv value is particularly preferably 1 μm to 20 μm. R
If the v value exceeds 50 μm, the capacity of the battery decreases,
If the thickness is less than 0.1 μm, the adhesiveness to the polymer electrolyte may be adversely affected.

Further, in the present invention, when the polymer electrolyte layer is formed independently of the active material layer, the Rp value of the contact surface of the polymer electrolyte layer with the active material layer is 0.1 μm.
It is preferable that the Rv value is 0.1 μm to 20 μm. The Rp value is particularly preferably 1 to 10 μm. If the Rp value exceeds 50 μm, the capacity of the battery may be reduced. If the Rp value is less than 0.1 μm, the adhesiveness to the electrolyte may be adversely affected. The Rv value is particularly preferably 1 μm to 10 μm. Rv
When the value exceeds 20 μm, the battery is likely to cause an internal short circuit or local current concentration, which may lead to a decrease in cycle characteristics and dendrite generation. On the other hand, when the thickness is less than 0.1 μm, the adhesiveness to the positive and negative electrode active material layers is reduced, and the flexibility of the battery may be impaired.

In the lithium secondary battery of the present invention, by setting the surface roughness of the electrode active material layer and the surface of the polymer electrolyte layer to a specific range, the thickness of the polymer electrolyte (layer) is particularly reduced to 50 μm or less. Suitable lithium secondary batteries can also be obtained. Although the thickness of the polymer electrolyte (layer) is arbitrary, it is usually 10 to 50 μm.
It is.

The relationship between Rp and the short circuit also depends on the thickness of the electrolyte. In recent years, the demand for improvement in energy density has been increasing, and as a result of examining the relationship between the average thickness (d) of the electrolyte layer, the average line height (Rp) of the active material layer surface, and the battery characteristics, Rp / d was found to be It has been found that good properties can be obtained with good yield when the ratio is 0.3 or less, especially 0.3 to 0.002, particularly 0.25 to 0.05.
If Rp / d exceeds 0.3, local current concentration may cause shortening due to generation of dendrite in a high potential portion of 3700 mV or more, or cause deterioration of cycle characteristics in large current charging / discharging. .

[0013] The lithium secondary battery of the present invention mainly comprises a positive electrode, a negative electrode and a polymer electrolyte. First, the electrodes in the lithium secondary battery of the present invention will be described. In general, a positive electrode or a negative electrode in a lithium secondary battery is formed of an electrode containing a positive electrode (negative electrode) active material, a binder resin (binder), a conductive material, a solvent, and the like on a current collector such as an aluminum foil or a copper foil. It is manufactured by applying and drying a paint for forming an active material layer.

As the active material used for the positive electrode in the present invention, compounds capable of inserting and extracting lithium ions include:
Examples of the inorganic compound include a transition metal oxide of a transition metal such as Fe, Co, Ni, and Mn, a composite oxide of lithium and a transition metal, and a transition metal sulfide. Specifically, Mn
Transition metal oxide powders such as O, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ ; composite oxide powders of lithium and transition metal such as lithium nickelate and lithium cobalt oxide; TiS ₂ , F
Transition metal sulfide powders such as eS are exemplified. Examples of the organic compound include a conductive polymer such as polyaniline. Further, these inorganic compounds and organic compounds may be mixed at an arbitrary ratio.

As the negative electrode active material, graphite or coke is used as a compound capable of inserting and extracting lithium ions in addition to the Li metal foil. Coke is particularly preferable from the viewpoint of safety. The particle size of the active material of the positive electrode and the negative electrode may be appropriately selected in consideration of other components of the battery, but is usually 1 to 30 μm in average particle size, particularly 1 to 10 μm,
In particular, when the thickness is 3 to 8 μm, the surface roughness described in the claims can be easily obtained. Further, it is preferable because the porosity can be easily controlled.

The binder must be stable with respect to an electrolytic solution or the like, and is desired to have weather resistance, chemical resistance, heat resistance, flame retardancy, and the like. Further, a material having excellent ion conductivity is desirable, and examples thereof include a cross-linkable polyethylene oxide resin. More preferably, those obtained by introducing an acryl group, a methacryl group, or the like into the terminal of the polyethylene oxide resin and cross-linking by heat, ultraviolet light, or the like are preferable.

The conductive substance is not particularly limited as long as it can impart conductivity by mixing an appropriate amount of compound powder with a compound powder capable of inserting and extracting lithium, but carbon powder such as acetylene black, carbon black, and graphite; Metal powders that are stable at the electrode potential to be used are exemplified. The DBP oil absorption of these conductive substances is 100 to 500 cc / 100 g,
Particularly, 150 to 300 cc / 100 g is preferable. The average particle size is 1 to 100 [nm], particularly 10 to 50 [nm].
Is preferred. The weight ratio between the active material and the conductive material is 98 /
A range of 2 to 90/10 is preferred.

As the solvent of the coating material for forming the positive electrode, those which can disperse and dissolve the binder and easily dry are preferable. For example, acrylonitrile, dimethyl carbonate and the like can be mentioned. Generally, an aluminum foil is used as the current collector of the positive electrode. A copper foil is used as a current collector of the negative electrode. In these current collectors, it is preferable that the surface on which the active material layer is provided be roughened in advance, since the binding effect will be increased. Examples of the surface roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. Examples of the mechanical polishing method include a method of polishing the surface of the current collector with a polishing cloth paper having abrasive particles fixed thereon, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like.

The method for forming the positive electrode and the negative electrode on the current collector is not particularly limited, but it is preferable to use a coating method such as a converse coat, a squeeze coat, and a lip coat because of the high viscosity of the paint. . The thickness (average thickness) of each active material layer of the positive electrode and the negative electrode is usually 20 to 2 respectively.
It is about 00 μm. To control the surface roughness of the active material layer in the positive and negative electrodes, change the active material particle size, or apply and dry the active material layer forming paint on the substrate,
There are various methods of pressing the coating film and controlling the type and amount of the solvent of the paint. For example, after forming the positive and negative electrode active material layers on the current collector, the pressure is increased to 1 to 500.
0 [kg / cm ² ], preferably 1 to 1000 [kg / cm ² ]
cm ² ] at a temperature of room temperature to 200 ° C., preferably room temperature to 150 ° C., by applying pressure with a calender.

Next, the polymer electrolyte will be described.
The polymer electrolyte may itself constitute an electrolyte, or may contain an electrolyte solution in a gel polymer, but in the latter case, it is generally contained in a gel polymer. The electrolytic solution to be used is preferably a non-aqueous electrolytic solution, which is generally obtained by dissolving an electrolyte in a non-aqueous solvent.

As the electrolyte used for preparing the polymer electrolyte, the electrolyte is stable with respect to the positive electrode active material and the negative electrode active material, and transfers lithium ions for performing an electrochemical reaction with the positive electrode active material or the negative electrode active material. Anything that can be performed can be used. LiPF ₆ in particular, LiAsF _6, LiSbF
₆ , LiBF ₄ , LiClO ₄ , LiI, LiBr, L
iCl, LiAlCl, LiHF ₂ , LiSCN, Li
SO ₃ CF _{2 and the} like. Among these, L
iPF ₆ and LiClO ₄ are preferred.

The content of these electrolytes in the electrolyte is as follows:
Generally, it is 0.5 to 2.5 mol / l. The solvent for dissolving the electrolyte is not particularly limited, but a solvent having a relatively high dielectric constant is preferably used. Specifically, ethylene carbonate, cyclic carbonates such as propylene carbonate, dimethyl carbonate, diethyl carbonate, non-cyclic carbonates such as ethyl methyl carbonate,
Tetrahydrofuran, 2-methyltetrahydrofuran,
Examples include ethers such as dimethoxyethane, lactones such as γ-butyl lactone, sulfur compounds such as sulfolane, and nitriles such as acetonitrile. In addition, these 2
Species or more may be mixed and used in an arbitrary ratio. Among these, ethylene carbonate, cyclic carbonates such as propylene carbonate, dimethyl carbonate, diethyl carbonate, and a mixture of two or more kinds of arbitrary ratios selected from an acyclic carbonate such as ethyl methyl carbonate are preferable. .

The polymer electrolyte is prepared by impregnating the electrolyte solution with a gel-forming polymer, for example, a polymer such as polyethylene oxide, polypropylene oxide, a crosslinked isocyanate of polyethylene oxide, phenylene oxide, or a phenylene sulfide polymer. Create If necessary, a compound having a polymerizable functional group such as an acrylic group is mixed with the electrolyte solution,
A polymer electrolyte may be obtained by irradiating an energy ray such as V and polymerizing the mixture, or by polymerizing the mixture by heat. The content of the electrolyte in the electrolyte solution is generally 0.5 to 2.
5 mol / l. The strength of the polymer constituting the gel in this case was as follows: pin piercing strength <1 mmφ0.5
As the spherical contact pressure test for r, a test of about 1 to 50 g · F is usually used. In addition, a nonwoven fabric or a porous film may be used in combination as a reinforcing material. In this case, the pin piercing strength is about 100 to 500 g · F.

The viscosity of the coating material for forming the polymer electrolyte layer is preferably 10,000 cp or less, depending on the coating method and the coating material. Within this range, the electrolyte can easily penetrate into the unevenness of the active material layer surfaces of the positive and negative electrodes, so that the surface roughness of the electrolyte layer and the interface roughness with the positive and negative electrode layers are The size is obtained by reversely copying the surface roughness of the negative electrode layer. That is, Rp, R on the surface of the active material layer
The v value is the R of the surface of the polymer electrolyte layer in contact with this surface.
v and Rp are preferable. On the other hand, when the viscosity of the electrolyte solution is higher than 100000 cp, the positive and negative electrode active material layers may not easily conform to the irregularities on the surface.

As described above, the feature of the present invention is that, in a lithium secondary battery using a polymer electrolyte, the surface of the active material layer of the positive and negative electrodes and the surface of the polymer electrolyte layer are set to a specific range, whereby the cycle characteristics and the external pressure are reduced. It is possible to provide a thin-film secondary battery such as a card type which is resistant to deformation such as bending. Hereinafter, the present invention will be described specifically.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention. Example 1 A coating material for a positive electrode was prepared according to the composition shown below, and applied to an aluminum substrate to evaluate a positive electrode for a lithium secondary battery. The following materials were used as the raw materials for the positive electrode paint.

Cathode active material LiCoO ₂ Average particle size: 5 μm (manufactured by FMC) Conductive material Acetylene black Average particle size: 40 nm (manufactured by Denki Kagaku Kogyo) Binder Photomer 4050 (manufactured by Henkel) Solvent DMC: dimethyl carbonate (Mitsubishi Chemical) Crosslinking initiator Trignox42 (Akuzo Nobel)

After weighing the above positive electrode material at the following ratio,
The mixture was kneaded and dispersed to obtain a paint. LiCoO ₂ 59.0% by weight Acetylene black 8.0% by weight Photomer 4050 8.0% by weight Trignox 0.1% by weight PC 24.9% by weight

This paint was applied on a 20 μm-thick aluminum foil using a doctor blade so that the film thickness became 150 μm. Next, pressing was performed so that the pressing pressure became 10 kgf / cm ^2, and crosslinking was performed at 120 ° C. to obtain a sheet on which the electrode material was applied.

Next, a negative electrode paint was prepared according to the following composition and applied to a steel substrate to evaluate a positive electrode for a Li battery. The following were used as raw materials for the negative electrode paint. Material for negative electrode active material Artificial graphite powder KS6 Average particle size: 5 μm (manufactured by LONZA) Binder Photomer 4050 (manufactured by Henkel) Solvent DMC: dimethyl carbonate (Mitsubishi Chemical) PC: propylene carbonate (Mitsubishi Chemical) EC: ethylene carbonate (Mitsubishi Chemical) Crosslinking initiator Trignox42 (Akuzo Nobel)

After weighing the above negative electrode material at the following ratio,
The mixture was kneaded and dispersed to obtain a paint. KS6 45.0 wt% Photomer 4050 10.9 wt% Trignox42 0.1 wt% PC 22.0 wt% EC 22.0 wt%

This paint was applied on a copper foil having a thickness of 20 μm using a doctor blade so that the film thickness became 150 μm. Next, pressing was performed so that the pressing pressure became 10 kgf / cm ^2, and crosslinking was performed at 120 ° C. to obtain a sheet on which the electrode material was applied. Next, a polymer electrolyte was prepared according to the following composition. The following materials were used. Acrylic monomer Photomer 4050 (manufactured by Henkel) Photomer 4158 (manufactured by Henkel) Polymer Polyethylene oxide (molecular weight: 4,000,000: Wako Pure Chemical) Solvent PC: propylene carbonate (Mitsubishi Chemical) Lithium salt LiClO ₄ (Wako Pure Chemical) Crosslinking initiator Darocure 1173 (Ciba) -Geigy)

The above-mentioned materials were weighed at the following ratios and dissolved by stirring to obtain a polymer electrolyte solution. Photomer 4050 6.0 wt% Photomer 4158 4.0 wt% Polyethylene oxide 0.5 wt% PC 79.0 wt% LiClO ₄ 10.0 wt% Darocure 1173 0.5 wt%

When the viscosity of this solution was measured using a B-type viscometer, it was 200 cp. Next, this solution was applied on the negative electrode active material layer applied on the copper base material using a doctor blade so that the film thickness (d) became 50 μm.
Ultraviolet irradiation was performed at 00 J / cm ² to obtain a polymer electrolyte layer. In addition, the pin piercing strength of the polymer constituting this polymer electrolyte layer was 20 g · f. The positive electrode was placed on the opposite side of the negative electrode with the polymer electrolyte layer, the electrodes were attached, and the resultant was sealed under reduced pressure in an aluminum-deposited polyethylene bag to obtain a lithium secondary battery. When the cross section of the polymer electrolyte layer was observed, the polymer electrolyte was almost positive, and the surface of the active material layer of the negative electrode was impregnated with irregularities, and the cross section was observed with a scanning electron microscope to obtain a roughness curve. The active material layer has an Rp value of 10 μm and an Rv value of 6
μm, the Rp value of the active material layer on the negative electrode side was 12 μm, and the Rv value was 9 μm. Therefore, Rp / d is 0.
2, 0.24 on the negative electrode side.

When five lithium secondary batteries were subjected to a charge / discharge test, all of them exhibited good battery characteristics without any internal short circuit, and the number of cycles at which the capacity became 80% or less of the initial capacity was defined as life. The cycle life was 53 times. The battery was bent at a curvature of 100 mmR, but no separation between the polymer electrolyte and the active material layer was observed, indicating good adhesion. And for this lithium secondary battery,
A load of 5 kg / cm ² was applied, but there was no internal short circuit and no special effect on the battery.

Example 2 A lithium secondary battery was manufactured in the same manner as in Example 1 except that the press pressure at the time of manufacturing the negative electrode was set to 20 kgf / cm ² . When the surface roughness of the positive and negative electrode active material layers was determined from the cross section of the polymer battery in the same manner as in Example 1, the Rp value on the positive electrode side was 1
0 μm, Rv value is 6 μm, Rp value on the negative electrode side is 5 μm, R
The v value was 7 μm. Therefore, Rp / d was 0.2 on the positive electrode side and 0.1 on the negative electrode side. When five of the obtained batteries were subjected to a charge / discharge test, the cycle life of all of the obtained batteries was 58 times, showing good characteristics.
Showed good adhesiveness to withstand the bending test. After the subsequent 5 kg / cm ² load test, the characteristics did not change.

Comparative Example 1 A lithium secondary battery sample was manufactured in the same manner as in Example 1 except that the negative electrode layer was formed without performing a press treatment when the negative electrode was manufactured. When the surface roughness of the positive and negative electrode active material layers was determined from the cross section of the polymer battery in the same manner as in Example 1, the Rp value on the positive electrode side was 10 μm, the Rv value was 6 μm, the Rp value on the negative electrode side was 37 μm, and the Rv value was 25 μm. Met. Therefore, Rp / d was 0.2 on the positive electrode side and 0.74 on the negative electrode side. When a charge / discharge test was performed on five of the obtained batteries, one of the five batteries was short-circuited at a voltage of 1 V or less and two were short-circuited at a voltage of 3.8 V or more. When the battery short-circuited at 1 V or less was disassembled and observed, the fine powder which seemed to have chipped off was present in a form free from the surface of the active material. Also,
When the battery short-circuited at 3.8 V or more was disassembled and observed, lithium dendrite was locally generated and reached the positive electrode surface. The remaining two batteries were subjected to repeated charge / discharge tests. The cycle life was 12 times on average, and an internal short circuit was caused by a load test of 5 kg / cm ² .

Comparative Example 2 Example 1 was repeated except that the pressing pressure at the time of producing the negative electrode was 5 kg.
In the same manner as described above, a lithium secondary battery was produced. Example 1
Similarly, when the surface roughness of the positive and negative electrode active material layers was determined from the cross section of the polymer battery, the Rp value of the positive electrode layer was 10 μm and Rv
The value was 6 μm, the Rp value of the negative electrode layer was 25 μm, and the Rv value was 25 μm.
μm. Therefore, Rp / d is 0.
2. The negative electrode layer was 0.5. When five of the obtained batteries were subjected to a charge / discharge test, two of the five batteries were short-circuited at a voltage of 3.8 V or more. When the charge / discharge test was repeatedly performed on the three batteries that were normally charged, the cycle life was 20 times on average.

Comparative Example 3 A lithium secondary battery was produced in the same manner as in Example 1 except that the press pressure at the time of producing the negative electrode was 7 kgf / cm ² . When the surface roughness of the positive and negative electrode active material layers was determined from the cross section of the polymer battery in the same manner as in Example 1, the Rp value of the positive electrode layer was 1
0 μm, Rv value is 6 μm, Rp value of the negative electrode layer is 22 μm,
The Rv value was 25 μm. Therefore, Rp / d is
The positive electrode layer was 0.2 and the negative electrode layer was 0.44. When five of the obtained batteries were subjected to a charge / discharge test, two of the five batteries were short-circuited at a voltage of 3.8 V or more. When the charge and discharge test was repeatedly performed on the three batteries that were normally charged in the initial stage, the cycle life was 35 times on average.

Comparative Example 4 A lithium secondary battery was produced in the same manner as in Example 1 except that the press pressure at the time of producing the negative electrode was 100 kgf / cm ² . When the surface roughness of the positive and negative electrode active material layers was determined from the cross section of the polymer battery in the same manner as in Example 1, the Rp value of the positive electrode layer was 1 μm, the Rv value was 2 μm, and the Rp value of the negative electrode layer was 0.05 μm.
m and Rv values were 0.07 μm. When five of the obtained batteries were subjected to a charge / discharge test, initial charging was normally performed for all five batteries. However, when a bending test of 100 mmR was performed, peeling at the electrolyte / negative electrode interface was observed,
The surface adhesion was poor.

[0041]

The lithium secondary battery of the present invention is excellent in product yield and cycle characteristics, and can withstand external pressure and bending.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01M 10/38 H01M 10/38

Claims (19)

[Claims] 1. A lithium secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and a polymer electrolyte, wherein the positive electrode and the negative electrode collect an active material layer containing a compound capable of inserting and extracting lithium ions. An Rp value (average line height) on the surface of the active material layer is 0.1 μm to 20 μm.
m, a lithium secondary battery. 2. The Rv value (average line depth) of the active material layer surface is 0.1 μm to 50 μm.
4. The lithium secondary battery according to 1. 3. The lithium secondary battery according to claim 1, wherein an Rp value of a contact surface of the polymer electrolyte layer with the active material layer is 0.1 μm to 50 μm. 4. The lithium secondary battery according to claim 3, wherein the polymer electrolyte layer has an Rv value of 0.1 μm to 20 μm at a contact surface with the active material layer. 5. The method according to claim 1, wherein, when an average thickness of the electrolyte layer is d, an Rp value / d on the surface of the active material layer is 0.3 or less. The lithium secondary battery according to the above. 6. The lithium secondary battery according to claim 5, wherein Rp / d is 0.3 or less for both the positive and negative electrode active material layers. 7. The method according to claim 1, wherein the thickness of the polymer electrolyte layer is 50 μm or less.
The lithium secondary battery according to any one of the above. 8. The Rp value of the active material layer surface is 1 to 10 μm
The lithium secondary battery according to claim 1, wherein: 9. The lithium secondary battery according to claim 6, wherein Rp / d is 0.3 to 0.002. 10. A positive electrode active material comprising: a transition metal oxide;
The lithium secondary battery according to any one of claims 1 to 9, wherein the lithium secondary battery is selected from the group consisting of a composite oxide of lithium and a transition metal, a transition metal sulfide, and a conductive polymer. 11. The lithium secondary battery according to claim 1, wherein the negative electrode active material is selected from lithium metal, graphite and coke. 12. The lithium secondary battery according to claim 10, wherein the active material is composed of particles having an average particle size of 1 to 30 μm. 13. The lithium secondary battery according to claim 1, wherein the active material layer contains a binder component and / or a conductive material. 14. The lithium secondary battery according to claim 13, wherein the binder component is a crosslinkable polyethylene oxide resin or a derivative thereof. 15. The conductive substance is a carbonaceous powder or
The lithium secondary battery according to claim 13, wherein the lithium secondary battery is a metal powder. 16. The conductive material has an average particle size of 1 to 100.
The lithium secondary battery according to claim 15, wherein 17. The weight ratio between the active material and the conductive material is 9
14. The ratio is from 8/2 to 90/10.
17. The lithium secondary battery according to any one of items 16 to 16. 18. The lithium secondary battery according to claim 1, wherein the current collector is an aluminum foil or a copper foil. 19. An active material layer containing a compound capable of inserting and extracting lithium ions is provided on a current collector as a positive electrode and a negative electrode, and then at room temperature to 150 ° C. and 1 to 5000 kg / cm ^2.
After applying pressure by a calendering method at a pressure of, a lithium secondary battery is characterized in that a polymer electrolyte layer is provided and laminated on the active material layer, and the Rp of the active material layer surface is set to 0.1 to 20 μm. Production method.