JP2003157847A - Method of manufacturing electrode for lithium battery and electrode for lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode for a lithium battery having an excellent output at a low temperature. SOLUTION: This method of manufacturing the electrode for the lithium battery comprises a process to prepare an active material paste having an active material, water and a binder, and a process to apply the active material paste to the surface of a collector and to dry it. The binder has cellulose having adjusted characteristics. In this method, a gap through which lithium ions can pass is formed when the binder coats the surface of the active material, and movement of the lithium ions on the boundary surface of the active material is no more impeded. Thereby, a battery having an enhanced output at a low temperature can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode for a lithium battery and an electrode for a lithium battery, and more specifically, a method for manufacturing an electrode for a lithium battery which can obtain a lithium battery having excellent low temperature characteristics and a lithium battery Regarding electrodes.

[0002]

2. Description of the Related Art In recent years, as a power source for electric devices such as mobile phones and portable video cameras, a lithium battery is becoming mainstream because of its high weight energy density.
This lithium battery has a positive electrode having a positive electrode active material containing lithium and capable of releasing lithium as lithium ions during charging and occluding lithium ions during discharging,
Consists of a negative electrode that has a negative electrode active material and is capable of occluding lithium ions during charging and releasing lithium ions during discharging, and a non-aqueous electrolytic solution in which an electrolyte composed of a supporting salt containing lithium in an organic solvent is dissolved. To be done.

Further, in such a lithium battery, in order to improve the weight energy density, the positive electrode and the negative electrode are formed in a sheet shape, and the sheet-shaped positive electrode and the negative electrode are formed through a separator which is also formed in the sheet shape. It is housed in a case in a wound or laminated state. The sheet-shaped positive electrode and negative electrode each have a structure in which a mixture layer containing an active material is formed on the surface of a metal foil serving as a current collector.

The positive electrode of the lithium battery is LiMexOy.
(Me; a transition metal containing at least one of Ni, Co and Mn, x and y are not particularly limited),
Conductive agent made of carbon, etc., carboxymethyl cellulose (CMC) and polytetrafluoroethylene (PTF
It is manufactured by preparing an active material paste in which a binder composed of E) or the like is dispersed in a solvent, and coating the prepared active material paste on the surface of a current collector to form a mixture layer.

In the production of a positive electrode for a lithium battery, an organic solution such as N-methyl-2-pyrrolidone (NMP) has been used as a solvent. On the other hand, water has been used as a solvent because of the reduction of raw materials and costs required for handling and the impact on the environmental load at the time of discharge.

However, the output of a positive electrode manufactured by using water as a solvent is particularly low at a low temperature as compared with a positive electrode manufactured by using an organic solvent such as polyvinylidene fluoride (PVDF). Had a problem.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of producing an electrode for a lithium battery, which can produce an electrode whose low-temperature output does not decrease even when a solvent made of water is used as an active material paste. The challenge is to provide a method.

[0008]

The inventors of the present invention have investigated the cause of the decrease in low-temperature output, and as a result, CMC used as a binder covers the surface of the active material, and the binder coated with this active material forms a battery. It was speculated that when formed, it hindered the migration of lithium ions at the active material interface.

As a result, in order to solve the above-mentioned problems, the present inventors have repeatedly studied a binder which does not inhibit the movement of lithium ions even when the surface of the active material is covered, and as a result, the kind of the binder is adjusted and It has been found that the movement of lithium ions is not hindered by increasing the gap between the molecules that make up.

That is, the method for producing an electrode for a lithium battery of the present invention comprises at least an active material, water, a binder,
In the method for manufacturing an electrode for a lithium battery, the method including: a step of preparing an active material paste having: and a step of applying the active material paste onto a surface of a current collector and drying the binder, wherein the binder has a viscosity of 4000 mPa in a 1% aqueous solution. -Characterized by having s or more cellulose.

In the method for producing an electrode for a lithium battery of the present invention, since cellulose having a large molecular weight is used as a binder, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions at the active material interface is not obstructed, and a battery having improved low-temperature output when the battery is formed can be obtained.

In the lithium battery electrode of the present invention, a step of preparing an active material paste having at least an active material, water, and a binder, and a step of applying the active material paste on the surface of a current collector and drying it. And a binder having a viscosity of 4000 m in a 1% aqueous solution.
It is characterized by having a cellulose of Pa · s or more.

In the lithium battery electrode of the present invention, since cellulose having a large molecular weight is used as a binder, a gap through which lithium ions can pass is formed in the binder covering the surface of the active material. As a result, in the lithium battery electrode of the present invention, the movement of lithium ions at the active material interface is not obstructed, and a low temperature output is improved when the battery is formed.

The method for producing an electrode for a lithium battery according to the present invention comprises a step of preparing an active material paste having at least an active material, water and a binder, and applying the active material paste on the surface of a current collector. The method for producing an electrode for a lithium battery, which comprises the step of drying, wherein the binder has cellulose having a weight average molecular weight of 1.4 million or more.

In the method for producing an electrode for a lithium battery of the present invention, since cellulose having a large molecular weight is used as a binder, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions at the active material interface is not obstructed, and a battery having improved low-temperature output when the battery is formed can be obtained.

In the lithium battery electrode of the present invention, a step of preparing an active material paste having at least an active material, water, and a binder, and a step of applying the active material paste on the surface of a current collector and drying it. An electrode for a lithium battery obtained by performing the method for producing an electrode for a lithium battery having the above, wherein the binder has cellulose having a weight average molecular weight of 1.4 million or more.

In the lithium battery electrode of the present invention, cellulose having a large molecular weight is used as a binder, so that a gap through which lithium ions can pass is formed in the binder covering the surface of the active material. As a result, in the lithium battery electrode of the present invention, the movement of lithium ions at the active material interface is not obstructed, and a low temperature output is improved when the battery is formed.

The method for producing an electrode for a lithium battery of the present invention comprises a step of preparing an active material paste having at least an active material, water and a binder, and applying the active material paste on the surface of a current collector, In the method for producing an electrode for a lithium battery, which comprises a step of drying, the binder contains cellulose having a weight average molecular weight / number average molecular weight of 5 or more.

In the method for producing an electrode for a lithium battery of the present invention, since the binder has cellulose having a wide molecular weight distribution, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions is not obstructed, and the low temperature output is improved when the battery is formed.

In the lithium battery electrode of the present invention, a step of preparing an active material paste having at least an active material, water, and a binder, and a step of applying the active material paste on the surface of a current collector and drying it. An electrode for a lithium battery, which is obtained by performing the method for producing an electrode for a lithium battery including: and the binder has a weight average molecular weight / number average molecular weight of 5 or more.

In the lithium battery electrode of the present invention, since the binder has cellulose having a wide molecular weight distribution, even if the binder covers the surface of the active material, a gap is formed through which lithium ions can pass. As a result, the lithium battery electrode of the present invention has improved low-temperature output when a battery is formed.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION (First Invention) (Production Method) A method for producing an electrode for a lithium battery of the present invention comprises a step of preparing an active material paste containing at least an active material, water, and a binder, In the method for producing an electrode for a lithium battery, which comprises a step of applying an active material paste on a surface of a current collector and drying, a binder is 1%.
It has a viscosity of 4000 mPa · s or more in an aqueous solution.

At least an active material, water, a binder,
In the step of preparing an active material paste having the above, an active material paste using water as a solvent is prepared.

Apply the active material paste on the surface of the current collector,
By the step of drying to form the active material mixture layer, the active material mixture layer is formed on the surface of the current collector to form the lithium battery electrode.

In the manufacturing method of the present invention, an active material paste is prepared, and the prepared active material paste is applied to the surface of a current collector and dried to manufacture a lithium battery electrode. Also,
An active material paste having a binder and an active material is prepared and dried to obtain an active material whose surface is coated with the binder.

The binder has a viscosity of 4 in a 1% aqueous solution.
It has cellulose of 000 mPa · s or more. Since the binder has a cellulose having a viscosity of 4000 mPa · s or more in a 1% aqueous solution, inhibition of migration of lithium ions at the active material interface of the manufactured lithium battery electrode is suppressed, and the low temperature of the battery using this electrode is suppressed. The characteristics are improved.
In the production method of the present invention, the viscosity of the binder is
The viscosity at room temperature (about 25 ° C.) is shown.

More specifically, the binder having cellulose having a large molecular weight is located on the surface of the active material in a non-uniform state at the particle level before the active material paste is applied. When the active material paste is dried in this state, the binder is fixed on the surface of the active material in a non-uniform state. When fixed in a non-uniform manner, a gap is left on the surface of the active material that is not covered by the binder, and lithium ions will pass through this gap when the lithium battery is assembled. As a result, sufficient movement of lithium ions is ensured, so that the battery characteristics at low temperatures are improved.

Further, cellulose having a large molecular weight is a bulky molecule. Therefore, even if the binder covers the surface of the active material, a gap is created between the molecular chains due to the bulkiness of the cellulose molecule, and the migration path of lithium ions is secured.

Generally, the viscosity of cellulose when dissolved in water and the molecular weight of cellulose have a positive correlation. That is, the higher the viscosity of the aqueous cellulose solution, the higher the molecular weight of cellulose.

Further, according to the production method of the present invention, the binder having the high viscosity cellulose increases the viscosity of the active material paste prepared, and the amount of the binder can be reduced. That is, since the viscosity of the active material paste can be imparted with a small amount of binder, the amount of binder can be reduced. When the amount of the binder decreases, the amount of the binder that covers the surface of the active material decreases, and the inhibition of lithium ion migration at the active material interface decreases. As a result, the low temperature characteristics of the battery assembled using the positive electrode are improved.

The cellulose is not limited as long as it can be used as a binder.
Since the production method of the present invention uses water as a solvent to prepare an active material paste, the binder is required to be a water-soluble polymer. Examples of water-soluble celluloses include carboxymethyl cellulose (CMC), hydroxyl cellulose, and methyl cellulose.

The binder preferably has a water-soluble polymer having a molecular weight different from that of cellulose. By having a water-soluble polymer having a different molecular weight from that of cellulose, the gap between the binders coated with the active material increases. That is, by arranging the water-soluble polymers having different molecular weights, the steric hindrance between the molecules constituting the binder is increased, and a gap is formed on the surface of the active material.

Examples of the water-soluble polymer include not only cellulose but also water-soluble polymers such as polyethylene oxide (PEO), ethyl cellulose, polyvinyl alcohol and polyacrylate.

Further, it is preferable that the binder has a resin dispersed in water. Examples of the resin dispersed in water include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)
Examples thereof include water-dispersion type resins having excellent organic solvent resistance such as fluorine-based resins such as, acrylic resins, olefins such as polyethylene and polyolefin, and polyimide resins.

The method for producing the lithium battery electrode of the present invention is not particularly limited except that the binder contains cellulose. That is, as the material forming the active material paste, the material used in the conventional production of electrodes for lithium batteries can be used.

The production method of the present invention can be applied to the production of positive electrodes and negative electrodes. Furthermore, it is more effective if both the positive electrode and the negative electrode manufactured by the manufacturing method of the present invention are applied to a battery. The lithium battery electrode manufactured by the manufacturing method of the present invention is more preferably a lithium battery positive electrode.

When the manufacturing method of the present invention is applied to the positive electrode, the active material becomes the positive electrode active material.

The positive electrode active material is LiMexOy (Me; N
i, Co, transition metal containing at least one of Mn, x,
y; arbitrary) is preferable. This LiMexOy
Is not particularly limited. For example, LiMn
A compound having O ₂ , LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ as a main skeleton and substituted with various metal elements can be used.

LiMn ₂ O ₄ system, LiCoO ₂ system, LiN
An iO ₂ -based positive electrode active material is more preferable. That is, since it has excellent performance as a positive electrode active material such as excellent diffusion performance of electrons and lithium ions, a lithium battery having high charge / discharge efficiency and good cycle characteristics can be obtained. Further, it is preferable to use a LiMn ₂ O ₄ -based positive electrode active material because of low material cost.

The active material paste preferably has a conductive material. Since the active material paste has the conductive material, the characteristics of the manufactured positive electrode are improved.

The conductive material ensures the electric conductivity of the positive electrode.
As the conductive material, for example, carbon black, acetylene black, a carbon material such as graphite, or a mixture of two or more carbon materials can be used.

As the current collector of the positive electrode to which the active material paste is applied, for example, a metal such as aluminum or stainless can be used as a net, punched metal, foam metal or a foil processed into a plate shape. .

When the manufacturing method of the present invention is applied to a negative electrode, the active material becomes a negative electrode active material.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Examples thereof include lithium metal, graphite, and carbon materials such as amorphous carbon. A carbon material is preferable as the negative electrode active material formed of an intercalating material capable of electrochemically absorbing and desorbing lithium without deposition of dendrite-like lithium which causes a short circuit defect or the like.

The active material paste preferably contains a binder and the like, if necessary, in addition to the negative electrode active material.

The binder has a function of binding the active material particles. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as polyvinylidene fluoride (PVDF), polyvinylidene chloride, and polytetrafluoroethylene (PTFE). You can

As the current collector of the negative electrode, for example, a net, punched metal, foam metal or a foil processed into a plate shape of copper, nickel or the like can be used.

Further, in the method for producing a lithium battery electrode of the present invention, it is preferable to compress the current collector and the active material mixture layer after the active material mixture layer is formed. The compression improves the density of the active material mixture layer and shortens the distance between the active material particles.

In the method for producing an electrode for a lithium battery of the present invention, since cellulose having a large molecular weight is used as a binder, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions is not hindered and the low temperature output is improved.

(Lithium Battery Electrode) The lithium battery electrode of the present invention comprises a step of preparing an active material paste having at least an active material, water and a binder, and the active material paste on the surface of the current collector. Applying and drying,
A lithium battery electrode obtained by performing the method for producing a lithium battery electrode having the above, wherein the binder has cellulose having a viscosity of 4000 mPa · s or more in a 1% aqueous solution.

In the step of preparing an active material paste containing at least an active material and water, an active material paste using water as a solvent is prepared.

By the step of applying the active material paste on the surface of the current collector made of Al and drying it to form the active material mixture layer, the active material mixture layer is formed on the surface of the current collector, and the lithium battery is formed. It becomes an electrode for.

The lithium battery electrode of the present invention is manufactured by preparing an active material paste, coating the prepared active material paste on the surface of a current collector, and drying. In addition, an active material paste having a binder and an active material is prepared and dried to obtain an active material whose surface is coated with the binder.

The binder has a viscosity of 4 in a 1% aqueous solution.
It has cellulose of 000 mPa · s or more. Since the binder has a cellulose having a viscosity of 4000 mPa · s or more in a 1% aqueous solution, the lithium battery electrode is suppressed from inhibiting the movement of lithium ions at the active material interface.
The low temperature characteristics of the battery are improved. In the lithium battery electrode of the present invention, the viscosity of the binder is room temperature (25 ° C.).
Shows the viscosity at.

More specifically, the binder having cellulose having a large molecular weight is located on the surface of the active material in a non-uniform state at the particle level before the active material paste is applied. When the active material paste is dried in this state, the binder is fixed on the surface of the active material in a non-uniform state. When fixed in a non-uniform manner, a gap is left on the surface of the active material that is not covered by the binder, and lithium ions will pass through this gap when the lithium battery is assembled. As a result, sufficient movement of lithium ions is ensured, and the low temperature characteristics are improved.

Further, cellulose having a large molecular weight is a bulky molecule. Therefore, even if the binder covers the surface of the active material, a gap is created between the molecular chains due to the bulkiness of the cellulose molecule, and the migration path of lithium ions is secured.

Generally, the viscosity of cellulose when dissolved in water and the molecular weight of cellulose have a positive correlation. That is, the higher the viscosity of the aqueous cellulose solution, the higher the molecular weight of cellulose.

Furthermore, since the binder has a high-viscosity cellulose, the viscosity of the active material paste also increases, and the amount of the binder can be reduced. That is, since the viscosity of the active material paste can be imparted with a small amount of binder, the amount of binder can be reduced. When the amount of binder decreases,
The amount of binder coating the surface of the active material is reduced, and inhibition of lithium ion migration at the active material interface is suppressed. As a result, the low temperature characteristics of the battery assembled using the lithium battery electrode of the present invention are improved.

The cellulose is not limited as long as it can be used as a binder.
The lithium battery electrode of the present invention, in the manufacturing process,
Since the active material paste is prepared using water as a solvent, the binder is required to be a water-soluble polymer. Examples of water-soluble celluloses include carboxymethyl cellulose (CMC), hydroxyl cellulose, and methyl cellulose.

The binder preferably has a water-soluble polymer having a molecular weight different from that of cellulose. By having a water-soluble polymer having a different molecular weight from that of cellulose, the gap between the binders coated with the active material increases. That is, by arranging the water-soluble polymers having different molecular weights, the steric hindrance between the molecules constituting the binder is increased, and a gap is formed on the surface of the active material.

Examples of the water-soluble polymer include not only cellulose but also water-soluble polymers such as polyethylene oxide (PEO), ethyl cellulose, polyvinyl alcohol and polyacrylate.

Further, it is preferable that the binder has a resin dispersed in water. Examples of the resin dispersed in water include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)
Examples thereof include water-dispersion type resins having excellent organic solvent resistance such as fluorine-based resins such as, acrylic resins, olefins such as polyethylene and polyolefin, and polyimide resins.

The lithium battery electrode of the present invention is not particularly limited in the manufacturing process, except that the binder contains cellulose. That is, as the material forming the active material paste, the material used in the conventional production of electrodes for lithium batteries can be used.

The lithium battery electrode of the present invention can be applied to a positive electrode and a negative electrode. Further, the lithium battery electrode of the present invention is more effective if both the positive electrode and the negative electrode are applied to the battery. The lithium battery electrode of the present invention is more preferably a lithium battery positive electrode.

When the lithium battery electrode of the present invention is used as a positive electrode, the active material is a positive electrode active material.

The positive electrode active material is LiMexOy (Me; N
i, Co, transition metal containing at least one of Mn, x,
y; arbitrary) is preferable. This LiMexOy
Is not particularly limited. For example, LiMn
A compound having O ₂ , LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ as a main skeleton and substituted with various metal elements can be used.

LiMn ₂ O ₄ system, LiCoO ₂ system, LiN
An iO ₂ -based positive electrode active material is more preferable. That is, since it has excellent performance as a positive electrode active material such as excellent diffusion performance of electrons and lithium ions, a lithium battery having high charge / discharge efficiency and good cycle characteristics can be obtained. Further, it is preferable to use a LiMn ₂ O ₄ -based positive electrode active material because of low material cost.

The active material paste preferably has a conductive material. Since the active material paste has a conductive material, the characteristics of the positive electrode are improved.

The conductive material ensures the electric conductivity of the positive electrode.
As the conductive material, for example, carbon black, acetylene black, a carbon material such as graphite, or a mixture of two or more carbon materials can be used.

As the current collector of the positive electrode to which the active material paste is applied, for example, a metal such as aluminum or stainless steel can be used as a net, punched metal, foam metal or a foil processed into a plate shape. .

When the lithium battery electrode of the present invention is used as a negative electrode, the active material becomes a negative electrode active material.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Examples thereof include lithium metal, graphite, and carbon materials such as amorphous carbon. A carbon material is preferable as the negative electrode active material formed of an intercalating material capable of electrochemically absorbing and desorbing lithium without deposition of dendrite-like lithium which causes a short circuit defect or the like.

The active material paste preferably contains a binder and the like, if necessary, in addition to the negative electrode active material.

The binder has a function of binding the active material particles. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as polyvinylidene fluoride (PVDF), polyvinylidene chloride, and polytetrafluoroethylene (PTFE). You can

As the current collector of the negative electrode, for example, a net, punched metal, foam metal or a foil processed into a plate shape of copper, nickel or the like can be used.

Furthermore, the electrode for a lithium battery of the present invention is
It is preferable that the current collector and the active material mixture layer are compressed after the active material mixture layer is formed. The compression improves the density of the active material mixture layer and shortens the distance between the active material particles.

In the lithium battery electrode of the present invention, since cellulose having a large molecular weight is used as a binder, even if the binder covers the surface of the active material, a gap is formed through which lithium ions can pass. As a result, the low temperature output of the lithium battery electrode of the present invention is improved.

(Second Invention) (Manufacturing Method) A method for manufacturing a lithium battery electrode according to the present invention comprises a step of preparing an active material paste containing at least an active material, water, and a binder, and In a method for producing an electrode for a lithium battery, which comprises a step of applying an active material paste on the surface and drying, the binder has cellulose having a weight average molecular weight of 1.4 million or more.

At least an active material, water, a binder,
In the step of preparing an active material paste having the above, an active material paste using water as a solvent is prepared.

Applying the active material paste on the surface of the current collector,
By the step of drying to form the active material mixture layer, the active material mixture layer is formed on the surface of the current collector to form the lithium battery electrode.

In the manufacturing method of the present invention, an active material paste is prepared, and the prepared active material paste is applied to the surface of a current collector and dried to manufacture a lithium battery electrode. Also,
An active material paste having a binder and an active material is prepared and dried to obtain an active material whose surface is coated with the binder.

The binder has a weight average molecular weight of 1.4 million or more. When the binder has a cellulose having a weight average molecular weight of 1.4 million or more, the manufactured lithium battery electrode is suppressed in inhibition of movement of lithium ions of the active material, and the low temperature characteristics of the battery using the lithium battery electrode are low. improves.

The weight average molecular weight is one of the methods for defining the molecular weight of a polymer. That is, the polymerized polymer generally has a distribution in molecular weight. Such polymers have M _1
One molecule n with a molecular weight of _two molecules of n with a molecular weight of M _2, molecules having a molecular weight of ... M _n is from n _n number of mixtures.

The molecular weight of this polymer is determined from the number average molecular weight (M _n ) calculated by dividing the sample weight shown in the following formula 1 by the number of molecules and the average value of the weight shown in formula 2. There is a weight average molecular weight (M _w ).

[0085]

[Equation 1]

[0086]

[Equation 2]

The weight average molecular weight is required because various molecules constituting the polymer contribute to the average value depending on not only the proportion contained in the mixture but also the mass thereof. A polymer having a large weight average molecular weight has a polymer having a large molecular weight.

The binder containing cellulose having a large molecular weight is located on the surface of the active material in a non-uniform state at the particle level before the active material paste is applied. When the active material paste is dried in this state, the binder is fixed on the surface of the active material, and the binder coating the surface of the active material is unevenly distributed. Therefore, a gap is formed on the surface of the active material that is not covered with the binder, and lithium ions pass through the gap when the lithium battery is assembled. As a result, sufficient movement of lithium ions is ensured, and the low temperature characteristics are improved.

Further, cellulose having a large molecular weight is a bulky molecule. From this, even if the binder covers the surface of the active material, a gap is created between the molecular chains due to the bulkiness of the cellulose molecule, and a conduction path for lithium ions is secured.

From this interaction, the larger the molecular weight of the binder cellulose, the better the low temperature characteristics of the assembled battery.

The cellulose is not limited as long as it can be used as a binder.
Since the production method of the present invention uses water as a solvent to prepare an active material paste, the binder is required to be a water-soluble polymer. Examples of water-soluble celluloses include carboxymethyl cellulose (CMC), hydroxyl cellulose, and methyl cellulose.

The binder preferably has a water-soluble polymer having a molecular weight different from that of cellulose. By having a water-soluble polymer having a different molecular weight from that of cellulose, the gap between the binders coated with the active material increases. That is, by arranging the water-soluble polymers having different molecular weights, the steric hindrance between the molecules constituting the binder is increased, and a gap is formed on the surface of the active material.

Examples of the water-soluble polymer include not only cellulose but also water-soluble polymers such as polyethylene oxide (PEO), ethyl cellulose, polyvinyl alcohol and polyacrylate.

Further, it is preferable that the binder has a resin dispersed in water. Examples of the resin dispersed in water include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)
Examples thereof include water-dispersion type resins having excellent organic solvent resistance such as fluorine-based resins such as, acrylic resins, olefins such as polyethylene and polyolefin, and polyimide resins.

The method for producing the lithium battery electrode of the present invention is not particularly limited, except that the binder contains cellulose. That is, as the material forming the active material paste, the material used in the conventional production of electrodes for lithium batteries can be used.

The production method of the present invention can be applied to the production of positive electrodes and negative electrodes. Furthermore, it is more effective if both the positive electrode and the negative electrode manufactured by the manufacturing method of the present invention are applied to a battery. The lithium battery electrode manufactured by the manufacturing method of the present invention is more preferably a lithium battery positive electrode.

When the manufacturing method of the present invention is applied to the positive electrode, the active material becomes the positive electrode active material.

The positive electrode active material is LiMexOy (Me; N
i, Co, transition metal containing at least one of Mn, x,
y; arbitrary) is preferable. This LiMexOy
Is not particularly limited. For example, LiMn
A compound having O ₂ , LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ as a main skeleton and substituted with various metal elements can be used.

LiMn ₂ O ₄ system, LiCoO ₂ system, Li
A NiO ₂ -based positive electrode active material is more preferable. That is, since it has excellent performance as a positive electrode active material such as excellent diffusion performance of electrons and lithium ions, a lithium battery having high charge / discharge efficiency and good cycle characteristics can be obtained. Further, it is preferable to use a LiMn ₂ O ₄ -based positive electrode active material because of low material cost.

The active material paste preferably has a conductive material. Since the active material paste has the conductive material, the characteristics of the manufactured positive electrode are improved.

The conductive material ensures the electric conductivity of the positive electrode.
As the conductive material, for example, carbon black, acetylene black, a carbon material such as graphite, or a mixture of two or more carbon materials can be used.

As the current collector for the positive electrode to which the active material paste is applied, for example, a metal such as aluminum or stainless steel can be used as a net, punched metal, foam metal, or a foil processed into a plate shape. .

When the manufacturing method of the present invention is applied to a negative electrode, the active material becomes a negative electrode active material.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Examples thereof include lithium metal, graphite, and carbon materials such as amorphous carbon. A carbon material is preferable as the negative electrode active material formed of an intercalating material capable of electrochemically absorbing and desorbing lithium without deposition of dendrite-like lithium that causes a short circuit defect or the like.

The negative electrode is preferably formed by coating the current collector with an active material paste obtained by mixing a binder, if necessary, in addition to the negative electrode active material.

The binder has a function of binding the active material particles. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as polyvinylidene fluoride (PVDF), polyvinylidene chloride, and polytetrafluoroethylene (PTFE). You can

As the current collector of the negative electrode, for example, a net, punched metal, foam metal or a foil processed into a plate shape of copper or nickel can be used.

Further, in the method for producing an electrode of the present invention, it is preferable to compress the current collector and the active material mixture layer after the active material mixture layer is formed. The compression improves the density of the active material mixture layer and shortens the distance between the active material particles.

In the method for producing an electrode for a lithium battery of the present invention, since cellulose having a large molecular weight is used as a binder, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions is not hindered and the low temperature output is improved.

(Lithium Battery Electrode) The lithium battery electrode of the present invention comprises a step of preparing an active material paste containing at least an active material, water, and a binder, and an active material paste on the surface of a current collector. Applying and drying,
A lithium battery electrode obtained by the method for producing a lithium battery electrode according to claim 1, wherein the binder has cellulose having a weight average molecular weight of 1.4 million or more.

In the step of preparing an active material paste containing at least an active material and water, an active material paste using water as a solvent is prepared.

By the step of applying the active material paste on the surface of the current collector made of Al and drying it to form the active material mixture layer, the active material mixture layer is formed on the surface of the current collector. It becomes an electrode for.

The electrode for a lithium battery of the present invention is manufactured by preparing an active material paste, applying the prepared active material paste on the surface of a current collector, and drying. An active material paste having a binder and an active material is prepared and dried to obtain an active material whose surface is coated with the binder.

The binder contains cellulose having a weight average molecular weight of 1.4 million or more. When the binder has cellulose having a weight average molecular weight of 1.4 million or more, in the lithium battery electrode, inhibition of movement of lithium ions of the positive electrode active material is suppressed, and the low temperature characteristics of the battery using the lithium battery electrode are improved. .

A polymer having a large weight average molecular weight has a polymer having a large molecular weight.

The binder containing cellulose having a large molecular weight is located on the surface of the active material in a non-uniform state at the particle level before the application of the active material paste. When the active material paste is dried in this state, the binder is fixed on the surface of the active material, and the binder coating the surface of the active material is unevenly distributed. Therefore, a gap is formed on the surface of the active material that is not covered with the binder, and lithium ions pass through the gap when the lithium battery is assembled. As a result, sufficient movement of lithium ions is ensured, and the low temperature characteristics are improved.

Further, cellulose having a large molecular weight is a bulky molecule. From this, even if the binder covers the surface of the active material, a gap is created between the molecular chains due to the bulkiness of the cellulose molecule, and a conduction path for lithium ions is secured.

From this interaction, the larger the molecular weight of the binder cellulose, the better the low temperature characteristics of the assembled battery.

The cellulose is not limited as long as it can be used as a binder.
The lithium battery electrode of the present invention, in the manufacturing process,
Since the active material paste is prepared using water as a solvent, the binder is required to be a water-soluble polymer. Examples of water-soluble celluloses include carboxymethyl cellulose (CMC), hydroxyl cellulose, and methyl cellulose.

The binder preferably has a water-soluble polymer having a molecular weight different from that of cellulose. By having a water-soluble polymer having a different molecular weight from that of cellulose, the gap between the binders coated with the active material increases. That is, by arranging the water-soluble polymers having different molecular weights, the steric hindrance between the molecules constituting the binder is increased, and a gap is formed on the surface of the active material.

Examples of the water-soluble polymer include not only cellulose but also water-soluble polymers such as polyethylene oxide (PEO), ethyl cellulose, polyvinyl alcohol and polyacrylate.

Further, it is preferable that the binder has a resin dispersed in water. Examples of the resin dispersed in water include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)
Examples thereof include water-dispersion type resins having excellent organic solvent resistance such as fluorine-based resins such as, acrylic resins, olefins such as polyethylene and polyolefin, and polyimide resins.

The lithium battery electrode of the present invention is not particularly limited, except that the binder contains cellulose. That is, as the material forming the active material paste, the material used in the conventional production of electrodes for lithium batteries can be used.

The lithium battery electrode of the present invention can be applied to a positive electrode and a negative electrode. Further, it is more effective if the lithium battery electrode of the present invention is applied to both the positive electrode and the negative electrode. The lithium battery electrode of the present invention is more preferably a lithium battery positive electrode.

When the lithium battery electrode of the present invention is used as a positive electrode, the active material becomes a positive electrode active material.

The positive electrode active material is LiMexOy (Me; N
i, Co, transition metal containing at least one of Mn, x,
y; arbitrary) is preferable. This LiMexOy
Is not particularly limited. For example, LiMn
A compound having O ₂ , LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ as a main skeleton and substituted with various metal elements can be used.

LiMn ₂ O ₄ system, LiCoO ₂ system, Li
A NiO ₂ -based positive electrode active material is more preferable. That is, since it has excellent performance as a positive electrode active material such as excellent diffusion performance of electrons and lithium ions, a lithium battery having high charge / discharge efficiency and good cycle characteristics can be obtained. Further, it is preferable to use a LiMn ₂ O ₄ -based positive electrode active material because of low material cost.

The active material paste preferably has a conductive material. Since the active material paste has the conductive material, the characteristics of the manufactured positive electrode are improved.

The conductive material ensures the electric conductivity of the positive electrode.
As the conductive material, for example, carbon black, acetylene black, a carbon material such as graphite, or a mixture of two or more carbon materials can be used.

As the current collector for the positive electrode to which the active material paste is applied, for example, a metal such as aluminum or stainless steel can be used as a net, punched metal, foam metal, or a foil processed into a plate shape. .

When the lithium battery electrode of the present invention is used as a negative electrode, the active material becomes a negative electrode active material.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Examples thereof include lithium metal, graphite, and carbon materials such as amorphous carbon. A carbon material is preferable as the negative electrode active material formed of an intercalating material capable of electrochemically absorbing and desorbing lithium without deposition of dendrite-like lithium which causes a short circuit defect or the like.

The active material paste preferably contains a binder and the like, if necessary, in addition to the negative electrode active material.

The binder has a function of binding the active material particles. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as polyvinylidene fluoride (PVDF), polyvinylidene chloride, and polytetrafluoroethylene (PTFE). You can

As the current collector of the negative electrode, for example, a net, punched metal, foam metal or a foil processed into a plate shape of copper or nickel can be used.

Furthermore, the lithium battery electrode of the present invention comprises:
It is preferable that the current collector and the active material mixture layer are compressed after the active material mixture layer is formed. By compressing,
The density of the active material mixture layer is improved and the distance between the active material particles is shortened.

In the lithium battery electrode of the present invention, since cellulose having a large molecular weight is used as a binder, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result,
In the lithium battery electrode of the present invention, the movement of lithium ions is not obstructed, and the low temperature output is improved when the battery is formed.

(Third Invention) (Production Method) A method for producing a positive electrode for a lithium battery according to the present invention comprises a step of preparing an active material paste containing at least an active material, water, and a binder, and In the method for producing an electrode for a lithium battery, which comprises a step of applying an active material paste on the surface and drying, the binder has cellulose having a weight average molecular weight / number average molecular weight of 5 or more.

At least an active material, water, a binder,
In the step of preparing an active material paste having the above, an active material paste using water as a solvent is prepared.

The active material paste is applied to the surface of the current collector,
By the step of drying to form the active material mixture layer, the active material mixture layer is formed on the surface of the current collector to form the lithium battery electrode.

That is, according to the manufacturing method of the present invention, an active material paste is prepared, and the prepared active material paste is applied to the surface of a current collector and dried to manufacture a lithium battery electrode. In addition, in the manufacturing method of the present invention, an active material paste having a binder and an active material is prepared and dried to obtain an active material having a surface coated with the binder.

The binder has a weight average molecular weight / number average molecular weight of 5 or more. When the binder has a weight-average molecular weight / number-average molecular weight of 5 or more, the manufactured lithium battery electrode is suppressed in inhibition of migration of lithium ions of the active material, and thus the lithium battery electrode Low temperature characteristics are improved. Here, the weight average molecular weight and the number average molecular weight are defined by the above-mentioned formula 1 and formula 2.

Specifically, cellulose having a weight average molecular weight / number average molecular weight of 5 or more is a mixture of cellulose molecules having various molecular weights. Therefore, when the surface of the active material is covered with this cellulose, a gap is formed between the cellulose molecules due to the difference in the molecular weight and the nonuniformity of the molecular structure. When a gap is formed in the binder cellulose, the electrode becomes an electrode that does not hinder the transfer of lithium ions to the active material, and a battery having excellent low temperature characteristics can be obtained.

The weight average molecular weight / number average molecular weight generally indicates the broadening of the molecular weight distribution of the polymer. It is known that when the molecular weight distribution has a spread, the weight average molecular weight is always larger than the number average molecular weight, and the wider the spread, the wider the difference between the weight average molecular weight and the number average molecular weight. Therefore, when the weight average molecular weight / number average molecular weight increases, the molecular weight distribution becomes wider.

Cellulose is not limited as long as it can be used as a binder.
Since the production method of the present invention uses water as a solvent to prepare an active material paste, the binder is required to be a water-soluble polymer. Examples of water-soluble celluloses include carboxymethyl cellulose (CMC), hydroxyl cellulose, and methyl cellulose.

The binder preferably has a water-soluble polymer having a molecular weight different from that of cellulose. By having a water-soluble polymer having a different molecular weight from that of cellulose, the gap between the binders coated with the active material increases. That is, by arranging the water-soluble polymers having different molecular weights, the steric hindrance between the molecules constituting the binder is increased, and a gap is formed on the surface of the active material.

Examples of the water-soluble polymer include not only cellulose but also water-soluble polymers such as polyethylene oxide (PEO), ethyl cellulose, polyvinyl alcohol and polyacrylate.

Further, it is preferable that the binder has a resin dispersed in water. Examples of the resin dispersed in water include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)
Examples thereof include water-dispersion type resins having excellent organic solvent resistance such as fluorine-based resins such as, acrylic resins, olefins such as polyethylene and polyolefin, and polyimide resins.

The method for producing the electrode for a lithium battery of the present invention is not particularly limited, except that the binder contains cellulose. That is, as the material forming the active material paste, the material used in the conventional production of electrodes for lithium batteries can be used.

The production method of the present invention can be applied to the production of positive electrodes and negative electrodes. Furthermore, it is more effective if both the positive electrode and the negative electrode manufactured by the manufacturing method of the present invention are applied to a battery. The lithium battery electrode manufactured by the manufacturing method of the present invention is more preferably a lithium battery positive electrode.

When the manufacturing method of the present invention is applied to the positive electrode, the active material becomes the positive electrode active material.

The positive electrode active material is LiMexOy (Me; N
i, Co, transition metal containing at least one of Mn, x,
y; arbitrary) is preferable. This LiMexOy
Is not particularly limited. For example, LiMn
A compound having O ₂ , LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ as a main skeleton and substituted with various metal elements can be used.

LiMn ₂ O ₄ system, LiCoO ₂ system, Li
A NiO ₂ -based positive electrode active material is more preferable. That is, since it has excellent performance as a positive electrode active material such as excellent diffusion performance of electrons and lithium ions, a lithium battery having high charge / discharge efficiency and good cycle characteristics can be obtained. Further, it is preferable to use a LiMn ₂ O ₄ -based positive electrode active material because of low material cost.

The active material paste preferably contains a conductive material. Since the active material paste has the conductive material, the characteristics of the manufactured positive electrode are improved.

The conductive material ensures the electric conductivity of the positive electrode.
As the conductive material, for example, carbon black, acetylene black, a carbon material such as graphite, or a mixture of two or more carbon materials can be used.

As the current collector for the positive electrode to which the active material paste is applied, for example, a metal such as aluminum or stainless steel can be used as a net, punched metal, foam metal or a foil processed into a plate shape. .

When the manufacturing method of the present invention is applied to a negative electrode, the active material becomes a negative electrode active material.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Examples thereof include lithium metal, graphite, and carbon materials such as amorphous carbon. A carbon material is preferable as the negative electrode active material formed of an intercalating material capable of electrochemically absorbing and desorbing lithium without deposition of dendrite-like lithium which causes a short circuit defect or the like.

The active material paste preferably contains a binder and the like, if necessary, in addition to the negative electrode active material.

The binder has a function of binding the active material particles. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as polyvinylidene fluoride (PVDF), polyvinylidene chloride, and polytetrafluoroethylene (PTFE). You can

As the current collector for the negative electrode, for example, a net, punched metal, foam metal or a foil processed into a plate shape of copper, nickel or the like can be used.

Further, in the method for producing an electrode of the present invention, it is preferable to compress the current collector and the active material mixture layer after the active material mixture layer is formed. The compression improves the density of the active material mixture layer and shortens the distance between the active material particles.

In the method for producing an electrode for a lithium battery of the present invention, since the binder has cellulose having a wide molecular weight distribution, when the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions is not hindered and the low temperature output is improved.

(Lithium Battery Positive Electrode) In the lithium battery electrode of the present invention, a step of preparing an active material paste containing at least an active material, water, and a binder, and the active material paste on the surface of the current collector. Applying and drying,
An electrode for a lithium battery, which is obtained by performing the method for producing an electrode for a lithium battery having, wherein the binder comprises cellulose having a weight average molecular weight / number average molecular weight of 5 or more.

In the step of preparing an active material paste containing at least an active material and water, an active material paste using water as a solvent is prepared.

By the step of applying the active material paste on the surface of the current collector made of Al and drying it to form the active material mixture layer, the active material mixture layer is formed on the surface of the current collector, and the lithium battery It becomes an electrode for.

That is, the electrode for a lithium battery of the present invention is manufactured by preparing an active material paste, applying the prepared active material paste on the surface of a current collector, and drying it. Further, in the lithium battery electrode of the present invention, an active material paste having a binder and an active material is prepared and dried to obtain an active material having a surface coated with the binder.

The binder has a weight average molecular weight / number average molecular weight of 5 or more. Since the binder has cellulose having a weight average molecular weight / number average molecular weight of 5 or more, the manufactured lithium battery electrode suppresses inhibition of movement of lithium ions of the active material, and a battery using the lithium battery electrode. The low temperature characteristics of are improved. Here, the weight average molecular weight and the number average molecular weight are defined by the above-mentioned formula 1 and formula 2.

Specifically, cellulose having a weight average molecular weight / number average molecular weight of 5 or more is a mixture of cellulose molecules having various molecular weights. Therefore, when the surface of the active material is covered with this cellulose, a gap is formed between the cellulose molecules due to the difference in the molecular weight and the nonuniformity of the molecular structure. When a gap is formed in the cellulose of the binder, it becomes a positive electrode in which the movement of lithium ions to the active material is not hindered, and a battery having excellent low temperature characteristics can be obtained.

The cellulose is not limited as long as it can be used as a binder.
The lithium battery electrode of the present invention, in the manufacturing process,
Since the active material paste is prepared using water as a solvent, the binder is required to be a water-soluble polymer. Examples of water-soluble celluloses include carboxymethyl cellulose (CMC), hydroxyl cellulose, and methyl cellulose.

The binder preferably has a water-soluble polymer having a molecular weight different from that of cellulose. By having a water-soluble polymer having a different molecular weight from that of cellulose, the gap between the binders coated with the active material increases. That is, by arranging the water-soluble polymers having different molecular weights, the steric hindrance between the molecules constituting the binder is increased, and a gap is formed on the surface of the active material.

Examples of the water-soluble polymer include not only cellulose but also water-soluble polymers such as polyethylene oxide (PEO), ethyl cellulose, polyvinyl alcohol and polyacrylate.

Further, it is preferable that the binder has a resin dispersed in water. Examples of the resin dispersed in water include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)
Examples thereof include water-dispersion type resins having excellent organic solvent resistance such as fluorine-based resins such as, acrylic resins, olefins such as polyethylene and polyolefin, and polyimide resins.

The lithium battery electrode of the present invention is not particularly limited except that the binder contains cellulose. That is, as a material forming the active material paste, a material used for manufacturing a conventional positive electrode for a lithium battery can be used.

The lithium battery electrode of the present invention can be applied to a positive electrode and a negative electrode. Further, the lithium battery electrode of the present invention is more effective if both the positive electrode and the negative electrode are applied to the battery. The lithium battery electrode of the present invention is more preferably a lithium battery positive electrode.

When the lithium battery electrode of the present invention is used as a positive electrode, the active material becomes a positive electrode active material.

The positive electrode active material is LiMexOy (Me; N
i, Co, transition metal containing at least one of Mn, x,
y; arbitrary) is preferable. This LiMexOy
Is not particularly limited. For example, LiMn
A compound having O ₂ , LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ as a main skeleton and substituted with various metal elements can be used.

LiMn ₂ O ₄ system, LiCoO ₂ system, Li
A NiO ₂ -based positive electrode active material is more preferable. That is, since it has excellent performance as a positive electrode active material such as excellent diffusion performance of electrons and lithium ions, a lithium battery having high charge / discharge efficiency and good cycle characteristics can be obtained. Further, it is preferable to use a LiMn ₂ O ₄ -based positive electrode active material because of low material cost.

The active material paste preferably has a conductive material. Since the active material paste has the conductive material, the characteristics of the manufactured positive electrode are improved.

The conductive material ensures the electric conductivity of the positive electrode.
As the conductive material, for example, carbon black, acetylene black, a carbon material such as graphite, or a mixture of two or more carbon materials can be used.

As the current collector of the positive electrode to which the active material paste is applied, for example, a metal such as aluminum or stainless steel can be used as a net, punched metal, foam metal or a foil processed into a plate shape. .

When the lithium battery electrode of the present invention is used as a negative electrode, the active material becomes a negative electrode active material.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Examples thereof include lithium metal, graphite, and carbon materials such as amorphous carbon. A carbon material is preferable as the negative electrode active material formed of an intercalating material capable of electrochemically absorbing and desorbing lithium without deposition of dendrite-like lithium which causes a short circuit defect or the like.

The active material paste preferably contains a binder and the like, if necessary, in addition to the negative electrode active material.

The binder has a function of binding the active material particles. As the binder, an organic binder or an inorganic binder can be used, and examples thereof include compounds such as polyvinylidene fluoride (PVDF), polyvinylidene chloride, and polytetrafluoroethylene (PTFE). You can

As the current collector of the negative electrode, for example, a net, punched metal, foam metal or a foil processed into a plate shape of copper, nickel or the like can be used.

Furthermore, the lithium battery electrode of the present invention comprises:
It is preferable that the current collector and the active material mixture layer are compressed after the active material mixture layer is formed. By compressing,
The density of the active material mixture layer is improved and the distance between the active material particles is shortened.

In the lithium battery electrode of the present invention, since the binder has cellulose having a wide molecular weight distribution, even if the binder covers the surface of the active material, a gap through which lithium ions can pass is formed. As a result, the low temperature output of the lithium battery electrode of the present invention is improved.

(Lithium Battery) The electrodes produced by the method for producing an electrode for a lithium battery of the first to third inventions and the electrode for a lithium battery of the present invention form a lithium battery in the same manner as an ordinary electrode for a lithium battery. can do.

That is, it can be manufactured by housing the positive electrode and the negative electrode together with the electrolytic solution in the battery container. The first to
When the lithium battery electrode of the third invention is used as a positive electrode or a negative electrode, an electrode used in a conventional lithium battery can be used as a counter electrode.

The electrolytic solution may be any electrolytic solution used in ordinary lithium secondary batteries, and is composed of an electrolyte salt and a non-aqueous solvent.

As the electrolyte salt, for example, LiP
F₆, LiBF_Four, LiClO_Four, LiAsF₆, LiC
l, LiBr, LiCF₃SO₃, LiN (CF₃S
O₂)₂, LiC (CF₃SO₂)₃, LiI, LiAlC
l_Four, NaClO_Four, NaBF_Four, Nal, etc.
And especially LiPF₆, LiBF_Four, LiClO_Four,
LiAsF₆Inorganic lithium salts such as LiN (SO₂C_x
F_{2x + 1}) (SO₂C_yF_{2y + 1}) Organic lithium salt represented by
Can be raised. Where x and y are 1 to 4
It represents an integer, and x + y is 3 to 8. Organic richiu
Specifically, LiN (SO₂CF₃)
(SO₂C₂F_Five), LiN (SO₂CF₃) (SO₂C
₃F ₇), LiN (SO₂CF₃) (SO₂C_FourF₉), Li
N (SO₂C₂F_Five) (SO₂C ₂F_Five), LiN (SO₂C₂
F_Five) (SO₂C₃F₇), LiN (SO₂C₂F_Five) (SO₂
C_FourF₉) Etc. Among them, LiN (SO₂C
F₃) (SO₂C_FourF₉), LiN (SO₂C₂F_Five) (SO
₂C₂F_Five) Is used as the electrolyte, it has excellent electrical characteristics.
It is preferable because

The electrolyte salt is preferably dissolved so that the concentration in the electrolytic solution is 0.5 to 2 mol / dm ³ . The concentration in the electrolyte is 0.5 mol / d
This is because if it is less than m ³ , a sufficient current density may not be obtained, and if it exceeds 2 mol / dm ³ , the viscosity will increase and the conductivity of the electrolytic solution will decrease.

The organic solvent in which the electrolyte salt is dissolved is not particularly limited as long as it is an organic solvent used in a non-aqueous electrolyte of a usual lithium secondary battery, and examples thereof include carbonate compounds, lactone compounds, ether compounds and sulfolane compounds. , Dioxolane compounds, ketone compounds, nitrile compounds, halogenated hydrocarbon compounds and the like. Specifically, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethyl carbonate, ethylene glycol diethyl carbonate, carbonates such as vinylene carbonate, lactones such as γ-butyl lactone, Ethers such as dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,4-dioxane, sulfolanes such as sulfolane and 3-methylsulfolane, dioxolanes such as 1,3-dioxolane, 4-methyl-2- Ketones such as pentanone, acetonitrile,
Examples thereof include nitriles such as pyropionitrile, valeronitrile and benzonitrile, halogenated hydrocarbons such as 1,2-dichloroethane, and other methyl formate, dimethylformamide, diethylformamide, dimethyl sulfoxide and the like. Further, it may be a mixture thereof.

Among these organic solvents, one or more non-aqueous solvents selected from the group consisting of carbonates are
It is preferable because it has excellent solubility, dielectric constant and viscosity of the electrolyte.

The lithium battery formed by using the positive electrode is
The shape is not particularly limited, and it can be used as a battery of various shapes such as a sheet type, a coin type, a cylindrical type, and a square type. It is preferable that the positive electrode and the negative electrode are formed in a sheet shape, and the wound electrode body is wound with a sheet separator interposed therebetween. Furthermore, since it is excellent in volumetric efficiency, a flat wound electrode body is more preferable.

The separator is not particularly limited as long as it is a separator used in ordinary lithium secondary batteries, and examples thereof include porous resins made of polyethylene, polypropylene and the like.

The lithium battery formed using the electrode of the present invention has excellent cycle characteristics because the cycle characteristics of the electrode are not deteriorated.

[0199]

EXAMPLES The present invention will be described below with reference to examples.

As an example of the present invention, a positive electrode for a lithium battery was manufactured.

Example 1 As Example 1, an active material paste containing a positive electrode active material, a binder and water was prepared, and the active material paste was applied onto the surface of a current collector and dried to obtain a positive electrode for a lithium battery. Was manufactured.

First, the positive electrode active material has an average particle size of 8 μm.
LiNi_0.81Co_0.16Al_0.03O ₂87 parts by weight of particles
And a carbon black having an average particle size of 50 nm as a conductive material.
10 parts by weight of particles (Denka Black HS-100)
And 1 to 2 parts by weight of the binder CMC and the binder P
1 part by weight of TFE dispersion in terms of PTFE,
Pour into 83 parts by weight of pure water to homogenize kneader
Was kneaded to prepare an active material paste.

Then, the prepared active material paste was applied to Al.
It was applied to the surface of a current collector made of foil. Here, as the Al foil, an Al foil made of 1N30-H material (Al: 99.3% or more) and having a thickness of 15 μm was used.

The active material paste was applied by coating with a comma coater on the surface of the Al foil at a basis weight of 6.4 mg / cm ^2.
It was applied on both sides. Then, it was made to pass through a furnace maintained at 80 ° C. for 2 minutes to be dried.

Then, press molding was performed at a linear pressure of 0.2 ton / cm to improve the density of the active material mixture layer.

The positive electrode of Example 1 was manufactured by the above means.

As the binder CMC, four kinds of CMC having different viscosities and weight average molecular weights were used. Four
The types of CMC are shown in Table 1. The viscosity of the 1% aqueous solution shown in Table 1 is a value measured by a B-type viscometer at a temperature of 25 ° C. The weight average molecular weight of CMC was measured by a gel permeation chromatography method (GPC method).

[0208]

[Table 1]

(Evaluation) As an evaluation of the positive electrode of Example 1, a lithium battery was manufactured and the low temperature characteristics of this lithium battery were measured.

(Manufacture of Lithium Battery) 92.5 parts by weight of graphite as a negative electrode active material, PVDF 7.5 as a binder
1 part by weight and 130 parts by weight of N-methyl-2-pyrrolidone (NMP) were added and kneaded using a homogenizer type kneader to prepare a negative electrode active material paste.

The prepared negative electrode active material paste was coated on a copper foil with a comma coater in the same manner as the positive electrode so that the weight per unit surface was 3.8 mg / cm ^2, and the paste was dried. Then, a load of 0.25 ton / cm of linear pressure is applied through a roll press machine, and the electrode density is 1.2.
An electrode was produced which was raised to 5 g / cm ³ .

The negative electrode was manufactured by the above means.

The negative electrode obtained above and the positive electrode of Example 1 were wound with a separator interposed therebetween to form a wound electrode, and this electrode was inserted into the case. At this time,
The current collecting lead was joined to the positive electrode terminal and the negative electrode terminal of the case.

The separator is a polyethylene porous film having a thickness of 25 μm, and the electrolyte is ethylene carbonate (EC) and diethylene carbonate (DEC).
1mo as an electrolyte in a solvent mixed in a volume ratio of 0:70
It was used by dissolving LiPF ₆ in l / l.

The case in which the wound electrode is housed is
It had an internal space with a diameter of 18 mm and a height of 65 mm.

After that, the electrolytic solution was injected into the case and the case was closed.

(Low temperature characteristic) The low temperature characteristic was measured by the following means.

First, after charging / discharging at room temperature up to the 25th cycle, the battery voltage was adjusted to 3.62 V, and the battery was kept in a thermostatic chamber whose internal temperature was kept at −30 ° C. Was measured.

During the charging and discharging up to the 25th cycle, the current is 2
The low current charging at C and the voltage of 4.1V and the low current discharging at the current of 2C and the voltage of 3V were repeated.

To measure the output characteristics, first set the battery to 0.1A.
The battery is charged at the current value of 10 seconds and the voltage of the battery immediately after the end of charging is measured. In addition, the battery is held for 5 minutes after the end of charging and then discharged at a low current of 0.1 A for 10 seconds, and the voltage of the battery immediately after the end of discharging is measured. Then, after the battery was held for 5 minutes after the end of discharging, the battery was charged with a current value increased by 0.1 A for 10 seconds, and the voltage of the battery immediately after the end of charging was measured. The current was increased by 0.1 A, and the output of the battery was measured up to a current value of 1 A.

More specifically, the output characteristics are measured by 0.1 A charge, measurement, hold for 5 minutes, 0.1 A discharge, 0.2 A charge,
Measurement, hold for 5 minutes, 0.2A discharge, 0.3A charge, measure, hold for 5 minutes, 0.3A discharge, ... 1A charge,
Made to be a measurement.

A graph in which the horizontal axis represents the current value obtained at each current value and the vertical axis represents the voltage was prepared, and the internal resistance of the battery was calculated from the slope. Further, the output was calculated by multiplying the current value, which is the lower limit voltage of 3V, by the lower limit voltage of 3V.

The outputs of the batteries using the positive electrodes of Samples 1 to 4 are
It is shown in FIG. In FIG. 1, the output of the battery using the positive electrode of Sample 1 was set to 1 and the output of the battery using the positive electrode of Samples 2 to 4 was shown as an output ratio. The output of the battery using the positive electrode of Sample 2 was 1.2, the output of the battery using the positive electrode of Sample 3 was 1.4, and the output of the battery using the positive electrode of Sample 4 was 1.9.

It can be seen from FIG. 1 that the output obtained increases as the viscosity of the binder CMC increases. In addition, CM whose viscosity of 1% aqueous solution is 4000 mPa · s or more
It can be seen that a high low-temperature output can be obtained by using C as the binder.

Further, it can be seen that a high low-temperature output can be obtained by using CMC having a weight average molecular weight of 1.4 million or more as a binder.

(Example 2) As Example 2, an active material paste containing a positive electrode active material, a binder and water was prepared, and the active material paste was applied onto the surface of a current collector and dried to obtain a positive electrode for a lithium battery. Was manufactured.

First, the positive electrode active material has an average particle size of 8 μm.
LiNi_0.81Co_0.16Al_0.03O ₂87 parts by weight of particles
And a carbon black having an average particle size of 50 nm as a conductive material.
10 parts by weight of particles (Denka Black HS-100)
And 1 to 2 parts by weight of the binder CMC and the binder P
1 part by weight of TFE dispersion in terms of PTFE,
Pour into 83 parts by weight of pure water to homogenize kneader
Was kneaded to prepare an active material paste.

After that, the prepared active material paste was applied to Al.
It was applied to the surface of a current collector made of foil. Here, as the Al foil, an Al foil made of 1N30-H material (Al: 99.3% or more) and having a thickness of 15 μm was used.

Application of the active material paste was carried out by using a comma coater on the surface of the Al foil at a basis weight of 6.4 mg / cm ² per surface.
It was applied on both sides. Then, it was made to pass through a furnace maintained at 80 ° C. for 2 minutes to be dried.

After that, press molding was performed at a linear pressure of 0.2 ton / cm to improve the density of the active material mixture layer.

The positive electrode of Example 2 was manufactured by the above means.

As the binder CMC, three types of CMC having different weight average molecular weight / number average molecular weight ratios were used. The three types of CMC are shown in Table 2. The weight average molecular weight and the number average molecular weight of CMC were measured by the GPC method.

[0233]

[Table 2]

(Evaluation) As the evaluation of the positive electrode of Example 2, a battery was manufactured in the same manner as in the evaluation of Example 1, and the output of the manufactured battery at low temperature was obtained.

The outputs of the batteries using the positive electrodes of Samples 5 to 7 are
It is shown in FIG. In FIG. 2, the output of the battery using the positive electrode of Sample 5 is 1 and the output of the battery using the positive electrode of Samples 6 and 7 is shown as an output ratio. The output of the battery using the positive electrode of sample 6 is 1, and the output of the battery using the positive electrode of sample 7 is 1.
It was 4.

From FIG. 2, it can be seen that high temperature output can be obtained by using CMC having a large weight average molecular weight / number average molecular weight ratio of 12.5 of the binder CMC.

Example 3 As Example 3, an active material paste containing a positive electrode active material, a binder, and water was prepared, and the active material paste was applied onto the surface of a current collector and dried to obtain a positive electrode for a lithium battery. Was manufactured.

First, the positive electrode active material has an average particle size of 8 μm.
LiNi_0.81Co_0.16Al_0.03O ₂87 parts by weight of particles
And a carbon black having an average particle size of 50 nm as a conductive material.
10 parts by weight of particles (Denka Black HS-100)
And 0.5 parts by weight of CMC of the binder and P of the binder
0.5 parts by weight of EO, binder PTFE purge
1 part by weight of PTFE to 83 parts by weight of pure water
Charge and knead using a homogenizer type kneader to activate.
A material paste was prepared.

As CMC, CMC having a 1% aqueous solution viscosity of 11000 mPa · s measured at 25 ° C. by a B-type viscometer was used. As PEO, a polymer having a number average molecular weight of 3.5 million was used.

After that, the prepared active material paste was added to Al.
It was applied to the surface of a current collector made of foil. Here, as the Al foil, an Al foil made of 1N30-H material (Al: 99.3% or more) and having a thickness of 15 μm was used.

The active material paste was applied by coating with a comma coater on the surface of the Al foil at a basis weight of 6.4 mg / cm ^2.
It was applied on both sides. Then, it was made to pass through a furnace maintained at 80 ° C. for 2 minutes to be dried.

Then, press molding was performed at a linear pressure of 0.2 ton / cm to improve the density of the active material mixture layer.

The positive electrode of Example 3 was manufactured by the above means.

The positive electrode of Example 3 is the same as the positive electrode of Sample 4 of Example 1 except that the amount of CMC was reduced and PEO was added in an amount corresponding to the reduced amount of CMC.

(Evaluation) As the evaluation of the positive electrode of Example 3, a battery was manufactured in the same manner as the evaluation of Example 1, and the output at low temperature of the manufactured battery was determined.

When the output of the battery using the positive electrode of Sample 4 of Example 1 was set to 1, the low temperature output of Example 3 was 1.2. That is, it can be seen that the low temperature output was improved by adding PEO to the binder.

[0247]

INDUSTRIAL APPLICABILITY In the electrode for a lithium battery manufactured by the manufacturing method of the present invention, a gap through which lithium ions can pass is formed by the cellulose coating the surface of the active material. As a result, in the electrode manufactured by the method for manufacturing a lithium battery electrode of the present invention, the movement of lithium ions at the active material interface is not hindered, and the low temperature output is improved when the battery is formed.

[Brief description of drawings]

FIG. 1 is a diagram showing a low temperature output ratio of a battery using the positive electrode of Example 1.

FIG. 2 is a diagram showing a low temperature output ratio of a battery using the positive electrode of Example 2.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Manabu Yamada             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Hideo Amagi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Takamasa Ogawa             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F term (reference) 5H029 AJ02 AJ14 AK03 AL06 AL07                       AL12 AM02 AM03 AM04 AM05                       AM07 CJ02 CJ08 CJ22 DJ08                       EJ12 HJ10 HJ11                 5H050 AA06 AA19 BA15 CA08 CA09                       CB07 CB08 CB12 DA11 EA23                       GA02 GA10 GA22 HA10

Claims (12)

[Claims] 1. A lithium battery comprising: a step of preparing an active material paste having at least an active material, water, and a binder; and a step of applying the active material paste to the surface of a current collector and drying the active material paste. In the method for producing an electrode for use in the method, the binder has a viscosity of 4000 mP in a 1% aqueous solution
A method for producing an electrode for a lithium battery, which comprises cellulose of a · s or more. 2. The method for manufacturing an electrode for a lithium battery according to claim 1, wherein the binder has a water-soluble polymer having a molecular weight different from that of the cellulose. 3. A lithium battery comprising: a step of preparing an active material paste having at least an active material, water, and a binder; and a step of applying the active material paste on a surface of a current collector and drying the active material paste. An electrode for a lithium battery, which has been subjected to a method for producing a battery electrode, wherein the binder has a viscosity of 4000 mP in a 1% aqueous solution.
An electrode for a lithium battery, characterized by having cellulose of a · s or more. 4. The electrode for a lithium battery according to claim 3, wherein the binder has a water-soluble polymer having a molecular weight different from that of the cellulose. 5. A lithium battery comprising: a step of preparing an active material paste having at least an active material, water, and a binder; and a step of applying the active material paste to the surface of a current collector and drying the active material paste. The method for producing an electrode for a lithium battery, wherein the binder has cellulose having a weight average molecular weight of 1.4 million or more. 6. The method for producing an electrode for a lithium battery according to claim 5, wherein the binder has a water-soluble polymer having a molecular weight different from that of the cellulose. 7. A lithium battery comprising: a step of preparing an active material paste having at least an active material, water and a binder; and a step of applying the active material paste on the surface of a current collector and drying the active material paste. An electrode for a lithium battery, which has been subjected to the method for producing a battery electrode, wherein the binder comprises cellulose having a weight average molecular weight of 1.4 million or more. 8. The electrode for a lithium battery according to claim 7, wherein the binder has a water-soluble polymer having a molecular weight different from that of the cellulose. 9. A lithium battery comprising: a step of preparing an active material paste having at least an active material, water, and a binder; and a step of applying the active material paste to the surface of a current collector and drying the active material paste. The method for producing an electrode for a lithium battery, wherein the binder comprises cellulose having a weight average molecular weight / number average molecular weight of 5 or more. 10. The method of manufacturing an electrode for a lithium battery according to claim 9, wherein the binder has a water-soluble polymer having a molecular weight different from that of the cellulose. 11. A lithium battery comprising: a step of preparing an active material paste having at least an active material, water, and a binder; and a step of applying the active material paste to the surface of a current collector and drying the active material paste. An electrode for a lithium battery, which has been subjected to the method for producing a battery electrode, wherein the binder comprises cellulose having a weight average molecular weight / number average molecular weight of 5 or more. 12. The electrode for a lithium battery according to claim 9, wherein the binder has a water-soluble polymer having a molecular weight different from that of the cellulose.