JP3405380B2 - Non-aqueous electrolyte secondary battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery in which a material capable of inserting and extracting lithium ions is used as a negative electrode active material and a lithium ion conductive non-aqueous solution is used. , High energy density and excellent charge / discharge characteristics, long cycle life, high reliability,
The present invention relates to a new secondary battery in consideration of workability of a battery assembly process.

[0002]

2. Description of the Related Art In recent years, portable electronic devices such as video cameras, portable CDs, mobile phones, PDAs and notebook computers have been reduced in size, weight and performance. As a power source for these portable electronic devices, a highly safe secondary battery having high capacity and excellent heavy load characteristics is required. Sealed lead storage batteries and nickel-cadmium storage batteries have been used as secondary batteries that meet such purposes, but nickel-hydrogen storage batteries and lithium-ion secondary batteries as non-aqueous electrolyte secondary batteries have been used as batteries with higher energy density. It has been put to practical use.

The non-aqueous electrolyte secondary battery uses an electrolyte in which a lithium salt is dissolved in a non-aqueous solvent, and the negative electrode active material is metallic lithium or an alloy of metallic lithium and another metal such as Al, Sn or Pb. The lithium secondary battery used, a lithium ion secondary battery using a carbonaceous material capable of inserting and removing lithium ions in the negative electrode active material, and the like are known. Since these non-aqueous electrolyte secondary batteries do not use water as an electrolytic solution, it is possible to design a battery that can be charged and discharged at a high voltage higher than the electrolysis voltage of water, and there is an advantage that the energy density can be easily increased. .

As a positive electrode active material for these non-aqueous electrolyte secondary batteries, oxides or chalcogenides having a one-dimensional chain structure capable of inserting and extracting lithium ions, a two-dimensional layered structure, a three-dimensional skeleton structure, an amorphous structure, or the like, or Conductive polymers and the like have been proposed. When metal lithium is used as the negative electrode active material, dendrite-shaped lithium metal crystals grown by repeating charge and discharge break through the separator, causing a short circuit between the positive and negative electrodes, which is an obstacle to practical use in terms of safety. There is. In addition, as a negative electrode active material in a non-aqueous electrolyte secondary battery, metallic lithium, Al, Sn and P are used.
When alloys with other metals such as b are used, the energy density is lower than that of metallic lithium, and the cycle characteristics are lower than when carbon materials are used as the active material. Used only in coin-type secondary batteries. Therefore, most of the negative electrode active materials of non-aqueous electrolyte secondary batteries used as the main power source of portable electronic devices use carbonaceous materials.

However, the theoretical energy density per unit weight of metallic lithium is 3861 mAh / g, whereas the theoretical energy density of a generally known carbonaceous material is 372 mAh / g. Therefore, when the carbonaceous material is used as the negative electrode active material, its weight energy density is lower than that when metallic lithium is used, and further, since the actual carbon material is high, the volume energy density is also low. .

In order to answer such a problem, the present inventors have used, as the negative electrode active material, various oxides and carbonaceous materials such as silicon, tin and transition metals capable of inserting and extracting lithium ions,
It was found that a non-aqueous electrolyte secondary battery using a composite oxide having _a composition of Li _a T _b L _c O _d as a positive electrode active material was prototyped and that a battery with high capacity and low internal resistance could be provided.
(T is one or more kinds of transition metals selected from Co, Ni, Mn, Fe, V, W, Nb, Ti, etc., L is a metal of Group IIIB or IVB of the Periodic Table, or a similar metal, At least one element selected from the group consisting of alkaline earth metals, metals such as Ti, Mn, Cu and Zn;
a, b and c are 0 <a ≦ 1.15 and 0.8 ≦ b +, respectively.
complex oxide with c ≦ 1.3 and 1.7 ≦ d ≦ 2.5)
(Japanese Patent Application No. 3-253921, 5-162958, 7)
156547).

In particular, when the negative electrode active material is silicon oxide and the composition formula is represented by LixMySiO (X ≧ 1), the theoretical energy density in the reversible charge / discharge region is 121.
It is 6 mAh / g or more. This has a theoretical energy density about three times as high as that when only the carbonaceous material is used as the negative electrode active material.

[0008]

In order to obtain a battery with excellent heavy load characteristics (large current charge / discharge characteristics), the electrode area should be as large as possible and the current required from the equipment used should be
It is effective to reduce the current density of the electrodes. To increase the area of one of the electrodes, the electrode may be thinned, but the dead space of the current collector, the separator, etc. increases, the amount of active material that can be filled in a fixed volume decreases, and the volume decreases. In order to store the electrode in a predetermined volume while ensuring a large area of the electrode, a method of dividing the electrode in a state of having an electrical connection and laminating with a separator is proposed. Current tends to concentrate at the end of the cut, and dendrite of lithium may grow at the end of the electrode due to repeated charging / discharging of the battery, which poses a problem in battery safety and the like.

Further, considering the theoretical energy density per unit weight shown above, comparing the theoretical energy density per unit volume when a carbon material is used as the negative electrode material and when a silicon oxide is used, When graphite is used as the carbon material and SiO is used as the silicon oxide, the densities are 2.25 g / cc and 2.24 g, respectively.
Since / cc, the theoretical energy density per unit volume is three times or more higher when silicon oxide is used.
That is, in comparison with the case where only a carbonaceous material capable of occluding and releasing lithium ions is used for the negative electrode active material, in the negative electrode using silicon oxide, the thickness of the negative electrode facing the positive electrode of the same volume and the same area is Although it can be increased to about 1/3 to 1 times, there is a problem that productivity is significantly lowered in order to secure the accuracy such as the electrode thickness required for battery performance in the battery manufacturing process due to the thin electrode. is there.

Therefore, in order to improve the characteristics at the time of discharging and charging at a large current required for a practical battery, a battery structure and a manufacturing method with higher productivity are required.
Further, a substance capable of occluding and releasing lithium ions generally cannot release 100% of occluded lithium ions, and has an irreversible capacity. If a real battery is assumed, the battery capacity corresponding to the irreversible capacity will decrease.

[0011]

In order to solve the above problems, the present invention provides a non-aqueous electrolyte secondary battery comprising at least a strip-shaped positive electrode, a strip-shaped negative electrode and a lithium ion conductive non-aqueous electrolyte. The structure is such that a strip-shaped positive electrode and a strip-shaped negative electrode are spirally wound to be used as a wound electrode group.
Therefore, the electrode area per sheet can be increased, and the characteristics at the time of discharging and charging with a large current can be improved. Furthermore, since the number of parts in the actual battery configuration can be reduced, it is possible to improve the productivity and yield in the battery manufacturing process and reduce the manufacturing cost. When winding the electrode, the positive electrode and / or the negative electrode is wound while being heated. This allows easy and uniform winding. Furthermore, by spirally winding together with metallic lithium, a lithium alloy, and a substance capable of releasing lithium, lithium corresponding to the irreversible capacity of the substance capable of absorbing and releasing lithium ions can be supplied.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The positive and negative electrodes are arranged so as not to come into contact with each other via a separator, and a winding core to be wound is rotated to wind the electrodes and the separator in a spiral shape. Thus, a wound electrode group can be manufactured. At least one of the electrodes may be bent once or more.

A general method can be used for supplying the positive and negative electrodes and the separator to the winding core. For example, it is continuously supplied in the form of a reel, and the electrode is cut into a predetermined length during or after the winding operation. Alternatively, it is possible to cut the electrode or separator into a predetermined length in advance, supply it, and wind it. It is preferable that the electrode and the separator to be supplied are supplied while applying a load in the winding direction because the adhesion of the electrode can be obtained during the winding.

At the time of winding, at least one of the electrodes is arranged so that the core of the winding machine is located at the center of the winding direction, or one end of the electrode is the winding direction of the winding machine. It can be arranged so as to face the winding core. Moreover, both ends of the positive and negative electrodes in the hand direction may face the same direction, but the positive and negative electrodes may be arranged so that the ends in the hand direction face each other.

The separator can be arranged similarly to the electrode.
However, the separator does not necessarily need to be supplied and wound with a sheet using the above-mentioned material, and includes a case where it is chemically or physically formed on at least one of the electrodes so as to exert the function of the separator. .

At the time of winding, the positive and negative electrodes are placed on the winding core with the electrode and / or the separator interposed therebetween, and the winding is performed. At that time, the end points of the electrodes in the longitudinal direction and the end points of the winding core can be aligned. It is also possible to use it as a lead of one of the electrodes without pulling out the winding core after winding. When the winding core also serves as the lead, the winding core and the electrode may be electrically connected, but the lead and the electrode are preferably welded by a general method.

When the core is drawn out without leaving it inside the spirally wound electrode group after winding, a contact resistance is generated between the core and the electrode when the core is drawn out, so that a winding deviation easily occurs and the electrode mixture is peeled off. The peeled mixture may cause a short circuit. Therefore, the winding deviation is prevented by arranging the separator so as to contact the winding core and then starting winding so that the electrode does not directly contact the winding core.

Further, the contact between the separator and the winding core may cause cracking, cutting, and abrasion of the separator to lower the strength and cause insulation failure.
It is preferable to wind it twice or more. The shape of the winding core used when spirally winding the positive electrode and the negative electrode may be a perfect circle, but an ellipse, a rectangle, a rhombus, or other polygons or their corners are chamfered. It may have a shape as described above. The material of the winding core is not particularly limited, but stainless steel is preferable. The winding core does not necessarily have to be composed of a single component, and may have a structure divided into a plurality of components.

In particular, an electrode electrochemically doped with lithium tends to be hard, which causes a problem such as separation from the current collector when the electrode is wound, and the separated electrode material penetrates the separator. In addition, since it causes a short circuit between the electrodes, it is possible to prevent them by supplying the electrodes while heating or keeping the temperature and spirally winding the electrodes. At this time, heating is performed at 40 ° C. or higher and within a range that does not affect the material of the separator. The preferable heating temperature depends on the material of the separator, but when polyethylene or polypropylene is used, for example, 40 to 80 ° C is preferable, and 40 ° C to 60 ° C is particularly preferable.

The positive and negative electrodes are spirally wound, and when winding is completed, the entire outer circumference or a part of the outermost circumference of the electrode or the separator located at the outermost circumference of the wound electrode group is fixed. When the separator is made of a material whose outermost periphery is particularly heat-melted, the separator can be directly fixed by heat welding.
Further, in order to fix the outermost circumference, an adhesive tape or a rectangular tubular fixing tape can be used. When a heat resistant material is used for the separator, a heat shrinkable tube can be used at the outermost circumference. Also, the outermost circumference is an electrode,
If the electrical connection is maintained and fixed to the outer case, it is not necessary to provide positive and negative terminals, respectively. In that case, it is desirable to use an electronically conductive material in order to make an electrical connection advantageous.

By fixing these, the deviation of the winding in the vertical direction with respect to the winding of the electrode and the looseness of the winding in the winding direction can be suppressed to the minimum to prevent the deterioration of the performance of the battery, and the fallen material causes a short circuit between both electrodes. It is possible to prevent this, facilitate the transportation to the next step using the wound electrode body, and easily insert the wound electrode body into the outer case.

It is necessary that the portions between the electrodes and the portions having the electrical connection with the respective electrodes are electrically isolated from each other.
As a method of performing electrical isolation, a portion other than those having electrical connection is subjected to insulation treatment or spatial isolation. Examples of the portion other than the portion having the electrical connection include the surface of the electrode terminal, the lead between the strip electrode and the electrode terminal, the battery sealing lid, the inner surface of the battery outer case, and the like.

Further, the leads are reinforced against mechanical external force. The adhesive tape is preferable because it can have both the functions of insulating treatment and reinforcement. If the active material of the positive electrode or the negative electrode is exposed to a state in which the active material exceeds the potential region in which it can stably exist, such as over-discharge or over-charge, the decomposition reaction of the active material itself or the decomposition reaction of the electrolytic solution may occur. A reaction occurs. Therefore, it is necessary to design and control the amount of active material in consideration of the balance so that each electrode maintains an appropriate charge / discharge capacity.

As a measure against the over-discharge, in order to cover the entire surface facing the positive electrode with the negative electrode, a negative electrode longer than the positive electrode in the spiral winding direction is used. Also, in any step of winding the electrodes in a spiral shape to produce a wound electrode group, removing the winding core from the wound electrode group, and further putting the wound type electrode group in the outer case, there is a winding deviation. If there is a portion where both electrodes do not face each other due to the winding deviation that occurs, the current concentrates or disperses only in that portion, so the electrode may partially over discharge or There is a possibility of overcharge, and the same side reaction as above occurs. Therefore, by using a negative electrode having a spiral winding width wider than that of the positive electrode, even if some winding deviation occurs, the widened portion can absorb the deviation. Therefore, it is necessary to make the negative electrode area larger than the positive electrode area for the above reason.

Further, it is necessary to avoid short-circuiting between the electrodes or a portion having an electrical connection between the electrodes and an outer case, and the separator needs to be larger than the area of at least one of the electrodes. When the cross-sectional shape of the outer case is circular, the spirally wound electrode group using a circular core can be finished to have a circular cross-sectional shape like the winding core. Can be directly inserted into the outer case. However, the cross-sectional shape of the outer case, which is generally called a rectangular type, is rectangular, and the wound electrode group formed by using the circular core cannot be inserted into the outer case as it is. Therefore, the spirally wound wound type electrode group used in the present invention is applied with an external force such as compression in accordance with the cross-sectional shape of the outer case to be used, and after the wound type electrode group having a predetermined shape is formed, the outer case is attached to the outer case. Can be inserted. For example, when a winding core having a rectangular cross section is used, the cross sectional shape of the spirally wound electrode group tends to be elliptical due to the elasticity of the electrode. The wound electrode group thus formed can be inserted into the outer case as it is, but voids are formed at the four corners of the outer case, and the space utilization rate of the outer case is reduced. In this case, the wound electrode group can be deformed from an elliptical shape to a quadrangular shape by performing compression from the two-handed direction according to the cross section of the outer case. In addition, the jig for compression processing is composed of multiple parts, and the entire circumference or part of the direction of the wound electrode group should be divided simultaneously or multiple times, and compression processing should be performed once or more. You can Further, it is preferable to process the wound electrode group during compression processing while heating or keeping the temperature at an appropriate temperature for the same reason as when winding the electrodes. In addition to the method of heating and retaining heat, a method in which a heater is incorporated in the compression jig and the surface in contact with the wound electrode group is preheated can be used in combination with the method of heating and heat retention.

As a constituent element of the wound electrode group, a current collector,
It is necessary to provide an electrode mixture, a separator, a lead, etc. for each electrode. If necessary, metallic lithium or the like, an insulating tape for leads, or the like is used. When used as a battery, it is necessary to further include a battery sealing lid, a battery outer case, and electrode terminals.

If the outer case and the battery sealing lid are made of metal and the joints thereof are fixed while maintaining electrical connection by, for example, laser welding, it is not necessary to provide positive and negative terminals to the battery sealing lid. . When the battery outer case also serves as the current collector of the electrode, the outer case can also serve as the lead.

A plurality of wound electrode groups can be inserted into the outer case at the same time. The material of the current collector of the electrode is preferably a metal or metal alloy that does not react with the electrolyte, lithium or the like and has electronic conductivity. In particular, the positive electrode current collector is preferably aluminum or an alloy containing aluminum, and the negative electrode current collector is preferably copper or an alloy containing copper.

The method of manufacturing the current collector is not particularly limited, such as rolling or electrolytic foil forming. The shape of the current collector is preferably a foil or thin plate of metal or metal alloy, but a thin flat plate such as expanded metal that has been machined in advance or a cloth or net made of metal fiber, metal It may be a foam or a porous body.

In the process of manufacturing the electrode, in order to improve the adhesion between the current collector and the electrode material, the entire surface or a part of the surface of the current collector is specially processed by sandblasting or roughening the surface. Processing by rolling etc., sputtering using ion beam or photon other than electron beam or ion implantation processing or treatment, or
It may be subjected to a chemical treatment using a chemical agent such as an acid or a base, and particularly when the current collector is produced by rolling, it is particularly preferable to produce the surface as described above. In addition, if a metal material is used on the surface of a material that can be plastically deformed, such as metal, plastic, or polymer such as rubber, plating,
Those produced by vapor deposition, thermal spraying, etc. are also directly or indirectly electrically connected to the electrode active material, and are included as a current collector if they have a current collecting function. For example, even if the electrodes are formed on the battery case, the battery case may function as a current collector. Alternatively, a material containing an electrode active material that does not have a band-shaped current collector may be prepared in advance, and the current collector may be formed on the electrode itself by some method to form an electrode.

As an example of the surface treatment of the current collector, the adhesion between the current collector and the electrode material, the electron conductivity, the smoothness of the electrode current collector when the electrode mixture is applied, and the uneven coating are suppressed. In order to do so, a conductive carbon or metal filler and a binder are dispersed on the surface of the current collector by adding water or a non-aqueous solvent to prepare a slurry-like paste, and a certain method is applied on the current collector. It may be used after being applied with, dried, and compression molded.

In the negative electrode mixture, in addition to the negative electrode active material, a filler such as carbon, a metal or a metal alloy is added as a conduction aid for imparting electron conductivity, or the active material and the current collector or the electron conductivity imparting substance is added. A binder may be added for the purpose of maintaining an electrical connection with and maintaining the molded shape. It is not always necessary to use both the conductive auxiliary agent and the binder as the electrode mixture at the same time.

The negative electrode mixture contains at least a negative electrode active material,
The negative electrode active material is preferably a carbonaceous material capable of inserting and extracting lithium ions and / or an oxide of one or more elements selected from IIIB and IVB of the periodic table and a transition metal, particularly an oxide of silicon. Oxides of silicon _{Li x M y Si 1-y} O z
Represented by the following composition formula, and the lithium content x is 0 ≦ x,
The substitution amount y of silicon is 0 ≦ Y <1, and particularly excellent battery characteristics are exhibited when 0 ≦ z ≦ 4. Substitution element M of silicon is one or more elements selected from metals and non-metals except lithium and silicon, and examples thereof include alkali metals such as sodium, potassium and rubidium, and alkaline earth metals such as magnesium and calcium. Metal and / or iron, nickel, cobalt, manganese, vanadium, titanium, niobium, tungsten, molybdenum, copper, zinc, tin, lead,
A metal such as aluminum, indium, bismuth, gallium, germanium, carbon, boron, nitrogen, phosphorus, etc., or a semimetal or nonmetal is desirable. It is more preferable that the carbonaceous material becomes an active material that doubles as a conductive agent and has a large capacity.

As the positive electrode active material used in the present invention,
Metal chalcogenides such as TiS ₂ , MoS ₂ and NbSe ₃ , as well as MnO ₂ and M
Metal oxides such as oO ₃ , V ₂ O ₅ , LixCoO ₂ , LixNiO ₂ and LixMn ₂ O ₄ , conductive polymers such as polyaniline, polypyrrole, polyparaphenylene and polyacene, and lithium ions such as graphite intercalation compounds and / or Various substances that can store and release anions can be used.

In particular, the composition of the positive electrode active material is Li _a T _b L _c
Od , T is Co, Ni, Mn, Fe, V, W,
One or more kinds of transition metals selected from Nb, Ti, etc., L is one or more kinds of elements selected from B, Si, P, Mg, Zn, and Cu, and a, b, c is 0 <a, 0.8 ≦ b + c ≦ 1.3, 1.7 ≦ d ≦, respectively
A (noble) active material having a high potential of 3 V to 4 V or more such as a complex oxide of 2.5 and a (base) active material having a low potential of 1 V or less with respect to metallic lithium described later. By combining with the used negative electrode,
It is more preferable because a secondary battery having a high energy density can be obtained.

The silicon oxide represented by the composition formula of Li _x M _y Si _1-y O _z synthesized in advance is used as it is, or mechanically or chemically if necessary, mechanically or chemically pulverized or granulated, and further processed such as granulation. It may be used for producing an electrode after being subjected to.
Strip positive electrode and _{Li x M y Si 1-y} o negative electrode of preparation containing an active material substance of the formula with the composition of _z it is may be preferable four ways.

The first method is to prepare a strip-shaped negative electrode using a negative electrode active material containing a silicon oxide represented by a composition formula of Li _x M _y Si _1-y O _z , and prepare the negative electrode and the strip-shaped positive electrode. And a method of producing a non-aqueous electrolyte secondary battery using a wound-type electrode group that is wound in a spiral shape through a separator.

The second method is a lithium-free lower oxide of silicon M _y Si _1-y O _z (where 0 ≦ y <0, 0 <
z ≦ 4) is used to prepare a strip-shaped negative electrode, and the negative electrode or the positive electrode is placed in contact with metal lithium or an alloy of lithium in a laminated manner, and the strip-shaped positive electrode or the negative electrode is respectively interposed via a separator. A method for producing a non-aqueous electrolyte secondary battery using a spirally wound electrode group.

The third method is to manufacture a strip-shaped electrode using a lithium-free lower oxide of silicon M _y Si _1-y O _z (where 0 <z ≦ 4), and further, before winding. electricity electrodes chemically perform doping of _{lithium, Li x M y Si 1-} y O z
A band-shaped negative electrode is prepared using a negative electrode active material containing a silicon oxide represented by the compositional formula, and the positive electrode and the negative electrode are non-aqueous using a spirally wound electrode group that is spirally wound through a separator. A method for manufacturing an electrolyte secondary battery.

In the second method, it is desirable that a metallic lithium or an alloy of lithium be attached to at least one of the electrodes in advance by a step of laminating the metallic lithium or the like, and then it is wound via a separator.
It is also possible to supply the lithium or the like at the same time as the positive and negative electrodes and wind them. The step of adhering the lithium may be arranged before or after forming the electrode as long as it is before the step of spirally winding the electrode.

Lithium metal or lithium used in the present method
Aluminum alloy is pasted or supplied as foil or thin plate
It is preferable from the viewpoint of workability, but the cross section is round or polygonal.
It is also possible to use a thin wire or the like, and the shape is not restricted.
In addition, a thin plate or rod-shaped small piece of the lithium is previously prepared.
After cutting out or molding, stick it to the electrode
They may be arranged side by side. The thickness of the lithium used is
Although not particularly limited, it is preferably 60 μm or less
And more preferably 20 μm or less. The re
Titanium is attached or supplied so as to cover the entire electrode.
Is more preferable, but keeps electrical connection with some of the electrodes
It should be arranged like this. Stuck the lithium
After that, by adding pressure or heat energy, the lithium is
It is also possible to change to a preferable thickness or area. This
Here, the lower oxide of silicon MySi _1-yO_zEven a little
The surface potential of metallic lithium becomes steep when it contains thium.
It drops sharply, M_ySi_1-yO_zOf lithium ion in the atmosphere
Driving force that causes science diffusion is significantly reduced
To do. Therefore, metallic lithium should be arranged as evenly as possible.
There is a need to. As a method, the lithium is in a solid state.
Not in the molten or gaseous or ionized state
It is preferable to use and arrange as uniformly as possible.

Before the wound type electrode group is inserted into the battery case, the wound type electrode group is directly immersed outside the battery case in an electrolytic solution used in the battery assembly or an electrolytic solution different from the electrolytic solution used to form the wound type electrode. It is also possible to form a kind of local battery within the group and self-discharge to electrochemically occlude lithium into the lower oxide of silicon represented by the composition formula of M _y Si _1-y O _z . It is preferable that the wound electrode group is inserted into the battery case and then the electrolytic solution is added to the battery case to cause the above reaction so that the battery is easily assembled and the productivity is high.

In the third method, a lithium-free lower oxide of silicon M _y Si _1-y O _z (where 0 <Z
The method for producing a strip-shaped electrode using ≦ 4) is the same as the above-mentioned second method. This electrode is used as a working electrode, and metallic lithium or a substance containing lithium is used as a counter electrode in contact with a lithium ion conductive non-aqueous electrolyte to make both electrodes face each other to form an electrochemical cell. A lithium current is electrochemically absorbed in the lower oxide of silicon by applying an appropriate current in the direction of causing a reaction. The obtained working electrode is directly used as a negative electrode to form a non-aqueous electrolyte secondary battery. Preferably, the workability of winding can be improved by removing the non-aqueous electrolyte solution on the electrode before winding. Second those immersed in electrolytic solution said electrode bonding the lithium obtained by the process also Li _x M _y Si
A silicon oxide represented by the compositional formula of _1-y O _z can be obtained, and when the electrode is spirally wound, an electrode in a state substantially similar to that of the third method is used. Means to use.

The advance winding turn, after winding using electrochemical techniques and n- butyl lithium or the like described above Li _x M _y Si
It is also possible to obtain a silicon oxide represented by a composition formula of _1-y O _z . A fourth method uses the lower oxide of silicon as a negative electrode active material, and a material that can store and release lithium ions containing lithium as a positive electrode active material to prepare strip-shaped negative electrodes and positive electrodes, and vortex them through a separator. A non-aqueous electrolyte secondary battery is wound into a wound electrode group. Lithium ions released from the positive electrode by being charged when used as a battery are occluded in the lower oxide of silicon. The method used in the first method can be appropriately used for each of the positive and negative electrodes.

As the binder of the mixture, a dispersion of polytetrafluoroethylene (PTFE) or a fluororesin such as polyvinylidene fluoride (PVdF) can be used. The fluororesin is stable to the electrolytic solution and has excellent heat resistance. In particular, PVdF, which is the only solution among fluororesins, can be used as a solution and is often used because of its good coating property in the process of manufacturing an electrode in which a mixture slurry is coated on a current collector. As the water-soluble polymer, various polymers such as natural polymer and synthetic resin can be used. For example, as the natural product type, starch type starch, modified starch, dextrin, cellulose type methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose (CMC), rubber type gum arabic, tragacanth gum, karaya gum, locust bean gum, guar gum, etc. can give. For synthetic resin systems, polyvinyl alcohols, polyacrylamides, polyethylene oxides, polyvinylpyrrolidone, vinyl acetate copolymers,
An acrylic acid polymer or the like can be used. Above all,
Acrylic acid polymers, CMC and the like are preferable because they have good binding property to metals such as aluminum and copper to current collectors. Further, it is effective to use a cross-linked acrylic acid polymer in order to enhance the binding property. In particular, the content of carboxyl group in the crosslinked acrylic acid polymer is preferably 50 to 70%. One of these water-soluble polymers can sufficiently function, but two or more of them may be mixed and used.

The electrode is manufactured by mixing the negative electrode active material containing the silicon oxide with the conductive auxiliary agent and / or the binder, and adding water or a non-aqueous solvent to disperse the negative electrode mixture into a slurry. Apply it on the current collector by some method and dry it.
An electrode can be produced by compressing and molding into a predetermined size.

The drying method for drying the electrodes is preferably hot air, but infrared rays including the far infrared region, low humidity air, centrifugal force and vacuum may be used alone or in combination. And the method of applying the electrode mixture onto the current collector is not limited thereto. Spin coating method, doctor blade method, reverse roll method, direct roll method, dip method, squeeze method, extrusion method, curtain method, bar Examples of the method include a knife method and a knife method, but the method is not limited thereto.

The silicon oxide layer may be formed by a method such as vacuum deposition or high frequency sputtering to prepare an electrode. An electrode can be produced by synthesizing this silicon oxide on a current collector using a technique such as plasma CVD. The last part of the wound electrode can be fixed with a tape resistant to the non-aqueous electrolyte. For example, a material having metal foil, glass cloth, polyethylene, polypropylene, polyolefin, polyimide, Teflon, silicone rubber or the like as a base material can be used as an example. Further, when an adhesive is used for the fixing tape, the material of the adhesive is required to have chemical resistance in a non-aqueous solution, and an acrylic or rubber material is preferable. Further, a heat fusion material or a heat shrink material can be used.

A separator is used between each electrode to separate the positive electrode and the negative electrode, and each electrode is wound via the separator. The material of the separator is preferably polypropylene or polyethylene, but is not limited to these polymer materials. Porous materials such as non-woven fabrics or lithium ion permeable microporous polymer films, using these materials alone or in a mixed weave, or with one of the materials coated with the other It is preferable to use the above condition. A case where a polymer solid electrolyte, an inorganic solid electrolyte or the like described later also functions as a separator is also included. The solid polymer electrolyte is not limited to be in a solid state at room temperature, and may be rubber-like or gel-like. The above-mentioned polymer material may be used in combination with the polymer solid electrolyte or the inorganic solid electrolyte.

The electrolytic solution is prepared by mixing an aprotic polar solvent represented by heterocyclic compounds, chain ethers, glycol ethers, chain carbonates, and other organic solvents, alone or in combination of two or more kinds. LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO as a supporting salt in a certain solvent
₃ , non-aqueous electrolytes in which a lithium ion dissociable salt such as Li (CF ₃ SO ₂ ) ₂ N is dissolved, polyethers, polyesters, polyimines represented by polyethylene oxide and polyphosphazene crosslinked products, A lithium ion conductive non-aqueous electrolyte such as a polymer solid electrolyte in which the lithium salt is solid-solved in a polymer such as a polyether derivative or an inorganic solid electrolyte such as Li ₃ N or LiI may be used. Here, the heterocyclic compounds are tetrahydrofuran, 2-methylhydrofuran, 1,3 dioxolane, γ
-Butyrolactone, ethylene carbonate, propylene carbonate, butylene carbonate, sulfolane, 3
-Methylsulfolane, N-methylpyrrolidone, thiophene and the like are mentioned. Chain ethers are 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, 1,
2-diethoxyethane, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme and the like can be mentioned. Examples of glycol ethers include ethyl cellosolve, ethyl carbitol, butyl cellosolve, and butyl carbitol. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Other organic solvents such as methyl formate, hexamethylphosphoric triamide, acetonitrile, dimethylformamide, nitromethane, benzene, toluene and hexane can be used as the solvent regardless of the presence or absence of polarity and strength.

The supporting salt concentration in the non-aqueous electrolyte is not particularly limited, but it is preferable to use it so that the supporting salt concentration in the battery is between 0.5 mol / liter and 1.5 mol / liter. In particular, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and dimethyl carbonate, diethyl carbonate,
LiClO ₄ , LiPF ₆ , L in a mixed solvent mainly containing chain alkyl carbonate such as ethyl methyl carbonate
It is more preferable to use an organic electrolytic solution in which a salt such as iBF ₄ or LiCF ₃ SO ₃ is dissolved, because a charge / discharge characteristic is excellent even at a low temperature, a battery having a long cycle life and a large current can be taken out easily. .

The injection of the electrolytic solution may be carried out all at once, but it is preferable to carry out the injection in two or more times. When the electrolytic solution is injected twice or more times, the composition of each electrolytic solution may be changed, but it is preferable to use the same electrolytic solution. As a welding method for the outer case, the battery lid, the electrodes, the leads, and the electrode terminals, electric resistance welding using direct current or alternating current, laser welding, ultrasonic welding, or the like can be used. Further, it is possible to seal the outer case and the battery sealing lid with packing by mechanical caulking or screwing, or sealing using a resin sealing material. In particular, it is preferable to use a two-kind three-layer laminate film of maleic acid-modified polyethylene resin / high-density polyethylene resin / maleic acid-modified polyethylene resin as the resin sealing material. It is also possible to provide a flange or the like on the outer case and / or the battery sealing lid for sealing.

The atmosphere for producing the battery using the spirally wound electrode group is preferably argon gas or carbon dioxide gas which is inactive to metallic lithium, but it is also possible in sufficiently dry air. The degree of drying of the atmosphere is preferably −20 ° C. or lower in terms of dew point, but it is more preferable to carry out the drying at a low humidity of −40 ° C. or lower since it is effective in improving the reliability of the battery. Further, all the manufacturing steps do not have to be in the same atmosphere, and a preferable atmosphere may be created only in a specific step such as electrolyte injection.

[0054]

【Example】

[Example 1] An example will be described with reference to the drawings. Fig. 1 shows a cross-sectional view of a core of a wound electrode group in which a battery is wound in a spiral shape.

In the figure, reference numeral 1 is a polyethylene porous separator. The width of the separator is 45m
m, the length is 1080 mm, and the thickness is 25 μm. 2 is a positive electrode. The material of the current collector of the positive electrode is aluminum and is a thin flat plate having a smooth surface. Positive electrode current collector length 4
The width is 25 mm, the width is 39 mm, and the thickness is 10 μm. A layer of conductive paste is provided on the current collector of the positive electrode. The conductive paste layer is prepared by previously applying a paste in which fine-grained graphite is dispersed with a water-soluble binder, and heating and drying with warm air.
It has been rolled and crimped. The surface coated with the conductive paste has a length of 412 mm, a width of 39 mm, and a thickness of 5 μm. There is a positive electrode mixture application surface on the conductive paste layer. The positive electrode mixture is a mixture of LiCoO ₂ and a binder made of PVdF polymer, and graphite as a conduction aid. The mixing weight ratio is 85: 10: 5 wt% respectively. As the positive electrode mixture, a paste using n-methyl-2-pyrrolidone as a dispersion medium is applied on a conductive paste, dried, and rolled to be used. The positive electrode after molding has a length of 425 mm, a width of 39 mm, and a thickness of 130 μm. 3 is a negative electrode. The material of the current collector of the negative electrode is copper, which is a thin flat plate having a smooth surface. The negative electrode current collector has a length of 492 mm, a width of 41 mm, and a thickness of 20 μm.
Is. A layer of conductive paste is provided on the negative electrode current collector.
The conductive paste layer is formed by previously applying a paste in which graphite having a fine particle diameter is dispersed with an epoxy-based binder, and heating and drying with warm air. The surface coated with the conductive paste has a length of 487 mm, a width of 41 mm, and a thickness of 5 μm. There is a negative electrode mixture application surface on the conductive paste layer. The negative electrode mixture is a mixture of silicon oxide, graphite, and a binder made of polyacrylic acid polymer. The mixing weight ratio is 45:40:15 wt% respectively. As the negative electrode mixture, a paste using pure water as a dispersion medium is applied on a conductive paste, dried, and rolled to be used. Negative length after molding is 4
The size is 92 mm, the width is 41 mm, and the thickness is 70 μm.

4 was metallic lithium, which was supplied together with the negative electrode during winding. A total of 2 lithium was used so that it was placed on both sides of the negative electrode.
mm, width 16.9 mm, and thickness 30 μm. Reference numeral 5 is a negative electrode lead. The negative electrode lead is made of nickel and is 49 m long
m, width 2.5 mm, thickness 0.1 mm. The negative electrode lead was ultrasonically welded directly to the surface of the negative electrode current collector which was not coated with the conductive paste before being used for winding. A tape for reinforcement and insulation was attached so as to cover the ultrasonically welded surface of the lead. The tape is based on polyimide and the adhesive is acrylic. The width of the tape is 6 to 10 mm, the length is 20 to 41 mm, and the total thickness including the adhesive layer is 55 μm. Reference numeral 6 is a positive electrode lead. The positive electrode lead is made of aluminum and has a length of 49 mm, a width of 2.5 mm and a thickness of 0.1 mm. The positive electrode lead was ultrasonically welded directly to the surface of the positive electrode current collector, which was not coated with the conductive paste, before being used for winding. A tape was attached for reinforcement and insulation so as to cover the ultrasonically welded surface of the lead. Also, for insulation,
Using this tape, a tape was attached so as to cover the area other than the welding surface of the negative electrode lead. 7 is a tape for fixing the final part of the wound electrode group. The tape is a polypropylene base material and has a rubber adhesive.

The winding core of the winding has a rectangular cross-section as shown in FIG.
The separator was arranged so as to be located at the center of the winding core, and the positive and negative electrodes were supplied from opposite directions, and were sandwiched and fixed by heating while being heated. The spirally wound electrode group was obtained by rotating the winding core so that the load was continuously applied to the positive and negative electrodes and the separator, respectively.
The final part of the wound electrode group was fixed with tape. The obtained wound electrode group was designated as A, compressed to fit the inner diameter of the battery outer case made of metal, and inserted into a rectangular battery outer case. Weld the positive and negative electrode leads and the electrodes attached to the battery sealing lid, and after laser welding the battery sealing lid, inject the electrolytic solution from the electrolytic solution inlet provided in the battery sealing lid, and Sealed.

The completed battery was left for a certain period of time, and an electrochemical evaluation test was carried out by checking the time when the electrode was impregnated with the electrolytic solution. The test conditions were a current of 400 mA, a constant current with an upper limit voltage of 4.2 V and a constant voltage of 2.5 V. After that, a discharge test at 1C was performed. As a result, 720m
The discharge capacity of Ah was obtained.

[ Comparative Example 1 ] A battery was obtained in the same manner as in Example 1 except that lithium was not used and the same members as in Example 1 were used. The wound electrode group used at this time is designated as B. The completed battery was subjected to the same evaluation test as in Example 1. As a result, 420mA
A discharge capacity of h was obtained. A and B had a large difference in discharge capacity, and the effect of simultaneously entraining lithium during winding was obtained.

[ Comparative Example 2 ] A wound electrode group was obtained in the same manner by using a member having the same structure as in Example 1 except that heating was not performed during winding. This wound electrode group is designated as C. When C was decomposed, peeling of the electrode was noticeable as compared with the case where A was similarly decomposed.
Nothing was seen in the decomposition of A.

[0061]

INDUSTRIAL APPLICABILITY The present invention is a non-aqueous electrolyte secondary battery comprising at least a strip-shaped positive electrode, a strip-shaped negative electrode, and a lithium ion conductive non-aqueous electrolyte as described above, and occludes lithium ions in the negative electrode active material. Using an oxide and / or carbonaceous material of at least one element selected from Group IIIB, Group IVB and transition metals of the periodic table capable of occluding and releasing releasable lithium ions, and winding it in a spiral shape while heating. A secondary battery having a high energy density, a small polarization, and excellent charge / discharge characteristics at a large current can be obtained by previously using a wound wound electrode group, and occluding lithium in the negative electrode in advance. .

Further, as described in detail above, a step of forming a mixture layer capable of occluding and releasing lithium ions on a current collector, a step of cutting into a strip electrode by cutting to a predetermined size, and a step of forming an electrode By carrying out the step of connecting the leads, the step of winding the strip-shaped positive and negative electrodes through the separator if necessary, and the step of fixing the winding terminal end, excellent productivity and improved yield can be achieved. realizable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a wound electrode group in which electrodes are spirally wound.

FIG. 2 is a cross-sectional view of a winding core of a wound electrode group.

[Explanation of symbols]

1 separator 2 positive electrode 3 Negative electrode 4 metallic lithium 5 Negative electrode lead 6 Positive lead 7 fixing tape

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fumiharu Iwasaki 1-8 Nakase, Mihama-ku, Chiba, Chiba Seiko Electronics Co., Ltd. (72) Hideo Sakamoto 1-8, Nakase, Mihama-ku, Chiba Seiko Electronics Co., Ltd. (72) Inventor Shinichi Takasugi 1-8 Nakase, Nakase, Mihama-ku, Chiba, Chiba Seiko Electronics Co., Ltd. (56) Reference JP-A-7-201318 (JP, A) JP-A 7-307150 (JP, A) JP 5-47419 (JP, A) JP 3-190061 (JP, A) JP 57-194464 (JP, A) JP 6-325765 (JP, A) JP-A-7-230800 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 4/02 H01M 6/16 H01M 10 / 00-10 / 34

Claims (3)

(57) [Claims] 1. A wound electrode group comprising at least a band-shaped positive electrode, a band-shaped negative electrode, and a lithium ion conductive non-aqueous electrolyte, and spirally wound with a separator interposed between the positive electrode and the negative electrode. In the non-aqueous electrolyte secondary battery consisting of, the negative electrode active material of the negative electrode is LixMySiOz (0 ≦ x,
0 ≦ y <1, 0 <z ≦ 4, M is one or more elements selected from metallic and non-metallic elements except lithium and silicon)
The separator is polyethylene or polypropylene, and the positive electrode and / or the negative electrode is heated at 40 ° C. to 80 ° C. while having the spirally wound electrode group. Water electrolyte secondary battery. 2. A wound electrode group comprising at least a band-shaped positive electrode, a band-shaped negative electrode, and a lithium ion conductive non-aqueous electrolyte, and spirally wound with a separator between the positive electrode and the negative electrode. In the non-aqueous electrolyte secondary battery consisting of, the negative electrode active material of the negative electrode is LixMySiOz (0 ≦ x,
0 ≦ y <1, 0 <z ≦ 4, M is one or more elements selected from metallic and non-metallic elements except lithium and silicon)
Represented by the composition formula, wherein the separator is polyethylene or polypropylene, and the wound electrode group is heated at 40 ° C. to 80 ° C., and the non-aqueous electrolyte has the wound electrode group wound in a spiral shape. Secondary battery. 3. A step of forming a mixture layer capable of storing and releasing lithium ions on a current collector, and cutting the current collector and the mixture layer into predetermined dimensions, and then LixMy
Forming a strip-shaped negative electrode using SiOz (0 ≦ x, 0 ≦ y <1, 0 <z ≦ 4, M is one or more elements selected from metal and non-metal elements excluding lithium and silicon) as a negative electrode active material. A step of forming a strip-shaped positive electrode, a step of connecting a lead to the strip-shaped negative electrode and the strip-shaped positive electrode, a step of electrochemically doping lithium into the strip-shaped negative electrode, and polyethylene or polypropylene Non-aqueous electrolyte secondary battery comprising a step of winding the strip-shaped positive electrode and the negative electrode while heating at 40 ° C. to 80 ° C. via a separator Manufacturing method.