JP2001202998A - Square shape nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a square shape nonaqueous secondary battery of a large capacity and high safety. SOLUTION: The square shape nonaqueous secondary battery accommodates in a square shape battery can an elliptic or oval electrode of a winding structure having a positive pole, where at least a part of the positive pole collector forms on both sides a film of the coat containing a positive pole active material and a negative pole, where at least a part of the negative pole collector forms on both sides a film of the coat containing a negative pole active material wound through a separator. At least one side of the battery can forms a concave and an electrode opposing to the battery can accommodating the electrode of the winding structure constitutes substantially a single electrode only of a positive pole or a negative pole. A part of the surface of at least the outermost positive pole collector in the electrode of the winding structure is provided with no film of the coat, containing the positive pole active material. This part which forms no film of the coat containing the positive pole active material is to be opposite to a negative pole or the inner surface of the battery can through the separator. In addition, the lead welded to the negative pole collector is not to be opposite directly to the positive pole through the separator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prismatic non-aqueous secondary battery, and more particularly to a prismatic non-aqueous secondary battery having a specific structure in order to secure safety while increasing capacity.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of portable electronic devices that use a secondary battery as a main power source, the chances of using the device portablely have increased, and the electronic device has been used in a wider environment than before. Was. Non-aqueous secondary batteries such as lithium-ion secondary batteries are widely used as the main power source for portable electronic devices because of their large capacity, high voltage, high energy density, and high output. And their usage tends to increase. As such a secondary battery, LiCoO ₂ is currently used as a positive electrode active material.
Lithium ion secondary batteries using (lithium cobalt oxide) and a carbon-based material as the negative electrode active material have been commercialized. However, in order to increase the capacity of this battery and to ensure safety, Unlike a non-aqueous secondary battery using lithium metal as a negative electrode, a paste in which the above active material is dispersed in an organic solvent together with a binder and the like is used, and the paste is used to form a positive electrode current collector and a negative electrode current collector. A coating film containing an active material was formed on each of both surfaces, and used as a positive electrode and a negative electrode, respectively. Then, a cylindrical electrode body produced by spirally winding these band-shaped electrodes via a separator is inserted into a cylindrical battery can to constitute a battery.

However, the demand for high capacity and small size and light weight of batteries used in equipment is increasing year by year. However, the storage efficiency of conventional cylindrical batteries is low, and the storage of batteries in cordless equipment is particularly difficult. Because the volume is reduced,
There has been a problem that the above demand cannot be sufficiently satisfied.

[0004] Therefore, a secondary battery having a rectangular battery can has been proposed for the purpose of reducing the size of the battery and saving space. When this rectangular battery can is used, the electrode body to be inserted therein is different from the cylindrical electrode body produced by winding the above-mentioned band-shaped electrode, and has a large number of rectangular plate-like positive and negative electrode plates. Or a pair of band-shaped positive and negative electrodes wound through a separator as in the case of the cylindrical electrode body described above, and then pressing this from a certain direction. Alternatively, an elliptical or elliptical electrode body produced by using a combination of a long axis and a short axis as a winding core at the time of winding and further pressing as necessary. However, in the former electrode structure having a laminated structure, it is necessary to provide an electrode terminal on each electrode plate, and furthermore, it is necessary to connect the terminals, thereby lowering productivity and lowering the capacitance density. Was. For this reason, for a prismatic battery, an electrode body having a wound structure formed by winding the latter pair of band-shaped electrodes in an elliptical or elliptical shape is often used.

[0005] However, a lithium ion secondary battery in which the above-mentioned wound electrode body is inserted into a battery can uses an active material for doping and undoping lithium ions in a positive electrode and a negative electrode. In addition, the electrode active material-containing coating film repeatedly expands and contracts during charge and discharge. When such expansion occurs, the cylindrical battery can exerts pressure evenly on the entire circumference of the side surface, so that the pressure resistance is excellent, but the rectangular battery can is easily subjected to pressure deformation in a flat surface. Therefore, the side surface of the battery can expands, and deformation such as swelling of the battery is likely to occur. In particular, when the thickness of the battery can is reduced in order to reduce the weight of the battery per capacity, the cylindrical body of the cylindrical battery can has an ideal shape for the pressure resistance. However, in the case of a rectangular battery can, swelling on the side portion where pressure is likely to be applied becomes noticeable, and tensile stress is applied to the weld between the battery can and the sealing plate. And the gap between the positive electrode and the negative electrode in the wound electrode body increases, and the smooth movement of lithium ions to facilitate the charge / discharge reaction occurs. I do. In this case, if the battery can material is iron or stainless steel, it is possible to maintain the shape to some extent by the rigidity of those materials, but to reduce the weight, a battery can made of light metal such as aluminum or magnesium is used. When the battery is used, the rigidity is further insufficient with the same thickness, and the front and rear surfaces of the battery can swell due to the charge / discharge cycle.

In order to solve the above-mentioned problem in the case of using a rectangular battery can, it has been proposed to dispose an element pressing plate between the battery can and the outermost peripheral portion of the electrode body. Have not achieved sufficient results. Therefore, it is proposed to provide a recess in the long side surface of the battery can in order to suppress the expansion of the electrode body by the battery can itself and to absorb the expansion of the battery can once the electrode body expands. (Japanese Patent Application Laid-Open Nos. 62-126566, 5-28973, and 9-1990).
No. 89). By using the battery can having the above structure, even when the electrode body expands due to the charge / discharge reaction, the concave portion presses the electrode body in the inner surface direction, thereby suppressing an increase in the gap between the electrodes and expanding the battery can. Even if it occurs, it can be absorbed by the concave portion of the battery can and can be prevented from expanding beyond the width of the short side portion.

[0007]

However, the rectangular non-aqueous secondary battery as described above also needs to be designed to have a higher capacity in the future or depending on the specifications required by the user.
It has been found that if the structure of the power generating element itself of the battery is not further devised, it may not be possible to sufficiently cope with safety. In other words, it has been found that there is a tendency for safety to be lacking in a safety confirmation test under severe conditions, such as a crush test, on the assumption of abnormal use intentionally.

The above crush test is based on the assumption that the battery is intentionally crushed by some kind of accident. In this crush test, a rectangular non-aqueous secondary battery having a concave portion formed on the side of the battery can is used. When a battery is mounted, the concave portion provided to prevent the battery can from bulging becomes a convex portion on the inner surface side of the battery can and presses the electrode body, so that the inner wall surface of the battery can comes into contact with the electrode body. It has been found that short circuit is easily caused when the lead body welded to the negative electrode current collector faces the positive electrode via the separator. This is considered to be due to the fact that when the battery is crushed, the recess provided in the battery can presses the electrode body on the inner surface side of the battery can and the lead body of the negative electrode breaks through the separator.

In particular, when the concave portion of the battery can is enlarged in order to absorb the expansion of the electrode body during charging and discharging, the area of the long side portion of the rectangular battery can becomes large. Since it is easy to be located at the opposite position and the gap between the inner wall surface of the battery can and the electrode body is narrowed, the pressure applied to the lead body tends to be large. Further, even at the positive electrode portion not facing the lead body, the positive electrode may be torn by the impact of crushing. In addition, since the battery can also serves as the electrode terminal, a short-circuit current will flow if a different electrode comes into contact with the battery can in the crush test. To increase. Furthermore, when the separator surrounding the electrode body is melted by the heat generation, other parts of the electrode (electrode having a different polarity from the battery can) may also come into contact with the battery can and cause a secondary internal short circuit. Furthermore, in a non-aqueous secondary battery using an electrode provided with an active material-containing coating on the current collector, when a foreign object such as a metal piece is mixed in a production process or when a wound electrode body is inserted into a battery can. Often, active material falls off.

In particular, when an elliptical or elliptical electrode body is inserted into the above-described square battery can, the concave portion of the battery can is a convex portion on the inner surface side of the battery can. It was clarified that the active material-containing coating film of the electrode was in contact with the projections and the active material-containing coating film was easily damaged. In addition, when foreign matter is mixed as described above, since the positive electrode and the negative electrode are usually separated by a separator, a short circuit is rarely caused by the foreign matter. When these foreign substances are present in the battery can during the test, a so-called micro short circuit (soft short circuit)
This can trigger an internal short circuit.

[0011] Further, as the environment surrounding the battery, it has recently been necessary to further increase the energy density of the battery in order to achieve a higher capacity. Therefore, the safety confirmation test under the severe conditions as described above is performed. It is necessary to have high safety even in a crush test, and for that purpose, it is necessary to change the internal structure of the battery to a structure that is difficult to ignite.

Under the circumstances described above, the present invention provides sufficient safety even in a crush test, which is a safety confirmation test under severe conditions, in preparation for a future increase in capacity of a prismatic nonaqueous secondary battery. It is an object of the present invention to improve the structure of a battery so that it can be confirmed, and to provide a square non-aqueous secondary battery with high capacity and high safety.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and as a result of intensive studies on the structure of a non-aqueous secondary battery, it has been found that at least a part of a positive electrode current collector is provided. Wound a positive electrode having a positive electrode active material-containing coating film formed on both surfaces thereof, and a negative electrode having at least a portion of the negative electrode current collector having a negative electrode active material-containing coating film formed on both surfaces thereof via a separator. In a prismatic non-aqueous secondary battery containing an elliptical or elliptical wound structure electrode body in a prismatic battery can,
A concave portion is formed on at least one side surface of the battery can, and the electrode of the spirally wound electrode body facing the battery can is substantially composed of only a single electrode of either a positive electrode or a negative electrode. A portion where the positive electrode active material-containing coating is not formed is provided on at least the outermost peripheral portion of the positive electrode current collector at the outermost periphery of the positive electrode in the electrode body having the structure, and the positive electrode active material-containing coating of the positive electrode current collector is formed. Achieved high capacity by making the part that does not face the negative electrode or the inner surface of the battery can through the separator, and the lead body welded to the negative electrode current collector does not directly face the positive electrode through the separator On the other hand, it has been found that a highly safe rectangular non-aqueous secondary battery which can exhibit excellent safety even in a severe safety confirmation test such as a crush test is obtained.

The following describes in detail the process of completing the present invention and the reason why high security can be ensured while achieving high capacity by adopting the above configuration.

The most common type of wound electrode body in a non-aqueous secondary battery such as a lithium ion secondary battery is a positive electrode made of aluminum foil or the like in order to increase the capacity per volume to obtain a high capacity battery. At least a portion of the current collector has a positive electrode active material-containing coating film formed on both surfaces. At least a portion of the negative electrode current collector formed of a strip-shaped positive electrode and a copper foil has a negative electrode active material-containing coating film formed on both surfaces. Is formed by stacking one strip-shaped negative electrode and two separators in the order of a separator, a negative electrode, a separator, and a positive electrode, and spirally winding the negative electrode on the outer peripheral side of the positive electrode, In order to insert the above-mentioned electrode body into the battery can, the electrode body is formed into a cylindrical wound structure and then pressed from a certain direction, or a combination of a long axis and a short axis as a winding core during winding. Use, and if necessary Pressing to have an elliptical shape or an oval shape was an electrode assembly.

Therefore, the present inventors have proposed a rectangular non-aqueous secondary battery in which a wound electrode structure having the above-mentioned shape is inserted into a rectangular battery can having a concave portion on a side surface and assembled.
A crush test showed that increasing the energy density increased the risk of a short circuit.
In other words, compounds such as carbon materials that can insert and remove lithium are usually used for the negative electrodes of these batteries. However, when the negative electrode is overcharged and lithium is electrodeposited to some extent, the electrolyte is mixed with the electrolyte from about 100 ° C. It has been found that an exothermic reaction occurs between electrodeposited lithium and a carbon material into which lithium has been inserted. Further, even when lithium is desorbed from the positive electrode, the reaction start temperature with the electrolytic solution is lowered, and heat may be generated at around 100 ° C.

In other words, the greater the dischargeable capacity per unit volume of the wound electrode body, the greater the amount of heat generated per unit volume when heat is generated during overcharge, and the battery temperature reaches the thermal runaway temperature of the positive electrode. It is more likely to rise. For this reason, it is necessary to control the heat generation better for a battery having a larger discharge capacity per unit volume so that the battery temperature does not rise to the thermal runaway temperature of the positive electrode. Also, when the volume of the wound electrode body is large, heat is hardly dissipated.

Further, as described above, by using a compound capable of deintercalating lithium, such as a carbon material, in the negative electrode, the reactivity between the electrolytic solution and the negative electrode at a high temperature is higher than when metallic lithium is used for the negative electrode. However, since the lead body provided on the electrode becomes a convex part on the electrode, the battery can provided with the concave part has a battery can based on the concave part due to the expansion of the electrode body at the time of charge / discharge reaction. Since the protrusion on the inner surface side presses the electrode body in the inner surface direction, a large concentrated stress on the protrusion by the lead body and a torsion stress on the electrode body are likely to occur. Then, when the electrolyte is injected, sealed, and the battery is assembled and charged, the electrode body swells due to swelling of the active material, particularly the swelling of the negative electrode active material, and thus has an elliptical or elliptical winding structure. In the electrode body, the above-mentioned concentrated stress and torsional stress further increase, and the electrode body becomes distorted. In such a case, in the battery can provided with the concave portion, the lead body welded to the negative electrode current collector is strongly pressed against the separator, and the lead body is made of a metal material harder than the negative electrode active material-containing coating film. Therefore, at the time of crushing, when the electrode body having the wound structure is crushed, it easily breaks through the separator, thereby easily causing an internal short circuit.

Further, when a concave portion is provided in the battery can, since the concave portion is a convex portion on the inner surface side of the battery can, both the positive electrode and the negative electrode are provided on the outermost peripheral portion of the wound electrode body. In such a structure, the gap between the outermost peripheral portion of the electrode body and the inner wall surface of the battery can is small, and the battery can facing this wound structure on the outer peripheral side is different from one electrode. Since it acts as a pole, if the separator between the electrode body and the inner wall of the battery can melts, contact between the battery can and the electrode of the opposite polarity becomes easy, and a short circuit occurs, and the heat generated by the short circuit generates the electrode body. If the wrapping separator melts,
Since other portions of the above-mentioned electrode (electrode having a different polarity from the battery can) also come into contact with the battery can, a secondary internal short circuit may occur.

Further, when the electrode assembly is inserted into the battery can, the active material-containing coating film provided on the outermost periphery is likely to fall off by coming into contact with the convex portion on the inner side of the battery can. Further, when foreign matter enters between the wound electrode body and the battery can, the electrode is brought into a conductive state, and a minute short circuit is likely to occur, which is likely to cause this minute short circuit in a crush test.

In general, since the lead of the negative electrode and the coating film containing the negative electrode active material have high resistance, when the lead breaks through the separator in the crush test and a large current flows due to an internal short circuit, the lead faces the negative electrode. The positive electrode active material-containing coating promotes heat generation inside the battery due to Joule heat and hinders heat radiation, so that the positive electrode easily reaches a thermal runaway temperature at a relatively early stage. Further, even in a portion where the crushed surface does not face the lead body, the electrode is torn by the impact of the crushing, and a secondary internal short circuit is likely to occur.

The present invention takes the above circumstances into consideration,
The electrode facing the battery can of the wound electrode body is substantially composed of only a single electrode of the positive electrode or the negative electrode, and the lead body of the negative electrode is not directly opposed to the positive electrode via the separator. As a result, as will be described in detail with reference to the drawings in the following embodiments of the present invention, the probability of occurrence of a short circuit is reduced even at the outermost peripheral portion where an internal short circuit is likely to occur, and the active material is mixed due to falling off. Even if the battery of the present invention is prevented from being locally heated by the foreign matter, and even if the battery of the present invention is forcibly crushed in a crush test, an internal short circuit due to the lead body hardly occurs, and a highly safe battery can be obtained. In addition, a portion of the positive electrode current collector alone is provided without forming a positive electrode active material-containing coating film on the outer peripheral surface side of at least the outermost peripheral portion of the positive electrode current collector in the wound electrode body. By making the portion of the body not forming the positive electrode active material-containing coating face the inner surface of the negative electrode or the battery can through the separator, the thermal conductivity to the battery can is increased, and heat is easily radiated, Improves safety.

In the present invention, the electrode facing the battery can of the spirally wound electrode body as described above is substantially composed of only a single electrode of either the positive electrode or the negative electrode. A single electrode includes, of course, the case of a genuine single electrode, but the finished accuracy of the wound electrode body may be slightly shifted due to the accuracy of the winding machine, etc. In some cases, not only one electrode but also the other electrode is partially mixed in the electrode facing the battery can of the wound electrode body, so that the other electrode is partially mixed. Even if it is within a range that does not affect the occurrence of internal short-circuits, it means that it is substantially included in the category of a single electrode. Further, the electrode in the above may be only an electrode current collector on which an active material-containing coating film is not formed.

In the present invention, the elliptical shape or the elliptical shape indicating the shape of the wound electrode body means that the shape is not a perfect circle, and may be any one of an almost elliptical shape and a substantially elliptical shape. For example, it may be flat and partially have a curved surface portion.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically.

According to a specific embodiment of the present invention, as shown in FIG.
a is formed to improve the pressure resistance of the battery can 5 even when the electrode body expands due to charge and discharge, and to absorb the expansion in the concave portion 5a of the electrode body can 5 even when the electrode body expands. The swelling of the battery can 5 can be prevented from expanding beyond the width of the short side surface portion. As the electrode body to be inserted into the battery can, an electrode body having an elliptical or elliptical winding structure according to the shape of the battery can is used, and the outermost peripheral portion is constituted by a positive electrode. As shown in FIG. 3, the positive electrode at the outer peripheral portion is composed of only the positive electrode current collector 1a, and no positive electrode active material-containing coating film is formed on any surface thereof. In the outermost peripheral portion of the negative electrode 2, the negative electrode current collector 2
The negative electrode active material-containing coating film 2b was formed only on the inner peripheral surface side without forming the negative electrode active material-containing coating film on the outer peripheral surface side of a (not shown in FIG. Negative electrode active material-containing coating films are formed on both surfaces of the negative electrode current collector on the negative electrode in the second and subsequent rounds on the inner circumferential side as viewed from the outermost peripheral portion). The electrode facing the battery can at the outermost periphery of the wound electrode body is substantially composed of only the positive electrode, and the positive electrode 1 is shown at the outermost periphery and the second circumference from the outermost periphery. As described above, the outermost peripheral portion of the positive electrode 1 is only the positive electrode current collector 1a, and the positive electrode active material-containing coating film is not formed on any surface thereof. A positive electrode active material-containing coating film 1b is formed on both surfaces of the current collector 1a. And the separator 3 is the positive electrode 1
The positive electrode current collector 1a and the battery can 5 located at the outermost periphery of the wound electrode body as well as between the negative electrode 2 and the negative electrode 2 (in this specific embodiment, the battery can 5 is a positive electrode can). Also interposed between the inner surfaces of the two.

In addition, FIG. 3 and other figures showing the wound electrode body schematically show the wound electrode body, and the dimensional ratio of each member is not always accurate. . This is because a thin member is actually shown with a certain thickness. In addition, there is such a relationship, and a place where there is actually no gap is illustrated as if there is a gap, or vice versa, and a place where there is only a small gap is actually a large gap. Some parts are illustrated as if they were open.

In this specific embodiment of the wound electrode body,
As shown in FIG. 3, the electrode facing the battery can 5 of the wound electrode body is substantially composed of only the positive electrode.
No positive electrode active material-containing coating film is formed on the outer peripheral surface of the outermost peripheral portion of the positive electrode current collector 1a, and the uncoated portion, that is, the exposed portion of the positive electrode current collector 1a, Is exposed to the inner surface of the battery can 5 via the separator 3. The negative electrode active material-containing coating film is not formed on the outer peripheral surface side of the negative electrode current collector 2a at the outermost peripheral portion of the negative electrode 2, and the exposed portion of the negative electrode current collector 2a (that is, the negative electrode current collector 2a Of the positive electrode current collector 1a of the positive electrode 1 via the separator 3 (that is, the portion where the negative electrode active material-containing coating film is not formed) (that is, the positive electrode active material-containing coating film of the positive electrode current collector 1a is formed). A lead body 8 is welded to the outer peripheral surface side of the negative electrode current collector 2a at the outermost periphery of the negative electrode 2, and faces the lead body 8 welded to the exposed part of the negative electrode current collector 1a. An insulating tape 9 is adhered to the inner peripheral surface side of the positive electrode current collector 1a, and the above-mentioned lead body 8 faces the insulating tape 9 with the separator 3 interposed therebetween.

Therefore, in the battery having the wound electrode body, even if the elliptical or elliptical electrode body is inserted into the battery can 5 having the concave portion on the side surface, the battery is not crushed in the crush test. Even when the can 5 presses the electrode body, since the electrode of the electrode body facing the battery can 5 is constituted only by the positive electrode 1, no internal short circuit occurs due to the contact between the battery can 5 and the negative electrode 2, and The negative electrode 2 and the convex portion protruding on the inner surface side of the battery can 5 also serving as a positive electrode terminal face each other via the positive electrode 1, and are interposed between the wound electrode body and the battery can 5 by a crush test. Even when the separator 3 melts and breaks, no internal short circuit occurs due to the contact between the negative electrode 2 and the battery can 5.

Further, a lead body 8 is welded to the outer peripheral surface side of the outermost peripheral portion of the negative electrode current collector 2a, and this lead body 8 faces the insulating tape 9 with the separator 3 interposed therebetween. Therefore, even if the electrode body is pressed by the protrusion on the inner surface side of the battery can at the time of expansion of the electrode body during charging / discharging, occurrence of an internal short circuit can be prevented. Further, since no active material-containing coating film is formed on the outermost periphery of the wound electrode body, when the above-mentioned elliptical or elliptical wound electrode body is inserted into the rectangular battery can 5, The active material-containing coating film of the outermost electrode does not come into contact with the convex portion inside the battery can, so that the active material-containing coating film does not collapse. Therefore, a minute short circuit due to foreign matter mixed between the wound electrode body and the battery can 5 is unlikely to occur, and the probability of progressing to an internal short circuit during a crush test can be reduced. further,
A large current flows through the lead body 8 by the crush test, and the lead body 8
Even when the separator 3 melts due to heat generation, since the lead body 8 does not directly face the positive electrode 1, it is possible to prevent an internal short circuit from occurring.

In particular, when the shape of the wound electrode body is elliptical or elliptical, torsion stress or strain stress is likely to be applied by the projections of the lead body 8 during charging and discharging, and thereby the separator contacting the lead body 8 is formed. Since the stress applied to the lead 3 increases, the separator 3 is more easily melted when the lead body 8 generates heat. However, according to the present invention, the safety can be ensured even in such a case, and the effect is remarkable. Can be expressed. It is preferable that the outermost periphery corresponds to one outermost circumference of each electrode. However, the outermost part may be less than one circumference as long as the probability of an internal short circuit occurring by a crush test can be reduced. There may be.

Further, in the above-mentioned specific portable wound electrode structure, the thickness of the positive electrode insulating tape 9 and the thickness of the separator 3 at the portion where the thickness of the lead body 8 welded to the negative electrode current collector 2a is opposite. It is preferable that the thickness is smaller than the total thickness (the thickness of the insulating tape 9 + the thickness of the separator 3).

That is, in the crush test, when the lead body 8 of the negative electrode 2 is pressed inward, the thickness of the lead body 8 of the negative electrode 1 is set to be larger than the total thickness of the positive electrode 1 and the separator 3. By making the thinner, the crushing proceeds and the lead body 8 breaks through the separator 3 on the outer peripheral surface, further breaks through the insulating tape 9 on the outer peripheral surface, and further prevents an internal short circuit that contacts the positive electrode 1 on the outer peripheral side.

As is clear from the above description, the thickness of the negative electrode 2 as used herein refers to the thickness of the negative electrode 2 from the viewpoint of preventing an internal short circuit caused by the lead body 8 of the negative electrode 2 breaking through the positive electrode 1 facing the negative electrode 2. 2 means the thickness of the positive electrode 1 facing the lead 8.

Further, in the present invention, when the electrode body having the wound structure is used, as shown in FIG.
In the outermost peripheral portion of the negative electrode current collector 1a, the negative electrode active material-containing coating film is not formed on both surfaces of the negative electrode current collector 1a. It is preferable to have a structure in which no film is formed. In other words, even if the outermost peripheral positive electrode is broken by the impact during the crush test, the outermost peripheral positive electrode current collector and the outermost peripheral negative electrode current collector near the outermost peripheral part of the negative electrode current collector first contact each other. Although a large current flows due to a short circuit between current collectors having small resistances, heat dissipation is performed quickly due to the high thermal conductivity, so that the firing probability of the battery can be reduced.

As shown in FIG. 3, at the outermost peripheral portion of the negative electrode 2, no negative electrode active material-containing coating film is formed on the outer peripheral surface side of the negative electrode current collector 2a. By forming the negative electrode active material-containing coating film 2b only on the peripheral surface side, the thickness of the negative electrode active material-containing coating film and the positive electrode active material-containing coating film that are not charged and discharged is reduced, and the space in the battery can is efficiently used. And the capacity can be further increased.
By applying the present invention to such a high-capacity battery, the safety can be greatly improved.

Next, the battery configuration of the present invention will be described.

In the non-aqueous secondary battery of the present invention, the electrolyte may be any of an organic solvent-based liquid electrolyte, a gel electrolyte, and a solid electrolyte, but the present invention provides a liquid electrolyte (hereinafter referred to as an “electrolyte”). This is particularly effective for the case of using. As a solvent for the electrolytic solution, a chain ester having a chain COO-bond such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propionate; propylene carbonate, ethylene carbonate, butylene carbonate, gamma-butyrolactone, ethylene glycol sal Cyclic esters such as phyto, and 1,2-dimethoxyethane, 1,3
-In addition to ethers such as dioxolane, tetrahydrofuran, 2-methyl-tetrahydrofuran and diethyl ether, amine-based or imide-based organic solvents, sulfur-containing or fluorine-containing or phosphoric-containing or silicon-containing organic solvents, and the like are also used. Can be.

In the present invention, it is preferable to use a chain ester as the main solvent of the solvent in the electrolytic solution, since the viscosity of the electrolytic solution is reduced and the ionic conductivity is increased. The main solvent means that the chain ester exceeds 50% by volume in the total electrolyte solvent containing these chain esters. If the chain ester exceeds 65% by volume, the safety of the battery in the crush test after 4.4 V charging tends to decrease in the prior art. However, according to the present invention, the chain ester has such a 65% by volume. Even in the case where the content exceeds% by volume, safety can be ensured, and the effects of the present invention are remarkably exhibited.

When the amount of the chain ester exceeds 70% by volume, the safety of the battery is more likely to be reduced in the prior art, so that the effect of the present invention is more remarkably exhibited. If the content exceeds 75% by volume, the safety of the battery is more likely to be reduced in the conventional technique, so that the effects of the present invention are more remarkably exhibited. Also, in the case where the chain ester has a methyl group, the safety of the battery is liable to be reduced in the conventional technique. Thus, the effects of the present invention are more remarkably exhibited.

When the following ester having a high dielectric constant (dielectric constant of 30 or more) is mixed with the above-mentioned chain ester and used,
Since the cycle characteristics and the load characteristics of the battery are improved as compared with the case where only the chain ester is used, the battery is more preferable. Examples of such an ester having a high dielectric constant include propylene carbonate, ethylene carbonate, butylene carbonate, gamma-butyrolactone, and ethylene glycol sulfite. In particular, those having a cyclic structure are preferred, cyclic carbonates are particularly preferred, and ethylene carbonate is most preferred.

The high dielectric constant ester is preferably less than 40% by volume, more preferably 30% by volume or less, further preferably 25% by volume or less of the total solvent of the electrolytic solution. The improvement of the safety by these esters having a high dielectric constant is easily achieved when the amount of the ester is 10% by volume or more in the total solvent of the electrolytic solution, and the safety is further improved when the amount of the ester reaches 20% by volume. become.

As a solute of the electrolytic solution, for example, LiCl
O_Four, LiPF₆, LiBF_Four, LiAsF₆, LiS
bF₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, Li
CF _ThreeCO_Two, Li_TwoC_TwoF_Four(SO_Three)_Two, LiN
(CF_ThreeSO_Two)_Two, LiC (CF_ThreeSO_Two)_Three, Li
C_nF_{2n + 1}SO_Three(N ≧ 2), LiN (RfOSO_Two)
_Two[Where Rf is a fluoroalkyl group]
Or a mixture of two or more kinds.₆And
LiC_FourF₉SO_ThreeEtc. have good charge / discharge characteristics
preferable. The concentration of solutes in the electrolyte is particularly limited
Although it is not a thing, 0.3 to 1.7 mol / l, especially
About 0.4 to 1.5 mol / l is preferable.

In the present invention, as the positive electrode active material,
Although not limited to, for example, LiCoO_TwoSuch
Lithium cobalt oxide, LiMn_TwoO_FourSuch as Richi
Manganese oxide, LiNiO_TwoLithium ni
Lithium composite oxides such as Kel oxide, manganese dioxide
Oxides such as vanadium pentoxide and chromium oxide
Or a composite oxide having these as a basic structure (for example,
Seed metal additive), or titanium disulfide, molybdenum disulfide
Metal sulfides such as den are used. Especially LiNi
O_Two, LiCoO_Two, LiMn_TwoO_FourOpen when charging
Lithium composite oxide with a circuit voltage of 4 V or more based on Li
When using as a positive electrode active material, high energy density
Is preferred. Especially charged LiCoO_TwoAnd
LiNiO _TwoMeans that the reaction initiation temperature with the electrolyte is LiMn_TwoO
_FourLower than the temperature of the negative electrode
However, according to the present invention, as the positive electrode active material, L
iCoO_TwoAnd LiNiO_TwoSafety when using
Therefore, the present invention can be used as a positive electrode active material.
LiCoO_TwoAnd LiNiO_TwoWhen using, the effect
Is remarkably expressed.

For the positive electrode, for example, a conductive additive such as flake graphite or carbon black, or a binder such as polyvinylidene fluoride or polytetrafluoroethylene is appropriately added to the positive electrode active material described above, for example. A paste is formed with a solvent (the binder may be dissolved in the solvent in advance and then mixed with the positive electrode active material, etc.), and the positive electrode active material-containing paste is made of a metal foil such as an aluminum foil. And dried to form a positive electrode active material-containing coating film. In the present invention, however, the positive electrode active material-containing coating film is not formed on at least the outermost peripheral portion of the positive electrode current collector at the outermost periphery of the positive electrode in the wound electrode body as described above. Leave only the electrical parts.

In the present invention, the thickness of the positive electrode current collector is preferably 5 to 60 μm, particularly preferably 8 to 40 μm.
The thickness of the positive electrode active material-containing coating film is preferably 30 to 300 μm, more preferably 50 to 150 μm per side.

The material used for the negative electrode may be any material capable of doping and undoping lithium ions. In the present invention, such a material capable of doping and undoping lithium ions is referred to as a negative electrode active material. The negative electrode active material is not particularly limited. Examples thereof include graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, and carbon fibers. , Activated carbon and other carbon materials, Si, S
An alloy such as n or In or an oxide such as Si, Sn, or In which can be charged and discharged at a low voltage close to Li can be used.

When a carbon material is used as the negative electrode active material,
The carbon material preferably has the following characteristics.
That is, the inter-plane distance (d ₀₀₂ ) of the (002) plane is preferably 0.35 nm or less, more preferably 0.345 nm or less, and still more preferably 0.34 nm or less. Further, the size (Lc) of the crystallite in the c-axis direction is preferably 3.0 nm or more, more preferably 8.0 nm or more, and further preferably 25.0 nm or more. The average particle size of the carbon material is 8 to 20 μm.
m, particularly preferably 10 to 15 μm, and the purity is preferably 99.9% by weight or more.

For the negative electrode, for example, a binder such as polyvinylidene fluoride or polytetrafluoroethylene is appropriately added to the above-mentioned negative electrode active material, and if necessary, a conductive auxiliary is appropriately added. (The binder may be previously dissolved in a solvent and then mixed with the negative electrode active material, etc.), and the negative electrode active material-containing paste is applied to a negative electrode current collector made of copper foil or the like, dried, and dried. It is produced by forming an active material-containing coating film. However, in the present invention, a negative electrode active material-containing coating film is formed on at least the outermost peripheral portion of the negative electrode current collector at the outermost peripheral portion of the negative electrode in the wound electrode body as shown in Examples described later. Without
It is preferable to leave only the negative electrode current collector.

In the present invention, the thickness of the negative electrode current collector is preferably 5 to 60 μm, particularly preferably 8 to 40 μm.
Further, the thickness of the negative electrode active material-containing coating film is preferably 30 to 300 μm, more preferably 50 to 150 μm per one side.

As the positive electrode current collector and the negative electrode current collector, for example, metal foils such as aluminum, copper, nickel, and stainless steel, expanded metals, and nets are used. A foil is preferred, and a copper foil is particularly preferred as the negative electrode current collector.

In producing the positive electrode and the negative electrode, the application method of applying the positive electrode active material-containing paste and the negative electrode active material-containing paste to a current collector includes, for example, an extrusion coater, a reverse roller, a doctor blade, and the like. In addition, various coating methods can be adopted.

From the viewpoint of increasing the capacity,
Preferably, the chargeable / dischargeable capacity per unit volume of the wound electrode is large, and the chargeable / dischargeable capacity at full charge is 130 mAh / cm ³ per unit volume of the wound electrode.
Or more, preferably 140 mAh / cm ³ or more, and more preferably 150 mAh / cm ³ . Such a high-capacity battery is liable to cause abnormal heat generation, but the present invention can secure safety even for the high-capacity battery as described above. The effect is remarkably exhibited when applied to a battery having a large capacity. Here, the volume of the wound electrode body is a positive electrode,
This is the bulk volume in the battery of the battery in which the negative electrode and the separator are wound, and does not include the volume left after removing the winding shaft used for spirally winding. In short, it is the sum of the bulk volumes occupied by the positive electrode, the negative electrode, and the separator.

In the present invention, the lead of the negative electrode is welded to the negative electrode manufactured as described above on the exposed portion of the negative electrode current collector by resistance welding, ultrasonic welding, or the like. Is 0.1 mm ² in order to reduce resistance and reduce heat generation when a large current flows.
The above is preferably 1.0 mm ² or less, more preferably 0.3 mm ² or more and 0.7 mm ² or less. Nickel is generally used as the material of the negative electrode lead body, but copper, titanium, stainless steel, or the like can also be used.

In the present invention, as the insulating tape to be adhered to the positive electrode current collector, it is preferable to use, for example, an imide-based, polytetrafluoroethylene-based, polyphenylene sulfide-based insulating tape, or the like. The thickness of the positive electrode insulating tape is preferably from 50 μm to 120 μm, and more preferably from 60 μm to 100 μm. The width of the insulating tape depends on the width of the opposing lead body (the negative electrode lead body).
Above is preferably 15 mm or less, 7 mm or more is 12 mm
The following is more preferred.

In the present invention, it is preferable that the separator has sufficient strength and can hold a large amount of electrolyte, and from such a viewpoint, polypropylene having a thickness of 10 to 50 μm and a porosity of 30 to 70% is preferable. , A microporous film or nonwoven fabric made of polyethylene or a copolymer of ethylene and propylene is preferred.

In the non-aqueous secondary battery of the present invention, for example, a positive electrode and a negative electrode produced as described above are overlapped with a separator interposed therebetween, and the resultant is combined into a rectangular shape such as an elliptical shape or an oval shape. An electrode body having a wound structure manufactured by winding the electrode body into a structure insertable into the battery can is inserted into the battery can and sealed. At this time, it is preferable to provide an insulator at the bottom of the electrode body. By disposing an insulator at the bottom of the electrode body, safety against crushing from the bottom of the battery can can be ensured.

The battery can is provided with a concave portion on a side surface in order to prevent the battery from swelling due to the expansion of the electrode body. The material of the battery can is not particularly limited, and various materials can be used. However, it is preferable to reduce the weight of the battery as much as possible by using a material having a low specific gravity, such as aluminum or magnesium, and setting its thickness to a minimum allowable value within the standard. Even with such weight reduction, the present invention provides a concave portion on the side surface of the battery can, so that when the electrode body expands due to a charge / discharge cycle, the expansion of the battery can side is absorbed by the concave portion. This can be prevented. The method of providing the concave portion may be any method. For example, in the case of providing a rectangular concave portion, the metal plate is formed in several steps using a mold comprising at least one set of male and female. In particular, it is possible to adopt a method of forming a concave portion by performing drawing, and further pressing before or after the drawing with another die. When a curved concave portion is provided, a method of forming a concave portion by pressing a press die having a curved press surface on a side surface portion of a drawn battery can can be employed.

Further, the above-mentioned battery usually incorporates an explosion-proof mechanism for discharging gas generated inside the battery to the outside of the battery when the pressure has risen to a certain pressure, thereby preventing the battery from bursting under high pressure. Can be

Further, in the case of a non-aqueous secondary battery, when the charging voltage is charged to 4.25 V or more, particularly to 4.35 V, the risk of abnormal heat generation and the like tends to increase. Even in such a case, safety can be ensured. Therefore, when the present invention is applied to such a case, the effect is remarkably exhibited. The details will be described in Examples.

[0061]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 LiPF ₆ was added to a mixed solvent of methyl ethyl carbonate and ethylene carbonate at a volume ratio of 2: 1.
Dissolve 2 mol / l and make composition 1.2 mol / l Li
An electrolyte represented by PF ₆ / EC: MEC (1: 2 volume ratio) was prepared.

In the above electrolyte, EC is an abbreviation for ethylene carbonate, and MEC is an abbreviation for methyl ethyl carbonate. Therefore, the above-mentioned electrolyte solution of 1.2 mo
1 / l LiPF ₆ / EC: MEC (1: 2 volume ratio)
LiPF ₆ was added to a mixed solvent of methyl ethyl carbonate and ethylene carbonate at a volume ratio of 1: 2 by 1.2 mol / mol.
1 indicates that it was dissolved.

Separately from this, LiC as a positive electrode active material
Scaly graphite is added to oO ₂ as a conductive additive in a weight ratio of 92: 4.
The resulting mixture was mixed with a solution in which polyvinylidene fluoride was previously dissolved in N-methyl-2-pyrrolidone to prepare a paste.
After passing the positive electrode active material-containing paste through a 70-mesh net to remove large pieces, the paste was uniformly applied to both surfaces of a positive electrode current collector made of aluminum foil having a thickness of 15 μm,
It dried and the positive electrode active material containing coating film was formed. However, when the positive electrode made from this is formed into a wound electrode body together with a negative electrode, a separator, etc., the above-mentioned positive electrode active material-containing paste is applied to the outermost peripheral portion of the positive electrode on the outer peripheral surface side of the positive electrode current collector. And the length of the uncoated portion (that is, the exposed portion of the positive electrode current collector on which the positive electrode active material-containing coating film is not formed) is 68
mm (approximately one round), and facing the lead body provided on the negative electrode current collector on the inner peripheral surface side of the outermost peripheral portion,
A polyphenylene sulfide tape having a width of 10 mm and a thickness of 80 μm was adhered as an insulating tape. After drying this band-shaped body, it was pressure-molded to a thickness of 179 μm, cut, and then cut to a width of 3 μm.
One end of an aluminum lead body having a thickness of 100 μm and a thickness of 100 mm was welded to the uncoated portion of the positive electrode current collector (that is, the exposed portion of the positive electrode current collector), and the lead body was attached to produce a belt-shaped positive electrode.

Next, a graphite-based carbon material as the negative electrode active material [provided that the distance between the 002 surfaces (d ₀₀₂ ) = 0.33]
7 nm, crystallite size (Lc) in c-axis direction = 95.0
A carbon material having characteristics of nm, an average particle diameter of 10 μm, and a purity of 99.9% or more] was mixed with a solution in which polyvinylidene fluoride was previously dissolved in N-methyl-2-pyrrolidone to prepare a paste. This negative electrode active material-containing paste was uniformly applied to both surfaces of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 10 μm, and dried to form a negative electrode active material-containing coating film. However, when the negative electrode produced therefrom is formed into a wound electrode body together with the positive electrode and the separator,
The negative electrode active material-containing paste was not applied to the portion of the negative electrode current collector that was the outermost peripheral portion of the negative electrode, and the uncoated portion (that is, the exposed portion of the negative electrode current collector where the negative electrode active material-containing coating film was not formed) was applied. ) Was 65 mm in length. After drying this band-shaped body, it was pressure-molded to a thickness of 142 μm, cut and then
One end of a nickel lead body having a width of 3 mm and a thickness of 0.1 mm (cross-sectional area of 0.3 mm ² ) was welded to a position 8 mm from the leading end of the uncoated portion (that is, the exposed portion of the negative electrode current collector), A strip-shaped negative electrode was produced.

After drying the positive electrode and the negative electrode, the positive electrode is superposed on the negative electrode via a separator made of a microporous polyethylene film having a thickness of 25 μm in a dry atmosphere to form a winding core having a long axis and a short axis. The electrode body was wound and wound to form an elliptical wound structure. Thereafter, a polyimide tape is adhered to the bottom of the electrode body as an insulator, and the wound electrode body is inserted into a battery can having concave portions on both long side surfaces as described later, and the opening is sealed. Thus, a prismatic non-aqueous secondary battery was manufactured. FIG. 1 shows a schematic perspective view of this battery, FIG. 2A shows a plan view thereof, and FIG.
(B) of FIG. FIG. 3 shows the outermost peripheral portion of the wound electrode body and essential parts in the vicinity thereof.

First, the electrode structure having a wound structure will be described first with reference to FIG. 3. In FIG. 3, the positive electrode 1 is shown in the outermost periphery and the second periphery from the outermost periphery. The electrode of the electrode body having the structure facing the battery can 5 is substantially composed of only the positive electrode 1, and the outermost portion has an exposed portion of the positive electrode current collector 1 a, and any surface thereof contains the positive electrode active material. No coating film is formed, and the positive electrode active material-containing coating film 1b is formed on both surfaces of the positive electrode current collector 1a in the second round from the outermost peripheral portion. The outermost peripheral portion of the negative electrode 2 is shown. At the outermost peripheral portion, the negative electrode active material-containing coating film is not formed on the outer peripheral surface side of the negative electrode current collector 2a made of copper foil. The negative electrode active material-containing coating film 2b is formed only on the side. The lead body 8 of the negative electrode 2 is attached to the outer peripheral surface side of the outermost peripheral part of the negative electrode current collector 2a, and the lead body 8 faces the concave portion 5a of the battery can 5 via the separator 3 and the positive electrode 1. ing. The separator 3 is interposed not only between the positive electrode 1 and the negative electrode 2 but also between the positive electrode current collector 1 a located at the outermost periphery of the wound electrode body and the inner surface of the battery can 5. .
FIG. 3 shows an electrode body having a wound structure and essential parts in the vicinity thereof. The battery can 5 is not shown in its entirety but only partially, so the part shown in FIG. Although it is not possible to determine whether or not this is the case, the portion shown in FIG. 3 is the concave portion 5 a of the battery can 5.

In the electrode body of the wound structure of the battery of Example 1, as shown in FIG. 3, a negative electrode active material-containing coating film was formed on the outer peripheral surface side of the negative electrode current collector 2a at the outermost periphery of the negative electrode 1. Not being formed, the negative electrode active material-containing coating film 2b is formed only on the inner peripheral surface side. The exposed portion of the negative electrode current collector 2a faces the exposed portion of the positive electrode current collector 1a of the positive electrode 1 via the separator 3, and the lead member 8 welded to the negative electrode current collector 1a of the negative electrode 1 The insulating tape 9 is opposed to the insulating tape 9 provided on the positive electrode current collector 1 a of the positive electrode 1 at the outermost peripheral portion, and is not directly opposed to the positive electrode 2.

Therefore, when the electrode body having the above structure is applied to a rectangular non-aqueous secondary battery using a rectangular battery can 5 having a concave portion 5a on the side surface, the concave portion 5a is previously formed on the long side surface of the battery can 5. Since it is formed, the expansion of the electrode body at the time of charge and discharge can be suppressed, and once expanded, the deformation due to the expansion of the battery can can be absorbed by the concave portion 5a, and the expansion of the battery can is prevented. Even if the provided recess presses the electrode body in the inner surface direction and the battery can is pressed against the electrode body by the crush test, the outermost positive electrode 1 of the electrode body only comes into contact with the battery can 5 also serving as a positive electrode terminal. Therefore, the internal short circuit does not occur, and the lead body 8 welded to the negative electrode current collector 2a is strongly pressed against the separator 3 and the convex portion of the inner surface of the battery can 5 based on the concave portion 5a due to crushing, or the short circuit occurs. By separator Because but melt, lead body 8 even when the fracture is only in contact with the insulating tape 9, it is possible to prevent the occurrence of internal short circuit. Furthermore, even if the positive electrode 1 is torn at the portion of the positive electrode 1 that is not opposed to the lead body 8 due to the crushing impact and a secondary internal short circuit occurs, the outermost periphery of the positive electrode 1 in the wound electrode body is A portion of only the positive electrode current collector 1a is provided on the peripheral surface without forming the positive electrode active material-containing coating film, and a portion of the positive electrode current collector 1a where the positive electrode active material-containing coating film is not formed is a separator. 3 and a battery can 5 serving as a positive electrode terminal via the separator 3 on the outer peripheral surface of the outermost peripheral portion of the positive electrode 1, and a high-resistance active material. Since it does not face the containing coating film, the thermal conductivity is high, and the heat is quickly released, so that the safety can be further improved. In addition, since the positive electrode at the outermost periphery of the wound electrode body does not form a positive electrode active material-containing coating only with the positive electrode current collector, when the electrode body is inserted, the inside of the battery can 5 is removed. The active material-containing coating film does not fall off due to contact with the projections. In addition, when foreign matter enters between the wound electrode body and the battery can 5, the electrode is energized, thereby easily causing a micro short circuit, which is likely to be a factor inducing this micro short circuit during a crush test. However, also in this case, the wound structure of the electrode body of the present invention can reduce the probability of progressing to an internal short circuit at the time of a crush test due to the above-described structure, and can avoid local heat generation.

Further, the thickness of the lead body 8 of the negative electrode 2 in this wound electrode body is 0.1 mm (100 μm).
Since the thickness of the positive electrode 1 is 179 μm, the thickness of the insulating tape 9 is 80 μm, and the thickness of the separator 3 is 25 μm, the thickness of the lead body 8 is the sum of the thickness of the insulating tape 9 and the thickness of the separator 3. Since it is thinner, even if this battery is forcibly crushed in a crush test, no internal short circuit occurs.

Next, a description will be given of a prismatic non-aqueous secondary battery using the electrode body having the elliptical winding structure. First, an outline of the manufacturing method will be described with reference to FIGS.
The rectangular non-aqueous secondary battery is manufactured as follows. That is, the electrode body having the wound structure is a bottomed square shape having a thickness of 6 mm, a width of 30 mm, and a height of 60 mm and a depth of 0.15 mm.
mm, a width of 10 mm, and a height of 20 mm, into a battery can 5 made of aluminum provided on both sides of a long side face portion,
The free end of the lead member 8 of the negative electrode 2 is welded to the terminal lead plate 14 of the sealing plate 10 of the rectangular battery can 5, and the lead member 7 of the positive electrode 1 is welded.
Is welded to the sealing plate 10. Further, the electrolytic solution was injected into the battery can 5 provided with the concave surface, and after the electrolytic solution sufficiently permeated into the separator 3 and the like, sealing was performed, preliminary charging and aging were performed, and a prismatic non-aqueous secondary battery was manufactured.

FIG. 1 is a schematic perspective view of this prismatic nonaqueous secondary battery.
2A is a plan view, and FIG. 2B is a partial longitudinal cross-sectional view. The positive electrode 1 and the negative electrode 2 are wound into an oval shape with a separator interposed therebetween. As an electrode body 4 having an elliptical wound structure, the battery body 5 is housed in a rectangular battery can 5 together with the electrolytic solution. However, FIG. 2 does not show a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 in order to avoid complication. Also, the outer periphery of the electrode body 4 having an elliptical winding structure is shown by a cross section, but the cross section of the inner periphery is not shown, and the electrolytic solution is not shown.

The battery can 5 is made of an aluminum alloy and serves as an outer case of the battery. The battery can 5 also serves as a positive electrode terminal. Then, from the electrode body 4 having an oval winding structure composed of the positive electrode 1, the negative electrode 2, and the separator 3, a positive electrode lead 7 and a negative electrode lead 8 connected to one ends of the positive electrode 1 and the negative electrode 2, respectively. Have been withdrawn. An aluminum alloy sealing plate 10 for sealing the opening of the battery can 5 has an insulating packing 11 made of polypropylene.
A terminal 12 made of stainless steel is attached to the terminal 12, and a lead plate 14 made of stainless steel is attached to the terminal 12 via an insulator 13.

The sealing plate 10 is inserted into the opening of the battery can 5, and the joint of the two is welded, whereby the opening of the battery can 5 is sealed and the inside of the battery is sealed.

In the battery of the first embodiment, the lead 7 of the positive electrode 1 is directly welded to the sealing plate 10 so that the battery can 5 and the sealing plate 10 function as a positive electrode terminal, and the lead 8 of the negative electrode 2 is The terminal 12 functions as a negative electrode terminal by welding to the lead plate 14 and electrically connecting the lead body 8 of the negative electrode 2 and the terminal 12 through the lead plate 14.

Comparative Example 1 A positive electrode active material-containing coating film was formed on both surfaces of the positive electrode current collector at the outermost periphery of the positive electrode in the wound electrode body of Example 1, and the uncoated portion (that is, the positive electrode active material-containing coating film) was formed. The length of the exposed portion of the positive electrode current collector where the film is not formed is 10 mm, and the positive electrode insulating tape is not attached. On the other hand, the negative electrode side is the outermost portion of the negative electrode in the wound electrode body. The uncoated portion of the negative electrode current collector (that is, the exposed portion of the negative electrode current collector on which the negative electrode active material-containing coating film is not formed) is set to 20 mm, and the width on the outer peripheral surface side of the portion 5 mm away from the negative electrode active material-containing coating film is set. 4m
m, a lead body having a thickness of 0.3 mm (cross-sectional area of 1.2 mm ² ) was welded and attached, except that the positional relationship of the outermost periphery at the time of winding the electrode was schematically shown in FIG. Is
An electrode body having a wound structure was produced in the same manner as in Example 1, and a prismatic nonaqueous secondary battery was produced.

Here, the outermost peripheral portion and its vicinity of the wound electrode structure of the battery of Comparative Example 1 will be described with reference to FIG. The outermost peripheral electrode of the body is the positive electrode 1. The positive electrode 1 has a positive electrode active material-containing coating film 1b formed on both surfaces of a positive electrode current collector 1a, and the uncoated portion thereof (that is, the positive electrode active material-containing coating film). The length of the exposed portion of the positive electrode current collector 1a where no film is formed) is 10 mm, and no insulating tape is attached. on the other hand,
On the negative electrode side, the uncoated portion of the negative electrode current collector 2a at the outermost periphery of the negative electrode 2 in the wound electrode body (that is, the exposed portion of the negative electrode current collector 2a on which the negative electrode active material-containing coating film is not formed) is 20.
mm, and a width of 4 mm and a thickness of 0.3 mm (cross-sectional area 1. mm) on the outer peripheral surface side of a portion 5 mm away from the negative electrode active material-containing coating film 2b.
A lead body 8 of ² mm ² ) is attached by welding.

The batteries of Example 1 and Comparative Example 1 were
After discharging to 2.75 V with a current of 0 mA, 800 mA
After reaching 4.25 V, the battery was charged for 2 hours and 30 minutes under the condition of maintaining a constant voltage of 4.25 V. afterwards,
The battery was subjected to a crush test.

In the crush test, a battery charged to 4.25 V is crushed as it is with a crushing speed of 15 mm / s and a force of 1 ton, and how many of the 20 batteries generate abnormal heat due to an internal short circuit. Was examined. Table 1 shows the results.
In Table 1, the denominator of the numerical value indicating the result is the number of batteries subjected to the test, and the numerator is the number of batteries that generated abnormal heat due to an internal short circuit in the crush test. Note that abnormal heat generation refers to a case where the battery surface temperature becomes 150 ° C. or higher.

[0080]

[Table 1]

As shown in Table 1, the battery of Example 1 generated less abnormal heat due to an internal short circuit in the crush test than the battery of Comparative Example 1. In contrast, the battery of Comparative Example 1 generated a large amount of abnormal heat due to an internal short circuit. In the battery of Comparative Example 1, the coating film 1b containing the positive electrode active material was coated at the outermost periphery of the positive electrode 1 with the coating film containing the negative electrode active material. This is considered to be due to the fact that the lead body 8 of the negative electrode 2 directly faces the positive electrode current collector 1a and the outermost peripheral portion is not a single electrode.

[0082]

As described above, according to the present invention, a square non-aqueous secondary battery having high capacity and high safety can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a prismatic nonaqueous secondary battery according to Embodiment 1 of the present invention.

FIGS. 2A and 2B schematically show the structure of a prismatic nonaqueous secondary battery of Example 1, wherein FIG. 2A is a plan view and FIG. 2B is a partial longitudinal sectional view.

FIG. 3 is an enlarged cross-sectional view showing an outermost peripheral portion of an electrode body having an elliptical wound structure of a rectangular non-aqueous secondary battery and a main part in the vicinity thereof in Example 1.

FIG. 4 is a cross-sectional view showing, on an enlarged scale, an outermost peripheral portion of an electrode body having a wound structure of a prismatic nonaqueous secondary battery of Comparative Example 1 and a main part in the vicinity thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode current collector 1b Coating film containing positive electrode active material 2 Negative electrode 2a Negative current collector 2b Coating film containing negative electrode active material 3 Separator 4 Wound structure electrode body 5 Battery can 5a Concave 6 Insulator 7 Lead on positive electrode side Body 8 Lead body on the negative electrode side 9 Insulating tape 10 Sealing plate 11 Insulating packing 12 Terminal 13 Insulator 14 Lead plate

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Masaji Ishizawa 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell, Ltd. (Reference) 5H011 AA03 AA13 BB03 CC06 5H014 AA04 BB03 CC04 EE05 5H022 AA09 AA18 CC12 CC19 KK03 5H029 AK03 AL02 AL07 AM03 AM07 BJ02 CJ07 DJ05 DJ07

Claims (2)

[Claims] 1. A positive electrode comprising a positive electrode active material-containing coating film formed on both surfaces of at least a part of a positive electrode current collector, and a negative electrode active material-containing coating film on both surfaces of at least a part of a negative electrode current collector. A rectangular non-aqueous secondary battery in which a negative electrode formed and an electrode body having an elliptical or elliptical winding structure wound around a separator are housed in a square battery can. A concave portion is formed on at least one side surface of the can, and the electrode facing the battery can of the electrode structure having the wound structure is substantially composed of only a single electrode of a positive electrode or a negative electrode. At least the outermost surface of the positive electrode current collector at the outermost periphery of the positive electrode in the electrode body having a structure is provided with a portion where the positive electrode active material-containing coating is not formed, and the positive electrode active material-containing coating of the positive electrode current collector is provided. The part that does not form is the inner surface of the negative electrode or battery can through the separator A non-aqueous secondary battery characterized in that a lead body facing the positive electrode and welded to the negative electrode current collector does not directly face the positive electrode via the separator. 2. The rectangular non-aqueous secondary battery according to claim 1, wherein a lead body welded to the negative electrode current collector faces an insulating tape adhered to the positive electrode current collector via a separator.