JP2001189167A - Non-aqueous electrolyte secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary cell that prevents inner short-circuit and has high reliability and safety. SOLUTION: This non-aqueous electrolyte secondary cell includes an electrode body contained within a cell case, and the electrode body is formed by laminating and winding longitudinally band shaped positive and negative electrodes. When the inner diameter of the cell case is A, the maximum outer diameter of the electrode body is B, and the minimum outer diameter of the electrode body is C, a prescribed clearance is formed between the electrode body and the cell case so as to have (B+C)/2A in the range of 0.954 to 0.988 inclusive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0002]

2. Description of the Related Art Nickel cadmium secondary batteries, nickel hydrogen secondary batteries, nickel zinc secondary batteries, lithium ion batteries and the like are known as secondary batteries used as power supplies for portable electronic devices. Above all, for example, a non-aqueous electrolyte secondary battery using a lithium-containing compound as a positive electrode and a lithium-doped / dedopable material for a negative electrode, a so-called lithium-ion battery, has a high energy density and is lightweight, In recent years, backup power supplies for personal computers and mobile phones have become mainstream. Further, such nonaqueous electrolyte secondary batteries are expected to be put to practical use as secondary batteries for high-performance electric vehicles and hybrid vehicles.

[0003] Although this lithium ion battery is provided with a safety valve and a PTC element having a mechanism for interrupting the current in the event of an abnormality, the safety in the event of an abnormality is ensured. Improvement is required.

[0004] A lithium ion battery is used as a secondary battery for an electric vehicle or a hybrid vehicle as an assembled battery formed by connecting a number of unit cells. For this reason, in order to ensure the reliability as a battery pack, it is necessary to ensure higher reliability with a unit cell.

[0005]

However, in the conventional non-aqueous electrolyte secondary battery, the electrode body expands during charging, sometimes leading to an internal short circuit. For example, the initial charging may cause the electrode body to expand and cause an internal short circuit,
There was a problem in the reliability as a battery. In addition, since the electrode body expands due to overcharging, an internal short circuit occurs, and further, heat generated due to the internal short circuit occurs inside the battery,
There was a problem with the safety as a battery.

The present invention has been proposed in view of such conventional circumstances, and has as its object to provide a non-aqueous electrolyte secondary battery having high reliability and excellent safety.

[0007]

In order to achieve the above-mentioned object, a non-aqueous electrolyte secondary battery according to the present invention is obtained by laminating at least a strip-shaped positive electrode and a strip-shaped negative electrode and winding them in the longitudinal direction. In a non-aqueous electrolyte secondary battery in which an electrode body is loaded in a battery case, when the inner diameter of the battery case is A, the maximum outer diameter of the electrode body is B, and the minimum outer diameter of the electrode body is C,
A predetermined clearance is provided between the electrode body and the battery case so that (B + C) / 2A is in the range of 0.954 or more and 0.988 or less.

In the non-aqueous electrolyte secondary battery according to the present invention having the above-described structure, a predetermined clearance is provided between the electrode body and the battery case. Even if expanded, the electrode body does not contact the battery case. Therefore, the non-aqueous electrolyte secondary battery, even if the electrode body expands due to various charges such as initial charge and overcharge,
The occurrence of an internal short circuit is prevented.

In the above non-aqueous electrolyte secondary battery,
The electrode body has a center pin. As a result, the occurrence of minute internal short-circuits due to overcharging is effectively prevented, and the generation of high-temperature heat inside the battery is reliably prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a non-aqueous electrolyte secondary battery according to the present invention will be described in detail with reference to the drawings.

Non-aqueous electrolyte secondary battery 1 to which the present invention is applied
As shown in FIG. 1, a spiral electrode body 2 formed by laminating a strip-shaped positive electrode and a strip-shaped negative electrode via a separator and being wound in a longitudinal direction is loaded in a battery case 3, The liquid is injected into the battery case 3.

Here, when the inside diameter of the battery case 3 is A, the maximum outside diameter of the electrode body 2 is B, and the minimum outside diameter of the electrode body 2 is C, (B + C) / 2A is 0.954 or more; 0.988
A predetermined clearance is provided between the electrode body 2 and the battery case 3 so as to be within the following range, and the electrode body 2 is loaded into the battery case 3.

Preferably, (B + C) / 2A is in the range of 0.955 or more and 0.985 or less. In particular, in the case of a large non-aqueous electrolyte secondary battery used as a power source for electric vehicles and hybrid vehicles, (B +
C) / 2A desirably satisfies this range.

No predetermined clearance is provided between the electrode body 2 and the battery case 3, that is, (B + C) / 2A is 0.9.
If it exceeds 88, when the electrode body 2 expands due to the electrode expansion due to the electrolyte or the negative electrode expansion due to the initial charge, the battery case 3 presses the expanded electrode body 2 and the stress concentrates on the separator. Therefore, an internal short circuit occurs in the non-aqueous electrolyte secondary battery 1.

When the electrode body 2 expands due to overcharging, the battery case 3 presses the expanded electrode body 2.
Twisting of the electrode body 2 occurs, and a slight internal short circuit occurs in the electrode body 2. If overcharging is continued in this state, high-temperature heat is generated inside the battery due to an internal short circuit.

On the other hand, when an excessive clearance is provided between the electrode body 2 and the battery case 3, that is, when (B + C) / 2A is smaller than 0.954, the reaction area of the electrode body 2 becomes small, and a desired battery is obtained. Does not meet capacity.

The positive electrode is obtained by applying a positive electrode mixture containing a positive electrode active material and a binder onto a positive electrode current collector and drying the mixture.

As the positive electrode active material, a lithium-containing compound or the like is used. As the lithium-containing compound, LiM
Lithium transition metal composite oxides represented by O ₂ (where M represents one or more transition metals), and specifically, LiCoO ₂ , LiNiO _2, and LiMn ₂ O ₄ are used. Is preferred. Such a lithium transition metal composite oxide is prepared by using, for example, carbonates, nitrates, oxides and hydroxides of lithium, cobalt, nickel and manganese as starting materials, and mixing them in an amount according to the composition.
It is obtained by firing in a temperature range of 0 ° C to 1000 ° C.

As the positive electrode current collector, a metal foil such as an aluminum foil is used.

As the binder, a known binder usually used for a positive electrode mixture of this type of battery can be used. Further, a known additive such as a conductive agent may be added to the positive electrode mixture as needed.

The negative electrode is obtained by applying a negative electrode mixture containing a negative electrode active material and a binder on a negative electrode current collector and drying the mixture.
As the negative electrode active material, any material capable of doping / dedoping lithium may be used, and for example, a carbon material or the like is used. Examples of the carbon material include a low-crystalline carbon material obtained by firing at a relatively low temperature of 2000 ° C. or lower,
Highly crystalline carbon materials such as artificial graphite and natural graphite that have been treated at a high temperature of about 00 ° C. are used. Specifically, pyrolytic carbons, cokes, graphites, glassy carbons, fired organic polymer compounds (which are obtained by firing and carbonizing a furan resin or the like at an appropriate temperature), carbon fibers, And activated carbon can be used.

As the negative electrode current collector constituting the negative electrode, a metal foil such as a copper foil is used.

As the binder for the negative electrode mixture, there can be used a known binder which is usually used for a negative electrode mixture of this type of battery. Further, a known additive or the like may be added to the negative electrode mixture as needed.

The electrode body 2 is formed by laminating a strip-shaped positive electrode and a strip-shaped negative electrode obtained as described above via a separator made of, for example, a microporous polypropylene film, and being wound many times in the longitudinal direction. It has a spiral structure.

The electrode body 2 preferably has a center pin. The same center pin as that used as the center pin of this type of non-aqueous electrolyte secondary battery can be used.

By inserting the center pin into the hole at the center of the electrode body 2, even if the electrode body 2 expands due to overcharging and comes into contact with the battery case 3, kinking occurs. Since the kinking force is applied, induction of a minute internal short circuit is prevented. Further, by inserting the center pin into the hole at the center of the electrode body 2, it is possible to orient the electrode body 2 so as to expand outward.

Therefore, in the non-aqueous electrolyte secondary battery 1 in which the electrode body 2 having the center pin is loaded, the occurrence of a minute internal short circuit due to overcharging is effectively prevented, and high-temperature heat is generated inside the battery. Is reliably prevented from occurring.

The hardness of the winding of the electrode body 2 is preferably such that the deformation amount is 8% or less. Here, the amount of deformation means that the spiral electrode body 2 is sandwiched between two flat plates, and the electrode body 2
When a load of 1 kg is applied per 1 cm of the positive electrode width in the width direction, the spiral electrode body 2
It indicates how much deformation has occurred.

As a method for preventing an internal short circuit due to the expansion of the electrode, there is a method of manufacturing a spirally wound electrode body 2 by winding a strip-shaped electrode body extremely loosely. That is, in the nonaqueous electrolyte secondary battery 1 in which the electrode body 2 whose deformation amount is larger than 8% is loaded, the cycle characteristics may be poor. Therefore, when the amount of deformation of the electrode body 2 is 8% or less, the nonaqueous electrolyte secondary battery 1 has excellent cycle characteristics and high capacity.

The non-aqueous electrolyte is a solution in which an electrolyte salt is dissolved in an organic solvent.

Examples of the organic solvent include, but are not limited to, cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate and diethyl carbonate, γ-butyrolactone and γ-valerolactone. Examples include cyclic esters, chain esters such as ethyl acetate and methyl propionate, and ethers such as tetrahydrofuran and 1,2-dimethoxyethane. These organic solvents may be used alone or as a mixture of two or more.

The electrolyte salt is not particularly limited as long as it is a lithium salt which dissolves in an organic solvent and exhibits ionic conductivity. For example, LiPF ₆ , LiBF ₄ , LiClO
₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC
(CF ₃ SO ₂ ) _{3 and the} like. One of these electrolytes may be used alone, or two or more of them may be used in combination.

In manufacturing the non-aqueous electrolyte secondary battery 1, first, the strip-shaped positive electrode and the strip-shaped negative electrode obtained as described above are interposed via a separator made of, for example, a microporous polypropylene film. A spiral electrode body 2 that is laminated and wound many times in the longitudinal direction is manufactured, and this electrode body 2 is housed in a battery case 3. Then, a center pin is inserted into the center of the electrode body 2. Note that insulating plates are provided on both upper and lower surfaces of the electrode body 2.

Next, one end of the positive electrode lead is attached to the positive electrode, and the other end is electrically connected to the battery lid in order to collect current from the positive electrode of the spiral electrode body 2. As a result, the battery lid has conductivity with the positive electrode, and serves as an external positive electrode of the nonaqueous electrolyte secondary battery 1. In order to collect current from the negative electrode of the spiral electrode body 2, one end of the negative electrode lead is welded to the negative electrode, and the other end is welded to the battery case 3. As a result, the battery can has conductivity with the negative electrode, and serves as an external negative electrode of the nonaqueous electrolyte secondary battery 1.

Next, a non-aqueous electrolyte is injected into the battery case 3. Then, the battery case 3 is caulked via an insulating sealing gasket coated with asphalt to fix the battery lid, thereby producing the cylindrical nonaqueous electrolyte secondary battery 1.

The non-aqueous electrolyte secondary battery 1 is provided with a safety valve 4 for releasing the gas inside the battery when the pressure inside the battery becomes higher than a predetermined value.

In the non-aqueous electrolyte secondary battery 1 configured as described above, the inner diameter of the battery case 3 is A, the maximum outer diameter of the electrode body 2 is B, and the minimum outer diameter of the electrode body 2 is C. (B +
C) Since a predetermined clearance is provided between the electrode body 2 and the battery case 3 so that / 2A is in the range of 0.954 or more and 0.988 or less, the electrode body 2 is charged.
The electrode body 2 does not come into contact with the battery case 3 even if the battery expands.
Therefore, the non-aqueous electrolyte secondary battery 1 is prevented from generating an internal short circuit even in initial charging and overcharging, and has high reliability and excellent safety.

In particular, since the electrode body 2 has the center pin, the non-aqueous electrolyte secondary battery 1 is effectively prevented from generating a minute internal short circuit due to overcharging, and generating high-temperature heat inside the battery. Is reliably prevented, which is very excellent in safety.

In the non-aqueous electrolyte secondary battery 1, a predetermined clearance is provided between the electrode body 2 and the battery case 3, so that the space inside the battery increases. This facilitates the injection of the electrolytic solution, resulting in excellent productivity. In particular,
When the non-aqueous electrolyte secondary battery 1 is small, it is difficult for the shut-off valve to be shut off during high-temperature storage.

Further, since there is a predetermined clearance between the electrode body 2 and the battery case 3, gas escape is improved in an ultimate safety test such as gas injection. As the battery 1, safety is improved,
It will be highly reliable.

The shape of the nonaqueous electrolyte secondary battery 1 may be not only small but also large. For example, a large non-aqueous electrolyte secondary battery 5 is provided with a plurality of safety valves 6 as shown in FIG. Also, as the electrolyte,
It is not limited to a so-called non-aqueous electrolyte which is a liquid electrolyte,
It may be a gel electrolyte, a solid electrolyte, or another non-aqueous electrolyte.

[0042]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results.

<Experiment 1> First, a large, cylindrical non-aqueous electrolyte secondary battery was fabricated, and the relationship between the occurrence of an internal short circuit due to initial charging and the clearance was examined.

Sample 1 The method for producing the positive electrode is as follows. First, a positive electrode mixture was prepared by mixing 91 parts by weight of LiCoO ₂ as a positive electrode active material, 6 parts by weight of a graphite powder as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder. next,
This positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Then, this positive electrode mixture slurry was uniformly applied to a belt-like aluminum foil serving as a positive electrode current collector, and dried. In addition, the thickness of the aluminum foil was 20 μm. Next, after compression molding with a roll press machine, it was cut into a width of 342 mm and a length of 5400 mm to obtain a belt-shaped positive electrode.

The method for producing the negative electrode is as follows. First, 90 parts by weight of a negative electrode active material and 10 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. Note that, as the negative electrode active material, a carbon material which was fired in an inert gas atmosphere and then pulverized to an average particle diameter of 20 μm was used. Next, this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry. And
This negative electrode mixture slurry was uniformly applied to a strip-shaped copper foil serving as a negative electrode current collector, and dried. The thickness of the copper foil is 1
The thickness was 5 μm. Next, after compression molding with a roll press machine, it was cut into a width of 348 mm and a length of 5600 mm to obtain a strip-shaped negative electrode.

The strip-shaped positive electrode and the strip-shaped negative electrode produced as described above are laminated via a microporous polyethylene film having a thickness of 80 μm to be a separator, and wound many times to form a spiral electrode body. Produced. When the spiral electrode body was sandwiched between two flat plates and pressed with 34.2 kg, the amount of deformation of the electrode body was 5%.

Next, the positive and negative electrode current collectors were laser-welded to the current collecting positive and negative electrode leads, respectively. The electrode body was housed in a cylindrical battery case having an inner diameter of 65.9 mm with a predetermined clearance.

The predetermined clearance is defined by (B + C) / 2A, where A is the inner diameter of the battery case, B is the maximum outer diameter of the electrode body, and C is the minimum outer diameter of the electrode body. In the non-aqueous electrolyte secondary battery of Sample 1, (B + C) / 2 is 6
Since 4.9 mm and A were 65.9 mm, (B + C)
/ 2A was 0.985.

Next, a battery cover, a packing and a ceramic butting with a safety valve were previously assembled, and the battery cover and the battery case were laser-welded. Thereafter, an electrolytic solution was injected from a hole for injecting the electrolytic solution, and the resultant was sealed with a bolt, thereby producing a cylindrical non-aqueous electrolyte secondary battery. Here, as an electrolytic solution, LiBF ₄ was added at a concentration of 1 mol / l to a solution obtained by mixing propylene carbonate and dimethyl carbonate at a ratio of 1: 1.
What was melt | dissolved so that it might become was used.

Sample 2 The length of the positive electrode was 5240 mm, and the length of the negative electrode was 5440 mm.
mm, and (B + C) / 2 is 64.0 mm,
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that a spiral electrode body was manufactured so that the deformation amount was 5%.

Sample 3 The length of the positive electrode was set to 5060 mm, and the length of the negative electrode was set to 5260 mm.
mm, and (B + C) / 2 is 63.0 mm,
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that a spiral electrode body was manufactured so that the deformation amount was 5%.

Sample 4 The length of the positive electrode was 5060 mm, and the length of the negative electrode was 5260 mm.
mm, and (B + C) / 2 is 63.0 mm,
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that a spiral electrode body was manufactured so that the deformation amount was 8%.

Sample 5 The length of the positive electrode was 5060 mm, and the length of the negative electrode was 5260 mm.
mm, (B + C) / 2 is 63.1 mm,
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that a spiral electrode body was manufactured so that the deformation amount was 12%.

Sample 6 The length of the positive electrode was 5510 mm, and the length of the negative electrode was 5710 mm.
mm, (B + C) / 2 is 65.5 mm,
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that a spiral electrode body was manufactured so that the deformation amount was 5%.

Sample 7 The length of the positive electrode was 4710 mm, and the length of the negative electrode was 4910 mm.
mm, (B + C) / 2 is 61.0 mm,
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 1, except that a spiral electrode body was manufactured so that the deformation amount was 5%.

Samples 1 to 7 prepared as described above
, The short-circuit occurrence rate and the battery capacity were measured. The evaluation methods are described below.

[Short occurrence rate] First, for each battery,
The first charging was performed with the charging voltage set to an upper limit of 4.2V. Then, it was left at 25 ° C., and the internal short-circuit was determined from the voltage change after being left for three weeks. Note that a battery in which an internal short circuit occurred was determined to be a battery whose voltage drop was 20 mV or more larger than the average voltage drop.

[Battery capacity] After the internal short-circuit judgment, the constant current is set to 90 A, the constant current and constant voltage charging is performed up to the upper limit of 4.15 V, and the constant current discharging of 30 A is performed to the final voltage of 2.50 V. Was measured. Note that the battery capacity was an average of 10 batteries to be measured.

As a result, (B + C) / 2A of each battery and the amount of deformation of the spiral electrode body are shown in Table 1.

[0060]

[Table 1]

As apparent from Table 1, (B + C) / 2
In Samples 1 to 5, in which a predetermined clearance is provided between the electrode body and the battery case so that A is in a range of 0.954 or more and 0.988 or less, occurrence of an internal short circuit is prevented. I understood.

On the other hand, (B + C) / 2A is 0.98
In sample 6 exceeding 8, it was found that the electrode body expanded due to charging and came into contact with the battery case, resulting in an internal short circuit. Sample 7 in which (B + C) / 2A is less than 0.954 has no internal short circuit, but has a very low battery capacity of 80.9 Ah because the reaction area of the electrode body is small. Was.

Thus, (B + C) / 2A is 0.954
As described above, it was found that by setting the range to 0.988 or less, the occurrence of an internal short circuit was prevented, and a nonaqueous electrolyte secondary battery having a desired battery capacity was obtained.

Next, the cycle characteristics of the samples 3, 4 and 5 were evaluated as follows.

[Cycle Characteristics] For Samples 3, 4, and 5, the second and subsequent charges were performed at a constant current of 90 A and the charging voltage was increased to an upper limit of 4.15 V for 3 hours. Next, a constant current discharge of 90 A was performed to a final voltage of 2.50 V. This charge / discharge was repeated, and the discharge capacity at each cycle was measured.
Then, the charge / discharge efficiency (%) when the initial discharge capacity was set to 100 was determined, and this value was evaluated as cycle characteristics.

FIG. 3 shows the results of the above cycle characteristics. As is clear from FIG. 3, Samples 3 and 4 having a deformation amount of 8% or less correspond to Sample 5 having a deformation amount of 12%.
It can be seen that it has better cycle characteristics as compared with. From this, it was found that the amount of deformation of the spiral electrode body was preferably 8% or less.

<Experiment 2> Next, a small and cylindrical non-aqueous electrolyte secondary battery was manufactured, and the relationship between the temperature of heat generated inside the battery due to overcharge and the clearance was examined.

The preparation method of the positive electrode of Sample 8 is as follows. First, 86% by weight of LiCoO ₂ as a positive electrode active material, 6% by weight of graphite as a conductive agent, and 4% by weight of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Next, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode mixture slurry. Then, the slurry of the positive electrode mixture was uniformly applied to a belt-shaped aluminum foil having a thickness of 20 μm as a positive electrode current collector, and dried. Next, after compression molding with a roll press machine, it was cut into a belt-shaped positive electrode.

The method for producing the negative electrode is as follows. First, 90% by weight of graphite powder as a negative electrode active material and 10% by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. Next, this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Then, the negative electrode mixture slurry was uniformly applied to a 10 μm-thick strip-shaped copper foil serving as a negative electrode current collector, and dried. Next, after compression-molding with a roll press machine, it was cut into a strip-shaped negative electrode.

As shown in FIG. 4, the band-shaped positive electrode 11 and the band-shaped negative electrode 1 prepared as described above are used as the electrode bodies included in the small and cylindrical non-aqueous electrolyte secondary battery 10.
2 was laminated via a microporous polyethylene film having a thickness of 25 μm to be a separator 13, and a spiral electrode body was formed by winding a large number of times.

Next, the electrode body was accommodated in a nickel-plated iron battery case 14 having an inner diameter of 17.35 mm with a predetermined clearance, and the center pin 15 was inserted into the center of the electrode body. Note that insulating plates 16 were provided on both upper and lower surfaces of the electrode body. The ratio (B + C) / 2A of the clearance was set to 0.9695.

Then, the positive electrode lead 17 made of aluminum is used.
Was drawn out of the positive electrode current collector 18 and welded to the safety valve device 20 in which electrical conduction with the terminal plate 19 was ensured. Further, a nickel negative electrode lead 21 was led out from the negative electrode current collector 22 and was welded to the battery case 14.

Thereafter, an electrolytic solution was injected into the battery case 14. Here, as the electrolytic solution, a solution obtained by dissolving LiBF ₆ as an electrolyte salt at a concentration of 1 mol / l in a solution in which ethylene carbonate and methyl ethyl carbonate were mixed at a ratio of 1: 1 was used.

Then, a safety valve device 20 having a cleavage valve mechanism for caulking the opening of the battery case 14 and a current cutoff mechanism, a PTC element 24 and a terminal plate 19 are fixed via a sealing gasket 23 coated on the surface with asphalt. Thus, a cylindrical non-aqueous electrolyte secondary battery having a diameter of 18 mm and a height of 65 mm was produced.

A non-aqueous electrolyte secondary battery was prepared in the same manner as in Sample 8, except that Samples 9 to 12 (B + C) / 2A were changed as shown in Table 2 below.

Sample 13 Sample 1 except that the electrode body did not have a center pin.
0, a non-aqueous electrolyte secondary battery was produced.

Samples 8 to 1 prepared as described above
Regarding the battery No. 2, the battery capacity was measured. The samples 8 to 13 prepared as described above were subjected to an overcharge test, and the maximum temperature of heat generated inside the battery was measured. These measurement methods are described below.

[Battery Capacity] The battery was charged at a charging voltage of 4.20 V and a charging current of 1000 mA at a temperature of 23 ° C. for 10 hours. Then, the battery capacity was measured by performing a constant current discharge of 1000 mA up to a final voltage of 2.5 V. The battery capacity was the average value of the test batteries I to V.

[Overcharge Test] After measuring the battery capacity, the charge voltage was set to 20 V, the charge current was set to 1700 mA, and the temperature was set to 45.
An overcharge test was performed on the test batteries I to V at ℃. Then, the maximum temperature of the heat generated inside the battery was measured. The measurement of the exothermic temperature was performed by directly attaching a thermocouple to the surface of the battery can.

Table 2 shows the measurement results of the samples 8 to 13, the presence or absence of the center pin, and (B + C) / 2A of each battery. Note that, as the measurement results of the overcharge test, all the maximum temperatures obtained for the individual test target batteries were described.

[0081]

[Table 2]

As apparent from Table 2, (B + C) / 2
Sample 8 in which a predetermined clearance is provided between the electrode body and the battery case so that A is in the range of 0.954 or more and 0.988 or less, and the electrode body has a center pin
-Sample 10 was found to be prevented from generating heat due to an internal short circuit even when overcharged.

On the other hand, (B + C) / 2A is 0.95
In Sample 11, which is less than 4, heat generation due to an internal short circuit was prevented, but the reaction area of the electrode body was small, so that the battery capacity was low. On the other hand, sample 1 in which (B + C) / 2A exceeds 0.988
In the case of No. 2, it was found that the electrode body expanded due to the overcharging and contacted with the battery case due to the overcharging, and was kinked to cause an internal short-circuit, thereby generating high-temperature heat.

Although (B + C) / 2A is within a predetermined range, the sample 13 in which the electrode body does not have the center pin is used.
It was found that overcharge generated heat inside the battery.

Therefore, (B + C) / 2A is set in the range of 0.954 or more and 0.988 or less, and since the electrode body has the center pin, the occurrence of an internal short circuit even when overcharged is prevented. It was found that a non-aqueous electrolyte secondary battery having a desired battery capacity without generating high-temperature heat inside the battery was obtained.

Sample 14 A non-aqueous electrolyte secondary battery was prepared in the same manner as in Sample 12, except that a cylindrical battery having a diameter of 26 mm, a height of 65 mm, and an inner diameter of a battery case of 25.4 mm was prepared. .

Sample 15 A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Sample 12, except that a cylindrical battery having a diameter of 14 mm, a height of 43 mm, and an inner diameter of a battery case of 13.3 mm was manufactured. .

Sample 16 A non-aqueous electrolyte secondary battery was prepared in the same manner as in Sample 9, except that a cylindrical battery having a diameter of 26 mm, a height of 65 mm, and an inner diameter of a battery case of 25.4 mm was prepared. .

Sample 17 A non-aqueous electrolyte secondary battery was prepared in the same manner as in Sample 9, except that a cylindrical battery having a diameter of 14 mm, a height of 43 mm, and an inner diameter of a battery case of 13.3 mm was prepared. .

Samples 14-
17, the above-described overcharge test was performed in the same manner,
The maximum temperature of the heat generated inside the battery was measured. Table 3 shows the above measurement results and (B + C) / 2A of each battery.
Shown in

[0091]

[Table 3]

Samples 16 and 17 have different battery sizes, but (B + C) / 2A is 0.954 or more,
A predetermined clearance is provided between the electrode body and the battery case so as to be 0.988 or less, and the electrode body has a center pin. Was found to be prevented. From this, it was found that the present invention is applicable to non-aqueous electrolyte batteries of various sizes.

[0093]

The non-aqueous electrolyte secondary battery according to the present invention having the above-described structure has a predetermined clearance between the electrode body and the battery case. Thereby, even if the electrode body expands due to the expansion of the electrode due to the electrolyte solution or the expansion of the negative electrode due to charging, the electrode body does not contact the battery case, and the occurrence of an internal short circuit is reliably prevented. Therefore, the non-aqueous electrolyte secondary battery maintains high capacity, has excellent cycle characteristics, has high reliability, and has excellent safety.

In particular, the non-aqueous electrolyte secondary battery has a very excellent safety because the electrode body has a center pin, thereby reliably preventing high-temperature heat generation inside the battery due to overcharging. Becomes

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a non-aqueous electrolyte secondary battery to which the present invention is applied.

FIG. 2 is a schematic diagram of a large non-aqueous electrolyte secondary battery to which the present invention is applied.

FIG. 3 is a characteristic diagram showing cycle characteristics of the batteries manufactured in Samples 3, 4 and 5.

FIG. 4 is a sectional view of a small and cylindrical non-aqueous electrolyte secondary battery to which the present invention is applied.

[Explanation of symbols]

1 Non-aqueous electrolyte secondary battery, 2 electrodes, 3 battery case, 4 safety valve

Continued on the front page F term (reference) 5H029 AJ04 AJ05 AJ12 AK03 AL06 AL07 AM03 AM04 AM05 AM07 BJ02 BJ14 BJ27 CJ07 HJ00 HJ04 HJ12

Claims (4)

[Claims] 1. A non-aqueous electrolyte secondary battery in which at least a band-shaped positive electrode and a band-shaped negative electrode are stacked and wound in a longitudinal direction and loaded in a battery case, the battery case has an inner diameter of A When the maximum outer diameter of the electrode body is B and the minimum outer diameter of the electrode body is C, (B +
C) A predetermined clearance is provided between the electrode body and the battery case so that / 2A is 0.954 or more and 0.988 or less. battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode body has a center pin. (B + C) / 2A is 0.955 or more,
2. The method according to claim 1, wherein the range is 0.985 or less.
The non-aqueous electrolyte secondary battery according to the above. 4. When the electrode body is sandwiched between two flat plates and a load of 1 kg is applied per 1 cm of the width of the positive electrode in the width direction of the electrode body, the amount of deformation of the electrode body is 8%.
The non-aqueous electrolyte secondary battery according to claim 1, wherein: