JP2006134758A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery capable of improving charge/discharge cycle characteristics by preventing micro short circuit caused by a level difference or the like of an end part of an active material layer and a reed, in case an alloy material is used as an anode active material. <P>SOLUTION: Cathode exposed regions 21D are provided at an end part of outer peripheral side of the winding of a cathode 21. The cathode exposed region 21D has an insulating protective member 30 arranged on a winding laid just under the outermost winding of an anode active layer material 22B, at a position facing an end part 22B1 located at the outer peripheral side of the outermost winding. The protective member 30 may be provided either at an inner peripheral side or both outer and inner peripheral side. A width of the protective member 30 is preferred to be formed larger than that of a cathode collector 21A within the range of 0.54 mm or more and 5 mm or less. Further, an anode exposed region 22D is preferred to be extended up to an opposite position of one round inside the position where an anode reed 26 is connected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a secondary battery including a wound body obtained by laminating and winding a positive electrode and a negative electrode with an electrolyte interposed therebetween, and in particular, can absorb and release an electrode reactant, and constitutes a constituent element. The present invention relates to a secondary battery including a negative electrode including a negative electrode active material including at least one of a metal element and a metalloid element.

  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.

  As a negative electrode active material used for a lithium ion secondary battery, a carbon-based material such as non-graphitizable carbon or graphite having a relatively high capacity and good cycle characteristics is widely used. However, considering the recent demand for higher capacity, further increase in capacity of carbon-based materials has become an issue.

  From such a background, a technique for achieving a high capacity with a carbon-based material by selecting a carbonization raw material and preparation conditions has been developed (see, for example, Patent Document 1). However, when such a carbon-based material is used, the negative electrode discharge potential is 0.8 V to 1.0 V with respect to lithium, and the battery discharge voltage when the battery is configured becomes low. Then we cannot expect a big improvement. Furthermore, there is a drawback that the charge / discharge curve has a large hysteresis and the energy efficiency in each charge / discharge cycle is low.

On the other hand, as a high-capacity negative electrode that surpasses carbon-based materials, research is being conducted on an alloy material in which a certain kind of metallic lithium is electrochemically alloyed and reversibly generated and decomposed. For example, a high-capacity negative electrode using a Li—Al alloy has been developed, and further, a high-capacity negative electrode made of a Li—Si alloy has been developed (see, for example, Patent Document 2). An intermetallic compound called Cu ₆ Sn ₅ has also been developed (see, for example, Patent Document 3).
Di. D. Larcher, “Journal of The Electrochemical Society”, 2000, Vol. 147, p1658-1662 JP-A-8-315825 US Pat. No. 4,950,566, etc. JP-A-6-325765 JP-A-7-230800 JP 7-288130 A JP-A-5-234620 JP 2001-266946 A

However, Li—Al alloy, Si alloy, or Cu ₆ Sn ₅ expands and contracts with charge / discharge, and pulverizes every time charge / discharge is repeated. Therefore, there is a big problem that cycle characteristics are extremely poor.

Therefore, as a technique for improving the cycle characteristics, it has been studied to replace a part with an element that does not participate in expansion / contraction due to insertion / extraction of lithium. For example, LiSi _s O _t (0 ≦ s, 0 <t <2), Li _u Si _1-v M _v O _w (M represents a metal excluding an alkali metal or a similar metal excluding silicon, and 0 ≦ u, 0 <v <1, 0 <w <2), Or the LiAgTe type-alloy is proposed (for example, refer patent documents 4-6). However, even with these negative electrode active materials, the fact is that the charge / discharge cycle characteristics are greatly deteriorated due to expansion and contraction, and the characteristics of high capacity cannot be fully utilized.

  Moreover, when using these negative electrode active materials, a negative electrode expand | swells and shrinks greatly with charging / discharging. Therefore, in particular, when the positive electrode and the negative electrode are stacked and wound with the electrolyte in between, the end of the active material layer or the step of the lead on the outer periphery of the winding presses the separator due to the expansion of the negative electrode, and the other Contact with the electrode caused a short-circuit, which caused deterioration of charge / discharge cycle characteristics. Furthermore, fading of the edge of the active material layer and flying of the paint during formation also cause a step on the surface of the positive electrode or the negative electrode, which may similarly cause a micro short circuit and deteriorate the charge / discharge cycle characteristics. . Such a phenomenon was particularly remarkable at a high temperature and in a charge / discharge cycle of overcharge.

  Conventionally, in a wound type battery using a carbon-based material as a negative electrode active material, an insulating material such as a tape made of polyimide or polypropylene is bonded onto the end of the electrode and the electrode on the opposite side, It has been proposed to prevent a short circuit between electrodes when a pressing force is applied from the outside (see, for example, Patent Document 7).

  The present invention has been made in view of such problems, and its purpose is to prevent a micro short circuit caused by an end portion of an active material layer or a step of a lead when an alloy material is used as a negative electrode active material, It is providing the secondary battery which can improve charging / discharging cycling characteristics.

  The secondary battery according to the present invention comprises a belt-like positive electrode current collector having a positive electrode active material layer and a belt-like negative electrode current collector laminated with a negative electrode having a negative electrode active material layer, with a separator in between. The negative electrode is capable of occluding and releasing 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 positive electrode current collector has an exposed positive electrode exposed region that is exposed without being covered with the positive electrode active material layer at the end portion on the outer periphery side of the winding, and the positive electrode exposed region is one of the end portions on the outer peripheral side of the negative electrode active material layer An insulating protective member is provided on at least one of the outer peripheral side and the inner peripheral side at the opposing position on the inner side.

  According to the secondary battery of the present invention, the negative electrode can absorb and release the electrode reactant, and includes a negative electrode active material including at least one of a metal element and a metalloid element as a constituent element. Therefore, a high capacity can be obtained. Further, the positive electrode has a positive electrode exposed region at an end portion on the outer periphery side of the winding, and this positive electrode exposed region is located on the outer peripheral side and the inner side at the opposite positions on the inner side of the outer periphery side of the negative electrode active material layer. Since an insulating protective member is provided on at least one of the peripheral sides, the protective member provided on the outer peripheral side allows the step between the step on the winding outer peripheral side of the negative electrode active material layer and the positive electrode exposed region. A micro short-circuit can be prevented, and even when a micro short-circuit occurs, the generated heat can be released to the winding outer peripheral side by the protective member provided on the inner peripheral side. Therefore, cycle characteristics and safety can be improved while maintaining a high capacity.

  In addition, the negative electrode has a negative electrode exposed region to which the negative electrode lead is connected at the end on the winding outer periphery side, and the negative electrode exposed region extends to an opposing position on the inner side of the circumference of the position where the negative electrode lead is connected. In this case, the negative electrode lead and the positive electrode exposed region are in contact with each other even when the negative electrode expands with charge / discharge and the negative electrode exposed region or the separator is broken at the corner of the negative electrode lead. Therefore, a minute short circuit can be prevented.

  Furthermore, if the width of the protective member is larger than the positive electrode current collector in the range of 0.5 mm or more and 5 mm or less, even if the width of the positive electrode is extended by charging / discharging, the end in the width direction of the positive electrode is increased. It can be covered with a protective member to suppress a minute short circuit with the negative electrode. Therefore, cycle characteristics can be further improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawing, 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.

(First embodiment)
FIG. 1 shows a cross-sectional structure of a secondary battery according to the first embodiment of the present invention. This secondary battery is a so-called cylindrical type, and has a wound body 20 inside a substantially hollow cylindrical battery can 11. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the wound body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 and a thermal resistance element (Positive Temperature Coefficient; PTC element) 16 provided inside the battery lid 14, have a gasket 17 in between. The battery can 11 is attached by being caulked, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound body 20 is formed by laminating a positive electrode 21 and a negative electrode 22 with a separator 23 interposed therebetween and wound in a spiral shape, and a center pin 24 is inserted in the center. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the wound body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows a cross-sectional configuration of the positive electrode 21 shown in FIG. 1 before winding. The positive electrode 21 is obtained, for example, 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 outer periphery 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 and 0.05 ≦ y ≦ 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. 3 shows a cross-sectional configuration of the negative electrode 22 shown in FIG. 1 before winding. The negative electrode 22 is obtained, for example, 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 end portion on the winding outer peripheral side Both have a negative electrode exposed region 22D that is exposed without the negative electrode active material layer 22B. A negative electrode lead 26 is connected to the negative electrode exposed region 22D.

  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 can contain and release lithium as an electrode reactant as a negative electrode active material, and contains a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element is doing. This is because a high energy density can be obtained by using such a negative electrode material. This 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. Moreover, this negative electrode material may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  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 carbon 1s orbital (C1s) appears at 284.5 eV in an energy calibrated apparatus so that the peak of 4f orbit of gold atom (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 for correcting 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, and this 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).

  The negative electrode active material layer 22B may further include other negative electrode active materials, and may include other materials that do not contribute to charging, such as a conductive agent, a binder, or a viscosity modifier. Examples of other negative electrode active materials include carbon materials such as natural graphite, artificial graphite, non-graphitizable carbon, and graphitizable carbon. Examples of the conductive agent include graphite fiber, metal fiber, and metal powder. Examples of the binder include a fluorine-based polymer compound such as polyvinylidene fluoride, or a synthetic rubber such as styrene butadiene rubber or ethylene propylene diene rubber. Examples of the viscosity modifier include carboxymethylcellulose.

  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.

  FIG. 4 illustrates an example of a cross-sectional configuration along line IV-IV of the wound body 20 illustrated in FIG. In FIG. 4, the separator 23 is omitted. The positive electrode exposed region 21D has an insulating protective member 30 on the outer peripheral side at the opposite position on the inner side of one end of the end portion 22B1 on the winding outer peripheral side of the negative electrode active material layer 22B. Thereby, in this secondary battery, it is possible to prevent a minute short circuit between the step of the end 22B1 on the winding outer periphery side of the negative electrode active material layer 22B and the positive electrode exposed region 21D, and to improve the cycle characteristics. It has become.

  The width of the protective member 30 is preferably larger than that of the positive electrode current collector 21A in the range of 0.5 mm to 5 mm. This is because even in the case where the width of the positive electrode 21 is extended due to charging / discharging, the end in the width direction that is likely to come into contact with the negative electrode 22 can be protected and minute short circuit can be suppressed.

  As such a protective member 30, what is necessary is just what can exist stably in the surface of the positive electrode 21, for example, the adhesive tape which consists of a polypropylene or a polyethylene terephthalate is mentioned.

  Further, as described above, the negative electrode lead 26 is connected to the outermost periphery of the negative electrode exposed region 22D. Furthermore, as shown in FIG. 5, the negative electrode exposed region 22 </ b> D extends to a facing position on the inner side of one circumference of the position where the negative electrode lead 26 is connected. By doing so, the negative electrode lead 26 and the positive electrode are exposed even when the negative electrode 22 expands with charge / discharge and the negative electrode exposed region 22D and the separator 23 are broken at the corners of the negative electrode lead 26. There is no contact with the region 21D, and a minute short circuit can be prevented. In FIG. 5, the separator 23 is indicated by a wavy line.

  This secondary battery can be manufactured, for example, 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 compression-molded by a roll-press machine or the like. To form the positive electrode 21. At that time, the positive electrode exposed region 21D is formed at the end on the winding outer peripheral side.

  Further, as shown in FIG. 4, the positive electrode exposed region 21 </ b> D is made of the above-described material as the protective member 30 on the outer peripheral side at the opposite position on the inner side of the outer periphery of the negative electrode active material layer 22 </ b> B. Adhesive tape is provided. At this time, it is preferable that the width of the protective member 30 is larger than that of the positive electrode current collector 21 </ b> A within a range of 0.5 mm to 5 mm. The length of the protective member 30 is determined so that the protective member 30 faces the end portion 22B1 on the winding outer peripheral side of the negative electrode active material layer 22B in consideration of winding deviation when the wound body 20 is formed. It is desirable.

  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 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 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, and wound many times in the winding direction shown in FIGS. 2 and 3 to produce the wound body 20.

  After the wound body 20 is manufactured, the wound body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The body 20 is accommodated in the battery can 11, and the electrolyte is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking the gasket 17 therebetween. Thereby, the secondary battery shown in FIG. 1 is completed.

  In this secondary battery, when charged, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. When discharging is performed, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution impregnated in the separator 23. Here, in the positive electrode exposed region 21D, the insulating protective member 30 is provided on the outer peripheral side at the opposite position on the inner circumference of the end portion 22B1 on the winding outer peripheral side of the negative electrode active material layer 22B. The step of the end 22B1 on the winding outer periphery side of the material layer 22B does not press the separator 23 due to the expansion of the negative electrode 22 and directly contact the positive electrode exposed region 21D. Therefore, a short circuit is prevented and cycle characteristics are improved.

  As described above, according to the present embodiment, the negative electrode 22 can occlude and release the electrode reactant, and the negative electrode active material containing at least one of a metal element and a metalloid element as a constituent element. Since it was made to include, a high capacity can be obtained. Further, the insulating protective member 30 can prevent a minute short circuit between the step at the end 22B1 on the winding outer periphery side of the negative electrode active material layer 22B and the positive electrode exposed region 21D. Therefore, cycle characteristics can be improved while maintaining a high capacity.

  Further, the negative electrode 22 has a negative electrode exposed region 22D to which the negative electrode lead 26 is connected at the end on the winding outer peripheral side, and the negative electrode exposed region 22D is opposed to the inside of the circumference of the position where the negative electrode lead 26 is connected. If the negative electrode 22 expands to the position, the negative electrode 22 expands with charge and discharge, and the negative electrode exposed region 22D and the separator 23 are broken through the corners of the negative electrode lead 26. The lead 26 and the positive electrode exposed region 21D do not come into contact with each other, and a minute short circuit can be prevented.

  Furthermore, if the width of the protective member 30 is made larger than the positive electrode current collector 21A in the range of 0.5 mm or more and 5 mm or less, the width of the positive electrode 21 can be increased even when the width of the positive electrode 21 is extended by charge / discharge. The direction end can be covered with the protective member 30 to suppress a minute short circuit with the negative electrode 22. Therefore, cycle characteristics can be further improved.

(Second Embodiment)
FIG. 6 shows a cross-sectional configuration of the wound body 20 according to the second embodiment of the present invention. In the wound body 20, the positive electrode exposed region 21 </ b> D has an insulating protective member 30 on the inner peripheral side at the opposite position on the inner circumference of the end 22 </ b> B <b> 1 on the outer peripheral side of the negative electrode active material layer 22 </ b> B. Except for this, the other components have the same configuration as that of the first embodiment, and can be manufactured in the same manner. Therefore, the same components as those in the first embodiment will be described with the same reference numerals. In FIG. 5, the separator 23 is omitted.

  In the present embodiment, as described above, the positive electrode exposed region 21D is disposed on the inner peripheral side of the end portion 22B1 on the inner peripheral side of the winding outer peripheral side of the negative electrode active material layer 22B on the inner peripheral side, and the insulating protective member 30 have. Thereby, in this secondary battery, when a micro short circuit occurs between the step of the winding outer peripheral side end 22B1 of the negative electrode active material layer 22B and the positive electrode exposed region 21D, the generated heat is generated by the protective member 30. It is intercepted and is not transmitted to the winding center side, but is discharged to the winding outer peripheral side. Therefore, excessive temperature rise can be prevented and safety can be enhanced.

(Third embodiment)
FIG. 7 shows a cross-sectional configuration of a wound body 20 according to the third embodiment of the present invention. In the wound body 20, the insulating protection member 30 is provided on the outer peripheral side and the inner peripheral side in the opposite position on the inner side of the end portion 22B1 on the winding outer peripheral side of the negative electrode active material layer 22B. Except for this, the rest has the same configuration as that of the first embodiment, and can be manufactured in the same manner. Therefore, the same components as those in the first embodiment will be described with the same reference numerals. In FIG. 6, the separator 23 is omitted.

  In the present embodiment, as described above, the positive electrode exposed region 21D has an insulating property on the outer peripheral side and the inner peripheral side at the opposing position on the inner circumference of the end portion 22B1 on the winding outer peripheral side of the negative electrode active material layer 22B. A protective member 30 is provided. Thereby, in this secondary battery, it is possible to prevent a micro short circuit between the step of the winding outer peripheral end 22B1 of the negative electrode active material layer 22B and the positive electrode exposed region 21D. However, the generated heat can be released to the outer circumferential side of the winding to improve safety.

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

(Examples 1-1 to 1-4)
The secondary battery described in the first 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, the 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. At that time, the positive electrode exposed region 21 </ b> D was provided at the end of the positive electrode 21 on the winding outer peripheral side.

  After the positive electrode 21 is formed, a polypropylene adhesive tape having a length of 15 mm as a protective member 30 is formed on the outer peripheral side of the positive electrode exposed region 21D on the outer peripheral side at the opposite inner side of the winding outer peripheral end of the negative electrode active material layer 22B. Pasted. At this time, the width of the protective member 30 is 5 mm larger than the positive electrode current collector 21A in Example 1-1 (2.5 mm larger on one side in the width direction, and 4 mm (2 mm on one side in the width direction) in Example 1-2). In Example 1-3, the electrode was formed larger than the positive electrode current collector 21A by 1 mm (0.5 mm on one side in the width direction), and in Example 1-4, the size was the same as the positive electrode current collector 21A. An aluminum positive electrode lead 25 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, and the negative electrode 22 was produced. At that time, a negative electrode exposed region 22D was provided at the end of the negative electrode 22 on the winding outer periphery side, and a negative electrode lead 26 made of nickel was attached to the negative electrode exposed region 22D. At this time, the negative electrode exposed region 22 </ b> D was extended to a facing position on the inner side of one circumference of the position where the negative electrode lead 26 was connected.

  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 maximum diameter of the body of the wound body 20 was 13 mm.

After the wound body 20 is manufactured, the wound body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The body 20 was accommodated in a battery can 11 having an inner diameter of 13.4 mm. After that, an electrolytic solution was injected into the battery can 11. 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.

  After injecting the electrolyte into the battery can 11, the battery lid 14 was caulked to the battery can 11 with the gasket 17 in between, thereby obtaining a cylindrical secondary battery having an outer diameter of 14 mm and a height of 43 mm.

(Examples 2-1 to 2-4)
The secondary battery described in the second embodiment was manufactured. Example 1 except that a polypropylene adhesive tape was applied as a protective member 30 to the inner peripheral side of the positive electrode exposed region 21D on the inner peripheral side of the end of the negative electrode active material layer 22B on the outer peripheral side of the winding. Secondary batteries were fabricated in the same manner as -1 to 1-4. At that time, the width of the protective member 30 is 5 mm larger than the positive electrode current collector 21A in Example 2-1 (2.5 mm larger on one side in the width direction, and 4 mm in Example 2-2 (2 mm on one side in the width direction). In Example 2-3, the electrode was formed larger by 1 mm (0.5 mm on one side in the width direction) than in the positive electrode current collector 21A, and in Example 2-4, it was the same as the positive electrode current collector 21A.

(Examples 3-1 to 3-4)
The secondary battery described in the third embodiment was manufactured. Except that a polypropylene adhesive tape was applied as a protective member 30 to the positive electrode exposed region 21D on the outer peripheral side and the inner peripheral side in the opposite position on the inner circumference of the winding outer peripheral end of the negative electrode active material layer 22B, Secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-4. At that time, the width of the protective member 30 is 5 mm larger than the positive electrode current collector 21A in Example 3-1 (2.5 mm larger on one side in the width direction, and 4 mm in Example 3-2 (2 mm on one side in the width direction). In Example 3-3, the electrode was formed larger by 1 mm (0.5 mm on one side in the width direction) than in the positive electrode current collector 21A, and in Example 3-4, the electrode was made the same as the positive electrode current collector 21A.

  As a comparative example for Examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4, as shown in FIG. 8, no protective member was used, and positive electrode exposed region 21D. In the same manner as in Examples 1-1 to 1-4 except that it was extended to the opposite position on the inner circumference of the position where the negative electrode lead 126 of the negative electrode exposed region 122D was connected. Produced. In FIG. 8, the same components as those shown in FIGS. 1 to 7 are denoted by the same reference numerals in the 100s.

  Five secondary batteries of Examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4 and comparative examples obtained in this way were prepared, and the cycle characteristics were examined. It was. The obtained results are shown in Table 1. In Table 1, the width difference between the protective member and the positive electrode current collector is a value obtained by subtracting the width of the positive electrode current collector from the width of the protective member ((width of the protective member) − (width of the positive electrode current collector)). "+" Represents that the width of the protective member is larger than the width of the positive electrode current collector.

  As the cycle characteristics, the discharge capacity retention ratio at the 200th cycle (discharge capacity at the 200th cycle / discharge capacity at the second cycle) × 100 (%) with respect to the discharge capacity at the second cycle was determined. At that time, charge / discharge is performed under constant current / constant voltage charging under the condition of upper limit voltage 4.2V and current 1C in an environment of 45 ° C. and then constant current discharge under conditions of current 1C and final voltage 2.5V. Went. 1C is a current value at which the battery capacity can be discharged in one hour.

  As can be seen from Table 1, Examples 1-1 to 1-4, in which the protective member 30 is provided and the negative electrode exposed region 22D is extended to the opposite position on the inner side of the circumference of the position where the negative electrode lead 26 is connected, are shown. In 2-1 to 2-4 and 3-1 to 3-4, the protective member is not provided, and the positive electrode exposed region 121D is moved to the opposite position on the inner circumference of the position where the negative electrode lead 126 of the negative electrode exposed region 122D is connected. The capacity retention rate was improved as compared with the extended comparative example.

  Further, in Examples 1-1 to 1-3 in which the width of the protective member 30 is 5 mm, 4 mm, or 1 mm larger than the positive electrode current collector 21A, a stable high capacity maintenance rate of 80% or more is obtained. It improved compared with Example 1-4 which made the width | variety of the protection member 30 the same as 21 A of positive electrode electrical power collectors. Similar results were obtained in Examples 2-1 to 2-4 and Examples 3-1 to 3-4.

  That is, in the positive electrode exposed region 21D, the protective member 30 is provided on at least one of the outer peripheral side and the inner peripheral side at the opposite position on the inner periphery side of the end portion on the winding outer peripheral side of the negative electrode active material layer 22B. It has been found that the cycle characteristics can be improved by extending 22D to an opposing position on the inside of one circumference of the position where the negative electrode lead 26 is connected.

  It has also been found that cycle characteristics can be improved if the width of the protective member 30 is made larger than the positive electrode current collector 21A in the range of 0.5 mm to 5 mm.

  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.

  Moreover, in the said embodiment and Example, although the cylindrical secondary battery which has a winding structure was demonstrated, all can be applied if this invention is a secondary battery which has a winding structure.

  Furthermore, in the above-described embodiment 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 magnesium Alternatively, the present invention can be applied to the case where a Group 2 element in a long-period periodic table such as calcium (Ca), another light metal such as aluminum, lithium, or an alloy thereof is used, and similar effects are obtained. 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 one embodiment of this invention. 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 sectional drawing showing the structure along the IV-IV line of the wound body shown in FIG. It is sectional drawing which expands and represents a part of winding body shown in FIG. It is sectional drawing showing the structure of the wound body which concerns on the 2nd Embodiment of this invention. It is sectional drawing showing the structure of the wound body which concerns on the 3rd Embodiment of this invention. It is sectional drawing showing the structure of the wound body which concerns on the comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulating plate, 14 ... Battery cover, 15 ... Safety valve mechanism, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20 ... Winding body, 21 ... Positive electrode, 21A ... Positive electrode collector, 21B ... Positive electrode active material layer, 21C ... Positive electrode coating region, 21D ... Positive electrode exposure region, 22 ... Negative electrode, 22A ... Negative electrode current collector, 22B ... Negative electrode active material layer, 22C ... Negative electrode coating region, 22D ... Negative electrode exposure region, 23 ... separator, 24 ... center pin, 25 ... positive electrode lead, 26 ... negative electrode lead, 30 ... protective member.

Claims (6)

A positive electrode having a positive electrode active material layer on a belt-like positive electrode current collector and a negative electrode having a negative electrode active material layer on a belt-like negative electrode current collector are laminated with a separator interposed therebetween, and a wound body is provided.
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,
The positive electrode has a positive electrode exposed region at an end portion on a winding outer peripheral side where the positive electrode current collector is exposed without being covered with the positive electrode active material layer,
The positive electrode exposed region has an insulating protective member on at least one of an outer peripheral side and an inner peripheral side at a facing position inside one circumference of an end of the negative electrode active material layer on the outer circumferential side. Secondary battery. The negative electrode has a negative electrode exposed region in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer, and a negative electrode lead is connected to an end portion on a winding outer peripheral side,
2. The secondary battery according to claim 1, wherein the negative electrode exposed region extends to a facing position on one inner side of a position where the negative electrode lead is connected.   The secondary battery according to claim 1, wherein the protective member is made of polypropylene or polyethylene terephthalate. The secondary battery according to claim 1, wherein the protective member has a width larger than that of the positive electrode current collector in a range of 0.5 mm to 5 mm.   The secondary battery according to claim 1, 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, 2. The secondary battery according to claim 1, 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.

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