JP2009252397A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion battery or other batteries (typically a secondary battery) having high output characteristics by suppressing volatilization of an electrolyte within a battery case. <P>SOLUTION: A battery 100 includes: an electrode body 80 including a positive electrode 60 and a negative electrode 70; and a battery case 50 housing the electrode body 80 together with an electrolyte, and a porous body 20 having pores capable of holding the electrolyte is arranged between the electrode body 80 and the battery case 50. The porous body 20 is a porous sheet formed in a sheet shape, and wound so as to cover the outer surface 81 of the electrode body 80. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery, and more particularly, to a battery including an electrode body that is accommodated in a battery case together with an electrolytic solution.

  In recent years, lithium-ion batteries, nickel-metal hydride batteries, and other secondary batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and portable terminals. In particular, a lithium ion battery that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle. Such a lithium ion battery generally contains a battery element (electrode body unit) obtained by winding (or laminating) a positive electrode and a negative electrode through a separator in a battery case, and then an electrolytic solution from an injection port of the battery case. The liquid injection port is then sealed with a sealing plug or the like.

By the way, in this kind of lithium ion battery, liquid withering due to electrolytic solution decomposition accompanying charging / discharging (a portion where the electrolytic solution does not exist locally is generated in the active material layer constituting the positive electrode and the negative electrode) In order to suppress precipitation of metal and metallic lithium, a technique for introducing an electrolyte solution holding agent into the active material layer has been proposed. For example, Patent Document 1 discloses a technique in which an electrolytic solution is held around active material particles by covering the entire surface of the active material particles with a binder containing a conductive agent.
JP 2003-331823 A

  However, in the technique of Patent Document 1, it is possible to suppress the liquid withering in the active material layer due to the electrolytic solution decomposition accompanying charging and discharging, but the liquid withstanding of the electrolyte due to the change in the internal pressure in the battery case is suppressed. I can't do it. That is, when the internal pressure of the battery case decreases with the aging of the battery, the electrolyte solution having a relatively high vapor pressure volatilizes easily with the passage of time. . Thus, when the amount of the electrolyte decreases due to the change in the internal pressure in the battery case, the battery output characteristics (for example, high-rate discharge characteristics) decrease due to the deposition of metallic lithium, or the freezing point of the electrolyte changes and the required temperature output characteristics There is a possibility that various troubles such as failure to obtain the above occur.

  The present invention has been made in view of such points, and its main purpose is to suppress the volatilization of the electrolyte in the battery case and to provide a lithium ion battery or other battery (typically, excellent battery output characteristics). Secondary battery).

  A battery (typically a lithium ion battery or other secondary battery) provided by the present invention includes an electrode body including a positive electrode and a negative electrode, and a battery case that houses the electrode body together with an electrolytic solution. A porous body having pores capable of holding an electrolytic solution is disposed between the electrode body and the battery case. And the said porous body is formed in the elongate sheet form, and is wound so that at least one part of the outer surface of the said electrode body may be covered.

  According to such a configuration, the porous sheet having pores capable of holding the electrolytic solution between the electrode body and the battery case (preferably the average pore diameter of the porous sheet is in the range of 0.5 nm to 5 μm. Therefore, the volatilization of the electrolytic solution accompanying the change in the internal pressure of the battery case (and the decrease in the amount of the electrolytic solution in the battery case) can be suppressed. In addition, since the porous sheet is wrapped around and coated on at least a part of the outer surface of the electrode body, the electrolytic solution can be held in the vicinity of the outer surface of the electrode body. Thereby, the withering phenomenon of the electrolytic solution (a situation in which an insufficient portion of the electrolytic solution with respect to the electrode body is locally generated) can be prevented. Moreover, when comprising a lithium ion battery, the local precipitation of metallic lithium can be prevented evenly. As a result, a battery excellent in battery output characteristics (for example, high rate discharge characteristics) and temperature characteristics (for example, output characteristics at a low temperature) can be provided.

  Preferably, the average pore diameter of the porous sheet is in the range of 0.5 nm to 5 μm. A porous sheet having such an average pore size (typically a pore size approximating the peak value of the pore size distribution) is excellent in electrolyte retention performance.

  In addition, the said porous body sheet should just be comprised from the porous material which can hold | maintain electrolyte solution around an electrode body by the connection of an independent hole or many pores. The shape of the pores only needs to be a shape that can hold the electrolyte solution (for example, a shape that can store the electrolyte solution inside the pores), and may be any of a slit shape, a cylinder shape, and the like.

The porous sheet is preferably made of a material having an insulating property (preferably an electrical conductivity of 10 ⁻⁷ Ω ⁻¹ cm ⁻¹ or less), and further has an electrolytic solution resistance (particularly an electrolytic solution corrosion resistance). It is particularly preferable that it is made of a material having it. An example of such a material is a synthetic resin material. For example, polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), or a combination thereof can be suitably used. In general, a porous material made of synthetic resin (for example, made of polyolefin resin) has mechanical strength and chemical stability suitable for the purpose of the present invention, and can be procured at low cost.

  In a preferred embodiment of the battery disclosed here (typically a secondary battery such as a lithium ion battery), an insulating (for example, synthetic resin) nonwoven fabric sheet is used as the porous sheet. It is characterized by that. In general, the nonwoven fabric sheet has a high porosity (typically 40% or more, for example, 50 to 70%), and can realize high electrolytic solution holding performance (electrolytic solution holding capacity).

  In one preferable embodiment of the battery disclosed herein (typically, a secondary battery such as a lithium ion battery), the electrode body has an electrode active material layer on the surface of a long current collector. It is a wound electrode body obtained by winding the formed positive electrode sheet and negative electrode sheet. And the said porous body sheet is wound along the winding surface (outer peripheral surface) of the said winding electrode body. By winding the porous sheet along the wound surface (outer peripheral surface) of such a wound electrode body, a gap (typical) between the wound surface (outer peripheral surface) of the wound electrode body and the inner wall of the battery case is typical. Can effectively utilize the dead space, and can efficiently accommodate the porous sheet in the internal space of the battery case. Thereby, the battery (lithium ion battery etc.) provided with the porous body sheet suitable for the objective of this invention can be provided, without enlarging battery size. Moreover, according to the said structure, a porous body sheet can be accommodated in a battery case in the state wound beforehand on the winding surface of the winding electrode body in the manufacture stage, and those accommodation operations become easy.

  In a battery of a type including the wound electrode body (typically a secondary battery such as a lithium ion battery), preferably, the positive electrode sheet and the negative electrode sheet are each provided with the active material layer on the surface of the current collector. The positive electrode active material layer non-formed part and the negative electrode active material layer non-formed part are not provided along one end in the width direction of the current collector. At the end in the winding axis direction of the wound electrode body, the positive electrode active material layer non-formed part protrudes from the negative electrode sheet, and the positive electrode side protruding part is wound, and the negative electrode active material layer non-formed part is A negative electrode side protruding portion that is wound out from the positive electrode sheet is formed. In addition, a wound core portion in which the positive electrode active material layer of the positive electrode sheet and the negative electrode active material layer of the negative electrode sheet are stacked is formed at a central portion in the winding axis direction of the wound electrode body. And the said porous body sheet is arrange | positioned so that it may become the positional relationship facing the outer surface of the said winding core part at least. Thus, the positive electrode active material layer and the negative electrode active material are disposed by arranging the porous sheet so as to face the outer surface of the wound core portion in which the positive electrode active material layer and the negative electrode active material layer are laminated. The electrolytic solution can be effectively retained with respect to the layer, and the liquid withdrawing phenomenon of the electrolytic solution in the positive electrode active material layer and the negative electrode active material layer can be effectively prevented. Moreover, in the case of a lithium ion battery, local precipitation of metallic lithium can be effectively prevented.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Hereinafter, the structure of the battery of the present invention will be described in detail by taking the prismatic lithium ion secondary battery 100 as an example, but the present invention is not intended to be limited to the one described in the embodiment. Further, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect actual dimensional relationships.

  The configuration of the battery 100 will be described with reference to FIG. FIG. 1 is a perspective view schematically showing the external appearance of the lithium ion secondary battery according to the present embodiment. As shown in FIG. 1, a lithium ion secondary battery 100 disclosed herein includes an electrode body 80 including a positive electrode 60 and a negative electrode 70, and a rectangular battery case 50 that accommodates the electrode body 80.

  The battery case 50 includes a battery case main body 52 and a lid 54. The battery case main body 52 may be in any shape that can accommodate the electrode body 80, and in this embodiment, has a box shape that can accommodate the flat electrode body 80. Moreover, the battery case main body 52 has an open end (not shown) in the upper part, and can accommodate the electrode body 80 through the said open end. The lid 54 is a plate-like member that closes the open end of the battery case main body 52, and after being attached to the open end of the case main body 52, the meeting portion is joined. The material of the battery case main body 52 and the lid 54 is preferably a light metal material with good thermal conductivity, and for example, aluminum, stainless steel, nickel-plated steel, or the like can be preferably used.

A liquid injection port 40 is formed on the upper surface of the lid 54, and the electrolytic solution can be injected into the battery case through the liquid injection port 40. The liquid injection port 40 is normally sealed with a sealing plug 42. As the electrolytic solution that can be injected into the battery case 50, for example, a nonaqueous electrolytic solution in which an electrolyte is dissolved in a nonaqueous solvent can be used. In this embodiment, a mixed solvent of diethyl carbonate and ethylene carbonate (for example, a mass ratio of 1: 1) is used as the nonaqueous solvent, lithium hexafluorophosphate (LiPF ₆ ) is used as the electrolyte, and the concentration is It is adjusted to about 1 mol / liter.

  Next, the internal structure of the battery 100 according to this embodiment will be described with reference to FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II-II in FIG. An electrode body 80 is accommodated in the battery case 50 together with the above-described electrolyte. The electrode body 80 is made of a predetermined battery constituent material (active material for each of the positive and negative electrodes, current collector for each of the positive and negative electrodes, a separator, etc.) in the same manner as an electrode body of a normal lithium ion battery. In addition, a flat wound electrode body 80 described later is used as the electrode body 80 here.

  Between the wound electrode body 80 and the battery case 50, a porous body 20 having pores capable of holding an electrolytic solution is disposed. The porous body 20 has a large number of pores (voids) (not shown), and can hold the electrolyte contained in the battery case 50 by the independent pores (or the connection or voids of the many pores). It is like that. The shape of the pores only needs to be a shape that can hold the electrolyte solution (for example, a shape that can store the electrolyte solution inside the pores), and may be any of a slit shape, a cylinder shape, and the like. The porous body 20 is a porous sheet formed in a sheet shape, and is wound so as to cover at least a part of the outer surface 81 of the wound electrode body 80. In this embodiment, a non-woven fabric sheet made of synthetic resin (for example, polyolefin resin such as polypropylene) is used as the porous sheet 20, and is tripled from the top of the wound electrode body 80 along the wound surface 81 ( 3 laps).

  In carrying out the present invention, the porous sheet may be wound so as to cover at least a part of the outer surface of the electrode body, and the degree of winding is not particularly limited. For example, the degree of winding may vary depending on the thickness of the porous sheet and the electrolytic solution holding performance (electrolytic solution holding capacity). Typically, it is wound 1 to 10 times along the outer surface of the electrode body so as to cover at least a part of the outer surface of the electrode body (for example, at least the outer peripheral surface of the wound core portion 82 in the wound electrode body 80). For example, in a preferred embodiment of the present invention, the gap (dead space) between the outer surface (for example, the winding surface) of the electrode body and the inner wall of the battery case is wound to such an extent that it can be filled (filled) with the porous sheet. is there.

  According to the configuration of the battery 100 of the present embodiment, since the porous sheet 20 having pores capable of holding the electrolytic solution is disposed between the electrode body 80 and the battery case 50, the internal pressure of the battery case 50 is The volatilization of the electrolytic solution accompanying the change (and the decrease in the amount of the electrolytic solution in the battery case 50) can be suppressed. In addition, since the porous sheet 20 is wrapped around the outer surface 81 of the electrode body 80 and covered, the electrolyte solution is biased over the entire portion 82 where the active material layers of the positive and negative electrodes of the electrode body 80 are present. It can be held without. Thereby, the withering phenomenon of the electrolytic solution (a situation in which an insufficient portion of the electrolytic solution with respect to the electrode body is locally generated) can be prevented. Moreover, when a lithium ion battery is configured as in this embodiment, local precipitation of metallic lithium can be prevented without any bias. As a result, the battery 100 excellent in battery output characteristics (for example, high rate discharge characteristics) and temperature characteristics (for example, output characteristics at a low temperature) can be provided.

The porous sheet 20 is preferably made of a material having an insulating property (preferably an electric conductivity of 10 ⁻⁷ Ω ⁻¹ cm ⁻¹ or less), and further has an electrolytic solution resistance (particularly an electrolytic solution corrosion resistance). It is particularly preferable that it is made of a material that also has. An example of such a material is a synthetic resin material. For example, polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), or a combination thereof can be suitably used. In general, a porous material made of synthetic resin (for example, made of polyolefin resin) has mechanical strength and chemical stability suitable for the purpose of the present invention, and can be procured at low cost.

  A non-insulating (conductive) porous sheet can also be used. In that case, the surface of the porous sheet may be subjected to an insulating treatment (for example, an insulating film, for example, a resin coating layer may be formed). It is preferable to keep it.

  Or you may use a nonwoven fabric sheet as the porous sheet 20 like this embodiment. The nonwoven fabric sheet has a high porosity (typically 40% or more, for example, 50 to 70%), and can realize a high electrolyte solution holding performance (electrolyte solution holding capacity). A non-woven fabric sheet made of synthetic resin is particularly preferable from the viewpoints of chemical stability and insulation.

  Moreover, the average pore diameter of the porous sheet 20 is preferably in the range of 0.5 nm to 5 μm. A porous sheet having such an average pore size (typically a pore size approximating the peak value of the pore size distribution) is excellent in electrolyte retention performance. Specifically, if the pore size of the porous sheet (typically the pore size approximating the peak value of the pore size distribution) is too larger than the above range, the electrolyte molecules that have entered the pores are outside the pores. Since it is easily released into the pores, the pores cannot be provided with a sufficient holding capacity of the electrolytic solution. Therefore, the average pore diameter of the porous sheet is desirably a size (preferably 5 μm or less) that can provide a sufficient holding ability to appropriately restrain the electrolyte that has entered the pores. On the other hand, when the pore size (pore size distribution) of the porous sheet 20 is too smaller than this range, electrolyte molecules cannot enter the pores. Therefore, the pore diameter of the porous sheet 20 needs to be a size (preferably 0.5 nm or more) that allows electrolyte molecules to enter.

  Here, the average value (average pore diameter) of the pores formed in the porous sheet 20 is obtained, for example, by a nitrogen adsorption method. The measurement of the pore diameter (average pore diameter and pore diameter distribution) by the nitrogen adsorption method is easily performed using, for example, a commercially available high-functional specific surface area / pore distribution measuring apparatus (for example, ASAP2020) manufactured by Shimadzu Corporation. Can do.

  Further, the configuration of the battery 100 according to the present embodiment, in particular, the characteristics of the electrode body 80 and the porous sheet 20 will be described with reference to FIG. As described above, the flat wound electrode body 80 is used here as the electrode body 80. The wound electrode body 80 is formed by winding a sheet-like electrode body 90 as shown in FIG. The sheet-like electrode body 90 has a long (band-like) sheet structure in a stage before assembling the wound electrode body 80. The sheet-like electrode body 90 is formed by laminating a positive electrode sheet 60 and a negative electrode sheet 70 together with a total of two separator sheets 92 and 94 in the same manner as a typical wound electrode body.

  The positive electrode sheet 60 is formed by attaching a positive electrode active material layer 62 for a battery to both surfaces of a long sheet-like foil-shaped positive electrode current collector (hereinafter referred to as “positive electrode current collector foil 64”). However, the positive electrode active material layer 62 is not attached to one side edge (upper side edge portion in the drawing) along the edge in the width direction of the sheet-like electrode body 90, and the positive electrode current collector 64 has a constant width. An exposed positive electrode active material layer non-forming portion 66 is formed. Similarly to the positive electrode sheet 60, the negative electrode sheet 70 is formed by attaching a negative electrode active material layer 72 for a battery to both surfaces of a long sheet-like foil-shaped negative electrode current collector (hereinafter referred to as “negative electrode current collector foil 74”). Has been. However, the negative electrode active material layer 72 is not attached to one side edge (the lower side edge portion in the drawing) along the widthwise end of the sheet-like electrode body 90, and the negative electrode current collector 74 has a certain width. A negative electrode active material layer non-forming portion 76 exposed at is formed.

  When constructing the wound electrode body 80, a sheet-like electrode body 90 in which a positive electrode sheet 60 and a negative electrode sheet 70 are laminated via separator sheets 92 and 94 is prepared. At this time, the separator sheets 92 and 94 are arranged so that the positive electrode active material layer non-formation part (exposed part of the positive electrode current collector foil 64) 66 of the positive electrode sheet 60 protrudes outward (that is, the positive electrode active material layer 62 and the separator sheet 92, 94 to face each other). The negative electrode sheet 70 is also laminated in the same manner as the positive electrode sheet 60, so that the negative electrode active material layer non-forming part (exposed part of the negative electrode current collector foil 74) 76 protrudes outward from the separator sheets 92 and 94 (that is, the negative electrode active material layer). 72 and separator sheets 92 and 94 are overlapped). A flat wound electrode body 80 is obtained by winding the sheet-like electrode body 90 and then crushing the obtained wound body from the lateral direction and causing the abduction.

  A wound core portion 82 (that is, a positive electrode active material layer 62 of the positive electrode sheet 60, a negative electrode active material layer 72 of the negative electrode sheet 70, and separator sheets 92 and 94) is provided at a central portion in the winding axis direction of the wound electrode body 80. A densely stacked portion) is formed. Further, the positive electrode side protruding portion 84 where the positive electrode active material layer non-forming portion 66 (exposed portion of the positive electrode current collector foil 64) protrudes from one end portion in the winding axis direction of the wound electrode body 80 is wound. (Positive electrode current collector foil laminated portion having a structure in which foil-like positive electrode current collectors are laminated) is formed. The negative electrode active material layer non-forming portion 76 (exposed portion of the negative electrode current collector foil 74) protrudes from the other end portion in the winding axis direction of the wound electrode body 80, and the negative electrode side protruding portion 86 wound. (Negative electrode current collector foil laminated part having a structure in which foil-like negative electrode current collectors are laminated) is formed.

  The wound electrode body 80 obtained in this way is housed in the battery case 50 so that the winding axis direction is the horizontal direction (left-right direction in the figure) as shown in FIG. In the illustrated example, the positive electrode side protruding portion 84 and the negative electrode side protruding portion 86 are provided with a positive electrode current collecting member 32 and a negative electrode current collecting member 34, respectively, and are electrically connected to the positive electrode terminal 36 and the negative electrode terminal 38. Is done. The positive electrode terminal 36 and the negative electrode terminal 38 are each attached to the lid 54 of the battery case 50 via a gasket (not shown).

  In the present embodiment, the porous sheet 20 is wound along the wound surface 81 of the wound electrode body 80. The porous sheet 20 is disposed at a position facing at least the outer surface 81 of the wound core portion 82. In the illustrated example, the porous sheet 20 is interposed between the positive electrode current collecting member 32 and the negative electrode terminal 38 projecting from both ends of the wound electrode body 80 to expose the entire surface 81 of the wound core portion 82. It coats without.

  By winding the porous sheet 20 along the winding surface 81 of such a wound electrode body 80, a gap (typically a dead space) between the winding surface 81 and the battery case inner wall is effectively used. The porous sheet 20 can be efficiently accommodated in the internal space of the battery case 50. Thereby, the battery 100 (here lithium ion battery) provided with the porous sheet 20 suitable for the object of the present embodiment can be provided without increasing the battery size. Moreover, according to the said structure, the porous body sheet | seat 20 can be accommodated in a battery case in the state wound beforehand on the winding surface (outer peripheral surface) of the winding electrode body 80 in the manufacture stage, and those accommodation operations are possible. It becomes easy.

  In addition, in this way, the porous sheet 20 is arranged so as to be opposed to the outer surface of the wound core portion 82 in which at least the positive electrode active material layer 62 and the negative electrode active material layer 72 are laminated (that is, And at least covering the wound core portion 82), the electrolytic solution can be effectively held in the positive electrode active material layer 62 and the negative electrode active material layer 72, and the positive electrode active material layer 62 and the negative electrode The withering phenomenon of the electrolyte in the active material layer 72 can be effectively prevented. Further, as in this embodiment, in the case of a lithium ion battery, local precipitation of metallic lithium can be effectively prevented.

  In addition, the material and member itself which comprise the winding electrode body 80 may be the same as that of the electrode body of the conventional lithium ion battery, and there is no restriction | limiting in particular. For example, the positive electrode sheet 60 is formed by applying a positive electrode active material layer for a lithium ion battery on a long positive electrode current collector (in this embodiment, an aluminum foil). On the other hand, the negative electrode sheet 70 is formed by applying a negative electrode active material layer for a lithium ion battery on a long negative electrode current collector (copper foil in this embodiment). Examples of suitable separator sheets 92 and 94 interposed between the positive and negative electrode sheets 60 and 70 include those made of a porous polyolefin resin. For example, a porous separator sheet made of synthetic resin (for example, made of polyolefin such as polyethylene) having a thickness of 5 to 30 μm and an average pore diameter of about 0.1 μm can be suitably used.

In order to confirm that by constructing a battery using the porous sheet 20 according to the present embodiment, it is possible to suppress the volatilization of the electrolytic solution accompanying the change in the internal pressure of the battery case, the following tests were conducted as test examples. That is, a test battery is constructed using four porous sheets having different average pore diameters, holes (5 mmφ) are opened in each battery case, and the internal pressure of the case is changed. The number of days until doubling was measured and evaluated. Details will be described below.
<Test Example 1>
89% by mass of lithium nickel oxide (Li ₂ NiO ₃ ) as a positive electrode active material, 5% by mass of acetylene black as a positive electrode conductive agent, 5% by mass of PTFE as a positive electrode binder, and carboxymethylcellulose (as a thickener) CMC) 1% by mass and dispersed in a suitable solvent (water) to prepare a positive electrode material paste, this paste was applied to a positive electrode current collector (aluminum foil, thickness 10 μm, length 2 m), and positive electrode current collector A positive electrode sheet in which positive electrode material layers (density 1.8 g / ml) were provided on both sides of the body was produced. On the other hand, 98% by mass of graphite (C) as a negative electrode active material is dispersed in an appropriate solvent (water) together with 1% by mass of styrene-butadiene rubber (SBR) as a negative electrode binder and 1% by mass of CMC as a thickener. A negative electrode material paste is prepared, and this paste is applied to a negative electrode current collector (copper foil, thickness 10 μm, length 2 m), and a negative electrode sheet in which negative electrode material layers are provided on both sides of the negative electrode current collector Was made. Then, these positive electrode sheet and negative electrode sheet are wound through two separator sheets (porous polypropylene (PP), thickness 30 μm, 2 m), and the wound wound electrode body is crushed from the side surface direction. Thus, a flat wound electrode body was produced.

Next, a porous sheet (specifically, a nonwoven fabric sheet made of polypropylene, having a thickness of 100 μm and a length of 7 cm) having an average pore diameter of about 2 μm is wound around the wound surface of the wound electrode body thus obtained 6 times. I wrapped it. Next, the electrode body was housed in a battery case together with a porous sheet. Thereafter, an electrolyte was injected from the liquid inlet of the battery case and the liquid inlet was sealed to construct a test battery (Test Example 1). As the electrolytic solution, 50 ml of about 1 M LiPF ₆ dissolved in a 1: 1 (mass ratio) mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was used.
<Test Examples 2 to 4>
As Test Examples 2 to 4, batteries were constructed by changing the pore diameter of the porous sheet. Specifically, a test battery was constructed using porous sheets having an average pore diameter increased to 5 μm, 10 μm, and 20 μm in the order of Test Examples 2 to 4. In addition, it produced on the conditions similar to Test Example 1 except having changed the pore diameter of the porous sheet.
<IV resistance measurement>
The IV resistance of the test batteries of Test Examples 1 to 4 manufactured as described above was measured. The IV resistance was measured by first charging each battery from 0 V to 4.0 V at room temperature and then holding it at 50 ° C. for 40 hours. Thereafter, a hole (5 mmφ) was opened in the case of each battery and left at 25 ° C. as it was. Then, the IV resistance was measured every 24 hours, and the number of days until the resistance value was twice the initial resistance (the resistance value measured first) was evaluated. The results are shown in FIG. In FIG. 4, the horizontal axis represents the average pore diameter of the porous sheet, and the vertical axis represents the number of days spent until the IV resistance becomes twice the initial resistance. The initial resistance of the IV resistance was 4.2 mΩ in any of the batteries of Test Examples 1 to 4.

  As is clear from FIG. 4 and Table 1, the batteries using the porous sheet having pores of 5 μm or less (Test Examples 1 and 2) are the batteries using the porous sheet having pores of 10 μm or more (Test). Compared to Examples 3 and 4), it was found that the number of days spent until the IV resistance doubled the initial resistance was significantly longer (50 days or more in this experimental result). This is because batteries (Test Examples 1 and 2) using a porous sheet having pores of 5 μm or less suppress the volatilization of the electrolyte over a long period of time even after the sealing performance of the battery is impaired. It is thought that it was made. From this, it was confirmed that the porous sheet having an average pore diameter of 5 μm or less is particularly excellent in electrolytic solution holding performance.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, in this specification, the “battery” refers to a power storage device that can extract predetermined electrical energy, and is not limited to a specific power storage mechanism (configuration of an electrode body or an electrolyte). A lithium secondary battery such as a lithium ion battery, a nickel hydride secondary battery or other secondary battery, or a capacitor such as an electric double layer capacitor (that is, a physical battery) is a typical example included in the battery herein.

  In addition, the battery 100 including the electrode body 80 around which the porous sheet 20 is wound can exhibit excellent battery output characteristics by suppressing the volatilization of the electrolytic solution in the battery case as described above. It can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as the above. That is, the battery 100 according to this embodiment is arranged as a single battery in a predetermined direction, the battery is constructed by constraining the single battery in the arrangement direction, and the battery is provided as a power source (typically Can provide automobiles, particularly automobiles equipped with electric motors such as hybrid cars, electric cars, and fuel cell cars.

1 is an external perspective view schematically showing an external appearance of a lithium ion secondary battery according to an embodiment of the present invention.

The cross-sectional schematic diagram which shows typically the II-II cross section of FIG. The figure for demonstrating the structure of the wound electrode body which concerns on one Embodiment of this invention. The graph which shows the change of the days spent for the double increase of IV resistance by the difference in the average pore diameter of a porous body sheet.

Explanation of symbols

20 Porous sheet 32 Positive electrode current collecting member 34 Negative electrode current collecting member 36 Positive electrode terminal 38 Negative electrode terminal 40 Injection port 42 Seal plug 50 Battery case 52 Battery case main body 54 Lid 60 Positive electrode sheet 62 Positive electrode active material layer 64 Positive electrode current collector Body 66 Positive electrode active material layer non-formation part 70 Negative electrode sheet 72 Negative electrode active material layer 74 Negative electrode current collector 76 Negative electrode active material layer non-formation part 80 Winding electrode body 81 Outer surface (winding surface)
82 Winding core part 84 Positive electrode side protruding part 86 Negative electrode side protruding part 90 Sheet electrode body 92, 94 Separator sheet 100 Lithium ion secondary battery

Claims (8)

An electrode body comprising a positive electrode and a negative electrode;
A battery case that houses the electrode body together with an electrolyte solution,
Between the electrode body and the battery case, a porous body having pores capable of holding an electrolytic solution is disposed,
Here, the porous body is a porous sheet formed in a sheet shape, and is wound so as to cover at least a part of the outer surface of the electrode body.   The battery according to claim 1, wherein an average pore diameter of the porous sheet is in a range of 0.5 nm to 5 μm.   The battery according to claim 1 or 2, wherein an insulating nonwoven fabric sheet is used as the porous sheet. The electrode body is a wound electrode body formed by winding a positive electrode sheet and a negative electrode sheet in which an electrode active material layer is formed on the surface of a long current collector,
The battery according to any one of claims 1 to 3, wherein the porous sheet is wound along a wound surface of the wound electrode body. Each of the positive electrode sheet and the negative electrode sheet has a positive electrode active material layer non-formation part and a negative electrode active material layer non-formation part in which the active material layer is not formed on the current collector surface in the width direction of the current collector. Provided along one end,
At the end of the wound electrode body in the winding axis direction, the positive electrode active material layer non-formed part is protruded from the negative electrode sheet and wound, and the negative electrode active material layer non-formed part is formed. A negative electrode side protruding portion wound out of the positive electrode sheet is formed,
In the central portion in the winding axis direction of the wound electrode body, a wound core portion in which the positive electrode active material layer of the positive electrode sheet and the negative electrode active material layer of the negative electrode sheet are laminated is formed,
The battery according to claim 4, wherein the porous sheet is disposed at a position facing at least an outer surface of the wound core portion.   The battery according to claim 1, wherein the porous sheet is made of an insulating material.   The battery in any one of Claims 1-6 which comprises a lithium ion battery.   A vehicle comprising the battery according to claim 1.

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