JP2008091100A - Square lithium-ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a square lithium ion battery in which on an assumption that undulation or warping are apt to occur in a separator when the separator is manufactured by heat fusion-bonding, even if lamination deviation of a positive electrode and a negative electrode occurs, the lamination deviation can be identified easily, and by this, the lamination deviation can be corrected, and the battery having a superior precision can be manufactured. <P>SOLUTION: In the square lithium ion battery that has the positive electrode 1, the negative electrode 2, and the bag-formed separators 3 equipped with a fused part 4 in which peripheries of two sheets of rectangular separators 3a are mutually fused and the positive electrode 1 is arranged in the inside, and that is equipped with the lamination electrode body 10 in which this bag-formed separator 3 and the negative electrode 2 are alternately arranged, the fused parts 4 are formed on three sides of the bag-formed separators 3, and the ends 4a of the fused parts 4 are extendingly installed toward the outer edges 3b of the bag-formed separators 3, and the outer edge positions of the fused part 4 are arranged at the same position by the respective bag-formed separators 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a prismatic lithium ion battery used for a robot, an electric vehicle, a backup power source and the like.

  In recent years, batteries have been used not only for power sources of mobile information terminals such as mobile phones, notebook personal computers, and PDAs, but also for robots, electric vehicles, backup power sources, etc., and further increase in capacity is required. It has become like this. In response to such demands, lithium ion secondary batteries have high energy density and high capacity, and are therefore widely used as drive power sources as described above.

  As a battery form of such a lithium ion secondary battery, it is roughly divided into a cylindrical type in which a spiral electrode body is enclosed in a bottomed cylindrical exterior body, and a laminated electrode body in which a plurality of rectangular electrodes are laminated. There is a square type encapsulated in an exterior body produced by welding two laminated films.

  Among these lithium ion secondary batteries, the specific structure of the laminated electrode body of the latter battery is that a sheet-like positive electrode having a positive electrode lead and a sheet-like negative electrode having a negative electrode lead are substantially the same shape as the negative electrode. The required number of layers are stacked via a square separator. In this case, the structure is such that the dimensions of the positive electrode are smaller than the dimensions of the negative electrode so that charging and discharging can be performed smoothly.

  However, in the conventional structure, when the positive electrode and the negative electrode are stacked via a separator, stacking deviation is likely to occur. This is because the electrode of the lithium ion battery has a thickness of several tens to several hundreds of μm for both positive and negative electrodes, and the separator is also several tens of μm thick. This is thought to be caused by the occurrence of wrinkles or wrinkles. When the stacking deviation occurs in this way, cycle characteristics deteriorate due to lithium deposition on the electrode end due to repeated charge / discharge, or short circuit in the battery occurs due to contact between the positive electrode and the negative electrode. There was a problem that it was likely to occur.

  Therefore, a proposal to form two adjacent separators in a bag shape by positioning at least one fused portion on each of at least two sides adjacent to each other, and to position the positive electrode in the bag-shaped separator. (See Patent Document 1 below). With such a configuration, since the positive electrode is disposed in the bag-like separator, direct contact between the positive and negative electrodes is suppressed, and the occurrence of a short circuit in the battery can be suppressed to some extent.

However, since the material of the separator is made of polyethylene or polypropylene, when the separator is processed into a bag shape by heat fusion, the separator is likely to be wavy or warped. When the separators are wavy or warped as described above, there is a problem that stacking deviation between the positive electrode and the negative electrode occurs, so that an accurate battery cannot be manufactured and cycle characteristics cannot be improved.
In consideration of this, when the peripheral parts of two separators are fused to form a bag, a proposal is made to perform partial fusion while leaving the non-fused parts around these separators. (See Patent Document 2 below).

Japanese Patent Laid-Open No. 7-302616

JP-A-9-213377

  However, even with the configuration as described above, since there is a step of processing the separator by thermal fusion, it is not possible to completely prevent the separator from being wavy or warped, and a laminating deviation also occurs. In addition, since such a stacking shift is a slight shift (about 1 mm), it is difficult to confirm the stacking shift. As a result, the problem that an accurate battery cannot be produced cannot be solved.

  The present invention has been made in consideration of the above, and is a lamination of a positive electrode and a negative electrode, assuming that the separator is wavy or warped when the separator is processed by heat fusion. A prismatic lithium ion battery capable of easily confirming the stacking deviation even if a shift occurs, thereby correcting the stacking shift, producing an accurate battery, and improving cycle characteristics, etc. The purpose is to provide.

  In order to achieve the above object, the present invention provides a positive electrode having a positive electrode active material layer formed on at least one surface of a positive electrode conductive core made of a rectangular sheet, and one side of the positive electrode conductive core. A negative electrode having a negative electrode active material layer formed on at least one surface of a negative electrode conductive core made of a rectangular sheet and having a larger side dimension than the positive electrode, and the negative electrode conductive material A negative electrode current collecting tab protruding from one side of the core body, and a bag-like separator having a fusion part in which the peripheral parts of two rectangular separators are fused together, and the positive electrode disposed inside In the prismatic lithium ion battery having a structure in which the bag-shaped separator and the negative electrode are alternately arranged to form a laminated electrode body, and the positive electrode current collecting tab and the negative electrode current collecting tab protrude from the laminated electrode body. The fused part is the above Formed on at least two sides of the separator, and a part of the fusion part is extended to the outer edge of the bag separator, and the outer edge of the fusion part is arranged at the same position in each bag separator. It is characterized by being.

  As in the above configuration, if a part of the fusion part extends to the outer edge of the bag-like separator and the outer edge position of the fusion part is arranged at the same position in each bag-like separator, the positive electrode is arranged inside. When a laminated electrode body is produced by alternately arranging the bag-shaped separators and the negative electrodes, when the stacking deviation occurs in the bag-shaped separator, the fusion part existing at the outer edge position is aligned in a straight line when confirmed from the laminating direction. Therefore, the stacking deviation can be easily confirmed. Therefore, since the stacking deviation can be corrected without missing the stacking deviation, an accurate battery can be manufactured. As a result, it is possible to suppress deterioration in cycle characteristics due to lithium deposition on the electrode end due to repeated charge / discharge, or occurrence of short circuit in the battery due to direct contact between the positive and negative electrodes. In addition, since the thickness of the fused part is smaller than other parts, it can be confirmed not only by visual observation but also by a sensor or the like.

  In addition, in order to prevent lithium from precipitating around the negative electrode due to repeated charge and discharge, it is necessary to make the positive electrode dimension smaller than the negative electrode dimension. If it can be easily corrected, the difference between the dimensions of the positive electrode and the negative electrode can be reduced. That is, even if the positive electrode is enlarged, the positive electrode can be prevented from protruding from the negative electrode during lamination. As a result, the capacity of the battery can be increased.

  The reason for forming the fusion part on at least two sides of the bag-like separator is as follows. That is, if the stacking misalignment between the positive electrode and the negative electrode is a shift in a direction parallel to the side where the fused part is formed, the stacking misalignment can be confirmed if the fused part is formed on one side of the bag-shaped separator. If the misalignment between the positive electrode and the negative electrode deviates from each side at an angle (deviation in the rotational direction), the misalignment is confirmed only by forming the fused portion on one side of the bag-shaped separator. There are cases where it is not possible. Therefore, the fusion part is formed on at least two sides of the bag-like separator so that it can be easily corrected even when it is displaced in the rotational direction.

It is desirable that the fused portion is provided on three sides of the bag-shaped separator.
When the welded portion is provided on only two sides of the bag-shaped separator, the positive electrode may move within the bag-shaped separator, and a deviation may occur between the positive electrode and the negative electrode. If the fusion part is provided on the three sides, the movement of the positive electrode in the bag-like separator is further suppressed. Therefore, the occurrence of misalignment between the positive electrode and the negative electrode is further suppressed.

  Further, when the fusion part is provided on two sides of the bag-like separator and the fusion part is provided on two opposite sides, the case is shifted in a direction perpendicular to these sides. In some cases, the misalignment cannot be confirmed. Furthermore, in order to avoid such an inconvenience, it is conceivable to provide a fusion part on two adjacent sides. However, in this case, there arises a new inconvenience that the positive electrode easily protrudes from the bag-shaped separator. Therefore, in order to avoid these inconveniences, it is preferable that fusion portions are provided on the three sides of the bag-shaped separator.

  In addition, although it is good also as a structure which provides the said melt | fusion part in four sides of a bag-shaped separator, since the wave | undulation and curvature of a separator become large in this case, when it laminates | stacks, it will become easy to generate | occur | produce stacking | stacking deviation. Therefore, it is most desirable to provide a fusion part on the three sides of the bag-shaped separator.

It is desirable that the positive electrode current collecting tab and the negative electrode current collecting tab protrude from a side where the fused portion is not provided in the bag-shaped separator.
Such a configuration is desirable because, when a fusion part is provided on the side where both current collecting tabs protrude, stress is applied to both current collecting tabs, and both current collecting tabs may be deformed, Since the portion where both current collecting tabs are present cannot be fused, the fusion force may be reduced, and the protruding position of both current collecting tabs may be changed depending on the type of battery. This is because if the fusion part is provided, it is necessary to change the equipment, and the manufacturing cost increases. In addition, if a fusion part is provided on the side where both current collecting tabs protrude, it is difficult to check the fusion part due to the presence of both current collecting tabs, but the fusion part is located on the side where both current collecting tabs do not protrude. If there is provided, there is also an advantage that such inconvenience can be avoided.

It is desirable that a non-fused portion is provided on the side of the bag-like separator where the fused portion is provided.
If the non-fused part is not provided on the side where the fused part is provided, there will be no escape from the shrinkage of the separator caused by the fusion, so the undulation and warpage of the separator will increase, and stacking deviation will easily occur. Because it becomes.

It is desirable that non-fused portions are provided in the corner regions of the bag-like separator.
Since the corner region of the bag-like separator is less susceptible to shrinkage of the separator due to fusion compared to the intermediate region, the waviness and warpage of the separator are particularly large, and stacking deviation is more likely to occur. Therefore, the occurrence of misalignment is prevented by providing a non-fused portion in the corner region of the bag-like separator.
Since the corner region is a very limited region as will be described later, even if a non-fused portion is provided in the region, the probability that the positive electrode protrudes or falls off from the separator is Since there is no great difference from the case where the fusion part is provided in the region, it is considered that there is no functional problem.

It is desirable that the thermal shrinkage rate when the separator is stored at 100 ° C. for 1 hour is 10% or less.
By using a material having a small thermal shrinkage as the material of the separator as in the above configuration, it is possible to suppress the waviness and warpage of the separator, thereby further suppressing the occurrence of misalignment. Examples of such materials include polyethylene (PE), polypropylene (PP), and a composite of PE and PP.

The above-mentioned laminated electrode body may be housed in a single package or a flexible outer package in a state where a plurality of laminated electrode bodies are laminated.
Since a flexible exterior body can be made thinner than a non-flexible exterior body, when a flexible exterior body is used, the occupational accumulation of members not directly involved in power generation And the capacity per volume can be increased. In addition, a laminated film is illustrated as an exterior body which has flexibility.

  According to the present invention, even when a stacking error occurs between the positive electrode and the negative electrode, it is possible to easily check the stacking error, thereby correcting the stacking error and manufacturing an accurate battery. Excellent effect.

  Hereinafter, a prismatic lithium ion battery according to the present invention will be described with reference to FIGS. In addition, the prismatic lithium ion battery in the present invention is not limited to the one shown in the following embodiment, and can be implemented with appropriate modifications within a range not changing the gist thereof.

(Structure of prismatic lithium-ion battery)
As shown in FIGS. 4 and 5, the prismatic lithium ion battery of the present invention includes bag-like separators 3 and negative electrodes 2 each having two separators and having positive electrodes 1 arranged therein, and A laminated electrode body 10 having a structure in which the negative electrode 2 is disposed is provided at the outermost position. A plurality of the laminated electrode bodies 10 are encapsulated together with an electrolytic solution inside an exterior body made of a laminate film (not shown).

As shown in FIG. 1A, the positive electrode 1 is made of a positive electrode active material made of LiCoO ₂ and carbon black on both surfaces of a positive electrode conductive core made of a substantially square aluminum foil (not shown). The positive electrode active material layer 1a composed of a conductive agent and a binder made of polyvinylidene fluoride is provided. The positive electrode 1 has a width L1 of 90 mm and a height L2 of 85 mm, and a positive electrode current collecting tab 11 formed integrally with the positive electrode conductive core from one side of the positive electrode 1. The positive electrode current collecting tab 11 has a structure protruding from the laminated electrode body 10.

As shown in FIG. 1 (c), the bag-like separator 3 is composed of two polypropylene (PP) separators 3a (heat shrinkage rate of 15% when stored at a temperature of 100 ° C. for 1 hour), A fusion part 4 for fusing the separators 3a to a part of the peripheral part of the separator 3a (excluding the peripheral part excluding the corner part described later and excluding the peripheral part from which the positive electrode current collecting tab 11 protrudes). It is the structure which provides. Further, as shown in FIG. 1B, the separator 3a has a substantially square shape with a width L3 of 95 mm and a height L4 of 90 mm. As described above, by providing the fusion part 4 only in a part of the peripheral part (that is, the non-fusion part exists in the peripheral part), the escape of contraction of the separator 3a accompanying the fusion is ensured. The undulation and warpage of the separator 3a are suppressed.
The fusion part 4 is formed so as to form a predetermined angle with each side, and one end 4 a of the fusion part 4 extends to the outer edge 3 b of the bag-like separator 3.

  On the other hand, as shown in FIG. 1 (c), when the fusion part 4 is provided in the opposing peripheral part of the bag-like separator 3, the distance L5 between the other ends 4b and 4b of the fusion part 4 is as described above. The positive electrode 1 is configured to be larger than the width L1. Thereby, the positive electrode 1 can be stored inside the bag-shaped separator 3. Furthermore, the outer edge position (position of the said one end 4a) of the said fusion | fusion part 4 in the said bag-shaped separator 3 is comprised so that it may become the same position in each bag-shaped separator. Thus, when the laminated separator 10 and the negative electrode 2 are alternately arranged to produce the laminated electrode body 10, when the lamination deviation of the bag-like separator 3 does not occur, the above fusion part is confirmed from the lamination direction. 4, the outer edge position (the position of the one end 4a) is straight (see FIG. 5), and when the stacking deviation of the bag-like separator 3 occurs, the outer edge position ( Since the position of the one end 4a is not linear, the misalignment can be easily confirmed (see FIG. 10).

  Here, as described above, in the peripheral portion of the bag-shaped separator 3, the region where the fused portion 4 exists is provided with a non-fused portion, but the corner portion of the bag-shaped separator 3 is also non-fused. Is provided. This is because the corner region of the bag-like separator 3 is less susceptible to shrinkage of the separator due to fusion compared to the intermediate region, so that the waviness and warpage of the separator are particularly large. Therefore, by providing the non-fused portion in the corner region of the bag-like separator 3 as described above, the occurrence of misalignment is suppressed. In the present specification, as shown in FIG. 2, the corner region is a corner 3d of the separator 3a, and a point 3e where the distance L6 from the corner 3d is 1/20 of the width L3 of the separator 3a. And a point 3f at which the distance L7 from the corner 3d is 1/20 of the height L4 of the separator 3a, and an intersection 3g of line segments extending in parallel to each side from the points 3e and 3f. Region (region indicated by hatching in FIG. 2).

  As shown in FIG. 3, the negative electrode 2 is composed of a negative electrode active material made of graphite and a binder made of polyvinylidene fluoride on the front surfaces of both sides of a substantially square negative electrode conductive core (not shown). The negative electrode active material layer 2a is provided. The negative electrode 2 has a width L8 of 95 mm and a height L9 of 90 mm, the same size as the separator 3a, and a negative electrode integrally formed with the negative electrode conductive core from one side of the negative electrode 2. A current collecting tab 12 is provided, and the negative electrode current collecting tab 12 protrudes from the laminated electrode body 10.

(Preparation method of prismatic lithium ion battery)
[Production of positive electrode]
90% by mass of LiCoO ₂ as a positive electrode active material, 5% by mass of carbon black as a conductive agent, 5% by mass of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone as a solvent ( NMP) solution was mixed to prepare a positive electrode slurry. Next, this positive electrode slurry was applied to both surfaces of an aluminum foil (thickness: 15 μm) as a positive electrode current collector. Then, after drying the solvent and compressing to a predetermined thickness with a roller, the positive electrode current collector tab was cut | disconnected so that it might become width L1 and height L2 mentioned above, and the positive electrode current collection tab protruded, and the positive electrode was produced.

[Production of bag-shaped separator with positive electrode arranged inside]
After preparing two PP separators and arranging the positive electrode between the separators, the periphery of the separator was thermally welded to produce a bag-like separator in which the positive electrode was arranged inside.

(Production of negative electrode)
A slurry was prepared by mixing 95% by mass of graphite powder as a negative electrode active material, 5% by mass of polyvinylidene fluoride as a binder, and an NMP solution as a solvent. As a copper foil (thickness: 10 μm). Thereafter, the solvent was dried and compressed to a predetermined thickness with a roller, and then cut to have the above-described width L8 and height L9 and the negative electrode current collecting tab protruded to produce a negative electrode.

[Production of battery]
11 sheets of negative electrodes obtained as described above and 10 sheets of bag-shaped separators with positive electrodes arranged therein were alternately stacked to prepare a stacked electrode body. In addition, the negative electrode was arrange | positioned at the edge part of the lamination direction in this laminated electrode body. Next, after arranging a laminated electrode body between two laminated films having a substantially square shape, the laminated electrode body was arranged in the exterior body by welding three pieces of the laminated film. Finally, after pouring a non-aqueous electrolyte from the opening of the outer package, the battery was fabricated by welding the opening of the outer package. As the non-aqueous electrolyte, a mixed solvent in which ethylene carbonate (EC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 30:70, LiPF ₆ is 1 M (mol / liter). What was melt | dissolved in the ratio was used.

(Example 1)
As the prismatic lithium ion battery of Example 1, a battery manufactured in the same manner as the battery described in the best mode for carrying out the invention was used.
The battery thus produced is hereinafter referred to as the present invention battery A1.

(Example 2)
As shown in FIG. 6, a battery is formed in the same manner as in Example 1 except that the fused portion 4 provided in a part of the peripheral portion of the bag-like separator 3 has a different shape (in a U shape). Was made.
The battery thus produced is hereinafter referred to as the present invention battery A2.

(Example 3)
As shown in FIG. 7, the shape of the fused part 4 provided in a part of the peripheral part of these bag-like separators 3 is different (a slightly thick fused part 4 is provided in parallel to each side), A battery was fabricated in the same manner as in Example 1 above.
The battery thus produced is hereinafter referred to as the present invention battery A3.

Example 4
A battery was fabricated in the same manner as in Example 1 except that a polypropylene separator having a thermal shrinkage of 10% or less when stored at a temperature of 100 ° C. for 1 hour was used.
The battery thus produced is hereinafter referred to as the present invention battery A4.

(Comparative Example 1)
As shown in FIG. 8, the fusion part 4 is provided around the entire periphery of the bag-like separator 3 (excluding the part where the positive electrode current collecting tab 11 protrudes, but including the four corner areas). A battery was fabricated in the same manner as in Example 1 except that the attaching portion 4 did not extend to the outer edge of the bag-like separator 3.
The battery thus manufactured is hereinafter referred to as a comparative battery Z1.

(Comparative Example 2)
As shown in FIG. 9, the fusion part 4 is provided on three sides (excluding the side where the positive electrode current collecting tab 11 protrudes, but including the four corners) of the peripheral part of the bag-like separator 3. A battery was fabricated in the same manner as in Example 1 except that the fused portion 4 did not extend to the outer edge of the bag-like separator 3.
The battery thus produced is hereinafter referred to as a comparative battery Z2.

(Experiment)
Since the presence or absence of misalignment and the visibility when misalignment occurred during the production of the above-described inventive batteries A1 to A4 and comparative batteries Z1 and Z2, Table 1 shows the results.

  As is apparent from Table 1, it is recognized that the batteries A1 to A4 of the present invention are less misaligned than the comparative batteries Z1 and Z2, and have excellent visibility when misalignment occurs. This is considered to be due to the following reasons.

(1) Reason why the batteries A1 to A4 of the present invention have less stacking deviation than the comparative batteries Z1 and Z2. In the comparative batteries Z1 and Z2, fusion parts are continuously provided on at least three sides of the peripheral part of the bag-shaped separator. Therefore, there is no escape of the shrinkage of the separator due to fusion, and undulation and warpage increase. On the other hand, in the batteries A1 to A4 of the present invention, the fusion parts are provided at intervals. This is because some relief from the shrinkage of the separator due to wearing is ensured to suppress waviness and warping.

The corner region of the bag-like separator is less susceptible to shrinkage of the separator due to fusion compared to the intermediate region, so that the separator waviness and warpage are particularly large. This is because the fusion part exists in the partial region, but in the batteries A1 to A4 of the present invention, there is no fusion part in the corner region.

-Note that the present invention battery A1 has less stacking deviation than the present invention batteries A2 and A3. In the present invention battery A2, heat concentrates on the top of the cross-section, so that a separator accompanying fusion at that portion. The shrinkage escape of the separator is reduced, and the waving and warping of the separator is slightly increased, and the battery A3 of the present invention has a thicker fusion part than the batteries A1 and A2 of the present invention. Decreases, and the waviness and warpage of the separator slightly increase. On the other hand, in the battery A1 of the present invention, there is no portion where heat is concentrated, and the fusion part is thin, and therefore, the escape of the shrinkage of the separator accompanying the fusion is secured to some extent, and the ripple and warpage of the separator are suppressed. It is.
The reason why the battery A4 of the present invention has a smaller stacking deviation than the battery A1 of the present invention is that the separator of the battery A4 of the present invention has a thermal shrinkage rate of 10% or less when stored at 100 ° C. for 1 hour. This is considered to be because the shrinkage of the separator accompanying the fusion was further suppressed.

(2) Reason why the batteries A1 to A4 of the present invention are superior in visibility when the stacking deviation occurs compared to the comparative batteries Z1 and Z2. In the batteries A1 to A4 of the present invention, one end of the fusion part is a bag-shaped separator. Since the outer edge position of the fused portion is extended to the outer edge and is configured to be the same position in each bag-shaped separator, a laminated electrode body is produced by alternately arranging bag-shaped separators and negative electrodes In addition, when the stacking deviation of the bag-shaped separator occurs, the outer edge position (position of the one end 4a) of the fusion part is not straight when checking from the stacking direction as shown in FIG. I can confirm. On the other hand, in comparative batteries Z1 and Z2, one end of the fused portion is not extended to the outer edge of the bag-shaped separator, so that a laminated electrode body is produced by alternately arranging bag-shaped separators and negative electrodes. In addition, even if a stacking deviation of the bag-shaped separator occurs, it cannot be confirmed.

In addition, when this invention battery A1-A3 was charged / discharged on the following charging / discharging conditions, all the discharge capacity of the 3rd cycle was 2400 mA, and it was recognized that a favorable charging / discharging characteristic is shown.
[Charging / discharging conditions]
A condition that the battery is charged to a charge end potential of 4.2 V at a charge current of 2400 mA (1.0 It) and then discharged to a discharge end potential of 2.8 V at a discharge current of 2400 mA (1.0 It).

(Other matters)
(1) In the above embodiment, the fusion part 4 is provided on the three sides of the bag-like separator 3, but the present invention is not limited to such a configuration, and as shown in FIG. What is necessary is just to provide the melt | fusion part 4 in this. However, when the fusion part 4 is provided on two sides of the bag-shaped separator 3, the positive electrode 1 may move within the bag-shaped separator 3. In addition, as shown in FIG. 12, when the fusion separator 4 is provided only on the two sides of the bag-like separator 3, the bag-like separator 3 is displaced in the direction perpendicular to the side where the fusion part 4 is provided. There may be a case where the stacking error cannot be confirmed. For these reasons, it is desirable to provide the fusion part 4 on three sides of the bag-like separator 3.

(2) In the above embodiment, the shape of the fusion part 4 provided in each bag-like separator 3 is the same shape, but the fusion part 4 may have a different shape as shown in FIGS. good. However, since the outer edge position of the one end 4a of the fused part 4 must be configured to be the same in each bag-like separator, the distance from the corner 3d is the same (L20 = L22 = L24), The thicknesses must also be the same (L21 = L23 = L25). However, the number of the fusion | melting parts 4 provided in each edge | side is not limited to five, What is necessary is just to provide one or more.

(3) The shapes of the positive electrode 1, the negative electrode 2, and the separator 3a are not limited to a square shape, and may be a rectangular shape.
(4) The positive electrode active material is not limited to the above LiCoO ₂ but may be LiNiO ₂ , LiMnO ₄ or a composite thereof, and the negative electrode active material is not limited to the above natural graphite. Artificial graphite or the like may be used.

(5) In the above examples, the negative electrode active material layers were formed on both surfaces of the negative electrode conductive core for all the negative electrodes 2, but the negative electrode active material layers (specifically, not facing the positive electrode) There may be no negative electrode active material layer) present outside the outermost negative electrode. And if it is such a structure, since the thickness of a laminated electrode body will become small, the high capacity density of a battery can be achieved.

  The present invention can be applied to, for example, a robot, an electric vehicle, and a backup power source.

It is a figure which shows a part of prismatic lithium ion battery of this invention, Comprising: The same figure (a) is a top view of a positive electrode, The same figure (b) is a top view of a separator, The same figure (c) is a positive electrode inside. It is a top view which shows the bag-shaped separator arrange | positioned. It is a top view of the separator used for the prismatic lithium ion battery of this invention. It is a top view of the negative electrode used for the prismatic lithium ion battery of this invention. It is a disassembled perspective view of the laminated electrode body used for the square lithium ion battery of this invention. It is a side view of the laminated electrode body used for the square lithium ion battery of this invention. It is a top view which shows the modification of the bag-shaped separator used for the square lithium ion battery of this invention. It is a top view which shows the other modification of the bag-shaped separator used for the square lithium ion battery of this invention. It is a top view which shows the bag-shaped separator used for the conventional square lithium ion battery. It is a top view which shows the other example of the bag-shaped separator used for the conventional square lithium ion battery. It is a side view at the time of lamination | stacking shift | offset | difference having arisen in the lamination | stacking electrode body used for the square lithium ion battery of this invention. It is a front view which shows the other modification of the bag-shaped separator used for the square lithium ion battery of this invention. It is a top view at the time of lamination | stacking shift | offset | difference arising in the laminated electrode body used for the square lithium ion battery of this invention. It is a fragmentary top view which shows the modification of the melt | fusion part of the bag-shaped separator used for the square lithium ion battery of this invention. It is a fragmentary top view which shows the other modification of the melt | fusion part of the bag-shaped separator used for the square lithium ion battery of this invention. It is a fragmentary top view which shows the other modification of the melt | fusion part of the bag-shaped separator used for the square lithium ion battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Positive electrode 1a: Positive electrode active material layer 2: Negative electrode 2a: Negative electrode active material layer 3: Bag-shaped separator 3a: Separator 3b: Outer edge 4: Fusion part 4a: End part 10: Laminated electrode body 11: Positive electrode current collection tab 12 : Negative electrode current collector tab

Claims (7)

A positive electrode having a positive electrode active material layer formed on at least one surface of a positive electrode conductive core made of a rectangular sheet; a positive electrode current collecting tab protruding from one side of the positive electrode conductive core; A negative electrode having a negative electrode active material layer formed on at least one surface of a negative electrode conductive core and having a larger four-sided dimension than the positive electrode; and a negative electrode current collecting tab protruding from one side of the negative electrode conductive core; A bag-shaped separator having a fused portion in which peripheral portions of two rectangular separators are fused to each other and having the positive electrode disposed therein, and the bag-shaped separator and the negative electrode are alternately arranged. In a prismatic lithium ion battery having a structure in which a laminated electrode body is arranged and the positive electrode current collecting tab and the negative electrode current collecting tab protrude from the laminated electrode body,
The fusion part is formed on at least two sides of the bag-like separator, and a part of the fusion part extends to the outer edge of the bag-like separator, and the outer edge position of the fusion part is set to each bag. A prismatic lithium ion battery characterized by being configured to be in the same position with a cylindrical separator.   The prismatic lithium ion battery according to claim 1, wherein the fusion part is provided on three sides of the bag-like separator.   The prismatic lithium ion battery according to claim 2, wherein the positive electrode current collecting tab and the negative electrode current collecting tab protrude from a side of the bag-shaped separator where no fused portion is provided.   The prismatic lithium ion battery according to any one of claims 1 to 3, wherein a non-fused portion is provided on a side of the bag-shaped separator where the fused portion is provided.   The prismatic lithium ion battery according to any one of claims 1 to 4, wherein a non-fused portion is provided in a corner region of the bag-shaped separator.   The prismatic lithium ion battery according to any one of claims 1 to 5, wherein a thermal shrinkage rate when the separator is stored at 100 ° C for 1 hour is 10% or less.   The prismatic lithium ion battery according to any one of claims 1 to 6, wherein the laminated electrode body is housed in a flexible exterior body in a single or a plurality of laminated body.