KR100367751B1 - Nonaqueous electrolyte secondary battery and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a nonaqueous electrolyte secondary battery and a method for manufacturing the same. In the nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte is impregnated in the electrode group in a solution-liquid state, the thickness can be reduced, and the capacity, the large current characteristics, and the cycle performance can be achieved. An object of the present invention is to provide an improved nonaqueous electrolyte secondary battery, comprising an electrode group including a positive electrode, a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the nonaqueous electrolyte, and at least the positive electrode, the negative electrode, and the separator. The pores are each retained with an adhesive polymer having the same composition, and the anode, the cathode and the separator are bonded to each other.

Description

Non-aqueous electrolyte secondary battery and manufacturing method thereof {NONAQUEOUS ELECTROLYTE SECONDARY BATTERY AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a nonaqueous electrolyte secondary battery and a method for producing a nonaqueous electrolyte secondary battery.

At present, as a non-aqueous electrolyte secondary battery for portable devices such as a cellular phone, a thin lithium ion secondary battery is commercialized. In this battery, a porous membrane is used for lithium cobalt oxide (LiCoO ₂ ) in the positive electrode, a graphite material or a carbonaceous material in the negative electrode, an organic solvent in which lithium salt is dissolved in an electrolyte, and a separator.

Although it is desired to make the thickness of a battery thin with the thinning of a portable device, practical use of the thin lithium ion secondary battery of thickness 4mm or less is difficult. For this reason, conventionally, the card type lithium secondary battery which uses the polymer electrolyte is proposed, and the commercial development is progressing.

However, the lithium secondary battery using the polymer electrolyte has a problem that the electrode interface has a higher impedance and lower lithium ion conductivity than the lithium secondary battery using the nonaqueous electrolyte because it is a gel polymer in which the nonaqueous electrolyte is maintained in the polymer. In addition, when the thickness is made thin in order to increase the lithium ion mobility, the amount of the active material in the positive electrode group is reduced, resulting in a problem that the energy density is lowered.

Therefore, a lithium secondary battery using a polymer electrolyte has a problem in that volume energy density and large current characteristics are inferior to a thin lithium secondary battery in which a nonaqueous electrolyte is impregnated in a solution-liquid state.

On the other hand, the scope of the claims in Japanese Patent Application Laid-Open No. 10-177865 is made of a mixture of a positive electrode, a negative electrode, a separator having an opposite surface holding an electrolyte solution, an electrolyte solution, a polymer gel phase containing an electrolyte solution, and a polymer solid phase. A lithium ion secondary battery having an adhesive resin layer for joining the positive electrode and the negative electrode to the opposite side of is described. Further, in the scope of the claims of JP 10-189054 A, a process of forming each electrode formed on a positive electrode and a negative electrode current collector, and applying a binder resin solution obtained by dissolving a main component polyvinylidene fluoride in a solvent to a separator Manufacturing a lithium ion secondary battery comprising a step of forming a battery laminate by evaporating a solvent by drying each electrode in a state where the electrodes are stacked on and in close contact with the separator, and a step of impregnating an electrolyte solution in the battery laminate. The method is described.

However, in this lithium ion secondary battery, since the adhesive resin layer is sandwiched between the positive electrode and the separator, and between the negative electrode and the separator, there is a problem that the internal resistance is increased and the cycle life and the large current discharge characteristics are deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a nonaqueous electrolyte secondary battery in which a nonaqueous electrolyte secondary battery in which a nonaqueous electrolyte is impregnated in an electrode group in a solution-liquid state can be thinned, and the capacity, large current characteristics, and cycle performance are improved. I would like to.

In addition, an object of the present invention is to provide a nonaqueous electrolyte secondary battery in which a nonaqueous electrolyte is impregnated in an electrode group in a solution-liquid state. It is to provide a method of manufacturing a secondary battery.

1 is a cross-sectional view showing an example of a nonaqueous electrolyte secondary battery according to the present invention;

2 is an enlarged cross-sectional view showing part A of FIG. 1;

3 is a schematic diagram showing the vicinity of the boundary between the positive electrode layer, the separator and the negative electrode layer in the electrode group of the nonaqueous electrolyte secondary battery of FIG.

4 is a perspective view illustrating a nonaqueous electrolyte secondary battery having a structure in which a set of a positive electrode, a negative electrode, and a separator are wound;

FIG. 5 is a perspective view illustrating a nonaqueous electrolyte secondary battery having a structure in which a set of a positive electrode, a negative electrode, and a separator are wound or folded.

* Explanation of symbols for the main parts of the drawings

1: exterior material 2: electrode group

3,42,52: Separator 4: Anode layer

5: anode collector 6: cathode layer

7: negative electrode current collector 8: adhesive part

9: adhesive polymer 10: anode lead

11: Cathode lead 41, 51: Anode

43,53: cathode

The present invention includes an electrode group and a non-aqueous electrolyte having a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode,

A polymer having adhesiveness is retained in at least the pores of the positive electrode, the negative electrode, and the separator, and the positive electrode, the negative electrode, and the separator are bonded to each other to form a nonaqueous electrolyte secondary battery.

In addition, the present invention is a step of manufacturing an electrode group by sandwiching a separator between the positive electrode and the negative electrode,

Impregnating the electrode group with a solution in which an adhesive polymer is dissolved,

Drying and molding the electrode group; and

It is a manufacturing method of the nonaqueous electrolyte secondary battery characterized by including the process of impregnating a nonaqueous electrolyte solution to the said electrode group.

In addition, the present invention includes an electrode group having a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode and a non-aqueous electrolyte

At least the pores of the positive electrode, the negative electrode and the separator are each maintained with an adhesive polymer, the positive electrode, the negative electrode and the separator are bonded and integrated, and the electrode group is the positive electrode, the negative electrode and the separator is wound or It is a nonaqueous electrolyte secondary battery characterized by being bent and folded.

Hereinafter, a nonaqueous electrolyte secondary battery (for example, a thin lithium ion secondary battery) according to the present invention will be described in detail with reference to FIGS. 1, 2, 4, and 5.

1 is a cross-sectional view showing a nonaqueous electrolyte secondary battery (for example, a thin lithium ion secondary battery) according to the present invention, FIG. 2 is an enlarged view showing part A of FIG. 1, and FIG. 3 is a view of an anode layer, a separator, and a cathode layer. It is a schematic diagram showing the vicinity of the boundary.

4 is a perspective view showing a nonaqueous electrolyte secondary battery having a structure in which a positive electrode, a negative electrode, and a separator are wound.

5 is a perspective view illustrating a nonaqueous electrolyte secondary battery having a structure in which a positive electrode, a negative electrode, and a separator are wound or folded.

As shown in FIG. 1, the packaging material 1 made of, for example, a laminate film surrounds the electrode group 2. The electrode group 2 has a structure in which a laminate composed of an anode, a separator, and a cathode is wound in a flat shape. As shown in FIG. 2, the laminate includes a separator 3, a positive electrode layer 4, a positive electrode current collector 5, a positive electrode layer 4, a separator 3, a negative electrode layer 6, and a negative electrode current collector ( 7), negative electrode layer 6, separator 3, positive electrode layer 4, positive electrode current collector 5, positive electrode layer 4, separator 3, negative electrode layer 6, and negative electrode current collector 7 ) Is laminated in this order.

The negative electrode current collector 7 is located on the outermost layer of the electrode group 2. The adhesion part 8 exists in the surface of the said electrode group 2. The inner surface of the packaging material 1 is adhered to the bonding part 8. As shown in FIG. 3, the adhesive polymers 9 are held in the pores of the anode layer 4, the separator 3, and the cathode layer 6 throughout the electrode group 2. As a result, the electrode group is integrated and fixed. It is preferable that a polymer having adhesiveness of the same component is used for both the anode layer, the separator, and the cathode layer. Thereby, the electrode group can be more firmly integrated. The nonaqueous electrolyte is impregnated with the electrode group 2 in the packaging material 1. One end of the strip-shaped positive electrode lead 10 is connected to the positive electrode current collector 5 of the electrode group 2, and the other end thereof extends from the exterior member 1. On the other hand, one end of the strip-shaped negative electrode lead 11 is connected to the negative electrode current collector 7 of the electrode group 2, and the other end thereof extends from the exterior member 1.

In addition, the nonaqueous electrolyte secondary battery of the present invention may have an electrode group in which a stack of a set of the positive electrode 41, the negative electrode 43, and the separator 42 is wound as shown in FIG. 4. In addition, as shown in FIG. 5, a stack of a set of the positive electrode 51, the negative electrode 53, and the separator 52 may be folded to have an electrode group formed by bending. Thereby, manufacture of an electrode group becomes easy and an electrode group with strong mechanical strength is obtained. The area of the cathode 43 is preferably larger than the area of the anode 41. With such a configuration, the cathode end is formed to extend from the anode end, but current concentration to the cathode end is suppressed, thereby improving cycle performance and stability.

In addition, it is preferable that the short side of a separator extends 0.25 mm-2 mm from the short side of the strip | belt-shaped electrode of a cathode, and the polymer which has adhesiveness which concerns on this invention exists in the extended separator part. As a result, the strength of the extension of the separator is increased, and short circuits between the positive and negative electrodes are less likely to occur even when an impact is applied to the battery. In addition, even when the battery is present under high temperature conditions (100 ° C or more), shrinkage of the separator is less likely to occur, and short circuits between the positive and negative electrodes can be prevented, thereby improving safety.

Next, the positive electrode, the negative electrode, the separator 3, the adhesive layer 8, the adhesive polymer 9, the non-aqueous electrolyte and the packaging material 1 will be described in detail.

1) anode

This positive electrode has a structure in which the positive electrode layer 4 containing the active material is supported on one side or both sides of the current collector 5. The anode holds the polymer 9 having adhesion to the voids.

The anode layer includes a cathode active material and a conductive agent. The positive electrode layer may further include a binder for binding the positive electrode active material separately from the polymer 9 having adhesiveness.

As the positive electrode active material, various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt compound, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, vanadium oxide containing titanium, titanium disulfide, and disulfide And chalcogen compounds such as molybdenum. Among them, when lithium-containing cobalt oxide (for example, LiCoO ₂ ), lithium-containing nickel cobalt oxide (for example, LiNi _0.8 Co _0.2 O ₂ ), and lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO ₂ ) are used It is preferable because a high voltage is obtained.

As said conductive agent, acetylene black, carbon black, graphite, etc. are mentioned, for example.

As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene propylene diene copolymer (EPDM), styrene butadiene rubber (SBR) and the like can be used.

The blending ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

As the current collector, a conductive substrate having a porous structure or a conductive substrate without holes can be used. This conductive substrate can be formed, for example, of aluminum, stainless steel or nickel.

Among them, it is preferable to use a conductive substrate having a two-dimensional porous structure in which a hole having a diameter of 3 mm or less exists in a ratio of one or more per 10 cm 2. That is, when the diameter of the hole opened in the conductive substrate is larger than 3 mm, there is a fear that sufficient anode strength cannot be obtained. On the other hand, when the ratio of the hole having a diameter of 3 mm or less is smaller than the above range, it is difficult to uniformly infiltrate the nonaqueous electrolyte into the electrode group, and thus there is a fear that a sufficient cycle life cannot be obtained. The diameter of the hole is more preferably in the range of 0.1 to 1 mm. In addition, the abundance ratio of the holes is more preferably in the range of 10 to 20 pieces per 10 cm 2.

It is preferable that the conductive substrate having a two-dimensional porous structure in which the above-described holes having a diameter of 3 mm or less exist in one or more ratios per 10 cm 2 has a thickness in the range of 15 to 100 µm. When thickness is less than 15 micrometers, there exists a possibility that sufficient anode strength may not be obtained. On the other hand, when thickness exceeds 100 micrometers, battery weight and electrode group thickness increase, and there exists a possibility that it may become difficult to make the weight energy density and volume energy density of a thin secondary battery sufficiently high. The more preferable range of thickness is 30-80 micrometers.

It is preferable that the polymer which has the said adhesiveness can maintain high adhesiveness in the state which hold | maintained the nonaqueous electrolyte solution. Moreover, such a polymer is more preferable if it has high lithium ion conductivity. Specifically, polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), polyethylene oxide (PEO), etc. are mentioned. In particular, polyvinylidene fluoride is preferable. The polyvinylidene fluoride can maintain the nonaqueous electrolyte, and the inclusion of the nonaqueous electrolyte causes some gelation, thereby further improving the ion conductivity in the positive electrode.

It is preferable that the adhesive polymer has a porous structure in the pores of the positive electrode. An adhesive polymer having a porous structure can hold a nonaqueous electrolyte.

2) cathode

The negative electrode has a structure in which the negative electrode layer 6 is held on one side or both sides of the current collector 7. The negative electrode retains the polymer having adhesion to the pores.

The negative electrode layer includes a carbon material that occludes and releases lithium ions. The negative electrode layer may further include a binder for binding the negative electrode material separately from the polymer 9 having the adhesive property.

Examples of the carbon material include graphite materials such as graphite, coke, carbon fiber, spherical carbon or carbonaceous material, thermosetting resin, isotropic pitch, mesophase pitch, mesophase pitch-based carbon fiber, mesophase globules, and the like (in particular, mesophase Pitch-type carbon fiber is preferable), The graphite material obtained by heat-processing at 500-3000 degreeC, a carbonaceous material, etc. are mentioned. Among them, it is preferable that is obtained and, using the graphite material is a (002) plane of the plane interval (d ₀₀₂₎ having a graphite crystal 0.340㎚ or less by setting the temperature of the heat treatment above 2000 ℃. A nonaqueous electrolyte secondary battery having a negative electrode containing such a graphite material as a carbon material can significantly improve battery capacity and large current characteristics. More preferably, the surface spacing d ₀₀₂ is 0.336 nm or less.

As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene propylene diene copolymer (EPDM), styrenebutadiene rubber (SBR), carboxymethyl cellulose (CMC) and the like can be used. have.

The blending ratio of the carbon material and the binder is preferably in the range of 90 to 98% by weight of the carbon material, 2 to 20% by weight of the binder. In particular, the carbon material is preferably in the range of 5 to 20 g / m 2 in the state of producing a negative electrode.

As the current collector, a porous conductive substrate or a conductive substrate without holes can be used. This conductive substrate can be formed of copper, stainless steel or nickel, for example.

Among them, it is preferable to use a conductive substrate having a two-dimensional porous structure in which a hole having a diameter of 3 mm or less exists in a ratio of one or more per 10 cm 2. That is, when the diameter of the hole of a conductive substrate becomes larger than 3 mm, there exists a possibility that sufficient cathode strength may not be obtained. On the other hand, if the abundance ratio of the holes having a diameter of 3 mm or less is smaller than the above range, it is difficult to uniformly infiltrate the nonaqueous electrolyte into the electrode group, so that there is a fear that a sufficient cycle life cannot be obtained. It is preferable to make the diameter of a hole into the range of 0.1-1 mm. In addition, the abundance ratio of the holes is more preferably in the range of 10 to 20 pieces per 10 cm 2.

It is preferable that the conductive substrate having a two-dimensional porous structure in which the above-described holes having a diameter of 3 mm or less exist in one or more ratios per 10 cm 2 has a thickness in the range of 10 to 50 m. If the thickness is less than 10 mu m, there is a fear that sufficient negative electrode strength cannot be obtained. On the other hand, when thickness exceeds 50 micrometers, battery weight and electrode group thickness increase, and there exists a possibility that it may become difficult to make the weight energy density and volume energy density of a thin secondary battery sufficiently high.

It is preferable that the polymer which has the said adhesiveness can maintain high adhesiveness in the state which hold | maintained the nonaqueous electrolyte solution. Moreover, such a polymer is more preferable if it has high lithium ion conductivity. Specifically, the same thing as the thing described with the positive electrode mentioned above can be mentioned. PVdF is particularly preferred.

The adhesive polymer is preferably present in the form of a porous structure in the pores of the negative electrode. An adhesive polymer having a porous structure can hold a nonaqueous electrolyte.

As the negative electrode, in addition to the carbon material containing the above-described lithium ions, the one containing a metal oxide, a metal sulfide or a metal nitride, or a metal made of lithium metal or lithium alloy can be used.

Examples of the metal oxides include tin oxides, silicon oxides, lithium titanium oxides, niobium oxides, tungsten oxides, and the like.

Examples of the metal sulfides include tin sulfides and titanium sulfides.

As said metal nitride, lithium cobalt nitride, lithium iron nitride, lithium manganese nitride, etc. are mentioned, for example.

Examples of the lithium alloys include lithium aluminum alloys, lithium tin alloys, lithium zinc alloys, and lithium silicon alloys.

3) separator

The separator is formed by maintaining a polymer having adhesion to the pores of the porous sheet.

As the porous sheet, for example, a porous film containing polyethylene, polypropylene or PVdF, a nonwoven fabric made of synthetic resin, or the like can be used. Among them, a porous film made of polyethylene, polypropylene, or both is preferable because it can improve the safety of the secondary battery.

It is preferable that the polymer which has the said adhesiveness can maintain high adhesiveness in the state which hold | maintained the nonaqueous electrolyte solution. Moreover, such a polymer is more preferable if lithium ion conductivity is high. Specifically, the same thing as the thing described with the positive electrode mentioned above can be mentioned. In particular, PVdF is preferred.

The adhesive polymer is preferably present in the form of a porous structure in the pores of the separator. An adhesive polymer having a porous structure can hold a nonaqueous electrolyte.

It is preferable that the thickness of the said porous sheet shall be 30 micrometers or less. If the thickness exceeds 30 μm, the distance between the positive electrode and the negative electrode increases, which may increase the internal resistance. In addition, it is preferable that the lower limit of thickness shall be 5 micrometers. If the thickness is less than 5 µm, the strength of the separator is significantly lowered, and there is a possibility that internal shorting is likely to occur. As for the upper limit of thickness, it is more preferable to set it as 25 micrometers, and it is more preferable to set it as 10 micrometers.

It is preferable that the heat shrinkage in 120 degreeC and 1 hour of the said porous sheet is 20% or less. If the heat shrinkage exceeds 20%, it may be difficult to make sufficient adhesive strength of the positive electrode, the negative electrode, and the separator. As for the said thermal contraction rate, it is more preferable to set it as 15% or less.

It is preferable that the said porous sheet has a porosity of 30 to 60% of range. This is for the following reason. If the porosity is less than 30%, it is difficult to obtain high electrolyte retention in the separator. On the other hand, when the porosity exceeds 60%, there is a fear that sufficient separator strength cannot be obtained. The more preferable range of porosity is 35 to 50%.

The porous sheet preferably has an air transmittance of 600 seconds / 100 cm 3 or less. If the air permeability exceeds 600 seconds / 100 cm 3, it is difficult to obtain high lithium ion mobility in the separator. The lower limit of the air permeability is preferably 100 seconds / 100 cm 3. This is because if the air permeability is less than 100 seconds / 100 cm 3, sufficient separator strength may not be obtained. The upper limit of the air permeability is more preferably 500 seconds / 100 cm 3, and the lower limit is more preferably 150 seconds / 100 cm 3.

4) Non-aqueous electrolyte

The nonaqueous electrolyte is a liquid electrolyte prepared by dissolving an electrolyte in a nonaqueous solvent.

As the non-aqueous solvent, a known non-aqueous solvent can be used as a solvent of a lithium secondary battery, and is not particularly limited, but the propylene carbonate (PC), ethylene carbonate (EC), and the viscosity of the donor number 18 are lower than those of the PC and EC. It is preferable to use the non-aqueous solvent which mainly uses the mixed solvent of the 1 or more types of non-aqueous solvents (henceforth 2nd solvent) which are the following.

As the second type of solvent, for example, a chain carbonate is preferable, and among these, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, and γ-butyrolactone (γ-BL), acetonitrile (AN), ethyl acetate (EA), toluene, xylene, methyl acetate (MA), and the like. These second solvents can be used individually or in the form of a mixture of 2 or more types. In particular, as for the said 2nd solvent, it is more preferable that donor number is 16.5 or less.

It is preferable that the viscosity of the said 2nd solvent is 28mp or less at 25 degreeC. It is preferable that the compounding quantity of the said ethylene carbonate or propylene carbonate in the said mixed solvent is 10 to 80% by volume ratio. The more preferable compounding quantity of the said ethylene carbonate or propylene carbonate is 20 to 75% by volume ratio.

More preferred composition of the mixed solvent is EC and MEC, EC and PC and MEC, EC and MEC and DEC, EC and MEC and DMC, EC and MEC and PC and DEC mixed solvent, the volume ratio of the MEC is 30 to 80 It is preferable to set it as%. More preferable volume ratio of MEC is 40 to 70% of range.

Examples of the electrolyte contained in the nonaqueous electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoride (LiAsF ₆ ), and trifluoromethasulfonic acid. And lithium salts (electrolytes) such as lithium (LiCF ₃ SO ₃ ) and bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ]. Especially, it is preferable to use LiPF ₆ and LiBF ₄ .

The amount of the electrolyte dissolved in the nonaqueous solvent is preferably 0.5 to 2.0 mol / l.

The amount of the nonaqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh of battery unit capacity. This is for the following reason. If the amount of nonaqueous electrolyte is less than 0.2 g / 100 mAh, there is a possibility that the ionic conductivity of the positive electrode and the negative electrode cannot be sufficiently maintained. On the other hand, when the amount of the non-aqueous electrolyte exceeds 0.6g / 100 mAh, the amount of the electrolyte may be large, which may make it difficult to seal with the film-like packaging material. The more preferable range of the amount of nonaqueous electrolyte is 0.4 to 0.55 g / 100 mAh.

5) Adhesive Part (8)

This bonding part 8 exists in the surface of the said electrode group 2, and bonds and integrates an exterior material and an electrode group. Thereby, deformation by the gas generation of a battery can be reduced.

The adhesive part may be mainly formed of an adhesive polymer.

It is preferable that the polymer which has the said adhesiveness can maintain high adhesiveness in the state which hold | maintained the nonaqueous electrolyte solution. Moreover, such a polymer is more preferable if it has high lithium ion conductivity. Specifically, the same thing as the thing described with the positive electrode mentioned above can be mentioned. In particular, PVdF is preferred.

The bonding portion may have a porous structure. The porous adhesive portion can hold the nonaqueous electrolyte in the voids.

The total amount of the adhesive polymer contained in the battery is preferably 0.2 to 6 mg per 100 mAh of battery capacity. This is for the following reason. If the total amount of the adhesive polymer is less than 0.2 mg per 100 mAh of battery capacity, it may be difficult to sufficiently improve the adhesion between the positive electrode, the separator, and the negative electrode. On the other hand, if the total amount exceeds 6 mg per 100 mAh of battery capacity, there is a risk of lowering the lithium ion conductivity of the secondary battery or increasing the internal resistance, and improving the discharge capacity, the large current discharge characteristics, and the charge / discharge cycle lifespan. It may be difficult. The more preferable range of the total amount of the polymer having an adhesive is 0.5 to 3 mg per 100 mAh of battery capacity.

In addition, although the adhesion part 8 was formed in the whole surface of the electrode group 2 in FIG. 1 mentioned above, you may form the adhesion part 8 in a part of electrode group 2. When forming the adhesion part 8 in a part of electrode group 2, it is preferable to form in the surface corresponded to the outermost periphery of an electrode group at least. In addition, the adhesion part 8 may not be provided.

6) Exterior materials (1)

As the exterior member 1, for example, a thin film made of a synthetic resin or a metal having flexibility can be used. In particular, in the case of a non-aqueous electrolyte battery, a multilayer film in which a barrier layer such as aluminum is inserted into a layer made of synthetic resin is preferable. The inclusion of the aluminum layer is particularly preferable in the case of the nonaqueous electrolyte battery, since it is possible to prevent the incorporation of moisture into the electrolyte, which makes it possible to prolong the battery life.

It is preferable that the thickness of the said exterior material exists in the range of 50-300 micrometers. If it is too thin, it will become easy to deform and break, and if too thick, the effect of thinning will become small.

Hereinafter, a method for manufacturing a nonaqueous electrolyte secondary battery according to the present invention will be described.

(First process)

An electrode group is produced between a positive electrode and a negative electrode by inserting a porous sheet as a separator.

The positive electrode is produced by, for example, suspending a conductive agent and a binder in a positive electrode active material with a suitable solvent, applying the suspension to a current collector, drying, and forming a thin plate. Examples of the positive electrode active material, the conductive agent, the binder, and the current collector include the same ones described in the above (1) positive electrode column.

The negative electrode is, for example, kneaded carbonaceous material and a binder that occludes and releases lithium ions in the presence of a solvent, apply the obtained suspension to the current collector, and after drying, press once or at a predetermined pressure 2-5 It is produced by presses in multiple stages.

Examples of the carbon material, the binder, and the current collector include the same ones described in the section of (2) the negative electrode described above.

As a porous sheet of the said separator, the thing similar to what was demonstrated in the column of (3) separator mentioned above can be used.

(Second process)

The electrode group is housed in an encapsulated outer packaging material such that the laminated surface is visible from the opening. A solution obtained by dissolving an adhesive polymer in a solvent is injected into an electrode group in the packaging material, and the solution is impregnated with the electrode group.

As said exterior material, the thing similar to what was demonstrated in the column of said (6) exterior material mentioned above is mentioned.

Examples of the polymer having the adhesive property include the same as those described in the section of the above (1) anode. In particular, PVdF is preferred.

It is preferable to use the organic solvent whose boiling point is 200 degrees C or less for the said solvent. As such an organic solvent, dimethylformamide (boiling point of 153 degreeC) is mentioned, for example. When the boiling point of an organic solvent exceeds 200 degreeC, when drying temperature mentioned later is made into 100 degreeC or less, there exists a possibility that a drying time may take a long time. Moreover, it is preferable that the lower limit of the boiling point of an organic solvent shall be 50 degreeC. When the boiling point of an organic solvent is less than 50 degreeC, there exists a possibility that the said organic solvent may evaporate while injecting the said solution to an electrode group. The upper limit of the boiling point is more preferably 180 ° C., and the lower limit of the boiling point is more preferably 100 ° C.

The concentration of the adhesive polymer in the solution is preferably in the range of 0.1 to 2.5% by weight. This is for the following reason. If the concentration is less than 0.1% by weight, it may be difficult to bond the positive electrode, the negative electrode and the separator with sufficient strength. On the other hand, when the concentration exceeds 2.5% by weight, it is difficult to obtain a porosity sufficient to hold the nonaqueous electrolyte, which may significantly increase the interface impedance of the electrode. As the interface impedance increases, the capacity and the large current discharge characteristics are greatly reduced. The range with more preferable concentration is 0.5 to 1.5 weight%.

The injection amount of the solution is preferably in the range of 0.2 to 2 ml per 100 mAh of battery capacity when the concentration of the adhesive polymer in the solution is 0.1 to 2.5% by weight. This is for the following reason. If the injection amount is less than 0.2 ml, it is difficult to sufficiently increase the adhesion between the positive electrode, the negative electrode, and the separator. On the other hand, when the injection amount exceeds 2 ml, there is a possibility that the lithium ion conductivity of the secondary battery may decrease or the internal resistance may increase, and it may be difficult to improve the discharge capacity, the large current discharge characteristics, and the charge / discharge cycle life. . The more preferable range of the injection amount is 0.3 to 1 ml per 100 mAh of battery capacity.

(Third process)

Drying is carried out at atmospheric pressure or under reduced pressure including vacuum while press molding the electrode group to a predetermined thickness to evaporate the solvent in the solution, and maintain an adhesive polymer in the pores of the positive electrode, the negative electrode and the separator. The group is molded, integrated and fixed. In addition, the moisture contained in the electrode group can be simultaneously removed by the drying.

In addition, the porous adhesive portion allows to include a trace amount of solvent.

It is preferable to perform the said drying at 100 degrees C or less. This is for the following reason. When the temperature of drying exceeds 100 degreeC, there exists a possibility that the said separator may greatly heat shrink. When the heat shrink becomes large, the separator bends, making it difficult to firmly bond the positive electrode, the negative electrode, and the separator. In addition, the above-mentioned heat shrinkage is remarkably easy to occur when using a porous film containing polyethylene or polypropylene as a separator. The lower the drying temperature, the more the heat shrinkage of the separator can be suppressed. However, if the drying temperature is lower than 40 ° C., it is difficult to sufficiently evaporate the solvent. For this reason, as for drying temperature, it is more preferable to set it as 40-100 degreeC. In addition, drying is preferably performed under reduced pressure including a vacuum.

(Fourth process)

After injecting the nonaqueous electrolyte into the electrode group in the packaging material, a thin nonaqueous electrolyte secondary battery is manufactured by sealing the opening of the packaging material.

As said non-aqueous electrolyte, the same thing as mentioned above can be used.

In the above-described manufacturing method, the injection of the solution in which the adhesive polymer is dissolved is carried out after the electrode group is housed in the packaging material. In this case, first, a separator is sandwiched between an anode and a cathode to produce an electrode group. After impregnating the solution with the electrode group, the electrode group is dried under reduced pressure including atmospheric pressure or vacuum to evaporate the solvent of the solution and form a porous adhesive portion in the pores of the positive electrode, the negative electrode and the separator. . After storing such an electrode group in an exterior material, a nonaqueous electrolyte secondary battery can be manufactured by inject | pouring a nonaqueous electrolyte and sealing it by entrance.

In addition, the manufacturing method according to the present invention can produce a thin non-aqueous solvent secondary battery having the structure shown in Figure 1, 2 or 3, 4 described above.

According to the nonaqueous electrolyte secondary battery according to the present invention described above, the adhesive polymer can be maintained in at least the pores surrounded by the positive electrode and the separator, the pores surrounded by the negative electrode and the separator, and the respective pores in the positive electrode, the negative electrode and the separator, An adhesive polymer can be distributed in a three-dimensional network shape at least inside the electrode group. As a result, the positive electrode, the negative electrode and the separator can be integrated while the positive electrode is in direct contact with one side of the separator and the negative electrode is in direct contact with the other side, so that the adhesion between the positive electrode, the negative electrode and the separator is sufficient even when a film-like exterior material is used. In addition, it is possible to ensure a satisfactory quality and to suppress an increase in internal resistance due to the adhesive polymer. As a result, it is possible to provide a nonaqueous electrolyte secondary battery having improved capacity, large current characteristics, and cycle life. Moreover, since it becomes possible to use a film-form exterior material, it can realize a thin nonaqueous electrolyte secondary battery which is thin, for example, 4 mm or less, and excellent in capacity, a large current characteristic, and a cycle life.

In the case of using the film-like packaging material, the packaging material can be fixed to the electrode group by forming an adhesive part on a surface corresponding to at least the outermost periphery of the surface of the electrode group. As a result, in the secondary battery, the non-aqueous electrolyte is oxidatively decomposed, for example, stored in a high temperature atmosphere in a charged state, and the electrode group can be prevented from expanding and deforming when carbon dioxide is generated. It is possible to prevent the secondary battery from damaging the electronic device.

By setting the total amount of the adhesive polymer in the range of 0.2 to 6 mg per 100 mAh of battery capacity, the adhesion between the positive electrode, the negative electrode and the separator can be further improved while suppressing the internal resistance low. As a result, the large current characteristics and cycle life of the secondary battery can be further improved.

By setting the thickness of the separator to 30 μm or less, the internal resistance of the secondary battery can be further lowered, so that the large current characteristics and cycle life of the secondary battery can be further improved.

In addition, since the adhesiveness of the positive electrode, the negative electrode, and the separator can be further improved by setting the thermal contraction rate at 120 ° C. and 1 hour of the separator to 20% or less, the high current characteristics and cycle life of the secondary battery can be further improved.

Further, by setting the porosity of the separator to 30 to 60%, both the strength of the separator and the electrolyte retention property can be satisfied, so that the large current characteristics and cycle life of the secondary battery can be further improved.

In addition, by using a carbon material that occludes and releases lithium ions as the negative electrode, it is possible to avoid the problem of lithium dendride which is likely to occur in a thin nonaqueous electrolyte secondary battery having a negative electrode made of lithium metal or lithium alloy. .

In addition, by using the carbon material having a graphite crystal having a plane spacing d ₀₀₂ of (002) plane of 0.340 nm or less, the capacity and large current characteristics of the secondary battery can be further improved.

In addition, an electrode having at least one of the positive electrode and the negative electrode having a porous structure having a pore having a diameter of 3 mm or less at one or more ratios per 10 cm 2 is used as a current collector while securing the required electrode strength. Since the nonaqueous electrolyte can be uniformly infiltrated into the group, the cycle life of the secondary battery can be further improved.

According to the method for producing a nonaqueous electrolyte secondary battery according to the present invention, after impregnating a solution in which an adhesive polymer is dissolved in an electrode group prepared by sandwiching a separator between a positive electrode and a negative electrode, the electrode group is dried at least by drying. The polymer which has adhesiveness to the space | gap of a positive electrode, a negative electrode, and a separator can be maintained. As a result, the adhesive polymer can be distributed in at least the inside of the electrode group in a three-dimensional network shape, whereby the positive electrode, the negative electrode and the separator can be integrated while directly contacting the positive electrode on one side and the negative electrode on the other side of the separator. . Therefore, even when the film material is used as the packaging material, the adhesion between the anode cathode and the separator can be sufficiently secured, and the increase in the internal resistance due to the adhesive polymer can be suppressed. In addition, since the above-mentioned porous adhesive part can hold a nonaqueous electrolyte in the space | gap, it can contribute to conduction of lithium ion. Therefore, even when the electrode group is impregnated with a nonaqueous electrolyte and stored in a desired exterior material, a nonaqueous electrolyte secondary battery having excellent energy density, large current characteristics, and cycle life can be easily manufactured.

In the manufacturing method, after storing the electrode group produced by sandwiching the separator between the positive electrode and the negative electrode in a film-like exterior material, the solution in which the adhesive polymer is dissolved is impregnated by injecting into the electrode group, and vacuum drying the electrode group. By forming a porous adhesive portion in the pores of the positive electrode, the negative electrode and the separator, as well as forming a porous adhesive portion on a surface corresponding to at least the outermost periphery of the electrode group, the film-shaped packaging material is Can be attached to a military. As a result, in the secondary battery, the nonaqueous electrolyte is oxidized and decomposed by, for example, stored in a high temperature atmosphere in a charged state, and the electrode group can be suppressed from expanding and deforming when carbon dioxide is generated. It is possible to prevent the secondary battery from damaging the electronic device.

Moreover, heat shrinkage of a separator, especially the separator containing polyethylene or a polypropylene, can be suppressed by making the said drying temperature 100 degrees C or less. As a result, since the adhesive strength of the positive electrode, the negative electrode and the separator can be further improved, the large current characteristics and cycle life of the secondary battery can be further improved.

When the drying is carried out at 100 ° C. or lower, since the evaporation rate of the solvent can be improved by using an organic solvent having a boiling point of 200 ° C. or lower as the solvent, the influence of heat on the separator can be made smaller. The adhesion strength of the positive electrode, the negative electrode and the separator can be further increased.

In addition, when the drying is performed at 100 ° C. or lower, the heat shrinkage of the separator can be reduced by setting the heat shrinkage at 120 ° C. and 1 hour of the separator at 20%, thereby further increasing the adhesive strength of the positive electrode, the negative electrode, and the separator. .

(Example)

Hereinafter, embodiments of the present invention will be described in detail with reference to the above-mentioned drawings.

Example 1

<Production of the anode>

First, 91% by weight of lithium cobalt oxide (Li _X CoO ₂ ; where X is 0 ≦ X ≦ 1), 3.5% by weight of acetylene black, 3.5% by weight of graphite, 2% by weight of ethylene propylene diene monomer and toluene were added. They were mixed together and coated on both sides of a current collector made of porous aluminum foil (15 μm in thickness) in which holes of 0.5 mm in diameter were present at a rate of 10 per 10 cm 2, and then pressed to form electrodes having an electrode density of 3 g / cm 3. I produced one piece.

<Production of the cathode>

93% by weight of mesophase pitch-based carbon fiber (fiber diameter is 8 탆, average fiber length is 20 탆, average surface spacing (d ₀₀₂ ) is 0.3360 nm) as a carbonaceous material, and as a binder 7% by weight of vinylidene fluoride (PVdF) is mixed, and the electrode density is applied to a current collector made of porous copper foil (15 µm thick) having holes of 0.5 mm in diameter at a ratio of 10 per 10 cm 2. One electrode of 1.3 g / cm <3> was produced.

〈Separator〉

Two separators made of a polyethylene porous film having a thickness of 25 μm, a heat shrinkage of 20% at 120 ° C. for 1 hour, and a porosity of 50% were prepared. Each side of the separator is 2 mm and 1.5 mm longer than each side of the positive electrode and the negative electrode, respectively, and extends 1 mm and 0.75 mm from both ends of the positive electrode and the negative electrode, respectively.

<Preparation of nonaqueous electrolyte amount>

Lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 mol / L of a mixed solvent (mixed volume ratio 1: 2) of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) to prepare a nonaqueous electrolyte.

<Production of electrode group>

The obtained positive electrode, negative electrode and separator were laminated in the order of the separator, the positive electrode, the separator, and the negative electrode, spirally wound so that the outermost periphery became a separator, and it shape | molded in flat shape as FIG. 4, and produced the electrode group. In addition, a strip-shaped positive electrode lead was welded to the current collector of the positive electrode before lamination, and a strip-shaped negative electrode lead was welded to the current collector of the negative electrode.

A laminate film having a thickness of 100 μm covered with polypropylene on both sides of the aluminum foil was molded into a sealed shape, and the electrode group was housed so that the laminated surface shown in FIG. 3 described above was seen through the opening of the bag. Polyacrylonitrile (PAN), which is an adhesive polymer, was dissolved in 0.5% by weight of dimethylformamide (boiling point: 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was 0.25 ml. The solution was allowed to penetrate into the electrode group and adhered to the entire surface of the electrode group.

Next, the organic solvent is evaporated by vacuum drying the electrode group in the laminate film at 80 ° C. for 12 hours to maintain a polymer having adhesion to the pores of the positive electrode, the negative electrode and the separator, and at the same time A porous adhesive portion was formed on the surface. The total amount of PAN was 1.25 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was 4.1 g, and the structures shown in FIGS. 1 and 2 described above were 3 mm thick, 40 mm wide, and high. A thin nonaqueous electrolyte secondary battery of 70 mm was assembled.

Example 2

A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that aluminum was used as the negative electrode.

Example 3

The electrode group produced in the same manner as described in Example 1 was formed by molding the laminated film into a sealed shape so that the laminated surface shown in Fig. 3 described above was seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 0.5% by weight of dimethylformamide (boiling point of 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as that of Example 1, and the solution was allowed to penetrate the inside of the electrode group and adhere to the entire surface of the electrode group.

The electrode group in the laminate film is then vacuum dried at 40 ° C. for 24 hours to evaporate the organic solvent, to maintain a polymer having adhesion to the pores of the positive electrode, the negative electrode and the separator, A porous adhesive portion was formed on the surface. The total amount of PVdF was 1.15 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIGS. 1 and 2 described above, having a thickness of 3 mm and a width of 40 mm, A thin nonaqueous electrolyte secondary battery having a height of 70 mm was assembled.

Example 4

A thin nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 3 except that the conditions for vacuum drying were 80 ° C and 12 hours.

Example 5

A thin nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 3 except that the conditions for vacuum drying were 100 ° C and 6 hours.

Example 6

A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except that aluminum was used as the negative electrode.

Example 7

The electrode group produced in the same manner as described in Example 1 was formed by molding the laminated film into a sealed shape so that the laminated surface shown in FIG. 3 described above was seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 0.1% by weight of dimethylformamide (boiling point of 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as that of Example 1, and the solution was allowed to penetrate into the inside of the electrode group and adhered to the entire surface of the electrode group. .

Next, the organic solvent is evaporated by vacuum drying the electrode group in the laminate film at 80 ° C. for 12 hours to maintain a polymer having adhesion to the pores of the positive electrode, the negative electrode and the separator, and at the same time A porous adhesive portion was formed on the surface. The total amount of PVdF was 0.23 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Example 8

The electrode group produced in the same manner as described in Example 1 was formed by molding the laminated film into a sealed shape so that the laminated surface shown in FIG. 3 described above was seen from the opening of the bag. Polyvinylidene fluoride (PVdF), an adhesive polymer, was dissolved in 1% by weight of dimethylformamide (boiling point: 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the inside of the electrode group and adhere to the entire surface of the electrode group. .

The electrode group in the laminate film was then vacuum dried at 80 ° C. for 12 hours to evaporate the organic solvent to maintain a polymer having adhesiveness in the pores of the positive electrode, the negative electrode, and the separator. A porous adhesive portion was formed on the surface. The total amount of PVdF was 2.3 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Example 9

The electrode group produced in the same manner as described in Example 1 was formed by molding the laminated film into a sealed shape so that the laminated surface shown in FIG. 3 described above was seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 2.5% by weight in dimethylformamide (boiling point: 153 占 폚) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as that of Example 1, and the solution was allowed to penetrate into the inside of the electrode group and adhered to the entire surface of the electrode group. .

Next, the organic solvent was evaporated by vacuum drying the electrode group in the laminate film at 80 ° C. for 12 hours to maintain a polymer having adhesiveness in the pores of the positive electrode, the negative electrode and the separator, A porous adhesive portion was formed on the surface. The total amount of PVdF was 2.88 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Example 10

The electrode group produced in the same manner as described in Example 1 in the laminate film formed in the encapsulated shape was housed so that the laminated surface was seen from the opening of the encapsulation as shown in FIG. Polyacrylate (PMMA), which is an adhesive polymer, was dissolved in 1% by weight of dimethylformamide (boiling point: 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as that of Example 1, and the solution was allowed to penetrate into the inside of the electrode group and adhere to the entire surface of the electrode group. .

The electrode group in the laminate film was then vacuum dried at 80 ° C. for 12 hours to evaporate the organic solvent to maintain a polymer having adhesion to the pores of the positive electrode, the negative electrode and the separator, and at the same time, the surface of the electrode group. The porous adhesive portion was formed in the. The total amount of PMMA was 1.15 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Example 11

The electrode group produced in the same manner as that described in Example 1 was formed by molding the laminated film into an encapsulation shape, so that the laminated surface shown in Fig. 3 described above was seen from the opening of the encapsulation. Polyvinyl chloride (PVC), which is an adhesive polymer, was dissolved in 0.5% by weight of dimethylformamide (boiling point: 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as that of Example 1, and the solution was allowed to penetrate into the inside of the electrode group and adhered to the entire surface of the electrode group. .

Next, the organic solvent is evaporated by vacuum drying the electrode group in the laminate film at 80 ° C. for 12 hours to maintain a polymer having adhesion to the pores of the positive electrode, the negative electrode and the separator, and at the same time A porous adhesive portion was formed on the surface. The total amount of PVC was 1.15 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Example 12

The electrode group produced in the same manner as described in Example 1 was formed by molding the laminated film into a sealed shape so that the laminated surface shown in FIG. 3 described above was seen from the opening of the bag. Polyethylene oxide (PEO), an adhesive polymer, was dissolved in 0.5% by weight of dimethylformamide (boiling point: 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the laminate film such that the amount per 100 mAh of battery capacity was the same as that of Example 1, and the solution was allowed to penetrate into the inside of the electrode group and adhered to the entire surface of the electrode group. .

Next, the organic solvent was evaporated by vacuum drying the electrode group in the laminate film at 80 ° C. for 12 hours to maintain a polymer having adhesiveness in the pores of the positive electrode, the negative electrode and the separator, A porous adhesive portion was formed on the surface. The total amount of PEO was 1.15 mg per 100 mAh of battery capacity.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Comparative Example 1

The electrode group produced by molding the laminate film in the encapsulated shape in the same manner as described in Example 1 was stored so that the laminated surface shown in Fig. 3 described above was seen from the opening of the encapsulation, and vacuum drying was applied to the electrode group. It carried out at 80 degreeC for 12 hours. The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and had the structure shown in FIG. 1 described above. The thickness was 3 mm, the width was 40 mm, and the height was 70. A mm non-aqueous electrolyte secondary battery was assembled.

Comparative Example 2

Instead of the non-aqueous electrolyte solution, a gel electrolyte (polyacrylonitrile (PAN), LiPF ₆ , EC and MEC mixed with a molar ratio PAN: LiPF ₆ : EC: MEC = 16: 5: 55: 24) was added to the nonwoven fabric separator. A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that it was used by impregnation and no porous adhesive layer was formed.

Comparative Example 3

Polyvinylidene fluoride (PVdF), an adhesive polymer, was dissolved in 3% by weight in dimethylformamide (boiling point of 153 ° C) as an organic solvent. The obtained solution was applied to both surfaces of the same separator as described in Example 1. A laminate was prepared by sandwiching the separator between the same positive electrode and negative electrode A, B as described in Example 1. The laminate was vacuum dried at 80 ° C. for 12 hours to form a porous adhesive layer between the positive electrode and the separator and between the negative electrode and the separator. Next, the laminate was wound in a spiral shape and then molded into a flat shape to prepare an electrode group.

The nonaqueous electrolyte was injected into the electrode group in the laminate film such that the amount per 1Ah of the battery capacity was the same as that of Example 1, and a thin nonaqueous electrolyte secondary battery having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm was assembled.

The obtained secondary batteries of Examples 1, 3 to 5, 7 to 12 and Comparative Examples 1 to 3 were charged for 20 hours at a charge current of 20 mA at a charge current of 300 mA to 4.2 V, and then discharged from 300 mA to 2.7 V. Carried out in the atmosphere. On the other hand, the secondary batteries of Examples 2 and 6 were charged and discharged from 300 mA to 4.0 V for 5 hours, and then charged and discharged in a 20 ° C atmosphere. The discharge capacity (initial capacity) of the 1st cycle in each charge / discharge cycle test, and the capacity | capacitance retention rate (relative to the said initial capacity) at 300 cycles are shown in Table 2 below.

In addition, the secondary batteries of Examples 1, 3 to 5, 7 to 12 and Comparative Examples 1 to 3 were charged for 5 hours from 300 mA to 4.2 V of charging current, and then discharged at 2 C to 2.7 V. Then, the capacity retention ratio (ratio of the discharge capacity at 2C to the initial capacity) at 2C discharge rate is calculated, and the results are written together in Table 2 below. On the other hand, for the secondary batteries of Examples 2 and 6, after charging for 5 hours from 300 mA to 4.0 V of charging current, the discharge capacity when discharged from 2 C to 2.7 V was measured to calculate the capacity retention rate at the 2 C discharge rate. The results are written together in Table 2 below.

Types of Adhesive Polymers % Of adhesive polymer in solution Temperature of Vacuum Drying (℃) cathode Example 1 PAN 0.5 80 Carbonaceous material Example 2 PAN 0.5 80 A1 Example 3 PVdF 0.5 40 Carbonaceous material Example 4 PVdF 0.5 80 Carbonaceous material Example 5 PVdF 0.5 100 Carbonaceous material Example 6 PVdF 0.5 80 A1 Example 7 PVdF 0.1 80 Carbonaceous material Example 8 PVdF One 80 Carbonaceous material Example 9 PVdF 2.5 80 Carbonaceous material Example 10 PMMA 0.5 80 Carbonaceous material Example 11 PVC 0.5 80 Carbonaceous material Example 12 PEO 0.5 80 Carbonaceous material Comparative Example 1 No adhesive polymer (nonaqueous electrolyte) Carbonaceous material Comparative Example 2 No adhesive polymer (gel electrolyte) Carbonaceous material Comparative Example 3 PVdF 3.0 80 Carbonaceous material

Initial capacity (㎃h) Capacity maintenance rate after 300 cycles (%) 2C discharge rate capacity retention rate (%) Example 1 600 80 75 Example 2 550 75 70 Example 3 550 75 75 Example 4 620 90 85 Example 5 600 80 60 Example 6 550 75 70 Example 7 600 70 90 Example 8 600 85 70 Example 9 550 70 50 Example 10 600 85 70 Example 11 500 80 70 Example 12 400 80 70 Comparative Example 1 50 0 0 Comparative Example 2 400 70 40 Comparative Example 3 450 30 50

As can be seen from Tables 1 and 2, the secondary batteries of Examples 1 to 12 having an electrode group in which an adhesive portion was formed on the surface, and each of the polymers having adhesiveness in the pores of the positive electrode, the negative electrode, and the separator were held, respectively. It is understood that the capacity and cycle life are excellent, and in particular, the discharge capacity at a large current of 2C can be improved as compared with the secondary batteries of Comparative Examples 1 to 3. In particular, it can be seen that the secondary battery of Example 4 in which the adhesive polymer is PVdF has superior initial capacity, cycle life, and large current discharge characteristics as compared to the secondary batteries of Examples 1, 10 to 12, wherein the polymer is PAN, PVC, and PEO. have.

On the other hand, it can be seen that the secondary battery of Comparative Example 1 having an electrode group containing no adhesive polymer has much lower initial capacity, cycle life, and large current discharge capacity than Examples 1 to 12. On the other hand, it can be seen that the secondary battery of Comparative Example 2, which does not contain an adhesive polymer and uses a gel electrolyte instead of the nonaqueous electrolyte, has a lower discharge capacity at a large current of 2C than the secondary batteries of Examples 1 to 8. In addition, it can be seen that the secondary battery of Comparative Example 3 having an electrode group having a porous adhesive layer disposed between the positive electrode and the separator and between the negative electrode and the separator has a lower initial capacity, cycle life, and large current discharge capacity than those of Examples 1 to 12. .

Example 13

<Production of the anode>

First, 91% by weight of lithium cobalt oxide (Li _X CoO ₂ ) powder was mixed with 3.5% by weight of acetylene black, 3.5% by weight of graphite, 2% by weight of ethylene propylene diene monomer and toluene, and mixed together, and an aluminum foil having a thickness of 30 μm. After apply | coating to both surfaces of the electrical power collector which consists of these, it pressed and produced the positive electrode of the structure whose electrode density is 3 g / cm <3>, and the positive electrode layer was hold | maintained on both surfaces of an electrical power collector.

<Production of the cathode>

93% by weight of mesophase pitch-based carbon fiber (fiber diameter is 8 탆, average fiber length is 20 탆, average surface spacing (d ₀₀₂ ) is 0.3360 nm) as a carbonaceous material, and as a binder 7% by weight of vinylidene fluoride (PVdF) was mixed, and this was applied to both surfaces of a copper foil having a thickness of 15 µm as a current collector, dried, and pressed, so that the electrode density was 1.3 g / cm 3, and the negative electrode layer was supported on both sides of the current collector. A cathode of the structure was produced.

The positive electrode and the negative electrode were spirally wound through a separator made of a polyethylene porous film having a thickness of 15 μm to prepare an electrode group.

Next, the electrode group was housed in a cylindrical container having a bottom made of stainless steel. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 0.1% by weight of dimethylformamide (boiling point: 153 ° C) as an organic solvent. The obtained solution was injected into the electrode group in the container so that the amount per 100 mAh of battery capacity was 0.25 ml. The solution was allowed to penetrate into the electrode group and adhered to the entire surface of the electrode group.

Next, the electrode group in the container is vacuum dried at 80 ° C. for 12 hours to evaporate the organic solvent, to maintain a polymer having adhesion to the pores of the positive electrode, the negative electrode and the separator, and at the same time, the surface of the electrode group. The porous adhesive portion was formed in the. The total amount of PVdF was 0.23 mg per 100 mAh of battery capacity.

A cylindrical nonaqueous electrolyte secondary battery was assembled by injecting the same nonaqueous electrolyte solution as described in Example 1 into the electrode group in the container so that the amount per battery capacity was 3.8 g, and then performing an opening sealing or the like.

Comparative Example 4

The electrode group was manufactured by spirally winding the same positive electrode and the same negative electrode as described in Example 13 above through a separator made of a polyethylene porous film having a thickness of 25 μm.

Next, the electrode group was housed in a stainless steel bottomed cylindrical container, and the same nonaqueous electrolyte as described in Example 1 was injected so that the amount per battery capacity of 1 Ah was 3.8 g, and the sealing was performed by opening the cylindrical nonaqueous electrolyte. Assembled a secondary battery.

The secondary batteries of Example 13 and Comparative Example 4 obtained were charged and discharged in a 20 ° C atmosphere after charging for 3 hours from 800 mA to 4.2 V of charge current and then discharging from 800 mA to 2.7 V. The discharge capacity (initial capacity) of the 1st cycle in each charge / discharge cycle test, and the capacity retention rate (relative to the said initial capacity) at 300 cycles are shown in Table 3 below.

In addition, after charging the secondary batteries of Example 13 and Comparative Example 4 for 3 hours from 800 mA to 4.2 V of charging current, the discharge capacity when discharged from 2 C to 2.7 V was measured, and the capacity retention rate at 2 C discharge rate was measured. The ratio of the discharge capacity at 2C to the initial capacity) is calculated and the results are written together in Table 3 below.

Initial capacity (㎃h) Capacity maintenance rate after 300 cycles (%) 2C discharge rate capacity retention rate (%) Example 13 1800 95 90 Comparative Example 4 1600 85 80

As can be seen from Table 3, the secondary battery of Example 13, in which an electrode group in which an adhesive portion was formed on the surface and a polymer having adhesiveness at each of the positive electrode, the negative electrode, and the separator were held, was housed in a metal container. Compared with the secondary battery of the comparative example 4 provided with the electrode group which does not contain, it turns out that a thin separator can be used and it is excellent in initial stage capacity, a cycle life, and a large current discharge characteristic.

In addition, in the thin nonaqueous electrolyte secondary battery of the above-described embodiment, an example in which the electrode group is formed using a plurality of positive electrodes, separators, and negative electrodes has been described. However, the electrode group may be configured using one positive electrode, one separator, and one negative electrode.

In Example 1, the positive electrode, the negative electrode, and the separator are laminated in the order of the separator, the positive electrode, the separator, and the negative electrode, and the electrode group is manufactured by forming a flat shape as shown in FIG. However, the electrode group as shown in Fig. 5 was fabricated by laminating and folding in the order of the positive electrode, the separator, and the negative electrode to fabricate the same thin nonaqueous electrolyte secondary battery as in Example 4, but the battery capacity was reduced by about 10% compared to Example 4. Outer performance was equivalent to Example 4.

In addition, although the above-mentioned embodiment demonstrated the example applied to the cylindrical nonaqueous electrolyte secondary battery provided with the cylindrical container which has a metal bottom, the square nonaqueous electrolyte secondary battery provided with the rectangular cylindrical container which has a metal bottom was also demonstrated. The same can be applied.

As described above, according to the present invention, it is possible to provide a nonaqueous electrolyte secondary battery capable of improving discharge capacity, cycle performance and large current discharge characteristics and having a thin structure having a thickness of 4 mm or less.

According to the present invention, it is possible to provide a method for producing a non-aqueous electrolyte secondary battery which can improve the discharge capacity, cycle performance, large current discharge characteristics, and thickness reduction of 4 mm or less in a simple manner.

Claims (7)

An electrode group having a separator disposed between the anode, the cathode, the anode and the cathode, the separator including a porous sheet having an air transmittance of 600 seconds / 100 cm 3 or less; A nonaqueous electrolyte impregnated in the electrode group; And It is provided with an exterior material to accommodate the electrode group, The positive electrode and the separator are bonded by an adhesive polymer held in each gap, and the negative electrode and the separator are bonded by a polymer having adhesiveness held in each gap. Secondary battery. The method of claim 1, A nonaqueous electrolyte secondary battery, further comprising: an exterior material surrounding the electrode group, wherein the exterior material is adhered to the electrode group by the adhesive polymer. The method of claim 1, The total amount of the adhesive polymer is in the range of 0.2 to 6 mg per 100 mAh of battery capacity, and the amount of the non-aqueous electrolyte is in the range of 0.2 to 0.6 g per 100 mAh of battery capacity. . Manufacturing a electrode group by sandwiching a separator between the positive electrode and the negative electrode, Impregnating the electrode group with a solution in which an adhesive polymer is dissolved, Drying and molding the electrode group; and And a step of impregnating the nonaqueous electrolyte solution into the electrode group. The method of claim 4, wherein A method for producing a non-aqueous electrolyte secondary battery, characterized in that the concentration of the solution in which the polymer having an adhesive is dissolved is 0.1 wt% or more and 2.5 wt% or less. An electrode group having a separator disposed between an anode, a cathode, the anode, and the cathode, and a nonaqueous electrolyte solution, At least the pores of the positive electrode, the negative electrode and the separator are each maintained with an adhesive polymer, the positive electrode, the negative electrode and the separator are bonded and integrated, and the electrode group is the positive electrode, the negative electrode and the separator is wound or Non-aqueous electrolyte secondary battery, characterized in that the folded and bent. The method of claim 6, The stage of the separator extends from the stage of each of the positive electrode and the negative electrode, and a non-aqueous electrolyte secondary battery, characterized in that a polymer having an adhesive is present in the extended portion.