JP4695170B2 - Lithium ion secondary battery - Google Patents

Description

  The present invention relates to a lithium ion secondary battery. More specifically, the present invention mainly relates to an improvement of the current collector.

  Lithium ion secondary batteries have high capacity and high energy density, and are easy to reduce in size and weight. For example, mobile phones, personal digital assistants (PDAs), notebook personal computers, video cameras, and portable games It is widely used as a power source for portable small electronic devices such as electronic machines. In a typical lithium ion secondary battery, a positive electrode containing a lithium cobalt compound as a positive electrode active material, a negative electrode containing a carbon material as a negative electrode active material, and a separator made of a polyolefin porous film are used. This lithium ion secondary battery has high capacity and output, good charge / discharge cycle characteristics, and relatively long service life. However, with the progress of multi-functionality of portable small electronic devices and the need to extend the continuous usable time, it is necessary to further increase the capacity of lithium ion secondary batteries.

  In order to further increase the capacity of the lithium ion secondary battery, for example, development of a high capacity negative electrode active material is underway. As a high-capacity negative electrode active material, an alloy negative electrode active material that can be alloyed with lithium and occludes lithium during charging has attracted attention. Known alloy-based negative electrode active materials include, for example, silicon, tin, oxides thereof, nitrides thereof, compounds containing these, alloys, and the like. The alloy-based negative electrode active material has a high discharge capacity. For example, the theoretical discharge capacity of silicon is about 4199 mAh / g, which is about 11 times the theoretical discharge capacity of graphite conventionally used as a negative electrode active material (see, for example, Patent Document 1).

  The alloy-based negative electrode active material is effective in increasing the capacity of the lithium ion secondary battery. However, there are some problems to be solved in order to put a lithium ion secondary battery containing an alloy-based negative electrode active material into practical use. For example, it is very important to ensure the safety of a lithium ion secondary battery containing an alloy-based negative electrode active material. In addition to lithium ion secondary batteries, secondary batteries may generate heat, although it is extremely rare, due to overcharge, internal short circuit, foreign matter contamination, or other causes. In a lithium ion secondary battery containing an alloy-based negative electrode active material, since the alloy-based negative electrode active material has a high capacity, there is a possibility that the calorific value increases. Therefore, as one of the safety conditions, even if heat is generated, it is required that heat is quickly dissipated and the battery is not heated.

  For example, a battery having a radiation fin has been proposed (see, for example, Patent Document 2). The battery of Patent Document 2 is a wound electrode group in which a rectangular positive electrode, a solid electrolyte, and a rectangular negative electrode are laminated to form a laminated body and wound in a spiral shape around one short side of the obtained laminated body. Is included. The positive electrode includes a rectangular positive electrode current collector provided with heat radiation fins at the long side ends thereof, and a positive electrode active material layer formed on the surface of the positive electrode current collector other than the heat radiation fins. The negative electrode includes a rectangular negative electrode current collector provided with heat radiation fins at the long side ends thereof, and a negative electrode active material layer formed on the surface of the negative electrode current collector other than the heat radiation fins. The radiating fin of the positive electrode current collector is formed with a through-hole in the thickness direction or provided with a notch, and outward from one end of the wound electrode group in a spiral form. It protrudes. Also, the heat dissipating fin of the negative electrode current collector is formed with a through hole in the thickness direction or provided with a notch, and is wound in a spiral form from the other end of the wound electrode group. It protrudes toward.

As described above, the heat dissipating fins of Patent Document 2 have a spiral shape, and the heat dissipating fins are in close proximity, so that the heat dissipating efficiency is insufficient. In particular, the heat radiation efficiency is reduced on the long side where the heat radiation fins of the positive electrode current collector and the negative electrode current collector are not provided. For example, the radiating fin of the negative electrode current collector exists on the long side where the radiating fin of the positive electrode current collector is not provided. However, since there is a solid electrolyte that is not a good heat conductor between the positive electrode and the negative electrode, the heat conduction efficiency between the positive and negative electrodes is not sufficient. Therefore, it is difficult to dissipate the heat on the long side where the radiating fin of the positive electrode current collector is not provided to the outside by the radiating fin of the negative electrode current collector. In this way, it is difficult to dissipate the heat of the entire battery almost uniformly by simply providing the spiral radiating fins.

For this reason, in the technique of patent document 2, the electrical good conductor is connected to the front-end | tip part which a radiation fin protrudes. However, even if such measures are taken, the heat radiation efficiency on the long side where the heat radiation fins are not provided is not sufficiently improved. Further, the use of a good electrical conductor that is an extra part for the battery may complicate the structure of the battery, leading to an increase in the defective product rate in the manufacturing process and an increase in manufacturing cost. Moreover, there is a possibility that new heat generation may be caused by a mounting defect or the like.
Further, in Patent Document 2, the battery according to Patent Document 2 is described as a laminated thin battery, but since a wound electrode group is actually produced, it is not a laminated battery.

  In addition, a solid electrolyte battery including a flat rectangular electrode group and a heat radiation fin (cooling fin) protruding outward from the electrode group from one side of the electrode group has been proposed (see, for example, Patent Document 3). . Also in this battery, the radiation fin is provided as an extension of the current collector. Further, since it is described that the current collector protrudes at least on one side, it is suggested that one current collector is provided with a plurality of heat radiation fins. However, Patent Document 3 adopts a configuration in which a plurality of electrode groups are mounted on a frame in which a plurality of electrode group mounting holes are formed. In order to provide a plurality of radiating fins, it is necessary to make many holes through which the radiating fins penetrate the frame body, and the mechanical strength of the frame body, the ability to hold the electrode group, and the like are reduced. Therefore, it is technically difficult to provide a plurality of radiating fins on one current collector, and specifically disclosed in Patent Document 3 is one radiating fin provided on one current collector. Configuration only.

Thus, heat radiation efficiency is poor only by providing one heat radiation fin. Moreover, in Patent Document 3, since the heat dissipating fins of the electrode groups are arranged close to each other, the heat dissipating efficiency further decreases. For this reason, the heat dissipating fins of the electrode groups are arranged close to each other and electrically connected, but the heat dissipating effect is insufficient.
JP 2002-83594 A JP-A-5-166500 JP-A-9-134931

  An object of the present invention is to provide a lithium ion secondary battery in which the heat generated inside the battery can be efficiently dissipated to the outside and the safety is further improved by a structure that does not complicate the battery structure and decrease the mechanical strength of the battery. Is to provide.

The lithium ion secondary battery according to the first embodiment of the present invention accommodates a flat electrode group formed by laminating a positive electrode, a separator, and a negative electrode in the thickness direction, a nonaqueous electrolyte, a flat electrode group, and a nonaqueous electrolyte. A positive electrode and a negative electrode each having a rectangular current collector body present in the plate electrode group, and an active material capable of inserting and extracting lithium supported on the surface of the current collector body. includes a material layer, the issues collision extends like a hook to the outside of one corner along two sides sandwiching the plate-shaped electrodes of the collector body, and one conjugated without collector body and joint A heat radiation part and a lead part integrated or connected to at least one heat radiation part, the end of which is led out of the battery case , and a projection surface of the positive heat radiation part and a projection surface of the negative heat radiation part preparative do not overlap, the ratio of the area S of the heat radiating portion area S ₀ of the collector body (S S ₀₎ is 0.03 to 1.5, and the outer peripheral length L ₀ of the collector body, the ratio of the length L of the boundary line between the collector body and the discharge heat unit (L / L ₀₎ is equal to or greater than or equal to 0.25.

The lithium ion secondary battery according to the second embodiment of the present invention contains a flat electrode group formed by laminating a positive electrode, a separator, and a negative electrode in the thickness direction, a non-aqueous electrolyte, a flat electrode group, and a non-aqueous electrolyte. A positive electrode and a negative electrode each having a rectangular current collector body present in the plate electrode group, and an active material capable of inserting and extracting lithium supported on the surface of the current collector body. A heat radiation portion that extends in a U-shape and protrudes outward from the plate-like electrode group along the three sides of the current collector body, and is seamlessly integrated with the current collector body, A lead portion that is integrated or connected to at least one heat radiating portion and whose end portion is led out of the battery case, and the projection surface of the positive electrode heat radiating portion and the projection surface of the negative electrode heat radiating portion overlap. The area S of the current collector body ₀ To the area S of the heat radiation part (S / S ₀ ) Is 0.03 to 1.5, and the outer peripheral length L of each current collector body ₀ And the ratio of the length L of the boundary line between each current collector body and each heat radiating portion (L / L ₀ ) Is 0.25 or more.

The lithium ion secondary battery according to the third embodiment of the present invention contains a flat electrode group formed by laminating a positive electrode, a separator, and a negative electrode in the thickness direction, a nonaqueous electrolyte, a flat electrode group, and a nonaqueous electrolyte. A positive electrode and a negative electrode each having a rectangular current collector body present in the plate electrode group, and an active material capable of inserting and extracting lithium supported on the surface of the current collector body. A heat radiation portion that extends outward from the two opposite sides of the current collector main body and protrudes outward from the flat electrode group, and is integrated seamlessly with the current collector main body, and at least one heat radiation portion And a lead portion whose end is led out of the battery case, and the projection surface of the positive electrode heat dissipation portion and the projection surface of the negative electrode heat dissipation portion do not overlap, and the current collector Body area S ₀ To the area S of the heat radiation part (S / S ₀ ) Is 0.03 to 1.5, and the outer peripheral length L of each current collector body ₀ And the ratio of the length L of the boundary line between each current collector body and each heat radiating portion (L / L ₀ ) Is 0.25 or more.

  In the lithium ion secondary battery of the present invention, even if heat is generated due to overcharge, internal short circuit, foreign matter contamination, or other causes, the heat inside the battery is efficiently dissipated outside the battery, leading to high temperatures. There is no. In addition, since the lithium ion secondary battery of the present invention has a very simple heat dissipation mechanism, the battery structure is not complicated, the defective product rate is not increased, and the mechanical strength of the battery is not reduced. . Therefore, the lithium ion secondary battery of the present invention has high safety and high durability.

  FIG. 1 is a longitudinal sectional view schematically showing a configuration of a lithium ion secondary battery 1 according to the first embodiment of the present invention. FIG. 2 is an enlarged top view showing the configuration of the main part of the lithium ion secondary battery 1 shown in FIG. In FIG. 2, the positive electrode active material layer 11, the negative electrode active material layer 13, and the separator 5 are not shown.

  The lithium ion secondary battery 1 includes a positive electrode 3, a negative electrode 4, a separator 5, a gasket 6 and an outer case 7. The lithium ion secondary battery 1 is a stacked battery including a flat electrode group (hereinafter simply referred to as “electrode group”) 2 formed by stacking a positive electrode 3, a separator 5, and a negative electrode 4. The electrode group 2 has a substantially rectangular shape in the thickness direction.

  Since the electrode group 2 is provided with heat radiation portions 10b and 12b, which will be described later, on the positive electrode 3 and the negative electrode 4, respectively, the electrode plate that is the positive electrode 3 and the electrode plate that is the negative electrode 4 are connected to each other through the separator 5 and have a thickness. It is formed by laminating so that an overlapping portion and a non-overlapping portion can be formed in the direction. The overlapping portions are the current collector main bodies 10a and 12a, and the non-overlapping portions are the heat radiating portions 10b and 12b and the lead portions 10c and 12c.

The positive electrode 3 includes a positive electrode current collector 10 and a positive electrode active material layer 11.
The positive electrode current collector 10 includes a current collector body 10a, a heat radiating portion 10b, and a lead portion 10c. The positive electrode current collector 10 includes a current collector body 10a that is a rectangular portion, a heat radiating portion 10b that follows the current collector main body 10a, and a lead portion 10c that follows the heat radiating portion 10b. The current collector body 10a, the heat radiating portion 10b, and the lead portion 10c are integrally formed . Further, the current collector body 10a and the heat radiating portion 10b may be integrally formed, and the lead portion 10c may be connected to the heat radiating portion 10b.
The current collector body 10a is present in the electrode group 2 and is a portion having a substantially rectangular surface shape in the thickness direction. A positive electrode active material layer 11 is formed on the surface of the current collector body 10a in the thickness direction.

The heat radiation part 10b is a bowl-shaped part formed so as to follow the current collector body 10a. Specifically, the heat radiating portion 10b is provided so as to protrude outward from the electrode group 2 from two sides of the current collector body 10a. More specifically, the heat radiating portion 10b is provided so as to protrude outward from the electrode group 2 from a part of two adjacent sides of the current collector body 10a. In other words, the heat radiating portion 10b has two edges or found adjacent to the current collector body 10a, it is integrally formed. In the thickness direction of the electrode group 2, the surface of the heat radiating part 10 b is provided substantially parallel to the surface of the electrode group 2.

  By providing the heat radiating portion 10b in this way, the heat radiating efficiency is improved, and even when abnormal heat generation occurs in the lithium ion secondary battery 1, rapid heat removal is performed. It does n’t come. In the present specification, two adjacent sides are two sides connected via one apex angle in the substantially rectangular current collector body 10a. Further, in this specification, the part of the two sides is a continuous part including each part of the two sides and the apex part.

  The heat radiation part 10b is integrated, and the shape seen from the thickness direction is a bowl shape. By integrating the heat dissipating part 10b without dividing it into a plurality of parts, the heat dissipating area of the heat dissipating part 10b can be increased, and the heat dissipating efficiency can be further improved. Further, since the heat radiation portion 10b and thus the mechanical strength of the lithium ion secondary battery 1 can be improved and the overall weight balance of the lithium ion secondary battery 1 can be homogenized, the long-term durability of the lithium ion secondary battery 1 can be improved. Can be increased.

  Further, as shown in FIG. 2, the heat dissipating part 10b has a portion overlapping the heat dissipating part 12b on the negative electrode 4 side to be described later in the plan view when the electrode group 2 is placed on the horizontal surface so that the positive electrode 3 becomes the bottom surface. There is no provision. This further improves the heat dissipation efficiency.

The area ratio (hereinafter referred to as “positive electrode heat dissipation area S”) of the heat radiating portion 10 b and the surface area S ₀ of the current collector body 10 a (hereinafter referred to as “positive electrode current collector area S ₀ ”) S / S ₀ ) is 0.03 to 1.5. If the area ratio is less than 0.03, the heat dissipation efficiency is lowered, and there is a possibility that exhaust heat at the time of abnormal heat generation becomes insufficient. On the other hand, if the area ratio exceeds 1.5, the heat-radiating part 10b and thus the mechanical strength of the lithium ion secondary battery 1 may be reduced, and the long-term durability of the lithium ion secondary battery 1 may be insufficient.

In addition, the positive electrode heat radiation part area S is an area of one surface of the heat radiation part 10 b in the thickness direction of the electrode group 2. Similarly, the positive electrode current collector area S ₀ is the area of one surface of the current collector body 10 a in the thickness direction of the electrode group 2.

Further, the length L of the boundary line between the current collector body 10a and the heat radiating portion 10b, the ratio of the outer peripheral length L ₀ of the collector body 10a (L / L ₀₎ is Ru der 0.25 or more. Here, the boundary line between the current collector body 10a and the heat radiating portion 10b is a portion indicated by a dotted line in FIG. 2, and the total length of the dotted line portion is the length L. Further, L ₀ is the outer peripheral length of the current collector body 10a, that is, the sum of the lengths of the four sides of the current collector body 10a, which is a rectangular portion. By setting the ratio (L / L ₀ ) to 0.25 or more, the heat dissipation efficiency by the heat dissipation part 10b is further improved .

  Moreover, you may make the thickness of the thermal radiation part 10b smaller than the thickness of the collector main body 10a. Thereby, the heat dissipation efficiency can be further increased. At this time, the thickness of the heat radiating portion 10b can be appropriately selected according to the thickness of the current collector main body 10a, and it is preferable to select a range in which the mechanical strength does not significantly decrease. In order to reduce the thickness of the heat radiating portion 10b, for example, press working or the like can be used.

  Furthermore, a plurality of through holes in the thickness direction, cutout portions, and the like may be formed in the heat radiating portion 10b as long as the mechanical strength is not impaired. Moreover, the surface of the heat radiation part 10b in the thickness direction is insulated by, for example, a thermoplastic resin layer (not shown). For example, modified polypropylene is used for the thermoplastic resin layer.

  The lead portion 10c is a bowl-shaped portion formed so as to follow the heat radiating portion 10b. More specifically, the lead part 10c is provided so as to protrude outward from the electrode group 2 from a part of two adjacent sides of the heat dissipation part 10b. In addition, one end of the lead portion 10 c is connected to the heat radiating portion 10 b, and the other end is led out of the lithium ion secondary battery 1 from the opening 7 a of the outer case 7.

  By providing the lead portion 10c with the above-described configuration, the lead portion 10c not only supplies power to the outside of the lithium ion secondary battery 1, but also exhibits a heat dissipation function as an extension of the heat dissipation portion 10b. It gets even higher. In particular, since the other end of the lead portion 10c is led out to the outside of the lithium ion secondary battery 1, heat is radiated by the lead portion 10c outside the lithium ion secondary battery 1, and the heat radiation effect is enhanced.

The lead portion 10c is formed of the same material as the current collector main body 10a and the heat radiating portion 10b . The lead portion 10c is not limited to the hook shape, and may be provided as a thin wire lead as in the conventional case.

  As the positive electrode current collector 10, those commonly used in this field can be used. For example, a porous material made of a metal material such as stainless steel, titanium, aluminum, an aluminum alloy, a clad material of aluminum and stainless steel, or a conductive resin. Or a non-porous conductive substrate. Examples of the porous conductive substrate include a mesh body, a net body, a punching sheet, a lath body, a porous body, a foam, a fiber group molded body (nonwoven fabric, etc.), and the like. Examples of the non-porous conductive substrate include a foil, a sheet, and a film. The thickness of the porous or non-porous conductive substrate is not particularly limited, but is usually 1 to 500 μm, preferably 1 to 50 μm, more preferably 10 to 40 μm, and particularly preferably 10 to 30 μm. For example, the positive electrode current collector 10 is obtained by punching these conductive substrates into a predetermined shape.

  The positive electrode active material layer 11 is provided on one or both surfaces of the current collector body 10a in the thickness direction of the positive electrode current collector 10, and includes a positive electrode active material. Furthermore, the positive electrode active material layer 11 may contain a conductive agent, a binder, and the like together with the positive electrode active material.

  The positive electrode active material is not particularly limited as long as it is a material that can occlude and release lithium ions, but lithium-containing composite metal oxides, olivine-type lithium phosphate, and the like can be preferably used. The lithium-containing composite metal oxide is a metal oxide containing lithium and a transition metal or a metal oxide in which a part of the transition metal in the metal oxide is substituted with a different element. Here, examples of the different element include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B. Among these, Mn, Al, Co, Ni, Mg, etc. are preferable. One kind or two or more kinds of different elements may be used.

Specific examples of the lithium-containing composite metal oxide, for _{example, Li l CoO 2, Li l} NiO 2, Li l MnO 2, Li l Co m Ni 1-m O 2, Li l Co m M 1-m O n Li _l Ni _1-m M _m O _n , Li _l Mn ₂ O ₄ , Li _l Mn _{2 -m} M _m O ₄ , LiMPO ₄ , Li ₂ MPO ₄ F (wherein M is Na, Mg, Sc, It represents at least one element selected from the group consisting of Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb and B. l = 0 to 1.2, m = 0 to 0 .9, m = 2.0 to 2.3).

Here, m value which shows the molar ratio of lithium is a value immediately after positive electrode active material preparation, and increases / decreases by charging / discharging. Among these, (wherein, M, l, m and n are the same. Above) Formula _{Li l Co m M 1-m} O n lithium-containing composite metal oxide represented by are preferred.

  The lithium-containing composite metal oxide can be produced according to a known method. For example, a composite metal hydroxide containing a metal other than lithium is prepared by a coprecipitation method using an alkali agent such as sodium hydroxide, and the composite metal hydroxide is heat treated to obtain a composite metal oxide. A lithium-containing composite metal oxide can be obtained by adding a lithium compound such as lithium hydroxide and further heat-treating it.

Specific examples of the olivine type lithium phosphate include LiXPO ₄ (wherein X is at least one selected from the group consisting of Co, Ni, Mn and Fe).
A positive electrode active material can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

  As the conductive agent, those commonly used in the field of lithium ion secondary batteries can be used. For example, graphites such as natural graphite and artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal Carbon blacks such as black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metals such as titanium oxide Examples thereof include organic conductive materials such as oxides and phenylene derivatives. A conductive agent can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

  As the binder, those commonly used in the field of lithium ion secondary batteries can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, Polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, poly Examples include ether, polyether sulfone, hexafluoropolypropylene, styrene butadiene rubber, modified acrylic rubber, and carboxymethyl cellulose.

  In addition, a copolymer containing two or more monomer compounds may be used as a binder. Examples of the monomer compound include tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, hexadiene, and the like. A binder can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

  The positive electrode active material layer 11 can be formed, for example, by applying a positive electrode mixture slurry to the surface of the positive electrode current collector 10 (current collector body 10a), drying and rolling. The positive electrode mixture slurry can be prepared by dissolving or dispersing a positive electrode active material and, if necessary, a conductive agent and a binder in an organic solvent. As the organic solvent, for example, dimethylformamide, dimethylacetamide, methylformamide, N-methyl-2-pyrrolidone (NMP), dimethylamine, acetone, cyclohexanone and the like can be used. For the preparation of the positive electrode mixture slurry, any of a general mixer, a disperser, etc., for mixing powder and liquid can be used.

  When the positive electrode mixture slurry contains a positive electrode active material, a conductive agent, and a binder, the usage ratio of these three components is not particularly limited, but preferably, the positive electrode active material 80 is used with respect to the total use amount of these three components. It may be used as appropriate so that the total amount becomes 100% by weight within a range of ˜98% by weight, conductive agent 1-10% by weight and binder 1-10% by weight.

  The thickness of the positive electrode active material layer 11 is appropriately selected according to various conditions such as the design performance and application of the obtained lithium ion secondary battery 1. For example, the positive electrode active material layer 11 is formed on both surfaces of the positive electrode current collector 10. In the case where it is provided, the total thickness of the positive electrode active material layer 11 is preferably about 50 to 100 μm.

The negative electrode 4 includes a negative electrode current collector 12 and a negative electrode active material layer 13.
The negative electrode current collector 12 includes a current collector body 12a, a heat radiating portion 12b, and a lead portion 12c. The negative electrode current collector 12 has the same shape as the positive electrode current collector 10. The positive electrode current collector 10 and the negative electrode current collector 12 are such that the intersections of the diagonal lines of the current collector main bodies 10a and 12a are at the same position in the thickness direction and are symmetrical about the intersection. Are arranged.
The current collector main body 12a is present inside the electrode group 2, and is in the same position as the current collector main body 10a of the positive electrode current collector 10 in the thickness direction of the electrode group 2, and has substantially the same rectangular shape. ing. A negative electrode active material layer 13 is formed on one or both surfaces in the thickness direction of the current collector body 12a.

  The heat dissipating part 12b is formed so as to follow the current collector body 12a. More specifically, the heat radiating portion 12b protrudes outward from the electrode group 2 on the side opposite to the heat radiating portion 10b of the positive electrode current collector 10 from a part of two adjacent sides of the current collector body 12a. It is provided to do. The heat radiating part 12b is integrally formed from a part of two adjacent sides of the current collector body 12a. In the thickness direction of the electrode group 2, the surface of the heat radiating portion 12 b is provided substantially parallel to the surface of the electrode group 2. The effect of providing the heat dissipation part 12b is the same as the effect of providing the heat dissipation part 10b.

  The heat radiation part 12b is integrated and the shape seen from the thickness direction is a bowl shape. The heat dissipating part 12b has a symmetrical relationship with the heat dissipating part 10b around the intersection of the diagonal lines of the current collector body 12a. The effect of integrating the heat dissipating part 12b without dividing it into a plurality of parts is the same as the effect of integrating the heat dissipating part 10b.

  In addition, as shown in FIG. 2, when the electrode group 2 is placed on a horizontal plane so that the positive electrode 3 is a bottom surface, the heat radiating unit 12 b is a projection plane when the electrode group 2 is viewed from above in the vertical direction (hereinafter, Is simply provided as a “projection surface” so that there is no portion overlapping the projection surface of the heat dissipating part 10b on the negative electrode 5 side. Thereby, there is no possibility that the heat radiation efficiency is lowered.

In addition, the area ratio of the surface area S of the heat radiating portion 12b (hereinafter referred to as “negative electrode heat radiating portion area S”) to the surface area S ₀ of the current collector body 12a (hereinafter referred to as “negative electrode current collector area S ₀ ”). S / S ₀ ) is 0.03 to 1.5. If the area ratio is less than 0.03, the heat dissipation efficiency is lowered, and there is a possibility that exhaust heat at the time of abnormal heat generation becomes insufficient. On the other hand, if the area ratio exceeds 1.5, the heat dissipating part 12b and thus the mechanical strength of the lithium ion secondary battery 1 may be reduced, and the long-term durability of the lithium ion secondary battery 1 may be insufficient.

In addition, the negative electrode heat radiation part area S is an area of one surface of the heat radiation part 12 b in the thickness direction of the electrode group 2. Similarly, the negative electrode current collector area S ₀ is the area of one surface of the current collector body 12 a in the thickness direction of the electrode group 2.

Further, the length L of the boundary line between the current collector body 12a and the heat radiating portion 12b, the ratio (L / L ₀₎ the outer length L ₀ of the collector body 12a is Ru der 0.25 or more. Here, the boundary line between the current collector main body 12a and the heat radiating portion 12b is a portion corresponding to the dotted line portion of the positive electrode current collector 10 shown in FIG.

In the present embodiment, the negative electrode current collector 12 and the positive electrode current collector 10 have the same shape, and the current collector main bodies 10a and 12a also have the same shape. The boundary line with 12 b has the same length as the dotted line portion of the positive electrode current collector 10. The total length of this dotted line is the length L. L ₀ is the outer peripheral length of the current collector body 12a, that is, the sum of the lengths of the four sides of the current collector body 12a, which is a rectangular portion. By setting the ratio (L / L ₀ ) to 0.25 or more, the heat dissipation efficiency by the heat dissipation part 12b is further improved .

  Moreover, you may make the thickness of the thermal radiation part 12b smaller than the thickness of the collector main body 12a. This effect is also similar to the effect of making the thickness of the heat radiating portion 10b smaller than the thickness of the current collector 10a. At this time, the thickness of the heat radiating portion 12b can be appropriately selected according to the thickness of the current collector body 12a, and it is preferable to select a range in which the mechanical strength does not significantly decrease. In order to reduce the thickness of the heat dissipating part 12b, for example, press working or the like can be used.

  Furthermore, a plurality of through holes in the thickness direction, cutout portions, and the like may be formed in the heat radiating portion 12b as long as the mechanical strength is not impaired. Moreover, the surface of the heat radiation part 12b in the thickness direction is insulated by, for example, a thermoplastic resin layer (not shown). The thermoplastic resin layer is formed using, for example, a thermoplastic resin such as modified polypropylin.

  The lead portion 12c is a bowl-shaped portion formed so as to follow the heat radiating portion 12b. More specifically, the lead part 12c is provided so as to protrude outward from the electrode group 2 from a part of two adjacent sides of the heat dissipation part 12b. The lead portion 12 c has one end connected to the heat radiating portion 12 b and the other end led out of the lithium ion secondary battery 1 from the opening 7 a of the outer case 7.

By providing the lead portion 12c with the above-described configuration, the lead portion 12c not only supplies power to the outside of the lithium ion secondary battery 1, but also exhibits a heat dissipation function as an extension of the heat dissipation portion 12b. In particular, since the other end of the lead portion 12c is led out of the lithium ion secondary battery 1, heat is radiated by the lead portion 12c outside the lithium ion secondary battery 1. Therefore, the heat dissipation effect is further enhanced. The lead portion 12c is formed of the same material as the current collector main body 12a and the heat radiating portion 12b . In addition, the lead part 12c is not limited to a hook-like shape, and may be provided as a thin wire-like lead as in the past.

  As the negative electrode current collector 12, those commonly used in the field of lithium ion secondary batteries can be used. For example, stainless steel, titanium, nickel, aluminum, copper, a copper alloy, a clad material of copper and nickel, copper Examples thereof include a porous or non-porous conductive substrate made of a metal material such as nickel-plated or a conductive resin. Examples of the porous conductive substrate include a mesh body, a net body, a punching sheet, a lath body, a porous body, a foam, a fiber group molded body (nonwoven fabric, etc.), and the like. Examples of the non-porous conductive substrate include a foil, a sheet, and a film. The thickness of the porous or non-porous conductive substrate is not particularly limited, but is usually 1 to 500 μm, preferably 1 to 50 μm, more preferably 10 to 40 μm, and particularly preferably 10 to 30 μm. For example, the negative electrode current collector 12 is obtained by punching these conductive substrates into a predetermined shape.

  The negative electrode active material layer 13 contains an alloy-based negative electrode active material, and is formed in a thin film shape on one surface or both surfaces in the thickness direction of the current collector body 12a. Moreover, the negative electrode active material layer 13 may consist of, for example, an alloy-based negative electrode active material and inevitable impurities contained in a very small amount. Moreover, the negative electrode active material layer 13 may contain a well-known negative electrode active material, an additive, etc. in the range which does not impair the characteristic with an alloy type negative electrode active material. Furthermore, the negative electrode active material layer 13 is preferably an amorphous or low crystalline thin film containing an alloy-based negative electrode active material and having a thickness of 3 to 50 μm.

  The alloy-based negative electrode active material is a negative electrode active material that occludes lithium by being alloyed with lithium at the time of charging and releases lithium at the time of discharging under a negative electrode potential. The alloy-based negative electrode active material is not particularly limited, and known materials can be used, and examples thereof include silicon-containing compounds and tin-containing compounds.

  Examples of the silicon-containing compound include silicon, silicon oxide, silicon nitride, silicon-containing alloy, silicon compound and its solid solution. Examples of the silicon oxide include silicon oxide represented by a composition formula: SiOα (0.05 <α <1.95). Examples of silicon carbide include silicon carbide represented by the composition formula: SiCβ (0 <β <1). Examples of the silicon nitride include silicon nitride represented by the composition formula: SiNγ (0 <γ <4/3).

  Examples of the silicon-containing alloy include an alloy containing silicon and one or more elements selected from the group consisting of Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. It is done. As the silicon compound, for example, a part of silicon contained in silicon, silicon oxide, silicon nitride or silicon-containing alloy is B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Examples thereof include compounds substituted with one or more elements selected from the group consisting of Nb, Ta, V, W, Zn, C, N and Sn. Among these, silicon and silicon oxide are particularly preferable.

Examples of the tin-containing compound include tin, tin oxide, tin nitride, tin-containing alloy, tin compound and its solid solution, and the like. Examples of the tin-containing compound include tin, tin oxide such as SnOδ (0 <δ <2), SnO ₂ , Ni—Sn alloy, Mg—Sn alloy, Fe—Sn alloy, Cu—Sn alloy, Ti—Sn. A tin-containing alloy such as an alloy, or a tin compound such as SnSiO ₃ , Ni ₂ Sn ₄ , or Mg ₂ Sn can be preferably used. Among these, tin and tin oxides such as SnOβ (0 <β <2) and SnO ₂ are particularly preferable. Each of the silicon-containing compound and the tin-containing compound can be used alone or in combination of two or more.

  The negative electrode active material layer 13 can be formed on the surface of the negative electrode current collector 12 according to, for example, a known thin film forming method. Examples of the thin film forming method include a sputtering method, a vapor deposition method, and a chemical vapor deposition (CVD) method. Among these, a vapor deposition method is preferable.

  The separator 5 is provided between the positive electrode 3 and the negative electrode 4. For the separator 5, a sheet-like material or a film-like material having predetermined ion permeability, mechanical strength, insulating properties, and the like are used. Specific examples of the separator 5 include a porous sheet-like material or a film-like material such as a microporous membrane, a woven fabric, and a non-woven fabric. The microporous film may be either a single layer film or a multilayer film (composite film). The single layer film is made of one kind of material. The multilayer film (composite film) is a single-layer film stack made of one material or a single-layer film stack made of different materials.

  Various resin materials can be used as the material of the separator 5, but polyolefins such as polyethylene and polypropylene are preferable in view of durability, shutdown function, battery safety, and the like. The shutdown function is a function that blocks the through-hole when the battery is abnormally heated, thereby suppressing ion permeation and blocking the battery reaction. If necessary, the separator 5 may be formed by laminating two or more layers of microporous membranes, woven fabrics, nonwoven fabrics, and the like.

  The thickness of the separator 5 is generally 10 to 300 μm, preferably 10 to 40 μm, more preferably 10 to 30 μm, and still more preferably 10 to 25 μm. Moreover, the porosity of the separator 5 is preferably 30 to 70%, more preferably 35 to 60%. Here, the porosity is the ratio of the total volume of pores existing in the separator 5 to the volume of the separator 5.

The separator 5 is impregnated with an electrolyte having lithium ion conductivity. As the electrolyte having lithium ion conductivity, a nonaqueous electrolyte having lithium ion conductivity is preferable. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte, a gel-like non-aqueous electrolyte, a solid electrolyte (for example, a polymer solid electrolyte), and the like.
The liquid non-aqueous electrolyte contains a solute (supporting salt) and a non-aqueous solvent, and further contains various additives as necessary. Solutes usually dissolve in non-aqueous solvents. For example, the separator is impregnated with the liquid non-aqueous electrolyte.

As the solute, those commonly used in this field can be used. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylates, LiCl, LiBr, LiI, LiBCl ₄ , borates, imide salts and the like.

  Examples of borates include lithium bis (1,2-benzenediolate (2-)-O, O ') and bis (2,3-naphthalenedioleate (2-)-O, O') boric acid. Lithium, bis (2,2′-biphenyldiolate (2-)-O, O ′) lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid-O, O ′) lithium borate Etc.

Examples of the imide salts include lithium bistrifluoromethanesulfonate imide ((CF ₃ SO ₂ ) ₂ NLi), lithium trifluoromethanesulfonate nonafluorobutanesulfonate ((CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) NLi) ), Lithium bispentafluoroethanesulfonate imide ((C ₂ F ₅ SO ₂ ) ₂ NLi), and the like. A solute may be used individually by 1 type, or may be used in combination of 2 or more type as needed. The amount of the solute dissolved in the non-aqueous solvent is preferably in the range of 0.5 to 2 mol / L.

  As the non-aqueous solvent, those commonly used in this field can be used, and examples thereof include cyclic carbonate esters, chain carbonate esters, and cyclic carboxylic acid esters. Examples of the cyclic carbonate include propylene carbonate (PC) and ethylene carbonate (EC). Examples of the chain carbonate include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and the like. Examples of the cyclic carboxylic acid ester include γ-butyrolactone (GBL) and γ-valerolactone (GVL). A non-aqueous solvent may be used individually by 1 type, or may be used in combination of 2 or more type as needed.

Examples of the additive include a material that improves charge / discharge efficiency and a material that inactivates the battery. A material that improves charge / discharge efficiency, for example, decomposes on the negative electrode to form a film having high lithium ion conductivity, and improves charge / discharge efficiency. Specific examples of such a material include, for example, vinylene carbonate (VC), 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-ethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, 4-propyl vinylene. Examples include carbonate, 4,5-dipropyl vinylene carbonate, 4-phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl ethylene carbonate (VEC), divinyl ethylene carbonate, and the like. These may be used alone or in combination of two or more. Among these, at least one selected from vinylene carbonate, vinyl ethylene carbonate, and divinyl ethylene carbonate is preferable. In the above compound, part of the hydrogen atoms may be substituted with fluorine atoms.

  The material that inactivates the battery inactivates the battery by, for example, decomposing when the battery is overcharged to form a film on the electrode surface. Examples of such a material include benzene derivatives. Examples of the benzene derivative include a benzene compound containing a phenyl group and a cyclic compound group adjacent to the phenyl group. As the cyclic compound group, for example, a phenyl group, a cyclic ether group, a cyclic ester group, a cycloalkyl group, a phenoxy group and the like are preferable. Specific examples of the benzene derivative include cyclohexylbenzene, biphenyl, diphenyl ether, and the like. A benzene derivative can be used individually by 1 type, or can be used in combination of 2 or more type. However, the content of the benzene derivative in the liquid nonaqueous electrolyte is preferably 10 parts by volume or less with respect to 100 parts by volume of the nonaqueous solvent.

  The gel-like non-aqueous electrolyte includes a liquid non-aqueous electrolyte and a polymer material that holds the liquid non-aqueous electrolyte. The polymer material used here is capable of gelling a liquid material. As the polymer material, those commonly used in this field can be used, and examples thereof include polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polyvinyl chloride, polyacrylate, and polyvinylidene fluoride.

  The solid electrolyte includes, for example, a solute (supporting salt) and a polymer material. Solutes similar to those exemplified above can be used. Examples of the polymer material include polyethylene oxide (PEO), polypropylene oxide (PPO), a copolymer of ethylene oxide and propylene oxide, and the like.

  The gasket 6 is used to seal the openings 7 a and 7 b of the outer case 7. For the gasket 6, for example, various resin materials, various rubber materials and the like can be used. As the outer case 7, any one commonly used in the field of lithium ion secondary batteries can be used. Note that the openings 7a and 7b of the outer case 7 may be directly sealed by welding or the like without using the gasket 6.

  The lithium ion secondary battery 1 can be manufactured as follows, for example. First, the positive electrode 3 and the negative electrode 4 are laminated via the separator 5 to produce the electrode group 2. At this time, the positive electrode 3 and the negative electrode 4 are disposed so that the positive electrode active material layer 11 and the negative electrode active material layer 13 face each other. The electrode group 2 is inserted into the outer case 7, and the free end portions of the positive electrode lead portion 10c and the negative electrode lead portion 12c are led out of the outer case 7 from the openings 7a and 7b. Next, a nonaqueous electrolyte is injected into the outer case 7, and the openings 7 a and 7 b are welded through the gasket 6 while vacuuming the inside of the outer case 7. Thereby, the lithium ion secondary battery 1 is obtained.

FIG. 3 is a plan view schematically showing a configuration of a main part (electrode group 15a) of the lithium ion secondary battery 15 according to the second embodiment of the present invention. FIG. 3 is a plan view of the electrode group 15a placed on a horizontal plane so that the positive electrode 16 side is in contact with the horizontal plane and viewed from above in the vertical direction of the horizontal plane. The lithium ion secondary battery 15 is similar to the lithium ion secondary battery 1, and illustration and description of corresponding portions are omitted. The lithium ion secondary battery 15 has the same configuration as the lithium ion secondary battery 1 except that it includes an electrode group 15 a instead of the electrode group 2.
The electrode group 15a is a flat electrode group in which a positive electrode 16, a separator (not shown), and a negative electrode 17 are stacked.

The positive electrode 16 includes a positive electrode current collector 18 and a positive electrode active material layer (not shown).
The positive electrode current collector 18 includes a current collector body 18a, a heat radiating portion 18b, and a lead portion 18c. The current collector body 18a has a configuration similar to that of the current collector body 10a and has a substantially rectangular shape. The heat radiating part 18b is provided so as to be continuous with the current collector body 18a and substantially parallel to the surface of the electrode group 15a in the thickness direction. The heat dissipating part 18b has the same configuration as the heat dissipating part 10b except that it has a U-shaped shape. The shape of the heat radiation part 18b is the shape of the surface in the thickness direction of the electrode group 15a.

  The heat radiating portion 18b extends from one side of the current collector body 18a and a part of the other two sides adjacent to each other while sharing the apex angle to the outside of the electrode group 15a and integrally. Is formed. That is, the heat radiating portion 18b is provided so as to extend outward from the electrode group 15a from the three sides of the current collector body 18a. By adopting this configuration, the heat dissipation efficiency of the heat dissipating part 18b is further higher than the heat dissipating efficiency of the heat dissipating part 10b.

  The lead portion 18c may be provided so as to be continuous with the heat radiating portion 18b and substantially parallel to the surface in the thickness direction of the electrode group 15a. The lead portion 18c has the same configuration as the lead portion 10c except that it has a U-shape. The shape of the lead portion 18c is the shape of the surface in the thickness direction of the electrode group 15a. The lead portion 18c extends from one side of the outer periphery of the heat radiating portion 18b and a part of the other two sides adjacent to each other sharing the apex angle toward the outside of the electrode group 15a and integrally. Is formed.

That is, the lead portion 18c is provided so as to extend outward from the three sides of the heat radiating portion 18b. The lead portion 18c has the same configuration as that of the lead portion 10c except for the shape. By adopting this configuration, it is possible to further improve the heat dissipation effect by the heat dissipation portion 18b.
The positive electrode active material layer has the same configuration as the positive electrode active material layer 11 in the lithium ion secondary battery 1.

The negative electrode 17 includes a negative electrode current collector 19 and a negative electrode active material layer (not shown).
The negative electrode current collector 19 includes a current collector main body 19 a, a heat radiating portion 19 b, and a lead portion 19 c, and has the same shape as the positive electrode current collector 18. The current collector main body 19a has the same configuration as the current collector main body 12a and has a substantially rectangular shape. The heat dissipating part 19b is provided so as to be continuous with the current collector main body 19a and substantially parallel to the surface of the electrode group 15a in the thickness direction. The heat dissipating part 19b has the same configuration as the heat dissipating part 12b except that it has an inverted U-shaped shape. The shape of the heat radiation part 19b is the shape of the surface in the thickness direction of the electrode group 15a.

  The heat dissipating part 19b extends from one side of the current collector main body 19a and a part of the other two adjacent sides sharing the apex angle toward the outside of the electrode group 15a and integrally. Is formed. That is, the heat radiating portion 19b is provided so as to extend outward from the three sides of the current collector main body 19a to the electrode group 15a. By adopting this configuration, the heat dissipation efficiency of the heat dissipation portion 19b is further higher than the heat dissipation efficiency of the heat dissipation portion 12b.

The lead portion 19c may be provided so as to be continuous with the heat dissipation portion 19b and substantially parallel to the surface of the electrode group 15a in the thickness direction. The lead portion 19c has an inverted U-shape and has the same configuration as the lead portion 18c. The shape of the lead portion 19c is the shape of the surface in the thickness direction of the electrode group 15a. The lead portion 19c extends from one side of the outer periphery of the heat radiating portion 19b and a part of the other two sides adjacent to each other while sharing the apex angle to the outside of the electrode group 15a and integrally. Is formed. That is, the lead portion 19c is provided so as to extend outward from the electrode group 15a from the three sides of the heat radiating portion 19b. By adopting this configuration, it is possible to further improve the heat dissipation effect by the heat dissipation portion 19b.
The negative electrode active material layer has the same configuration as the negative electrode active material layer 13 in the lithium ion secondary battery 1.

  As shown in FIG. 3, also in the lithium ion secondary battery 15, the positive electrode current collector 18 and the negative electrode current collector 19 have the intersections of the diagonal lines of the current collector main bodies 18 a and 19 a at the same position in the thickness direction. Arranged to overlap. That is, in the thickness direction, the current collector main bodies 18a and 19a are overlapped via the positive electrode active material layer, the separator, and the negative electrode active material layer. The positive electrode current collector 18 and the negative electrode current collector 19 are arranged symmetrically with respect to the intersection of the diagonal lines of the current collector main bodies 18a and 19a, and the projection surfaces of the heat radiating portions 18b and 19b overlap in the thickness direction. It is arranged not to become.

  The lithium ion secondary battery 15 includes the electrode group 15a having the heat dissipating portions 18b and 19b as described above, so that the heat dissipating efficiency is further improved and the mechanical strength is improved. It gets even higher.

FIG. 4 is a plan view schematically showing a configuration of a main part (electrode group 20a) of the lithium ion secondary battery 20 according to the third embodiment of the present invention. FIG. 4 is a plan view of the electrode group 20a placed on a horizontal plane so that the positive electrode 23 is in contact with the horizontal plane and viewed from above in the vertical direction of the horizontal plane. The lithium ion secondary battery 20 is similar to the lithium ion secondary battery 1, and illustration and description of corresponding portions are omitted. The lithium ion secondary battery 20 has the same configuration as the lithium ion secondary battery 1 except that it includes an electrode group 20 a instead of the electrode group 2.
The electrode group 20a is a flat electrode group in which a positive electrode 21, a separator (not shown), and a negative electrode 22 are stacked.

The positive electrode 21 includes a positive electrode current collector 23 and a positive electrode active material layer (not shown).
The positive electrode current collector 23 includes a current collector body 23a, a heat radiating portion 23b, and a lead portion 23c.
The current collector body 23a has the same configuration as that of the current collector body 10a and has a substantially rectangular shape.

  The heat dissipating part 23b is provided so as to be continuous with the current collector body 23a and substantially parallel to the surface of the electrode group 20a in the thickness direction. The heat dissipating part 23b has the same configuration as the heat dissipating part 10b except that the heat dissipating part 23b is formed so as to extend to the outside of the electrode group 20a independently from two opposing sides of the current collector body 23a. Here, the two sides of the current collector body 23a are one arbitrary side and a side facing the side. By adopting this configuration, the heat dissipation efficiency of the heat dissipation portion 23b is equal to or higher than the heat dissipation efficiency of the heat dissipation portion 10b.

The lead portion 23c may be provided so as to be continuous with the heat radiating portion 23a and substantially parallel to the surface in the thickness direction of the electrode group 20a. The lead portion 23b has the same configuration as the lead portion 10c except that the lead portion 23b is formed so as to extend independently from the outer periphery of the two heat dissipating portions 23b in the opposite direction outside the electrode group 20a. By adopting this configuration, it is possible to further improve the heat effect by the heat radiating portion 23b.
The positive electrode active material layer has the same configuration as the positive electrode active material layer 11 in the lithium ion secondary battery 1.

The negative electrode 22 includes a negative electrode current collector 24 and a negative electrode active material layer (not shown).
The negative electrode current collector 24 includes a current collector body 24 a, a heat radiating portion 24 b, and a lead portion 24 c, and has the same shape as the positive electrode current collector 23. The current collector body 24a has the same configuration as that of the current collector body 12a and has a substantially rectangular shape.

  The heat radiation part 24b is provided so as to be continuous with the current collector body 24a and substantially parallel to the surface of the electrode group 20a in the thickness direction. The heat dissipating part 24b has the same configuration as the heat dissipating part 12b except that the heat dissipating part 24b is formed to extend outward from the electrode group 20a independently from the two sides of the current collector body 24a. Here, the two sides of the current collector 24a are one arbitrary side and a side facing the side. By adopting this configuration, the heat dissipation efficiency of the heat dissipation part 24b is equal to or higher than the heat dissipation efficiency of the heat dissipation part 12b.

The lead portion 24c may be provided so as to be continuous with the heat radiating portion 24a and substantially parallel to the surface in the thickness direction of the electrode group 20a. The lead portion 24b has the same configuration as the lead portion 10c except that the lead portion 24b is formed so as to extend independently from the outer periphery of the two heat radiating portions 24b in the opposite direction to the outside of the electrode group 20a. By adopting this configuration, it is possible to further improve the heat effect by the heat radiating portion 24b.
The negative electrode active material layer has the same configuration as the negative electrode active material layer 13 in the lithium ion secondary battery 1.

  As shown in FIG. 4, also in the lithium ion secondary battery 20, the positive electrode current collector 23 and the negative electrode current collector 24 have the intersections of the diagonal lines of the current collector main bodies 23 a and 24 a at the same position in the thickness direction. Arranged to overlap. That is, in the thickness direction, the current collector main bodies 23a and 24a overlap with each other via the positive electrode active material layer, the separator, and the negative electrode active material layer. Further, the positive electrode current collector 23 and the negative electrode current collector 24 are symmetrically arranged around the intersection of the diagonal lines of the current collector main bodies 23a and 24a, and the projection surfaces of the heat radiating portions 23b and 24b overlap in the thickness direction. It is arranged not to become.

  When the lithium ion secondary battery 20 includes the electrode group 20a having the heat dissipation portions 23b and 23b as described above, the heat dissipation efficiency is further improved, and the mechanical strength and the durability are improved.

  The lithium ion secondary battery of the present invention can be used in the same applications as conventional lithium ion secondary batteries, and in particular, personal computers, mobile phones, mobile devices, personal digital assistants (PDAs), portable game devices, and video cameras. It is useful as a power source for portable electronic devices such as In addition, it is expected to be used as a secondary battery for assisting an electric motor, a power tool, a cleaner, a power source for driving a robot, a power source for a plug-in HEV, etc. in a hybrid electric vehicle, a fuel cell vehicle and the like.

It is a longitudinal cross-sectional view which shows typically the structure of the lithium ion secondary battery which is 1st Embodiment of this invention. It is a top view which shows typically the structure of the principal part of the lithium ion secondary battery shown in FIG. It is a top view which shows typically the structure of the principal part of the lithium ion secondary battery which is the 2nd Embodiment of this invention. It is a top view which shows typically the structure of the principal part of the lithium ion secondary battery which is 3rd Embodiment of this invention.

Explanation of symbols

1, 15, 20 Lithium ion secondary battery 2, 15a, 20a Electrode group 3, 16, 21 Positive electrode 4, 17, 22, 26 Negative electrode 5 Separator
6 Gasket
7 Outer case 10, 18, 23 Positive electrode current collector 10a, 18a, 23a Positive electrode current collector body 10b, 18b, 23b Positive electrode heat radiation part 10c, 18c, 23c Positive electrode lead part 11 Positive electrode active material layer 12, 17, 24 Negative electrode current collection Electric current bodies 12a, 19a, 24a Negative electrode current collector bodies 12b, 19b, 24b Negative electrode heat radiation portions 12c, 19c, 24c Negative electrode lead portions 13 Negative electrode active material layers

Claims (3)

A lithium ion secondary battery comprising: a flat electrode group formed by laminating a positive electrode, a separator, and a negative electrode in a thickness direction; a nonaqueous electrolyte; and a battery case containing the flat electrode group and the nonaqueous electrolyte. There,
Each of the positive electrode and the negative electrode has a rectangular current collector body present in the flat electrode group, and an active material layer capable of inserting and extracting lithium supported on the surface of the current collector body, Including
And the current collector along two sides sandwiching one corner of the body out collision extends like a hook to the outside of the plate-like electrode group, the current collector body and seamlessly heat radiating portion which is one embodied,
A lead portion integrated or connected to at least one of the heat radiating portions, the end portion of which is led out of the battery case ; and
The projection surface of the heat dissipation portion of the positive electrode and the projection surface of the heat dissipation portion of the negative electrode do not overlap,
The ratio (S / S ₀ ) between the area S _{0 of the} current collector body and the area S of the heat radiating portion is 0.03 to 1.5,
The previous SL periphery length L ₀ of the collector body, before Symbol ratio of the length L of the boundary line between the current collector body before Symbol respective discharge heat unit (L / L ₀₎ is 0.25 This is the lithium ion secondary battery. A lithium ion secondary battery comprising: a flat electrode group formed by laminating a positive electrode, a separator, and a negative electrode in a thickness direction; a nonaqueous electrolyte; and a battery case containing the flat electrode group and the nonaqueous electrolyte. There,
Each of the positive electrode and the negative electrode has a rectangular current collector body present in the flat electrode group, and an active material layer capable of inserting and extracting lithium supported on the surface of the current collector body, Including
A heat radiating part extending in a U-shape and projecting outward from the plate-like electrode group along the three sides of the current collector body, and being integrated seamlessly with the current collector body,
A lead portion integrated or connected to at least one of the heat radiating portions, the end portion of which is led out of the battery case; and
The projection surface of the heat dissipation portion of the positive electrode and the projection surface of the heat dissipation portion of the negative electrode do not overlap,
Area S of current collector body ₀ To the area S of the heat radiating portion (S / S ₀ ) Is 0.03 to 1.5,
Perimeter length L of each current collector body ₀ And the ratio (L / L) of the boundary line length L between each current collector body and each heat radiation portion ₀ ) Is a lithium ion secondary battery having 0.25 or more. A lithium ion secondary battery comprising: a flat electrode group formed by laminating a positive electrode, a separator, and a negative electrode in a thickness direction; a nonaqueous electrolyte; and a battery case containing the flat electrode group and the nonaqueous electrolyte. There,
Each of the positive electrode and the negative electrode has a rectangular current collector body present in the flat electrode group, and an active material layer capable of inserting and extracting lithium supported on the surface of the current collector body, Including
A heat dissipating part extending outwardly from the two opposite sides of the current collector body and projecting outward from the plate-like electrode group, and being seamlessly integrated with the current collector body;
A lead portion integrated or connected to at least one of the heat radiating portions, the end portion of which is led out of the battery case; and
The projection surface of the heat dissipation portion of the positive electrode and the projection surface of the heat dissipation portion of the negative electrode do not overlap,
The ratio (S / S ₀ ) between the area S _{0 of the} current collector body and the area S of the heat radiating portion is 0.03 to 1.5,
Lithium having a ratio (L / L ₀ ) between the outer peripheral length L ₀ of each current collector body and the length L of the boundary line between each current collector body and each heat radiating portion is 0.25 or more Ion secondary battery .

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