JP2012190738A - Lithium secondary battery - Google Patents

Abstract

Provided is a lithium secondary battery capable of preventing a winding deviation of a wound body that occurs during the manufacture of the wound body or later.
The length of the portion where the positive electrode 52 and the positive electrode tab terminal 20 are electrically connected is shorter than the width of the positive electrode 52, and the longitudinal direction of the positive electrode tab terminal 20 and the longitudinal direction of the positive electrode 52 are set to be vertical. To do. In addition, the length of the portion where the negative electrode 56 and the negative electrode tab terminal 24 are electrically connected is shorter than the width of the negative electrode 56, and the longitudinal direction of the negative electrode tab terminal 24 and the longitudinal direction of the negative electrode 56 are set to be vertical. The insulating member 30 of the positive electrode 52 protrudes from the case bottom end 60 of the positive electrode, and the insulating member 31 of the negative electrode 56 protrudes from the case bottom end 64 of the negative electrode.
[Selection] Figure 1

Description

  The present invention relates to a lithium secondary battery.

  With the spread of various portable devices such as notebook personal computers in recent years, the demand for secondary batteries as power sources is increasing. Further, in response to demands such as long-time driving of portable devices and improvement of portability, improvement of energy density and safety of secondary batteries are required.

  Among secondary batteries, in particular, lithium secondary batteries have been widely used as power sources for portable devices. This is because the energy density of the lithium secondary battery is high. Taking advantage of these characteristics, lithium secondary batteries are being developed as power sources for large-capacity power storage systems.

  In a lithium secondary battery for portable equipment, a laminated aluminum foil container is widely used as a container for storing a wound body in which a positive electrode and a negative electrode are wound. In addition, flat rectangular containers made of metal, cylindrical containers made of metal, and the like are also widely used. Lithium secondary batteries for large-capacity power storage system power supplies contain a wound body with the positive electrode and negative electrode wound in consideration of the length of use period, harsh usage environment, and storage capacity. As the container, it is effective to use a metal cylindrical container.

  As disclosed in Non-Patent Document 1, a currently popular lithium secondary battery includes a bottomed container body and a sealing body for closing an opening of the container body. Since the sealing body also serves as a safety device, it has a complicated structure.

  Lithium secondary batteries for large-capacity power storage system power supplies are required to have higher safety than high energy density. In other words, by optimizing the material and design of the electrode, lithium secondary batteries having high safety are being developed even if the energy density is not as high as that for portable devices.

  Patent Document 1 discloses that a sealing body widely used in an electrolytic capacitor is applied to a lithium secondary battery as a new lithium secondary battery structure. By adopting the same sealing body as the electrolytic capacitor in the lithium secondary battery, the sealing body itself has a simple structure as compared with the sealing body of the lithium secondary battery having a conventional complicated structure. be able to.

  Further, in Patent Document 2, in order to prevent a short circuit at the bottom of the container in the electrolytic capacitor, the length of the tab terminal is made longer than the width of the electrode, and the tab terminal protruding from the bottom side end of the capacitor element is disclosed. A structure in which an insulating material is fixedly arranged at the tip is disclosed.

JP-A-10-308206 Microfilm of Japanese Patent Application No. Sho 62-1222044 (Japanese Patent Application No. 64-26825)

Yoshiyuki Masao and Akiya Ozawa, “Lithium-ion Secondary Batteries-Materials and Applications”, 2nd edition, Nikkan Kogyo Shimbun, January 27, 2001, p. 175-176

  The tab terminal for an electrolytic capacitor disclosed in Patent Document 1 has a flat portion that is partly processed into a flat shape. The length of the flat portion of the tab terminal is shorter than the width of the electrode. The flat portion of the tab terminal is joined on the electrode by welding or the like.

  However, since the length of the flat portion of the tab terminal is shorter than the width of the electrode, the thickness in the width direction of the electrode is not uniform at the portion where the flat portion of the tab terminal is welded. Therefore, when a wound body is created by winding an electrode welded with a tab terminal, the wound body is likely to be deformed in the axial direction due to non-uniform thickness, so that a so-called slippage is likely to occur. Had problems. In particular, the influence is remarkable in the electrode of the lithium secondary battery which is thicker than the electrode of the capacitor and inferior in flexibility.

  Moreover, in the thin part where the flat part of the tab terminal is not welded, the tightening pressure for winding is weakened, so that the tightening pressure for the entire wound body is reduced. Thereby, when using the battery after manufacture, there was a problem that the wound body is likely to cause a subsequent wrinkle due to external vibration or impact. In this case as well, a lithium secondary battery electrode having a larger mass than the capacitor electrode is more likely to cause such a trouble.

  Moreover, in the structure currently disclosed by patent document 2, the insulating material is arrange | positioned so that the front-end | tip of the flat part of a tab terminal may be covered. In the portion where the flat portion of the tab terminal is welded, the thickness in the width direction of the electrode is not uniform. When the flat portion of the tab terminal is prevented from protruding from the electrode, an insulating material is also poured into the electrode group to constitute a wound body. As a result, both the winding body and the subsequent use of the battery are liable to cause the winding body to slip.

  The present invention solves the conventional problems, and can be used to prevent winding of the wound body when the wound body is wound by using an electrode welded with a tab terminal, and to use a battery. It is an object of the present invention to provide a lithium secondary battery that can prevent a subsequent winding deviation from occurring in a wound body due to vibration or impact at the time.

  In order to solve the above problems, a lithium secondary battery of the present invention includes a positive electrode including a positive electrode active material layer capable of releasing and occluding lithium ions and a positive electrode current collector, and a negative electrode capable of releasing and occluding lithium ions. A negative electrode including an active material layer and a negative electrode current collector, a separator, a wound body in which the positive electrode and the negative electrode are wound through the separator, and a case having a bottom portion that accommodates the wound body; A lithium secondary battery having a sealing body that seals the case in which the winding body is accommodated on the opposite side of the bottom portion, and the winding body is further disposed near the sealing body side end of the positive electrode A positive electrode tab terminal electrically connected to the positive electrode, and a flexibility provided in the extending direction of the case bottom side end portion of the positive electrode tab terminal and having a cross-sectional shape substantially equal to the cross-sectional shape of the flat portion of the positive electrode tab terminal The positive electrode insulation member and the negative electrode sealing body side end portion A negative electrode tab terminal electrically connected to the negative electrode, and a flexible tab having a cross-sectional shape substantially equal to the cross-sectional shape of the flat portion of the negative electrode tab terminal, provided in the extending direction of the case bottom side end of the negative electrode tab terminal The length of the portion where the positive electrode and the positive electrode tab terminal are electrically connected is shorter than the width of the positive electrode, and the longitudinal direction of the positive electrode tab terminal and the longitudinal direction of the positive electrode are perpendicular to each other. The length of the portion where the negative electrode and the negative electrode tab terminal are electrically connected is shorter than the width of the negative electrode, and the longitudinal direction of the negative electrode tab terminal and the longitudinal direction of the negative electrode are perpendicular to each other. Is protruded from the case bottom side end of the positive electrode, and the negative insulating member has a structure protruding from the case bottom side end of the negative electrode.

  According to this configuration, it is possible to prevent the winding body from being twisted when the wound body is created. Further, it is possible to prevent the winding body from being subsequently displaced due to vibration or impact when using the battery.

  According to the lithium secondary battery of the present invention, the tab terminal is present near the end of the electrode on the side of the sealing body, and there is no tab terminal near the bottom of the metal case of the electrode. Near the bottom end of the metal case of the electrode, there is a flexible insulating member having a cross section substantially equal to the tab terminal. Due to the presence of the insulating member, the thickness of the electrode becomes uniform in the width direction. Therefore, when creating a wound body, it can prevent that a winding slip arises in a wound body. Further, it is possible to prevent the winding body from being subsequently displaced due to vibration or impact when using the battery.

(A) Cross section of lithium secondary battery in Embodiment 1 of this invention, (b) Perspective view of winding body (The figure which expanded and displayed the winding body) The figure which expanded and displayed the positive electrode and separator of the lithium secondary battery in Embodiment 1 of this invention The figure which expanded and displayed the negative electrode and separator of the lithium secondary battery in Embodiment 1 of this invention The side view of the insulating member in Embodiment 1 of this invention The front view of the insulating member in Embodiment 1 of this invention Sectional drawing of the ZZ arrow of the flat part of the positive electrode tab terminal in Embodiment 1 of this invention Sectional drawing of the insulating member of the positive electrode in Embodiment 1 of this invention of the YY arrow view Sectional drawing of the insulating member of the positive electrode in Embodiment 1 of this invention of the YY arrow view Sectional drawing of the ZZ arrow of the flat part of the negative electrode tab terminal in Embodiment 1 of this invention Sectional drawing of YY arrow of the insulating member of the negative electrode in Embodiment 1 of this invention Sectional drawing of YY arrow of the insulating member of the negative electrode in Embodiment 1 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention Side view of insulating member in Embodiment 2 of the present invention The front view of the insulating member in Embodiment 2 of this invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these.

(Embodiment 1)
The lithium secondary battery 10 in Embodiment 1 of this invention is equipped with the metal case 12, the winding body 14, and the sealing body 16 as shown to Fig.1 (a).

  As shown in FIG. 1B, the wound body 14 includes a positive electrode 52, a separator 36, and a negative electrode 56. The positive electrode 52, the separator 36, the negative electrode 56, and the separator 36 are wound in a stacked state. The wound body 14 has a cylindrical shape.

  As shown in FIG. 2A, the positive electrode tab terminal 20 has a lead-out portion 39 of the positive electrode tab terminal, a round bar portion 41 of the positive electrode tab terminal, and a flat portion 40 of the positive electrode tab terminal. As illustrated in FIG. 1B, the round bar portion 41 of the positive electrode tab terminal protrudes from the wound body 14. On the round bar portion 41 of the positive electrode tab terminal, there is a lead-out portion 39 of the positive electrode tab terminal.

  Similarly, as shown in FIG. 2B, the negative electrode tab terminal 24 includes a negative electrode tab terminal lead-out portion 53, a negative electrode tab terminal round bar portion 55, and a negative electrode tab terminal flat portion 54. As shown in FIG. 1B, the round bar portion 55 of the negative electrode tab terminal protrudes from the wound body 14. On the round bar portion 55 of the negative electrode tab terminal, there is a lead-out portion 53 of the negative electrode tab terminal.

The positive electrode 52 includes a positive electrode current collector 32 and a positive electrode active material layer 38. As shown in FIG. 2A, the positive electrode current collector 32 is provided on the separator 36. A positive electrode active material layer 38 is formed on the positive electrode current collector 32. However, there is a portion P ₂ that does not form a positive electrode active material layer on the positive electrode current collector. The width of the positive electrode 52, the width of the positive electrode current collector 32, and the width of the positive electrode active material layer 38 are the same. The flat portion 40 of the positive electrode tab terminal is fixed by welding or the like to a site P ₂ that does not form a positive electrode active material layer on the positive electrode current collector. Thereby, the positive electrode 52 and the positive electrode tab terminal 20 are electrically connected.

The length L ₂ of the portion positive electrode and the positive electrode tab terminal is electrically connected is shorter than the width L ₄ of the positive electrode. Width _{L 4} of the positive electrode is shorter than the width _{L 6} of the separator.

  Further, a positive insulating member 30 having a cross-sectional shape substantially equal to the flat portion 40 of the positive electrode tab terminal is provided in the extending direction of the metal case bottom side end portion of the flat portion 40 of the positive electrode tab terminal. For example, as for the cross-sectional shape of the flat part 40 of a positive electrode tab terminal, as shown to Fig.4 (a), a rectangular shape is mentioned. The cross-sectional shape of the flat portion 40 of the positive electrode tab terminal may be a square shape, a trapezoidal shape, a semicircular shape, or the like. Similarly, as shown in FIG. 4B, the cross-sectional shape of the positive electrode insulating member 30 may be a rectangular shape. The cross-sectional shape of the positive electrode insulating member 30 may be a square shape, a trapezoidal shape, a semicircular shape, or the like.

  Note that the cross-sectional shape of the flat portion 40 of the positive electrode tab terminal and the cross-sectional shape of the positive electrode insulating member 30 may be substantially equal. The thickness of the positive electrode only needs to be substantially uniform in the width direction due to the presence of the positive electrode tab terminal 20 and the positive insulating member 30.

This will be described with reference to FIG. Regarding the relationship between the cross-sectional width W ₁ of the flat portion 40 of the positive electrode tab terminal and the cross-sectional width W ₂ of the positive electrode insulating member 30, the cross-sectional width W ₂ of the positive electrode insulating member 30 is from 0.8 × W _1. it may be in the range of up to 1.2 × _{W 1.} More preferably, the width W ₂ of the cross section of the positive electrode insulating member 30 is in the range of 0.9 × W ₁ to 1.1 × W ₁ .

Further, regarding the relationship between the cross-sectional height H ₁ of the flat portion 40 of the positive electrode tab terminal and the cross-sectional height H ₂ of the positive electrode insulating member 30, the cross-sectional height H ₂ of the positive electrode insulating member 30 is 0. It suffices to be within a range from 8 × H ₁ to 1.2 × H ₁ . More preferably, the height H ₂ of the cross section of the positive electrode insulating member 30 is in the range from 0.9 × H ₁ to 1.1 × H ₁ .

  The positive insulating member 30 protrudes from the metal case bottom end 60 of the positive electrode. Note that a plurality of positive electrode insulating members 30 may be connected together.

Similarly, the negative electrode 56 includes a negative electrode current collector 34 and a negative electrode active material layer 43. As shown in FIG. 2B, the negative electrode current collector 34 is provided on the separator 36. A negative electrode active material layer 43 is formed on the negative electrode current collector 34. However, there is a site P ₄ where the negative electrode active material layer is not formed on the negative electrode current collector. The width of the negative electrode 56, the width of the negative electrode current collector 34, and the width of the negative electrode active material layer 43 are the same. The flat portion 54 of the negative electrode tab terminal is fixed by welding or the like to a site P ₄ which does not form a negative electrode active material layer on an anode current collector. Thereby, the negative electrode 56 and the negative electrode tab terminal 24 are electrically connected.

The length L ₈ of the negative electrode and the negative electrode tab terminal is electrically connected portion is shorter than the width L ₁₀ of the negative electrode. Width _{L 10} of the negative electrode is shorter than the width _{L 6} of the separator.

  Moreover, the negative electrode insulating member 31 having a cross-sectional shape substantially equal to the flat portion 54 of the negative electrode tab terminal was disposed in the extending direction of the metal case bottom side end portion of the flat portion 54 of the negative electrode tab terminal. For example, as for the cross-sectional shape of the flat part 54 of a negative electrode tab terminal, as shown to Fig.5 (a), a rectangular shape is mentioned. The cross-sectional shape of the flat portion 54 of the negative electrode tab terminal may be a square shape, a trapezoidal shape, a semicircular shape, or the like. Similarly, the cross-sectional shape of the negative electrode insulating member 31 may be a rectangular shape as shown in FIG. The cross-sectional shape of the negative electrode insulating member 31 may be square, trapezoidal, semicircular, or the like.

  The cross-sectional shape of the flat portion 54 of the negative electrode tab terminal and the cross-sectional shape of the negative electrode insulating member 31 may be substantially equal. The presence of the negative electrode tab terminal 24 and the negative electrode insulating member 31 only requires that the thickness of the negative electrode be substantially uniform in the width direction.

This will be described with reference to FIG. Regard the relationship between the width W ₄ of the cross-section of width W ₃ and the negative electrode of the insulating member 31 the cross section of the flat portion 54 of the negative electrode tab terminal, the cross-sectional width W ₄ of the insulating member 31 of the negative electrode, from 0.8 × W ₃ It suffices to be within a range up to 1.2 × W ₃ . More preferably, the width W ₄ of the cross section of the negative electrode insulating member 31 is in the range of 0.9 × W ₃ to 1.1 × W ₃ .

Further, regarding the relationship between the height H ₃ of the cross section of the flat portion 54 of the negative electrode tab terminal and the height H ₄ of the cross section of the negative electrode insulating member 31, the height H ₄ of the cross section of the negative electrode insulating member 31 is 0. It suffices to be within a range from 8 × H ₃ to 1.2 × H ₃ . More preferably, the height H ₄ of the cross section of the negative electrode insulating member 31 is in the range of 0.9 × H ₃ to 1.1 × H ₃ .

  The negative insulating member 31 protrudes from the metal case bottom end 64 of the negative electrode. A plurality of negative electrode insulating members 31 may be joined together.

  Hereinafter, unless otherwise specified, the term “insulating member” applies to both the positive insulating member 30 and the negative insulating member 31. When described as an electrode, it applies to both the positive electrode 52 and the negative electrode 56. When described as a tab terminal, it applies to both the positive electrode tab terminal 20 and the negative electrode tab terminal 24.

  As shown in a side view (a1) and a front view (a2) in FIG. 3, the insulating member is a substantially rectangular parallelepiped. Note that the cross-sectional shape of the insulating member may be a square, trapezoid, semi-circular shape, or the like, as long as the cross-sectional area of the insulating member is substantially constant over the entire insulating member.

  Note that the width of the positive electrode 52 may be different from the width of the negative electrode 56. It is preferable that the negative insulating member 31 protrudes from the metal case bottom end 60 of the positive electrode, and the positive insulating member 30 protrudes from the case bottom end of the negative electrode.

  As shown in FIG. 1A, the wound body 14 further includes a positive electrode tab terminal 20, a negative electrode tab terminal 24, a positive electrode insulating member 30, and a negative electrode insulating member 31. The wound body 14 is housed in a metal case 12 and sealed with a sealing body 16.

  The sealing body 16 has two through holes 18. The positive electrode tab terminal 20 and the negative electrode tab terminal protrude outside the metal case 12 through the through hole 18.

  As described above, in the lithium secondary battery 10 according to the first embodiment, the insulating member exists in the vicinity of the metal case bottom side end portion of the electrode where the tab terminal does not exist. Due to the presence of the insulating member, the thickness of the electrode becomes substantially uniform in the width direction. Therefore, when creating the wound body 14, it is possible to prevent the winding body 14 from being twisted.

  Furthermore, the pressure which clamps the winding body 14 becomes uniform because the thickness of an electrode becomes substantially uniform in the width direction. Therefore, it is possible to prevent the winding body 14 from being subsequently displaced due to vibration or impact when using the battery.

  In addition, when pressure such as impact is applied to the bottom side of the metal case 12 when using the battery, the insulating member protrudes from the metal case bottom side end of the electrode, so the insulating member is ahead of the electrode, Under pressure. When pressure is applied, the insulating member is flexible, so that the insulating member buckles. Note that buckling refers to a phenomenon in which a long bar or column or the like bends in the lateral direction when a certain limit is exceeded when a compressive load is applied in the longitudinal direction. Even if the insulating member is buckled, it is difficult for the insulating member to break through the separator wound in a spiral with the electrode because of its flexibility.

  Further, when an extremely large pressure is applied to the bottom side of the metal case 12, the insulating member is greatly buckled. In that case, when the insulating member buckles greatly, the insulating member may break through the separator wound together with the electrode in a spiral shape. Even if the insulating member breaks through the separator, a short circuit inside the battery can be prevented because of the insulating property.

  Further, the positive insulating member 30 and the positive tab terminal 20 may or may not be joined. Preferably, the positive insulating member 30 and the positive electrode tab terminal 20 are joined and integrated. This is because the positive electrode insulating member 30 and the positive electrode tab terminal 20 can be disposed on the positive electrode 52 in one step, which is easy to manufacture. Similarly, the negative electrode insulating member 31 and the negative electrode tab terminal 24 may or may not be bonded. The negative electrode insulating member 31 and the negative electrode tab terminal 24 are preferably joined and integrated.

  As a method of joining the positive electrode insulating member 30 and the positive electrode tab terminal 20, adhesion using an adhesive and a pressure sensitive adhesive, thermal fusion using a thermoplastic resin material, positive electrode insulating member 30 and the positive electrode tab terminal 20 are used. For example, a method of forming a concavo-convex shape and fitting them. These methods can also be used as a method of joining the negative insulating member 31 and the negative electrode tab terminal 24 together.

  Alternatively, the positive insulating member 30 and the positive electrode tab terminal 20 may not be bonded, and the positive insulating member 30 may be disposed on the positive electrode 52 and bonded to the positive electrode 52. Examples of the method for fixing the positive insulating member 30 to the positive electrode 52 include adhesion with an adhesive and a pressure-sensitive adhesive, and thermal fusion using a thermoplastic resin material. These methods can also be used when the negative insulating member 31 and the negative electrode tab terminal 24 are not bonded, and the negative insulating member 31 is disposed on the negative electrode 56 and bonded to the negative electrode 56.

  Conventionally, an insulating plate has been inserted between the separator 36 and the bottom of the metal case 12. This is because, when a pressure such as an impact is applied from the bottom side of the metal case 12 when the battery is used, the electrode and the bottom of the metal case 12 come into contact with each other to prevent a short circuit from occurring.

  In the lithium secondary battery 10 of Embodiment 1, it is not necessary to insert an insulating plate between the separator 36 and the bottom of the metal case 12. Even when a pressure such as an impact is applied from the bottom side of the metal case 12 when the battery is used, the insulating member protrudes from the metal case bottom side end portion of the electrode. 12 will come into contact with the bottom. There is no short circuit.

  Further, in the lithium secondary battery 10 of Embodiment 1, the case bottom side end portion 37 of the separator is located on the case bottom side of the case bottom side end portion of the positive electrode insulating member 30, and the case bottom side of the separator When the end 37 is positioned closer to the case bottom than the case bottom end of the negative insulating member 31, the separator 36 directly contacts the bottom of the metal case 12. The volume in the metal case 12 can be effectively utilized only by the volume of the insulating plate that has been conventionally required.

  Consider the increase in battery capacity due to the elimination of the insulating plate.

The battery capacity is determined by the length of the current collector × the width of the current collector × the capacity per unit area of the current collector. For example, a battery cell having an inner diameter of 18 (mm) and a height of 50 (mm) is assumed. The length of the current collector is about 550 (mm) and the width of the current collector is about 39 (mm). The capacity per unit area of the current collector is about 5.4 (mAh / cm ² ) in the case of double-sided coating. Accordingly, the battery capacity is about 1158 (mAh). The length of the current collector, the width of the current collector, and the capacity per unit area of the current collector are examples. By changing the design of the battery structure, the length of the current collector, the width of the current collector, the capacity per unit area of the current collector, and the battery capacity change.

  The increase in battery capacity due to the elimination of the insulating plate is obtained by the length of the current collector × the thickness of the insulating plate × the capacity per unit area of the current collector. This is because the width of the current collector can be increased by an amount corresponding to the thickness of the insulating plate. For example, it is assumed that the thickness of the insulating plate is about 0.5 (mm). At this time, the increase in battery capacity due to the elimination of the insulating plate is about 14.9 (mAh). Accordingly, the battery capacity is improved by about 1.3 (%).

  Next, each component will be described in detail.

(Metal case)
The metal case 12 is a metal case having a bottom and an opening. The material of the metal case 12 is preferably a metal such as aluminum or aluminum alloy from the viewpoint of lightness and workability. More preferred is an aluminum alloy to which a small amount of elements such as Si, Fe, Cu, Mn, Mg, Zn, Ti, Ga, and V are added. This is because the strength of the aluminum alloy is improved.

(Sealed body)
The sealing body 16 is made of an elastic material such as an elastic material (elastomer) having rubber elasticity, and has a cylindrical shape. The diameter of the sealing body 16 is slightly larger than the diameter of the opening of the metal case 12. As a material of the sealing body 16, ethylene propylene diene rubber (EPDM), isobutylene isoprene rubber (IIR), butadiene styrene rubber (SBR), or the like can be used.

(Positive electrode)
The positive electrode 52 includes a positive electrode current collector 32 and a positive electrode active material layer 38 provided on one or both surfaces of the positive electrode current collector 32.

  The positive electrode current collector 32 is a sheet-like member having conductivity. Metal foil can be used. In place of the metal foil, a member having a large number of holes (metal mesh, punching metal, expanded metal) can also be used. The material of the positive electrode current collector 32 is preferably a metal. For example, aluminum and aluminum alloy are suitable.

  The positive electrode active material layer 38 includes a positive electrode active material, a binder, and a conductive additive.

An oxide can be used as the positive electrode active material. Examples of the oxide include manganese dioxide (MnO ₂ ), lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg, Li _x NiO ₂ ), and lithium cobalt composite oxide. (e.g. Li _x CoO _2), lithium nickel cobalt composite oxide (e.g., _{LiNi 1-y Co y O 2} ), and lithium-manganese-cobalt composite oxide (e.g., _{Li x Mn y Co 1-y} O 2) and the like. Examples of other oxides include spinel type lithium manganese nickel composite oxide (Li _x Mn _{2 -y} Ni _y O ₄ ), lithium phosphorus oxide having an olivine structure (Li _x FePO ₄ ), and the like. Each of “x” and “y” in the above chemical formula can take a value in the range of 0 to 1. Preferred oxides include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, spinel type lithium manganese nickel composite oxide, lithium manganese cobalt composite oxide, and lithium iron phosphate. Is mentioned. These materials have a charge / discharge potential of 3.0 (V) or more and 5.0 (V) or less with respect to the potential of metallic lithium.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), ethylene propylene rubber, ethylene propylene diene rubber, fluoro rubber, styrene butadiene rubber (SBR), and the like.

  A carbon material can be used as the conductive assistant. As the carbon material, carbon materials such as acetylene black, carbon black, and graphite can be used.

(Negative electrode)
The negative electrode 56 includes a negative electrode current collector 34 and a negative electrode active material layer 43 provided on one surface or both surfaces of the negative electrode current collector 34.

  The negative electrode current collector 34 is also a conductive sheet-like member. Metal foil can be used. Instead of the metal foil, a member having a large number of holes (metal mesh, punching metal, expanded metal) can also be used. The material of the negative electrode current collector 34 is preferably a metal. For example, nickel, nickel alloy, copper, copper alloy, aluminum, aluminum alloy and the like are suitable.

  The negative electrode active material layer includes a negative electrode active material, a binder, and a conductive additive.

Examples of the negative electrode active material include lithium metal, lithium alloy, lithium titanium composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), a carbon material that can occlude and release lithium ions, and a material that can form an alloy with lithium (so-called alloy-based active material). Substance). An example of the carbon material is graphite. Examples of the alloy-based active material include tin, tin alloy, silicon, and silicon alloy. From the viewpoint of charge / discharge efficiency and cycle life, a carbon material or a lithium titanium composite oxide is preferable.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), ethylene propylene rubber, ethylene propylene diene rubber, fluoro rubber, styrene butadiene rubber (SBR), and the like.

  A carbon material can be used as the conductive assistant. As the carbon material, carbon materials such as acetylene black, carbon black, and graphite can be used.

  When the negative electrode active material layer 43 includes a negative electrode active material having a noble potential of 1.0 (V) or more with respect to the potential of metallic lithium, the negative electrode current collector 34 is preferably made of aluminum or an aluminum alloy. This is because the weight of the current collector can be reduced by using aluminum or aluminum alloy having a small specific gravity. Further, it is possible to prevent the negative electrode current collector 34 made of aluminum or an aluminum alloy from being eluted.

As a negative electrode active material having a noble potential of 1.0 (V) or more with respect to the potential of metallic lithium, a composite oxide containing lithium and titanium can be given. Specifically, lithium titanate represented by the chemical formula Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) and having a spinel structure can be given.

(Separator)
As the separator 36, a porous film, a nonwoven fabric, or the like can be used. Examples of the porous film include those made of polyethylene or polypropylene. As a nonwoven fabric, what consists of a cellulose or polyvinyl alcohol (PVA) is mentioned.

(Nonaqueous electrolyte)
The nonaqueous electrolytic solution is injected into the metal case 12. The nonaqueous electrolytic solution contains an organic solvent and an electrolyte.

  Examples of the organic solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC). Also, chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC), cyclic ethers such as tetrahydrofuran (THF) and 2 methyltetrahydrofuran (2MeTHF), chains such as dimethoxyethane (DME) And ether, acetonitrile (AN), sulfolane (SL) and the like. These organic solvents can be used alone or in the form of a mixture of two or more.

Examples of the electrolyte include lithium salts such as lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), and lithium tetrafluoroborate (LiBF ₄ ). From the viewpoint of chemical stability and high dielectric constant, it is preferable to use lithium hexafluorophosphate (LiPF ₆ ) as the main electrolyte. The main electrolyte means an electrolyte that is contained most in a molar ratio. The electrolyte is dissolved in the organic solvent at a concentration of 0.5 to 2.0 (mol / L), for example.

(Positive electrode tab terminal and negative electrode tab terminal)
As a material of the positive electrode tab terminal 20, a metal can be used. Examples of the metal include aluminum, an aluminum alloy, and stainless steel.

  As a material of the negative electrode tab terminal 24, a metal can be used. Examples of the metal include nickel, nickel alloy, copper, copper alloy, and stainless steel. In the case where the negative electrode includes a negative electrode active material having a noble potential of 1.0 (V) or more with respect to the potential of metallic lithium, aluminum or an aluminum alloy can also be used.

(Positive electrode insulation member and negative electrode insulation member)
The material of the positive insulating member 30 and the negative insulating member 31 may be any material having electrical insulation. For example, ceramic materials and resin materials can be used. The resin material may be any material that does not dissolve or swell with the electrolytic solution. For example, ethylene propylene diene rubber (EPDM), isobutylene isoprene rubber (IIR), butadiene styrene rubber (SBR), etc. can be used. In addition, polyolefin resins such as polyethylene and polypropylene, polytetrafluoroethylene (PTFE), perfluoroalkoxy fluororesin, fluororesins including tetrafluoroethylene / hexafluoropropylene copolymer, cellulose, etc. may be used. it can. These resin materials may be used alone, or two or more kinds thereof may be mixed or laminated and used in combination. The resin material may be a high-density molded body that does not include voids, a porous body that includes voids, or a hollow structure having one or more spaces. Moreover, as a resin material, a nonwoven fabric and its laminated body may be sufficient. Further, as the resin material, a natural material may be used instead of an artificial synthetic product. For example, paper, cloth, felt and the like can be mentioned.

(Embodiment 2)
Hereinafter, the lithium secondary battery 10 of Embodiment 2 of this invention is demonstrated, referring drawings. The lithium secondary battery of Embodiment 2 is different from the lithium secondary battery of Embodiment 1 in the shape of the insulating member. The other parts are the same.

  The shape of the insulating member will be described. The insulating member is provided with a portion where the cross-sectional area of the insulating member in the direction perpendicular to the longitudinal direction of the insulating member is smaller than the cross-sectional area of other portions of the insulating member at a predetermined position. This is because when pressure is applied to the insulating member, the pressure concentrates on the portion, and the insulating member is more likely to buckle. Moreover, there is an advantage that the material of the insulating member can be saved by providing the insulating member with a portion smaller than the cross-sectional area of the other portion of the insulating member at a predetermined position. Examples are given below.

  As shown in a side view (a1) and a front view (a2) in FIG. 6, a trapezoidal notch is provided at a predetermined position in a direction perpendicular to the longitudinal direction of the insulating member.

  As shown in a side view (b1) and a front view (b2) in FIG. 6, a large trapezoidal notch is provided at a predetermined position in a direction perpendicular to the longitudinal direction of the insulating member.

  As shown in a side view (c1) and a front view (c2) in FIG. 6, it is possible to provide a triangular cutout at a predetermined position in a direction perpendicular to the longitudinal direction of the insulating member.

  As shown in a side view (d1) and a front view (d2) in FIG. 6, a semicircular cutout is provided at a predetermined position in a direction perpendicular to the longitudinal direction of the insulating member.

  As shown in a side view (e1) and a front view (e2) in FIG. 6, a plurality of trapezoidal cutouts are provided at predetermined positions in a direction perpendicular to the longitudinal direction of the insulating member on both side surfaces of the insulating member. Is mentioned.

  As shown in a side view (f1) and a front view (f2) in FIG. 6, a plurality of trapezoidal cutouts are provided at predetermined positions in a direction perpendicular to the longitudinal direction of the insulating member on one side surface of the insulating member. Is mentioned.

  As shown in a side view (a1) and a front view (a2) in FIG. 7, it is possible to provide a rectangular cutout at a predetermined position in a direction perpendicular to the longitudinal direction of the insulating member.

  As shown in a side view (b1) and a front view (b2) in FIG. 7, it is possible to provide a plurality of rectangular cutouts at predetermined positions in a direction perpendicular to the longitudinal direction of the insulating member.

  As shown in a side view (a1) and a front view (a2) in FIG. 8, holes may be provided at predetermined positions of the insulating member.

  As shown in a side view (b1) and a front view (b2) in FIG. 8, a plurality of holes may be provided at predetermined positions of the insulating member.

  The present invention is useful as a lithium secondary battery for a power storage system power supply. For example, the present invention is applicable to lithium secondary batteries for general household use and electric vehicles.

DESCRIPTION OF SYMBOLS 10 Lithium secondary battery 12 Metal case 14 Winding body 16 Sealing body 18 Through-hole 20 Positive electrode tab terminal 24 Negative electrode tab terminal 30 Positive electrode insulating member 31 Negative electrode insulating member 32 Positive electrode current collector 34 Negative electrode current collector 36 Separator 37 Separator case bottom side end 38 Positive electrode active material layer 39 Positive electrode tab terminal lead portion 40 Positive tab terminal flat portion 41 Positive tab terminal round bar portion 43 Negative electrode active material layer 52 Positive electrode 53 Negative electrode tab lead portion 54 forming a positive electrode active material layer on the flat portion 55 negative electrode tab round bar portion 56 negative 60 positive the metal case bottom end 64 negative electrode metal case bottom end P ₂ positive electrode collector on the terminal of the negative electrode tab terminal not sites P ₄ anode current collector portion L ₂ positive electrode that does not form a negative electrode active material layer on the positive electrode tab terminal is electrically connected portion length L ₄ positive width L ₆ separator Data width L ₈ negative electrode of the negative electrode tab terminal is electrically connected to portions of the length L ₁₀ negative electrode width

Claims (5)

A positive electrode including a positive electrode active material layer capable of releasing and storing lithium ions and a positive electrode current collector, a negative electrode including a negative electrode active material layer capable of releasing and storing lithium ions and a negative electrode current collector, and a separator. And a wound body in which the positive electrode and the negative electrode are wound through the separator,
A case having a bottom for accommodating the wound body;
A lithium secondary battery having a sealing body that seals the case in which the wound body is accommodated on the opposite side of the bottom portion;
The winding body is further disposed near the sealing body side end of the positive electrode, and a positive electrode tab terminal electrically connected to the positive electrode;
A flexible positive electrode insulating member provided in the extending direction of the case bottom side end of the positive electrode tab terminal and having a cross-sectional shape equal to the cross-sectional shape of the flat portion of the positive electrode tab terminal;
A negative electrode tab terminal disposed near the end of the negative electrode on the sealing body side and electrically connected to the negative electrode;
A flexible negative electrode insulating member provided in the extending direction of the case bottom side end of the negative electrode tab terminal and having a cross-sectional shape equal to the cross-sectional shape of the flat part of the negative electrode tab terminal;
The length of the portion where the positive electrode and the positive electrode tab terminal are electrically connected is shorter than the width of the positive electrode, and the longitudinal direction of the positive electrode tab terminal and the longitudinal direction of the positive electrode are perpendicular to each other,
The length of the portion where the negative electrode and the negative electrode tab terminal are electrically connected is shorter than the width of the negative electrode, and the longitudinal direction of the negative electrode tab terminal and the longitudinal direction of the negative electrode are perpendicular to each other,
The positive insulating member protrudes from the case bottom side end of the positive electrode,
The negative electrode insulating member is a lithium secondary battery protruding from a case bottom side end of the negative electrode. The lithium secondary battery according to claim 1, wherein the negative electrode insulating member protrudes from a case bottom side end portion of the positive electrode, and the positive electrode insulating member protrudes from a case bottom side end portion of the negative electrode. A case bottom side end of the separator is located on a case bottom side of a case bottom side end of the positive electrode insulating member, and a case bottom side end of the separator is a case bottom side of the negative electrode insulating member. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is located closer to the case bottom than the end. 4. The lithium secondary battery according to claim 1, wherein at least one of the positive electrode insulating member and the negative electrode insulating member is formed of a flexible resin material. 5. 5. The lithium secondary battery according to claim 1, wherein a cross-sectional area of a predetermined portion of the positive electrode insulating member or the negative electrode insulating member is smaller than a cross-sectional area of another portion.

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