JP4984551B2 - battery - Google Patents

Description

The present invention accommodates the wound body with a flat winding structure inside the battery can of the rectangular parallelepiped shape, directed to suitable batteries to the so-called square battery.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, or a notebook computer have appeared, and their size and weight have been reduced. Batteries used as portable power sources for these electronic devices, particularly secondary batteries, are actively used as key devices for research and development aimed at improving energy density. Among them, non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries) can provide a larger energy density than conventional lead batteries and nickel cadmium batteries, which are conventional aqueous electrolyte secondary batteries. Considerations are being made in various directions.

  Lithium ion secondary batteries have been developed in various shapes. For example, a positive electrode and a negative electrode are stacked with a separator between them and wound in a spiral shape, and a metal or resin is wound around the winding center. There is one in which a cylindrical center pin made of a material is inserted (for example, see Patent Document 1 and Patent Document 2).

FIG. 14 shows an example of a conventional center pin. The center pin has a cut 131 in the axial direction of a cylindrical tubular body 130 made of, for example, metal. When an external force is applied to the battery, the main body 130 is crushed, and as a result, the edge of the cut 131 opens to the outside, and the opened portion penetrates the separator to short-circuit between the positive electrode and the negative electrode. As a result, the battery reaction is prevented and the power generation function is safely lost.
Japanese Patent Laid-Open No. 4-332481 JP-A-11-204140 JP 2001-229905 A

  However, a so-called rectangular battery using a rectangular battery can uses a battery element that is formed into a flat shape after the positive electrode and the negative electrode are wound in a spiral shape, and the winding of such a flat battery element is used. It was difficult to insert the above-described conventional cylindrical center pin at the center of rotation. In particular, since a large square battery has a large amount of heat generation, there has been a demand for a structure capable of ensuring sufficient safety even when there is no center pin when crushed by an external force.

  Incidentally, in Patent Document 3, a perforated plate made of a metal such as stainless steel is disposed between the closed end surface of the battery can and the bottom surface of the battery element, and gas passage holes are formed at the center and outer periphery of the perforated plate. It is described that the gas is led to the safety valve side by providing.

The present invention has been made in view of the above problems, and an object, if it is crushed to external forces, it is possible to short-circuit the more reliably electrodes, to provide improved batteries safety It is in.

  A battery according to the present invention includes a rectangular parallelepiped battery can, a positive electrode having a positive electrode active material layer on the surface of a strip-shaped positive electrode current collector, and a negative electrode having a negative electrode active material layer on the surface of a strip-shaped negative electrode current collector. The winding body has a flat structure with a laminated structure between the separators, and has a wound body housed in a battery can, a cut made of a conductive material and a bent shape, And a center plate arranged at the winding center.

In accordance with batteries present invention, the center of the spirally wound body, since the conductive central plate having a notch bent shape is provided, when force is applied to the battery from the outside, the battery can is deformed Then, the center plate is pressed against the wound body, the corners of the cuts stick into the wound body, and the positive electrode and the negative electrode are reliably short-circuited by penetrating the separator.

  In particular, at this time, the positive electrode is provided with a positive electrode exposed region in which the positive electrode active material layer does not exist on both sides at the end of the positive electrode current collector on the winding center side, while the negative electrode is provided on the winding center side of the negative electrode current collector. When the negative electrode exposed region where the negative electrode active material layer does not exist on both sides is provided at the end of the electrode, the exposed region of the positive electrode current collector and the negative electrode current collector having a low resistance value are directly short-circuited Thus, no short circuit occurs through the positive electrode active material layer having a high resistance value, and the temperature rise in the positive electrode active material layer is suppressed.

According to batteries of the present invention, the center of the spirally wound body. Thus providing the conductive central plate having a notch of bent shape, when or broken crushed by an external force Thus, the positive electrode and the negative electrode can be reliably short-circuited, and safety is improved. In particular, it is suitable for a prismatic battery in which a cylindrical center pin cannot be used, and a large battery with a large calorific value, and high safety can be obtained.

  In particular, when the negative electrode is capable of occluding and releasing electrode reactants and includes a negative electrode active material containing at least one of a metal element and a metalloid element as a constituent element, the energy density of the battery is Since a larger and higher safety is required, a higher effect can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, each component schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood, and is different from the actual size.

(One embodiment)
1 and 2 show a cross-sectional structure of a secondary battery according to an embodiment of the present invention. This secondary battery is a so-called rectangular shape, and has a flat wound body 20 inside a battery can 11 having a substantially hollow rectangular parallelepiped shape.

  The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and also has a function as a negative electrode terminal. The battery can 11 has one end closed and the other end open, and the inside of the battery can 11 is sealed by attaching an insulating plate 12 and a battery lid 13 to the open end. The insulating plate 12 is made of polypropylene or the like, and is disposed on the wound body 20 perpendicular to the winding peripheral surface. The battery lid 13 is made of, for example, the same material as the battery can 11 and has a function as a negative electrode terminal together with the battery can 11. A terminal plate 14 serving as a positive electrode terminal is disposed outside the battery lid 13. A through hole is provided near the center of the battery lid 13, and a positive electrode pin 15 electrically connected to the terminal plate 14 is inserted into the through hole. The terminal plate 14 and the battery lid 13 are electrically insulated by an insulating case 16, and the positive electrode pin 15 and the battery lid 13 are electrically insulated by a gasket 17. The insulating case 16 is made of, for example, polybutylene terephthalate. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  A cleavage valve 18 and an electrolyte injection hole 19 are provided near the periphery of the battery lid 13. The cleaving valve 18 is electrically connected to the battery lid 13 and is cleaved when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating, thereby suppressing an increase in the internal pressure. . The electrolyte injection hole 19 is closed by a sealing member 19A made of, for example, a stainless steel ball.

  The wound body 20 is formed by laminating a positive electrode 21 and a negative electrode 22 with a separator 23 therebetween, and is wound in a spiral shape, and is formed into a flat shape in accordance with the shape of the battery can 11. A positive electrode lead 24 made of aluminum (Al) or the like is connected to the positive electrode 21 of the wound body 20, and a negative electrode lead 25 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 24 is welded to the lower end of the positive electrode pin 15 to be electrically connected to the terminal plate 14, and the negative electrode lead 25 is welded to and electrically connected to the battery can 11.

  FIG. 3 shows a cross-sectional configuration of the positive electrode 21 shown in FIG. 1 before winding. This positive electrode 21 is obtained by providing a positive electrode active material layer 21B on both surfaces of a strip-shaped positive electrode current collector 21A. Specifically, it has a positive electrode covering region 21C where the positive electrode active material layer 21B exists on the outer peripheral surface side and the inner peripheral surface side of the positive electrode current collector 21A. In addition, in the positive electrode 21, the end portion on the winding center side is a positive electrode exposed region 21D, that is, a region where both surfaces of the positive electrode current collector 21A are exposed without the presence of the positive electrode active material layer 21B. .

  The positive electrode current collector 21A has, for example, a thickness of about 5 μm to 50 μm and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a positive electrode active material. A conductive material and a binder such as polyvinylidene fluoride may be included. The positive electrode material capable of inserting and extracting lithium does not contain lithium such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), or vanadium oxide (V ₂ O ₅ ). Examples thereof include metal sulfides, metal selenides, metal oxides, etc., or lithium-containing compounds containing lithium.

Among these, lithium-containing compounds are preferable because some compounds can obtain a high voltage and a high energy density. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. In particular, cobalt (Co), nickel and manganese (Mn Among these, those containing at least one of them are preferred. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x MIO ₂ or Li _y MIIPO ₄ . In the formula, MI and MII represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the battery, and are generally 0.05 ≦ x ≦ 1.10.

Specific examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni _1-z Co _z O ₂ (z <1)) or lithium manganese composite oxide (LiMn ₂ O ₄ ) having a spinel structure. Among these, a composite oxide containing nickel is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can also be obtained. Specific examples of the phosphate compound containing lithium and a transition metal element include, for example, a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-v Mn _v PO ₄ (v <1)). Can be mentioned.

  FIG. 4 shows the configuration of the negative electrode 22. The negative electrode 22 is obtained by providing a negative electrode active material layer 22B on both surfaces of a strip-shaped negative electrode current collector 22A. Specifically, the negative electrode covering region 22C where the negative electrode active material layer 22B exists on the outer peripheral surface side and the inner peripheral surface side of the negative electrode current collector 22A, and both surfaces of the negative electrode current collector 22A at the winding center side end. Both have a negative electrode exposed region 22D that is exposed without the negative electrode active material layer 22B.

  The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The thickness of the negative electrode current collector 22A is, for example, 5 μm to 50 μm.

  The negative electrode active material layer 22B includes, for example, a negative electrode active material, and may include other materials such as a conductive material and a binder as necessary. Examples of the negative electrode active material include a negative electrode material that can occlude and release lithium, which is an electrode reactant, and includes at least one of a metal element and a metalloid element as a constituent element. Use of such a negative electrode material is preferable because a high energy density can be obtained. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of the metal element or metalloid element constituting the negative electrode material include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon, germanium (Ge), tin, lead (Pb), bismuth (Bi), cadmium Examples thereof include (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), and platinum (Pt).

  Among these, the negative electrode material preferably includes a group 14 metal element or metalloid element in the long-period periodic table as a constituent element, and particularly preferably includes at least one of silicon and tin as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained. Specifically, for example, a simple substance, an alloy, or a compound of silicon, a simple substance, an alloy, or a compound of tin, or a material having one or two or more phases thereof at least in part.

  Examples of tin alloys include silicon, nickel, copper, iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), and silver as second constituent elements other than tin. (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and the thing containing at least 1 sort (s) of chromium (Cr) are mentioned. As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

  Examples of the tin compound or silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to tin or silicon.

  Among these, as this negative electrode material, tin, cobalt, and carbon are included as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the total of tin and cobalt is A CoSnC-containing material having a cobalt ratio of 30% by mass to 70% by mass is preferable. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

  This CoSnC-containing material may further contain other constituent elements as necessary. Examples of other constituent elements include silicon, iron, nickel, chromium, indium, niobium (Nb), germanium, titanium, molybdenum (Mo), aluminum (Al), phosphorus (P), gallium (Ga), or bismuth. Preferably, 2 or more types may be included. This is because the capacity or cycle characteristics can be further improved.

  This CoSnC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has a low crystallinity or an amorphous structure. In this CoSnC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a semimetal element as another constituent element. The decrease in cycle characteristics is thought to be due to the aggregation or crystallization of tin or the like, but this is because such aggregation or crystallization can be suppressed by combining carbon with other elements. .

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. In XPS, the peak of the carbon 1s orbital (C1s) appears at 284.5 eV in an energy calibrated apparatus so that the peak of the gold atom 4f orbital (Au4f) is obtained at 84.0 eV if it is graphite. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element increases, for example, when carbon is bonded to a metal element or a metalloid element, the C1s peak appears in a region lower than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained for the CoSnC-containing material appears in a region lower than 284.5 eV, at least a part of the carbon contained in the CoSnC-containing material is a metal element or a half of other constituent elements. Combined with metal elements.

  In XPS measurement, for example, the C1s peak is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In the XPS measurement, the waveform of the C1s peak is obtained as a shape including the surface contamination carbon peak and the carbon peak in the CoSnC-containing material. For example, by analyzing using a commercially available software, the surface contamination The carbon peak and the carbon peak in the CoSnC-containing material are separated. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  As the negative electrode active material, a carbon material such as natural graphite, artificial graphite, non-graphitizable carbon, or graphitizable carbon may be used. Use of a carbon material is preferable because excellent cycle characteristics can be obtained. Moreover, lithium metal is also mentioned as a negative electrode active material. The negative electrode active material may be used alone or in combination of two or more.

  The separator 23 shown in FIG. 1 is composed of a porous film made of a polyolefin-based material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. A structure in which a porous film is laminated may be used.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. For example, the electrolytic solution includes a solvent and a lithium salt that is an electrolyte salt. The solvent dissolves and dissociates the electrolyte salt. Solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4-methyl. 1,3 dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetic acid ester, butyric acid ester or propionic acid ester, etc. are used, and any one of these or a mixture of two or more are used. May be.

Examples of the lithium salt include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, or LiBr. One kind or a mixture of two or more kinds may be used.

  Further, in the present embodiment, the center plate 30 is disposed at the winding center of the wound body 20. As shown in FIG. 5, the center plate 30 is a thin strip-like plate member made of a conductive material such as stainless steel, and is provided with a number of bent cuts 31. Thereby, in this battery, when crushed by external force, the positive electrode 21 and the negative electrode 22 can be short-circuited reliably, and safety can be improved.

  In particular, when the negative electrode 22 can occlude and release the electrode reactant and includes a negative electrode active material containing at least one of a metal element and a metalloid element as a constituent element, the energy density of the battery Therefore, a higher effect can be obtained because higher safety is required.

  Note that the material and thickness of the center plate 30 normally have a predetermined strength, and on the other hand, when the battery is crushed by an external force, it is crushed or broken along with it. The thickness of the center plate 30 is preferably 0.05 mm or more and 5 mm or less, for example. If the thickness is less than 0.05 mm, the strength may be weakened, and if it is thicker than 5 mm, processing and molding become difficult. Although the dimension of the short-circuit member 30 varies depending on the dimension of the secondary battery, for example, the width is preferably about 3.0 mm and the length is preferably 2.5 cm or more and 8.0 cm or less.

  The cut 31 includes a linear first portion 31A and a linear second portion 31B extending from the end of the first portion 31A in a direction different from the first portion 31A, for example, at a right angle. That is, the cut 31 has a so-called L-shape, and has a convex portion 31C at the bent portion. The convex portion 31C is for biting into the wound body 20 when the secondary battery is crushed by an external force and penetrating the separator 23 to short-circuit the positive electrode 21 and the negative electrode 22 more reliably. In addition, the corner | angular corner of the notch 31 does not necessarily need to be a right angle, and the corner may be rounded.

  It is preferable that the length of the first portion 31A and the second portion 31B, that is, the dimension in the extending direction is such that the convex portion 31C of the cut 33 can be reliably projected. The width of the first portion 31A and the second portion 31B, that is, the dimension in the direction orthogonal to the extending direction is preferably 0.1 mm or more and 2.0 mm or less, for example. This is because a higher effect can be obtained. Note that the first portion 31A and the second portion 31B do not necessarily have the same length.

  The first portion 31A is preferably parallel to the longitudinal direction of the center plate 30, and the second portion 31B preferably extends vertically from the end of the first portion 31A. This is because productivity can be improved.

  The number or arrangement of such cuts 31 is not particularly limited. For example, the distance D between the cuts 31 is preferably 0.1 mm or more. This is because productivity can be improved.

  For example, the secondary battery can be manufactured as follows.

  First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like material. A positive electrode mixture slurry is obtained. Subsequently, the positive electrode mixture slurry is uniformly applied to the positive electrode current collector 21A using a doctor blade or a bar coater, and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like. Then, the positive electrode 21 is produced.

  Next, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. And Subsequently, the negative electrode mixture slurry is uniformly applied to the negative electrode current collector 22A using a doctor blade or a bar coater, and the solvent is dried. Then, the negative electrode mixture layer 22B is formed by compression molding using a roll press. Then, the negative electrode 22 is produced. The roll press machine may be used by heating. Moreover, you may compression-mold several times until it becomes the target physical-property value. Furthermore, you may use press machines other than a roll press machine.

  Subsequently, the positive electrode lead 24 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 25 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed therebetween, wound many times in the winding direction shown in FIGS. 3 and 4, and then formed into a flat shape to produce the wound body 20. .

  After that, a thin belt-like plate made of, for example, stainless steel is prepared as the center plate 30, a cut 31 is provided by wire cutting, and the center plate 30 is inserted into the center of the wound body 20.

  After inserting the center plate 30, the wound body 20 is accommodated in the battery can 11. Subsequently, the insulating plate 12 is disposed on the wound body 20, the negative electrode lead 25 is welded to the battery can 11, and the positive electrode lead 24 is welded to the lower end of the positive electrode pin 15. The battery lid 13 is fixed by laser welding. After that, the electrolytic solution is injected into the inside of the battery can 11 through the electrolytic solution injection hole 19 and impregnated in the separator 23, and then the electrolytic solution injection hole 19 is closed with a sealing member 19A. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. When the discharge is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution impregnated in the separator 23. And in this secondary battery, since the conductive center plate 30 having the cut 31 is arranged at the winding center of the wound body 20, when the battery can 11 is deformed by the application of external force, the center plate 30 is also crushed or broken, and the convex portion 31 </ b> C of the cut 31 bites into the wound body 20 and penetrates the separator 23, whereby the positive electrode 21 and the negative electrode 22 are more reliably short-circuited.

  Further, in this secondary battery, a positive electrode exposed region 21D where the positive electrode active material layer 21B does not exist on both sides is provided on the winding center side of the positive electrode 21, and the negative electrode active material layer on both sides also on the winding center side of the negative electrode 22 Since the negative electrode exposed region 22D in which 22B does not exist is provided, the notch 31 of the center plate 30 pierces the wound body 20 and penetrates the separator 23, so that the positive current collector 21A and the negative current collector having a relatively low resistance value 22A is short-circuited directly. That is, in the present embodiment, the positive electrode exposed region 21D of the positive electrode 21 and the negative electrode exposed region 22D of the negative electrode 22 are short-circuited by the center plate 30 and short-circuited via the positive electrode active material layer 21B having a high resistance value. The temperature rise in the positive electrode active material layer 21B is suppressed.

  As described above, in the present embodiment, since the conductive center plate 30 having the bent cut 31 is provided at the winding center of the wound body 20, the battery can 11 is deformed when an external force is applied. The convex portion 31 </ b> C of the cut 31 pierces the wound body 20, and the positive electrode 21 and the negative electrode 22 can be reliably short-circuited. In particular, it is suitable for a prismatic battery in which a cylindrical center pin cannot be used or a large battery with a large calorific value, and high safety can be obtained.

  In addition, the positive electrode 21 has a positive electrode exposed region 21D in which no positive electrode active material layer 21B is present on both sides of the wound body 20, particularly on the winding center side. Since the exposed region 22D is provided, when the cut 31 of the center plate 30 penetrates the separator 23, the positive electrode current collector 21A and the negative electrode current collector 22A having a relatively low resistance value are directly short-circuited. Therefore, the positive electrode 21 and the negative electrode 22 can be reliably short-circuited while suppressing the temperature rise of the positive electrode active material layer 21B, and safety is improved.

  In particular, when the negative electrode 22 is capable of inserting and extracting an electrode reactant and includes a negative electrode active material containing at least one of a metal element and a metalloid element as a constituent element, the battery Since the energy density is high and higher safety is required, higher effects can be obtained.

(Modification)
In the present embodiment, the case where the cuts 31 are arranged at regular intervals has been described, but the cuts 31 may be arranged at irregular intervals. In the present embodiment, the first portion 31A is parallel to the longitudinal direction of the center plate 30 and the second portion 31B is perpendicular to the first portion 31A. However, as shown in FIG. The first portion 31 </ b> A and the second portion 31 </ b> B may be disposed obliquely with respect to the longitudinal direction of the center plate 30.

  Further, in the present embodiment, the case where the second portion 31B extends from the end portion of the first portion 31A in a direction perpendicular to the first portion 31A has been described. However, as shown in FIG. You may extend in the acute angle direction from the edge part of 31 A of parts. Further, the second portion 31B extends from the end of the first portion 31A in an acute angle direction, and the first portion 31A and the second portion 31B are disposed obliquely with respect to the longitudinal direction of the center plate 30. Also good.

  In addition, the cut 31 may include a linear first portion 31A and a linear second portion 31B that intersects the first portion 31A. At this time, the second portion 31B may intersect with the first portion 31A in a cross shape as shown in FIG. 8, for example, or in a T shape as shown in FIG. May be. Further, the crossing angle between the first portion 31A and the second portion 31B is not necessarily a right angle, and may be an acute angle or an obtuse angle.

  Furthermore, the cut 31 is not necessarily limited to a straight line, and may be a shape that is rounded and bent as shown in FIG. 10, for example.

  In addition, the center pin 30 may be provided with a notch 33 that intersects the side 32 of the center plate 30 as shown in FIG. 11 in addition to the notch 31 as shown in FIG. The positive electrode 21 and the negative electrode 22 can be more reliably short-circuited by the angle formed at the intersection of the notch 33 and the side 32, as in the convex portion 31C of the notch 31, and safety can be further improved. it can. The number and arrangement of the notches 33 are not particularly limited, and the notches 33 and the notches 31 do not necessarily have to be provided at positions facing each other as shown in FIG.

  Moreover, the shape of the cut 31 used together with the notch 33 is not specifically limited, You may provide the cut 31 of the other shape demonstrated in the said modification. For example, as shown in FIG. 12, the cross-shaped cut 31 shown in FIG. 8 may be provided.

  The intersecting angle of the notch 33 with respect to the side 32 is not particularly limited, and may intersect with the side 32 obliquely.

  Furthermore, the notch 31 does not necessarily have to be a hole that penetrates the center plate 30 in the thickness direction, and as shown in FIG. 13, a part in the thickness direction is made thinner than the surrounding region without penetrating. A thin groove may be used. The same applies to the notch 33.

  Further, specific embodiments of the present invention will be described in detail.

Example 1
The secondary battery described in the above embodiment was manufactured. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1 (molar ratio), and 5 ° C. at 900 ° C. in the air. After firing for a time, lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material was obtained. Next, 91 parts by mass of this lithium / cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Subsequently, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of a positive electrode current collector 21A made of an aluminum foil having a thickness of 20 μm and dried. Then, the positive electrode active material layer 21B was formed by compression molding with a roll press machine, and the positive electrode 21 was produced. Subsequently, a positive electrode lead 24 made of aluminum was attached to one end of the positive electrode current collector 21A.

  In addition, a CoSnC-containing material was produced as a negative electrode active material. First, cobalt powder, tin powder, and carbon powder were prepared as raw materials, and cobalt powder and tin powder were alloyed to produce a cobalt-tin alloy powder. Then, carbon powder was added to the alloy powder and dry mixed. Subsequently, this mixture was synthesized using a mechanochemical reaction using a planetary ball mill to obtain a CoSnC-containing material.

  When the composition of the obtained CoSnC-containing material was analyzed, the cobalt content was 29.3 mass%, the tin content was 49.9 mass%, and the carbon content was 19.8 mass%. . The carbon content was measured by a carbon / sulfur analyzer, and the cobalt and tin contents were measured by ICP (Inductively Coupled Plasma) emission analysis. Further, when X-ray diffraction was performed on the obtained CoSnC-containing material, a diffraction peak having a wide half-width with a diffraction angle 2θ of 1.0 ° or more was observed between diffraction angles 2θ = 20 ° to 50 °. It was. Further, when XPS was performed on the CoSnC-containing material, the C1s peak in the CoSnC-containing material was obtained in a region lower than 284.5 eV. That is, it was confirmed that carbon in the CoSnC-containing material was bonded to other elements.

  Next, 60 parts by mass of this CoSnC-containing material, 28 parts by mass of artificial graphite as a conductive agent and a negative electrode active material and 2 parts by mass of carbon black, and 10 parts by mass of polyvinylidene fluoride as a binder are mixed. The agent was adjusted. Subsequently, the negative electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which is applied to both surfaces of a negative electrode current collector 22A made of a copper foil having a thickness of 15 μm, and dried. The negative electrode active material layer 22B was formed by compression molding with a press. Thereafter, a negative electrode lead 25 made of nickel was attached to one end of the negative electrode current collector 22A.

  Subsequently, a separator 23 made of a microporous polypropylene film having a thickness of 25 μm was prepared, and a positive electrode 21, a separator 23, a negative electrode 22, and a separator 23 were laminated in this order to form a laminated body. The wound body 20 was produced by winding. The obtained wound body 20 was formed into a flat shape.

  After that, a thin strip plate made of stainless steel is prepared as the center plate 30, and an L-shaped cut 31 as shown in FIG. 5 is provided by wire cutting, and the center plate 30 is wound around the winding body 20. Inserted in the center.

After inserting the center plate 30, the wound body 20 was accommodated in the battery can 11. Subsequently, the insulating plate 12 is disposed on the wound body 20, the negative electrode lead 25 is welded to the battery can 11, and the positive electrode lead 24 is welded to the lower end of the positive electrode pin 15. The battery lid 13 was fixed by laser welding. After that, an electrolytic solution was injected into the battery can 11 from the electrolytic solution injection hole 19. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt at a content of 1 mol / dm ³ in a solvent obtained by mixing 50% by volume of ethylene carbonate and 50% by volume of diethyl carbonate was used. Finally, the electrolytic solution injection hole 19 was closed with a sealing member 19A to obtain a rectangular secondary battery having a thickness of 5 mm, a width of 34 mm, and a height of 42 mm.

  As Comparative Example 1 with respect to Example 1, a secondary battery was fabricated in the same manner as in Example 1 except that the center plate was not provided. As Comparative Example 2, a secondary battery was fabricated in the same manner as in Example 1 except that the center plate was not cut.

  Five secondary batteries (Battery 1 to Battery 5) of Example 1 and Comparative Examples 1 and 2 thus obtained were prepared, and a crushing test was performed to examine the presence or absence of ignition or rupture. The obtained results are shown in Table 1.

  As can be seen from Table 1, according to Example 1 in which a conductive center plate 30 having a bent cut 31 was provided at the winding center of the wound body 20, no rupture occurred at all. In Comparative Example 1 in which the center plate was not provided, and in Comparative Example 2 in which the notch was not provided in the center plate, rupture occurred in all of the five secondary batteries. That is, if the center plate 30 having the notch 31 is provided at the winding center of the wound body 20, safety can be improved even when a short circuit occurs due to the battery being crushed or broken. I understood that I could do it.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where an electrolytic solution that is a liquid electrolyte is used as a solvent has been described. However, another electrolyte may be used instead of the electrolytic solution. Other electrolytes include, for example, a gel electrolyte in which an electrolyte is held in a polymer compound, a solid electrolyte having ionic conductivity, a mixture of a solid electrolyte and an electrolyte, or a solid electrolyte and a gel electrolyte. And a mixture thereof.

  Note that various polymer compounds can be used for the gel electrolyte as long as it absorbs the electrolyte and gels. Examples of such a polymer compound include a fluorine-based polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, an ether-based polymer such as polyethylene oxide or a crosslinked product containing polyethylene oxide. A molecular compound, polyacrylonitrile, etc. are mentioned. In particular, a fluorine-based polymer compound is desirable from the viewpoint of redox stability.

  As the solid electrolyte, for example, an organic solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, or an inorganic solid electrolyte made of ion conductive glass or ionic crystals can be used. At this time, as the polymer compound, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, an acrylate polymer compound alone or mixed, Alternatively, it can be used by copolymerizing in the molecule. As the inorganic solid electrolyte, lithium nitride, lithium iodide, or the like can be used.

  Furthermore, the present invention can be applied to a primary battery.

  In addition, in the above embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or The present invention can also be applied to the case of using elements of Group 2 in the long-period periodic table such as magnesium or calcium (Ca), other light metals such as aluminum, lithium, or alloys thereof. An effect can be obtained. At that time, a negative electrode active material, a positive electrode active material, a solvent, or the like that can occlude and release the electrode reactant is selected according to the electrode reactant.

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st Embodiment of this invention. It is sectional drawing along the II-II line of FIG. It is sectional drawing showing the structure before winding of the positive electrode shown in FIG. It is sectional drawing showing the structure before winding of the negative electrode shown in FIG. It is a top view showing an example of composition of a center board. It is a top view showing the other structural example of a center board. It is a top view showing the further another structural example of a center board. It is a top view showing the further another structural example of a center board. It is a top view showing the further another structural example of a center board. It is a top view showing the further another structural example of a center board. It is a top view showing the further another structural example of a center board. It is a top view showing the further another structural example of a center board. It is sectional drawing showing the further another structural example of a center board. It is a perspective view showing an example of the conventional center pin.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12 ... Insulation board, 13 ... Battery cover, 14 ... Terminal board, 15 ... Positive electrode pin, 16 ... Insulation case, 17 ... Gasket, 18 ... Cleavage valve, 19 ... Electrolyte injection hole, 19A ... Sealing 20, wound body, 21, positive electrode, 21 A, positive electrode current collector, 21 B, positive electrode active material layer, 21 C, positive electrode coating region, 21 D, positive electrode exposed region, 22, negative electrode, 22 A, negative electrode current collector, 22 B ... negative electrode active material layer, 22C ... negative electrode coating region, 22D ... negative electrode exposed region, 23 ... separator, 24 ... positive electrode lead, 25 ... negative electrode lead, 30 ... center plate, 31 ... notch, 32 ... side, 33 ... notch

Claims (5)

A rectangular parallelepiped battery can,
It has a laminated structure with a separator between a positive electrode having a positive electrode active material layer on the surface of the strip-shaped positive electrode current collector and a negative electrode having a negative electrode active material layer on the surface of the strip-shaped negative electrode current collector and is flat. A wound body having a shape and housed in the battery can;
A battery comprising: a center plate that is formed of a conductive material and has a bent cut, and is disposed at a winding center of the winding body. The positive electrode has a positive electrode exposed region in which the positive electrode active material layer does not exist on both sides at an end portion on the winding center side of the positive electrode current collector, and the negative electrode is on the winding center side of the negative electrode current collector The battery according to claim 1, further comprising: a negative electrode exposed region in which the negative electrode active material layer does not exist on both sides at the end of the battery.   2. The negative electrode according to claim 1, wherein the negative electrode is capable of inserting and extracting an electrode reactant, and includes a negative electrode active material containing at least one of a metal element and a metalloid element as a constituent element. battery.   The battery according to claim 3, wherein the negative electrode includes a material containing at least one of tin (Sn) and silicon (Si) as a constituent element as the negative electrode active material.   The negative electrode includes tin, cobalt (Co), and carbon (C) as constituent elements as the negative electrode active material, and the carbon content is 9.9 mass% or more and 29.7 mass% or less, 4. The battery according to claim 3, further comprising a CoSnC-containing material in which a ratio of cobalt to a total of tin and cobalt is 30% by mass or more and 70% by mass or less.

Images